Converting a 1x12 cab from 4 ohms to 8 ohms

[samkeen]

Hi all,

Can anyone tell me, is it possible to convert a 1x12 4 ohm cab to 8 ohms? Hoping to do it if it's feasible / not expensive!

Thanks

[razze06]

A 1x12 cabinet only has one speaker with a given impedance, in your case 4 ohm. I can't see any solution short of replacing the entire speaker with an 8ohm one. Whether that is not expensive depends on the speaker and your budget

[samkeen]

I read this on a hifi forum, but I'm concerned that this might be wrong, and wouldn't want to damage the driver:

[font=sans-serif][size=3]two resistances in series gave a combined resisitance that was their sum. I don't think this has changed. Connect a 4 Ohm resistor anywhere between one speaker terminal and the corresponding terminal on the amp, and you add 4 Ohms to what the amp sees. The amp doesn't know, or care, whether the load is a speaker or a lump of wood.[/size][/font]

[razze06]

The statement is true, from a scientific point of view. I am doubtful whether that is the right thing to do...

[Dad3353]

[quote name='samkeen' timestamp='1338286623' post='1672030']I read this on a hifi forum...[font=sans-serif][size=3]Connect a 4 Ohm resistor anywhere between one speaker terminal and the corresponding terminal on the amp...[/size][/font][/quote]

Good afternoon, samkeen...

A resistor, same value as the speaker impedance, will have to absorb the same power as the speaker, and will dissipate this as heat. If the speaker receives 150w, then so does the resistor. That's equivalent to a very bright light bulb, and would be very hot indeed, unless special cooling steps were taken (heat sinks, fans, water pipes...). More power..? More heat for the resistor to dissipate; at 500w we're getting up to a smallish radiator. OK for heating in winter, but not recommended for a speaker cab.
The short answer is... No, one cannot 'bodge' a cab impedance change. Either swap the speaker for an 8 ohm one, or have the present speaker reconed as 8 ohms (if such a kit exists for that speaker...). Sorry.
A second cab, with 4 ohm impedance, wired in series to the present one, would work. A bit delicate, as series cabling has it's drawbacks, but it would work.
Could you please explain what problem you're trying to solve with this..? There may be an alternative approach that can give satisfaction.
Hope this helps...

[Matt P]

Dad3353 speaks the truth, a resistor would have to be [i]very[/i] big to handle even the wimpiest of practice amps let alone a gigging head, we do need to know what 1x12 it is you're trying to modify, i have a feeling that the best course of action would be to sell it and get an 8 ohm cab instead.

Matt

[samkeen]

Excellent, thanks very much for clarifying this guys.

I am buying a 4 ohm cab, as it's lovely, great price and a good size for small to medium gigs, but as it's only a 1x12 there may be times when I'd prefer to add a second cab, but my amp doesn't go down to 2 ohms.

[chris_b]

You will be loosing a lot of flexibility if you buy a 4 ohm 112 cab. The 4 ohm cab won't be much louder than an 8 ohm version so you don't gain anything with small 4 ohm cabs. I've got 2 8 ohm 112 cabs and I can use one or both for all but the loudest gigs.

If you haven't bought it yet I'd reconsider.

[Bill Fitzmaurice]

[quote name='samkeen' timestamp='1338286161' post='1672024']

Can anyone tell me, is it possible to convert a 1x12 4 ohm cab to 8 ohms?
[/quote]Only by taking it to a music store and trading it in.

[samkeen]

Thanks all, I appreciate the advice (and wry wisdom Bill!)

[neepheid]

You do get switchable 1x12 cabs - admittedly the only one I know is the Hartke HyDrive which is switchable 4/8ohms.

Of course, if you use two of these you'd better make damn sure you've got the switches in the 8 ohm position if you're using them in parallel with a min 4 ohm amplifier

[thebuckets]

[quote name='neepheid' timestamp='1338299329' post='1672328']
You do get switchable 1x12 cabs - admittedly the only one I know is the Hartke HyDrive which is switchable 4/8ohms.

Of course, if you use two of these you'd better make damn sure you've got the switches in the 8 ohm position if you're using them in parallel with a min 4 ohm amplifier
[/quote]
Wise words neep

Does anyone know how does the hydrive dissipates the heat when switched to 8 ohm?

[LawrenceH]

[quote name='thebuckets' timestamp='1338376310' post='1673436']
Wise words neep

Does anyone know how does the hydrive dissipates the heat when switched to 8 ohm?
[/quote]

I /think/ their drivers have dual voice coils so one just gets switched out - no extra heat to get rid of. I can't imagine the design is optimal for either scenario though, but I've not got any experience with them myself.

[BILL POSTERS]

[quote name='samkeen' timestamp='1338294738' post='1672229']
Excellent, thanks very much for clarifying this guys.

I am buying a 4 ohm cab, as it's lovely, great price and a good size for small to medium gigs, but as it's only a 1x12 there may be times when I'd prefer to add a second cab, but my amp doesn't go down to 2 ohms.
[/quote]

Well, If the second cab was a 4 ohm 1X12, you could add it in series, total would then be 8 ohms. I woulnt expect to notice a huge difference in volume, though.