14 replies to this topic

[JKent]

Picked up a pair of Rectilinear Mini III speakers today for $10. Circa 1969. They seem nice—close in size to AR 7 maybe? Real walnut veneer, although it is kind of beat up on these and will need a lot of patching. Nice grille cloth (kind of dirty), 2-layer like the KLH with a sheer black backing. Three-way system with level controls for mid and high. Nice binding posts.

Some peculiarities: The grilles are NAILED on with what appear to be 6d finishing nails, cut off so they are about 1" long. The whizzer-cone mid (Philips, I assume—there is a number embossed on the cone--2376) is enclosed in what appears to be a 1 qt container like they put egg salad in at the deli (these were made in Brooklyn. Probably a lot of delis ). The woofer has a nice cloth surround. Tweeter is tiny. The stuffing is not fiberglass or rock wool—looks like something used in furniture (?). The cross over has 2 caps of unknown values, but I have asked a friend to measure them and give an opinion. They are marked "XMC" (larger one) and "XTC-M".
Kent

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[joelongwood]

Picked up a pair of Rectilinear Mini III speakers today. Circa 1969. They seem nice—close in size to AR 7 maybe? Real walnut veneer, although it is kind of beat up on these and will need a lot of patching. Nice grille cloth (kind of dirty), 2-layer like the KLH with a sheer black backing. Three-way system with level controls for mid and high. Nice binding posts.

Some peculiarities: The grilles are NAILED on with what appear to be 6d finishing nails, cut off so they are about 1” long. The whizzer-cone mid (Philips, I assume—there is a number embossed on the cone--2376) is enclosed in what appears to be a 1 qt container like they put egg salad in at the deli (these were made in Brooklyn. Probably a lot of delis ). The woofer has a nice cloth surround. Tweeter is tiny. The stuffing is not fiberglass or rock wool—looks like something used in furniture (?). The cross over has 2 caps of unknown values, but I have asked a friend to measure them and give an opinion. They are marked “XMC” (larger one) and “XTC-M”.
Kent

Congratulations, Kent, nice score! Having not been able to get into mine (the grill is REALLY on there), it's nice to finally see what's inside. My grill is a dark brown, quite thick material. The mid appears to be similar to the Philips mid used in the larger III (both Highboy and Lowboy). The dustcap is different, as it's flat rather than convex, and the surround is slightly different as well. The tweeter appears to be the same as the super tweeters used in those models as well. The deli container is another thing that the Mini III has in common with its larger brethren, as it serves to isolate the midrange driver in them as well.
Be aware though, that unlike the larger IIIs, the Mini is a 4 ohm system.
I'm anxious to hear what you think of the sound. I spent a good portion of the day listening to the Mini IIIs driven by a Harman Kardon 730 Receiver. The sound, to my ears, is a bit laid back, but very smooth and non-fatiguing. It's a speaker you could listen to all day.............and I did.

[JKent]

close in size to AR 7 maybe?

Correction on the size--they are bigger than I thought: 12x19x9. Bigger than the AR7 (7.75x16x6.25) and even a little bigger than the AR4x (10x19x9). Smaller than the KLH 17/20 (12x23x9). The Rectilinear Mini III is a 4 ohm system.
That "whizzer cone" midrange (or one like it) was apparently used in all Rectilinears, or at least the LowBoy and HighBoy. I think it was also used in Dahlquists. My first encounter with the whizzer cone was in an Advent 400 radio speaker. I thought it was a replacement, since I had only seen standard 5.25" full-range speakers in the 400, but maybe Advent switched to the Philips driver at some point? See discussion here:
http://www.classicsp...?showtopic=2936
Kent

[JKent]

Thanks to RoyC (one of the authors of the excellent "Restoring the AR3a" brochure):
http://www.classicsp...ring_the_ar-3a/

here is some info on the Rectilinear Mini III caps:
The large cap [XMC] measures about 87 uf and the little one [XTC-M] is about 1.8uf. The Rectilinear IIIs (not Minis) used 2.0 caps so that may be the intended value. It appears that DF is the same as an equivalent modern npe, so it is entirely possible they are still within spec.

