DCM Time Window

[anmpr1]

Since no one has said it, I'll be the corpse at the party. Vintage speaker restorations are often a crap-shoot. The wrong year of driver may have been substituted, or in many cases a cheap generic driver that sort of looks like the original. Don't let me discourage you, but keep that in mind as you shop.

Replacement of parts for a 50 year old product has to be hit or miss. Even for a product as ubiquitous as the '70s L100, which sold in much greater quantities, and which company is still active today. The upside is that for speakers such as older JBLs, or vintage AR, there is a hobbyist set that can help, and you can find replacement drivers fairly easily. JBL drivers were pretty rugged, so getting decent parts from scavenged units is possible. I don't know about drivers from original AR.

Then there is intra-model variation. JBL made at least three versions of that speaker, in addition to using several versions of its individual drivers, all having the same basic number. For example, there were at least four versions of the LE-25 tweeter over the course of production. I can't speak to sonic/measurement differences among the various production units.

Also, early L100 were wired differently than later versions.

JBL's spec sheet (see below) listed suggested replacements, once individual drivers went out of production, but noted that replacements should be done in pairs, since the sound of the stereo set would be different. Of note: the company's suggestion to use the 035t metal tweeter as a 'last resort' was an understatement. Finally, the spec sheet indicated that the 035 was 'drop in', but the baffle would need to be cut in order to make it fit up against the midrange driver. Perhaps on the 4311 it would be 'drop in', but I never checked that.

I'd imagine that attempting to refurb a more limited distribution loudspeaker like the DCM would be that much more difficult.

 

[fpitas]

Replacement of parts for a 50 year old product has to be hit or miss. Even for a product as ubiquitous as the '70s L100, which sold in much greater quantities, and which company is still active today. The upside is that for speakers such as older JBLs, or vintage AR, there is a hobbyist set that can help, and you can find replacement drivers fairly easily. JBL drivers were pretty rugged, so getting decent parts from scavenged units is possible. I don't know about drivers from original AR.

Then there is intra-model variation. JBL made at least three versions of that speaker, in addition to using several versions of its individual drivers, all having the same basic number. For example, there were at least four versions of the LE-25 tweeter over the course of production. I can't speak to sonic/measurement differences among the various production units.

Also, early L100 were wired differently than later versions.

JBL's spec sheet (see below) listed suggested replacements, once individual drivers went out of production, but noted that replacements should be done in pairs, since the sound of the stereo set would be different. Of note: the company's suggestion to use the 035t metal tweeter as a 'last resort' was an understatement. Finally, the spec sheet indicated that the 035 was 'drop in', but the baffle would need to be cut in order to make it fit up against the midrange driver. Perhaps on the 4311 it would be 'drop in', but I never checked that.

I'd imagine that attempting to refurb a more limited distribution loudspeaker like the DCM would be that much more difficult.


View attachment 249924

Yes, it can get difficult to find the right parts. Complicating the matter for higher-end stuff is the "flippers" who just don't care, as long as they can move product.

 

[mhardy6647]

As a fellow with way too much interest and investment in a motley array of vintage loudspeakers of very differing types (and worthiness), I'll offer, gently, a counterpoint.

I think it depends on the loudspeaker and the interest and expertise of restorers. Look, e.g., at the Polk Audio forums and the depth of information held by the collective on the many, many (!) subtly different flavors of Polk's long-ubiquitous 6-1/2 inch "midbass radiator". Most of the interesting vintage loudspeakers have astonishing if diffuse "databases" of expertise in finding and rehabilitating appropriate bits and pieces for restoration.

I suspect it's not all that different than the vintage auto restoration gambit -- I mean, if you have a 1954 Nash and want to do a period-correct restoration... it can be done.



See what I mean? They just kind of accrete sometimes.

EDIT: Of course, in fairness, I am listening to a decidedly nonvintage pair of Polk R200 two-ways as I type this -- and quite happily so.

 

[anmpr1]

I am listening to a decidedly nonvintage pair of Polk R200 two-ways as I type this -- and quite happily so.

Also, refurbing a loudspeaker depends a lot upon how it was constructed. With many boxes, you just screwed out the drivers and replaced whatever needed to be replaced.

DCM TW enclosures were evidently semi-sealed inside a wrap-around foam grill. To get to the drivers, the foam skirt apparently had to be ripped away from the outside of the box.

L100 were built to confound home repair. The 'foilcal' covering the crossover assembly (with serial numbers embossed) had to be removed before you could get to the crossover. Removing it permanently damaged the label. Some have had a certain amount of luck using a hot air gun to melt the foil's glue, but invariably the foil is bent out of shape when scraping it off. Gluing it back on shows bends and wrinkles.

I seem to recall that JBL factory repair would install a new foilcal and print the same serial numbers. Today you can buy foilcal replacements from third parties, w/o the serial number, but that are otherwise identical.

AR and probably most others simply put the crossover on the back of the speaker box, so all you had to do was remove the drivers, pull out the stuffing, and then access the unit.

