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Voltages, power draw, and ZV28s OH MY!
Hey there ADJS,

Yes, the voltage remains the same. When adding a second amplifier, the current doubles. The current limit of the amplifier doesn’t change when the voltage changes. When running on any voltage, the amplifiers limit their current intake to 16.5A after 1 second regardless of the line voltage. For less than one second they can draw over 30A each. The nature of a breaker is that it trips based upon current flow over time. The more current, the faster it trips. 20A breakers will allow much more than 20A for short periods of time.

Current (flow), not voltage (pressure), is what heats up wires and connectors, so current is the limiting factor for connector and cable ratings, and breakers. The reason you get more output from the amp on 240V is that when there is more voltage, there is more power available at the same current flow limit. If you put two amps on the same circuit, they will draw double the current of one amp. At 120V 16.5A allows only 1980W of continuous power. At 240V, with the same limit of 16.5A, the power available is 3960W.  On 240V, two amps at their limits would be drawing 33A of current flow, which would make 7920W of power available. (These numbers are all continuous draw and assume no losses. In reality, audio amplifiers don't demand continuous draw because of the dynamic nature of music. The amplifiers have storage capacity that allows them to deliver more power for brief periods and, due to the varying impedances of the woofers, the amplifiers don’t need to pass that much current very much of the time. These particular amplifiers run between 93 and 98% efficient, so 2 to 7% operating losses.)  

The bottom line is that connectors are rated for current flow. A L6-30 outlet is rated for 30A of continuous current flow. The blue and white PowerCONs are rated for 20A of current flow. Each amplifier draws a maximum continuous 16.5A of current. It’s fine to run 33A of maximum continuous current flow through a 30A rated connector, but it is less well advised to run the same flow through a 20A rated connector. If the connector heats up, it will not only wear out, but it will add resistance which will reduce the available voltage and the available current. The chances are you would not have a problem with using the 20A connectors because all these devices are rated quite conservatively but why cause a bottleneck if you don’t have to?

David Lee
Question about the AB-36-B and TS-42 from Cerwin Vega
Hi There,

When I first started out, back in the late 80's and early '90s, I used to sell people Cerwin Vega when they were on a strict budget. The boxes were loud but they always required a lot of tweaking in order to make them sound better. No matter what I did, I could not make them sound good. Yes, they could be made loud but never really enjoyable. No matter what you did to them, they never gave you a sense of warmth and pleasure. They were always struggling or sounding somehow uncomfortable. People running Cerwin Vegas always seems to want to add those BBE sonic maximizer's or some other kind of Band-Aid fixer EQ. If you run something like that, or have ever been wishing for something you didn't get out of the Cerwin Vegas, you know what I'm talking about.  Back then I didn't know exactly what the problem was, but now I do, and here's what my take is.

We have not done our latest direct comparison testing of the Cerwin-Vega AB-36-B or the TS-42 but we have tested other Cerwin-Vega boxes of the same style using different test equipment so we do have some data on which to base a comparison. I would LOVE to see the results of our new tests because, based on those earlier tests, I get the impression that the TS-42 specifications are somewhat misleading. The first thing I noticed on the TS42 was that the specification said: (-3dB) 35 Hz - 215 Hz.  The standard specification is (+-3dB) The fact that they left the + off throws up a red flag for me, making me think that the response of the box isn't +-3dB, aka "flat" but rather that they have picked a point at 35Hz and looked above that frequency to where the response drops to the same level without regard for how high it goes in-between those two. Testing would verify if this were the case.

The second thing I noticed was the claim of 108dB sensitivity combined with a claim of a maximum SPL of 144dB. FIrst I would expect that the peak sensitivity of this box would be in the 150 Hz range and that the peak SPL would also be in that range. If so, and you don't use the box crossed over above 160 Hz, you would never see the benefit if this SPL number. Second, the 144dB peak SPL number is theoretical, calculated based upon claimed sensitivity, not measured. This is indicated by the absence of any thermal losses which would cause the measured number to be slightly lower than the theoretical number.

