• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

Running odd ohmages?

#2
jady said:
so if I have an 8ohm cab and a 5.3 ohm cab in parallel the total ohms are 3.14, could I run this with a power amp designed for 4 ohms or will this do damage?
Click to expand...

If 4 ohms is the amp's rated minimum load, that's what you should abide by. That's why the rating is there. I'm not saying it's 101% absolutely guaranteed that you'd damage your amp with that load; some ratings are more rigorous than others, some amps more forgiving than others, and sometimes you can get away with something for a short period that would be dangerous over the long term. But the chances of damage are too high for comfort, so why would you even consider doing it?
 
#6
Don't do it. As a rule of thumb, don't take that risk, as you might damage your rig.

Here's my alternative solution: If your amp is pumping out a good amount of wattage per side in stereo mode, why not just put one cabinet on each side? You'll lose some headroom, but you can still be loud.
 
#7
by all rights, my 212 should be a 4 ohm load, an ohmmeter actually reads it as 3.56 ohms. So in addition to running what's actually rated as a impedance too low for your amp, you have to take variance into consideration. it could come out higher or lower in real life.
 
#11
jonly said:
by all rights, my 212 should be a 4 ohm load, an ohmmeter actually reads it as 3.56 ohms. So in addition to running what's actually rated as a impedance too low for your amp, you have to take variance into consideration. it could come out higher or lower in real life.
Click to expand...

It reads lower because you are reading the DC resistance, not the impedance. Impedance is an AC value. When you throw an AC signal at that voice coil some of the energy gets stored in the electromagnetic field and that is what drives up the impedance to the 4 ohm range.

It does vary under operation through. But it will tend to stay above the value you measure with the meter.
 
#12
jady said:
Im thinking of buying a lds 3x8 hence the odd ohmage.............the amp will take a 2 ohm load in sterio but not bridged. Hmmmmm what to do?
Click to expand...

Don can give you any impedance that you want. He build a 3x8 for me using 12 ohm speakers, resulting in a nominal impedance of 4 ohms (which of course, would put you in more trouble than you would already be in with the 5.3). However, I would guess he could order 24 ohm 8's to give you an 8ohm 3x8 without too much problem. Ask him about it.
 
#13
12 Ohm speakers? I haven't run across any of them. I bet it's 3 16 ohm speakers. 5.33 ohms, and close enough.

In any case for a SS amp, running at lower ohms than rated should be they amp checks it's current and heat, and if they're exceeded it shuts down. I've seen testing specs that say as part of the QC to short the output and check the amp shuts down. No harm to the amp. They should all be so bullet proof, but you just don't see many that advertise how they torture test to be sure they have a solid field product.

I any case, I doubt any one could tell if you burnt out an amp because you picked an impedance slightly under the rating. So while it's still under warranty, give it a try,
 

Latest posts

Top Bottom
Back