Newbie help needed - amp/sub

[Chippa02]

Hi All,

New to tackling some basic improvements to stock system and learning for myself along the way but need some help from the more experienced people

I have an older 4 ch Pioneer bridgeable amp ( 1000w class D - ice) and wanting to hook up sub correctly. I have wired in to rear speakers a basic line level converter with RCA's to amp.

I have read/watched many vids regarding adjusting gain with multimeter to achieve an acceptable voltage output from channels.
My question is if I bridge two channels for sub will my volts equation change if bridging ?? I.E amp is 75w RMS per channel and sub 4 ohms for one channel calculation...or do I have to use 150 x 4 to get correct volts calculation.

Amp has two gain controls (A & B )

Hope it's not a dumb question..thanks in advance for any advice

Cheers

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[1aespinoza 10+ year member]

Hope it's not a dumb question..thanks in advance for any advice

Use the sub's ratings for this. If it is 750w rms, 2 Ohms. 750x2=1500. Square root of 1500=38.72v. That is the A/C voltage you will look for coming out of the bridged channels. Gain A should control fronts.

 

[Chippa02]

Use the sub's ratings for this. If it is 750w rms, 2 Ohms. 750x2=1500. Square root of 1500=38.72v. That is the A/C voltage you will look for coming out of the bridged channels. Gain A should control fronts.

Hey thx for the reply....every video I've watched has always used the RMS rating from the amp per channel...not the Sub which in my case the sub is 250w RMS /750w peak power ???

 

[1aespinoza 10+ year member]

250w RMS

Multiply the 250 by whatever resistance you wire it to. Always use RMS.

 

[1aespinoza 10+ year member]

reply....every video I've watched has always used the RMS rating from the amp per channel...

Yeah, I do not understand that thought process either. The sub is the one that will be in danger of failure, so using it's ratings just seems like the logical thing to do. Maybe it is to find the clipping point but you need more than a multimeter for that. On that note, that is why it is optimal for the amp to be able to handle at LEAST the RMS rating of the sub/s you are using. This will keep it far from clipping territory. Just practicing restraint and controlling the volume is not enough. That one song will eventually play and one will crank it up.

 

[Chippa02]

Yeah, I do not understand that thought process either. The sub is the one that will be in danger of failure, so using it's ratings just seems like the logical thing to do. Maybe it is to find the clipping point but you need more than a multimeter for that. On that note, that is why it is optimal for the amp to be able to handle at LEAST the RMS rating of the sub/s you are using. This will keep it far from clipping territory. Just practicing restraint and controlling the volume is not enough. That one song will eventually play and one will crank it up.

Ok thx for the explanation, as I'm only running the sub off the amp I'll set it up for 2 ch mono (300w x 2) and use 250rms (sub) x 4 ohms to get my volts calculation to set the gains..
If I've missed anything please let me know...thx for your help

 

[1aespinoza 10+ year member]

Ok thx for the explanation, as I'm only running the sub off the amp I'll set it up for 2 ch mono (300w x 2) and use 250rms (sub) x 4 ohms to get my volts calculation to set the gains..
If I've missed anything please let me know...thx for your help

Looks like you got it down. Good luck.

 

[Chippa02]

Looks like you got it down. Good luck.

Well I've wired everything up correctly but the sub is hardly moving....I checked voltage out of line converter which only measured 0.5V AC.
I tried another line out converter and the output was the same for both...am I missing something??

 

[1aespinoza 10+ year member]

Well I've wired everything up correctly but the sub is hardly moving....I checked voltage out of line converter which only measured 0.5V AC.
I tried another line out converter and the output was the same for both...am I missing something??

Adjust the gain on the amp to 0.5v.

 

[Chippa02]

Adjust the gain on the amp to 0.5v.

The amp gain adjustment goes from 0.4v - 6.5v...(max 26v)..does not matter where I set gains, the sub doesn't move much.

One thing I did notice is when I only had one rca plugged into amp the sub actually seemed to work better...not a huge jump in performance but definitely made a difference...

 

[1aespinoza 10+ year member]

The amp gain adjustment goes from 0.4v - 6.5v...(max 26v)..does not matter where I set gains, the sub doesn't move much.

One thing I did notice is when I only had one rca plugged into amp the sub actually seemed to work better...not a huge jump in performance but definitely made a difference...

Did you plug into the Front RCA inputs? Also, is the amp 150RMS bridged per channel? If it is, then you will have to target 24.5vAC per bridged channel to avoid clipping.
Are the subs single 4 Ohms?

 

[Chippa02]

Did you plug into the Front RCA inputs? Also, is the amp 150RMS bridged per channel? If it is, then you will have to target 24.5vAC per bridged channel to avoid clipping.
Are the subs single 4 Ohms?

The HU has no RCA outs hence using LOC.
Tapped into left and right rear speakers to connect LOC, used 9v battery to check correct wiring +/-.
Ran 50hz test tone at 75% vol on HU and flat EQ etc...used MM to check LOC output voltage (0.5v).
Amp is Pioneer PRS 4200FD 4ch...bridged in 2ch mode is 300w x2 which is how I have wired sub...
Sub is 12" Alpine Bass 250rms SVC 4ohm

 

[1aespinoza 10+ year member]

Sub is 12" Alpine Bass 250rms SVC 4ohm

Is it 1 sub or 2?

 

[Chippa02]

Is it 1 sub or 2?

Just one Sub...nothing else

 

[1aespinoza 10+ year member]

Just one Sub...nothing else

Got it. Then the original 250wx4 Ohms still stands. Will you be using the front bridged channel or the rear?