Audio Systems: which amp for dual 12, dual voice coil, kenwood amp

Question
QUESTION: Hi there...

I am currently running a Kenwood 350W amp
http://www.precisioncarsound.co.nz/kenwood2.htm
(it's the second one)
bridged to a single 12" sub.. I just was just
given a pair of Phoenix Gold 12" subs in a single
box with wires coming out for both
http://forums.xbox-scene.com/index.php?showtopic=504658
(this site has the spec's for the sub)
and I also acquired a sony xm-4501 amp that
came with the subs..
http://129.33.22.12/release/XM4501.PDF (amp link)
I am just wondering should I use my Kenwood amp
or take it out and use the sony?
the only issue I have with using the kenwood
amp is that I only have a single spot to hook
up in bridged mode so I would have to connect
both pos' and both neg's to a single connection
each.. is this ok ..

Any help would be appreciated..

Thanks
Joe

ANSWER: I kinda got lost in the mix with all the numbers.  

But, the speakers are 4 ohm coils in dual.  Paralleled they give you 2 ohms impedance.

The Sony is a 4 ohm amp so you cannot connect the 2 ohm load to it without taking a dangerous course.

The Kenwood can handle 2 ohms in standard configuration but if you bridge it for mono drive it must have a 4 ohm load.

It is very dangerous to put a load (impedance) that is lower in ohms than the rating of the amplifier.  So, that should be your guiding light .  HIgher impedances are no problem.

Maybe this will help you figure it out; if not, let me know more and we can go another round on your question!

C



---------- FOLLOW-UP ----------

QUESTION: I appreciate the input...

I am still a bit confused about how you got the ohm reading
for the subs.. cause the dual voice coil amp on the forum says 1.9ohms on the first part which is the model I have the other single voice coil version says 3.64 ohm's...
if I wire the Subs in series they should be 4 ohms then, is this correct? assuming they are 4 ohms? is there a way I can check the ohm's on the subs myself with an volt/ohm meter? I have this but not completely educated on how to use it fully.

Thanks again

Joe

Answer
Yes. Impedance of a speaker is a function of frequency.  That normal rating is usually give at the frequency just above the free air resonance of the cone.  

And, it is generally about 10 to 15% higher than the dc resistance of the voice coil.  So, a 4 ohm speaker (as rated by the manufacturer) would have a dc resistance of a little less than the 4 ohms.

In subwoofers they often have two voice coils.  They can be connected in either series or parallel.  The do this intentionally so that the best amplifier connections can be made.

But, as previously stated, burnout of amps is often caused by the impedance of the speaker being too low for the manufacturers rated load impedance.

You are right.  A 1.9 ohm coil dc resistance would be a 2 ohm impedance.  If they are in series the impedance to the amp would be 4 ohms.  In parallel it would load the amp at 1 ohm.

Does that help?
C