ok, so I just bought a pair myself (for $15 canadian). they're the same basic size/driver configuration as minimus 7s. however ALL wood veneer (real wood, ALL sides/edges). made in the late 70s/early 80s I'd say. 4" woofer, 1" soft dome tweeter.
it's obvious that the tweeters and woofer caps have been pushed in at some point and then pulled out again, but they all sound great so I'm ok with that (there are little wrinkles... can't do much about it now).
I've read all the stuff about M7 crossover mods, great stuff from those guys. was thinking I could do something similar for these babies.
sound is great, definitely mid heavy, but great, nice tweeter that isn't harsh at all, woofer is performing very well and is paper, bit of a curve to the cone, foam surround (recently refoamed), very solidly built inside (quite different from M7 woofers though). very light on bass but can take it great from tone controls and sounds good (if mid-bassy) like that, but I'm quite certain that I can improve the balance overall with some tweaking.
I opened them up (removed a woofer, these are permanently built speakers and you can't remove the front panel or anything). stuffed FULL of very high quality material, honestly it's like 1" thick super high density carpet underlay, folded over once, from top to bottom front to back of the cabinet. not much room for sound waves to travel in there.... was pressed up against woofer etc so tight I figured it might actually improve a bit of the bass level by opening that up a bit, but I don't want to actually cut it to remove it (I pulled it all out in one solid chunk through the woofer hole though... I'm now wondering if it's original or after market cuz it's like new...).
I had to pull it out to find the crossover (on back wall). the crossover makes the M7 stock one look like tinkertoy. it's got two inductors (of radically different values... odd) and at first glance two caps although I didnt' try to remove it to see values or how it's really wired. I'll have to do that though since I need to know what's going on before I can see what I can do to balance out the sound more.
I'm not big on adding eq or using tone controls if possible with speakers so I'm hoping this can be an improvable project.
With that bit of info I have a couple of theories about that xover:
- with one inductor being honestly fairly large (for such a tiny speaker), the other much smaller, my first instinct is: 1st order network between tweeter and woofer, also a 2nd order hpf on the bottom end of the woofer to make sure it doesn't get blown up by idiots (like me) who are turning up the bass to make it sound better and then cranking the amp.
- 2nd order network between tweeter and woofer with the woofer having a significantly lower cutoff point than the tweeter (sure doesn't sound like that though, plenty of smooth mids)
- 3rd order network cutting off bottom of tweeter with nothing on the woofer at all (or maybe a cap on the very low end of the woofer to prevent overloads of low bass).
we'll have to see - wierd to see such differently sized inductors though in a two way, especially of this minute size
drivers are top notch quality as well.
so I'm blown away with the high end, the middle is emphasized too much but still really high quality sound, and the midbass and lower are underemphasized imho. I'd like to alter the eq somewhat so will do some measurements and modifications to the crossover on one of mine to see if I can improve it (without spending much money... I'll try to use the inductors that are there already if I can).
these appear to be much higher quality speakers (in materials and overall planning at least, if not sound - hard to say since I have no M7s to compare with currently) than minimus 7s for example, which are also great and were likely the direct competition to these back in the late 70s/early 80s. 7s have those simple crossovers (no filter on the woofer and a 2nd order on the tweeter with other poor compromises as well) that are well researched here and improved upon by good brains on audiokarma, where I can see no financial compromises made in these koss speakers so far (but again, I expect improvements can be made based on the sound I hear).
I do wish that I had the m80s instead though with the dual woofers, would no doubt perform better in the bass region.
Taking that in stride I'll likely end up adding a third small inductor to this to lower the woofer's filter cutoff frequency a bit and otherwise will have to wait on guessing what changes to make until I've figured out exactly what the crossover is currently doing. But really that is all a guess - depends completely on what I find the current components are actually doing in the crossover.
I read a review of the m80 (same thing supposedly but 2 woofers) where the reviewer claimed it had no inductors at all and just 3 capacitors, two on the tweeter and one on the woofers. that seems really unlikely to me especially considering the 2 inductors in my m60 pluses (which are a cheaper model), so I expect there are two crossover boards in the m80 and he didn't notice as much, and maybe the filter cap wasn't doing what he thought it was on the woofers (might have been part of a zobel for example).
