Are audio companies all involved in a huge conspiracy? - Page 11

Not so much. Providing far more amplifier power, and using a driver that can take all that power, is pretty much the only significant cost of reducing the size of the enclosure. Good clean amplifier power now has a very low cost - well under a dollar a watt. For example the most common power amp used by do-it-yourself subwoofer enthusiasts is probably the Behringer EP 2500/4000 which can really put out 2500 watts into a couple of 2 ohm subwoofer voice coils. They have a street price of under $400. Among other sources, Ficar sells subwoofer drivers for about the same price that can handle all that power. The incremental cost of the larger, husker voice coil etc is not all that much.

No at all. The cost of the small box is that exercising the swept displacement builds up more pressure in the box, where is essentially where the extra amplifier power goes. If the woofer had high efficiency we would get the energy we put into compressing that air back on the other half cycle, but unfortunately the efficiency of the woofer is on the order of 1% so most of the energy we put into the woofer is turned into heat.

Asked and answered.

Years of actual practice has shown us that we have to apply eq to speakers particularly subwoofers to match them with their environments, regardless of box size.

Yes, we can agree that no matter what we do, whether we build a relatively high efficiency subwoofer in a large box, or a lower efficiency subwoofer in a small box, there are compromises. The opposite of a small box subwoofer would be the people who cut holes in floors, walls, or doors and use a room or a basement for their subwoofer's enclosure. Pretty hard to tune them to the room by moving them around, eh? ;-)

It's all a matter of choosing the solution that involves the least amount of compromise and if given the choice between a small box and a big box I'll choose the least compromised option which is the bigger box. In fact I'll choose no box, thank you very much!

Yes and the associated costs involved still outweigh the extra wood needed for a larger cabinet. We'll have to agree to disagree on this one.

The extra amplifier power is required in the smaller box to overcome the additional internal pressure that is built up inside it. Not exactly a bonus for the woofer because any way you cut it, you need more excursion to overcome the forces in the box. You need more excursion to handle the extra EQ lift to achieve a lower F3 and you end up burning linear excursion and the potential for running into thermal compression. Horses for courses and all that. At the end of the day you have the Iron Law to contend with, no matter how you slice it.

Yes, except less EQ is needed when using a larger box to lift the response and that is what we are discussing. Yes, regardless of the internal EQ used to achieve the target curve you still have parametric EQ to shape the final curve we see. But that's not particularly relevant as most people I know don't boost dips but cut peaks.

Seems to me you need the power to overcome the stiffness provided by the small airspace, but my simple way of thinking is that moving the cone X millimeters at Y freqyuency will generate the exact same SPL, whether it's a huge box with less power or a smaller box with more power. Which is to say you need however much excursion you need to achieve the SPL you want, not more excursion for a smaller box. "Just" a bunch more power to achieve the same excursion (and of course when you build the driver heavily enough to withstand the power it loses sensitivity so more power again). Of course a vented box changes that more than a little arouns the tuning frequency.

Wrong. The SPL generated by the subwoofer at a given frequency is based on the excursion of the cone and its area. While it takes more energy to overcome the forces in the box, those added forces are required to obtain the same excursion of the cone.
Wrong. All the EQ does is bring the excursion back into line with what it would be for a larger box.

Wrong again. Excursion times cone area is what gives you the SPL. Same frequency, same SPL, same product of cone area times excursion.

Wrong again? Maybe yes, maybe no. But it is not a given. The high efficiency woofer has that high efficiency partially because the cone+voice coil assembly is lighter. The lighter voice coil takes less power to heat it up. It might get just as hot as the larger, heavier voice coil in the low efficiency woofer.

You need to study up on Hoffman's Iron Law. Hoffman said nothing about equalization, nothing about thermal compression, and nothing about needing more excursion. That is because they don't necessarily apply.

Not true. The F3 of the system in the small box can be dropped as low as desired by increasing the mass of the cone, and then no eq is required to offset the effects of a higher F3. Designers have the option not adding the extra mass, but then F3 rises and they need more LF eq. The trade off is that system with the higher F3 has more efficiency at F3 and above. The point is that either situation can be obtained in a small box with different drivers.

A key point is that the difference in equalization required for comparable response is based on where F3 is, and is required to provide the same excursion versus frequency versus cone area. Equalization boost comes at the cost in amplifier power, but it doesn't reduce the ability of a given cone area and linear excursion to provide clean bass.

