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PostPosted: Sat Sep 22, 2012 7:27 pm 
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Hi, I picked up a free set of vintage Koss CM 1020 speakers today.
Supposedly, these are extremely nice/desireable speakers.
The cabinets were made by a grandfather clock manufacturing company in Zeeland MI, H.L. Hubbell Mfg. Co.

They work, but I believe the crossovers need to be rebuilt as 1 tweeter
doesnt work as well as the mid and tweeter switches as well.

Anyone know who can rebuild these crossovers for cheap ?
What would this cost ?

thanks

PS: Heres a vid I found on youtube of them.

http://www.youtube.com/watch?v=7xke8Uo8 ... ure=relmfu

sample pic
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PostPosted: Sat Sep 22, 2012 8:20 pm 
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Hi,

I wouldn't council spending any money on them. They date back to the late 70s and while the cabinets had some time put into them they were sold as an alternative to Cerwin Vega back in the day. They played loud but the quality was pretty poor. I'm all for preserving quality vintage gear but these would not fall into that category.

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PostPosted: Sat Sep 22, 2012 8:29 pm 
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rickho wrote:
Hi,

I wouldn't council spending any money on them. They date back to the late 70s and while the cabinets had some time put into them they were sold as an alternative to Cerwin Vega back in the day. They played loud but the quality was pretty poor. I'm all for preserving quality vintage gear but these would not fall into that category.


hmm, Ive read only good things about these speakers online...except yours.
Would $80 be too much to get these crossovers repaired ?

btw, I see London audio used to sell these back in the day ? :lol:

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PostPosted: Sun Sep 23, 2012 12:53 am 
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These were not particularly good speakers. Looked better than they sounded. I wouldn't spend the money on them.I have seen several sets of them over the years and the drivers usually have issues, not the crossovers. You have to take the drivers out of the cabinets and test them individually.


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PostPosted: Sun Sep 23, 2012 4:19 am 
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Google Jeff Mackwood - he has most of the available info on the CM-1010/1020/1030 speakers.
If you can find a current email for him he'll send you the specs.

I think he was/is a member on CAM....?

Got some crossover schematics for the 1030's from him a few years back.

The Koss's are a bear to work on, the switches plastic internals degrade into a runny goo and the only access to the inside (crossovers) is through the driver openings IIRC.

I found the tweeters to be particularly harsh. :(

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PostPosted: Sun Sep 23, 2012 5:29 am 
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I can comment on the CM 1030 a bit. The plastic switches broke very easily. The tweeters tended to blow at what I considered low levels.
And they really didn't play all that loud. At anything more than polite levels the sound became hard and glassy and the fuses would blow.
I kept them for a few years the sold them for a pair of KEF 103.2-much much better.

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PostPosted: Sun Sep 23, 2012 6:26 am 
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A timely discussion...as I am working on a deal for a set of CM 1030's...they are some distance away and haven't been able to make time to go fetch them (and large enough vehicle - 4 ft high!). Am thinking of paying $200 for a set that I'm told work well, cosmetically fair.

Meanwhile, I bought a set of Infinity RS III a's (8" woofers). Another big speaker, though not as deep. My plan was to try them both and sell off the set I liked the least. Haven't got the Infinity's home either, though that should happen next weekend.

In view of the significant negatives I read here on this thread, perhaps I should just pass on the Koss?

I'm getting the feeling that most if not all vintage speakers of this age (30 yrs +/-) really should have crossovers rebuilt if you really want them to sound good.

Would you agree that crossovers should be rebuilt as a general policy? Any exceptions/variables?

If so, I have also heard that the Infinity RS III's are easy to rebuild. Yes?

Anyone have thoughts on crossover rebuilds for Advent Large, Cambridge Audio A100, Polk Monitor 10's, and B&W midsize (not sure on model)? I have those as well. Necessary? Source of info and parts?

I'm an old guy whose ears are probably not "audiophile"...but I certainly like some speakers better than others, and am interested in finding other speakers that offer real good sound, plus high quality build and favorable ease/cost of repair.

