Acoustic Research AR2a found with all plywood cabs?

[Ficklistnr]

I've been sitting on a pair of Acoustic Research AR2a speakers that are in very good shape making them excellent candidates for a thourough restoration project. With no variations planned outside the original build specs.

However, I recently discovered something that struck me as quite unusual. I may just be confused by assumptions and misinformation but it has been my understanding that all AR2a cabinets while having several options of finish laminates ie: utility pine, unfinished walnut etc. The cabinets were all constructed of the same base material MDF panels on top bottom sides and front (baffle) with a plywood back found in earlier manufactured pairs, replaced with MDF in higher number series completely eliminating the use of plywood anywhere in the cabinet.

This obviously does t fit with what I have in front of me .
They are in fact factory cabinets with the original AR informational printed on paper and affixed at each corner with a single staple.
The baffle on each is in fact MDF however, each of the 5 remaining panels are 5 ply with no finish grade laminates. The back appears to be a lesser grade finish ply.

Does anyone have an explanaition for this? Am I mistaken or misinformed with my assumption that the AR2a had never been manufactured with an all-plywood enclosure?
Might I be in possession of a demo or customer requested special order? Or is it possible this set was built to compare and demostrate the accoustical differences between the two materials. It's my understanding that the use of MDF vs plywood was a hotbed topic in this era. I'm curious if earlier AR models were built with all plywood/MDF baffle cabinet material. And of course if an all MDF cabinet had been commonly found with a plywood back and an MDF back.

I have little doubt the cabinets in front of me were produced by AR and are not likely to be a post-sale modification.
All elements of design and construction are identical to that of an all MDF cabinet AR2a.

Ill add photos during daylight hours.

Thanks for any input and references in advance.

 

[alteclipsch]

I had a single AR2 (not 2A) of unfinished plywood construction that had been installed inside another console cabinet, and I've read this was fairly common. I'm no expert and I'm sure someone will be along shortly to give you a more educated answer.

 

[baco99]

The construction methods were not consistent. Older models were made all ply, yet some others were a mix of both. Later models almost always used all MDF, but I have seen some with ply used for bracing and backs. I have even seen some serial numbers close to each other that look like they were made a decade apart.

 

[audiojones]

Growing up we had a pair of AR2a’s that my dad bought brand new with all plywood cabinets. It was a money saving option if you wanted to paint the cabinets or build them into a custom enclosure.

I’ve got a pair now that have finished walnut veneer on three sides but the bottom is unfinished pine, another money saving option.

 

[baco99]

Here's an example: Two sets of AR3a, one from 1969, one from 1970. Cabinet construction on both is veneered plywood, but the internal bracing is glued ply on the 1969 and nailed and glued solid pine on the 1970.

 

[Blue Shadow]

The baffle is MDF and not chip board?

 

[ra.ra]

The baffle on each is in fact MDF however, each of the 5 remaining panels are 5 ply with no finish grade laminates. The back appears to be a lesser grade finish ply.

This sounds perfectly normal to me, even if MDF (probably more accurately: particleboard) was used for the front baffle panel. If there is no "finish grade laminate", then what you have are the unfinished pine cabinets - - sometimes referred to as "utility grade". The four pine side panels were always fabricated from plywood, and the rear panel was also typically plywood but of a slightly lesser grade.

Looking forward to seeing some pics.