On that we (and the laws of physics) agree. ;-)

It is all very well adding mass to lower Fs, but it also reduces efficiency. So you still need to add more power to get the same SPL as before you added the mass. More power = more heat = more chance for thermal compression whether you like it or not.

I know what it means and I never said Hoffman was related to equalisation, thermal compression or excursion. It stands to reason that if you apply EQ boost that will cause woofer excursion to increase. All things being equal between two identical woofers, one in a large box and one in a small box the amount of power will differ to reach a given SPL and more EQ is needed in the smaller box. Based on our exchanges you give me the impression that you don't think a small box is without compromise and I don't agree with that at all.

Actually, what I find funny is that our exchanges began because you have a problem with my signature. I think it's pretty obvious that displacement is the name of the game when discussing very low frequencies, but you don't seem to grasp that for some reason. No matter, you are welcome to dissect every line of text if it makes you feel better.

You've paraphrased my previous post pretty well! ;-)

You must have flunked the thermodynamics part of your engineering program. [-), More heat doesn't necessarily mean higher temperatures. If that were true, power plant cooling towers would all glow like the sun. In reality they don't even get hot enough to boil water. It is all about how well the heat can be dissipated. A high efficiency speaker or a tweeter with low mass has fewer opportunities to dissipate heat. Thermal compression in the real world is more of a problem for tweeters than woofers, for that reason. Maybe you've never held the cone/voice coil assembly for a high efficiency woofer and compared it to what you find in low efficiency woofers. Because I have friends who rebuild speakers as a business, I have.

Really? Your erroneous statements keep telling a different story.

A good example of a half-truth. Of course boosting bass causes more excursion of a woofer cone, but you have to consider what the excursion of the cone was before you equalized it. The reason they equalize most small woofers to obtain flat response is because without the eq, the bass response would be falling off. Response falling off means excursion falling off. There is a target for excursion versus frequency versus SPL for a given diaphragm area that all direct radiator speakers regardless of box size or efficiency have to follow. To reiterate - it is possible to achieve this target a number of different ways. But, in the end the same target must be met regardless of how the speaker is built internally.

The port gives you a back door, but the port sacrifices bass extension in order to do its job. Bandpass speakers also sacrifice response extension, this time at high frequencies, in order to provide their other advantages. The law of conservation of energy is very rigid but their are situations where you trade off what you don't care about to get what you do care about.


Wrong, and this may surprise you. It is possible to have a woofer that would give flat response in a small box without eq. If you put the same driver into a large box, then it will not have flat response. You then have to equalize it to get flat response out of it in the big box. It will also be a poor performer from the standpoint of efficiency in the large box. So, the claim that the smaller box always requires more equalization is false. I repeat, you can put a high mass speaker into a small box and obtain flat response without equalization. The origional Sunfire subwoofers were early examples of this approach, but I don't know if they went far enough to have truly flat response without equalization. They made some relatively new steps in that direction.

All speakers are a big ball of compromises. I'll bet that you have not built or helped build as many large box speakers as I have. My first serous subwoofer used a Earthquake (and by this I mean one that was actually used for that circa 70s movie) subwoofer My driver was rebuilt, so I don't know the precise parameters of the original driver. At any rate its measured T/S parameters said put it into an 18 cubic foot vented box (the size of a fridge) and it will be flat down to 20 Hz. Independent measurements in opens paces say that is what happened. It was very efficient and blew me out of my living room (for my needs) with a 15 wpc power amp. I also have years of experience with a close friend who is into whole-house subwoofers. His current system has 5 Ficar 18 inchers, each with a 1250 wpc power amp driving it. It too is very efficient but he uses it to do things like 120 SPL at 10 Hz which is someplace I never went with my 18 cubic foot monster. At any rate, I have woked hands on with voicing it and tuning it so I know what sort of eq it needs.


Wrong again. You chose something that has multiple reasonable meanings. You apparently don't want to take responsibility for your own choices and you aren't totally aware of the details of engineering subwoofers.

You must have reading comprehension problems because I've repeatedly said that large volume displacement is required for low frequency, high SPL response in this exchange of posts.

I've repeatedly pointed out that there is a fixed connection between displacement and LF response and SPL. You've been arguing that this is modified by the size of the box and that simply isn't true. If you don't get this by now then I should stop trying to talk to you because of your rather obvious learning-challenged status. ;-)

You got a lot to learn kid, starting with reading comprehension. I guess that is why you didn't learn how subwoofers actually work from your previous readings. A little hands-on construction would help you, as well.