What these observations tend to indicate is that the specifications have been cherry-picked to highlight the big numbers but that there is no information that ties them all together. Sensitivity is quoted at 108dB. That's high. Peak SPL is 144dB. That's high. Frequency response is quoted to 35 Hz. That's nice and low. These are all potentially good things... But the frequency response also goes all the way up to 215 Hz... So where does it do 108dB? 40Hz? 140Hz?  Big difference and no way of telling. And will you REALLY get 144dB in the field? Here are the conditions required for you to get 144dB: 1) It has to be at the frequency that the box is most sensitive. 2) The amplifier must be capable of 4000W into 8 ohms. 3) The voice coil must remain cold. Working backwards, it's impossible for the voice coil to remain cold once you apply any power. If you applied 4000W to the driver it would get very hot and fail in a very short period of time. It's very unlikely that you will want any subwoofer operating at the frequency where this one offers maximum sensitivity so the whole premise of it providing 144dB is moot.

As a general rule, boxes of this type have peaky response that increases in sensitivity as frequency rises. They have specifications that indicate they are loud, and they can be, but not necessarily where you want a _subwoofer_ to be loud. If a box has a response that rises by 12dB per octave above its intended operating range, the effect of a low-pass filter with a 24dB/octave slope becomes only 12dB per octave and the subwoofer will then interact with the tops a lot more than you might want. This situation is less than ideal because it can either make the system sound boomy, especially if the subwoofer overlap happens to be in phase with the tops, or it can make the system lose impact if the two are out-of-phase. While the relative phase of any random sub and top combination could produce the same result, using the types of subs that offer maximum output sensitivity above their actual operating range tends to make the problem worse.

BASSBOSS builds subwoofers that do the work that subwoofers are supposed to do. You specifically mention low frequency bass and I am very confident that our boxes deliver the best low-frequency bass performance on the market. Whether you compare dollars to deep-down decibels or size to subwoofer sound pressure level, BASSBOSS provides outstanding performance, quality and reliability, which all together adds up to superior value. We know they will cost more than anything from Cerwin-Vega but what our products provide is completely different on so many levels. The frequency content of music and the expectations of audiences has changed. The sophistication level of processing and control has changed. Cerwin-Vega builds good products for a budget and you can buy more of their boxes than ours for the same money. BASSBOSS loudspeakers include amplification and processing and, because the power and processing are integrated with the loudspeaker to create a matched and balanced system, there is also excellent warranty coverage. The cabinet is covered for 6 years, the electronics for 3 years and the drivers are covered against any failure, including blown voice coils, for 2 years.

When you go into a hardware store to buy a drill bit, what you really want is a hole in something. If you want a bigger hole, you buy a bigger bit, even if it's twice the price. You don't buy two smaller bits because A) you can only drill one hole at a time and B) two smaller holes isn't the same thing as one big hole.  If you go into a music store to buy a subwoofer, and what you really want is low bass, what's the better solution? If you want more and deeper bass, would you buy a better sub that goes loud AND low rather than 2 subs that go louder but not lower for the same money? You'd have at least double the boxes to move and no more deep bass. We believe that delivering massive output at low frequencies in the real world is more important than creating spec sheets with big numbers that can't be realized where you want and need them. Essentially I'd estimate that you could buy two of the TS-42s with an amp for the price of one powered VS21. The VS21 is much smaller and much lighter than one of those beasts, let alone two, and it might even deliver as much deep bass as two of the TS-42s. We'll do the testing to find out if we can borrow or rent one somewhere...


David Lee
What Do You Want in a Car Sub?

Hey Aaron,

Thanks for this great info! David Lee has been busy designing a whole raft of new pro subs and hasn't had a chance to delve into this as yet... stay tuned for some exciting new developments!

More soon,
best!

Can I run my system on a generator?
Hi D. C.

I hate to be the bearer of bad news but I took a look at the generator info and I'm a little concerned whether it will do what you need it to do. If you're needing this generator to provide power for an audio system, it may not be the right tool for the job. It isn't easy for a generator to handle the kind of load that big amplifiers present. If you haven't discussed this application with the manufacturer, I suggest you do. Reading the Q&A about the generator in the link you sent leaves me wondering.

This generator can supply 50A, or 12,500W continuously. Amplifiers draw their power in pulses, something that very few generators of this sort are equipped to handle. When we've connected two subwoofer amps to a 30A generator like this, the generator bogged when the bass hit and the amps shut down due to the drop in voltage. This happens because the generator can't "predict" when the demand will hit, so it's constantly reacting to the load and it's too slow to keep the power level up. When the generator is running motors, lights or heaters, the draw is constant. When you turn the device on, like a light, a fan, a refrigerator or an air conditioner, the generator senses the draw and increases the power by opening the throttle. The throttle then stays open until you turn the device off.  Music signals are constantly fluctuating, so they demand a power source that is full-on all the time, with regulated voltage and the capacity to handle the pulses the amps draw the way a car's suspension handles highway joints. For a little generator, the amplifiers' irregular pulsed draw characteristics would seem more like curbs and ditches or even mountains than minor bumps. They can stop the generator in its tracks.

