4 ohms to 8 ohms

[beerdragon]

It turns out the two Trace Elliot 2x10 cabs i bought are not trace, well when me and the keyboard player took them apart there was nothing on the speakers. and i would imagine TE would use Celestions. when we put a meter on them they showing to be 4 ohms. now, i know bugger all about this so advice would be appreciated. my mate the keyboard player said he would rewire them into 8 ohms, sure enougth after some soldering the meter said 8 ohms. is this all you have to to. i was a bit sceptical. There's a bit of a buzz from one of the speakers but i have seen a couple of 10 inch celestions on ebay that i might get.

[Bill Fitzmaurice]

[quote name='beerdragon' post='241774' date='Jul 17 2008, 09:21 AM']i was a bit sceptical.[/quote]
As well you should be. It's not possible to rewire a 4 ohm 2x10 to 8 ohms. If indeed the meter reading went from 4 to 8 ohms it could only do so if one of the drivers was disconnected.
BTW, a meter would not read either 4 or 8 ohms, as it measures the voice coil resistance, not impedance. The DCR measurement is on average .7 the impedance. I assume you took that into consideraton with your results.

[BOD2]

Hmmmm....you need to be a little careful here.

Firstly you cannot read cabinet IMPEDANCE directly with a RESISTANCE meter. You'll get a reading but it won't be exact.

But more worryingly I cannot see how you can achieve the results you're hoping to get by rewiring the speakers. If the cab only has two speakers then both speakers will almost certainly have the same impedance and both will be 4, 8 or 16 ohms. In that case you have the choice of wiring the two speakers in the cab in serial or in parallel. Here are the resultant impedance values for a two speaker cabinet -

2 x 16 ohm in parallel = 8 ohm
2 x 16 ohm in series = 32 ohm

2 x 8 ohm in parallel = 4 ohm
2 x 8 ohm in series = 16 ohm

2 x 4 ohm in parallel = 2 ohm
2 x 4 ohm in series = 8 ohm

From the above there is no combination that would have given you 4 ohms wired one way and then 8 ohms wired the other way. So the question is, what exactly do you have now ?

[beerdragon]

[quote name='BOD2' post='241789' date='Jul 17 2008, 02:41 PM']Hmmmm....you need to be a little careful here.

Firstly you cannot read cabinet IMPEDANCE directly with a RESISTANCE meter. You'll get a reading but it won't be exact.

But more worryingly I cannot see how you can achieve the results you're hoping to get by rewiring the speakers. If the cab only has two speakers then both speakers will almost certainly have the same impedance and both will be 4, 8 or 16 ohms. In that case you have the choice of wiring the two speakers in the cab in serial or in parallel. Here are the resultant impedance values for a two speaker cabinet -

2 x 16 ohm in parallel = 8 ohm
2 x 16 ohm in series = 32 ohm

2 x 8 ohm in parallel = 4 ohm
2 x 8 ohm in series = 16 ohm

2 x 4 ohm in parallel = 2 ohm
2 x 4 ohm in series = 8 ohm

From the above there is no combination that would have given you 4 ohms wired one way and then 8 ohms wired the other way. So the question is, what exactly do you have now ?[/quote]


I haven't got a clue what i have now . The meter measurement was taken from one of the drivers. as i said i haven't a clue about this, neither its seems does our keyboard player. i guess i had better put it back as i found it. how do you tell if its 4 or 8 Ohms?

[Hamster]

Quick and dirty is how Bill suggests. Measure the DC resistance, which is around .7 of the real value, so 3 ohms for a 4 ohm speaker and 6 ohms for an 8 ohm speaker.

[Bill Fitzmaurice]

[quote name='beerdragon' post='241853' date='Jul 17 2008, 11:11 AM']as i said i haven't a clue about this, neither its seems does our keyboard player.[/quote]
That's usually a good reason to leave well enough alone. Newbies, speakers and soldering irons are a combination that can lead to blown amps.