Bandogmusic

Guitar speaker matrix switch design and build help.
« on: February 19, 2020, 04:56:52 PM »
Hey Guys,

This might be weird or super easy... you tell me.

What I'm trying to do:

I have an old Marshall 4 x 12 cabinet that I have stocked with 4 different speakers. All of them are 8 Ohm and 90 - 100 watt. This is a rig exclusively for recording and re-amping.

I'd like to be able to to send signal out of a guitar amp to any 1, 2, 3, or 4 (All speakers).

I've considered trying to find or build some sort of ABCD switch but I don't know how something like this would affect the signal.

I'd love to hear any issues with this idea or other novel ideas for how to pull this off.

Thanks guys!

Ben


squarewave

Re: Guitar speaker matrix switch design and build help.
« Reply #1 on: February 20, 2020, 02:10:21 AM »
It's not that simple. The number and arrangement of speaker connections depends on parallel and series impedances and has to match the amp impedance. Two 8 ohms speakers in series is 16 ohms. Two 8 ohm speakers in parallel is 4 ohms. So if the amp is say 8 ohms for example, neither of those arrangements for two speakers will work. Three is also a problem.

JohnRoberts

Re: Guitar speaker matrix switch design and build help.
« Reply #2 on: February 20, 2020, 09:02:52 AM »
You generally do not want to switch speakers connected to vacuum tube amplifiers while powered up.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

tony hunt

Re: Guitar speaker matrix switch design and build help.
« Reply #3 on: February 20, 2020, 10:07:23 AM »
There was a 4-way cab switcher from Palmer: PCABSW4X.
I used it with an ancient Vox 4x12 cab which I loaded with different vintage alnico speakers.

It works for one speaker at a time, but not all four together.
The unit is conceived for use with tube amps and you will get a short interruption of sound with each switch activation.

fazer

Re: Guitar speaker matrix switch design and build help.
« Reply #4 on: February 20, 2020, 10:20:03 AM »
Like square says impedance change with speaker con fig .   You can create a patch bay with parallel and serial points in it But the amp should be in standby while patching or switching and amp impedance should be adjusted to config of speakers. Then amp is switch back on.    Power tubes are what take the brunt of mismatched impedance.   They burn out quicker with a lower impedance load and will sound under damped if or loose in bass with a higher load than the amps impedance.     

If you close micing,  you can run then a combination of series and parallel and maintain an 8 ohm load and simple move the mic to different speakers for tonal variation.  Main thing is to protect the amp by switching it off or standby befor repatching or switching speaker loads.

Matador

Re: Guitar speaker matrix switch design and build help.
« Reply #5 on: February 20, 2020, 05:11:40 PM »
Hey Guys,

This might be weird or super easy... you tell me.

What I'm trying to do:

I have an old Marshall 4 x 12 cabinet that I have stocked with 4 different speakers. All of them are 8 Ohm and 90 - 100 watt. This is a rig exclusively for recording and re-amping.

I'd like to be able to to send signal out of a guitar amp to any 1, 2, 3, or 4 (All speakers).

I've considered trying to find or build some sort of ABCD switch but I don't know how something like this would affect the signal.

I'd love to hear any issues with this idea or other novel ideas for how to pull this off.

Thanks guys!

Ben
Is this for recording or for live use?

For recording, I've used many 4x12 cabs that had different speakers, and never had too much of a problem just miking up all speakers and picking and choosing during mixdown.  I don't see a lot of issues (other than phase) with the mikes blending together and each channel has the distinct sound of the individual speaker.

Of course, this only works for close miking:  if you are moving the mikes away from the cab and trying for room sounds  then this won't work.

Bandogmusic

Re: Guitar speaker matrix switch design and build help.
« Reply #6 on: February 21, 2020, 10:02:43 PM »
There was a 4-way cab switcher from Palmer: PCABSW4X.
I used it with an ancient Vox 4x12 cab which I loaded with different vintage alnico speakers.

