• BASSBOSS - David Lee
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Subwoofer arrangment/placement
Hi Aaron,

There are so many factors to consider beyond those in the article. The article describes the problem and offers a solution in terms of mixing bass-heavy if your mix position is on the center line but doesn’t discuss any alternatives to the setup.

Without going deeply into the simulations and graphics I will describe a few related issues and some potential solutions that you could actually use.

Initially let’s consider an outdoor scenario, or at least lets ignore the reflections that occur indoors that would complicate the following discussion.

First, there is Proximity. Having the subs in the proximity of the tops allows their outputs to be aligned and summed in phase. This helps with “punch" and "impact”. If you stack subs in the center, you get the benefit of more even coverage of bass but you lose the benefit of that bass being phase-coherent with the tops over a relatively large coverage area. In big systems, when the tops are flown well above the subs, this alignment issue is a problem even when the subs are left and right because they will also be misaligned to a certain extent from front-to-back due to the height offset. Generally with these bigger systems there is enough equipment and therefor enough sources that the gaps get filled in well enough for the audience to get acceptable results in most locations.  

In smaller systems it can be worse because the tops aren’t able to deliver a sufficient portion of the low frequency energy to make the sides sound full when the subs are stacked at a center location. The center-stacking advantage of having even coverage of the bass, without the lobes associated with a left-right placement, is offset by the potential imbalance in the perceived level of bass. With the subs in the center and the tops left and right, the perception can be too much bass in the middle and too little bass on the sides.

The 'best' solution is to have at least 3 subwoofer sources. One left, one right and one center. Instead of having one power alley, and several valleys, you will create 3 power alleys. One in the center, between the left and right, one between left and center and one between right and center. Having three sources creates a situation where you’re almost never in a location where an absolute null can occur. It puts full-range, high-impact sound on the outer edges so the overall balance is better to the left and right. It puts power alleys where there used to be valleys. It also puts a bit of extra whomp right in front of the stage where the fervent fans tend to gather.

Now let’s consider the difference between indoor and outdoor. Outdoors you’re less likely to have surfaces that reflect sound surrounding your system. There’s the ground, but not much else. And if your subs are on the ground, the reflections are not generally destructive. Indoors, the reflections of low frequency sound contribute to the comb-filtering effect. Comb-filtering refers to destructive interference caused by an offset of arrival times. Reflected sound arrives later than direct sound and it, too, can be constructive or destructive. The difference in distance from the source to the listener versus the source to the reflecting surface and back to the listener will determine the frequencies that are reinforced or cancelled. The side walls, the back wall behind the stage or speakers, the far wall and the ceiling will all reflect sound. For the most part, reflected sound indoors will be perceived as an increase in the level of higher frequencies due to their shorter wavelengths. On the other hand, due to the longer wavelengths of low frequencies, the reflected low-frequency sound can create large areas with a perceived absence of bass. Due to these reflection-induced nulls, subwoofer placement indoors is less forgiving than outdoors.

For instance, if a subwoofer is placed with its back to a wall, there will be a reflection as the sound leaves the front of the box, wraps around the box and then reflects off the wall. If the same subwoofer is placed with its side to the wall, there is effectively no difference in distance between the source and the reflection, making for a smoother response in the room and a slightly higher level to boot.

 
Sideofwall.jpg 
 
When you have a null, no amount of level at the source can overcome it. The remaining SPL will always be the same. +1-1=0, +10-10=0, +100-100=0  The only solution is to change the relationship of the direct sound to the reflecting surface. In other words, to move the source,- because that’s usually easier than moving the walls and ceiling. A hard-reflecting, solid surface is effectively a secondary sound source presenting the listener with an inverted, delayed, attenuated signal. The delay is the path length difference from direct to reflected sound. The attenuation is the energy loss over the additional distance and the inversion is the result of the reflection. This problem is potentially worse for people with OCD because if you put everything at the same distances from walls and each other, all the positives and all the negatives add up the same. If you offset things slightly you can have one side null at different frequencies from the other, with the result being some less complete nulls and a more even average level. Hopefully that offers you something to try…

On carts is generally not as good as off carts - unless you’re doing the lifting at the end of the night. On a concrete or dirt floor, off the carts will result in a slight, very slight, difference in SPL and impact. The reason is that if the subs can’t move back when the cones move forward, more of the energy is transmitted into the air. You can strap multiple subs together with ratchet straps to link their total mass to improve performance. This helps whether they are on carts or not.

Other than minimizing heavy lifting, there are circumstances where on a cart is better, such as if you want the carts to isolate the subs from the surface they’re on, like a resonant floor or stage. A resonant floor or stage can make the subs sound muddy by contributing its own tonality to the overall sound. For instance, putting the subs on carts with the wheels unlocked and rotated front-rear will allow the boxes to absorb the cone inertia without transmitting as much energy into the floor.

I would tend to avoid putting subs on any stage that has mics on it unless that stage is poured concrete or packed dirt, and even then I would hesitate. The only reason I can think of for putting subs on a stage, with no mics, is in a room with a ceiling reflection that’s killing your low end energy. This would tend to be a very low, very rigid ceiling, usually less than 12 feet, such as in a basement. If you elevate subs in a room like that, you will probably get better summed response between the floor and ceiling, where the ears are.

This brings to mind the advantages of cardioid deployments. Outdoors, cardioid can keep bass levels down on stage and even keep LF energy from interfering with other performances or even adjacent neighborhoods. Indoors, cardioid deployments can improve frequency response in the audience area by minimizing wrap-around reflections that would otherwise cause destructive interference as they bounced off the back wall and then all around the venue.

