Enclosure material - What is truely best?

[GTHill]

Yes, another thread on enclosure material.

What is the best material, not concerning weight or cost?

I auditioned a pair of Wilson Audio Alexandria X2's last night. When you knock on the cabinet is was very very inert. I know it's made of material X and material M.

So, what material is best?

Gene

 

[annunaki]

I would assume that Marlan is one of the best materials to use. B&W's Nautilus speakers are made from it as are the mid-range head shells in the 800 Series.

Other than that I don't think there is necessarily a "best" material. It just depends upon how the build process is done. Wmax (Chis) can weigh in a bit more in-depth as far as materials are concerned.

Design goals and implementation tend to be more paramount than materials used in some cases. Combining high quality materials with high quality design, implementation, and execution will result in a superb product.

 

[GTHill]

Would it be correct that the goal is a completely inert material? One that does not vibrate during operation?

Gene

P.S. I see you a lot on FChat. I have a 328 as another toy / hobby.

 

[annunaki]

I am not sure what FChat is. I do not frequent there. It could be another person with the same screen name.


A completely inert substance is recommended for any driver within its operating bandwidth. Cabinet colorations are so prevalent in many of today's speakers that some people actually (gasp) prefer them. It is difficult to find a single material which is completely resonance free throughout the entire operating bandwidth of a speaker.

A resonance fee system can be designed and built but with extremely complex construction and/or very exotic design/material. One does not want the enclosure to add anything to the sound. The only thing that should ever be in motion is the driver's moving parts themselves.

 

[GTHill]

Sorry, you have a very similar screen name as someone on Ferrari Chat. Plus, you say that you like F1 in your profile so I thought you were the same person.

I'll have to think about the material I want to use. I do a lot of work with MDF and should probably start there, but I want to do something not so normal.

Gene

 

[WmAx]

Yes, another thread on enclosure material.

What is the best material, not concerning weight or cost?

I auditioned a pair of Wilson Audio Alexandria X2's last night. When you knock on the cabinet is was very very inert. I know it's made of material X and material M.

So, what material is best?

Gene

For subwoofers, it is not an issue. You can easily use any conventional material, and with moderate bracing, push the resonant frequencies of the panels above the bandwidth of the subwoofer operation.

For the mid-range, though, this becomes a real issue. There is no way to use normal materials in a practical capacity and push the resonances of the panels over the bandwidth of the speaker system. It can be done - but it would require extraordinary building techniques.

So, normally, you will use a system that reduces the amplitude and converts the vibration to heat energy as efficiently as possible. The most practical method, using normal materials, that I have found in my testing: 0.75" high grade cabinet ply, then a constrained layer dampening adhered to this. Dynamat for example, in layers built up to 1/8" to 1/4". Then adhere solid oak, 1" to 1.5" to the Dynamat. Now install braces in every axis(X, Y, Z), and thave those braces spaced not more than 3" from another brace. This means a very dense bracing content in the cabinet. However, this method will result in extreme low level cabinet panel output.

Here is an example of a small bookshelf speaker using conventional MDF construction(Ascend CBM-170 SE), compared to an enclosure using the method described above. This measurement was taken with an acellerometer attached to the center of each bookshelf speaker's side wall, and both speakers driven to the same measured SPL:

The cabinet construction I specified has up to 30dB reduction in output compared to the standard cabinet.

-Chris

 

[GTHill]

For subwoofers, it is not an issue. You can easily use any conventional material, and with moderate bracing, push the resonant frequencies of the panels above the bandwidth of the subwoofer operation.

For the mid-range, though, this becomes a real issue. There is no way to use normal materials in a practical capacity and push the resonances of the panels over the bandwidth of the speaker system. It can be done - but it would require extraordinary building techniques.

So, normally, you will use a system that reduces the amplitude and converts the vibration to heat energy as efficiently as possible. The most practical method, using normal materials, that I have found in my testing: 0.75" high grade cabinet ply, then a constrained layer dampening adhered to this. Dynamat for example, in layers built up to 1/8" to 1/4". Then adhere solid oak, 1" to 1.5" to the Dynamat. Now install braces in every axis(X, Y, Z), and thave those braces spaced not more than 3" from another brace. This means a very dense bracing content in the cabinet. However, this method will result in extreme low level cabinet panel output.

Here is an example of a small bookshelf speaker using conventional MDF construction(Ascend CBM-170 SE), compared to an enclosure using the method described above. This measurement was taken with an acellerometer attached to the center of each bookshelf speaker's side wall, and both speakers driven to the same measured SPL:

The cabinet construction I specified has up to 30dB reduction in output compared to the standard cabinet.

-Chris

Chris,

Thank you for the helpful information. I have a few questions regarding your post:

However, this method will result in extreme low level cabinet panel output.

Low level cabinet panel output is desired, right?

This measurement was taken with an accelerometer attached to the center of each bookshelf speaker's side wall, and both speakers driven to the same measured

Do you know of or have documentation on how to perform this test? I would like to start experimenting with building techniques and materials and this seems like a great way to test cabinet rigidity.

The cabinet construction I specified has up to 30dB reduction in output compared to the standard cabinet.

I understand decibel loss, but in this case is the loss good? 30dB loss is of course a very significant number, but do we want that loss? Does this mean it is 30dB quieter than its MDF only counterpart?

Again, thanks for the very useful post!

Gene

 

[annunaki]

Chris,
I understand decibel loss, but in this case is the loss good? 30dB loss is of course a very significant number, but do we want that loss? Does this mean it is 30dB quieter than its MDF only counterpart?

Again, thanks for the very useful post!

Gene

GTHill,

That is correct. The cabinet itself is 30db quieter in terms of resonance. We definitely want that type of loss. What it means is that you are only going to hear the speakers themselves with little if any coloration from the cabinet at all.

This is what many of the "high end" manfacturers strive to achieve with their desins. Unfortunately many of them fail. One of the best executed designs available as far as neutrality is concerned is the B&W 802D. It is extremely linear with no cabinet coloration.

 

[GTHill]

GTHill,

That is correct. The cabinet itself is 30db quieter in terms of resonance. We definitely want that type of loss. What it means is that you are only going to hear the speakers themselves with little if any coloration from the cabinet at all.

This is what many of the "high end" manfacturers strive to achieve with their desins. Unfortunately many of them fail. One of the best executed designs available as far as neutrality is concerned is the B&W 802D. It is extremely linear with no cabinet coloration.

I have been reading a very interesting thread at DIYaudio. The cabinet neutrality is something that everyone agrees upon, but actual weight is something that seems to be debated.

Some are of the opinion that neutrality should be achieved with the least possible weight, and others seem to say that weight is not as important of a factor. I keep on talking about the Wilson Audio line and I love their sound. The Alexandria speakers are 700lbs each which would make me conclude that weight isn't a bad thing, given that Dave Wilson knows what he is doing.

I have been doing research on epoxy and concrete enclosures. I plan on starting with braced MDF, but I am intrigued by other materials for enclosures.

Thanks a lot for the response!

Gene

 

[annunaki]

I have been reading a very interesting thread at DIYaudio. The cabinet neutrality is something that everyone agrees upon, but actual weight is something that seems to be debated.

Some are of the opinion that neutrality should be achieved with the least possible weight, and others seem to say that weight is not as important of a factor. I keep on talking about the Wilson Audio line and I love their sound. The Alexandria speakers are 700lbs each which would make me conclude that weight isn't a bad thing, given that Dave Wilson knows what he is doing.

I have been doing research on epoxy and concrete enclosures. I plan on starting with braced MDF, but I am intrigued by other materials for enclosures.

Thanks a lot for the response!

Gene

For midrange units, it may be better suited to look into other materials like void free, cabinet grade plys. WmAx knows of some great absorbtion materials (compressed fiberglass, rockwool) that should be placed insider the cabinet regardless of the material you use for construction. Effectively decoupling the driver from the enclosure is also very effective at eliminating resonances.

Concrete still has resonances and is very difficult to work with. It too would still need to be braced. If this is going to be your first time (building speakers), use materials you can easily work with until you gain more experience.

 

[randyb]

I went to the DIY thread on speaker cabinet material and was a little surprised to read that Gedlee did not place as much importance on it as many and seemed to say that he has tried it all and came back to good old MDF.

 

[GTHill]

I went to the DIY thread on speaker cabinet material and was a little surprised to read that Gedlee did not place as much importance on it as many and seemed to say that he has tried it all and came back to good old MDF.

My understanding is the MDF properly braced isn't too bad. I think it just came down to cost for that project.

Gene

 

[jaxvon]

My understanding is the MDF properly braced isn't too bad. I think it just came down to cost for that project.

Gene

The lack of a more effective damping material with this style of construction is still a detriment. The added bracing with MDF will help push the main resonance higher in frequency, but it doesn't do too much with attenuating the vibration of the panels. This is the reason you see Chris recommending Dynamat or Peel 'n Seal, preferably in a constrained layer, to combat panel resonance.

 

[WmAx]

By the way, Chris (WmAx) has just shown me a midrange unit that has the most linear, horizontal off axis response I have ever seen. Dispersion on this unit is phenomenal as is the dynamic capability. Use with a good mid-bass and tweeter and solid construction technique and you could easily rival the Wilson Sophia's or exceed their performance. We're talking +/- 7db at 75 degrees from 167hz-11Khz!!!!!!

First off, that is a prototype system analysis - and that was meant to be kept in private PMs. I do not want prototype measurements shown in public forums unless there is a specific reason/purpose that I had to show it in public. This prototype does not even have fine correction filters in place - it is in a rough state of analysis/prototyping.

2nd, to compare this with the laughably inferior Wilsons must be a joke. No Wilson can compare to the off axis linearity I have targeted. Seriously, if the best I could do was build something comparable to a Wilson, I would give up the hobby.

Ans 3rd, the response chart you linked, shows a +/- 3dB deviation, maximum, from 500Hz-15000Hz, at 75 degrees. I am not sure where you go +/- 7db at 11kHz.

