Bridged at certain ohm?

[la bam]

Hi all,

Just wondering if anyone could put my mind at ease....

Ive just bought a cheap second hand power amp to see if me vtrm preamp works well with a power amp. And it does.

The amp is a Matrix ukp 500.

Spec:

125w per side at 8ohm.

250w per side at 4ohm.

500w at 8ohm bridged.

Now, being used for a one socket bass cab, the bridge mode seems great - get really good power, one speakon out into one cab.

However.......... my cab is 6ohm (i know thats odd, but its a markbass 610). So is it safe to run it in bridged mode? or should i only be running bridge mode into an 8ohm cab?

I fully understand ohmage and 8ohm and 4ohm etc - but bridge mode has always confused me. 

Edited October 3, 2018 by la bam

[BassManGraham]

Running an amplifier into too low an impedance is definitely not advisable, the amp could run hot and you could blow the output stage of of your power amp.

[Bill Fitzmaurice]

There's no such thing as a free lunch. When you bridge you double the minimum acceptable impedance load. Running 6 ohms with an 8 ohm rated amp may not be a problem, not as bad as running 4 ohms, but watch the heat.

[la bam]

Thanks, i think ive got it now.

So, the amp can only give out a maximum of 500w.

It can achieve that by putting out 250w per side at 4ohm using both channel/speakon outs.

Or it can put out 500w through one channel/speakon at 8ohm, because if it went lower ohmage it would in theory be putting out more watts which is impossible, or itd burn itself out trying.

[casapete]

Also maybe worth getting your cab checked, as some official ratings can vary a bit I.e. if it is actually a bit less than 6 ohms you’ll know it’s not a good idea. The bridged thing has confused me sometimes too!

[la bam]

So, if i bought an amp which could run at 2ohm - like the QSC 1450 - that would mean bridged it would run at 4ohm, which would make it safe to run my 6ohm cab?

Or is it better just to get a bigger amp and run just on one channel?

[Bill Fitzmaurice]

Read this, it may help:

https://billfitzmaurice.info/forum/viewtopic.php?f=10&t=19292

[la bam]

That's why I've hardly ever bridged.

Ah well....bigger amp it is!

[Ghost_Bass]

Bigger amp (or one that'll go down to 4Ohms bridged) would be the safer option. you don't know the tolerances of the amp or the real impedance of the cab. You can check the impedance of your cab by mesuring it's resistance with a multimeter (on the ohm setting) then multiplying the reading by 1,3 should get you in the ballpark of the actual impedance of that cab.

[obbm]

I used to run an Epifani UL310 (5.33-ohms) on a QSC PLX-1600 which was fine bridged at 4-ohms.

[Phil Starr]

Why not email Matrix http://www.matrixamplification.com/

[la bam]

The matrix new range looks really good, and in time I'll probably go for that, but £500 - £1000 just for the power amp section doesn't really make it good value compared to what you can get at the moment.

Usual case - if I had the cash it's be a no brainier, but im looking for a cheaper alternative at the moment, so may have to go heavier etc.

[Phil Starr]

I just meant why not ask matrix if the amp you have will work with 6ohms. It has a class A/B Mosfet design so depending upon the current handling of the output transistors and the protection circuits it may be fine. They will be able to tell you. It's not a huge miss match.

[la bam]

Good point. I'll send them an email.