Disabling or replacing piezo tweeter in MarkBass CMD121P combo?

[will33]

What does this crossover look like?

It's probably just a resistor for the peizo. Even if it's more than thst, just disconnecting the whole works and wiring the woofer straight to a jack will take the tweeter out of the equation and allow the woofer to play your whole sound. No problems with impedance or adding cabinets. Only question is whether or not the woofer alone is bright enough for the tone you want. Only you can answer that after you've tried the mod, which is completely reversable.

If it's too dark that way and you need the tweeter back, a small, one band parametric eq would let you notch out the nasty part without killing your whole topend.

 

[The Bass Clef]

It is safe to do it, but I did it when when I had one and discovered that there are absolutely no highs at all without it. Quite honestly, I think there's a response hole between the woofer and tweeter. Your best bet is to use the VLE to tame down the tweeter. You could possibly replace it with a better tweeter, but since it's only a little 1" tweeter, I wouldn't expect miracles.

I know this thread is old, but for the sake of information, I’m pretty sure that the more recently made CMD 121P combos must have gone through a little change since the one that you had years ago Jimmy. I just picked up an Indonesian-made one (from 2014) off the classifieds here, and the first thing I noticed was that nasty hissing tweeter. I looked online to see if that was “normal” (which it is for this amp) and if I could just disconnect it. I found out it was safe to do, but I also saw your post above about it having no highs at all afterwards, so then I figured I’d just have to live with it and use the VLE to get rid of the ugly tweeter noise.

The problem was, while the VLE did get rid of the tweeter ugliness, I also found that it had a bit of a negative effect on my overall tone - I was muddier and starting to get lost in the mix now. So I researched a little more, and found several posts from people who disconnected their tweeter and said it was way better now. That convinced me to try it out, so I pulled the wires off mine and I found that my 12” main speaker is most defintiely operating full range. I do have to crank the “High” EQ knob on the amp now if I want to get more of the crispy highs, but they are there, and at least now I’m cutting through the mix again (the VLE is turned back down to where it isn’t making me sound muddy anymore).

Another thing to mention... I didn’t even bypass the crossover like I read many others did. I found a couple posts saying that the CMD 121P doesn’t really have a true crossover, it’s really just a high pass filter for the piezo, and the main woofer is wired full range from the factory. And I found this to be the case with mine.

So... now I’m thinking maybe the older combos actually had a true crossover in them (that cut off the highs to the 12”, as well as cut off the lows to the tweeter) that would have needed to be bypassed. That would explain why your combo didn’t get the full range to the 12, and mine did. Did you ever try bypassing the crossover, or did you just disconnect the tweeter? It seemed like you enjoyed the VLE turned up, so maybe it wasn’t worth the effort for you to dig in there and bypass it. I know you’ve moved on from this amp long ago Jimmy, but for future readers, I figured I’d let em know that disconnecting my tweeter made it a way better amp.

 

[JimmyM]

I know this thread is old, but for the sake of information, I’m pretty sure that the more recently made CMD 121P combos must have gone through a little change since the one that you had years ago Jimmy. I just picked up an Indonesian-made one (from 2014) off the classifieds here, and the first thing I noticed was that nasty hissing tweeter. I looked online to see if that was “normal” (which it is for this amp) and if I could just disconnect it. I found out it was safe to do, but I also saw your post above about it having no highs at all afterwards, so then I figured I’d just have to live with it and use the VLE to get rid of the ugly tweeter noise.

The problem was, while the VLE did get rid of the tweeter ugliness, I also found that it had a bit of a negative effect on my overall tone - I was muddier and starting to get lost in the mix now. So I researched a little more, and found several posts from people who disconnected their tweeter and said it was way better now. That convinced me to try it out, so I pulled the wires off mine and I found that my 12” main speaker is most defintiely operating full range. I do have to crank the “High” EQ knob on the amp now if I want to get more of the crispy highs, but they are there, and at least now I’m cutting through the mix again (the VLE is turned back down to where it isn’t making me sound muddy anymore)... And the best part - no more nasty highs and hiss!

Another thing to mention... I didn’t even bypass the crossover like I read many others did. I found a couple posts saying that the CMD 121P doesn’t really have a true crossover, it’s really just a high pass filter for the piezo, and the main woofer is wired full range from the factory. And I found this to be the case with mine.

So... now I’m thinking maybe the older combos actually had a true crossover in them (that cut off the highs to the 12”, as well as cut off the lows to the tweeter) and that could explain why your combo didn’t get the full range to the 12 - it need to be bypassed, and mine didn’t. Did you ever try bypassing the crossover, or did you just disconnect the tweeter? It seemed like you enjoyed the VLE turned up, so maybe it wasn’t worth the effort for you to dig in there and bypass it. I know you’ve moved on from this amp long ago Jimmy, but for future readers, I figured I’d let em know that disconnecting my tweeter made it a way better amp.

Well that's good to know if they did fix that. I honestly can't remember if I bypassed the crossover network or not. I may not have. I think I decided it was a PITA to do it.

Let's put it this way...I tolerated the VLE doing the highs cut more than disconnecting the tweeter But I actually thought the VLE was the best thing about Markbass amps, and I wanted something similar in a tiny effect pedal, and that led to the Broughton Low Pass Filter, which along with the subsequent High Pass Filter and the combo HPF/LPF are a couple of Josh's best selling pedals. I really didn't hear the VLE acting on the amp. I guess it's possible but I don't remember it that way.

 

[The Bass Clef]

Well that's good to know if they did fix that. I honestly can't remember if I bypassed the crossover network or not. I may not have. I think I decided it was a PITA to do it.

Let's put it this way...I tolerated the VLE doing the highs cut more than disconnecting the tweeter But I actually thought the VLE was the best thing about Markbass amps, and I wanted something similar in a tiny effect pedal, and that led to the Broughton Low Pass Filter, which along with the subsequent High Pass Filter and the combo HPF/LPF are a couple of Josh's best selling pedals. I really didn't hear the VLE acting on the amp. I guess it's possible but I don't remember it that way.

I like the VLE too, just more in moderation than what I needed to get rid of that nasty tweeter. Now that I’m using the VLE for the actual effect that it is, it sounds great. And this little combo is now perfect for the hole in the wall dive bar gigs (that I don’t want to lug my Ampeg rig to). Even with all the new amps that have come out since the CMD, I still don’t think anything comes close to packing the punch at 26 lbs. that this little thing does!

 

[JimmyM]

I like the VLE too, just more in moderation than what I needed to get rid of that nasty tweeter. Now that I’m using the VLE for the actual effect that it is, it sounds great. And this little combo is now perfect for the hole in the wall dive bar gigs (that I don’t want to lug my Ampeg rig to). Even with all the new amps that have come out since the CMD, I still don’t think anything comes close to packing the punch at 26 lbs. that this little thing does!

It's a good little combo...I thought it was good enough to buy one so I must have liked it Ultimately it just wasn't my thang.