-Chris

 

[GTHill]

First off, that is a prototype system analysis - and that was meant to be kept in private PMs. I do not want prototype measurements shown in public forums unless there is a specific reason/purpose that I had to show it in public. This prototype does not even have fine correction filters in place - it is in a rough state of analysis/prototyping.

2nd, to compare this with the laughably inferior Wilsons must be a joke. No Wilson can compare to the off axis linearity I have targeted. Seriously, if the best I could do was build something comparable to a Wilson, I would give up the hobby.

Ans 3rd, the response chart you linked, shows a +/- 3dB deviation, maximum, from 500Hz-15000Hz, at 75 degrees. I am not sure where you go +/- 7db at 11kHz.

-Chris

I just looked as some performance measurements of some Wilson speakers and you are right! +/- 3dB is incredible! I'm not trying to ask about your secret sauce, but can cabinet design effect off axis response to that degree of difference? I'm of course just a newbie, but it seems like the driver itself is the main contributor of off axis sound. I'm sure I'm wrong, but I don't understand how that all works yet.

Hmm... maybe I need to attend a class...

Gene

 

[annunaki]

First off, that is a prototype system analysis - and that was meant to be kept in private PMs. I do not want prototype measurements shown in public forums unless there is a specific reason/purpose that I had to show it in public. This prototype does not even have fine correction filters in place - it is in a rough state of analysis/prototyping.

2nd, to compare this with the laughably inferior Wilsons must be a joke. No Wilson can compare to the off axis linearity I have targeted. Seriously, if the best I could do was build something comparable to a Wilson, I would give up the hobby.

Ans 3rd, the response chart you linked, shows a +/- 3dB deviation, maximum, from 500Hz-15000Hz, at 75 degrees. I am not sure where you go +/- 7db at 11kHz.

-Chris

Chris,

I apologize. The link is removed nor will it happen again without your explicit instruction.

 

[annunaki]

I just looked as some performance measurements of some Wilson speakers and you are right! +/- 3dB is incredible! I'm not trying to ask about your secret sauce, but can cabinet design effect off axis response to that degree of difference? I'm of course just a newbie, but it seems like the driver itself is the main contributor of off axis sound. I'm sure I'm wrong, but I don't understand how that all works yet.

Hmm... maybe I need to attend a class...

Gene

There are plenty of great books regarding DIY. Enclosures are just one part of it. One also has crossover design, driver selection and other things to worry about as well. My next DIY speakers (whenever I have time & funds to do them) will have fully active crossovers/filters.

Classes are not always the easiest to put together unless one is dedicating their time to it (which is usually a luxury to have extra ). Finding enough people (to attend) would also be potentially difficult. Starting out and making a couple mistakes along the way is the best way to learn in many cases. Paying for a class kind of defeats the true goal of the DIY enthusiast. High quality for a very minimal cost, and learning on your own.

Driver selection is always very important in any DIY or commercial application. The issue with commercial driver selection is cost and profitability. Enclosure design tends to be looked past in many instances, and/or more money being spent on asthetics as opposed to properly engineered cabinets.

 

[GTHill]

There are plenty of great books regarding DIY. Enclosures are just one part of it. One also has crossover design, driver selection and other things to worry about as well. My next DIY speakers (whenever I have time & funds to do them) will have fully active crossovers/filters.

Classes are not always the easiest to put together unless one is dedicating their time to it (which is usually a luxury to have extra ). Finding enough people (to attend) would also be potentially difficult. Starting out and making a couple mistakes along the way is the best way to learn in many cases. Paying for a class kind of defeats the true goal of the DIY enthusiast. High quality for a very minimal cost, and learning on your own.

Driver selection is always very important in any DIY or commercial application. The issue with commercial driver selection is cost and profitability. Enclosure design tends to be looked past in many instances, and/or more money being spent on asthetics as opposed to properly engineered cabinets.

I guess I'm just a bit frustrated because I can't find a good book for novices. I purchased the Loudspeaker Cookbook, but it is over my head for now. In technology, I always start with a Dummies book because they break down the basics very well. That is what I need. (Suggestions appreciated)

I'm not looking for a class to show me what is the best, but a class to explain the terminology, application of that terminology, and testing techniques would be excellent.

Thanks!

Gene

 

[annunaki]

I guess I'm just a bit frustrated because I can't find a good book for novices. I purchased the Loudspeaker Cookbook, but it is over my head for now. In technology, I always start with a Dummies book because they break down the basics very well. That is what I need. (Suggestions appreciated)

I'm not looking for a class to show me what is the best, but a class to explain the terminology, application of that terminology, and testing techniques would be excellent.

Thanks!

Gene

What terminology are you after???

I can try to find you some links.

 

[WmAx]

I went to the DIY thread on speaker cabinet material and was a little surprised to read that Gedlee did not place as much importance on it as many and seemed to say that he has tried it all and came back to good old MDF.

1. Ged Lee's design approach would never result in the most realistic sound for conventional 2.0 recording playback according to the perceptual works; he tries to target a controlled directivity system, which at best, could create a near field like experience in mid or far field use.

2. Resonances are substantially less audible in near field use or equivalent, with very little room reflection contribution occurring in ratio to the direct sound.

-Chris