So, assuming that this generator can deliver a constant 12,500W at full power, it may be able to power the two VS21s and the two AT312s and a set of CDJs and a mixer.  At peak draw, the VS21 subs will pull 40A between them. Granted this is for a short time, but that doesn't help if the generator's not "ready" for it. So you have about 10A left for everything else. But if the voltage drops for just a moment, the electronics in the amps and CD players will shut of to protect themselves. I thought it best that you know this as soon as possible so you can find out if that generator can really meet your needs.

In case you're wondering why you can run more equipment on a 50A distro than a 50A generator, a 50A distro can pass 50A of current constantly and can pass 100A of current for a few seconds and 200A of current for less than a second. When connected to the main power grid, which has virtually unlimited reserves, and provided the draw pulses aren't more than a few seconds, you can get a lot of power through a 50A distro. A 50A generator like this one has a maximum capacity of 73A, and no reserves after that. When you run out of reserves, voltage drops, and the result is a brown-out of your system.

If after investigating further you find that generator can't do what you need, I'd recommend you consider the advantages of renting a generator when you need one. You can get any size generator you need whenever you need it, it will run quietly and you don't have to maintain it or even change the oil. And if the rental generator has a problem, they can bring another one...

I hope you find this information helpful. Let me know if I can be of further assistance.

best,
David Lee
Yorkville vs. BassBoss
Hello again!

Thanks for the clarification! David Lee is working on your response, and we'll have that info for you soon.

Best from the BASSBOSS team!
What Do You Want in a Car Sub?
Thanks for all the interest in our car sub! In order to get you what you really want, we need to know what you really want...

We're working on 18" and a 21" car sub because they offer much more displacement to achieve high SPL at low frequencies. There are plenty of smaller alternatives but not too many options for big drivers. Are 18" and 21" drivers too big for your car?

Would you rather buy the driver and amp and build your own box from our design? Or would you rather buy the whole package ready to go?

For the whole package deals, we need to know what vehicle you'll want to put it in. There are many shops around the country that can build boxes, too. Would you like to have the box built for you customized for your car?

These drivers, amps and boxes aren't cheap, so consider how much you're willing to spend. What is a budget for your ideal car sub?

BASSBOSS subs are designed to deliver massive output for extended periods. We do this by managing the combination of cabinet, power, processing and driver. This ensures reliability for the long term. To maintain this pattern of performance in the car audio market, we have to design a system of components and electronics that meet our requirements.

We are currently testing drivers that offer outstanding performance at high power levels and operate in relatively small enclosures. We are researching amplification options that can take advantage of the properties of these drivers. We are also working on integrating the proprietary BASSBOSS processing into the amplifiers. This takes time, so we want to take the time to get it right and we want you to tell us what's right for you.

It's a lot of fun to have a system that can do extreme sound pressure levels, I know this from experience. What the BASSBOSS system is intended to do is allow you to get the SPL you want, for as long as you want, without having to worry about blowing your drivers or overheating your amp or melting your alternator. In other words, to crank it for as long as you can stand it. It won't be built just for showing off, it will be built for listening to music whenever and for as long as you're in your car (and wearing your hearing protection!)

So tell us if we're on the right track here. Tell us if there's anything you wish a car sub could do that it doesn't. What do you love? What drives you crazy? Tell us what YOU want and we'll do what we do to make it possible.

Thanks!
David Lee
srx828 vs ssp218
Hello!

The BASSBOSS team have been running around like crazy for our annual extravaganza of SXSW, and David Lee hasn't had a chance to get to your question, apologies!

We were not able to rent the SRX828 so David will use published specs and graphs for his comparison. Stay tuned, and he'll get back to this shortly.

thanks!
Sound Level Issues for an Overnight, Outdoor Festival
Hello,

Outdoor festival production faces many challenges but one of the most difficult to manage is noise pollution. Bass, aka low-frequency noise propagation, generates the most complaints from local residents. Festivals don't tend to invest in the management of these issues due to the temporary nature of their sound output.