Polk's Monitor RTA 12 (not the later SDA model) had the crossover on top of the speaker cabinet, covered by a small grill cube. Those early Polk Monitor series speakers were quite good sounding, and could be considered excellent value for the money.

 

[fpitas]

As a fellow with way too much interest and investment in a motley array of vintage loudspeakers of very differing types (and worthiness), I'll offer, gently, a counterpoint.

I think it depends on the loudspeaker and the interest and expertise of restorers. Look, e.g., at the Polk Audio forums and the depth of information held by the collective on the many, many (!) subtly different flavors of Polk's long-ubiquitous 6-1/2 inch "midbass radiator". Most of the interesting vintage loudspeakers have astonishing if diffuse "databases" of expertise in finding and rehabilitating appropriate bits and pieces for restoration.

I suspect it's not all that different than the vintage auto restoration gambit -- I mean, if you have a 1954 Nash and want to do a period-correct restoration... it can be done.



See what I mean? They just kind of accrete sometimes.

EDIT: Of course, in fairness, I am listening to a decidedly nonvintage pair of Polk R200 two-ways as I type this -- and quite happily so.

I'm sure it can be, and is done with TLC at times. I've just seen far too many old "Altecs" that sold for quite a premium, but when disassembled proved to have no Altec drivers. I mean the 802 wasn't a shining star, but it's better than the $25 PA CD someone stuck in there

 

[mhardy6647]

I'm sure it can be, and is done with TLC at times. I've just seen far too many old "Altecs" that sold for quite a premium, but when disassembled proved to have no Altec drivers. I mean the 802 wasn't a shining star, but it's better than the $25 PA CD someone stuck in there

You won't see that at my house

Well... maybe on an off-day...

 

[mhardy6647]

Also, refurbing a loudspeaker depends a lot upon how it was constructed. With many boxes, you just screwed out the drivers and replaced whatever needed to be replaced.

DCM TW enclosures were evidently semi-sealed inside a wrap-around foam grill. To get to the drivers, the foam skirt apparently had to be ripped away from the outside of the box.

L100 were built to confound home repair. The 'foilcal' covering the crossover assembly (with serial numbers embossed) had to be removed before you could get to the crossover. Removing it permanently damaged the label. Some have had a certain amount of luck using a hot air gun to melt the foil's glue, but invariably the foil is bent out of shape when scraping it off. Gluing it back on shows bends and wrinkles.

I seem to recall that JBL factory repair would install a new foilcal and print the same serial numbers. Today you can buy foilcal replacements from third parties, w/o the serial number, but that are otherwise identical.

AR and probably most others simply put the crossover on the back of the speaker box, so all you had to do was remove the drivers, pull out the stuffing, and then access the unit.

Polk's Monitor RTA 12 (not the later SDA model) had the crossover on top of the speaker cabinet, covered by a small grill cube. Those early Polk Monitor series speakers were quite good sounding, and could be considered excellent value for the money.

The good thing about the TWs -- by the time I had a pair, the foam was so deteriorated it was a given that it had to be removed, anyway. The biggest problem with them is that the drivers are glued in -- and in the early models, the top and bottom plugs are glued on, as well -- and, of course, the 'cabinet's Sonotube and particle board.
My first modern hifi loudspeakers were a pair of Polk "Monitor 7" (more accurately, Monitor Series Model 7A) that I bought, as demos, in 1978, still have, and am in no hurry to divest myself of. At the time, they were unbeatable for the $ in terms of sound quality, and they're still quite pleasant to listen to.

 

[fpitas]

You won't see that at my house

Well... maybe on an off-day...

Looks like an 811. You can do whatever you please with that

 

[restorer-john]

At least with the DCM drivers, all the factory installed ones have orange chalk marks on the cones/tweeter plate so you can tell if they are original.

 

[mhardy6647]

Looks like an 811. You can do whatever you please with that

I thought I had a photo of that Pyle abomination on a 511B (which is what I really wanted to post, just for you! ) but this is the only photo I found on Flikr. I think that's actually an EH500-2 the Pyle's bolted to... but I am not sure. I did have those drivers on the pair of 511Bs I used to have -- so there's probably a photo somewhere.

EDIT: Nope -- that IS a 511B! That's the one with the ear chewed off.

 

[fpitas]

I thought I had a photo of that Pyle abomination on a 511B (which is what I really wanted to post, just for you! ) but this is the only photo I found on Flikr. I think that's actually an EH500-2 the Pyle's bolted to... but I am not sure. I did have those drivers on the pair of 511Bs I used to have -- so there's probably a photo somewhere.

Oh well, 811s are ok too. In the 70s a friend bought an Altec kit with 411 woofers, 802s and 811s. We built sealed boxes and made speakers. Not bad. 802s are smooth enough, but you don't get the magic of the 288.

 

[fpitas]

I thought I had a photo of that Pyle abomination on a 511B (which is what I really wanted to post, just for you! ) but this is the only photo I found on Flikr. I think that's actually an EH500-2 the Pyle's bolted to... but I am not sure. I did have those drivers on the pair of 511Bs I used to have -- so there's probably a photo somewhere.

