Search with no luck - Gain Question

[2008screw 10+ year member]

Here is my question

I have a set of BA Pro 60's rated at 125 wrms @ 3 ohms

I have a Alpine PDX.4-150 which will be bridge 300 wrms @ 4 ohms (Stable @ 3 oms)

What should my voltage target be on my DMM

(125 rms speakers x 3 ohms) sqr = 19.37

(300 rms amp x 3 ohms) sqr = 30

(125 rms speaker x 4 ohms) sqr = 22.36

(300 rms amp x 4 ohms) sqr = 34.64

Also, Alpine amps are usually underated. Mine did not come with a birthsheet for some strange reason. Should I just use the rms rating listed or should I bump it up a bit as the amp is most likely underated?

thank for your help

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[BEAVER.989 10+ year member]

24.5v

 

[2008screw 10+ year member]

24.5v

How did you determine that #

 

[BEAVER.989 10+ year member]

150W @ 4ohms... Might as well use all the power you have.

On second thought... I just re-read what you are asking... Why are you bridging this amp only to use half the power? Don't even bridge it, just use 2 ch. @ 24.5V.

 

[BEAVER.989 10+ year member]

Also, I'm not so sure that your amp is capable of running at 3ohms bridged. Better to be safe than sorry.

 

[2008screw 10+ year member]

Also, I'm not so sure that your amp is capable of running at 3ohms bridged. Better to be safe than sorry.

I called Alpine support and they said it will run anything between 2-4 ohms bridged.

300 wrms is twice as much power as 150 wrms. Why would you suggest using only the 150 wrms instead of bridging it? It makes no sense to me

 

[alxmlr789 10+ year member]

http://z13.invisionfree.com/The_Dumbster/index.php?showtopic=41

 

[BEAVER.989 10+ year member]

300 wrms is twice as much power as 150 wrms. Why would you suggest using only the 150 wrms instead of bridging it? It makes no sense to me

If you want to run 300W to each component, then by all means, have at it, but you're questioning whether or not to bridege your amp to 300WX2 and then only using 125WX2. This makes no sense to me.

 

[2008screw 10+ year member]

If you want to run 300W to each component, then by all means, have at it, but you're questioning whether or not to bridege your amp to 300WX2 and then only using 125WX2. This makes no sense to me.

I guess, I am asking in my OP, what factors do you use in getting the voltage to set your gains.

Do you take what you are sending from the amp, in this case 300 wrms (Bridged)and the speaker impendance, in this case 3 ohms and square root them to get 30 volts?

or what?

Also the other part about the amp being underated too

 

[BEAVER.989 10+ year member]

The more I think about it, the harder your question becomes. I'm a little thrown off by the regulated power supply and can see where you're coming from.

Honestly, in your situation, I'd set them by ear. Start with the gain at the lowest setting and turn it up until you can't take it any more. This should happen long before you reach 300W.

If you're not comfortable with that, go by the 2ohm (more conservative) method, which is 24.5V. If it's not loud enough, turn it up until it is, without going over 34.64V.

That's how I'd approach it, anyways.

 

[BEAVER.989 10+ year member]

Oh, and the under-rated part... Know way of knowing what to do there without a birth sheet, or bench test.

I think it's a moot point anyway, since you have all the headroom you need.

 

[2008screw 10+ year member]

The more I think about it, the harder your question becomes. I'm a little thrown off by the regulated power supply and can see where you're coming from.
Honestly, in your situation, I'd set them by ear. Start with the gain at the lowest setting and turn it up until you can't take it any more. This should happen long before you reach 300W.

If you're not comfortable with that, go by the 2ohm (more conservative) method, which is 24.5V. If it's not loud enough, turn it up until it is, without going over 34.64V.

That's how I'd approach it, anyways.

Thanks for the reply. I know, it is confusing. Just to be even more confusing, the PDX amps are rated the same for both 2 ohms and 4 ohms. Both are 300 watts rms per channel bridged. //content.invisioncic.com/y282845/emoticons/eek.gif.771b7a90cf45cabdc554ff1121c21c4a.gif

 

[LiMarc 10+ year member]

Let me bring this back to life for a quick question. Im planning on runnign a PDX 4.150 with just the fronts for the pro 60's and the back two bridged for a sub.

150W @ 4ohms... Might as well use all the power you have.
On second thought... I just re-read what you are asking... Why are you bridging this amp only to use half the power? Don't even bridge it, just use 2 ch. @ 24.5V.

This quote seems right to me since the speakers are rated at 125, 150 more than enough right.

Why would anyone run more the double the rated to the speakers?