Adding speakers and not changing ohm rating

[walls]

First off let me introduce myself. This is my first post here. I'm a converted guitar player who's playing in a roots style 3 piece band.

I'm currently playing through a 66 Dual Showman head and 67 big style fender cab 2x12. It's plenty loud for practicing and I'm looking for a small SS head as a back up for when the showman won't cut it volume wise(that's another story).

Anyway, to gain volume, I'm going to add more speakers. I'd like to build a new speaker baffle for the cab I have (I like the vintage look) and end up with a 4x12 cab.

I'm using 2 eminence kappalite 12" speakers which are 8 ohm wired to 4ohms. It seems as though most bass heads like to see a 4 ohm load.

Is there anyway I can add speakers to my current setup and still retain the 4 ohms? Any other options I may not be thinking of? I'm definitely open to options. I know getting a new modern cab would be the easiest but, that's not what I'm looking to do.

[i_got_a_mohawk]

Sadly not.

With 4x 8 ohm speakers you'll get 2ohms (all parallel), 8ohms (series/parallel) or 32ohms (all series).

SS amps can run higher impedances, so it wouldn't be a problem running 8ohms on a 4ohm amp, you'll just have less output. With a tube amp, it's important to keep in plugged into the correct impedance.

You could always get 4x 4ohm speakers or you could change the grill cloth on a newer cabinet to match the older gear.

[tech21nyc]

You would need 4 16ohm speakers to get 4 ohms. I get where you're coming from in terms of the vintage looks but that old Fender cab may not really work out very well even with the 4 speakers vs 2. Those old cabs weren't really the best design for a bass guitar application.

Another easier solution may be a newer design cab with some retro looking grill cloth and hardware to make it look vintage.

[billfitzmaurice]

Originally Posted by walls

I'd like to build a new speaker baffle for the cab I have (I like the vintage look) and end up with a 4x12 cab.

If you do you'll lose low end response, collapse the midrange dispersion and introduce high frequency combing. And if you didn't vent that cab to match the specs of the Kappalites that would explain your volume problems.

[i_got_a_mohawk]

Originally Posted by tech21nyc

You would need 4 16ohm speakers to get 4 ohms.

You can do it with 4 ohm speakers too with series/parallel wiring.

[walls]

All advice duly noted. I think I may just keep this cab for practice and have a separate one for gigs. Maybe spruce it up with some Fender style tolex and grill cloth.

The cab I have is ported (someone before me put two holes in it) but maybe someone would be kind enough to give me a link related to the size of porting vs cab size?

Thanks in advance.

[Mr. Foxen]

Originally Posted by walls

All advice duly noted. I think I may just keep this cab for practice and have a separate one for gigs. Maybe spruce it up with some Fender style tolex and grill cloth.

The cab I have is ported (someone before me put two holes in it) but maybe someone would be kind enough to give me a link related to the size of porting vs cab size?

Thanks in advance.

LinearTeam

[i_got_a_mohawk]

Sadly it isn't as simple as that.

The porting required depends on both the cab size and the speakers you're using.

Check out WinISD, it's a free software which should help you out


- Edit, beaten to it by Mr. Foxen

[will33]

If they're holes cut in the baffle, no pipes going into the cab, it's likely tuned too high. Mr. Foxen's link is WinISD, a modeling program used to tune the cabinet to the drivers. I'd use that to get the best you can out of your current setup and just consider that as good as it's going to get. You can buy or build modern, better speakers and finish them in the old school look.

To your original question, you can't double the speaker count without changing the impedance. You can however quadruple it and maintain the same impedance with series/parallel wiring although that's likely impractical as you'd be carrying four 212's.

[Mr. Foxen]

Basically, get one of these in the silver grillcloth option: Barefaced Bass - Ultra lightweight high power bass guitar speaker cabinets

[BassmanPaul]

Personally I'm not in favour of hacking a vintage cabinet trying to make it something its not. By all means build a 4x12 using WinISD, even cover it to look Fenderesque but leave the original alone and maybe drop some JBLs into it.

[walls]

Originally Posted by BassmanPaul

Personally I'm not in favour of hacking a vintage cabinet trying to make it something its not. By all means build a 4x12 using WinISD, even cover it to look Fenderesque but leave the original alone and maybe drop some JBLs into it.

Believe me, I hear you. I have some vintage stuff I take perfect care of. That said, this thing's battered, holes drilled in it, and in the end, one of the least desirable of the blackface/silverface era of Fender. Perfect for gigging. Really that's why I wanted to make a go of it.

Thanks for the help fellas.

[will33]

I'd tend to agree with BassmanPaul regarding vintage gear as well but as you say, this thing already has a couple holes drilled in it. You wouldn't be doing any further damage by sticking a couple port tubes in those holes. Stapling lining to the inside of the cab and adding a couple crossbraces to stiffen it up would be improvements as well.

WinISD can seem a little complicated at first but your kappa's should already be in the database so start by taking measurements of the cab as is to see where you're at with it.

[darius8]

Hey Walls, heres an idea that may be a nice compromise,
if you only have 12' 8 ohm speakers to work with, just add ONE more
and the total load will be about 5.3 ohms. perfectly safe.

The speakers in your cab are 8 ohms wired in parallel = 4 ohms
Re-wire them in series to get 16 ohms

Then, with a new 12" 8ohm, wire this speaker to your other speakers in
parallel, this should be a total load of 5.3 ohms.

Heres a rough diagram:


first set of speakers +speaker- _______ +speaker-

single speaker l________ +speaker- ________l

connect the positve of the first set to the positive of the
single speaker and negative of the first set to negative of the
single speaker.

[billfitzmaurice]

Originally Posted by darius8

The speakers in your cab are 8 ohms wired in parallel = 4 ohms
Re-wire them in series to get 16 ohms

Then, with a new 12" 8ohm, wire this speaker to your other speakers in
parallel, this should be a total load of 5.3 ohms.

Then 2/3 the system power goes through the single 8 ohm driver, 1/3 ( 1/6 of system total each) goes though the two series wired drivers.

[will33]

Originally Posted by darius8

The Eminence Kappalite 12" speakers, if I'm no too far off, is rated about 300w,
The head he's using is, I think 100w. Would it hurt?

What about excursion, and having the one driver trying to move farther than the others....all in the same box. Not to mention stuffing more drivers in there taking away response in the lows?

[billfitzmaurice]

Originally Posted by darius8

The Eminence Kappalite 12" speakers, if I'm no too far off, is rated about 300w,
The head he's using is, I think 100w. Would it hurt?

It wouldn't hurt anything, but it would have less output than two drivers, so there's no point.

[walls]

If there is a way to add more speakers (2 or 4) and still use the 8 ohm speakers I own already, I'm definitely open to hearing ideas.

Until then I'd like to investigate tuning this cab for use of the Kappalites I have.

This may be pushing it for a FNG but, would someone mind helping me with the WinISD thing?

I have a Mac and can't download the software and the online program doesn't leave me a spot to type in my speakers as far as I can find.

2- Kappalite 3012HO speakers -Here's a link
Speaker Detail | Eminence Speaker

My Cab is 29x39x11

[darius8]

I was just making a suggestion to help.

[Ric5]

Adding speakers and not changing ohm rating

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The only way I can think of is powered pa speakers.