In conclusion, I would recommend adding one subwoofer for center placement to a 2 subs and 2 tops setup to help even out bass response in most circumstances. Pay close attention to reflection surfaces and try to use them to your advantage if possible. And consider that a certain amount of asymmetry can work in your favor.

Let me know if there are any other questions I can answer. Thanks!

Best,
David Lee
BASSBOSS
Bassboss LA88 vs. QSC KLA12
My pleasure. Products that aren't true line arrays being marketed as such is a pet peeve of mine, so I enjoyed the chance to highlight the differences. ;-)

Thanks for your question!
best
David Lee
Bassboss LA88 vs. QSC KLA12

Dear Jay,

Thanks for your interest in the BASSBOSS LA88 Line Array. Below is a short comparison between it and the QSC KLA12.

For more information on line array technology, and what constitutes a TRUE line array, I recommend reading this article from the ProSoundWeb about line array design and function.

prosoundweb.com/topics/sound_reinforcement/everything_you_wanted_to_know_about_line_arrays

The LA88 is a line array featuring 120 degree horizontal by 8 degree vertical coverage and splay increments from 0 to 8 degrees.

The KLA12 is a 2-way loudspeaker with a fixed 18 degree vertical coverage pattern. In other words, it’s not a line array.

The standard LA88s can be flown 12 deep with virtually infinite adjustability of the coverage of the array, allowing the energy to focused on the far field or to be spread over 80 degrees. With 5 boxes, the maximum vertical spread would be ~45 degrees.

The KLA can be flown a maximum of 5 deep with a minimum vertical coverage of 90 degrees on 5 boxes. The energy can’t be focused for long-throw applications. It’s not a line array.

The LA88 uses two HF compression drivers, each with a 1.7” voice coil and each on a 1” throat isophasic wave guide. Both cover a cabinet frontal height of 10”, making each cover only 5” of vertical line output. This tighter directivity and higher output density makes it suitable for long-throw applications.

The KLA12 has one compression driver with a 1.75” voice coil, stretched to cover a cabinet frontal height of 15”. The reduced driver displacement (1 vs 2) and lower directivity index mean this box will not project sound as effectively.

The LA88 is symmetrical, with the same coverage provided to the left and right of the array.

The KLA12 is asymmetrical, so the sound arriving at the center between the two arrays from one side is different from the other.

The LA88 uses 8” drivers with a proprietary energy distribution system to ensure line-array propagation performance in the midrange frequencies. Spacing between the effective acoustical centers is reduced to 1.25”. That's the wavelength of 10,800Hz, resulting in mid-range propagation summing to 3600Hz, which is 1600Hz above the mid-range to high crossover frequency. This ensures consistent summing and even propagation throughout the frequency range.

The KLA12 uses a single 12” woofer with no mechanism for improved mid-range coupling and propagation. Spacing between the effective acoustical centers is over 15”. That’s the wavelength of 900Hz, resulting in mid-range propagation summing to only 300Hz. QSC doesn’t disclose the crossover frequency but it’s likely to be above 1500Hz considering the 1.75” HF voice coil. The result is a huge gap in mid-range propagation effectiveness between 300 and ~1500Hz. Again, this is not a line array.

The LA88 is made in the USA from Baltic Birch for structural integrity and sound quality and uses Neodymium drivers which keep its weight down to 55 lbs each.

The KLA12 is made in China from more flexible ABS plastic and the ceramic magnet drivers increase its weight to the same 55 lbs each.

The LA88 is powered by a 3000W Powersoft amplifier.

The KLA12 is powered by a 1000W QSC amplifier.

In short, the LA88 Line Array is a very lightweight, extremely powerful, wide dispersion, tightly controlled line array capable of projecting sound over long distances.

The KLA12 "Line Array" is a 2-way plastic box with an 18 degree coverage high frequency horn that can be stacked in 18 degree vertical increments. As it's not a line array it offers essentially none of the benefits of line array technology. In practice it’s effectively a point-source array rotated onto its side. The component cost is probably only slightly more than the K12 but tagging it as a “line array” apparently gives them license to charge $1,000.00 more. Did I mention it wasn’t a line array?  ;-)

If there are any other questions I can answer, please let me know.

best,
David Lee
Questions About Amplification and Specifications
Hey Zach,

No bother, I'm sure your questions, and the answers, will help plenty of people!  One way to think about the numbers of watts is to consider that when discussing amplifiers, including the amplifiers in powered speakers, the number of Watts refers to the output of the AMPLIFIER, not to the output of the speaker. How much sound comes out of the speaker is not dependent on the number of Watts alone. My answers are in bold.

1) So just to clarify it is extremely possible, specifically talking about subwoofers, when frequency spectrum and quality are similar between two products, it's possible that a 700w sub can have a dB output that's louder or just as loud with the same quality as a 2400w sub? If so, would that be shown on paper as the Max peak SPL? (Main point I'm getting at is if I run into a decision between buying a 700w speaker with 128dB @ 1m, and a 2400w speaker with 128dB @ 1m, the best decision would be go with the 700w speaker, or are there other factors that would make one better than the other?)

There is always a trade-off of one kind or another. If there were two subwoofers that actually had identical frequency response characteristics and output characteristics and one of them achieved the performance with 700W and the other with 2400W it would be almost inevitable that the one using only 700W to achieve the output would be much larger. On the other hand, if the two were the same size and the only available comparison was the CLAIM of 128dB, it's not likely that they would both make good on their claim.

