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PLEASE HELP amp distorts at low volume

S

Santino Orozco

Commercial User
Jul 14, 2019
10
0
#1
Hello everyone, I have seemed to run into an issue with my Mesa M3 Carbine 300-watt head. it seems when i turn up the volume to play live gigs the amp seems to distort but not in a good way, and its also not very loud when it does get to this distorting range, I thought it may have been the speakers but I doubt this and think its the head, I am a running a 400 watt Celestion pulse 15 with 3 unknown wattage seismic speakers and one seismic jolt 10 200 watt speaker, so I figured that the speaker would be able to handle the wattage of the head, I kind of suspect it may be a biasing issue but I am also not sure.

please respond ASAP thank you very much.
 
#3
I’m hoping that what you have is one 115 cabinet and one 410 cabinet, by your description. It will make troubleshooting easier starting with only one cabinet.
The Celestion Pulse 15 is an 8 ohms speaker.
You really need to find out what the other 10” speakers are, and what cabinet they are in.
 
#5
agedhorse said:
How are your speakers connected?

Are these commercially designed speakers?

What are the nominal impedances of the speakers?

Have you tried your amp with ONLY the 15" cabinet?
Click to expand...

I've wired the 4x10s to have an 8-ohm load, and then I daisy chain them to the 15 which also is an 8-ohm load which comes out to 4 ohm total to the head, also these speakers you can just buy, 3 of the 10s came out of an old cab I had and I had to buy a new one which is the jolt 10 so they're just normal speakers nothing crazy about them
 
#6
abarson said:
I’m hoping that what you have is one 115 cabinet and one 410 cabinet, by your description. It will make troubleshooting easier starting with only one cabinet.
The Celestion Pulse 15 is an 8 ohms speaker.
You really need to find out what the other 10” speakers are, and what cabinet they are in.
Click to expand...

it is a custom cabinet, 4x10s surrounding the Celestion 15, wired up to have a 4-ohm load to the head, the head is perfectly capable of handling this load as it says on the back "4 ohms preferred"
 
#7
So you've got 4 x 10" in the same cabinet as the 1 x 15"? We need a picture!
I can't imagine that being a successful design. Different sized speakers aren't typically happy sharing the same cabinet space. It's probably not wattage that causing the distortion but rather the speakers fighting each other.
 
#8
What is the measured DC resistance of the cabinet?

Do the drivers all share the same air space or is the 15” driver in its one air space?

Have you tested each driver separately?
 
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#9
abarson said:
So you've got 4 x 10" in the same cabinet as the 1 x 15"? We need a picture!
I can't imagine that being a successful design. Different sized speakers aren't typically happy sharing the same cabinet space. It's probably not wattage that causing the distortion but rather the speakers fighting each other.
Click to expand...

oh i see, i didn't really know of this, but yes they are in the same airspace, is there a way I could keep the same design but change up the internal design? like a box off the 10s separately on the inside of the cab? I've seen that been done on some HiFi speakers but not sure if it would help my situation.

also I've tried to do the same design as the mesa powerhouse 1000, just not sure how the inside looks on that cab so I may have missed something (ps this is an old pic I've already cleaned up the wiring and tried adding some foam for isolation and also added port tubes at the bottom)
IMG-8285.jpg
 
#10
agedhorse said:
What is the measured DC resistance of the cabinet?

Do the drivers all share the same air space or is the 15” driver in its one air space?

Have you tested each driver separately?
Click to expand...

not exactly sure I've been meaning to get a multimeter to check these things, will get back to you soon, but yes they do share the same air space, check my reply to the other guy for a pic of the inside of the cab
 
#12
abarson said:
So you've got 4 x 10" in the same cabinet as the 1 x 15"? We need a picture!
I can't imagine that being a successful design. Different sized speakers aren't typically happy sharing the same cabinet space. It's probably not wattage that causing the distortion but rather the speakers fighting each other.
Click to expand...
Also, it can be fairly loud, just not loud enough as I think it can be, I play harsh music like punk and metal mix, and it does get loud, just not loud enough to where people can hear me over the drums and guitars, but it does stay clean for a long time, i just think with 300 watts it should able to at least match them.
 
