Just some rambling, wanna read it?

[GranteedEV]

Subjectively speaking, do the following concepts have any merit or are they myths?

1) Sealed speakers acoustically sum to subwoofers easier than resonant alignments
2) Products intended for pro-sound "sound worse" than products intended for "Domestic" use.
3) Receiver level subwoofer crossovers are poor and we really need to implement a custom-tuned active crossover to the sub.

Based on my admittedly limited understanding and experience:

1) Many vented speakers tend to have tuning issues, especially many smaller speakers tuned to 77hz with a steep rolloff below there. Combined with the high pass filter slopes used you may be implementing a virtual brick wall rolloff below the tuning frequency. What are the audible consequences of this? Many subwoofers also fail to be flat up to the crossover frequency. While actual response is often dictated by room interaction, any subwoofer that's 3 to 6db down by the point of crossover, may create integration issues.

2) Pro Audio does have different priorities, but I think it's not quite the tradeoff of "Sound Quality for Loudness" that the Hi Fi industry might have you think. If anything, i'd say the main tradeoffs would be

1) extension vs sensitivity
2) many reflections vs attenuation of reflections (perhaps unintentional?)
3) aesthetics/WAF/CLD vs light weight/portability
4) optimized crossovers vs output/ruggedness optimized crossovers

But first you have to accept one thing - the obvious side effects of various high-diffraction horn lens' are as big a knock on many pro audio loudspeakers, as the obvious side effects of uncontrolled cone breakup in many so-called hi fi speakers. Both can be bad enough to bias you against specific design approaches even if a listener's issue is with a rectifiable issue.

So I'm lookin for a woofer that had reasonably high sensitivity. What I found was a big GAP. I looked at the popular ones and found some excellent looking drivers with 86 to 88db sensitivity, but then it seemed to shoot straight to 95+db sensitivity for Pro Audio drivers. That's not to say I didn't find drivers that fit my criteria, but it really got me thinking.

It seems to me that manufacturers really don't shoot for a sensitivity around 92-93db. PA companies want total speaker sensitivity close to 100db/2.83v/m / 16 ohm for the spec sheet and Hi Fi companies just want to get as far below 35hz as they possibly can, for the spec sheet, even if it means an 85db sensitive, 2.8 ohm speaker.

I mean the spec for the Revel Salon2, with THREE 8" woofers (about the cone surface area of a 14" woofer) states 86.4 db sensitivity. All it takes is an SPL calc to tell you you'd need about ~400w into a 4 ohm load just to hit 100db at the usual distance people sit in living rooms (10ft).

I find that odd, because Harman suggests using four subwoofers in a reference level room, not two or three tower speakers down to 20hz . Harman's own reference room uses JBL 6332 speakers with 93db/2.83v/m sensitivity + 4 subs. What that somewhat tells me is that Harman sees ~93db as a bit of a sweet spot for reference level performance in a reference room, but 20hz extension as a sweet spot for what "sells". Unfortunately there is a consequence to this. The Salon2's "made for subwoofers" little brother the Gem2 unfortunately does not have much of an edge in sensitivity - 86.4dB / 2.83v / m - despite losing two entire octaves of extension....

So which is it? The Gem2 or the 6332? I dunno.

The question shifts to: do hi fi optimized drivers just flat out sound better than "compromised" PA drivers. I don't know about that. It seems PA drivers actually can exhibit less measured distortion... companies like PHL, Acoustic Elegance, B&C, Beyma, JBL Pro, TAD, Radian, RLC, Eminence et al seem to have some excellent drivers.

So what's the problem with those excellent drivers? THEY ARE BIG! It seems to me that the thing that's missing, is acoustically small, dedicated midrange drivers with high sensitivity.

Here's one such example of what more companies probably ought to be making more of:

http://www.solen.ca/pdf/atc/sm150s.pdf

What we seem to have a surplus of is midwoofers - drivers designed for two-way loudspeakers to operate from probably 60hz on up to 3khz+

That's fine, but when you start with such midwoofers as the midrange in a 3-way, it's only logical for the woofer to be as or less sensitive. Therefore it only makes sense that a woofer extend the response further down.

The problem is that's totally useless for those of us running subs!!!

There are really so few dedicated midrange drivers. Pro Audio has excellent motors, but they chase output to the point of acoustically large drivers (For example, one interesting dedicated midrange, the acoustic elegance TD6M, looks sickeningly good in terms of optimized motor performance and bandwidth and all that good stuff. - but it's a 6" driver. do we really want a 6" driver playing up to 2khz+, especially if it will be mating to an acoustically small tweeter?). Home audio has excellent drivers, but they chase extension because 2-way, 2-driver speakers are what sells, even if it's likely to be lacking in dynamics in the average living room.

3) I don't think receiver level crossovers are inadequate. On paper they seem to lack the ability to make properly summing slopes, but the things we have to consider are the actual slopes used. My understanding of slopes is that THX certified and many other receivers will high pass the speakers at 12db/octave, and lowpass the subwoofer at 24db/octave.

So what's necessary is a sealed speaker that rolls off at 12db/octave, and a subwoofer that's reasonably flat up to 150hz or higher as a -3db point, give or take.

Receivers are good at aligning phase and timing information, so amplitude is the focus.

A speaker that will roll off 12db/octave (IE sealed) + a 12db/octave high pass filter, will give a 24db/octave rolloff, and a sub that is flat + 24db/octave low pass filter, should acoustically sum. These are active filters, so the transfer functions are independent of speaker impedance behavior.

