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John Rethorst

Rectilinear X or Xa

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This was an acoustic suspension bookshelf model made around 1972. I'm looking for a pair (and so have posted in the For Sale/Wanted forum). I'd also like to know the difference between the X and Xa, and hope to find a user manual or at least a detailed ad. All information appreciated.

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Martin    0

Just ran across your post & wondered if you'd found a pair. I've been searching in vain for a pair for many years until last week when I finally found a pair of Xa.  Unfortunately, this pair was modified and is essentially, worthless, as the original woofers are missing and replacements are  nearly non-existent.  I remember the ads for them pretty clearly, even though it's been 45 years. As I recall, they were called a very "fast" loudspeaker. The first crossover point, to the terrific  Philips midrange, was 100Hz.  It was a radical design which I bet blew lots of midrange drivers and is probably why this model disappeared very quickly. 

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ra.ra    0

It's always good to see the Rectilinear models get some attention here. Shown below are some scraps of info that might be helpful - - it is difficult to get a full rundown on the Rectilinear product line-up, but this might be a start. 

Not unlike many examples of product nomenclature, I think the Xa represents a later version of the X. I am not entirely sure of this, but I believe there was a change in the driver elements and possibly the corresponding crossover as well. Along with the Mini-III, the X and Xa are the only acoustic suspension (fully sealed cabinets, no port) models in the line-up, and the only ones I am aware of with a 4-ohm nominal impedance rating. I suspect it will be this 4-ohm rating which makes it difficult to find authentic 10" replacement woofers.

rectilinear models.jpg

Rect line-up.jpg

Rect drivers.jpg

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Hi Martin, I have found a pair -- thank you. I'll take down my wanted ad (I had forgotten about it).

Quite a while ago the foam on one of the woofers decomposed and I went looking for a replacement. The local stereo shop had a 10" KLH 4-ohm acoustic suspension woofer that fit perfectly and sounded just like the original. Maybe it was of identical manufacture: I know Rectilinear didn't make any drivers themselves; I don't know whether KLH did or not. So it may not be too hard for you to find replacements. Since the crossover is 100hz, all the woofer does is real bass, and I'm sure 10" acoustic suspension units are still out there. 

I never blew a midrange driver on either pair I have. I think the model may not have sold well since it was in direct competition with Acoustic Research and their entire line of acoustic suspension speakers. AR had a great reputation; maybe anyone who wanted that design just went to AR.

The Xa had a slightly different crossover than the X. No other change.

I bought these after living in Boston for a year and going to the Boston Symphony as often as possible -- I was in the Coast Guard and, as active-duty military, could go to a concert and, an hour before the concert, buy any unsold ticket for $1. When it came time to buy a stereo, I bought a few records (vinyl) of the orchestra, recorded in Symphony Hall, famous for its acoustics, and went to stereo shops. During the week in the middle of the day they weren't busy and they let me listen a lot. These speakers really stood out for their resemblance to live performance. I was surprised -- I'd thought several brands and models would be about the same. Nope, and I haven't heard more realistic speakers since. They're still going strong, and I just wanted the second pair as backup. You should be able to fix yours easily. Please do -- they're one of a kind.

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ra.ra    0

Hey John, that's a great story about your speaker history and your experiences with Symphony Hall. It is such a fantastic building - - one of the many masterpieces designed by the noted NYC architectural firm of McKim, Mead and White - - - and I think that I have read (at Symphony Hall, no less?) that the design of this interior space basically created the discipline now known as acoustical engineering.

Your tale of the KLH woofer replacement might just offer a practical Rx for Martin's pending problem, but your comment also surprised me a bit. Earlier today, when I was trying to add some pertinent information to this thread, I came across this image of a Rectilinear Xa, but thought to myself ...."naaaaah, I'm not going to show a Rectilinear speaker with a KLH woofer." But now it seems fair game, and perhaps even prescient, so here's the pic that might look like your resurrected pair. 

Rect Xa w:KLH.jpg

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Martin    0

Great picture!  That KLH woofer really looks like it belongs elsewhere, like in a KLH 20, which was the only 4-ohm 10" KLH product I can recall.  Looks just like a KLH 17 woofer, but for the impedance.   While it's a nice fit, and to the uninitiated, it looks like it belongs there,  I think the original woofer used in the X & Xa must have been a bit more robust than the one used in the KLH 17/20.  It was probably comparable in performance to the bigger KLH 6 or 5 woofers as the X/Xa were very competent loudspeakers. 

BTW, I've also owned IIIs,  Mini-IIIs,  XIs & XIas.  You could say I'm a Rectilinear fan. 

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ra.ra    0

I have no further information regarding the image shown above, and I know very little about the various KLH woofers, but your comments sound very sensible and most likely accurate. I've got an early pair of XI's, and I am about to complete restoration work on another pair of Mini-III's.

If you haven't already seen the Rectilinear pictorial inventory here, you might enjoy this.

http://www.kallhovde.com/Njord Noatun's Vintage Audio Resources.html

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Martin    0

It's great to see some enthusiasm here for Rectilinear since they are largely forgotten.  BTW, the XI & XIa gave the KLH 17 & AR 4x some stiff competition. 

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Martin    0

After opening them up, I see the Xa has a fairly large MDF sub-enclosure for the midrange (& tweeter). Contrast this with the big, plastic, deli container that is attached behind the Philips midrange in the III. 

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ra.ra    0
14 hours ago, Martin said:

...the Xa has a fairly large MDF sub-enclosure for the midrange (& tweeter).

There are a few AR models that have a similar enclosure for open-back midrange drivers, but I've never seen an MDF sub-compartment on a Rectilinear speaker, and I've never seen one that also included the tweeter. Like the plastic tub you describe for the Rect III, it sounds identical to the ones I have encountered with the Mini III, as shown in attached pic.

Phillips mid.jpg

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