It often falls to the individual sound companies to address these issues to the best of their abilities. Long-distance low-frequency sound propagation is a also significant concern for industrial and transportation sectors. Thanks to their extensive resources, software is available to analyze and predict the acoustical paths and potential remedies. An excellent environmental acoustic assessment program that can assist in noise control design and strategy during planning and construction can be found at olivetreelab.com/Terrain

Other software specific to the concert production industry can assist in predicting and illustrating steps that can be taken to minimize a festival's impact on the surrounding residents. These programs can be used to predict propagation over shorter distances but also offer valuable information related to how to orient the noise sources in order to dramatically reduce the noise propagation that tends to disturb local residents.

Two softwares that are free to the end user are Meyer MAPP XT and AFMG Ease. MAPP predicts the performance of Meyer loudspeaker systems but the laws of acoustics apply to all systems equally. MAPP predicts planar response, which is to say 2-dimensional propagation. You can, however, create a vertical and horizontal prediction of each simulation. Ease allows you to create a single 3D simulation but gives you 2 dimensional views of the propagation.

All these programs deal with propagation in air. Propagation of sound system energy through the ground is not considered. The speed of sound in solids is significantly faster than in air but the energy required to move the mass of the ground over large distances is generally greater than can be generated by common loudspeakers. Trucks and trains weighing many tons rolling over bumps generate far more energy into the ground, which is why the transportation industry is a great resource for noise mitigation information.

With regard to primary isolation, in a multi-family residence or shared commercial space where people share walls, floors and ceilings, isolation is critical. Preventing the direct transmission of energy from solid to solid, such as from a wooden speaker box to a concrete floor, makes a huge difference in how much energy reaches the neighbors' spaces. For instance, placing a speaker on a sponge rubber mat allows the mat to absorb the vibrations rather than transmit them directly into the concrete. On the other hand, over greater distances where structures aren't physically coupled to each other, separating speakers from the earth isn't of significant benefit.

It is known that sand and soils dissipate energy when subjected to cyclic loading, so sand has long been used as an excellent low-frequency absorption medium. Putting speakers on sand is an effective de-coupling mechanism on its own. As far as propagation to distant neighbors are concerned, pallets and blankets appear to have no beneficial effect at the offending frequencies.

There are much more effective and relevant options to consider. To illustrate what can be of benefit, I ran simulations in Meyer's MAPP XT of a speaker on the ground and of a speaker elevated 5 feet above the ground. (See below.)

Image-1.jpg 
The simulation indicates that the elevated speaker (upper simulation) actually propagates more energy over greater distance than does one directly on the ground. (Bottom simulation.) With the speaker elevated, the sound reflected from the ground acts as a second source.

These simulations cover a an overall length of 1500 feet with the stage facing from left to right and the propagation distance of 1125 feet from the speakers to the farthest (right) edge of the simulation. The patterns will hold true over greater distances but wind and the terrain do have an increasing effect as distance increases.

In looking for ways to provide a more comprehensive and scientific approach to solutions, it's useful to note some additional factors that aren't often considered or understood about sound propagation.

Many people have heard that low end is not directional, which is true when a single radiating source is involved, however when there is more than one source of low end, the interactions produce very significant directional effects.

Image-2.jpg

Image 2 (above) shows the propagation pattern of a stereo pair of subwoofers placed 20' apart. This pattern is viewed from above. It's clearly evident that the interaction between the two sources creates areas of reduced sound propagation, specifically 45 degrees off axis from the direction of orientation.

It's evident that orienting the system(s) has a greater influence over how much energy reaches a particular area than elevating a speaker or any de-coupling concept. A simple plan of orienting systems 45-degrees away from the nearest residences or potential complaint sources would allow the event organizers to minimize the noise levels at the nearest potential complaint points as well as minimize the interference between adjacent systems.

Simply drawing a line on the ground or tying a ribbon between two stakes to show which way a system needs to be oriented allows the participants a guide for system placement without restricting their creativity and all that's required to create sufficient directivity is a simple left-right speaker system.

If a participant wishes to use a large line of speakers, not in a left-right configuration, (shown in image 3, below)  it's still practical to orient such a system so that neighbors both near and far are minimally effected. The area of least radiation for a line of speakers is 90 degrees to their axis but they radiate nearly as much energy backwards as forwards. Pointing a big line of speakers "away from" the neighbors isn't nearly as effective as pointing the speakers crosswise relative to the neighbors. If the organizers know where the neighbors are and what the system configuration is, they can provide the information to the participants about which direction to aim their system, again by providing nothing more complicated than a line on the ground.

