When it doesn't fit anywhere else
 #151356  by Grateful Dad
 Thu Mar 17, 2016 8:49 am
I have a 700 watt maximum bass amp that pushes 450 watts into my 4 ohm speaker cabinet (1x15" Peavey Black Widow), and will push 700 watts into a 2 ohm speaker. My question is if I want to get the full 700 watts what do I do? Do I add a 2x10 in addition to the 1x15 to take the ohms to 2 ohms? Also how much of a difference in headroom/volume will it make going from 450 watts @ 4 ohms to 700 watts @ 2 ohms? I have called music stores but surprisingly no one seems to know much if anything at all about the watts to ohms relationship. If anyone knows how to explain in layman's terms this watt/ohm thing I would appreciate it! Thanks and have a grateful day!
Dave
 #151358  by schmidtz
 Thu Mar 17, 2016 10:42 am
Preface/disclaimer: I barely know what I'm talking about....

First, a pedantic note: the quantity you're referring to as "ohms" is impedance, which has "ohms" for units.
Grateful Dad wrote:if I want to get the full 700 watts what do I do
If you want to include your 4 ohm 1x15", you'll need to use another 4 ohm cabinet, and wire the two in parallel. That will result in 2 ohms of impedance.
Grateful Dad wrote:[h]ow much of a difference in headroom/volume will it make going from 450 watts @ 4 ohms to 700 watts @ 2 ohms?

In general, whenever you double your power ("watts" are the unit of power), you'll get an additional 3 decibels of volume, which results in a perceived loudness increase of roughly 1.23x.... not very much.

If you want to learn more about this, you'll have to refer to the relationship between loudness, power, and decibel change.


If you want to learn about the actual relationship between power and impedance, it will pay to learn about impedance itself (because it may go around masquerading as simple resistance, but there's a ton more to it), and then get in to Ohm's law.
 #151371  by gr8fullfred
 Fri Mar 18, 2016 7:57 am
Hard to imagine that 450 Watts is not enough. Should be enough to blow pretty much any speaker. Not sure what kind of gigs, venues you are playing, but 450 watts of bass amplification ought to do the trick in most any venue. In a bigger venue a direct out to the PA would be expected.

What are you trying to do?

You might consider a second cabinet of smaller speakers which might reproduce some higher frequencies that are preset in your instruments output. (like those harke's I used to see alot of).

A second identical or similar cabinet that is also 4 ohms impedance, connected in parallel would reduce your total impedance to 2 ohms and probably sound better than one speaker being driven to its maximum. Good luck!