Guitar Amplopnik: Extension Speaker Cab!

"Nonster" (noahnic) 11/06/2015 at 11:30 • Filed to: None

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The bass player in my band said he knew someone from work who was getting rid of a speaker cabinet and said I could have it for free! Much to my surprise it was a big ass 4x12 cabinet! Do I really need it? .....Well no, but hell yeah it’s AWESOME!

It’s pretty important to have the proper impedance for the extension cab. My amp is a Fender Hot Rod Deluxe. It has an 8 ohm internal speaker and can be run with 4 or 8 ohms of total load. So I have 3 options for hooking up an external speaker.

Option 1: 8 ohm load into the main output jack and nothing on the extension jack. So I could run the 8 ohm internal speaker or just hook straight up to an 8 ohm external cab. So 8 ohm total load.

Option 2: 8 ohm into main and 8 ohm into extension. This could be the internal speaker and an 8 ohm extension cab. or two(or a stereo) 8 ohm extension cabs. So 4 ohm total load.

Option 3: Dummy plug into main to switch it to 4 ohm mode and a 4 ohm extension cab. So 4 ohm total load.

They’re 8 ohm speakers and its wired as a stereo pair. Since each pair is wired in parallel that means its currently set up as two 4 ohm sets. So to test things out and see if I like the sound I did option 3 and ran just one side of the cab to my amp so I was running 2 out of the 5 available speakers. The best word to describe it is GNARLY! It sounded as if I could summon Thor’s hammer from Valhalla AND SMITE THOSE THAT WOULD RISE FROM THE REALM OF DARKNESS! In more technical terms, it had much better bass and mid-range punch and an overall more well rounded sound. It felt louder, but that’s probably more a function of it moving more air and not a real huge increase in decibels. I can’t wait to see how it sounds with all 5 speakers cranking.

Next I’m going to wire the stereo pair in series so that I have a mono 8 ohm 4x12 cab. Then I can run either option 1 or option 2. Like so...

Boom. Math

In reality, a 4x12 is overkill and a pain to haul for gigs so I’ve been tossing around the idea of chopping it in half to make a 2x12 cab. With two 8 ohm speakers I would run them in parallel for 4 ohms and have to bypass the internal speaker (pretty much what I did in my option 3 test run). That’s a lot more work so that’ll be a project for a later date.

I’ll report back on estimated hearing loss once I finish the wiring. \m/

Echo51 > Nonster 11/06/2015 at 11:36

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Full-range 12”, and not pure woofers, correct?

Jcarr > Nonster 11/06/2015 at 11:37

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Nice! What’s it running for speakers?

I’ve been wanting to get a little lunchbox tube amp (I’m thinking Bugera G5) and I have an old Line6 Spider III 1x12 that has some amp-side issues.

I’m planning to cut the connection from the amp to the speaker and wire in a 1/4” female jack so I can basically use it as a 1x12 cab. The Celestion that it’s got in there already is in excellent shape.

RamblinRover Luxury-Yacht > Nonster 11/06/2015 at 11:46

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In more technical terms, it had much better bass and mid-range punch and an overall more well rounded sound.

Would you describe it as buttery biscuit bass?

Mattbob > Nonster 11/06/2015 at 12:24

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Looks like you got it all figured out. As a shortcut for your math though, instead of doing the (1/8+1/8)^-1 business, you can just do the product of the two resistances divided by the sum for parallel resistances. so it goes to (8x8)/(8+8) its just faster to work out, and product over sum is easy to remember.

Zip-McBump > Nonster 11/06/2015 at 12:32

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Was going to suggest option 3 before I saw your postscript. I’m still leaning towards that, but you forgot the all-important axe/music style equation.

I’ve gotten better results running 4 ohm for chugga-chugga stuff, but better highs with an 8 ohm setup (it seems counter-intuitive, but that’s just my ear). I’d say at this point, it all depends on what kind of sound you’re going for.

The idea of just repurposing the speakers into two 2x12s seems like a good idea, if you can fab the cabinets on the cheap.

Nonster > Echo51 11/06/2015 at 12:51

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yep, they’re full range, no trouble with the high notes

Nonster > Mattbob 11/06/2015 at 12:54

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Thanks for the tip. I’m a mechanical engineer so I haven’t done any circuit calculations in quite a while so I just wanted to be sure I was doing things right so I don’t damage my amp

Nonster > Zip-McBump 11/06/2015 at 13:08

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My main guitar is a Telecaster. I also have a strat knock-off with some meaty humbuckers for when I’m in the mood for the chugga-chugga stuff, but I usually stick to a more classic rock style overdrive like tone.

My first thought was to cut off the top half of this cab and put a new board on top so that its a nice low rolling base I can set the amp on top of.

Nonster > Jcarr 11/06/2015 at 13:23

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It has Carvin British series speakers. I’ve never really heard of the brand, but they sound pretty good to me.

I haven’t had a chance to play through one of those little Bugeras but I’ve heard good things. It would probably sound great through that 12” Celestion. It would be really cool if you could put that speaker in classic looking cab that matched the bugera though.

Jcarr > Nonster 11/06/2015 at 13:28

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Carvin is great, they’ve been around for a long time.

The Opponaut formerly known as MattP123 > Nonster 11/06/2015 at 19:37

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I’m sure the folks in our dorm loved us.

Nonster > The Opponaut formerly known as MattP123 11/07/2015 at 14:42

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It looks like you still haven’t hit the ceiling yet, needs one or two more amps.