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Recording Guitar Amp via Amp Speaker

Member for

21 years 2 months
I'd like commentary on an idea I've had to record a guitar amp with another guitar-tailored speaker (used as a microphone, a la Yamaha's SubKick), and particularly one of the same make, model, and size.

Specifically, it occurs to me that using a 12" Alnico Blue speaker right on top of my Vox AC 15 might be cool for the following reasons:

1.) Exact same frequency response, in theory
2.) The mic-speaker would cover the entire AC 15's speaker, so finding a sweet spot would be no issue
3.) Further possibilities, like the idea of putting the mic-speaker in different cabinets and using it as above, could add for different personalities

Any help is appreciated.


Member for

16 years

Kapt.Krunch Wed, 06/06/2007 - 03:53
Ahhh...the old Beatles' "Let's put that speaker in front of Paul's bass amp and run it into the console as a mic" idea, eh?

May be worth a shot, just for something different, but I doubt it would sound all that great on a guitar. A guitar amp's speaker usually doesn't push quite enough air to make another respond in kind... even the same exact speaker. So, you'll probably not get the same frequency response picked up. Although Paul's bass amp probably had a lot more excursion to push enough air to make the other speaker respond, it's frequency response was likely different. It couldn't possibly have been "responding in kind" because there would have been a bit less movement in the "mic-speaker".

And screwing them together face-to-face to couple them together might get more response from the "mic-speaker", but I'd hesitate to try that, especially if you were pumping a lot of wattage. Might restrict the main speaker's natural movement, and screw it up with very little free air in front.

A tighter, lower wattage, different size speaker may actually be better. Something with a looser surround may not respond as quickly and easily as something stiffer. Just experiment with distance.

Yeah, it's been done before. But, there's probably a reason why people like SM57's in front, and not everyone is popping a speaker in front.

Just some stuff to think about and debate. :wink:


Member for

14 years 7 months

Link555 Wed, 06/06/2007 - 13:27
I have tried that before with a Mackie HR824 Speaker. I have a slightly damaged woofer that I had to replace a few years back. I used it on a kick drum. My thinking was it would respond better to record low frequencies due to the amount of energy it would require to move the mass of the speaker. It was a fun experiment, something I have been meaning to play with a bit more.

Member for

16 years

Kapt.Krunch Thu, 06/07/2007 - 04:02
patrick_like_static wrote: I figured it couldn't be an entirely new idea, but I hadn't heard about it being used before. That someone's tried it and it didn't stick is perhaps all the answer I need.

Thanks, Kap'n. reason not to try it. Just keep all the aforementioned things in mind, and think about the physics of what it is doing.

You may even want to run the guitar amp a little bass heavy to push a more air, and using a stiffer, smaller may just get a killer nasty tone. Who knows? Get a few hours to goof around...why not? Might be a tone that inspires something.

I can't remember which Beatles tunes that actually made it onto...I think it was during the Revolver/Rubber Soul era...but it's on there for several.

I'm a believer in using things for other than their intended purpose, within limits. I don't really want to fry things, but nothing wrong with trying things. Nothing new is made without experimentation.


Member for

21 years 2 months

Pro Audio Guest Thu, 06/07/2007 - 13:52
It's just that a new Alnico Blue is somewhere around the $250 mark, so if someone has already done the experimenting for me...

Your comments about the physics involved in one speaker moving another are understood, but I thought about this last night: shouldn't a speaker cone flexing forward 2 inches produce the force needed to move an identical speaker back the same amount, provided minimal air dispersion from one speaker atop the either?

Member for

16 years

Kapt.Krunch Thu, 06/07/2007 - 16:08
The initial attack might move the other speaker, but probably not by the same amount..and that would depend on how close it was. When the attack subsides and, say, you're holding out a long blues note, the amp speaker is still moving, but probably not pushing enough to make the other move exactly in the same manner...the other speaker will probably decay much faster. You may still be able to hear SOMETHING, but probably not in direct relation.

Might work better if you were doing slash'n'thrash where you're just pummeling the thing over and over to produce constant attacks. That way the other speaker reacts, sends the signal to the board, and may not have time to decay much and settle down before it sees another attack.

Even then, with air between them, it's only reacting to the outward force of the amp speaker...the amp speaker can't pull the other speaker back toward it while it's on its back motion. It reacts on its own, without power. So, you'll lose that part. It would have to be directly coupled, physically, for both speakers to react equally.

If you screwed one speaker face directly to the other, other problems may arise. You are changing the whole design of the working speaker. Instead of blasting out freely into a wide open space, it's blasting into a very small space, with a physical resistance impeding its motion. First, that will probably alter the tone. It ain't completely free to move in and out anymore.

Second, you may run the risk of voice coil damage by having it it pushing harder than it was designed to, and by having the reacting speaker react a bit more slowly back. Since it's probably impossible to actually seal the two airtight, air will still want to get in or out, and that could cause resonances and counter-resonances because at some point, it's likely the two cones will fight a bit...especially if you are pumping a lot of power. It's impossible to have the other cone react as quickly as the amp cone that has the signal controlling it. If you get the cones to start fighting against against each other, it could be enough to send it off center if it starts pushing air in uneven places respective to each other...kind of causing a wobble, and what have you got? A scraping voice coil.

It also may be possible that excessive heat build up could also occur more than is normal with the amp speaker. It's probably working harder, and the air in front isn't fresh. That's not so good either.

That's why I said I would be hesitant to screw them togtether face-to-face.

It's still not out of the question to try placing another speaker in front. Suspecting that the other cone is going to decay quicker, if you ran that direct and mic'ed the amp speaker, you may find a gnarly attack from both that smooths out as a note or chord is held to what will then likely be more of your amp speaker. May be phase issues, though, so you may have to consider the placement. Mix them together for something different.

Heck, you may just like the other speaker tone by itself BECAUSE of the possibly quicker decay.


Maybe it'll help lessen finger squeaks? I dunno. I haven't done it. I read about it before in several places. Wouldn't surprise me if Zappa tried it, knowing his proclivity for unusual things.

I doubt that the other speaker could accurately capture and recreate exactly what the amp speaker is doing. A tighter speaker may actually capture it better because it's probably taking less to keep it "excited" than one with the same, or more, excursion, so it may be able to react more quickly.

You may even find it just as interesting to discover what it WILL capture, if not the exact sound. Who knows?

Anyway, these are what I can imagine could happen.

Debate always welcome :)