[James Romeyn]

Stereophile about a year ago had an Industry Update article in which was described an intersting new laminated speaker panel material developed by two long-respected Euro speaker designers.

First the article described that even w/ all our current experience & advanced scientific measurement systems there is still no unanimity on the best material.  History was covered: In the 40s-50s teak & old growth north Russian ply were favorites.  The Germans apparently developed particle board in the 40s & it was liked for its lower cost & damping quality.  But PB is inconsistent & chips when rabbitted for flush-mounting.  When it arrived later MDF was liked for its consistency & no chipping when rabbitted.  There's of course HDF now too. 

But listening tests nowadays do not consistenly favor MDF/HDF, which may damp less well vs. particle board w/ its irregular sized chips.  Also I'm thinking that MDF's higher mass increases its Q & moves the resonance point to a higher frequency, both of which are bad.       

Anyhows, the Brits developed two laminates more recently: 50% particle board under 50% Baltic Birch ply (chips when rabitted) or 50% MDF over 50% BB ply.  The ply is liked for its stiffness, PB or MDF for damping.   

I'm favoring the two sides, top & bottom being 50% PB under 50% BB ply.  Front/back will be 1" solid MDF for easy rabbitting & also because that's what was employed by the designer of my favorite standmount speakers. 

Comments sought.  Facilitator please move this to another circle if that would be appropriate.  I was rather surprised no one at DIY had tried the above-described laminate; it seems to make a lot of sense.   

     

[mcgsxr]

I have used 3/4 mdf and 3/4 baltic birch ply laminated together for the front baffle of a sub in the past.

My best friend laminated 1/2 mdf, and 1/2 solid oak, for his speakers.

For my little KIT41 speakers, I used 3/4 mdf for top, bottom and sides, and 3/4 baltic birch ply for the baffle and rear panels.

[James Romeyn]

I will edit the post: should read 50%/50% rather than 1/2-1/2, which could easily mean inches.  Sorry!  Total panel thickness will be 1.25", again copying the speaker being cloned.  In this case that will be 5/8" PB under 5/8" BB ply. 

Have you guys ever radiused the corners on ply?  In my case the BB ply will be a high quality (5x5 panels, not 4x8) & plies will be fine.  Just wondering if someone could post a picture what the edges look like when radiused & clearcoated. 

Only the 5/8" thickness of the BB ply will be radiused; the 5/8" PB underneath will remain hidden under the dado.  Is a 5/8" radius large enough to minimize diffraction on a 2-way mid-size monitor?   

TIA.     

[mcgsxr]

There are examples of the effect in this thread - http://techtalk.parts-express.com/showthread.php?t=209719

I have never done it, because I knew I could easily create the roundover with mdf, so I used the material I was more comfortable with.

I would think that you will need to take a couple of passes, to create the roundover, to avoid tearouts etc.  I have been able to aggressively roundover mdf in a single pass, but I bought a cheap router and have little respect for how long it will or won't last...

Use hearing protection, and eye protection of course.

I favour 1/2 roundovers at a minimum, and like 3/4 when you can.

I did use 1/2 and 3/4 inch material, when laminating in the past, but I understand where you are coming from, with your questions.

5/8 is better than nothing, and mildly better than 1/2.  I would say you will be fine.

[James Romeyn]

Mark
You de man; thanks! 

I'm now considering a 3/4" radius & not worrying about the cosmetic effect of approximately 1/8" of the exposed roundover being particle board (5/8" BB ply over 5/8" PB w/ dado joints).   

The radiused BB ply 5/8" edge will have voids filled w/ a glaze before finishing.  The glaze will be dyed to cosmetically match the BB ply.  I'm thinking the glaze will appropriately smooth & fill voids in the 1/8" thickness of exposed particle board edge, making it look presentable.  It's too much work to install a solid wood corner for the radius.     

[Christof]

I will edit the post: should read 50%/50% rather than 1/2-1/2, which could easily mean inches.  Sorry!  Total panel thickness will be 1.25", again copying the speaker being cloned.  In this case that will be 5/8" PB under 5/8" BB ply. 

Have you guys ever radiused the corners on ply?  In my case the BB ply will be a high quality (5x5 panels, not 4x8) & plies will be fine.  Just wondering if someone could post a picture what the edges look like when radiused & clearcoated. 

Only the 5/8" thickness of the BB ply will be radiused; the 5/8" PB underneath will remain hidden under the dado.  Is a 5/8" radius large enough to minimize diffraction on a 2-way mid-size monitor?   

TIA.     