It works for one speaker at a time, but not all four together.
The unit is conceived for use with tube amps and you will get a short interruption of sound with each switch activation.

Thanks for this lead... I'll check it out.

Bandogmusic

Re: Guitar speaker matrix switch design and build help.
« Reply #7 on: February 21, 2020, 10:08:51 PM »
Is this for recording or for live use?

For recording, I've used many 4x12 cabs that had different speakers, and never had too much of a problem just miking up all speakers and picking and choosing during mixdown.  I don't see a lot of issues (other than phase) with the mikes blending together and each channel has the distinct sound of the individual speaker.

Of course, this only works for close miking:  if you are moving the mikes away from the cab and trying for room sounds  then this won't work.

This would be exclusively for recording purposes.

I agree about the close mics... some time I like to put a mic out in front a few feet. I also, have a house guitar player who likes to play around with different combinations of speakers as we work out the tunes before tracking. It would be fun to come up with a novel solution.


Bandogmusic

Re: Guitar speaker matrix switch design and build help.
« Reply #8 on: February 21, 2020, 10:10:47 PM »
You generally do not want to switch speakers connected to vacuum tube amplifiers while powered up.

JR

Thanks JR... since this will be for recording I wouldn't need to switch on the fly.

Bandogmusic

Re: Guitar speaker matrix switch design and build help.
« Reply #9 on: February 21, 2020, 10:16:31 PM »
Like square says impedance change with speaker con fig .   You can create a patch bay with parallel and serial points in it But the amp should be in standby while patching or switching and amp impedance should be adjusted to config of speakers. Then amp is switch back on.    Power tubes are what take the brunt of mismatched impedance.   They burn out quicker with a lower impedance load and will sound under damped if or loose in bass with a higher load than the amps impedance.     

If you close micing,  you can run then a combination of series and parallel and maintain an 8 ohm load and simple move the mic to different speakers for tonal variation.  Main thing is to protect the amp by switching it off or standby befor repatching or switching speaker loads.

Is there an off the shelf patch bay that can be configured in this way or would we have to make one...  I can do the solder work but I don't have experience designing this type of thing.


Re: Guitar speaker matrix switch design and build help.
« Reply #10 on: February 22, 2020, 12:39:49 AM »
There has been a few discussions about this same idea you have .
What a tube amp really doesnt like is open circuit across the speaker terminals while sound is running through it , it could easily cause flashover in the tubes and damage the output transformer in a very short time . What a tube amp can do without harm is supply a shorted load for a small amount of time ,that being said you still dont want a changing load while your playing , that speaker switcher you mentioned seems like it probably kicks in a low load resistor while the relay contacts flip the speaker .The other thing is  a transistor amp may not survive a low load condition ,but open circuit at the speaker wont be any problem for it , total opposite of what a tube amp wants. Theres a lot of 'what if's in the equation , like say the player tries to switch to an output with no speaker load present , does your switch box detect that and prevent it happening ?  trying to achieve all that in one simple fool proof box is not that simple at all .

abbey road d enfer

Re: Guitar speaker matrix switch design and build help.
« Reply #11 on: February 22, 2020, 05:10:12 AM »
This would be exclusively for recording purposes.
Why do you want a switcher? What's wrong with moving cables? Is it because you want to compare in real time?

Now, having only one or two speakers connected in a 4x12 is not a good thing since the inactive speakers absorb the energy of those that are not connected. Each unused speaker must be shorted. Most Marshall heads have multiple outputs, so a clever switching system could be devised, that would switch the outputs in accordance with the resulting impedance, but it involves serious logic that would be better managed with a microprocessor.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Bandogmusic

Re: Guitar speaker matrix switch design and build help.
« Reply #12 on: February 29, 2020, 09:38:45 AM »
I'm thinking that something like this would  help.

https://www.tedweber.com/z-matcher



 

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