EDIT: Nope -- that IS a 511B! That's the one with the ear chewed off.

That is a scruffy looking 511, for sure.

 

[mhardy6647]

That is a scruffy looking 511, for sure.

Rode hard and put away wet -- as they say.
The other one was prettier - and in an original Altec (Anaheim) carton - but the price for the pair was excellent.

 

[normanj8129e]

Here's pictures of my Mod 1 s/n 2 speakers with upgraded drivers.

 

[Canuck57]

I had a pair of DCM Time Frames 350, they sounded quite good, strong bass from what I remember. I suffer from Vintage Speaker Acquisition Syndrome (VSAS) just like mhardy6647

 

[mhardy6647]

Here's pictures of my Mod 1 s/n 2 speakers with upgraded drivers.

Isn't that, like, a tw7?
So many drivers...

 

[dogberry]

I've had to have my Quad 2905s out of service to have a couple of panels replaced during the last year. Each time I took my old TimeFrame TF700s out of the attic. When I bought them in, what?, 1989? they were said to be uncoloured like electrostatics. Well, they're no electrostatics! But after an hour of so of listening I'm thinking to myself that I like these speakers and could live with them if my Quads ever become too expensive to repair.* A little time lets us quickly forget the sound we had before. They aren't as clear, detailed or quick as the Quads, but they are musical. Some time during their working like a large and fat Burmese cat wrecked the covers, so if I ever did use them I'd cut the speaker sock off, scrape off the degenerated foam, prime and paint them and use them naked. No cats or kids any more.

*Probably not an issue, as the tech and I made up a preventive technique that should stop the panels from shaking themselves loose and being able to arc.

 

[DavidMcRoy]

I've had to have my Quad 2905s out of service to have a couple of panels replaced during the last year. Each time I took my old TimeFrame TF700s out of the attic. When I bought them in, what?, 1989? they were said to be uncoloured like electrostatics. Well, they're no electrostatics! But after an hour of so of listening I'm thinking to myself that I like these speakers and could live with them if my Quads ever become too expensive to repair.* A little time lets us quickly forget the sound we had before. They aren't as clear, detailed or quick as the Quads, but they are musical. Some time during their working like a large and fat Burmese cat wrecked the covers, so if I ever did use them I'd cut the speaker sock off, scrape off the degenerated foam, prime and paint them and use them naked. No cats or kids any more.

*Probably not an issue, as the tech and I made up a preventive technique that should stop the panels from shaking themselves loose and being able to arc.

I have a similar experience when I crank my c. 1970s Time Windows ("Improved", Generation 1) that do background service in the living room. They are definitely colored (but I never met a speaker that doesn't require bass "room correction" anyway, so why not just touch up everything else with the DSP as best you can while you're at it?) and they aren't as clean and detailed as my Acoustat SPECTRA 1100s or my Tannoy System 12 DMT monitors. And the Time Windows' imaging intentionally exaggerates soundstage width at the expense of focus or specificity, so they're a no-go for use in a surround system...except as a surround channel speaker. But they remain fun, engaging and endearing. And your Time Frames do have decent imaging up their sleeves, to boot, and those incredible Vifa tweeters that my very early Time Windows lack.

 

[WIJ]

Does anyone here have any opinion on the DCM Time Window vintage speakers? I was in a hi-fi store and heard them playing quite by accident and was amazed at the sound. I had gone to hear some restored Ohms and the DCMs killed them, especially for orchestral music. These were just the original 1 model and some prefer the 1a ones. I don’t have particularly sophisticated taste in speakers and am extremely pleased with my Larsen 6.2s which have come under criticism here. The DCMs would be for my second system. I was thinking about Revels but the significant other would blow a gasket at the expense. As luck would have it a totally restored pair of the DCM 1a model is available ten miles away.

TW 3’s and 7’s were supposed to be the pinnacle and even better than the 1’s or 1a’s. Also the TW3 had coaxially mounted tweeter on one of the two drivers, one being 6.5 and the other driver was a larger 8.5” woofer. The speaker had two ports, one on top of the other on the same side or face of the speaker. A larger speaker than the earlier renditions. Here are the specs for the TW3, according to info from a different forum:
24-20,000 Hz Frequency response
89 [email protected] 1meter Sensitivity
Power 5-400 watts Usable power range
8 Ω Nominal impedance
2-3/4" tweeters coaxially mounted soft dome
1-6.5" midbass polypropylene/butyl rubber surround
1-8" woofer butyl rubber surround
3-way time and phase equalized with electronic speaker protection
Folded transmission line with front port
Solid oak in black or walnut finish
45 pounds each.

 

[hulia]

hi- i have a pair of DCM time windows that i got around 1978. about ten years ago i had some of the speakers and the covering replaced and now i am thinking that they didn't put the right ones in there because one of them sounds almost like a woofer is blown. i would like to find someone who specializes in them to look them over and fix them to original if possible. can someone point me in the right direction? i live in the asheville, north carolina area. and yes, they sounded amazing when i got them. serial numbers 41332, 41333.