Something is likely to turn out to be an exaggeration. 128dB from 700W? At what frequency? I'd be more inclined to believe the 128dB from 2400W from a subwoofer. At that point you would need to dig deeper into the specifications to find data that supported the claims. Is the 2400W referred to as "peak" power? Probably a red flag. Is the 700W referred to as RMS power? Probably more realistic if the two share a similar price. 700W RMS is often then called 1400W "program" and some companies might even stretch that to 2400W "peak". Look for the *asterisks*.

That's where you find the fine print about how they got to those numbers.  If both speakers can actually deliver 128dB and the specification of the amplifier is exaggerated in one case then you can start to see which company is more or less likely to be telling the truth in other areas. The question is, can they actually deliver the 128dB?

The next place to look is at the 128dB specification. Does it specify whether that is a measured output or a calculated output? Is there a sensitivity specification? Does the sensitivity specification indicate the load impedance? If it does, you can calculate how much power would be required to reach the 128dB from the rated sensitivity.

To achieve a calculated output of 128dB using 700W would require a sensitivity of 100dB at 1 meter with one watt. That's not impossible for a horn-loaded system or a double-18" subwoofer but very unlikely for a direct radiating single 18" subwoofer. To achieve a calculated output of 128dB using 2400W would require a sensitivity of 94.5dB, which is realistic for a single 18" subwoofer.

Measured output takes more factors into account. The factors that occur in the real world, such as heat, turbulence and friction. In order to achieve a measured output of 128dB with 2400W, the sensitivity of the loudspeaker would have to be closer to 96 or 97.5 dB at one meter with one watt, depending on how well the driver dissipates heat.

This result requires a better quality driver and an amplifier that actually delivers every bit of the 2400W... And the speaker has to survive the testing. I see plenty of specifications that would almost certainly prove fatal to the speaker if anyone tried to achieve them in the real world.

So which one would I buy? I would be inclined to believe that a single driver sub with a 2400W amp could produce 128dB. IF the amps are rated using the same method and  the SPL and frequency responses were measured and specified exactly the same way, and they were the same price, etc., the 700W product would appear to be a superior design. On the other hand, if the 700W product is claiming 128dB peak and the 2400W product is claiming 128dB continuous, I would choose the 2400W product.

2) You mentioned "One could build a ruthlessly efficient system that was 112dB at 1 watt but did nothing at 30Hz. One could also build a desperately inefficient system that had 60,000W of power that would move more air with the fans in the amps than with the speakers."

Similar question to question #1, are you saying that the efficiency (output dB @ 1 m) and effectiveness (amount of Watts it takes to expend that dB at 1 m) is what a consumer should look at when figuring out what system to buy (assuming main goal is loudness and clarity).

Efficiency in this case refers to the conversion efficiency from electrical watts to acoustical watts.

Yes and no... I'm saying that you can't just look at electrical Watts and ignore the acoustical output that results from those watts. First let me clarify. Efficiency isn't just output dB @ 1 meter.  It's necessary to include three factors, Sound Pressure Level (dB) Distance (1m) and input power (1W) The specification of XdB (SPL) measured at 1 meter with 1 Watt of input power, usually but not always 2.83V into 8 ohms ( aka 95dB 1W1M) This specification indicates the system "Sensitivity", from which we can calculate the system's conversion efficiency as a ratio or percent. i.e. 95dB @1w1m corresponds to a 2% conversion efficiency. While this is very surprising, why is it important, you may ask? Because if your electrical to acoustical conversion efficiency is 2%, the other 98% of the electrical energy (aka Watts) is converted to heat! And heat is what blows woofers.

The higher your conversion efficiency, the less power your amplifier needs to deliver, the less heat you have to dissipate from the voice coil and the less current you need from the wall outlet. And a speaker with very low conversion efficiency will get a lot hotter when producing the same SPL as a speaker with a higher conversion efficiency, so there is a tendency for lower conversion efficiency speakers to burn/blow more easily if the demand is for high SPL.

From a sound quality, clarity or product purchasing point of view, it isn't absolutely better or worse to have a high or low conversion efficiency on its own. It's something you have to consider in context. For instance, a standard 120V 20A outlet can supply a maximum of 2400W continuously. If a speaker "A" can produce 128dB with 2400W and speaker "B" can produce 133dB with 2400W, then you might want to consider speaker "B" if you need to double your output without requiring another circuit. On the other hand, if speaker "B" is too big to move, you're going to need another circuit.

Amplifiers also have conversion efficiency specifications. If amplifier A produces 2000W and is 95% efficient it will require 2,100W to make the output. If amplifier B produces 2000W and is only 70% efficient, it will require 2850W to make 2000W of output. You can see where this may also be a factor to consider. But this is a conversation for another day...

In the early days of loudspeaker development, loudspeaker efficiency was critical because the early tube amplifiers were only able to deliver Watts in the single digits. If your speaker system wasn't very efficient, you just wouldn't hear it. For most of the history of sound reproduction, amplification was the most expensive element of the system.

It still is, but now the cost of the amplification is much lower, especially relative to the costs of drivers, materials, labor and shipping. The weight of the amplifiers has also gone down dramatically, making it a tiny percentage of the weight of a loudspeaker cabinet rather than the amps outweighing the speakers.

As the cost of amplification went way down, the market moved to smaller, less efficient boxes using more power to make up for the reduced efficiency. This made the power and power handling specifications more relevant for comparisons. Once the herd had turned and headed in the direction of bigger power numbers, well, let's just they still haven't turned back.

The real problem is that they ran off a cliff. The real problem is that in the madness of chasing the big numbers, the definition of a Watt coming from and amplifier got somewhat diluted. The methods by which amplifiers were rated for output power became vague and, to a large extent, misleading.