[JKent]

I replaced the 1.8uF (2 uF?) caps with 1.9uF mylars. Left the 87ish caps. Pots are good--no corrosion like the AR Aetna-Pollock pots. Still working on the cosmetics--had to patch some of the veneer. Will post exterior photos when finished.

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[JKent]

The Mini IIIs are coming along nicely. Had to do some patching of the veneer as shown in the pics. Replaced the small caps but left the large ones. Tried cleaning the grille cloth while it was still on the frame but that did not work out too well—it's 2 layers, like vintage KLH, with sheer black backing. Finally removed it, washed by hand, pressed it and reglued both layers. We'll see how it turns out. I may have to go with new linen although that's not really authentic for these.

You can see where I had to cut out damaged veneer and replace/patch it. I've also noticed one speaker cabinet is quite a bit darker than the other, so I'm using "natural" Watco oil on the dark one and "dark walnut" Watco oil on the lighter one. In the photos, the more finished one is the lighter speaker in the bottom right photo. The one with the patch (not yet oiled) is the darker one on the bottom left.

Will post finished pictures eventually, but getting closer!
Kent

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[joelongwood]

The Mini IIIs are coming along nicely. Had to do some patching of the veneer as shown in the pics. Replaced the small caps but left the large ones. Tried cleaning the grille cloth while it was still on the frame but that did not work out too well—it’s 2 layers, like vintage KLH, with sheer black backing. Finally removed it, washed by hand, pressed it and reglued both layers. We’ll see how it turns out. I may have to go with new linen although that’s not really authentic for these.

You can see where I had to cut out damaged veneer and replace/patch it. I've also noticed one speaker cabinet is quite a bit darker than the other, so I'm using "natural" Watco oil on the dark one and "dark walnut" Watco oil on the lighter one. In the photos, the more finished one is the lighter speaker in the bottom right photo. The one with the patch (not yet oiled) is the darker one on the bottom left.

Will post finished pictures eventually, but getting closer!
Kent

Beautiful job, Kent.........as usual. You make me feel guilty for playing mine "as-is." But since they're in my man-cave, the WAF is not an issue, and I can live with just about anything as long as it sounds good. And, to my ears, the Mini IIIs sound damned good.............I'm anxious to hear what you think.

[JKent]

Finished! and they do sound nice. I'll post some "after" pics, but I decided to make new grilles. Even with washing, ironing, starching, the old ones just looked dingy. And the panels are only thick cardboard! I made new ones from 1/4" Masonite, glued sheer black cloth on them (like the originals) then covered with Irish linen (like ARs of that period--not exactly like the original Rectilinear.
Kent
edit: 1/8" Masonite would work fine, and maybe omit the sheer black backing for better transparency.

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[JKent]

Here they are. Lookin' pretty good for $10 speakers. One is still lighter than the other, so I "may" do some more Dark Walnut on it, then again my friend the wood turner says "If you want consistency buy Formica!" There are a couple of patches--most notably one strip along the entire side, visible in one of these. Look at the earlier posts for "before" shots (I'll probably delete some to make room). Knobs on level controls are not original--they're from Rat Shack. Anyone know why the foam around the whizzer-cone mid? Is it to control refraction?
Thanks for looking at this project
Kent

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[ra.ra]

Hmmmm ...... four years lag time - - - any chance of reviving this thread?

First, some initial observations. I am very impressed with the build quality of this vintage of Rectilinear speakers - these little guys are heavy, dense, and compact. But actually, despite my calling them 'little' and Rectilinear titling them as "Mini", these speakers are not really so tiny at all. While JKent first likened them to AR-7's and then updated his comparison to AR-4x, these speakers are actually the nearly identical dimensions (albeit 2" deeper) as the AR-6. Even so, while a 4x weighs in at 18.5 lbs. and an AR-6 at 20 lbs., these brutes tip the scale at 25 lbs. apiece.

Next, a couple of questions. When all but one of the other Rectilinear speakers from 1971 have 8 ohm impedance, why was this speaker product designed at 4 ohms? Following this, why does the tweeter cone have 8 ohms stamped on it? And the tweeter cap - - - thanks to JKent and RoyC, I see his measured at 1.8 uf and was replaced with 1.9 uf (where does one find this cap - which brand makes 1.9?), but would it make more sense to pursue a replacement cap of 2.0 uf per the comment that it was a typical value in other Rect. products?

