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Thread: Baltic Birch Ply in Perth?
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2nd May 2008, 01:15 PM #1New Member
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Baltic Birch Ply in Perth?
Hi All
I d like to build a set of speaker cabinets to suit my refurbished 12" Tannoy Gold (Scottish) speakers.
Researching, I have read that Baltic Birch plywood is highly recommended but in Australia it's hard to get hold of, I Found some 16mm birch ply in Melbourne @ $60 sheet 1400 x 1200 (would need 3 sheets) but cost effective shipping is hard to sort .... any suggestions on that one?
I'm looking for 3/4" (19mm)
Someone suggested Hoop Pine ply.
your thoughts and suggestions would be appreciated.
Cheers
Andy
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2nd May 2008, 02:53 PM #2
Carbatec in Balcatta had some Birch ply, it was thinner than 16mm. They can order in your requirements.
Have you thought about veneered MDF? Nice and stable looks good when finished and is ideal for speaker cabinets.
Growing old is much better than the alternative!
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2nd May 2008, 10:44 PM #3
Hi
Any GOOD QUALITY ply (of appropriate thickness) would do the job. However, unless you REALLY want the Birch ply finish, you would be better off using a thicker MDF. 16mm ply is (IMHO) on the borderline of being too thin for speaker cabinets, 19mm or greater is preferred.
Speaker cabinets usually sound better when they are made from a very dense material, preferably something WITHOUT grain. 32mm mdf would be very good and can be sourced reasonably easily. All (kitchen) cabinet makers use 32mm mdf for the counter tops.
You can then finish the outside in whatever you prefer. Don't forget to include some internal bracing, even 32mm MDF can influence the sound quality if it resonatesKind Regards
Peter
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3rd May 2008, 11:16 AM #4Member
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It's been proven by many that ply sounds better than MDF in some speaker types.
I decided to experiment and constructed one speaker out of marine ply and the matching speaker out of mdf. I think the mdf speaker sounds slightly more "dead" in comparison.
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4th May 2008, 09:00 PM #5New Member
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WIXY
What type of wood was the marine ply?
Hoop pine? a softwood or hardwood finish?
Chars
Andy
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5th May 2008, 12:55 PM #6
Hi
I'd really like to read some of that "proof" do you have any points of reference, eg web sites etc?
I decided to experiment and constructed one speaker out of marine ply and the matching speaker out of mdf. I think the mdf speaker sounds slightly more "dead" in comparison.
The ply cabinet would have a greater tendancy to resonate when compared with the MDF version. This (potential) resonance can EASILY influence the overall sound giving it a rounder or more mellow tone. This could be your sound "preference". ie to you this ply cabinet "sounds" better.
There is nothing wrong with your preference, it's just different. However the ply cabinet may not refllect the "true" reproduction of the original sound. (The MDF cabinet could be just as incapable of reproducing a good quality sound).
The fact that you describe the sound from MDF cabinet you made as "dead", makes me think that this could well have been the "flat" response of a good cabinet compared to the potentially "warmer" or resonant "enhanced" / "boosted" ply cabinet.
It always is of course a subjective situation as peoples ears vary in their ability to hear or appreciate soundsKind Regards
Peter
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6th May 2008, 10:12 PM #7Member
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There is lot's of discussion on www.diyaudio.com in relation to mdf vs ply, here's one long thread:
http://www.diyaudio.com/forums/showt...9685&highlight=
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7th May 2008, 01:52 PM #8
Hi
Thanks for the link. I read the various comments. Excuse my being blunt, but what a load of crap in most messages!
One guy even wanted to use 1/2" ply for the sides of his cabinet. That's just TOO thin.
Another described making speakers as making musical instruments DUH!
Speakers are made to REPRODUCE the sound of the ORIGINAL instrument and in theory are NOT to change or influence the ORIGINAL sound. Several messages spoke of or alluded to the capability of ply to enhance or otherwise make the resultant output "better" because ply resonates and MDF (as someone in that thread wrote) sounds "dead".
The link is to a bunch of idiots talking crap to other idiots. There were no realistic or "provable" threads of any consequence. The discussion there was similar to the discussion here.
There will always be pro's and con's for both materials. The best speakers have no real resonance of their own or the resonances are so low that they do not influence the human audible frequency range range. Speakers of themselves have to be inert as far a the music is concerned. They need to "hold" the driver in position and guide or amplify (ie expand) any air movement created by the rear motion of the driver. Such movement of air and the designs and styles of speaker is, or can be quite esoteric.
I do NOT profess to be any kind of authority on speaker design, however I have read much about "speaker" theory etc and made quite a few speakers in my time - though not for quite some time.
Speaker cabinet designs NEED to be as heavy an inert as possible to help prevent any undue influence on the sound reproduced by the driver. Some of the better sounding speakers have been made of concrete or been built into walls such that there IS NO cabinet influence on the sound created by the driver.
I have an old, old, old set of KEF concerto speakers. I bought the drivers many years ago in Singapore (when KEF Concerto's were one of the best rated speakers of their time). I purchased the cabinets -in kit form - at home in Perth. I built these cabinets and used several pieces of 4"x2" Jarrah to prevent the resonance of the top/bottom/sides/front and rear.
The (original KEF equipment) cabinet is made from MDF. The combination of this and the reinforcing I used inside the cabinet has provided a great sounding system. This is of course MY subjective "interpretation" of the sound I like. There is no scientific evidence in this message that states MDF is better than ply.