Here's the definition of a Watt from Wikipedia: "The Watt is defined as 1 joule per second and can be used to express the rate of energy conversion or transfer with respect to time." So 1 joule per second, blah blah, blah, with respect to TIME! There's the key part that got what I call "creatively interpreted".

If one Watt is 1 joule per second, how many Watts will you use in 1/125th of a second? And if you cycle on and off 4 times in one second, making the duration of the "on" cycle 1/32nd of a second, how much power will you produce/use?  1 joule for 1/32nd of a second is 1/32nd of a Watt.

Not officially, but what some amplifier makers want you to believe is that if they can produce a 98V spike for 1/125th of a second, and repeat that 1/125th of a second spike 32 times per second that they are providing 2400W. So, their claims are true for 1/125th of a second but in the long term, the continuos power available from a system rated that way is closer to 600W.

You can effectively de-rate these amplifiers by frequency. 1/125th of a second is the cycle duration of 125Hz, so at 125Hz the amplifier can deliver full rated power for one cycle. After that, according to the specification method, it needs a 4-cycle break. At 250Hz, you get 2 cycles, at 500Hz, 4 cycles and at 1000Hz, 8 cycles etc.

Going the other way it's not even that pretty. At 60Hz you have to de-rate by half, so 1200W and at 30Hz, you will have no more than 600W. In audio dynamics, a second is a long time, especially for acoustic instruments, but with keyboards and electronic instruments it's not uncommon to see a sustained bass note last well over a second. If your amp can't deliver for more than a few milliseconds, your subwoofers are going to sound gutless.

The takeaway is that in order to have a loud, clear and reliable system you need good conversion efficiency and good power. You can't expect low conversion efficiency with big power to be reliable. You can't expect solid low frequency performance from exaggerated power claims. You can't expect extremely high conversion efficiencies from reasonably sized portable enclosures. You can't expect the powerful amplification and the top-quality components that are required to produce the desired results for the cheapest price. What you really need is a properly engineered solution that balances the demands of SPL, reliability, sound quality, depth, weight, cost and electrical consumption. What you want is a ruthlessly practical solution to the demand for excellence.

3) What else matters besides efficiency?

See above! [smile]

You said "Efficiency is the ratio of work done to the effort expended. Watts are how we measure the effort expended and dB are how we measure the work done". Does efficiency correlate to effectiveness?

Not quite. See below.

If I read that right, that means it takes less watts for a highly efficient system, to achieve the same dB, as a higher watt/lower efficient system does.

That is correct.

When comparing two speakers, when a customer's main goal is how well a sub will shake a building, the two things to look at are the efficiency (dB output @ 1 meter) (E.g. 93dB@1 m = 1% efficient; 96dB@1 m = 2% efficient) and peak watts the system has?

Actually, if your goal is to shake a building, the most important things to look at are the frequency response and the peak SPL. You need high output at low frequencies. Nothing shakes a building like extremely low frequencies. The deeper the frequency response, the better. But don't look at -10dB figures. The -3dB figure is what you need to consider. Beyond that, many times I see response graphs that contradict the specifications. Look at the response graph. 30Hz is where you start to really shake buildings.

You should look for subwoofers with a -3dB specification below 30Hz. And with high maximum continuous SPL. And make sure the high SPL number is measured. And make sure the high SPL number is IN BAND, in other words a subwoofer than will do 140dB is worthless if that 140dB is happening at 140Hz. You will never use a subwoofer at 140Hz, and if you did, you wouldn't be shaking the building, you'd be shaking your head.

You explain the dB @ 1m with 1W, calculation very well. That shows how efficient a speaker can be, but then how do you add in the max speaker wattage? Do you take that efficiency rating and use it to compare speakers? (E.g I have two speakers with the same efficiency; one is speaker A is 100w and speaker B is 105watts. Does that mean speaker B will be louder since it has the same efficiency?

The short answer to that is yes.

The second part of the answer is that you won't notice the difference between 100W and 105W. You'll barely notice 150W. You'll notice 200W.

The third part of the answer is to point out a technical distinction. You said "speaker A is 100w and speaker B is 105w"...  Technically, the amplifier in A would be rated for 100W and the amplifier in B would be rated at 105W.  

Why is this relevant? Because loudspeakers (transducers) are rated for power HANDLING, not power. Their power handling rating is a measurement of heat dissipation capacity. It would have no influence on the output of the speaker. If speaker "C" had a 100W amplifier and a 200W (power handling) speaker it would be no louder than speaker "D" with a 100w amplifier and a 100W (power handling) speaker provided the sensitivities were the same. Speaker "C" would simply have excess thermal capacity, meaning it would probably last longer or prove to be harder to damage.

For example: my old Alto Black 18" subwoofer had 2400 Watts and it's Max peak SPL = 133dB @ 1 meter.
Frequency = 27-160Hz

Your ZV18 has 2400 Watts and it's Max peak SPL = ?
Frequency = 21Hz - 95Hz

The ZV18 is an extreme example. It's very inefficient in order to get very low. It's not a box that's even intended to get loud. It's not really a fair comparison for either box but it's an interesting exercise to see the extent of the differences.

First of all you quote the specs for both but you missed some critical differences. This illustrates A: Why these companies use these misleading number and B: Exactly what you need to pay attention to when looking at spec sheets.

Alto: 2400 watts is peak, only 1200 watts continuous.
BASSBOSS: 2400 Watts continuous RMS. Thats already double the power.

Alto: 27-160Hz. Those are their -10dB specifications.
BASSBOSS 21-95Hz +-3dB. That difference will probably result in a 7dB advantage to the ZV18 at 27Hz.