Bob Smith made those S-9's for a while that were entirely from Baltic Birch and they have a very pleasing finished edge...



Not a speaker but finished BB ply (not my work)

[JLM]

IMO (and others) the goal should be not to hear the cabinet, therefore it should be as inert as possible.  This relates to stiffness because it won't make sound if it doesn't vibrate.  A perfectly inert cabinet would allow you to hear only the driver (plus any room interactions).  Note that some manufacturers "tune" their cabinets to provide their own sound (typically "warm").  Personally, I don't want to hear such colorations applied to all the music.  But to each their own.

Stiffness is affected by choice of material, thickness, span, and joinery.  Stiffness is proportional to the material's Young's modulus (a measure of how much the material deflects for a given force per area applied).  Stiffness is proportional to the cube of the material thickness.  Stiffness is proportional to the square of the square of the span.  And the more resistant to rotation, the stiffer the joint.

All wood has roughly (within 10%) the same Young's modulus, even taking into account the voids and glue associated with MDF, particle board, or plywood.  But composite (sandwich) panels made up of different materials offer some help.  (The combined Young's modulus and panel thickness would both be affected.)  So cabinet design (span), then material thickness are the primary factors to provide an inert cabinet. 

[chrisby]

JLM:

FWIW, 2 of the most boring speakers I've heard in the last 10yrs were of quite different driver configuration, etc, but both composed of fairly inert materials

DIY 2.5way MTM SEAS Millennium tower in diamond cored basalt - gorgeous looking in all respects, but not very emotionally involving.  This system was demoed at the Craftsman's room at VSAC 2003 (at least 800 square feet and 20ft ceiling)  - with the very elaborate crossover and drivers' moderate raw sensitivity it took well over 30 watts of P/P tube to get anything happening.

The other was a commercial product with a name I can't recall, at a local high end dealer.  Single full range driver in a "Corian" enclosure, and outboard "compensation network".  The less said about this one the better. 


The same dealer also carries the B&W line, and for years I've had nothing but admiration and respect for the aesthetic design and production technologies in the N800 series enclosures.  I can't cite any empirical test data to support the opinion, but the enclosures of the 800 and 801's particularly should have little sound of their own.  However, they rather left me cold - lots of very precise "information", but no "goose bumps" for this listener.

By comparison, with proper room location and associated equipment, the undeniably colored and grossly overpriced AudioNote Model E's (easily fitting your description of "warm") were so much more emotionally involving for me than anything else in the showroom.   

I think there's enough latitude allowed in your "IMO" for the position that the goal should be to hear and "feel" the emotion of the music (otherwise it's just "patterned noise", AFAIC ), and that inertness of the loudspeaker enclosure is only one factor in the calculus, and it (inertia) can certainly be overdone.   

the soapbox is yours, again

cheers

[James Romeyn]

Sorry to myself for jacking my own thread. 

The sides/top/base of my favorite standmount by a wide margin (I've heard dozens of the most notable) are comprised of 1-1/4" solid ovangkol (ovangkol is an African rosewood-type; the baffle/rear are 1" MDF).  The designer/recording engineer advertises that the ovangkol was chosen as part of the speaker's final voicing.

I play guitar & am familiar w/ the world's best flat tops, including Klein of Sonoma ($30k+) & Schoenberg of Tiburon.  It's interesting that ovangkol is sometimes employed as a lower-cost substitute for rosewood by mass-producers such as Taylor.  In playing ovangkol, it indeed sounds similar to rosewood but seems to have a more flat, linear FR, which is consistent w/ my standmount speaker's presentation (in the best way).

I'd employ ovankol in my clones but cost for the material & necessary joinery has induced a desire to explore the lower cost laminate mentioned above.           

[planet10]

But listening tests nowadays are not consistenly filled w/ love for MDF/HDF, which may damp less well vs. particle board because of PBs larger irregular sized chips.  Also I'm thinking that MDF's higher mass increases its Q & moves the resonance point to a higher frequency, both of which are bad.      

1/ higher mass reduces the resonance of a panel
1a/ the amount of energy available to excite a resonance is inversely proportional to the square of the frequency (so pushing the panel resonances upwards is not a bad thing)

2/ the higher the Q of a resonance then a high quantity of sustained energy is required to excite the resonance. If the resonance is sufficiently high, this energy is just not available when playing music, so in effect the resonance does not occur.

dave

[JLM]

Chrisby,

Dang, lost my first attempt to post this due to computer "helpers"...   

Most materials that folks build cabinets from are relatively inert.  The obvious question should be:  What was the material’s Young modulus?