All I can say is that from my experience MDF always wins out (IMHO) because it is more dense and is therefore less likely to influence the sound reproduction of the driver. (not like the idiot in the linked thread that talked about the speed of sound is faster in more dense material like MDF, therefore MDF is not as good as ply )
If as was described in the linked thread, the speaker is a musical instrument, EACH individual cabinet would have to be tuned to the driver to make the cabinet match the driver. Now I know that some manufacturers do do this and the results are spectacular, but the DIY'er can't do this. So (again IMHO) it is far easier to use a dense material that will not influence the overall sound.
The COST of superior quality ply, which is needed if voids in the ply are to be avoided, will NOT justifiably improve the sound quality. IOW many more dollars wil be spent for no appreciable gain in sound.
BTW if the OP still wants to use ply, BIRCH or otherwise, it will still be better if TWO thicknesses of ply are used for ALL sides of the cabinet. (adding to the cost)
HTH
.Kind Regards
Peter
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7th May 2008, 08:12 PM #9
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7th May 2008, 11:00 PM #10New Member
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Thanks for all the info people, appreciate your input.
I've finally committed myself to the Marine ply Hoop Pine, considerations were ... stability, finish and being void free ... to some no issue, to others a necessity. also a great deal from my local timber supplier, the edges will be Euro Beach.
design will be Trapezoidal with adequate internal bracing and finish will be with various of coats of Tung oil and elbow grease.
Preview of design... Defination Gold 900.jpg
Speakers will be 12" Tannoy golds (35 years old)
will post pix when finished.
Cheers
Andy
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10th May 2008, 04:40 PM #11Member
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Design looks great! I used to have Tannoy 12" Monitor Golds and know how great they sound.
As for the ply vs mdf debate, ply is stiffer than mdf and stores less energy. Wouldn't this mean it would resonate less?
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11th May 2008, 08:37 AM #12
I would have had a look at what some of the local manufacturers use. I'm a big fan of VAF (Adelaide based). They use veneered MDF. Their cabinets are superb. They are very well braced, extremely well finished and nice and heavy. They don't seem (to me) to resonate, there is no vibration from the cabinets even at high volume.
However, saying that, I've never heard a speaker whose cabinet was made out of ply.
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11th May 2008, 03:50 PM #13
Hi
Resonance is caused by the ability of something that can vibrate in some harmonic to that with which it is in contact. The contact may be direct or indirect.
The movement (vibration) in the resonating item ie in this case a speaker cabinet is caused by the ability of any part of the cabinet to move "in tune" with or more accurately "in HARMONY" (harmonics) with the sound being produced by the driver.
Now within an object that has a grained structure, where those "grains" are following a shape or form in an unbroken "chain" or pattern, then that object has an ability to resonate.
If that "grain" is broken up, ie does NOT follow a shape or form OR that grain IS broken then the resonant ability is also "broken" ie it cannot resonate, its grain cannot vibrate in tune.
You can easily prove this in many ways with something that is broken.
A wine glass for instance. A wine glass when gently stuck will have a wonderful ring to it (it resonates to the vibration after being stuck). If there is the smallest of cracks in that wine glass it loses the ability to "ring" because the "grain" is broken. It no longer has the ability to resonate as there is a break in the "grain".
Now, if you "translate" this broken grain effect to MDF and ply. The timber used in ply has a grain. Within this grain there are unbroken bonds of fibre so there is an inherent ability to resonate. This is stretching the point here really because the cross laminations already help prevent resonance. However the resonant tendencies are there.
In the construction of MDF there is no real chain of fibres as they begin with a pile of unconnected "wood chips". These are then compressed into a dense material but still remain "unconnected" as each "grain" is separated by the "glue" used to canstruct the sheet material.
Because of the method of construction, MDF is inherently more dense than ply. The greater the density the more difficult it is to create a resonant vibration.
I note with interest that in two messages within other forums, there has been a reference to MDF "sounding dead" or "sucking the life out of the music".
This implies that the "other" construction materials ARE having an affect on the sound (music). They are adding a "sound" of their own. As I said in a previous message speaker cabinets should not influence the sound in any other way than that of their design eg acoustic suspension, bass reflex, transmission line or horn etc The klipschorn speaker from Klipsch has to be my absolute favorite speaker. It uses the room in which they are placed as part of its sound transmission. The only speaker (in a suitable room) of producing a 30Hz standing wave! WOW!
Interestingly in regard to the subject of THIS thread, the Klipschorn speaker is constructed from both ply AND MDF "problem solved"Kind Regards
Peter
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13th May 2008, 02:15 PM #14
Hi Andy
I bought a pair of 15" Tannoy HPD385 speaker drivers in the mid-70's and then made the boxes for them.
My boxes were initially to be a copy on the Tannoy Berkely design, but then someone suggested that I would get better results if I eliminated parallel sides and right angle corners. Something about standing waves, I think...
I then redesigned the boxes to be "flat topped pyramids" and made them out of 25 mm MDF. Thirty years later they still sound great, albeit with new foam surrounds on the cones.
Last year I looked at upgrading and sound tested many speakers. Nothing that retailed for less than $10,000 was significantly better.
After all these years the boxes are still in excellent condition, MDF lasts, and they sound better than commercially available stuff made from plywood.
If I made them again I would still use MDF, but I might think about increasing the thickness to 32 mm. Difference probably would not be noticeable, but you will never know if you don't try.
Enjoy your speakers; you have got the best in the world.
Cheers
Graeme
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13th May 2008, 04:15 PM #15New Member
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Hi Graeme
I'm interesed! .... Can you post pix of the speakers or supply a link.
Cheers
Andy
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