Image-3.jpg

Even greater control can be achieved using cardioid programming, (as shown in image 4, below, also viewed from above) but it is expected that the majority of the systems in use will not have the capabilities or expertise to benefit from this technology. 

Image-4.jpg 
For events that provide the sound systems, and for the audio production companies that serve them, it's worth considering deploying cardioid system configurations to minimize the spill of noise to the surrounding area. Most cardioid configurations are deployed for the benefit of keeping bass levels lower on stage. Even when festival producers specify the need for the control of sound bleeding off site, very few companies are able to utilize these technologies effectively for that purpose. I recommend that anyone interested in growing their production business invest time in learning how to deploy these principles because, as you can see from the information provided in this brief article, even without the application of complex cardioid system setups, it's possible to realize benefits from the naturally occurring interactions between ordinary speakers.

Let me know if you have any more questions. 

Regards,

David Lee
Sound Level Issues for an Overnight, Outdoor Festival
Hey David,

I'm going to be taking my system to an overnight outdoor festival. What are some steps I can take to not disturb my neighbors with the bass?

thanks!
Why Are BASSBOSS Products So &&#^# Expensive?
Dear Marcus,

Thanks for your question. I understand and encourage your skepticism. I know that in this industry it can be difficult to know who to trust because there are a lot of inflated numbers out there. I'd be happy to clarify anything that appears to be unclear.

The practice of using 1 watt at 1 meter is a hold-over from days gone by, when 1 watt was being made by a tube amp and bigger power was difficult to generate. The information it provides is relevant to determining a loudspeaker's sensitivity for comparison to other loudspeakers when each is driven by the same amp. The primary relevance of this is related to comparing passive loudspeakers to see which one would produce more SPL output at 1 watt input. From there one could calculate the theoretical maximum output given the power limit of the amplifier. This doesn't take into account issues like thermal compression, port turbulence, excursion limits or distortion, all of which are extremely low at 1 watt power levels.

Because we sell powered loudspeakers, there is no need to reference the sensitivity of the loudspeaker independent of the amplifier, which is why the specific sensitivity at 2.83V into 8 ohms isn't part of the specifications. Our amplifiers, drivers and processing are matched for ultimate performance as a system. I've seen many specifications of sensitivity that, if you investigate them, reference output SPL at frequencies outside their intended operating band. I've often seen sensitivity and peak SPL numbers for subwoofers based on levels at 120, 160 or 200Hz, which is well outside the range I would consider using a "subwoofer".

It's difficult to have honest numbers be competitive with inflated numbers. Marketing departments and the general public all want to see the biggest numbers possible. Big number for power amps encourage the use of "peak" watts specifications. Our subwoofer amps are rated on continuous RMS power. We don't even list peak power. People who know a little more can see the difference but it's still possible for people to be misled. Part of the problem is that there are misleading standards. For instance, 1 watt / 1 meter measurements aren't always what they seem. The standard recently changed. Technically, the result of putting 2.83V through 8 ohms is 1 watt. If you want to measure an honest 1 watt into 4 ohms, you must put in only 2V to get 1 watt. The current practice of using 2.83V as the standard output voltage regardless of impedance can produce misleading numbers because 2.83V into 4 ohms is 2 watts and 2.83V into 2 ohms is 4 watts. To be strictly accurate, I use the voltage required to produce 1 watt into the loudspeaker's nominal impedance to calculate its sensitivity but it isn't published because that information isn't relevant to the customer's use of a powered speaker.  Strictly speaking, input sensitivity of a powered loudspeaker is adjustable via the input attenuator and is driven by a pre-amp output.

While it is useful to test loudspeakers in an anechoic chamber because they isolate the loudspeaker and microphone from wind, weather and reflections, the purpose of the anechoic chamber is to simulate an uninterrupted acoustical field, in other words, outside, suspended above the ground far enough to be able to measure to the lowest operational frequency of the loudspeaker without the influence of reflections on the measurement. An anechoic chamber is an idealized environment in which to measure a loudspeaker, and one that can be used year-round in controlled conditions, but it isn't a natural environment. Loudspeakers developed and tested in anechoic chambers will never be used in such an ideal environment again. In addition to that, the environment is an attempt to simulate an outdoor measurement on a clear, windless day. We are based at an airport where we have no noise restrictions and a massive cargo-jet parking lot for our testing area, so we have what is essentially an anechoic environment rather than an anechoic chamber.

