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Reply with quote  #1 
I'm sorry to bother you so much, but I'm reading your articles and that is some of the most help I've had in finding what specs are important when looking at options for speakers. Of course I'm still not an expert but this really helps! If you could help clarify though, when looking to buy speakers, of course wattage, dB output and frequency spectrum are important, as well as quality of the speaker and durability, but as a consumer I've always just looked for some of the biggest number watts the system can put out and I go with that. (Which you implicitly mention in your article, is how most speaker companies are successful in selling their products but is not always the best speaker for the customer's needs).

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?)

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).


3) What else matters besides efficiency? 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? 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.

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? 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?

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

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? 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.

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).

Thanks,
Zach S.
BASSBOSS - David Lee

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Reply with quote  #2 
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

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