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Koss CM Speaker Series Listeners' Review

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Deleted member 133

Guest
At The Great Canadian GTG 1.0 held this week, I took the opportunity of having a number of guests / potential listeners in hand to conduct a listeners' review of the Koss CM Series of speakers - and specifically the Koss CM/1030, CM/1020, and CM/1010.

To the best of my knowledge, nobody has ever set up all three speakers in a room before, with perhaps the exception of some store or OEM space. I certainly d6n't know of any published listeners' reviews like the ones that will appear here. Given the ongoing interest in these speakers (as evidenced by the large number of people that continue to contact me at junk666email@hotmail.com) I'm hoping this proves to be a valuable bit of info for the curious and fanatic alike.

For those who have not read my other posts about these speakers here are the hard facts:

CM/1030: 4-way, 74lbs, 29 Hz - 19 kHz (-3 dB points), 96 dB SPL efficiency.
CM/1020: 3-way, 60lbs, 31 Hz - 18.5 kHz (-3 dB points), 95 dB SPL efficiency.
CM/1010: 2-way, 44lbs, 32 Hz - 18.5 kHz (-3 dB points - with brass mass on passive radiator), 92 dB SPL efficiency.

They were set up in my (untreated) living room. In at least partially keeping to the "vintage" theme of these speakers, electronics included an old NAD 2150 stereo power amp (50 w/ch), Hafler DH101 pre-amp, brand new Sony BDP-S390 Blu-ray / DVD / SACD player, and a Dynex 15" LED flat panel. They were powered through a high-quality 4-way speaker switch so that quick changes between speakers could be made. Shown below.

Over the course of the GTG, PaulyT, Razz and Dude (Hoops) took turns, with a selection of music of their choosing, to spend time listening to all three speakers.

My own views of these speakers are well-known and I won't repeat them here. I'll let these three fine Forum members post their reviews / comments at their leisure, along with any pics that they happened to take.

Please hold off on any comments / questions etc. until all three have done so.

This one shows the set-up with grilles on.

http://www.flickr.com/photos/10665238@N06/7645922498/in/photostream

This one shows the set-up with grilles off.

http://www.flickr.com/photos/10665238@N06/7645930350/in/photostream

The next two close-ups, grilles off.

http://www.flickr.com/photos/10665238@N06/7645939482/in/photostream

http://www.flickr.com/photos/10665238@N06/7645947118/in/photostream
 
Some pics... my review will come shortly.

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aDSC0153-L.jpg





aDSC0154-L.jpg





aDSC0155-L.jpg





Simple stereo amp with a switch to select which speakers to use.

aDSC0156-L.jpg
 
So I have been waiting patiently :angry-tappingfoot: :angry-tappingfoot: :angry-tappingfoot: for these reviews.....................
 
:angry-tappingfoot: :angry-tappingfoot: :angry-tappingfoot:
Pray we don't go through this when Tom's new subs are "passed around"........still waiting :angry-tappingfoot:
 
Man they just don't make em like that any more. They even have brass built in, flush mount handles. Fancy!
 
I'm still traveling, in Niagra Falls right now - my review won't be up until after I get home, probably sometime Monday.
 
So, getting to my review... I used four tracks, selected from the relatively small collection I brought with me to listen to in the car, maybe not the most diverse but as decent a sampling of styles as I could come up with from material I'm familiar with (as opposed to choosing something I don't know as well from Jeff's enormous library) :

  • Tierney Sutton, Berne's Tune, from the album Unsung Heroes
  • Mumford & Sons, Roll Away Your Stone, from Sigh No More
  • Joe Bonamassa, India/Mountain Time, from Live from Nowhere in Particular
  • Hilary Hahn, Die Shatzbarkeit, from Bach Violin and Voice

Yeah the setup was maybe not ideal with an untreated smallish room, with speakers not in the same location during listening - yeah we coulda moved them around but the ease of switching immediately from one speaker to another trumped the notion of testing them in the same physical configuration. All the booster/dampener controls on the LF/MF/HF on the speakers was set to neutral, as you can see in the pics. (Note this is NOT the case in Jeff's main HT, I noticed, maybe Jeff can explain why he chose the configuration he did...) I tried to move the listening point forward/backward when switching speakers to get some rough idea of the best sound and best stereo separation. I listened to all of them with grills off after doing some brief listening tests to determine whether I preferred grills on or off. Yes there's an efficiency difference between the speakers, so I won't claim to be uninfluenced by that factor, but I did not bother to try to change the volume when switching speakers, that would be too much trouble and a bit arbitrary without some calibration.