Arny, a low q sub in a small box may have flatter response and require less equalization than if placed in a larger box, but more power will not be required in the larger box to reach a given excursion.

Every dynamic driver will suffer from thermal compression no matter how well it dissipates heat. In a smaller box where you need more power the reality is that thermal compression is more likely to occur.

A 5kHz order crossover sends 90% of the power to the woofer.



Why else, pray tell, would manufacturers such as Precision Devices even rate their woofers' power compression? You are not living in the real world.

I'm surprised I'm not even half-right here, just plain wrong. Just like that. The ego stroking from you is reaching critical mass now. Using a high mass woofer helps in a small box, but depending on the response you're after you still may need to apply eq at the low end. You need less power and eq in a larger box (for a given sized driver) and I was also right, but you must be right at all times. The fact that you can manipulate the variables to achieve a similar result in a smaller box does not change the fact that large boxes require less power and/or eq generally.

You can add as much mass to your driver as you want but then you'll be plagued by other issues. In any case, your small box/low Qts combination still needs more power but according to you that isn't an issue because thermal compression really only affects tweeters, not so much for woofers. Please. Don't talk nonsense Arny, you are not living in the real world - that's me preempting your next reply in case I don't bother replying again.

The Sunfire subwoofers produced enormous harmonic distortion and were not infrasonic monsters. They sounded "impressive" but that was due to the distortion, if anything. Impressive for their shoebox enclosure size? Sure. Still not that impressive.

You asked me in what context I used the signature and when I told you it was audio-related you disagreed, citing enclosure size as the source for disagreement. I was discussing swept displacement -ie moving air which is kind of the point. I think the fact you get so caught up by simple things like this explains a lot. You're a bit of a mental headcase, Arny. No humility, over-analysing everything to the nth degree, behaving as if you have a giant silver spoon stuck up his ass, trying to "act smart" and pretending that your answer is the only correct one etc etc - it's just pointless discussing anything with you.

Yes, I do have a lot to learn but not from you. If you can't grasp how high power in small boxes can't lead to thermal compression or even escalate the issue then who cares how knowledgeable you think you are. To be perfectly honest with you I'm not interested in your tactless approach to conversation either which is something you could learn to apply in future.

Thermal compression is a real issue for subwoofers, but let's sweep that under the rug because you are the authority on subwoofer design. If this is really just an ego stroking contest then you win first prize, but I am not interested.

Thermal compression is primarily caused by the voice coil heating up (IOW a voice coil temperature increase) which causes the voice coil's resistance to increase. Better dissipation of heat, less temperature increase. Less temperature increase, less increase in resistance of the voice coil. Less increase in voice coil resistance, less thermal compression.

Your claim that "Every dynamic driver will suffer from thermal compression no matter how well it dissipates heat." is hereby falsified.

If you can't accept this completely factual and logical argument, then there is no need for me to go any further.

No. With enough power you can cause any driver to suffer thermal compression no matter how well you claim it can dissipate that heat. What I am saying - what I've tried to get across and to no avail is that by virtue of using a smaller box you are forced to use more power to maintain that flat low frequency response and therefore thermal compression is more likely to occur. I am not saying it will occur - that obviously depends on the thermal properties of the driver and the listening levels in the room.

Infinite baffles are notorious for being extremely efficient with the drivers basically operating in free air - they require very little power and therefore the chances of thermal compression occurring are extremely low to nonexistent. What you are saying - rather implying is that thermal compression isn't even really an issue for woofers. There YOU would be incorrect.

Goodbye, Amir. ;-)

Translation - my position was without merit. Thank you for confirming what I already knew. Cheers. ; - )

That's not what Amir (amirm) is known for.

My understanding is that thermal compression can be a significant factor during sustained high power usage which occurs primarily in amplified large area venues like stadiums. The operative word(s) are sustained high power usage. As Arny has pointed jut this is a result of the voice coil heating up which changes the resistance. Whether this is a significant facor in home scenarios is highly debatable. After all, one must also contend with the inherent non-linearities in the driver's suspension. You've probably seen, goneten, compression tests performed on subs and the resultant graphs which givearough idea of the onset of compression. I think that one way a person might be able to test for themselves whether thermal compression is a significant facor is to measure the electrical resistance of the driver initially and then after playing for some time. If the change is large, then yes we have thermal compression that may have audible consequences. If small then not so much. Formulas for electrical resistance as a function of temperature can be found on the web for a variety of metals.

