Broad discussion on speaker cabinet materials.

[PristineSound]

Want to start a thread to discuss all things related to speaker cabinet. If there is already one, please let me know, will ask Rick to merge.

There is a very recent podcast with the founder of Acora Acoustics, hosted by Soundstage, see link below. In this podcast, Acora owner, Valerio talks extensively about using stone to make speaker cabinets, he does seem very knowledgeable about stones and the use of it in speaker cabinets, though he didn't at all talk about anything else about speaker design, though he did say he measures his speakers at the NRCC.

Anyway, he claims that stone is an excellent material for speaker cabinets due to the properties of stone, presumably the inert nature of it. On his website, he claims that it's essentially the best material (with some caveats).

So to start off this thread: we have the typical HDF and MDF, they are cheap, easy to work with and does a relatively good job in terms of stiffness and resonance control, then you have non commodity materials like aluminum, carbon fiber, fiber glass, one manufacturer even use bamboo. What is the best material for speaker cabinets irrespective of cost and what is the best for cost : performance? I know the utilitarians here will be insulted about anything exotic and will say, it all depends on the design and/or construction blah, blah, blah. The question is not about design nor implement, the question is about the material properties.

SoundStage! Audiophile Podcast - Rock-Solid Sound: Acora Acoustics’ Luxury Stone Speakers

Listen to SoundStage! Audiophile Podcast - Rock-Solid Sound: Acora Acoustics’ Luxury Stone Speakers by SoundStage! | The SoundStage! Network | Schneider Publishing Inc. on Podcast Addict. This week, SoundStage! Audiophile Podcast host Jorden Guth is joined by Valerio Cora, founder and CEO of...

podcastaddict.com

 

[dfuller]

I would take the Acora guy with a grain of salt.

One of his speakers was measured by JA at Stereophile and it wasn't particularly pretty:

Anyway, in most respects Aluminum is the best commonly used option. It's much stiffer per thickness than MDF (which means you can have a significantly higher internal volume to external volume ratio), it can be cast into any desired shape (including ones that would be hard or costly to machine), and can have cast-in bracing to keep its resonances to a minimum. Plus, it's a material that can be effectively endlessly recycled, and can sink heat from internal amplifiers effectively. Genelec uses it so extensively for a reason.

 

[ZolaIII]

Torminalis - Wikipedia

en.m.wikipedia.org

 

[SSS]

Every material has good and bad properties. Therefore there is no "best" material for loudspeaker cabinets indpendent of type and construction.
But I am curious what the crowd will select.

 

[DVDdoug]

I believe most pro monitors are wood (MDF or furniture grade plywood?). Stiffness is the most important mechanical requirement and that can be achieved with bracing if the material isn't naturally stiff and non-resonant enough.

As long as the speaker is half-way decent, most resonances are more-related to internal dimensions/reflections. Or resonances may come from the drivers or from poor ported designs.

Plastics are often used in pro portable PA speakers to make them lightweight and physically tough.

With plastics or other moldable/shapable materials it's easier to avoid sharp edges and to make waveguides or special-shaped ports, etc.

 

[MAB]

I know the utilitarians here will be insulted about anything exotic and will say, it all depends on the design and/or construction blah, blah, blah. The question is not about design nor implement, the question is about the material properties.

Odd restriction. What's the purpose?
For example, Beryllium is an interesting material, somewhat exotic, has had it's individual properties discussed over and over here, most often without any acknowledgement of what it does when designed and constructed into a speaker (blah blah blah ). It would certainly be nice to have a thread where we actually talk about how these exotic and mundane materials are implemented in a speaker, and what the tradeoffs are. We do have loudspeaker and driver designers at ASR, so such a restriction seems very limiting and even counterproductive. Otherwise it's a material-trivia thread, which will likely turn into a material envy thread.

 

[PristineSound]

I would take the Acora guy with a grain of salt.

One of his speakers was measured by JA at Stereophile and it wasn't particularly pretty:

I actually met that guy at Capital Audio Fest last year. I asked him few surface level technical questions about his speakers, he came across as he didn't want to be bothered with me, either he is not liking where the conversation is going or because I don't fit the mold of a stereotypical audiophile (50+ men).

Anyway, his answers were very brief and generic, which made me believe he had no clue with speaker design. But in this podcast, I was quite surprised how knowledgeable he is with using stone (though no fact checking performed on him) and he measures at the NRCC, so now I am having second guess if he is legit or not.

 

[PristineSound]

Odd restriction. What's the purpose?
For example, Beryllium is an interesting material, somewhat exotic, has had it's individual properties discussed over and over here, most often without any acknowledgement of what it does when designed and constructed into a speaker (blah blah blah ). It would certainly be nice to have a thread where we actually talk about how these exotic and mundane materials are implemented in a speaker, and what the tradeoffs are. We do have loudspeaker and driver designers at ASR, so such a restriction seems very limiting and even counterproductive. Otherwise it's a material-trivia thread, which will likely turn into a material envy thread.

