# Loss with less ohms?

Discussion in 'Amps and Cabs [BG]' started by bassicrunner, Sep 2, 2002.

1. ### bassicrunner

Sep 23, 2001
By having 2 cabinets at 8ohms, will my rig be significantly quieter than a rig with 2 4ohms cabinets? (Assuming the cabinets are all the same size.)

ps - i couldn't find this on the search

2. ### Jazz AdMi la ré solSupporting Member

It doesn't mean a thing.
It all depends on your power amp.

two 8 ohm cabs will make a total 4 ohm load. It's usally the best an amp can deliver.

two 4 ohm cabs will bring a 2 ohm impedance. Not so many amps can stand this. Actually, most will fry. It all depends on your amp's species.

3. ### FretNoMore* Cooking with GAS *

Jan 25, 2002
The frozen north
Everything else being equal - yes.

It also depends on your amp though, is it mono or stereo?

If it's mono, the result could be the opposite of what you would first think:

Not all amps can drive a load of 2 ohms (which is what you would get with two 4 ohm cabinets in parallell) and so you would have to connect them in series (with a resulting 8 ohm load).

Two parallell 8's on the other hand would result in a 4 ohm load and a louder result than the example above.

So, first check what your amp can handle, and if you state what amp you have perhaps we can be more specific.

4. ### FretNoMore* Cooking with GAS *

Jan 25, 2002
The frozen north
Jazz, you beat me to it, while I was editing my reply! Seems we agree though.

5. ### bassicrunner

Sep 23, 2001
hopefully will be an SWR SM-900 , and thanks for the help.

6. ### Matthias

May 30, 2000
Vienna, Austria
With the SM-900 you have the following options:
- run one 4Ohm cab from each side in stereo mode: total power output: max. 800W (400W@4Ohm per side)
- run one 8Ohm cab from each side in stereo mode: total power output: max. 480W (240W@8Ohm per side)
- run both 8Ohm cabs (=4Ohm load) in bridged mode: total power output: max. 900W (900W@4Ohm mono)

I don't recommend connecting two cabs in series (this can cause trouble if the cabs are not identical)
BTW if you connect one cab to the amp and the second cab to the first cab using normal speaker cables this is still parallel connection!!

Matthias

7. ### bassicrunner

Sep 23, 2001
Thanks, but to make sure, you're telling me the first two above are ok to do, but the third is not? That sucks since that is twice as powerful as the other option I have (second choice). Thanks.

8. ### BenF

Mar 29, 2001
Boston area
bassicrunner - Matthias' third option is fine. I run my sm-900 bridged into a 4 ohm load all the time. The only caution is that with a bridged 4 ohm load the amp gets pretty hot even with the internal fan going full blast - I keep a little desk fan blowing on the amp if I've got a long gig with the amp set up this way.

Alot also depends on how sensitive and efficient your cabs are.

9. ### Johnny BoomBoomSupporting Member

Jun 8, 2001
Glasgow, Scotland

No - what he is saying is that if you daisy chain the cabs, they will actually be in parallel. So option 3 is the optimum for you!

10. ### bassicrunner

Sep 23, 2001
Well that's super duper. Thanks alot.

11. ### Matthias

May 30, 2000
Vienna, Austria
That's what I've been trying to say. Thank you for clarifying.
Matthias