Problem with Markbass combo CMD 121p

Mister_argentum · #1 08-30-2011, 04:24 AM

Hello Everybody,

I am new to this forum so please let me know if I am posting in the wrong category.

I have a problem with my markbass combo and I wanted to know if others experienced the same issue. The combo is 7 months old and until now everything was fine.

The problem is that there is a kind of noise (a buzz) coming out from the tweeter. Is like if a lot of air was coming out from the piezo tweeter.

I checked with other basses, jacks, volumes, eq, etc but the noise persists. It is specially audible is the combo is right pointing at me.

At the shop they said everything is fine. Can anyone tell me if this happened to them?

**JxBass** · #2 08-30-2011, 04:58 AM

I owned the CMD 121P and CMD 151P combos. The biggest drawback to those combos, IMO, is the piezo tweeter. "Hissy" is the best description of what they sound like to me.

On the other hand, it sounds like yours was fine for months and something has changed?

nottswarwick · #3 08-30-2011, 05:19 AM

I blew the tweeter in mine. Too much volume and fizz from my BDDI.

Got a replacement easy enough for not much cash though, and dead easy to fit.

C

Mister_argentum · #4 08-31-2011, 06:20 AM

Thanks for the reply guys and the quick feedback. I think I need to find a replacement, but the tweeter seems fine (as the technician in the shop told me).

In the meantime, I think I found an "easy cheap fix". I took away the grid and with the help of some glue I paste a little bite of textile (like the one that you have in some mics or recording devices) directly in the part of the grid in front of the tweeter.

This way the sound of the tweeter still passes but without the "Hiss" (I would definitely say it is Hissy, thanks JxBass!).

If somebody else is having this issue I recommend following the procedure above, no Hiss will be audible after this.

Mister_argentum · #5 08-31-2011, 06:25 AM

Quote:

Originally Posted by JxBass

I owned the CMD 121P and CMD 151P combos. The biggest drawback to those combos, IMO, is the piezo tweeter. "Hissy" is the best description of what they sound like to me.

On the other hand, it sounds like yours was fine for months and something has changed?

Yes, I think something has changed, in fact they needed to change a small component in the preamp (SMD of something, I do not remember the name of the part). They say it is fine now but I do not think so.

Maybe the tweeter is defective, I think I found kind of a fix (see above).

Thanks for the reply.

rodl2005 · #6 08-31-2011, 07:12 AM

I've a MB cab, a HR115 1x15" which has a compression horn/tweeter rather than the piezzo tweeter.
I bypassed the horn in mine. Simply wired the speaker directly to the input sockets. No soldering involved, just press in plugs.
So, if you didn't want the tweeter going at all in yours, that would be an option.
Does it HISS when the tweeter is turned down or off???
I'm assuming yours HAS a tweeter level control on the cab somewhere?

Mister_argentum · #7 08-31-2011, 08:49 AM

Quote:

Originally Posted by rodl2005

I've a MB cab, a HR115 1x15" which has a compression horn/tweeter rather than the piezzo tweeter.
I bypassed the horn in mine. Simply wired the speaker directly to the input sockets. No soldering involved, just press in plugs.
So, if you didn't want the tweeter going at all in yours, that would be an option.
Does it HISS when the tweeter is turned down or off???
I'm assuming yours HAS a tweeter level control on the cab somewhere?

There is no tweeter volume control in the MB combos, I think your solution is the best one. It is a tweeter issue.

For the time being I'll just stick with my quick fix, later on I'll be bypassing. It is a great amp but this tweeter can be a pain!

Thanks for the feedback.

DownLowJoe · #8 08-31-2011, 10:59 AM

I've had my Markbass 121p combo for 3 years and have had some hiss and buzz out of the tweeter from day 1. I think it is universal with these peizo tweeters. I mainly notice it when I practice at low volume levels. With the full band I never notice the hiss one bit. It is such an excellent combo that this hiss is something I just put up with. It tends to be a somewhat intermittent thing with my combo. It may not be present when I start practicing and then all of a sudden I notice it, then it stops on its own. Again it has been present for years and the tweeter works so I don't worry about it.

The one thing you can do to reduce the hiss is to turn up the VLE control(turn counter clockwise) which i believe cuts the high frequency and is essentially a tweeter attenuator. Sometimes reducing the treble on the guitar tone knob or reducing the treble on the preamp also helps. These maneuvers almost always get rid of the hiss when I am practicing.

nottswarwick · #9 08-31-2011, 11:01 AM

^^^^^ this.

Mister_argentum · #10 08-31-2011, 12:11 PM

Quote:

Originally Posted by DownLowJoe

I've had my Markbass 121p combo for 3 years and have had some hiss and buzz out of the tweeter from day 1. I think it is universal with these peizo tweeters. I mainly notice it when I practice at low volume levels. With the full band I never notice the hiss one bit. It is such an excellent combo that this hiss is something I just put up with. It tends to be a somewhat intermittent thing with my combo. It may not be present when I start practicing and then all of a sudden I notice it, then it stops on its own. Again it has been present for years and the tweeter works so I don't worry about it.

The one thing you can do to reduce the hiss is to turn up the VLE control(turn counter clockwise) which i believe cuts the high frequency and is essentially a tweeter attenuator. Sometimes reducing the treble on the guitar tone knob or reducing the treble on the preamp also helps. These maneuvers almost always get rid of the hiss when I am practicing.

Thanks a lot, I agree 100 % with you. Excellent combo but I have had already 2 small issues (this preamp thing and the hiss) in 6-7 months of intense use. It is a pity. It is so close to being the perfect combo!

Anyway I'll stick to my fix (It actually works) and bypass the tweeter later on. Next time I'd rather go for the Berlin, He's right about these tweeters.

As you mention, with the band is not noticeable at all. The problem was when I mic it to record some stuff, next time I'll go D.I. but is not the same thing!

VLE up and treble down help a lot as well.

JimmyM · #11 08-31-2011, 01:51 PM

Bypassing the tweeter and crossover doesn't work so well in those little Markbass combos. The speaker cuts off at a fairly low point, and has no high end to speak of when you bypass it. Plus it voids the warranty. Honestly, that's why I no longer have it. Much respect for Markbass...the heads are nice, but the cabs just aren't my thing.

rodl2005 · #12 08-31-2011, 04:41 PM

Wow! Didn't realize the combos don't have a tweeter control!
I wonder if my HR115's driver is like this?
Doesn't SOUND like it. I actually sometimes find it hard to tell which is the cab which has the horn bypassed.
Must take it to a speaker repair guy I know who's got the diagnostic equip. Then again, afaik my ears work ok ;-)