So far Polk Monitor 10's (Peerless bullethole tweeter) are best I've heard (for my tastes - fairly diverse - blues, rock, jazz, classical, bluegrass, horns, tight bass, detailed sound) but I haven't spent a lot of time yet with other stuff. Getting some Advent Large soon to try and also a set of mid sized B&W's. Have heard Mission 710's and liked them. My Cambridge Audio A100's need refoaming so sound awful at moment, so not sure if I'll like them or not.

thanks in advance

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PostPosted: Sun Sep 23, 2012 7:11 am 
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If I had to pick I'd take the Infinitys. The Koss just aren't in the same league. A buddy has used a pair of Polk 10 for almost 20 years now and still loves them.
I've always liked the original Larger Advents. They are somewhat dated now but still sound resonably good. If you spend a few bucks on some upgraded parts their sound can be improved signficantly.
If you really want to have some fun try a stacked pair. There is all kinds of info on the best way to do this. I've done it with Smaller Advents and it was well worth the effort.

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PostPosted: Wed Mar 20, 2013 7:41 am 
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Sorry for coming so late to this thread but I think you'll understand why I felt a need to post.

First off I am always happy to help anyone who has questions / needs infomation about these speakers. You can reach me at junk666email@hotmail.com.

I currently own six pairs of CM/1030s, and one pair each of the CM/1020 and CM/1010. All have been professionally refurbished by SpeakerMart here in Ottawa.

If you google my name you'll find lots of places where I've posted extensively on these speakers - so I won't go into that level of detail about them. I will point you to this thread http://www.theaudioannex.com/forum/viewtopic.php?f=16&t=5245 about a listeners' test that I set up last year for a few of my visiting friends. While my opinions of these speakers may vary from theirs, I think that most listeners would agree with them.

Likewise while I disagree with many of the opinions presented in the preceeding posts within this thread, I can fully understand how one might have come to those conclusions. But for the record (since threads like this tend to get scanned by many more people who are simply trying to educate themselves about these speakers) I hope you won't mind me adding some specific comments (roughly in order of the previous posts).

You can tackle a Xover refurb yourself if you're reasonably good at such things. I would caution that I have seen some rebuilds that have turned otherwise good speakers into junkers when done improperly. ERSE is a good source for Xover parts. I can provide wiring diagrams for the 1030 and 1020. Contact me for these - and before you start - for more advice.

Up until recently I thought that there were no new replacement drivers available. That's still true for mids and woofers, however I now know of one source for both the 4 and 8 ohm version of the tweeter. (In the CM/1030 the treble tweeter and tweeter are different.)

It's actually very very rare for a driver to fail. It's almost always a case of Xover component failure. (Corroded resistors being the number one issue.) They're easy to test: lie the speaker on its back; remove the driver (leave the leads connected); touch your speaker leads directly to the driver's terminals (with volume all the way down); gently raise the volume and hear how they sound. Takes but a couple of minutes.

Access to the switches is through the tweeter opening. They get inserted from the inside and held in place by a knurled screw from the front. They (the originals) all fail (by snapping off at the root) eventually but I know of an inexpensive quality replacement. Access to the crossover is through the woofer opening.

This next point crosses over to "sound quality" and again I'm not trying to discount anyone's opinion. However, and as has been borne out in all existing trade publication reviews of the CM line of speakers, these speakers will play very loudly and very cleanly. I have had two fuses fail over the years because of what I think was simply old age. I have had a few others fail while doing a great job of protecting the speakers (like when an amp failed last year and sent a max power signal to a pair - for a brief time before the fuses went.)

In my main HT I run five "stacked" pairs of CM/1030s. I have heard nothing that has ever bested that set-up.

I hope that nothing posted in this thread has dissuaded anyone from at least considering to acquire, refurbish and enjoy these truly great speakers.

Jeff Mackwood
Ottawa

ps. I invite anyone who would like to listen to these to contact me to set up a time when you can drop by. My only caveat: I expect you to post your "review" (good or bad) afterwards somewhere, so that others can benefit from your opinion.