You are of course free to talk about cabinet design as my intent for this thread is all things speaker cabinets, but specific to replying to my starting OP, I am asking about cabinet materials. I'm not looking for others to come in and drown out the OP question about materials because some people are just grumpy about having to pay a premium for exotic materials.

 

[bmc0]

There is no "best" material; it depends on the application, even without considering costs. Additionally, as long as all cabinet resonances can be pushed well below audibility, there is no further advantage to be gained. Measurements of well-designed loudspeakers show that this can be achieved with a number of different materials: MDF, plywood, aluminum, reinforced plastic, etc.

You dismiss the "design and/or construction" details, but this is clearly the most important consideration. Any material which can be used to make a good cabinet can also be used to make a bad one.

 

[Chr1]

Is it not the case that if weight is not an issue, very dense, stiff materials are best?
However weight (and cost) are often the limiting factors.

 

[kemmler3D]

What you want from a cabinet is stiffness as well as damping if you can get it. To me this says that an ideal cabinet probably isn't made from a single material, but a composite of layers... stiffness, absorption, and damping are all desirable, but you have to trade those off for different materials. Traditionally builders going balls-out use concrete, sand layers, aluminum, and elastic damping layers of various kinds. If you were truly sparing no expense and going completely crazy (crazier than machining from stone) you might use multiple layers of tungsten with damping layers in between.

 

[Chr1]

Seems to me that concrete is probably a pretty good budget option.

Again if weight is not an issue.

Saying that, if I had the place/budget I'd probably go all in, and go for soffit mounting in concrete.
With big Genelecs. Bolted in.
(ie Coupled to/Part of the wall.)

 

[ckernel8]

What about Formi? It's an isotropic composite material made from a plastic of some kind (I think generally polypropylene, but they also make 3D printer filaments that use PLA), but also at least 20-50% wood fibers (the 3D print filaments are restricted to 20% I believe). B&W used it to great effect (imo) in the Formation Duo speakers (now defunct).

Seems like it could be nearly ideal for commercial speaker making? Especially since it lifts any real limitations on shape.

 

[thewas]

Here some analysis and even sound samples of typical cabinet materials are shown:

HAUPT

DUO-DXT

HiFi-Selbstbau - Das DIY Online Magazin für hochwertiges HiFi

www.hifi-selbstbau.de

As said from others already, it is a typical engineering exercise, namely finding a great compromise for the individual requirement and priorities list and thus not single answers exist.

 

[Doenerkunde]

Fink Team, led by german speaker development icon Karl Heinz Fink, seems to be among the industry leaders when it comes to evidence based speaker cabinets.

They employ:
- Constrained layer damping
- Point to point bracing
- Internal Helmholtz resonators

Q Acoustics Concept 500 developed by Fink:

Source: https://www.stereophile.com/content/q-acoustics-concept-50-loudspeaker-measurements

Fink Team Kim:

 

[MAB]

Fink Team, lead by german speaker development icon Karl Heinz Fink, seems to be among the evidence based industry leaders when it comes to speaker cabinets.

They employ:
- Constrained layer damping
- Point to point bracing
- Internal Helmholtz resonators

Q Acoustics Concept 50 developed by Fink:
View attachment 473090

View attachment 473093
Source: https://www.stereophile.com/content/q-acoustics-concept-50-loudspeaker-measurements

Fink Team Kim:
View attachment 473091

View attachment 473094

I'm intrigued by the Helmholtz resonators. I've measured interior cabinet resonances in tall speakers, Erin has pointed them out as well as seen in impedance traces in some of his reviews. I've wondered if a resonator could mitigate some of these.

 

[Doenerkunde]

I'm intrigued by the Helmholtz resonators. I've measured interior cabinet resonances in tall speakers, Erin has pointed them out as well as seen in impedance traces in some of his reviews. I've wondered if a resonator could mitigate some of these.

In this (German) talk Karl Heinz Fink demonstrates the effects of the Helmholtz resonators in the Fink Kim speakers (starts around 26 minutes):

250hz standing wave between top and bottom before...

...and after:

623hz standing wave between front and back before...

...and after:

From the Q Acoustics Concept 500 White Paper:

 

[thewas]

The standing waves are an issue at most floorstanders due to their height dimension, except a Helmholtz resonator it can be reduced by clever placement of the woofers, see page 8 of the KEF Q Meta white paper https://www.audiosciencereview.com/forum/index.php?threads/kef-q-series-with-mat-whitepaper.57911/

 

[RickS]

@ctrl had suggested something like the Fink HPE to me previously. If you block a vent cleanly on the outer end, could have a comparable effect. To deal with lower frequencies required a good size tube. For a floor stander might makes sense as may have volume to spare to implement. Would only make sense in a smaller speaker if the resonance is higher (and then damping material is often effective).

 

[DVDdoug]

My assumption is that nothing showing-up in Amir's speaker measurements is related to cabinet material.

...I've mostly used MDF but with at-least one of my (big) speakers I used plywood for the front & back panels because it was getting VERY heavy. (It probably didn't make much difference with just the front & back.)