For mid-high boxes, an anechoic chamber of sufficient size is possible, however an anechoic chamber will have a low-frequency limit at which the room is too small to not influence low-frequency measurements. Anechoic chamber measurements of subwoofers are very rare because to achieve anechoic conditions down to 20Hz you need to have an extremely large anechoic chamber, something the size of an aircraft hanger. That's why 1/2 space/ground plane measurements of subwoofers are very common. Full-space performance of subwoofers can be reasonably calculated by subtracting 6dB from the 1/2 space measurement.

Because we put a lot of focus on subwoofers, and we have a more appropriate environment in which to test subwoofers than an anechoic chamber, and we have plenty of clear days here in Austin, TX throughout the year on which to test, we found we had little need for an anechoic chamber. We also measure our mid-high boxes under the same conditions as our subwoofers because these conditions are more similar to how and where they will be used than an anechoic chamber.

Our output and frequency response ratings do specify distance and conditions,  such as 1 meter in half-space, aka ground plane. Since the subwoofers are most often used on the ground, the specifications tell you exactly what you will get with the subwoofer on the ground in a very large space or outdoors.

If there are any specifications about which you have questions, please feel free to point them out. I'll do my best to clarify them and it's not impossible that a data entry error could have occurred.

best
David Lee
How Do Loudspeakers Make Sound?
A very cool infographic about how loudspeaker technology creates sound.

http://animagraffs.com/loudspeaker/
Troubleshooting Sub Performance?
Hi JP,

You may have checked some of these things already so bear with me because this is a weird situation that I have not encountered before.

The first step is to eliminate any potential external sources of problems. This means eliminating all outboard signal processing from the signal path. It’s recommended that you run the signal directly from the source, whether an iPod or a DJ mixer, directly to the speakers. Digital boards with builtt-in processing or external analog or digital processing should be bypassed to eliminate them as potential causes of the problem. They are not necessary with BASSBOSS equipment.

With that done, the first thing to do on the subwoofers is make sure the crossover, EQ and delay settings are identical. Check the knobs first by turning them all the way to one direction and make sure the pointers are pointing the same way. Next turn the gain all the way down on one of the subs. Play something familiar, or a song that you've noticed an issue with before on one sub. Check the sound in various locations about the room to ensure it's not an effect in one particular spot. (Ideally this would be done outside but if both boxes are against the middle of a wall the reflections should be consistent.) Turn up the second box and note whether the overall sound improves or whether the particular note/frequency loses level.

If the note/frequency loses level when the second box is added, there is a problem with the DSP programming and something must have saved incorrectly or there is a problem with one of the pots (knobs) and it isn't reading the setting correctly.

If the sound is consistently improved when the second box is added, then there isn't a problem with the amp or the box. The problem may be with the placement in the room or it may be that the target frequency you're wanting is outside the operating range of the subwoofers. I did a spectrum analysis of the single ladies song and also ran it through a parametric EQ and I think the frequency of that kick is about 125Hz. The one in cha cha slide seemed to be about the same. You can try using a parametric filter with a narrow Q, boosting it 10dB then sweep the filter frequency until it really accentuates the beat you're looking for. That should tell you what frequency the beat is centered on, and from there you'll know whether the beat is in subwoofer territory or in woofer territory. If it's up above the subwoofers' range, the other subs may have been set to operate in a higher band and would have been louder in this range.

Another consideration is that the phase alignment of the tops to the subs is off in this mid-bass range.  Ideally, when the boxes are close to each other, their phase traces will overlap through the crossover region. If they don't, there will be a hole in the frequency response in the crossover region. The center frequency of the hole will shift about with placement but there will be a hole somewhere if the alignment isn't right. If the phase alignment is right when the boxes are physically aligned, there may be a ripple or a slight peak when their physical relationship is changed but not a bad hole until the tops are about 5' to 6' away from the subs. This is a more difficult thing for you to analyze but there is a relatively simple way to check it. Place a top on a sub.  Turn everything on but leave the gain of the sub all the way down. Play the reference track without the sub then add the sub. Does the referenced beat frequency get louder or softer when the sub is added? If it gets louder, things look good. If it gets softer, there may be an issue.

