Does the head units impedance rating affect the amps output? I find my audio sounded way better when I had the HK (2 Ohm) head unit as compared to the Kenwood (4 Ohm) head unit I am running now...same amp, same speakers...

Jim

 

What amp? What speakers? No way the HK unit is sounding better than the Kenwood. What kenwood HU do you have? What Bike??

 

A high current, low impedance, amp when matched to low ohm speakers generally will sound more crisp, better bass, less distortion. Basically it will sound better. Cheaper amps use higher voltage and lower amps and thus have higher distortion.

 

You are talking about amps and speakers but the only thing that has changed is the head unit....forget I said HK and Kenwood.... I know the amp output is affected by the impedance of the speakers but I wanted to know if a 2 Ohm head unit and a 4 Ohm head unit make any difference to the amp? If you read on, I think the answer is no....

I used the DIMM to set my gains on the HK, determined my voltage at 3/4 volume by following the formula for amp output (2x70=140) X and speaker impedance 4 Ohm and adjusted accordingly....23.66 (stopped increasing the gain until I hit that setting).... I could have kept turning it up, no problem.

But the Kenwood will not hit 23.66 even with the gain turned all the way up. I had a Sony HU a while back with this setup, I could dial in the gain with a DIMM to 23.66 (there was plenty left) and it sounded great.. that was a 4 Ohm HU as well...I think I just answered my question, so I guess it has something to do with my Kenwood...the 2 Ohm HK and the 4 Ohm Sony sounded fine and could exceed the recommended DIMM setting....the Kenwood can't.

Maybe I'll try a set of 2 Ohm speakers...my amp is rated for 2 x 125 at 2 Ohm.

I didn't specify what speakers or amp I was running at first because I find the the conversation usually takes off on a tangent as to what speakers or amp is best....which means the fact that the setup sounded great with the HK and I was more than happy is usually forgotten. So I have a pair of Hogtunes 5.25" 4 Ohm speakers, an ELF 2125EX Amp (which has great FM reception for some reason) and a pair of Hawgwired Tweeters that fit in the gauge holes....my system has gone from sounding great to crap and all that changed is the HU.

I don't want to play musical head units, but I would go back to HK if it wasn't for the fact that I've had two fail on me so far. I think my next step will be to try a set of 2 Ohm 6.5's. I've put the Hogtunes speakers and Hawgwired tweeters up for sale in the Classified Section.

Jim

 

The head unit's impedance is NOT affecting the output of the amp. Only the signal of the head unit affects the output of the amp and this can be corrected by the use of the gain setting. The OP's Kenwood having a 4V signal vs. the 2V signal on the HK means lower gains and less noise. That said I'd still like to know what set up and what bike?

 

Ahhhh Got it now brother . . I think your issues lies with the settings on the Kenwood HU. PM my friends HAZE or AAWAV and they can tell you exactly how to set up your HU. The Kenwood is tricky!

 

Powered with the same signal, 2-ohm speakers will "get" double the power that a set of 4-ohm speakers will get. They will sound louder. But not double - that's not how sound/volume works. And the HK unit - as you know - can handle the 2-ohm load. Infinity Kappas and Reference are 2-ohms, if you're looking for something readily available (and good and affordable). So basically, if you don't touch the volume control, and swap back and forth between 2- and 4-ohm speakers, the 2-ohm speakers will sound louder. Add an amp to your 4-ohm speakers and Kenwood and you'll be jazzed.

 

to OP:

you are using the wrong calcalation - see sticky thread regarding DDM.

in short: you need to do Vac=SQRT(P*R) where P is 1 SINGLE channel.
cannot find the exact RMS specs on this amp, but let's say
75W at 4 ohm and 125W at 2ohm...

4 ohm > V=SQRT(75*4)=17.32Vac
2 ohm > V=SQRT(125*2)=15.81Vac

Trust me... I have an O-Scope and have been over this over and over again.
When I dialed in using DDM to the Vac with the 2 channel Watts added together, the signal was heavily distorted on my O-Scope.

put 1KHz sine on the HU, set Kenwood at 70-80% of max volume (assuming you use RCA pre-outs!), EQ all neutral (called "flat"), no enhancers at all (like loudness, etc) and dial in.

 

That was the sound of my head exploding....using your formula
my actual amp is 4 ohm > V=SQRT(70*2)=11.83Vac....

I'm confused, the sticky says you take P=70/2(140) then multiply it by R(4) which gives you 580...the SQRT of 580 is 23.66Vac...with the new Kenwood HU I can only get to a little over 21 Vac...the sticky says ...."or as close as you can get"...so I left the gain maxed out. On my old Harman Kardon it could surpass the recommended Vac setting no problem...actually had the gain set at about 6.

All my Kenwood HU settings were flat, no enhancements...bass boost on amp off... Elf 2125EN amp is set to "Full Pass" or something like that. It's in between the LPF and HPF detents. Using the 1Khz tone I Set the gain to 21.xx Vac which is the max I could get...couldn't get to 23.66 Vac. Adjusted the HU settings to my preference after I was done. Turned on the Bass Boost on my amp.

End result, I have to crank it to hear it over the wind noise and exhaust, and it sounds like crap. When I had the Harman Kardon HU it sounded great and I actually had to to turn down my gain to about 6 to achieve the proper Vac. My wife, riding beside me on her Sporty even mentioned that it sounds like crap

Don't know what's going on, only change was the head unit...as I mentioned before I might switch to 2 Ohm speakers to take advantage of the P=125/2(250) ability. Any 5.25" aftermarkets out there other than Hogtunes for 2 Ohms? How about 6.5" in 2 Ohm?

EDIT...just realized that my Hogtune speakers are 5.75 Ohms not 4 Ohms...which drops the power output from the amp even more

Jim

 

TRUST ME, use these numbers, assuming 70W at 4ohm:
the original DDM described method is incorrect, Nutz even "admitted" it LMAO.
the way it is described is for when you bridge 2 channels, this is NOT the case.
If you go to the end of the thread, you will find my notes/comments

4 ohm > V=SQRT(70 Watts * 4 ohm)=16.73Vac
2 ohm > V=SQRT(125 Watts * 2 ohm)=15.81Vac

now if the speakers are 5.xx ohm, it is a different situation and there is no way to determine the actual RMS Watts without proper tools.