And how the cabinet material looks won’t affect the sound.  OTOH some cabinets generate more acoustical energy than the drivers mounted to it.   

I’m suspicious of any speaker that needs 30 watts to “wake up” as the basic function of a speaker is to react to dynamic pulses at any volume level. 

I can’t comment on how an unknown cabinet design or driver might sound, but have also read about cabinets made of concrete and other materials sounding dreadful.   Most brands of popular speakers, including B&W, haven’t “done it” for me in decades.  Personally I don’t want everything “colored”, but prefer semper fidelis (semper fi as the Marines say) or always faithful (to the original). 

I agree friend that without emotion, music is just auditory data.  As I age, I’m drifting away from the equipment side of audio and towards the art and beauty of the music itself.

[James Romeyn]

But listening tests nowadays are not consistenly filled w/ love for MDF/HDF, which may damp less well vs. particle board because of PBs larger irregular sized chips.  Also I'm thinking that MDF's higher mass increases its Q & moves the resonance point to a higher frequency, both of which are bad.      

1/ higher mass reduces the resonance of a panel
1a/ the amount of energy available to excite a resonance is inversely proportional to the square of the frequency (so pushing the panel resonances upwards is not a bad thing)

2/ the higher the Q of a resonance then a high quantity of sustained energy is required to excite the resonance. If the resonance is sufficiently high, this energy is just not available when playing music, so in effect the resonance does not occur.

dave

Important, relevent, audible points are missing in the above math.  It is a well-supported belief that the ear's sensitivity is not linear regarding the frequency of audible distortion.  The ear is almost deaf to multiple digit distortion in the bass range while distortion in the midband is easily detected.  Also, the main speakers are high-pass crossed around 85-90 Hz so in this case, again, raising the resonance frequency may not have the audible effects predicted by the math above. 

 

[James Romeyn]

...I agree friend that without emotion, music is just auditory data.  As I age, I’m drifting away from the equipment side of audio and towards the art and beauty of the music itself.

John Marks of Stereophile is probably my favorite professional audio writer.  His writing skill is exemplary.  He sings classical French music & has produced some amazing & enjoyable music CDs of which I own several.  Within the past couple years he recommended that audiophiles purchase a classical guitar & take lessons.  As a guitarist, I could not agree more w/ his recommendation.  The quality of instruments available now even in the $300 range is quite amazing.       

[frenshyflor]

My best acquaintance laminated 1/2 mdf, and 1/2 solid oak


_________________
Patio furniture

[planet10]

2/ the higher the Q of a resonance

To add to this: Research shown in Floyd Tool's new book shows that higher Q resonances are also less audible.

dave

[James Romeyn]

Finally built my clones w/ the above described laminate.  Comparing the original French OEM speaker to the clone (similar except enclosure material, OEM has offset tweeter/clone drivers verticaly aligned, OEM ported/clone is sealed), I prefer the clone.  Comparing knuckle taps fully loaded w/ xo & drivers: both enclosures resonate w/ about the same fundamental tone but the OEM has more extended overtones/clone has less overtones & sounds more dead/more highly damped.  I'm thinking the laminated panels of the clone offers a constrained layer damping feature (the two pieces comprising the laminate of each small panel were clamped & glued together w/ two 1.5" square maple to spread the clamp pressure across almost the entire surface).     

I give the described laminate my highest recommendation, A+.

Thanks for all the input.       

[jrebman]

Jimbo,

Congrats on finishing the project, and for explaining that resonances can be useful in the hands of a competent designer.

Chrisb, well said, some of the most totally dead speakers have me scratching my head why anybody would spend $50k, $100k, or $250k for such things.  As well, there are plenty of "live speakers that are too much too, but when done right, the resonances can be manipulated to complement the natural response of the driver, and every one of those I've heard has really connected with me.  I'd go further to say that those are the exception rather than the rule though.

-- Jim

[James Romeyn]

Again, one might expect that w/ today's myriad of modern computer aided tools & analysis, there would be almost universal agreement on one or two best overall panel materials.  Looking at the selection of cost no object choices, that is certainly not the current situation. 

[planet10]

Again, one might expect that w/ today's myriad of modern computer aided tools & analysis, there would be almost universal agreement on one or two best overall panel materials.

Except that in a lot of cases people miss some important noise mechanism. For instance, the typical big, dead sounding MDF cabinet is continuously oozing out low level, time smeared grunge that limits downward dynamic range. Turns out that the typical interpretation of good in this test is usually bad.

dave