The problem is that the typical speaker simply can't follow the above behaviour. If it's sealed and has the extension, then it probably has poor sensitivity. If it's sealed and has the sensitivity, then it probably doesn't dig low enough to mate to a subwoofer without localization.

You might even say that the need for big speakers like the JBL 6332 or Gedlee Summa -- is paramount if you want the right balance of sensitivity and output in blending to a subwoofer.

Modern autosetup software appears to work really well in integrating subwoofers into the room, assuming you're not running some convoluted setup where your speakers somehow double as your subwoofers and the receiver doesn't know that.

The problem we run into isn't likely the "integration" but rather the room! The room dominates much of what we hear in the bass, and consequently what the microphone doing the setup is "hearing".

Establishing all the above, it'd be really nice if we had more companies develop dedicated midrange drivers with high sensitivity, rather than repurpose midwoofers.

Thanks for wasting your time on this thread. I ain't payin ya back.

 

[AcuDefTechGuy]

My only experience with Pro speakers were the Yamaha CAB speakers. They were like $1,000 each and had dual 15" woofers. Compared to the much cheaper Infinity P362s in the same room, the P362s sound 100% better (side-by-side) to my ears.

I have never heard the JBL pro speakers, though. I should have gotten it instead of the Yamaha. I don't why I picked the Yamaha. Bad call on my part.:

And I'm thinking the Revel Gem2 will sound better than the DJBL 6332 just because.

 

[Pyrrho]

Subjectively speaking, do the following concepts have any merit or are they myths?

1) Sealed speakers acoustically sum to subwoofers easier than resonant alignments
2) Products intended for pro-sound "sound worse" than products intended for "Domestic" use.
3) Receiver level subwoofer crossovers are poor and we really need to implement a custom-tuned active crossover to the sub.

...

I think they are all myths.

With 1, if you use a crossover frequency sufficiently above the lowest frequency capabilities of the speaker, the rate of drop off after the -3dB point of the speaker will be irrelevant.

With 2, there may seem to be some merit to the idea, as some speakers are designed for different uses such that different requirements are necessary. Thus, for example, a speaker designed for a large auditorium must be able to play loud, and if one goes with a cheap one, that is likely its only virtue. But not all professional speakers are designed for such use; some are near field monitors for recording studios, and there the requirements are quite different.

I remember years ago listening to some Electro-Voice speakers designed for studio use, and compared them with similarly priced Genesis speakers for home use (in the same room, side by side). I preferred the sound of the Electro-Voice speakers. I also preferred their look, which was a no-nonsense black instead of a fake wood vinyl veneer. (I don't know why anyone would like a fake wood look, but evidently that is what manufacturers think people want in their homes.) I was planning on buying the Electro-Voice speakers after I saved up enough money for them, but ended up then deciding on some Heybrook HB2 (original model from the early 1980's, not the totally different speaker Heybrook later chose to call by the same name) speakers instead (which are made for home use). In part, the decision was due to getting a better price on the Heybrooks, which were store demos in perfect condition at about 50% off. If my memory is correct, the Heybrook speakers retailed for more than either of the other speakers, and although my impression is that they sounded better, I did not audition them side by side with the other two models of speakers, and so it was not even close to a proper test. Also, the Heybrooks have a gorgeous real wood veneer that wraps around the cabinet, so that the wood grain perfectly matches from side to top to side to bottom. I still have them, and plan on keeping them for life, though they are no longer my main speakers.

Anyway, I preferred the sound quality of the professional Electro-Voice speakers to the comparably priced Genesis home speakers. (Genesis speakers had a good reputation at that time; they were not at all bad sounding speakers, and were, in fact, the speakers I went to that store to audition, but the store was mainly a pro audio shop, so they had plenty of pro gear to audition.) And no, I do not remember the model numbers, as this was in the early 1980's, and I did not end up with either one.

Also, different home speakers are designed with different virtues and vices. Some are made to be able to play loud and give boomy bass for a cheap price, and those sound quite different from a speaker in which the goal is more refined sound but with sacrificing maximum volume and quantity of bass at that price. So in order to evaluate your claim, we need to figure out what it is that we want from the speaker, and then see what speaker matches up with those virtues best. And one will be able to find plenty of home and professional speakers that do not have whatever qualities it is that you want, and so it is going to make it a bit difficult to reasonably claim that one or the other general type is better. With home speakers, there are different design goals, and different compromises made by different companies to appeal to different people with different tastes and requirements. And the same is true of professional speakers.

As for 3, what is it that you want your crossover to do for you that a receiver cannot do? Your comments later on in your post about room acoustics are not going to be fixed by a crossover; those issues must be addressed in other ways, either by changing locations of subwoofers, by changing the acoustics of the room, or by equalization, none of which have anything to do with crossovers.

 

[JerryLove]

2) Products intended for pro-sound "sound worse" than products intended for "Domestic" use.

Although your examples are speakers: you don't specify that here.

Pro amps, mixers, crossovers, etc seem to perform as well as consumer gear; and XLR is a superior standard to RCA.

 

[Docks]

Heh, I've been pondering many of these questions.

The more I read the more a Behringer EP4000 with the DEQ2496 eq and DCX2496 (all XLR) fed into a well braced speaker seems to take the cake.
Ideally a computer could replace the deq and dcx and keep the phase linear too. Run a VST host into a Lynx soundcard (xlr out) applying eq as 24 and updb/octave filters and room eq.
In terms of sub you know the answer - Multiple Sealed LMS5400/Maelstrom fed with lots of power/headroom.