I started with the 1010. I thought it had a pretty decent midrange, acoustic instruments and vocals were smooth, dynamics pretty decent. However, I wanted more in the HF, and I thought the LF was a bit muddy - e.g. an electric bass line was not extremely clear.

Moving up to the 1020, I thought the bass output was actually a bit less overall, but much cleaner and tighter, I could hear more detail in the low instruments. Ok yeah not subwoofer range but I wasn't testing LFE, the lowest sounds in my tracks would be the acoustic and/or electric basses. The HF was slightly improved over the 1010, with a bit more detail and "spacious" feel to it. Again I hesitate to draw too firm a conclusion in that sense because of the difference in physical separation of the speakers. However, on continued listening, I found that the voicing of the upper MF and lower HF range to create a "honkiness", that brought out certain ranges like higher male vocals or some trumpet lines in a way that was fatiguing. I would venture that that might be solved by a bit of EQ (and/or twiddling the boost switches on the speakers), but in the configuration we used here, I would not want to listen to these speakers at even moderate volumes for any great length of time, as it became unpleasant. Yeah I know that's a bit vague, but I'm trying to factor in my emotional response to the sound and the overall impact of the music, as I do with any speaker. I can't justify it any other way without doing some sort of RTA at the minimum, which we did not attempt.

Finally, the 1030. Here I immediately found some relief in the voicing, the balance was smooth overall and the detail quite good. A little more in the MF than the 1020, but maybe a little less HF. Bass response was similar overall to the 1020, I didn't notice a large difference there. To my ears, the 1030 are clearly the best of the three.

I then played around with switching back and forth from one model to the other, trying to solidify these general impressions. Overall the voicing of the 1030 is more similar to the 1010, though the 1030 is obviously more efficient (e.g. louder without changing the volume knob) and more detailed, especially in the LF. The improvement in detail in 1030 vs 1010 is quite apparent. OTOH, the difference in detail of the 1030 vs 1020 is not as great, I thought the dynamic response was more similar, but there's the voicing issue that made me dislike the 1020.

So, that's the three models with respect to each other. The obvious next question is, how do these compare to other speakers I've heard? I won't even attempt to try to put them in some sort of rating scale, but I would say that the 1010 are fine as a casual listening speaker, they have a decent sense of scale even though they're the smallest physically, but the lack of detail makes them just "okay" overall - good but not something I'd go out of my way to buy.

For the reasons above, I would not put the 1020 a whole lot higher on my list, at least not before attempting to see if that voicing issue could be altered more to my liking. (Note that I'm not claiming it would be more or less accurate... I don't have enough information to make a hard conclusion like that.)

The 1030, even a humble non-stacked single pair :laughing: , is a pretty darn good speaker. Especially given the general price I know Jeff paid to purchase and fix these up; as full-range speakers (that is, not trying to throw a sub into the mix), I doubt much in that price range would be able to touch them. However, I think their biggest weakness is in the HF response. I thought the tweeters just didn't quite measure up to some material, things with little high-hat or cymbal ticks, or even tambourine, snare hits, the aspirations in vocals - the little "click hiss" types of details that are hard to pick up, especially if they are layered in the mix among a lot of other sounds (which may be a lot louder). To me one of the big measures of the quality of a speaker is the ability to reveal these details, and while the 1030s were pretty good, they didn't reach the level I've heard in other - more expensive - systems. I think this is directly connected with the stereo imaging, which was also good but not great, but there we also have the issue of acoustics and reflections and such to confuse the matter; though since I felt the same about the 1030 in the more treated HT, I think maybe that's a reasonable assertion, that the dynamic detail needed to reveal these little sounds is the same thing that constructs an accurate soundstage/image. I don't have any data to back up that connection, but it's something I've thought a lot about over the years, and I think applies both to speakers and headphones.

So, these are great speakers and a lot of fun to listen to. They would definitely classify as large-scale full-range speakers, especially when stacked! Even Batman's Dyn S5.4 don't give as huge a soundstage presentation. I'm not talking about volume, just the size of the image they project at least when sitting relatively close. It's great for a rock band because it gives the feel of being in a large concert venue. For a jazz trio or a classical vocalist, it's so big it's a little disconcerting - a saxophone that feels like it's 4 feet tall, a 10' tall vocalist, etc. :laughing: But that's probably more a matter of room size and listening distance; I can't say what it'd be like to replace Bat's dyns with the 1030 in the batcave... maybe at the next GTG. :D

Thanks Jeff, for providing this opportunity! It was a lot of fun, and I look forward to hearing how the other guys who evaluated these rip my opinions to shreds. :laughing-rolling:
 
Just what Tom and Zing said.....................thanks for taking the time to give such a comprehensive review. :handgestures-thumbup:

This is such a subjective hobby with so many variables with acoustics, equipment and recorded material.