Btw, nice to see you goneten. FYI our mutual buddy appears he's going back to the slammer again.

Oh, I think so to some degree. Much of science is a stranger to him. When I made the reference I was thinking of the endless arguments after his position was already crushed by the facts.

But going with your statement as presented:

Begging the question...???

Correct in the sense that high performance audio systems such as those used in large venues may be run very close to their maximum power handling capacity much of the time during certain kinds of performances. However, power compression is not just a problem with large venues and heavy metal. Thermal compression relates to the the actual sustained power levels versus what the equipment being used can handle.

Everybody who provides equipment maintenance services to the general public sees speakers with fried voice coils. If the voice coil is fried today, there is an extremely good chance that it was first run at power levels that caused thermal compression.

As long as we avoid global generalizations, the debate need not exist because the stage gets set for thermal compression at least part of the time in home audio systems. For example, I've mentioned a friend's system that is composed of 4 18" Ficar woofers driven by 4 Behringer EP 2500 power amps. Most of the time this system runs so far from thermal compression that there is simply nothing to talk about. OTOH, with certain well known recordings that subwoofer afficianados like to listen to, the system power levels are within a few dB of clipping. BTW yes, the power amps are on a dedicated 30 amp 230 volt circuit so circuit breakers don't trip out. Is there some thermal compression at those time? I think so! That may be expected. However, the rest of the system may be signficaintly taxed at the same time.

For example I know for sure that when I push my old NHT 2.5i system to 110 dB peaks, significant voice coil heating can be felt with the fingers applied to the smaller drivers. Since those voice coils are some distance from where fingers can go from the front of the system, significant heating is probably taking place.

I know that I cooked the voice coils of one system I had with a acoustic feedback situation I stupidly created by putting a CD player in the same equipment cabinet as the speakers. If you cook a driver, it was probably driven hard enough for thermal compression for quite a little bit of time before that.

There are two classes of driver operation - the range where the driver is excursion limited and the range that is thermally limited. Many drivers are excursion-limited at low frequencies but at mid and high frequencies (whatever those might be for the type of driver whether subwoofer or tweeter) they are thermally limited. Suspension nonlinearity is only an issue in the range where the driver is excursion limited. Midranges and tweeters are generally only operated in the range where they are thermally limited.

You may be interested in knowing that there are production active speaker systems that continuously measure the DC resistance of the voice coils of their drivers and modify the electrical signals that they apply to their drivers when their voice coil resistance starts going up. Voice coil resistances can double during more-or-less normal use. A lot of technology has been poured into making speaker voice coils be far more thermally robust. That is one of the big differences between a modern speaker driver and its 1970s equivalent. When the patents run out this technology may be more broadly implemented. The technology for doing this was originally developed for small electrical motors. It is all about avoiding warranty costs.

Good to see you too! I haven't been keeping tabs on this but what on earth has he done now?

Remember all those RSL-II's and LS's he took money for? Caught up with him. Sentencing end ofthemonth.

There's a guy on AVS called Bossobass. He makes subs and at least on some of them takes approaches to cool the voicecoil. Might want to pm him.

With love and kisses.

Yep, I know Bossobass. Maybe he will chime in if I ask nicely.

My reply was solely on goneten's reply because he didn't seem to be familiar with amirm.

I fail to see your point here, we overspend on useless crap all the time. I am all for buying things we enjoy, but I'm not for being ripped off for a marginal (if that) difference in performance.

As much as the absurdity of high-end audio leaves me shaking my head sometimes ("audiophilia" is actually a religion, after all), I stop short of characterizing it as a "rip off." This is a luxury segment (I mean, nobody actually needs this stuff), and the market is rife with competitive choices, so it's hard to argue that anyone is being "ripped off." People of otherwise sound mind (there's a pun there ) indulge voluntarily and of free will.

Alas, let the buyer beware. If someone actually believes that a $7,000 interconnect or a $40,000 amplifier actually "sound better" (absent any form of objective analysis, which is a crime against audiophilia, of course), then, well, you know what they say about a fool and his money.

Well, in the context of this threads' subject matter, I see "ripped off" as referring to the industry creating a false "need" for expenditure. Like the " you should spend xx% of your audio budget on interconnects and cables" that is constantly spewed out. Might make sense to a point since it is a real cost when putting together a system, but once you get past a certain price point it certainly can't be considered anything but egregious to maintain that percentage.

