Author Topic: Worried about my cabs resistance (Read 6558 times)

_tom_ · « **on:** December 19, 2006, 11:58:40 PM »

So apparently, with 2 speakers my cab cant be wired in series/parallel as found here http://www.usspeaker.com/speaker%20wiring-1.htm

Both speakers are 8 ohm. When I plug a cable into the 2nd input jack on the cab (theres 2, both of which seem to be 8 ohm inputs) and read the resistance at the other end of the cable, the resistance is around 5-6 ish, which I assume means the cab is 8 ohm.

I've been using the amp like this (8 ohm output into the cab) for almost a month now and it sounds fine. If it were a resistance mismatch would something have gone wrong by now? Should I be worried?

I'm tempted to rewire it all in series to get a 16 ohm load, at least I know it'll be matched with the amps output, but then I'd need a new hotplate as mines 8 ohms..

Cheers for any help

Twinfan · « **Reply #1 on:** December 20, 2006, 09:38:12 AM »

Not entirely sure what your question is here mate? The GH50L has multiple outputs so if you've been using the 8ohm output into an 8ohm hotplate into an 8ohm cab you've been spot on.

I'd wire your cab in series though to get 16ohms as I find valve amps sound better at 16...

_tom_ · « **Reply #2 on:** December 20, 2006, 09:43:08 AM »

Well basically, I've heard that a 2x12 with 2 8 ohm speakers cant be wired together to get a total 8 ohm resistance.

Just seems weird that my cab DOES read to be an 8 ohm resistance even though its apparently not possible.

Never heard about different resistances changing tone though, I might try 16 ohm as it seems easy to rewire em in series (if that diagram on the us speaker site is anything to go by!)

DeanS · « **Reply #3 on:** December 20, 2006, 09:44:37 AM »

+1 on the sound of 16 ohms wih valves.

_tom_ · « **Reply #4 on:** December 20, 2006, 09:50:36 AM »

I may just try it then, I honestly never thought the resistance would affect tone :o

As for the jack, what kind do I need? The ones the cab has now are the ones with 4 lugs on, but if I'm following this diagram surely I only need a regular switchcraft with 2 lugs on?

I always forget, on a jack which is positive and which negative? Please illustrate on here for me :lol: - http://www.wdmusic.co.uk/upload/wdmusic/products/WDE12.jpg

Twinfan · « **Reply #5 on:** December 20, 2006, 10:41:28 AM »

Ah - gotcha. Your cab must be wired up in parallel and it's running 4ohms then? But it's reading 6? Strange...

A regular switchcraft jack should be fine and I think the negative is the tag round the base and the positive is the tag with the tip.

jpfamps · « **Reply #6 on:** December 20, 2006, 11:41:57 AM »

If you measure an 8 ohm speaker with a multimeter you usually get a reading around 6 ohms, as you correctly oiunt out.

You can't wire up two 8 Ohm speakers to give an 8 ohm load. This would suggest to me that either one of your speakers has gone open circuit or is not connected if the speakers are in parallel; or that one of the speakers has gone short circuit is the they are in series. Before you rewire your cab remove the speaker wire and check both speakers with a multimeter.

If you rewire the speakers in series check that you get a reading of about 12 ohms with the multimeter before you plug your amps in. Wiring the speakers in series will allow you to use the 16 ohm setting on your amp, which some people preffer the sound off. This is probably because you are using all the windings on the secondary of the output transformer. The disadvantages of running your speakers in series are that if a speaker goes open circuit then you risk damaging your output transformer. Additionally you might find the bass is less tight due to poorer speaker damping.

Hope that this is useful.

_tom_ · « **Reply #7 on:** December 20, 2006, 02:10:51 PM »

Cheers!

I have measured both speakers, they each read around 6 ohms. I'll try re-doing it in 16 ohm sometime.

hunter · « **Reply #8 on:** December 20, 2006, 02:52:04 PM »

Quote from: _tom_

Cheers!

I have measured both speakers, they each read around 6 ohms. I'll try re-doing it in 16 ohm sometime.

I would say your multimeter sucks ...

:roll:

_tom_ · « **Reply #9 on:** December 20, 2006, 02:55:56 PM »

Hmm it is only a cheap one.. However both speakers read the same as what the speaker in my HRDx does (which is definately 8 ohm)

BTW, is this the correct polarity on a jack or am I backwards?

_tom_ · « **Reply #10 on:** December 22, 2006, 12:31:51 PM »

Rewired it to 16 ohm, it was way easier than I thought it would be!

To be honest I cant notice that much difference in sound, maybe its a bit tighter?

I need a 16 ohm hotplate now tho :(

HTH AMPS · « **Reply #11 on:** December 22, 2006, 04:51:40 PM »

I always think that amps sound 'tighter' ran into a 4ohm cab whereas a 16ohm load seems more 'vintagey' if that makes any sense at all.

All I know is that I can tell the difference even if it's subtle - more of a 'feel' thing than an out and out tonal difference.

:twisted:

stuckin93 · « **Reply #12 on:** December 23, 2006, 02:46:44 PM »

You might want to email THD before you shell out for a new hotplate. i am sure one way is OK to use what you have, and i'm sure that is a higher resistance cab.