The procedure to go deeper than this little experiment would be to put the two speakers next to each other with a measurement mic in front of the pair so that the mic is the same distance from the fronts of both speakers. Both have to be powered on. Measure and capture the response and phase of one and then the other. Then measure the combined response of both. The summed response should be higher at all frequencies where they overlap. This will be the case if the separately measured phase traces overlay. If they don't, either a crossover filter or a delay setting needs to be adjusted until they do and the summed response is entirely positive. On the plus side, once you have the two aligned, you can compensate for physical offset with a tape measure and a delay setting. Unfortunately, until you know your starting point is correct, deriving a delay setting from physical offset is not guaranteed to result in a re-alignment.

Confirming the ideal filter and delay setting for every other top box on the market is an impossible task, and most of the time it isn't necessary because the majority of powered boxes use a DSP with similar latencies and similar filter types. This may not be the cause of your problem, either. I mention it mostly to be thorough and to give you the opportunity to evaluate the possibilities. If all the other possible causes are exhausted, checking this alignment may come into play.

Once it's determined whether you're having an equipment problem, a phase problem, a placement problem or an operational range problem, we will know what needs to be done to sort it out.

I look forward to hearing what you find.
David Lee
Could you explain the differences between the ZV28 and the Yorkville LS801P and LS2100P?
Hi Ricky,

Here are two graphs. The first one shows the responses of the 3 boxes at low power. These give you an idea of their relative performance at normal listening levels. This graph shows the range of 20 to 200Hz.

The second graph shows the responses of the speakers when pushed to their absolute limits. I zoomed in on the 20 to 100Hz range for this graph because all the boxes are not really intended to be used above 100Hz so this focuses on the area you'll be using a subwoofer.

Sorry but I didn't remember to match the colors of the lines between the two graphs but you'll be able to recognize the speakers from the similarity of the curves and from the legend at the bottom.

You'll see that the horizontal lines are 1dB apart. When you double the number of boxes of the same type, total output is increased by 6dB. So, if you wanted to figure out how many of the LS801P it would take to deliver the same level of sound at 30Hz as a ZV28, you count the lines between the two at 30 Hz and double the number of boxes required for each 6dB.  At maximum output, I count 20dB between them. 6dB more would come from 2 boxes, 12dB more would require 4 boxes and 18dB more would require 8 boxes, meaning it would take about 8 of the LS801Ps to reach the same level as one ZV28 at 30Hz.  It would take at least 3 of the LS2100P to match the ZV28 at 30Hz. 30Hz is where the quantitative comparison to the ZV28 looks the best and multiples of the other boxes can outperform the ZV28 at higher frequencies but the ZV28 offers very even response throughout the subwoofer range, which the others don't, so the qualitative difference will be noticeable at every level.

I hope these graphs and notes help to clarify the differences. Please feel free to ask questions that I may not have answered.

Thanks,

David Lee
   
York-LS801+2100-V-ZV28.jpg  York-LS801+2100-V-ZV28-at-MAX.jpg 
4 TRX218 Carvin subs VS. 2 ZV28 Subs?
Hi Darren,

I downloaded the Carvin specifications and copied their response curve into my LMS for a relatively accurate comparison of the responses at 1 watt. I assumed they used 2V into 4 ohms rather than 2.83V. I used an unfiltered, unprocessed 2V graph of the ZV28 because I'm assuming they also measured without filters.

As you can see, there is a significant (7dB) difference at 30Hz. This difference will get bigger if the Carvin requires a 30Hz HPF because that will pull 30Hz down by another 3dB. The ZV28 HPF is set at 20Hz, leaving the response you see the response you get in the field. Based on my experiences measuring other boxes, I expect the differences will be even greater at high power.

To answer your question as plainly as possible, I believe that 2 of the ZV28 would closely match the performance of 4 of the TRX boxes above 35Hz and would deliver more output in the lowest ranges. I would need to do a maximum output test on the TRX2218 to say how much for sure.

When I do maximum output tests, I use a calibrated microphone and measure absolute (not relative) levels. My measurements of competing boxes tend to show lower levels than their published SPL specifications. This could be due to the short-term nature of their measurements relative to mine, it could be due to the publication of "calculated" SPL output numbers instead of measured, or it could be the their peak SPL numbers are derived outside the operating band of the loudspeaker. I mention this to point out that my specifications are conservative.

