AR-3a loudspeaker ? Plywood vs mdf

[thiptoman]

Just curious as to what type plywood these classic AR speakers are built from ? Is there a reason why AR used plywood to build their cabinets as opposed to fiber board ?

Can this type plywood be found today ?

One more question . Plywood vs mdf , which is better to build acoustic suspension cabinets and why ? Thanks !

[Andy]

Hopefully Tom Tyson will reply to this (he's very knowledgeable on AR), but my knowedge is that only very early AR were all plywood, 1954. And of course the unfinished models were pine plywood made until the early 1970's. MDF was used from early on, except for the back pannel which was plywood until maybe 1971 ?

I really want to here from Tom on this topic, he knows the history and sound quality differences on plywood vs. mdf

Andy

[thiptoman]

I'am looking forward to hearing from Mr.Tyson on this subject !

[Rlowe]

The following link may provide some answers in the interim;

http://www.classicspeakerpages.net/dc/dcbo...ing_type=search

[tysontom]

>Just curious as to what type plywood these classic AR

>speakers are built from ?

Early AR speakers, and those subsequent models built through the years in Utility Finish (Ponderosa Pine), were constructed of plywood, probably 9-Ply or something, but nothing special -- no marine plywood or anything. KLH, on the other hand, did briefly use marine plywood with 15- or 16-ply construction, but for no particularly good reason. The company soon went to MDF-type construction after the initial run of marine plywood (which, incidentally, is extremely strong but very expensive). You might characterize the marine-plywood construction as similar to the epoxied-frame woofers and tweeters in the early KLHs. Once the reality of cost became evident, the process was changed to more conventional methods.

>Is there a reason why AR used plywood to build their cabinets as opposed >to fiber board ?

MDF boards generally weren't readily available in the 1950s, to my knowledge, so the default wood was plywood. Contrary to what some have suggested, neither AR nor KLH ever used solid-board wood to build cabinets! Solid wood is totally incompatible with this type construction. The cabinet moldings on larger AR speakers were solid-stock wood, but not the cabinets.

> Can this type plywood be found today ?

This type of plywood is readily available today from about any woodworking supply source. Multi-ply interior-grade ¾-inch plywood sheets with veneered finishes are readily available, but once you price a piece of 4 x 8 ¾-inch plywood with, for example, Walnut veneer, you will quickly understand another reason why the cabinet industry went to MDF. Plywood is for strength; MDF is for deadness and true dimensions.

> One more question . Plywood vs mdf , which is better to build

>acoustic suspension cabinets and why ? Thanks !

While plywood is structurally superior to MDF, it is not as dead a material for cabinet-panel construction. It tends to “ring” more. This is one reason that AR put braces in the early plywood cabinets (this trend even continued after MDF cabinets came along). Since acoustic-suspension cabinets are sealed, there is even greater reason to have an enclosure that is acoustically inert, so to speak.

--Tom Tyson

[Andy]

It makes sense that MDF is superior to plywood, being more acoustically neutral, espeacially the Marine type used in the very early KLH speakers. Yes, the construction is like no other speaker cabinet I've seen. I count 12 ply's in my Model Six's (serial #'s 684 & 711) with very nice mitered joints at each corner. It's the most solidly made cabinet I've come across, but I'm sure this is not the best for the resonance produced. When I wrap on the cabinet with my knuckles, there is a distinct "ping" sound....incredibly solid and well made. As Tom mentioned, this cabinet was short lived, maybe just a matter of months in production, it must have been very costly to make.

All that being said, I think they sound great and since they are scarce, I don't think I could part with this pair.

Andy