Speaker cabinets: How important is inert

First let's assume that the best school of thought is for speaker cabinets to have zero characteristics of their own, i.e it's completely silent.

A lot of the premium speakers like Rockport, Magico, YG, Kharma, Wilson all boast custom cabinets which are supposed to be "dead," which will let the drivers do their jobs without having the cabinets interefere. There are also premium speakers that uses braced MDF like TAD, Tidal, the lower Rockport lines, Avalons, etc which are supposed to be almost as good.

I'm not in the market for speakers, but everytime I look and listen to different speakers, I almost always prefer the big heavy duty cabinet speakers, and not the slim shaped refined looking speakers.

So my question is - do these custom epoxy or sandwiched or aluminum or whatever cabinets make a HUGE difference over plain MDF or braced MDF, or is it just marginal? How much of the secret to a good sounding speaker is in the cabinet engineering versus the drivers?
You can't separate it; good drivers in a bad cabinet sound bad; bad drivers in a good cabinet sound bad. In a speaker, even more than other components, execution of the total package is critical. Most of my speakers use the BBC "Thinwall" design where a thin outer cabinet is carefully damped internally. My Gamut L5s have a very heavily braced narrow cabinet. The Apogees have no cabinet. All are excellent speakers. Deader is obviously better but that alone will not tell the whole story; if money is no object then high tech materials should have advantages but a more conventional speaker still might sound better to you. Speaker prices are becoming totally unrealistic in terms of what most of us can afford but conventional cheaper speakers still give high quality sound. Sometimes I think the exotic materials are used at least partly to justify the high costs. Asking whether the cabinet or drivers is more important is like asking if the engine or chassis is more important in a race car, if you don't have both you wont go anywhere.
Cabinet materials do have an effect on overall sound quality. Small transducers can also vibrate on baffles smearing image. Cabinet surfaces also vibrate this can cause added colorations. For me Baltic birch ply is one of the better materials for quality loudspeaker cabinets. I have used many other types I tend to go with baltic plys braced doubled baffles etc.
Well designed cabinets are certainly a major factor in a speaker's overall performance, but a very "dead" cabinet is not the only effective means of producing a good speaker. Two examples of the alternate route would be the Harbeth speakers and Audio Note speakers.
With Traditional drivers, The lower the resonance of the cabinet materials used, the less you hear the cabinets in your music. Typically this is achieved by useing very dense materials. Bracings purpose is to reduce cabinet resonance. If you can come up with a space age material, that will not flex(flexing would be a problem) or give and is "DEAD" you should have a winner. Until then, we do what we do. Tim
"Two examples of the alternate route would be the Harbeth speakers and Audio Note speakers. "

What route DOES Audio Note (UK?) take? They look like a Radio Shack project speaker, and imo, don't sound much better than my first pair of SoundDesigns in 1977.
With speaker drivers housed in cabinets, the fundamental issue is what does one do with the rear wave from the back side of a driver? That wave is just as strong as the front one. That energy does not magically go away, so it must be taken into account.

A dense cabinet in and of itself will only trap that energy inside the speaker and it will reemerge through the speaker cone as delayed sound. This smears the sound.

Ports and other devices work only in a lower range of frequencies. Padding and stuffing only work well at upper frequencies. However, if one is not careful, not getting rid of this rear driver energy can easily create issues in the lower midrange where our hearing is particularly sensitive.

Harbeth & classic Spendors use the BBC damped thin wall design. Other speakers use other approaches, but by itself, a cabinet that is simply dense doesn't address the issue.

