Baltic Birch Ply in Perth?

[andymcw110]

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

[Sprog]

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.

[MrFixIt]

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 resonates :)

[wixy]

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.

[andymcw110]

WIXY

What type of wood was the marine ply?

Hoop pine? a softwood or hardwood finish?

Chars

Andy

[MrFixIt]

Hi

It's been proven by many that ply sounds better than MDF in some speaker types.

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.

But this is completely subjective and ONLY to YOUR ear. This does not convey how well the driver performs in either cabinet, only how much you prefer one cabinet over the other.

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 sounds :)

[wixy]

There is lot's of discussion on www.diyaudio.com (http://www.diyaudio.com) in relation to mdf vs ply, here's one long thread:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=109685&highlight=

[MrFixIt]

Hi

There is lot's of discussion on www.diyaudio.com (http://www.diyaudio.com) in relation to mdf vs ply, here's one long thread:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=109685&highlight=

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 :doh: )

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. :2tsup:

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
.

[noodle_snacks]

There is lot's of discussion on www.diyaudio.com (http://www.diyaudio.com) in relation to mdf vs ply, here's one long thread:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=109685&highlight=


Discussion doesn't constitute proof, but plywood is definitely advantageous for durability. My opinion is that performance/cost is greater for MDF.

[andymcw110]

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

[wixy]

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?

[clubbyr8]

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.

[MrFixIt]

Hi

As for the ply vs mdf debate, ply is stiffer than mdf and stores less energy. Wouldn't this mean it would resonate less?

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 (http://www.klipsch.com/products/details/klipschorn.aspx) 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 :2tsup: "problem solved" :D :2tsup:

[GraemeCook]

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

[andymcw110]

Hi Graeme

I'm interesed! .... Can you post pix of the speakers or supply a link.

Cheers

Andy

[Pheonix]

Funny thing, the yanks rave about baltic birch ply make nearly everything from it ,comes from Russia I understand,I have never ever seen it, only seems to come in 5'x 5' sheets.
Any clues anybody?

[GraemeCook]

Hi Graeme

I'm interested! .... Can you post pix of the speakers or supply a link.

Cheers

Andy

Will try, Andy. I am the only person in Australia without a mobile phone or digital camera, so I'll have to ask a mate to help. Might take a few days...

Cheers

Graeme

[GraemeCook]

Hi Andy

This is my first attempt to include a photo with a posting. Hope it works.

Graeme

[GraemeCook]

Hi Andy

It worked. Amazing. Remember, its 30 years old.

I also drew a cutting plan for the MDF. You can get both speakers from a full sheet (8x4) plus a small sheet (2x4).

I drew it with paint and its 900 kbt and I cannot yet reduce it below the 100 kb limit on this board. Am not the worlds best geek.

Graeme

[andymcw110]

Hi Grahem

Thanks for going to the trouble of getting the pic online, what would you estimate the internal enclosure size to be and is it a sealed or vented enclosure .... is that the amp on top of the speaker? what is it?

Interesting colour choice too ... does it scare the children!

Cheers

Andy

[GraemeCook]

Hi Andy

I have emailed cutting plan to you privately.

I think each box is approximately 88 litres internal.

For first 25years they were not vented; quite tight uncoloured sound. Then I simulated it using WinISD and decided to add a pair of vents. 110mm diameter from Jaycar. Modified speakers are louder than before, with much more base extension. Richer, more detailed sound.

Actually I modified one speaker only, then listened. After balancing sound levels I decided I preferred the vented sound and then did the second speaker. The vents are in the bottom.

Colour is the same as the walls! And I plead the Nuremberg excuse.

Cheers

Graeme

[RonaldR]

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

The price in Australia is over the top when you find it and most of the shipment has been gone through leaving only the 2nds, I built speaker boxes in the mid 70's for ELECTRO VOICE speakers 12’’ woofers then horns for high and mid –range the cabinet size is around the same as a Marshall 4x12 Cabinet.
When I bought the ply –back then most timber yards had a good selection of Ply but now they all carry the same poor quality that is overpriced (a Friend in USA buys Baltic birch plywood he pays the equivalent of $46au per sheet of 18mm.
The only solution in Australia is MDF and the worst thing about that is you have to wear a mask not to breathe in the as it is very dusty to work with. But you get a nice finish and there is a good selection of finishes to give you a good looking set of boxes, the finishes you can use is as simple as paint, or glue on finishes such as veneer or laminate or similar or even contact you buy by the roll and it has an adhesive back and you just have to make sure you don’t get Air bubbles. I could tell you about some fantastic Finishes from a paint company in the USA but with shipping expensive. If I was you I would be using MDF and a Dulux Gloss. (MDF is made to be painted) if you have the skills go to Large automotive chain and buy Duco and you can have an amazing Gloss finish.