The Alto spec sheet says 133dB is the "maximum peak" SPL. Most companies specify peak SPL at 6dB higher than continuous, making the estimated continuous output of the Alto 127dB.

BASSBOSS has the ZV18 maximum sustained SPL at 127dB and short-term peak output at 130dB. The questions you have to ask yourself are, at what frequency will the box achieve its maximum output? Which one is more likely to deliver the output that it promises? Which one will deliver the most output at the frequencies where I really want it?

I would be very happy to subject an Alto Black 18 to the same tests as our boxes in order to get directly comparable data. I'm certain that the peak SPL will be measured at a higher frequency than any of our subs, probably cloe to their 140Hz upper limit. I fully expect that the peak SPL will also measure at a lower number when using the same extremely unforgiving test procedures we use on our boxes.

The BASSBOSS response requires no EQ, no boosting the low end.  I also noted that the specification you chose for the Alto was 27-160Hz, which is their -10dB claim. Their -3dB claim is 29-140Hz, which I also don't believe the box will be able to maintain at high output levels. The frequency response graph published in their spec sheet shows clear evidence that equalization is applied in order to achieve those response figures.

The benefit of the boost evaporates as soon as the volume is turned up because either the amp will run out of power or the driver will run out of excursion. The Alto box looks like the perfect example of a paper tiger. Make all the numbers look good on paper so it looks like a tiger, and when you get it home it's really just a pussy-cat.

4) If the dB for the ZV18 is the same as the Alto Black, then that would theoretically mean that they are equally as efficient and effective, correct?

Efficiency isn't the same thing as effectiveness. Efficiency can be defined and measured. (It could be specified at every frequency but we average to simplify.) Efficiency is like miles per gallon. A sports car and a mini van could get the same miles per gallon but knowing their miles per gallon spec won't tell you how effective the vehicle will be for taking kids to school or for carving through corners on country roads. Same efficiency, different effectiveness.

Effectiveness is subjective, it implies effectiveness for a particular purpose. In order to compare effectiveness we would need a metric of measure or a definition. For example, the Alto is more effective as a budget-priced speaker. To answer which one is more effective as a subwoofer requires that we know what you want a subwoofer to do, what your definition of an effective subwoofer is. To get a good sense of which one is more effective at making deep bass, you could look at the published response graphs side-by-side and evaluate which one is likely to produce more and deeper bass.

As a general rule, published response graphs will be provided for professional products and not available for products intended for consumers who will never look at the graph, nor understand it. There is no standard for publishing graphs so you have to pay attention to the frequency lines and the SPL lines and note the differences at clearly indicated points. 20Hz, 30Hz, 40Hz and so on. You could go so far as to re-draw them on the same scale. I've done that for some models that were not available to measure. It helps to be handy with graphics software or Excel if you're going to do this, or you can go really old-school and use grid paper and a pencil...

The key, though, is to learn to smell/see the BS. When you've looked at enough graphs, you can tell a lot about what's going on. Look for the notes and asterisks about how the data is presented. Is it smoothed? Is it processed? How and where was it measured? Check the scale. How much detail can you see? How many dB per vertical section? 3? 5? 10? Those things make a HUGE difference in how the data is perceived. If the marketing department made or edited the graph, it could be made all about manipulating perception.

You have to learn to see past the presentation and find the meaning. From what I can tell, specification sheets are a lot like online dating profiles. Everything is shown in the best possible light, from the best angle and with make-up or air-brushing applied. The genuinely hot products have less to hide, and they are harder to find.

If you put them together would they sound any different in regards to ability to shake a building If I'm wrong, could you please educate me further? Like you said, it takes years to become an expert on this stuff, but I'm trying my best.

If I'm right though, as someone who is going to try to promote and sell your product, what justifies the extra money being spent? Durability of the speaker assumed being nearly the same.

As I said, the ZV18 is not the best example for comparison to the Alto unit. {Funny, BASS (low) boss -vs- Alto (high)}  There would be a profound (pun intended) difference in how they shook a building. If your definition of effectiveness was "the ability to shake the walls and fixtures of a building with low-frequency sound," I'm confident the ZV18 would win.

We also have other boxes that would do that just as well or better. All of our subs would win against the Alto. The SSP118 is a better comparison for the Alto. It’s roughly twice the output and also very durable and reliable. I'd expect you to get almost 4 times the life expectancy, maybe more. And a better warranty. And better service. Theirs says designed and tuned in the USA. Any guesses as to where it's made? I can’t tell from their sheet.

BASSBOSS is designed, tuned, BUILT and SERVICED in the USA. The cabinet is made entirely from 18mm Baltic Birch. The BASSBOSS amplifier is recessed into the cabinet to protect it and the connectors from damage, and even spills, and features a locking Neutrik PowerCON connector. Theirs has bluetooth... And a switch to turn off the logo LED... One of these products is built for serious professionals and serious bass-heads. You tell me, which one do you think will be a more effective subwoofer? [smile]

I apologize for so many questions. I tried to split each individual question into a section for your convenience. Absolutely no need to rush and answer. Take as much time as you need. I know you are a busy man. I honestly appreciate the help. Online forums don't help very well, but your article helped me so much (that is, if I understood everything correctly).

Happy to help! Please let me know if there's anything else I can clarify.

Best,
David Lee
LA88 & ZV28 ideal match?
Hello,

Yes! The LA88 and ZV28 work extremely well together. The specified crossover points are acoustical for each of the loudspeakers but the two systems sum in phase through that 10Hz difference and there is no dip in the response related to their individual crossover frequencies.

