todays question

[AP Zoutes]

We know impedence rise effects the ouptut of an amp. By what I've heard you can have a rise of 30% or more...So why are more of you and/or competiters not using amps like the Alpine PDX, JBL, Jl Audio that do the same power from 1 to 4 ohms therefore eliminating the power change caused by impedence rise.

[ChevyBoy]

cause they dont make an amp that is as nice lookin and reliable like fosgate jbl has some power but theyre ass ugly..... :V

[AP Zoutes]

I like how the alpine pdx's look and they are stcakable. but that is all subjective what about performance

[AP Zoutes]

anyone else on the PERFORMANCE side of this question....ie ; If I run 2 Alpime pdx1.1000 on a two ohm load and the rise goes to 3 ohms I'm still getting 1000 watts rms or A jbl BPX2200.1 where the power goes from 1850 @ 1 to 2450 @ 4 actually going up as the impedence rises wouldn't a setup like that give better performance then an amp that loses power as imdedence rises

[Slinky]

id say it would be better performance but i wont buy one of those amps cause i dont have that kind of money.

[Audio Doc]

It would depend on the slew ability of the PS.

Ie. You do a sweep. As the impeadence rises can the PS topology adjust the rail voltage fast enough.

Since there are no posted specs on this sort of thing for any of the manufacturers doing this, I would say take the financially safe route, and assume _no_

Just assume for now that that type of PS topology is designed for adjusting to the nominal load and doesn't move much from there.

Clever thought though, maybe I should call JL and ask them about their tests on the RIPS circuitry.

- Matt

[AP Zoutes]

I was thinking small leaps...looking at the JBL on-line manual there is a switch for running 2 ohm mono and above or below...so I wasn't thinking a big leap like covering the spread from 1ohm to 4 ohm but I was thinkin in the case of a pair of SI mags wired and amp selected for 2 ohms being able to cover the imp rise and have no less then 2000 wattts.

Also, this is a silly question but I haven't tested it yet so I thought I would ask, Is impedence rise less of a problem with a single amp running a single sub as opposed to a single amp running a multiple. It seems to me logically you would have less imp rise per sub compared to a multiple of subs on the same circuit. Would you know if I am right about this.

[Audio Doc]

In the case of the JBL is't not automaticly regulated. As you said it's switched by the user. Thus switch position would dictate the fixed rail voltage increase/decrease.

I would find your impeadence rise, and try and get away with rounding it up to the closest switch setting. Ie. 3.6 ohms - set for 4 ohms. If you can't get away with it, go down a step.

You initial idea was to regulate the impeadence and adjust accordingly to maintain a consistant output from the amp. But the amplifier you chose for example does not do this. JL Audio system for example R.I.P.S. technology *does* do this. But again my concern would be that it doesn't act fast enough to constantly change the rail voltages to suit the load. I believe it automaticly adjusts to a 'nominal' impeadence it sees on average. It may be somwehat effective, but how much I cannot tell you.

On your impeadence rise question, test it. Or perhaps move that aspect of the question over to the sub forum where it may be better served. An amplifier stage only acts on what it has been presented (the load). The load itself is dictated by your subs in this example, and thus I would see it as a subwoofer question.

Hope this helps.

- Matt