The TRX2218 is priced so low that it's hard to beat for value. That said, the ZV28 is an extraordinary value if you're looking for massive output in the very lowest frequencies. It also allows moving a smaller amount of gear, which can add up to a lot of value over time. I'm very curious to measure a TRX2218 to find out how many it would take to match a ZV28 at 30Hz...

Regards,
David Lee

ZV28-V-Carvin-TRX218-pubspec(1).jpg 
SSP118 Powered Subwoofer VS the JBL SRX818 Sub?
Hi John,

The first graph below shows the measured output levels of two loudspeakers driven to the maximum limits of their capabilities.  In other words, this shows exactly how loud they will go between 20Hz and 200Hz. The blue line shows the  BASSBOSS SSP118. The brown line shows the JBL SRX818SP.

The second graph shows the frequency response graphs of the two speakers when they are not being pushed to their maximum levels. So, when you're not pushing them to their very limits, this is an indication of the difference in how they will sound. The BASSBOSS is intended to sound warm and deep and big. It was designed with the sound character in mind, rather than with being able to meet a high SPL as the priority.

The test signal is swept sine wave from 200Hz to 20Hz. The calibrated microphone was placed 1m from the speaker grill with both the speaker and the microphone on a flat concrete surface. The microphone and speaker were located 50' from the nearest obstruction or reflecting surface.

The tests indicate that in the range above 65Hz, the two boxes produce very nearly the same maximum level however, below 65Hz the BASSBOSS SSP118 provides more output, showing a 3dB advantage at 55Hz, a 5.5dB advantage at 50Hz, a 6dB advantage at 40Hz, a 5dB advantage at 35Hz and a 3dB advantage at 30Hz.  It can be concluded that it would take 2 of the JBL SRX818SP to equal the 40-50Hz output of the BASSBOSS SSP118 and that greater output above 50Hz would be achieved by 2 JBL SRX818SP.

It is evident that the performance of the SSP118 is focused on the lower range of the spectrum and that even at the very maximum limits of its output, it maintains the character of a subwoofer. The SSP118 can also be seen to deliver 130dB output as specified, and does so at 50Hz.

The JBL is specified to produce 135dB, which, from this measurement we must conclude is a "peak" specification. Actual measured continuous output is 127.5dB at 65Hz. From there, peak output is calculated to be 133.5dB.

I'm sure a test could be devised that would create a result of 135dB peak output, but for the sake of comparing apples to apples on the same day in the same place with the same mic, the same electricity and the same test procedure, this is an accurate comparison. 

BASSBOSS SSP118: 130dB continuous. 136dB peak. Peak output frequency: 50Hz

JBL SRX818SP:       127.5dB continuous, 133.5dB peak. Peak output frequency: 65Hz

For those of you familiar with the relative energy associated with dB, a 3dB increase is effectively double the output. 6dB is 4x the output. Therefor a 2.5dB increase is approximately 85% more output. In the range between 40Hz and 50Hz, the SSP118 delivers approximately 400% of the JBL's output.  Looking at it from the other side, the JBL delivers approximately 25% of the SSP118's output between 40 and 50Hz. 

One JBL SRX818SP is less expensive than one BASSBOSS SSP118. If you were to use 2 of the JBL SRX818SP, together they will deliver more output than one SSP118, but only very little more where you really want it and feel it. When getting back to comparing cost, two of the JBLs would be more expensive and would be twice as much gear to carry around. In the long term this costs you in time and effort as well as money. In normal operation, it's possible to get effectively the same amount of heavy bass from one SSP118 as two JBL SRX818. 

The two boxes are very nearly the same size, with the JBL being slightly lighter.

The BASSBOSS box and electronics are designed and made in the USA. The BASSBOSS amp and connectors are safely recessed into the back of the cabinet. The BASSBOSS has 2 steel bar handles and a grab point at center rear.

The JBL box is designed in the USA and made in Mexico. Electronics say assembled in Mexico. The JBL has the amp flush with the back surface so the connectors extend behind the box. The JBL has 4 plastic handles.

 

Please let me know if there is anything I can clarify or expand upon.

Thanks for your question!
best
David Lee

BASSBOSS_SSP118-v-JBL_SRX818SP-Max-Out.jpg   
 
BASSBOSS_SSP118-v-JBL_SRX818SP-Matched-Level-at-65Hz.jpg
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