While making comparisons to AR products, it appears to me that this woofer is nearly identical to that in the AR-4x. The basket, cone and magnet appear exactly the same, but this woof has an opaque felt dust cap and an inverted roll profile on the fabric surround. The spider has the same profile, but the material has a different texture and color.

A couple other peculiarities. My version has the dark brown Rectilinear grille cloth over the thin black scrim (2 layers), but strangely, the grille frame is made from two layers of 1/8" masonite. And just like an orphan Rectilinear XI that I have, the woofer is secured to the baffleboard with a rather odd fastener (see pics 1 and 2). No T-nuts and machine screws here - - - this device is basically a headed and threaded nail, punched thru from behind, with threads which accept a standard hex nut. This spike has a dangerous and sinister point which is no fun to work around.

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[JKent]

Hi ra.ra
Roy sent me the 1.9uF caps but 2.0 is close enough. And if I were doing it again I'd replace the big "maybe 87" caps with new 90 or even 100uF NPEs. I don't trust anything that resembles the infamous Callins PVC caps.
The tweeter is 8 ohms but the overall system is 4 ohms. Not that unusual. The 4 ohm KLH 20 and the 8 ohm 17 used the same tweeter and crossover, just different woofers.
Kent

[ra.ra]

Kent:
Great advice, thanks so much. I really don't know much at all about the wide, wide world of capacitors, and it all baffles me a bit frankly. Still, I agree with you that if you have the patient opened up on the operating table, why not check the liver while you're transplanting the kidney? NPE's are so inexpensive, it makes sense to replace both. The thought that Rectilinear may have used a standard 2.0 uF cap in several models sounds logical, so that's what I'll do for the small cap.

The note about the KLH speakers is interesting - - - so paralleling this discussion to AR, why is this not a similar case with the impedance of the tweeter in the AR-3 being the same driver as the tweet in the early AR-2ax? Am I correct that these two speakers had different drivers (although they look the same) based on the 3 being 4 ohm and the 2ax being 8 ohm?

[JKent]

The 3 (NOT the 3a) did use the same tweeter as the 2ax. Same driver. I can't explain it--for that you'd have to talk to Roy or John.
btw--another cheap way to replace the 90-ish cap would be a whole bunch of 10uF surplus caps from Madisound. They are 60 cents each, so 9 of them (90uF) would cost $5.40 per speaker. Not bad.
http://www.madisound...ap-10mfdp/tyee/
For the 2uF, if you go with Madisound, they have Solens
http://www.madisound...len-capacitors/

Kent

[fisher400]

I have had rect. research mini 111's stored away for a number of years, I hooked them up to my fisher 400 amp and they sound great. but the midrange speaker has come loose, seems to be some kind of glue holding it in place. does anyone know how to fix this. i want to refinnish the cabinets not sure how about going about it....gonna do the fisher cabinet too.
Thanks
Charles.

[ra.ra]

Hi Charles, and welcome to CSP.

This thread has helped me understand this Mini III speaker much better, and I am about to soon replace the capacitors in mine. Although I have never seen it identified or confirmed as such, it appears to me that the mid and tweet drivers are secured to the baffleboard only with what appears to be clear silicone caulk - - - a chemical bond rather than a mechanical one (screw, bolt, etc.). I don't know exactly when clear silicone became readily available in the consumer market, but these speakers probably date from the very early 70's and I know that silicone caulk was frequently in use in the construction industry by the mid 70's. It is fairly easy to use from a tube (with a typical caulking gun), has some odor which off-gases with the curing process, and is an extremely strong adhesive.

As for the cabinets, I have done many amateur wood refinishing projects but never knew about the Howard's products until I began reading these forums. Now that I've tried the Restor-a-finish, I will always consider this product and wouldn't hesitate to recommend it for your walnut veneer - - - it is what many readers here seem to prefer. It comes in many flavors - - - you may wish to try natural, walnut or maybe even mahogany if you like the enhanced red qualities in some walnut veneer.