I'll update you more when I know more.
it's obvious that the tweeters and woofer caps have been pushed in at some point and then pulled out again, but they all sound great so I'm ok with that (there are little wrinkles... can't do much about it now).
I've read all the stuff about M7 crossover mods, great stuff from those guys. was thinking I could do something similar for these babies.
sound is great, definitely mid heavy, but great, nice tweeter that isn't harsh at all, woofer is performing very well and is paper, bit of a curve to the cone, foam surround (recently refoamed), very solidly built inside (quite different from M7 woofers though). very light on bass but can take it great from tone controls and sounds good (if mid-bassy) like that, but I'm quite certain that I can improve the balance overall with some tweaking.
I opened them up (removed a woofer, these are permanently built speakers and you can't remove the front panel or anything). stuffed FULL of very high quality material, honestly it's like 1" thick super high density carpet underlay, folded over once, from top to bottom front to back of the cabinet. not much room for sound waves to travel in there.... was pressed up against woofer etc so tight I figured it might actually improve a bit of the bass level by opening that up a bit, but I don't want to actually cut it to remove it (I pulled it all out in one solid chunk through the woofer hole though... I'm now wondering if it's original or after market cuz it's like new...).
I had to pull it out to find the crossover (on back wall). the crossover makes the M7 stock one look like tinkertoy. it's got two inductors (of radically different values... odd) and at first glance two caps although I didnt' try to remove it to see values or how it's really wired. I'll have to do that though since I need to know what's going on before I can see what I can do to balance out the sound more.
I'm not big on adding eq or using tone controls if possible with speakers so I'm hoping this can be an improvable project.
With that bit of info I have a couple of theories about that xover:
- with one inductor being honestly fairly large (for such a tiny speaker), the other much smaller, my first instinct is: 1st order network between tweeter and woofer, also a 2nd order hpf on the bottom end of the woofer to make sure it doesn't get blown up by idiots (like me) who are turning up the bass to make it sound better and then cranking the amp.
- 2nd order network between tweeter and woofer with the woofer having a significantly lower cutoff point than the tweeter (sure doesn't sound like that though, plenty of smooth mids)
- 3rd order network cutting off bottom of tweeter with nothing on the woofer at all (or maybe a cap on the very low end of the woofer to prevent overloads of low bass).
we'll have to see - wierd to see such differently sized inductors though in a two way, especially of this minute size
drivers are top notch quality as well.
so I'm blown away with the high end, the middle is emphasized too much but still really high quality sound, and the midbass and lower are underemphasized imho. I'd like to alter the eq somewhat so will do some measurements and modifications to the crossover on one of mine to see if I can improve it (without spending much money... I'll try to use the inductors that are there already if I can).
these appear to be much higher quality speakers (in materials and overall planning at least, if not sound - hard to say since I have no M7s to compare with currently) than minimus 7s for example, which are also great and were likely the direct competition to these back in the late 70s/early 80s. 7s have those simple crossovers (no filter on the woofer and a 2nd order on the tweeter with other poor compromises as well) that are well researched here and improved upon by good brains on audiokarma, where I can see no financial compromises made in these koss speakers so far (but again, I expect improvements can be made based on the sound I hear).
I do wish that I had the m80s instead though with the dual woofers, would no doubt perform better in the bass region.
Taking that in stride I'll likely end up adding a third small inductor to this to lower the woofer's filter cutoff frequency a bit and otherwise will have to wait on guessing what changes to make until I've figured out exactly what the crossover is currently doing. But really that is all a guess - depends completely on what I find the current components are actually doing in the crossover.
I read a review of the m80 (same thing supposedly but 2 woofers) where the reviewer claimed it had no inductors at all and just 3 capacitors, two on the tweeter and one on the woofers. that seems really unlikely to me especially considering the 2 inductors in my m60 pluses (which are a cheaper model), so I expect there are two crossover boards in the m80 and he didn't notice as much, and maybe the filter cap wasn't doing what he thought it was on the woofers (might have been part of a zobel for example).
I'll update you more when I know more.
Last edited:
