I was wondering if UG could answer some questions about adding a sub woofer I have to my guitar amp. Right now whenever I play bass I have to use my guitar amp, and I'm always afraid of damaging it. I figured if I added the sub woofer it would reduce chances of killing my amp, while boosting shaking power.

Any ideas? If this possible? Worth pursuing?

you would need another power amp and a crossover. just get a bass amp, cheaper and will sound better.
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Find an extension cabinet with a 15-inch speaker? That'd be easier and it'd put our more low end.

Probably be cheaper than what you're thinking, too.
I have a similar question:

I blew both the speakers in my Vox AD50VT-212, which obviously has two speakers.

I had a spare one twelve inch speaker, so I replaced one with that. But I also have a very nice 8 inch subwoofer that I was wondering if I could put in as the other speaker. will I run into any problems doing this? I believe my amp works on 8 ohm speakers, and this subwoofer is 4 ohms. Is this a problem?
How many ohms is your spare 12in speaker?
If both speakers are 4ohms, simply wire them in series and you've got 8ohms.
If the 12 inch is anything other than 4ohm, and your amp needs 8, then you are out of luck.
I'm not sure how much it is. I figure its four, because how could I have 2 8 ohm speakers in an 8 ohm amp?

I'm kindof guessing on the 8 ohm thing though, because I'm just judging from what it says on the amp where you plug in the external speaker.
oh I was wrong. The AD50VT 212 is a 16 ohm.

does this change anything? as far as I know, the speaker is 8 ohms.
Quote by Iamonfire
I'm kindof guessing on the 8 ohm thing though, because I'm just judging from what it says on the amp where you plug in the external speaker.

Ahhhh assumptions like that are dangerous!
Many amps have a speaker out that is designed for a different impedance than the load in the combo. A quick look through the Vox website yielded an owner's manual, which states that the stock speakers are 8ohm each. That means that you need a total impedance of either 16ohms or 4ohms, depending on whether it was originally wired in series or parallel. The manual does not say, and I am not familiar enough with that amp to know off the top of my head.
So its a 16 ohm speaker, from what I've discovered in the manual.

I'm not sure how many ohms the speaker could be, though. it's either 8 or 4. I do know for sure the subwoofer is 4, though.

also, how would having a subwoofer affect the sound tonally?


if this doesn't end up working out, will having just the one replacement speaker be okay?
Quote by Iamonfire
oh I was wrong. The AD50VT 212 is a 16 ohm.

does this change anything? as far as I know, the speaker is 8 ohms.

If are positive the load is supposed to be 16ohms, then the stock speakers (which the manual says are 8ohm each) should be wired in parallel. This means that your only options with 2 replacement speakers is either two 8ohm speakers in series (as original) or two 32ohm speakers in parallel (the do exist, but you won't find them easily). So you can't use that 4ohm speaker.

You need to have the total impedance of your speakers match the impedance the amp wants at output, or else smoke and destruction of your amp can ensue.

The only way you can use just one speaker is if that single speaker matches the impedance the amp wants: i.e. a 16ohm speaker for 16ohm amp.
Last edited by cedricsmods at Dec 12, 2009,
so I can't just have the one speaker in there?

also, what if I changed the transformer?
Last edited by Iamonfire at Dec 12, 2009,
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yeah probably. Or the circuits.
As I explained, you can only use a single speaker if it matches the amp's impedance.
You need to find out what the impedance of that single speaker is. If it is 16ohm, you can use it alone. If it is 8ohm, you can MacGyver it by wiring the speaker to a 1/4" male plug and plugging it into the speaker out jack.

Why on earth would you buy a new tranny? You can get another speaker cheaper. You could even get a set of decent speakers cheaper.
nah, my dad has a transformer. he was just suggesting.

the speaker is 8 ohms, as far as I know. it isn't marked, but that's what the friend who gave it to me told me it was. is there any way to check?
Sure. If you have a multimeter that can measure resistance, just put one probe on the + terminal and the other probe on the - terminal.
okay, I just checked. its a 4 ohm speaker. so does that mean hooking up the subwoofer and the replacement speaker would work?

would I still get the same amount of volume? would the sub. change the tone?
Yes the tone will be different. I am not sure whether you will be able to get the same volume before the speakers start to distort (at which point you need to back off the volume).

If you have two 4ohm speakers, you need to wire them in series to a male 1/4" plug, then plug that into your 8ohm speaker out on the amp.

(You will have to do it this way because there is no way to combine those two speakers for the required 16ohms impedance that your amp wants for the internal speakers. When there is a plug in that speaker-out jack, it bypasses the normal internal speaker circuit. You are basically going to be tricking your amp into thinking that an external cab is connected to it. The wiring is the same as an external cab, the speakers are just being housed in the combo. Do not attempt to run the amp without the speakers plugged in. Running an amp with no speakers connected is bad news bears.)
Last edited by cedricsmods at Dec 12, 2009,
A subwoofer really works best running off a crossover so only lows are sent to it. W a guitar amp just running a sub w a regular guitar speaker in series its gonna get the full spectrum. A sub running higher freqs wont sound so good, and the other "guitar" speaker will still be getting those speaker killing low freqs.

Your best bet is to look around and buy some bass speakers, they will work w your bass and still work great for guitar. Another limiting factor is a guitar amp just isnt made to put out those low freqs anyways. The internal filter caps kill the lows to keep things from getting muddy, and most guitar OTs dont have alot of power in low freqs. For example a hammond OT most would use for guitar is 150 Hz - 15 Khz whereas a "hifi" 1600 series is 30 Hz to 30 Khz.
Another thing you might want to look at.
And i'm only throwing this out there in hopes
it might help. But i know a few Crate amps use
the internal speakers WHILE an external one is
plugged in.
I don't know if it'll make a difference in your situation,
with not having the internal speakers in, but, just
thought i'd put that out there. Feel free to correct me
if i'm wrong.
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hahaha wonderful. so I just tried it out and it turns out I have the same problem as before. it wasn't the speakers after all. it makes warbly distorted sounds when I play lower ended stuff on the guitar. any ideas as to what could be wrong? I thought the speakers were blown, but I guess not.