Crossovers are slopes, not absolute cut-offs, so with a specified -3dB point of 80Hz on one side and 100Hz on the other side, there is still a great deal of overlap happening. In other words, both systems are producing energy above and below their respective -3dB cut-off frequencies and, with BASSBOSS systems, that energy is in-phase.

If the two systems were not phase-aligned through the crossover region, there would be a large dip in response, but because they are summing in phase as they pass beyond their -3dB frequencies, their combined energy produces a flat response. 

The gain of the subwoofers relative to the arrays will shift the effective crossover point, which is where both systems contribute equal amounts of energy to the sum total. If the subwoofers are run at a higher gain level than the tops, the effective crossover point is shifted higher in frequency.

Matching crossover frequencies and then adding gain to the low frequency section causes many systems to sound excessively boomy with too much energy being produced in the overlap region. Matching crossover frequencies without getting the phase alignment right causes many system to have a hole in the response through the overlap region and this is a problem that adding more gain to the LF section can't solve. BASSBOSS Systems are designed and aligned to work together.

Even if the two systems, sub and top, are phase-aligned, the physical proximity of the subwoofers to the arrays will have an influence on the combined response of the two, at a given distance, that is more significant than their relative crossover frequencies. Separating the subs from the tops will result in a dip in response somewhere in the listening area. Where that dip occurs is influenced by the placement and can be shifted using delay.

Ultimately the point is that the phase alignment, the relative gain and the relative proximity of the two systems will have a much greater influence on overall system response than a 10Hz difference between their -3dB points, and that we build all our loudspeakers to be used together to produce coherent full-range response regardless of the independent specifications of the individual products. The processing in the speakers provides settings for mixing almost any combination of sub and top to achieve the best possible result. 

To that end, the LA88 has multiple presets, only one of which is a satellite mode with-3dB at 100Hz. The others offer output to 80, 60 and 40Hz, each of which has slightly lower peak output capacity but present alternate benefits in trade.  

Please let me know if you have any questions and sorry it took a while to respond...
Best,
David Lee

Best Practices for Cleaning Bassboss Boxes
Hi Glen,

Here's a bit more detail on the cleaning suggestions.

The best thing I have found is a wet magic eraser-type sponge or a wet microfiber towel. The small particles of dust will get stuck in the texture of the finish so you need something like a magic eraser to reach in and pull them out.

Pressure washing does do that pretty well but it would not be a good idea to use a pressure washer because of the potential they have to do damage to the electronics, the drivers and the finish. Even a fairly soggy sponge has a lot less chance of getting water where you don't want it. If the dirt isn't oily, as in just dust, repeating rub and rinse with the sponge will get you the best possible results. This is also the best way to remove sugary dirt.

Oily dirt may require a surfactant, aka soap, like Dawn dishwashing liquid, but use it very diluted otherwise getting the soap off will be as much of a challenge. 

Adhesives may require goo-gone or other solvents to break them down but for spilled drinks and dust, the following should do the trick.  

Put the box in a position so the dirty surface is vertical and preferably below the electronics and driver. If the dirt is on top, the best position may be on its side. Proceed to scrub with the wet magic eraser sponge. If you get a trigger spray bottle you can rinse the area with distilled water. Distilled water is recommended because it doesn't conduct electricity (until something conductive is dissolved into it,) it is the best solvent in the known universe, (more things dissolve in water than anything else we know of,) and it dries without residue but it will cost about $1.00 a gallon. 

I don't recommend scouring pads or power tools as they could remove part of your finish. What you want to do is remove the dirt and leave the finish. 

Once you get to a point where no more dirt will come out, let the surface dry completely and then apply a light coat of tire shine. The tire shine will mix with the last remaining stubborn bits of dust and make them almost invisible.

If you use a microfiber towel for drying and final dusting you'll avoid the problem of lint that comes from paper towels or cotton towels. 

Happy scrubbing! 
SSP118 Powered Subwoofer VS the JBL SRX828 Sub?
It was run flat with the low-pass filter at 100Hz. Essentially we ran it as it came out of the box. We did not adjust anything in the DSP. 
Yorkville vs. BassBoss
I love talking about what happens in the real world!

First things first: Actually the woofer doesn’t simply move slower for lower frequencies. The amplitude required to produce the SPL drives the speed of the woofer’s movement. To produce a lower frequency the woofer has to continue moving in the same direction for a longer time. Thus the combination of the longer duration required for a lower frequency along with the greater amplitude required to produce high SPLs results in the demand for extremely large displacements and lots of quality power to manage and control the excursions.

You’re following the right path but people are apparently deliberately obscuring the way for you. You’re right to consider compression loss, but it may account for more than you think. The trouble with what you’ve done with that graph is you have taken a low-power measurement and assumed a 1-Watt power source and no losses due to heat and turbulence and transient overshoot or even amplifier output. The graphs I presented were actual real-world maximum power measurements.

As an example of what these thermal and power limit factors look like, below here is a set of measurements taken of a test enclosure. The first at 2V in blue, then with 33.8dB added to calculate for 2400W of power input in red, and the actual full-power sweep measurement in green. You’ll see about 6dB of difference between the calculated ideal between 30 and 35Hz and the measured response between 30 and 35Hz.

[Low-power_fullpower_calculated]   

As mentioned elsewhere, Danley does use the equivalent of 2.83V at 1M to derive their SPL figures. To their credit, Danley do measure at 10m and add 10dB of power, which pretty well eliminates the potential benefits of mic proximity. 2.83V output regardless of load impedance is the new industry standard. But that doesn’t restrict the measurements to 4 ohms and 2 watts.

