Bill Fitzmaurice

No. Egg crate foam gets its name, and look, from real egg crates, which once were used to line the walls of studios, not to absorb sound waves but to diffuse them. When acoustical foam was invented the look was copied, but ill-advisedly. Foam can't diffuse sound waves, as that requires that they reflect off the foam, which they do not. In terms of absorption flat foam works better, as that is determined by the actual amount of foam. The air contained in the spaces between the egg crate foam dimples doesn't do anything. That may be of significance if you're building a boat, but it matters not a whit with a speaker. Baltic (also known as Finnish or Russian) Birch is the preferred material for speakers .

It needs damping because if it's not damped waves from the back of the cone reflect off the panels back to the cone, meeting it at various angles of phase, causing peaks and valleys in the speaker response. That's the case with all speakers. This isn't a debatable topic, it's Acoustical Engineering 101, first semester. Un-braced 15mm plywood is insufficient to make the cabinet panels inert. The only difference between Marine plywood and standard grade is the use of waterproof glue. What does matter is the number of plies, which is responsible for stiffness. A single brace connecting the middle of two opposing panels gives the same result as doubling the panel thickness. That's Civil Engineering 101, first semester. Giving the cab designer the benefit of the doubt I'll venture he may have studied acoustical and civil engineering and specified how to correctly build the cab, but the bean counter who over-ruled him in favor of saving a few quid certainly did not.

In WinISD 0.7 the effect of both lining and stuffing is seen when you alter Qa from the default value 100, a bare cab, to 50 for a lined cab, 10 for a stuffed cab and 5 for stuffed and compressed. However, as is the case with all WinISD modeling, the results are only fully accurate within the range of pure pistonic function, to roughly 2 octaves above the cab F3. Stuffing, especially when compressed, lowers the cab Q, so the effect on the low frequency response will be seen in the charts. Lining mainly affects the midrange, so it's primary effect is not reflected in the charts. It is seen in measured charts as a significant smoothing of midrange response.

It does. Nearly all speakers do. There's the right way to build a cab, and there's the cheap way. BF does it the right way.

It doesn't need loads of foam, but it should be fully lined, and since it wasn't then yes, they cocked up the design. The bracing is sparse as well.

Yorkville/Traynor is a Canadian company that's been around since the 1960s. Back then they were one of the brands to consider if you couldn't afford Fender or Ampeg. The BC line is long discontinued. The Eminence drivers they used were no more 'custom' than anyone's, which is to say not much different, if at all, than off the shelf. FWIW anyone can get a 'custom' Eminence, you just need to buy at least 50 of them.

Probably not, as most speakers are limited in their output by the size of the cabinet and the excursion limit of the driver, not the driver thermal power limit. To get a worthwhile increase you need to double the driver excursion and increase power by a factor of four to make use of that excursion.

The position of the ports doesn't matter, but the lack of ducts does. Unless the cab is gigantic ducts are required to lower the tuning of the cab to where it must be for proper operation.

Those aren't driver specs. This links to an example of what a spec sheet looks like: http://www.eminence.com/pdf/Kappalite_3015.pdf

Knowing the driver specs and cab particulars the science would reveal exactly what both of those set ups would sound like.

That tells me the drivers used probably weren't well suited for a ported cab. Some drivers can be used either way, but most are optimized for either one or the other. You probably could have arrived at the same result with EQ, but it's likely the level of EQ sophistication required wouldn't be found in a typical bass amp. The one thing about sealed that ported can't duplicate is the low frequency compression that results when drivers in a sealed cab reach xmax, which may or may not be desirable based on personal preference.

Can you read SPL charts? This compares response of a Simplexx 15 sealed and ported with the Eminence BP1525 driver. Note that if you want to get the same response from the ported as sealed you can, just back off on the bass EQ, which also reduces power draw from the amp. The chart only extends to 200Hz because above that they're identical. The ported advantage in low frequency sensitivity is there, but it's not huge. Now consider this, a maximum SPL chart, which takes into account the response, the driver thermal power handling and driver excursion limit: The sealed cab doesn't even come close down low. The difference is attributable not only to the output added by the port but also the reduction in cone excursion that porting results in, and it's excursion that primarily limits how loud a cab will go below 70Hz or so, not the thermal power capacity. You can get a ported cab to sound like a sealed cab, but you can't get a sealed cab to deliver the low end output of a ported cab. There will be those who say otherwise, but in controlled double blind listening tests when EQ'd for the same response listeners are unable to tell the tone of one from the other.

There's nothing magical about getting that tone. Light gauge round wounds, JBass pickups and a pick, along with lots of practice. A neck through bass with hardwood body helps, but it's not an absolute necessity.

The same percentage who know what it means.