#13
Santino Orozco said:
Also, it can be fairly loud, just not loud enough as I think it can be, I play harsh music like punk and metal mix, and it does get loud, just not loud enough to where people can hear me over the drums and guitars, but it does stay clean for a long time, i just think with 300 watts it should able to at least match them.
Click to expand...
Well, this thread makes it sound like the PH1000 wasn't one of their stellar models.
Mesa Powerhouse 1000/1200 | TalkBass.com

I think you'd be better off building one 115 and one 410, each with a good design. It's a better plan than to fix something of dubious nature to start with.

One more thing: are you sure the 3 unlabled 10" speakers are Seismic Audio? The closest appears to be the Quake, which is designed for PA and not for bass. The Quake is rated for only 125 watts RMS versus 200 watts RMS for the Jolt.
Mixing different speakers, even if they are the same size, doesn't usually work for bass.
 
Last edited:
#14
abarson said:
Well, this thread makes it sound like the PH1000 wasn't one of their stellar models.
Mesa Powerhouse 1000/1200 | TalkBass.com

I think you'd be better off building one 115 and one 410, each with a good design. It's a better plan than to fix something of dubious nature to start with.

Oh, and tell the guitarist and drummer to play quieter (yeah, I know it's punk...).
Click to expand...


I see, I probably should have looked into these forums more before starting a project like this, although at least with mine I don't have as sound complaints, sounds nice and clear with really nice bass, but yea I will try to see if there is still anything I can do so I don't have to just scrap the whole thing as it took a bit to put together but in the end, if I still have volume issues I will probably trash it and get something else.

thank you very much for the help!
 
#15
Santino Orozco said:
I see, I probably should have looked into these forums more before starting a project like this, although at least with mine I don't have as sound complaints, sounds nice and clear with really nice bass, but yea I will try to see if there is still anything I can do so I don't have to just scrap the whole thing as it took a bit to put together but in the end, if I still have volume issues I will probably trash it and get something else.

thank you very much for the help!
Click to expand...
I will say the construction looks solid.
 
#16
abarson said:
I will say the construction looks solid.
Click to expand...

Thank you very much! also I was thinking if I boxed off the 15 on the inside do you think this would make any difference? good or bad? and when I mean box off I mean almost the whole length of the cab, I would leave a bit of room for air to move, I'm not an acoustic engineer or anything I'm sure that's obvious but I'm just kinda throwing ideas up in the air to possibly save this build.
thanks!
 
#17
Santino Orozco said:
Thank you very much! also I was thinking if I boxed off the 15 on the inside do you think this would make any difference? good or bad? and when I mean box off I mean almost the whole length of the cab, I would leave a bit of room for air to move, I'm not an acoustic engineer or anything I'm sure that's obvious but I'm just kinda throwing ideas up in the air to possibly save this build.
thanks!
Click to expand...
If you made the one box into three separate compartments that were sealed off from each other, you'd probably have a better result than what you have now. But it will never be anywhere near as efficient and good sounding as a cabinet that was designed to be what it is from the beginning.
 
#18
BlueTalon said:
If you made the one box into three separate compartments that were sealed off from each other, you'd probably have a better result than what you have now. But it will never be anywhere near as efficient and good sounding as a cabinet that was designed to be what it is from the beginning.
Click to expand...

The cab doesn't really sound bad per se but if I can make it any better I will, thanks for the advice!
 
#19
So here's the bitter pill, take the comments as intended, as a learning opportunity.

1. ANY different drivers (even the same size, but with different TS parameters) sharing a common air space will generally work poorly. This is because rather than a set of identical spring-air mass sources, you have different spring-air mass sources coupled together by the common air space. Rather than working together they fight each other.

2. You need to understand that the drivers work together with the air mass to create a tuned system. If you don't know the parameters of the drivers, you can't (easily) calculate how the drivers will perform. One of the parameters that is calculated is mechanical power handling, which is almost always less than the "rated power handling" of a driver... often less than 1/2.

3. The Powerhouse 1000 was a very popular cabinet in spite of its size and weight. Lots of big rock acts used them, Paul McCartney still uses them (at least pre-COVID). It does contain "separate" air spaces, and the cabinet is properly tuned to the drivers.
 
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#20
@Santino Orozco, I'm not sure how active you have been here, but just in case you don't already know, there are a few members here who represent the gold standard of information for the rest of us. @agedhorse is one of those.
 

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