This means, from what I can find in the documentation, the Danley DBH218 and the Danley TH221 are measured with 28.3V into a nominal 2 ohms. So because you’re starting with a 4-watt measurement, you have to back 6dB out of your maximum SPL calculations, and then you have to account for thermal losses etc., which would potentially take off another ~6dB at certain frequencies, especially at the power levels you’re discussing.  

One other detail is that the graphs you’re working from are measured without the “recommended processing”, which would pull 3dB out at 25Hz from the DBH, which would leave the response at 30Hz still down by about 2dB. The ZV28 is specified and measured with all processing engaged. If you re-draw that red line taking all these factors onto account I think it will reveal that the ZV28 is far from beaten by the DBH218.

Ultimately, in the real world, I think you will find it very hard to beat the ZV28 when it comes to most comparative metrics, especially when one of the metrics is low bass output and the others are either price or size or weight or even power consumption. Furthermore I think the ZV28 is more pleasant to listen to than any of the competing options, if that counts for anything.

From my experience you need 4 people or a forklift to move a TH221. The DBH218 is not as bad but still bigger and heavier and more expensive than the ZV28 and I’m very curious to see exactly how well they compare in a real full-power sweep test. You did note, as did the DBH218 spec sheet, that horn-loaded boxes work better in multiples, mostly increasing their low-bass output. The translation or corollary to that is that they don’t do low bass as well in singles. So if you’re looking for a smaller, more portable, more affordable source of high-output low-bass, the ZV28 is the one to beat., IMHO. [smile]

- David Lee
Yorkville vs. BassBoss
I resemble that remark! [biggrin]
Yorkville vs. BassBoss
Not a hijack at all - we intended this forum to be a place not only to ask questions but also for community discussion. I could go on for hours about this (and often do). Thanks for participating!

-David Lee
Best Practices for Cleaning Bassboss Boxes
Hey Glen,

Great to hear from you, as always. We agree, keeping the cabinets looking tight is preferable, and with some basic maintenance they can stay relatively new looking for years.

My first thought is to put them, woofers up, on a slightly smaller box or over a drainage grate. Get a microfiber towel and a bucket of clean water and wipe the box down with the damp towel. You may need to do this several times because the water will get dirty and need to be replaced.

You can remove the grill and wipe the cone with the microfiber towel as well. Once the cleaning is done, use a different microfiber towel sprayed with tire shine to bring back the shiny new look on the cabinet finish. Be aware that the tire shine will make the surface of the box more slippery, so when you're moving it, get a firm grip.

On your boxes in particular, the ZV18 subs with your custom grills, the foam grill inserts can be removed and washed with running water. Hang them to dry before putting them back in. In AZ that should take about 5 minutes. [smile] You only have to take out the perimeter screws to get the custom grill off. Don't take it apart - it was a **#*# to get together and on.

Bed-liner is a great material for durability, however as you've noted, it has a tendency to pick up dirt due to its roughness. After a bit of clean-up though, your cabinets should be looking basically new again.

Let me know if you have any more questions and thanks!
David Lee
SSP118 Powered Subwoofer VS the JBL SRX828 Sub?
Hi John,

In frequency response terms, the JBL SRX828 performs almost identically to two SRX818, meaning it gives you the same frequency response with 6dB more output. The JBL SRX828 offers maximum continuous output of 134dB at 67Hz. That means peak output can be calculated to 140dB.

The BASSBOSS SSP118 is competitive with the SRX828, offering almost equivalent output between 35 and 50Hz. The SRX828 offers more output above 50Hz and a bit more below 40Hz. This is to be expected from a double driver sub. The design is essentially two SRX818 boxes joined at the port side. The SRX828 will deliver a bit more very low bass at maximum output because it helps to have another 18" cone to displace that air.

At maximum level, the JBL offers 3dB more output at 30Hz, 2dB more output at 35Hz, 0.8dB more output at 40Hz, 0.3dB more output at 45Hz and 0.7dB more output at 50Hz. Above 50Hz the two lines diverge, with the JBL continuing higher and the SSP118 going lower. At 55Hz the JBL double-18 shows a 3dB advantage, at 60Hz it shows a 4.2dB advantage, at 65Hz it shows a 5.7dB advantage, which it holds through 90Hz.  

The SSP118 was designed to be a subwoofer, to deliver as much deep bass as possible from a relatively small, portable enclosure. The fact that is does an excellent job at this is evident in the fact that between 40 and 50Hz, it runs neck-and-neck with either a double 18" subwoofer, or two single 18"s. In either case, the JBL's are twice its size. The SSP118 offers better low bass performance than all competitors' similarly sized single 18" subs that we've so far tested, and better than some that are much larger, including the Yorkville 21". The JBL SRX828 double-18 is the first box tested to offer more low frequency output than the single-18" SSP118.

An important thing to consider that is demonstrated in the response graph is the sound "character". It's true that you can't hear a loudspeaker by looking at a response graph but you can get an indication of its character.  These graphs can tell you a lot about what to expect in terms of "sound quality". You can determine where the energy is focused, what it does best and the overall balance across its spectrum.  This does give you a good indication of what it's going to sound like. The words people use to describe these things vary but a high resolution frequency response measurement graph will tell you a lot about the "character" of a loudspeaker. Is the energy focused at the bottom end of the spectrum, in the middle, or at the top?  What does it give up and where does it peak when you turn it up to the limit?

Under normal operating conditions, the SSP118's energy is focused between 35 and 55Hz.  What it gives up when it enters compression is some of the energy between 25 and 45Hz. When pushed to the limit, it peaks at 50Hz.

The JBL SRX828's energy is focused between 47 and 83Hz.  It gives up energy between 30 and 50Hz when it enters compression. When pushed to the limit, it peaks at 67Hz.

