Amplifier Birthsheets/Birth Certificates (PDX-5) Trust it or not?

[West]

The amp comes with a form from Alpine stating the following:

Load impedance: 4ohmn

Test Voltage: 14.4V D.C.

Actual test measurement

TEST /// Specification /// Actual

Output Power (RMS-per channel x 4) /// 75 W min. (full range) /// 97W

Output Power (RMS-per channel x 1) /// 300 W min (subwoofer) /// 414W

One member felt that this test was not realistic. I am inclined to agree, but wanted further explination from others...

Is the test garbage, since a car supplies 12 V of power and Alpine tests the amp at 14.4 V?

Can anything be gained by this stated information?

Has anyone done their own analysis to confirm what PDX-5's are really capable of?

Click to read more...

 

[Sleeklsc 5,000+ posts]

A car supplies 12.5~v when off, when on it'll supply 13.8-14.4v. Chances are the amp will rarely see 14.4v. You'd prob see 75-85rms per channel and a little over 300rms(sub) out of the amp @ normal charging rate. So under normal conditions it does rated, not what the bs say's unless you maintain 14.4v's.

 

[brynm 10+ year member]

A car that is running is actually putting out from 13.5-14.5V that is why many manufacturers use the 14.4v rating (not to mention it boosts their numbers some).

 

[Dirtrider4eva 10+ year member]

its a decent test, but doesnt show distortion numbers. it could be pushing out that power, but at what thd? 5%? 10%?

then you also have to look at it is getting a continual 14.4, when driving it is usually fluctuation with when you turn on the A/c, wipers, etc, but average around 14.4

finally, musical impedence is ever changing, and the speaker will rarely even see that power. thats where the efficiency of the speaker kicks in and make up for the impedance gain.

 

[Sleeklsc 5,000+ posts]

A car that is running is actually putting out from 13.5-14.5V that is why many manufacturers use the 14.4v rating (not to mention it boosts their numbers some).

13.5 is low esp w/ little to no acc 's on.

My 130k alt was putting out 13.3-13.4 w/ no acc. Put a new one in and it doesn't drop below 14 even with the stereo on.

 

[West]

This raises further questions for me... So will the gain set by the amp fluctuate as well based on how many volts are supplied to the amp?

And if this is the case, should I set the gain with the engine on so there is minimal distortion?

 

[West]

Should I consider upgrading the alternator? Who makes the best one?

 

[Sleeklsc 5,000+ posts]

Set the gain with the car running and leave it there, you'll be fine.

Should I consider upgrading the alternator? Who makes the best one?

I wouldn't worry about an alt with that amp. My alt was old and underperforming, that's why I replaced it. Still have it as a spare though.

 

[Dirtrider4eva 10+ year member]

it depends on power and what vehicle you are running.

In my 00 celica, it has a 90/100 amp alot, and i have a 55ah battery up front, big three, and a stinger spv69 in back.

Off my current system of running about 1.2k of about (50-65% efficiency), and i drop to about 13.8 at idle. never under 14v when driving.