It's amazing that we are not all crazy..... :teasing-tease:
 
Thanks Pauly. What an honest review. I would love to go visit Jeff's place & listen/share/ etc.
Didn't Jeff go through some replacing crossovers etc on these speakers? The speakers (tweeter etc) weren't replaced....right ?
 
As far as I know, Jeff had them reconditioned to like-new state, but nothing completely replaced with components different from the original. Jeff may comment further though...
 
My intention with this thread is to have independent reviews of these speakers posted for the benefit of all those so interested. I'll only chime in when asked. However I agree that Pauly has done a superb job in his review. A tough act for Russ and Jon to follow! :)

Pauly did remark about the settings of the frequency contour switches. I run all of mine "flat" - with but one exception: there is one pair (bottom speakers in the surround stack in the basement) where I've boosted things. The reason: the response from the treble and tweeter drivers is down on that pair. Equally. I suspect that an error was made by the shop when they were refurbished, because it's the only pair that sound any different from all of the rest. (I could never tell the difference between any of the other five pairs that I own.) In the next week or two I intend to run a few tests on them and if need be I'll take those stacks down (not any easy task for one person to do!) and take those two speakers back to the shop to be checked out. I've been holding off doing so for quite some time.

Barney: all of the crossovers have been refurbished. Typically this involves replacing all of the original resistors (their leads and internals corrode), and in about half the cases, some of the caps. (The last pair, which is the one in the living room, needed only resistors. And of course new switches: they all fail eventually.) A problem is that it is impossible to find exact replacements for the resistors. The shop can get the values right, but nobody makes them with as tight tolerances as the originals - or so I'm told. (I believe, with the one exception noted above, that every refurbished speaker sounds like it just came from the factory.) All of the drivers are original. There are no replacements for the mids and woofers. And while some claim to have found a replacement for the tweeters that is a match, I have no firsthand experience with any. I have a small supply of used drivers that I've salvaged from other speakers for my own future needs. I have salvaged and given away dozens of drivers to other Koss CM fanatics over the years. It's now been close to two years since I salvaged any. In many cases where people have contacted me because of a failed driver, it's really the crossover that's at fault. Driver failures are very rare. Every crossover needs refurbishing by now.
 
thanks Jeff & Pauly........but just me.....with all speakers it seems to me....is the advancement of tweeters & mid-drivers and it may also be that recordings are now far better..meaning the equipment used to "break-down" the Upper freq's etc. & more attention is spent on this info (rather than the "exciting mid freq's" ) and possible the equipment sending reading/sending the info has changed (SH will kill me for suggesting that...).
Kinda like our paradigm 20's v2's............they are sweet & we love em..........whats out there now just makes you shake your head..........it can be better......... :music-listening:
 
Barney said:
thanks Jeff & Pauly........but just me.....with all speakers it seems to me....is the advancement of tweeters & mid-drivers and it may also be that recordings are now far better..meaning the equipment used to "break-down" the Upper freq's etc. & more attention is spent on this info (rather than the "exciting mid freq's" ) and possible the equipment sending reading/sending the info has changed (SH will kill me for suggesting that...).
Kinda like our paradigm 20's v2's............they are sweet & we love em..........whats out there now just makes you shake your head..........it can be better......... :music-listening:
Click to expand...
The Koss CM Series of speakers were made (roughly) between 1978 and 1984. I would be shocked if there had not been a progression of the technology since then.

However I still believe that a fully-refurbished pair of Koss CM/1030s (~$1000 all in - assuming you have to first buy a used pair) cannot be touched by anything comparable in price. While "different", I prefer them over (some) speakers costing (new) many times that.

By the way, when all three reviewers have posted their reviews, I intend to email them copies of all known reviews (hi-fi pubs) of these speakers. If anyone else would like a copy, PM me your email address and I'll include you as well. Make sure that your email inbox can handle a pretty good size worth of attachments. (Hotmail works - for example.)
 
MatthewB said:
I have to ask is that a yellow thumb tack in the 1010 woofers?
Click to expand...
Good question Matt.

It's brass.

It's removable.

It's screwed to the passive radiator.

Unlike the 1030 and the 1020, the 1010 uses a passive radiator instead of port(s).

The weight allows you to choose one of two "damping" profiles.

"On" yields the flattest, deepest bass. "Off" raises the low frequency extension and adds a "bump" in the response. I prefer the former.

By the way, the surrounds on the passive radiators of a lot of 1010s deteriorates - including mine. I had mine re-done by SpeakerMart a couple of years ago. It took them a long time to exactly match the mass / stiffness of the originals and I love the end result.
 
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