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PostPosted: Thu Dec 29, 2016 11:05 am 
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I know this is a very old tread, but I thought I would add my 2 cents worth. When I first got my CM-1020 speakers, I was a little disappointed in the sound. I even contacted Jeff for the schematic, as I was considering a xover upgrade. I was using them with what I thought was a very nice Sony TA-F444ESII amp.

But then, I tried them in a couple of different set-ups - Harman Kardon HK 775 monoblocks / PS Audio IVH pre amp/ Thorens TD 165. The 2nd system was the same Thorens, with a Sansui AU-519. There was a night and day difference in the sound quality of the Koss'. They embarrassed a nice set of JBL L36's.

As all speakers will sound better when played with a good source, this seems especially true with these Koss speakers - they are so accurate they will be unforgiving with a so-so source. My advice is to try them with a good quality amp with a bit of punch, that likes a 4 ohm load, and these speakers will come alive, and sound as beautiful as they look.


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PostPosted: Thu Dec 29, 2016 11:27 am 
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I believe the tweeters are Philips Deforest. They have many versions, pull the tweeters and check the numbers on the back.

In 1984, my first set of speakers used the same tweeter, but with a round case.

http://www.ebay.ca/itm/281897561268
http://www.ebay.com/itm/Philips-545-MFB-Tweeters-/302176882758
http://www.ebay.ca/itm/Philips-AD-01624-T8-Vintage-Tweeter-Tube-Amp-Era-Speaker-2422-257-3316-3-5-2-/152079403385?hash=item2368a38979%3Ag%3ACbIAAOSwiYFXJ46L

Q Components has a similar Goldwood.
https://mcbrideloudspeaker.com/Goldwood ... tle&page=2

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Ohms

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PostPosted: Thu Dec 29, 2016 12:04 pm 
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AudiOhm wrote:
I believe the tweeters are Philips Deforest. They have many versions, pull the tweeters and check the numbers on the back.

In 1984, my first set of speakers used the same tweeter, but with a round case.

http://www.ebay.ca/itm/281897561268
http://www.ebay.com/itm/Philips-545-MFB-Tweeters-/302176882758
http://www.ebay.ca/itm/Philips-AD-01624-T8-Vintage-Tweeter-Tube-Amp-Era-Speaker-2422-257-3316-3-5-2-/152079403385?hash=item2368a38979%3Ag%3ACbIAAOSwiYFXJ46L

Q Components has a similar Goldwood.
https://mcbrideloudspeaker.com/Goldwood ... tle&page=2

Regards
Ohms


An ex-Koss factory employee swears up and down that the tweeters were Peerless and the mids and woofers were made by Heppner. The cabinets were made by a grandfather clock manufacturing company in Zeeland MI, H.L. Hubbell Mfg. Co


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PostPosted: Thu Dec 29, 2016 12:13 pm 
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After further investigation, 11-5097 is stamped on the back of the 1020's.

They sure look like the Philips drivers...

Regards
Ohms

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PostPosted: Thu Dec 29, 2016 12:39 pm 
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AudiOhm wrote:
After further investigation, 11-5097 is stamped on the back of the 1020's.

They sure look like the Philips drivers...

Regards
Ohms


My source says that the 1020 tweeter (and the 1030 supertweeter) are the identical Peerless 810665 4 ohm 1" tweeter with a Koss specific front bezel/diffuser. Incidentally, this is the same tweeter (in 8 ohm form) which was modified for use in the Paradigm Studio 20, 20 v.2, 40, 40 v.2, 60, 60 v.2, 80, 80 v.2, 100 and 100 v.2 speakers and in the Polk SDA and RTA 12, Monitor 4, 5a, 5jr, 7B/7C and 10/10A.


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PostPosted: Thu Apr 05, 2018 4:43 pm 
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London Audio Ltd wrote:
Hi,

I wouldn't council spending any money on them. They date back to the late 70s and while the cabinets had some time put into them they were sold as an alternative to Cerwin Vega back in the day. They played loud but the quality was pretty poor. I'm all for preserving quality vintage gear but these would not fall into that category.

Just a touch better then vega's or by a country mile.


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