At maximum output above 50Hz, the SSP118's output decreases where the SRX828's output increases. This gets into the area of design choices and philosophy. Both at maximum and below maximum, the SSP118's output decreases above 50Hz. This is a deliberate choice intended to give the SSP118 a full, rich tone, to make it sound big and deep. To give it a big and deep character, it could not be designed to also go as loud in the upper end of its range. This is necessary to allow the SSP118 to get as loud as possible as low as possible and, when it's turned up to the limit, to prevent it from changing character and sounding different. Thus, at any level the SSP118 has a "deeper voice" than either of the SRX boxes.

In comparison to the SRX818, the SSP118 is deeper and louder. The SRX828 has a louder voice, but if you wanted to give the SRX828 a deeper voice, to match the tonality and balance of the SSP118, you would have to give up on much of the area where it is louder. So, if you like your bass deeper, the SSP118 will do very nearly everything the SRX828 will do from a box that's half the size. That said, the SRX828 is a good product for the price. Next we'll be testing it against our double 18" subs, and we'll post that as soon as we have the testing done.

BASSBOSS SSP118: 130dB continuous. 136dB peak. Peak output frequency: 50Hz
JBL SRX828SP: 134dB continuous, 140dB peak. Peak output frequency: 67Hz

On the subject of limits, if you do tend to run your system buried in the limiters and every bit of output is necessary, it might be tempting to consider the higher output SRX828. On the other hand, the BASSBOSS warranty covers your boxes for 6 years, your amps for 3 years AND covers you against blown voice coils for 2 years. The JBL warranty covers the boxes for only 2 years, the amps for 3 years and if you blow the drivers you aren't covered at all.

Thanks for your questions, I'm enjoying testing these subs!

best
David Lee
BASSBOSS_SSP118-v-JBL_SRX828-Max-Out.jpg 
Eq'ing the room with a BASSBOSS System?
Hi Glen,

In short, I don't think you'll need or want to add an EQ. The system components offer you enough controls and options to adapt to various environments without additional processing. In addition, all but the very best (read most expensive) EQs will deteriorate the signal quality and graphic EQs are an outdated design based on fixed frequency points that are never centered where your issues are or where natural harmonics occur.

You're better off knowing where to place speakers to minimize the reflections that are most often the cause of "room issues" for which EQ doesn't really help. You can't EQ out a reflection because most of the issues they cause are related to arrival time, not signal amplitude. If, after you've used the system for a few months, you decide you must have an EQ, you should get a parametric EQ. You'll do more good and far less damage with a 4-band parametric EQ than a 31 band graphic EQ. They also offer a better opportunity to learn what does what and how to get better results.

There's a guy I know who loves to take his iPad analyzer out and show it off, make pronouncements and "tune" systems based on what he sees. I know of another guy who goes into clubs with an RTA and "tunes" systems with it. What they both don't realize is that what they see, regardless of the quality of the mic in use, is only relevant in that exact location and will not tell the same story as little as 6 inches from that spot.  What they also don't know is that they are measuring the sum total of all the acoustical energy bouncing around in the space with no reference to time so there's no way to tell the difference between the primary and reflected energy. The one guy has good ears and the other one is a good salesman. Neither one is helping as much as they could if they knew how to use a transfer function FFT system. And to be frank, the guy with the good ears does more good using them than his RTA and thankfully uses it more to show off than for data acquisition.  The other guy uses the RTA and, from what I've seen, does mostly damage.

I fully support you in your desire to know and understand the process of setting up and optimizing sound systems and knowing how to measure systems properly is a valuable skill, as is knowing how to interpret the data you acquire and what to do to implement corrections. The good news is that the speaker system you've bought will need nothing in order to deliver outstanding sound quality under most conditions. The bad news is there isn't much more that can be done to improve its performance in the field. To put it another way, you've just bought a Ferrari. You won't need to be re-mapping the fuel injection. ;-)

What you can do is make changes to adapt to personal tastes and to adapt to odd setup placements etc. The changes to adapt to personal tastes can be made with an EQ of one sort or another but doesn't require measurement equipment.  If you get to a point where you're doing a lot of unusual setups, I'd recommend getting a transfer function capable FFT measurement system like Smaart and taking a class on how to use it and interpret the data so you can ensure you're moving things in the right direction.

Best,
David Lee
Interfacing with Previous Mobile System?
Hi Jimmy,
That is correct. Let me know if there's anything else I can do!


best
David
Interfacing with Previous Mobile System?
Hi Jimmy,

The BASSBOSS systems are designed to provide everything you need after your mixer. You can connect from the outputs of your DJ mixer directly to the inputs of these speakers. The level controls and presets in the boxes allow you to taylor the sound to your taste and to the environment without any additional equipment. This helps minimize the amount of gear you have to transport and simplifies and speeds up setup and take-down. It also eliminates any equipment that could potentially degrade the sound quality or introduce unwanted noise to the system.

Specifically, use the cables we provide to connect from the balanced line outputs of your mixer to the speakers and adjust the level controls on the backs of the speakers to get the desired sound level balance between the tops and the subs for your taste, musical genres and your application in the performance space. Take a moment to listen to each of the presets (in the top boxes) to get the best balance of the high frequencies in your space and at the audience distance. Details about what the presets do and which ones to use are in the instructions for your speakers.) Normally the lower number presets work for smaller spaces and higher number presets work in larger areas or outdoors. Other factors like room acoustics can influence your choices so it's a good idea to listen to them to make the choice. Once that's done, you're ready for your show. Enjoy!

David Lee
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