Shouldn't the people who are ripped off being the ones that complain, and not the people who are not buying the message??? We seem to be giving ourselves ulcers on these forums worrying about what the other guy will spend. It is not like this is like sales tax and we too have to pay that percentage too. Everyone is able to walk away from that pitch.

But if you do want to worry about other people spending too much money, how about the millions of people lining up to upgrade to iPhone 5??? Shouldn't we shed a tear for them? 2 million units were sold in the first 24 hours. Non-subsided MSRP for iPhone 5 is $645. Assuming the cost to the carrier is $400, Apple collected revenues of $800 million dollars in the first 24 hours! With gross margins better than 50%, they netted $400 million in profit in one day. My calculator overflows when I try to add up the profits past the first day. And for what? A faster phone with more pixels? Folks couldn't run apps or make phone calls without that? They really needed more? They weren't past the point you mention? By that logic we should say Apple is ripping them all off too and brainwashing them to boot! Look at what these people are doing in addition coughing up the $200 with a 2 year commitment to get one of these phones:



Surely their souls need to be saved. No?

Just kidding. OK, just a little.

They are, Amir. Many of the people who suffered losses are among the large group of people who complain about the prevalence of fantastic claims and technical errors that are routinely made as part of the snake oil audio sales process.

Back in the day, I fell for the false claims made by TAS related to audio amplifiers sounding different. That amplifier was among the first two amplifiers to be ever ABXed.

You seem to think that the complaints are against the snake oil vendors because they are making too much money. In fact the larger amounts of money are as you observe, being made by people with valid and useful technology for sale.
Edited by arnyk - 9/20/12 at 5:41pm

It comes as no surprise that a high-end huckster has no idea what the word "rip-off" means.

The rip-off here isn't the price of the goods, or the profit margins. It's the deceptions you employ to sell the goods.

I don't even know where to start. Your comparison is wholly flawed.

Our perceptions are highly influenced by suggestion, bias, and expectation. These influences are so powerful that beliefs are formed based on their influence. These beliefs become reality for those with them. This reality may even be honestly shared by some "snake oil" companies, who, because of their convictions, contend that there must be qualities in their products that cannot be explained by science or measured using scientific methods. Of course you'd think there must be someone in those companies who knows otherwise, but who's to say?

In any event the real argument is one of reality. I personally have trouble with unsubstantiated reality and depend on science to prove cause and effect. But many do not, partly because of the effect of suggestion, bias and expectation. That creates polarized viewpoints that are often hard to bring together. Can we argue with someone's reality? One person may see his world as a wonderful place where lives are getting better, the environment is improving, governments are improving, and the entire quality of life is moving forward. Another sees life as degenerating, environments crashing, governments becoming more self-serving and with a hidden agenda, overall that we live in dark times. Both views are peoples reality.

If someone goes into an audio shop and the sales person says, "Listen to these cables, you'll hear (fill in the glorification here)", that's often what the customer hears. The cost of the product only substantiates the claim, and the published pseudo-science underscores it further. He buys the cables, takes them one, plunks them into his system and, fairly often, hears the same glorious improvements in his own system, at least for a while. If we apply science, we might think his perceptions are flawed, but to the happy customer they're his reality. How often a customer is happy with his new snake-oil purchase is probably related to how compelling the marketing, packaging, appearance, etc. Good snake-oil looks, feels, smells, tastes and yes, sounds good.

Not saying that purveying snake-oil products is right or justified, not at all. I debunk them personally at every opportunity. What I am saying is that sometimes, after listening to someone extoll the virtues of their new wires (or whatever), I just let it go. They may be wrong according to science or my opinion, but they're happy with their purchase. Who am I to take that away from them? When or if, someday, they come to me unhappy, I can put them on a different path. Or if they express doubt, we can discuss the alternative view. But if their opinion hasn't fully formed yet, stand back, here I go!

Audio companies, truthfully marketing products or not, are not selling a product, they are selling happiness. Happiness is subjective, vague, and often temporary. I'm happy with a product if it has real value that is verifiable. Others don't require that verification, but they are sometimes happier than I am!

I'm fairly sure this discussion centers around saving people from buying expensive products that don't do what they're supposed to. But enclosed within that discussion is the concept of "saving people from themselves". You can't do it. People have to save themselves by questioning their understanding, and seeking out knowledge, then re-forming opinion. The best you can do is open a new possibility for them. So long as companies are selling happiness, and happiness is subjective, you won't stop the snake-oil production. So long as people buy happiness in tune with their own reality, there will be a market for snake-oil. It might bother some of us, but that is only in our own reality.