They also will have completely different tonal characteristics. It would be nice if they posted response charts, but at least they're one of the perhaps 5% of manufacturers who provide displacement. I guess response charts will have to wait until the next century.

Internal dimensions are a must.

Assuming that the 237cc displacement of the first and 496cc displacement of the second does in fact refer to woofer Vd (odd they can't find anyone to translate their spec explanation into English) the second would equal two of the first in maximum output capability. I'd bet pence to pounds that the first is loaded with an Eminence Beta 12, the second with an Eminence 3012LF.

Most manufacturers are quite loathe to reveal any information about the drivers they use. The usual reason given is that they don't want people reverse engineering their cabs. That's silly, as any decent amateur engineer can borrow a cab, measure the driver specs and get the cab dimensions in a matter of a couple of hours. The real reason is that they don't want users to know how inexpensive the drivers are that they use, and don't want people buying replacement drivers from alternate sources for much less than what they sell them for. Your best bet is to post the cab dimensions and you can be given a few drivers that are compatible, but they probably won't sound the same as the stock drivers.

The driver T/S specs need to be matched to the cab, via speaker modeling software. The driver thermal rating is one of the least important specs, as it has no relationship with either frequency response, sensitivity or maximum output. Perhaps most important when contemplating a swap is that if you don't model the existing drivers for low frequency results and have a data sheet SPL chart for the midrange and high frequency results you have no way of knowing if a different driver would be an improvement, or if it is even as good as what you have.

Cab B will be louder, by about 7.5dB. In fact, Cab B will be more than the equal of a pair of cab A. This assumes that you're actually driving both cabs to their full excursion. If their sensitivities and frequency response are similar and both are driven with the same voltage swing they'll be equally loud. What gives Cab B the ability to go louder is that it can take over twice the voltage swing, which is more than four times the power, as Cab A. True, because speaker diameter is not a measurement of displacement. But displacement would not be stated as 200cm anyway. Cone area (Sd) is stated as square cm, displacement (Vd) is stated as cubic cm. As the OP specifically asked about displacement I assume that's what he means. The main issue with trying to compare displacement of different cabs is that almost every cab manufacturer won't reveal it. One can rightfully assume that those very few who do publish displacement specs don't feel the need to hide it.

I was prepared to let this thread go, but ...I never said rubbish, or that they won't work. I did point out the shortcomings of systems of this type from a purely technical standpoint. If the subs can be easily remotely placed It would be most helpful if the marketing material made note of that, and the owner's manual as well. It would be even better if the manual pointed out the advantages of sub wall placement and clustering. But every picture in the advertising, the manual, and your own demonstration shows the mains atop the subs, the subs split and away from the wall. As for the percentage of PA operators here who were previously aware that subs should be wall loaded and clustered whenever possible, and what the Power Alley is, do a poll. I venture it would be a very small percentage, because by no means are these technical aspects intuitively obvious. Knowing how to correctly do PA must be learned. It is most difficult to learn something that is not being taught. It certainly isn't being taught by the PA industry in general, and as the marketing and manuals are presently written, not by Markaudio. IMHO that makes Markaudio part of the problem. You now have the opportunity to make it part of the solution. Or continue to shoot at the messenger while ignoring the validity of the message.

If the forum management thinks that what I do for a living renders me incapable of offering unbiased technical advice all they have to do is say so and I will have made my last post here.

I do not manufacture or sell speakers, or represent in any way any entity that does. I'm an acoustical engineer, so any comments I may make come purely from an engineering standpoint. I don't have a dog in this fight, but that doesn't mean I can't point out if one or more of them have a decided limp.

The angling of the drivers doesn't make it 'not... a true array'. It's actually an old concept, intended to broaden high frequency dispersion that otherwise beams due to using HF drivers that are too large. It's not as effective as using a two-way line, with midbass drivers large enough to comfortably reach 100Hz or lower, and tweeters to prevent high frequency beaming. Bose used that configuration as a cost cutting measure, allowing use of the same drivers they employ in many of their home audio speakers. Bose double cubes allow aiming of the drivers in two directions for the same reason, to broaden HF dispersion beyond the limitations of the driver. The Bose array is for all intents and purposes a stack of those double cubes.

The comment about proper sub placement doesn't refer to compact arrays in particular, it refers to PA systems in general. Ask any PA operator who splits their subs and puts them under the mains why they do it that way. They'll be hard pressed to come up with an answer, other than 'that's the way everyone does it', 'that's the way I've always done it", or 'that's the only way I know how to do it'. Doing a PA setup the right way is no more difficult than doing it the wrong way, if you know what the right way is. The PA industry in general has not made any attempt at providing the average user that information. It could do far worse than to emulate the efforts in consumer education that Barefaced has in the electric bass cab genre.