Bridging 4 Chan. ~ Morels, Gotta Hold Back Some Wattage! Check My Calculations Please

[frankiebones 10+ year member]

ok, i have the morel hybrid ovation 6 in the front. i am only using 2 of the 4 channels to power it bc i wanted the speakers to break in nicely for awhile before i either bridged or upgraded the amp...

thanks to some advice from our hall monitor ngsm13, i have decided to bridge my amp. did i say hall monitor? i meant hard-working moderator...bring it on my mid-western friend....

what had concerned me prior to this is that the rms rating of the components is far less than the output of the amp when bridged. however, i am going to describe what i would normally do using a DMM to set gains, and then, without a doubt, you guys will tell me how this is incorrect, thus saving my equipment from myself.

everyone who has morels has said that they need above and beyond the rms rating if run passive but it doesnt mean i am going to risk my only source of headbanging during my last year of law school finals.

got all the bullsh*t behind us (can u tell i have ADD?), lets look at the specs, my calculations, and the assumptions i made in inputing values into those calculations.

the morel hybrid ovation 6:

Nominal Impedance 4 Ohm

Power Handling 160W

Max. Transient Power Handling 600W

for the sake of being thorough, here are the specs for the individual drivers:

WOOFER:

Nominal Impedance 4 Ohm

Power Handling 160W

Max. Transient Power Handling 600W

Morel Tweeter:

Impedance 4 Ohm

Power Handling 110W

Max. Transient Power Handling 300W

Kicker KX650.4

RMS Power in Watts, All Channels Driven

@ 14.4V, 4Ω Stereo,

@ 2Ω Stereo,

@ 4Ω Mono,

@ 12.5V, 4Ω Stereo, 0.085% THD+N 4 x 70

@ 2Ω Stereo, 0.5% THD+N 4 x 135

@ 4Ω Mono, 0.5% THD+N 2 x 250

Both from using the voltage meter on my head unit, and using a quality DMM to test what the actual voltage is at the amp, i almost always get 13.5V on average, with the many peaks and valleys in voltage to be expected from electrical components turning on and off throughout the car.

i spoke to someone at kicker, and in between the output ratings they gave for 12.5V and 14.4V, the increase in the amp's wattage increases at a steady rate.

therefore, if i wanted to use the most accurate measurement of my voltage, i would use its output at 13.5V, which is basically the average of the 2, (250 + 325)/2 = 287.5W x 2 @ 13.5V, 4Ω Mono.

multiplying this by the impedence and taking the square root of the resulting value gives us the voltage to shoot for as 33.91.

using the unrealistic output @ 14.4V, i would get a value of over 36 to use when putting the DMM to gain control duty.

while i have seen 14V, i would guess its better to undershoot the max unclipped output until i get my hands on an oscope.

HOWEVER, that still leaves us with the little problem that our equation did nothing to take into account the fact that the speakers are not technically rated to handle that much, although people have sworn up and down that they can.

should i use the 12.5V output for starters?

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[djman37 5,000+ posts]

better us a DMM to find out car ON voltage...that's what you'll really be using.

 

[jmanpc 5,000+ posts]

thanks to some advice from our hall monitor ngsm13, i have decided to bridge my amp. did i say hall monitor? i meant hard-working moderator...bring it on my mid-western friend....

that was me who said it would be a good idea to bridge it //content.invisioncic.com/y282845/emoticons/crying.gif.ec0ebefe590df0251476573bc49e46d8.gif

 

[jmanpc 5,000+ posts]

Heres what I'd do if I were you.

Set the gains very low for starters, and slowly turn the gain up until you can notice the speakers reaching their mechanical limits, and make sure the voltage doesn't exceed 33.91...

 

[frankiebones 10+ year member]

that was me who said it would be a good idea to bridge it //content.invisioncic.com/y282845/emoticons/crying.gif.ec0ebefe590df0251476573bc49e46d8.gif

this is true, and owe u thanks as well. however, a lot of people told me to bridge it, he was just the first to get the misassumption out of my head that bridging it would require running another wire through the door to the speaker.

 

[frankiebones 10+ year member]

better us a DMM to find out car ON voltage...that's what you'll really be using.

i have the pioneer deh-p7800mp HU, which has a voltage meter that u can choose as ur display background.

also, my DMM is a good model (it was marked down at sears from ~$170 to $130 so its no radioshack DMM thats only accurate +/- 18%, if that).

i have never thought to measure the voltage with the car off, if thats what u mean, for obvious reasons, but thanks for responding and making sure.

 

[frankiebones 10+ year member]

Heres what I'd do if I were you.
Set the gains very low for starters, and slowly turn the gain up until you can notice the speakers reaching their mechanical limits, and make sure the voltage doesn't exceed 33.91...

when you say to listen for indications they are reaching their mechanical limits, do u mean in ways other than distortion?

i have my doors sealed and dynamatted very very liberally, so its a very tight sound in the first place. any distortion would be immediately noticeable.

however, if u mean that i should listen for things involving the actual sounds the cone makes, i assume as it gets to the pt where it cant move fast enough to cool itself, im not sure i would notice.

moreover, im not sure i would want to take the chance that i might notice, even with the sub off, and everything flat and defeated.

 

[96GTIVR6 10+ year member]

****... you were talking about doing this like 2 months ago. Glad you finally made a decision. You should be fine running the amp bridged to those speakers, what I would personally do is go out and connect it up and see what you end up with... You shouldn't harm your speakers unless you have things set horribly wrong. JmanPC seems to have hit things right on, maybe set like you have figured out and then back off a little. They should be quite loud...