Like any engineering problem, it requires a system approach to address the problem.
"but by itself, a cabinet that is simply dense doesn't address the issue"

Actually it does address the issue. Not 100% But generally. A speaker has a specification called vas, this is the Equivelant air volume or the volume of air that has the same compliance as the speakers suspension.
The suspension i.e. voice coil assembly, spider and even cone material affects how the driver reacts to the air behind that driver. That is why In a sealed box a drivers frequency curve will develope a peak as you shrink the box size or develope a dip as you increase the box size. This happens on any traditional cone type speaker regardless of size. Cone breakup because of that back wave is what causes the smearing effect that you speak of. The right cone material will not have that smearing effect of back wave. In general, cabinet stuffing has three purposes, to break up standing wave, to cut resonance and to trick a driver that it is in a larger box, by changing the time that it takes air to travel within the speaker box.
Given there are hundreds and hundreds of speakers on the market, there are obviously a variety of opinions as to what is the best approach to speaker design.

The Vas parameter is used in determining the bass performance of the speaker. One can model a number of different box volumes and see a significant change in performance under 100 Hz but virtually no impact on the performance above. If you reread what I wrote above, it is this range above the bass where it is often difficult to control the back wave re-radiating through the driver cone material.

Of course, cone material can be selected that is better in this one area, but that cone material may represent a loss of performance in other areas. Almost all engineering efforts represent finding those compromises that result in the best balance in the opinion of the designer. And, as is routinely demonstrated on this forum, there a considerable range of variety in those opinions. ;-)
"One can model a number of different box volumes and see a significant change in performance under 100 Hz but virtually no impact on the performance above"

Hi Mlsstl,
I was only addressing cone speakers. VAS affects all cone speakers in a box regardless of size. It is just as important to have your midrange in the correct box size as the bass driver. Its final Qts figure will relate to a hump, flat or a dip in its frequency. If you develope a hump, it would easily portray a coloration or "smear" in frequency. As far as controlling back wave in the cone material, I was specifically speaking of mid range drivers. Back in the old days of paper cones, we treated them with Latex to stop cone break up, Later came poly, kevlar, carbon fiber, aluminum,....etc etc etc.
The latex helped control breakup. The more dense materials normally were not as effected by backwave coloration because of the stiff cone material. What I am saying is the cone material and box material are not intertwined. They both matter greatly, but independently of each other. Sorry, no disrespect intended.
Back to Enzo618. Any material that is rigid and dead would be great. Normally thinner materials require a bit more bracing, but can work. You've probably seen concrete enclosures. I've not experimented with alot of materials, I've used some fiberglass, but it had to be thick and re-damped, I like your epoxy sandwich idea.... but in the long run, a proberly damped inert material that has the proper air space will do a reasonable job. Some may be slightly better than another, but the standard braced MDF is hard to beat.... Dollar for dollar, I'm not sure that you can.
No disrespect taken (but then I've never worried too much about that issue one way or the other...)
I'm with you on that brother
I use British speakers mostly that figure cabinet resonance into their design,from my understanding.Speakers that have so called dead cabinets,aren't a guarantee for the best sound.The drivers themselves are a primitive way of making music,but that's what seems to work the best.Even 70-90 years later.A lot of musical instruments make their sound by cabin resonance. I go by what my ears like,not what electronic measuring devices say I'm supposed to like.A technically good speaker usually sounds poor.Is thick car paint fantastic sounding?If they were that dead,we could put them in a corner,or against a wall.In the 70s or 80s,a dealer had a pair of speakers that measured the best at the time. He asked me what I thought of them,I listened awhile and said ok to be polite.He asked if I would by them,I said no.He said that's why they're close to the door,to get rid of them as quick as possible.Go by your ears,and forget the rest.You must like,and enjoy them.This is just my two cents.
And then there are free resonance, that's controlled resonance speakers by Michael Green. Anyone listened to his Chameleons? I don't have Chameleons but I have his old Revolution 80i model. Very natural sound. Michael has a great ear. But I would not choose his speakers for big orchestra music especially if price is no object. Or probably for very big rooms, and I mean big. Also, ideally these speakers require iron-fist but gentle and refined amplifier, let's say like Rowland or Gryphon.
my large monitors have granite sides - I think it really helps - no resonance - nice and clean/clear sound.