Polk c300.2 Tuning - Oscilloscope Results

hondahirny

I've recently become the proud owner of a c300.2 and a pair of db804 8" subs. I built my first box and it's residing currently in the back of my Civic. Here's a pic of the whole setup, out of the car:
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I know, that's a mighty big cap I got there :eek: 1.5F is way overkill for a 300W amp, but it was on sale for $20 at Fry's Electronics, so can't beat that deal...

I brought my work o-scope home this weekend to see what truly is full power on my amp. The "birth certificate" the polk shipped with indicates 186w rms, with a minimum spec for the c300.2's of 180w rms. I disconnected the subs from the amp and fed a 40Hz tone through the CD player to the amp. I then cranked the volume on my HU until it was just below clipping. Take a look at the waveform:
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The RMS voltage reading on the amp is 27.2V RMS. With V-squared over R for the power calculation, that's 185W RMS output into 4 ohms. I was getting 14.2VDC to the amp at the time, according to the voltage reading on the stiffening cap. That's pretty darn close to the 186W the Polk techs qot during the quality control process!

Below, you can see two more images, showing clipping when the amp ran above the max volume used above:
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Now that i knew what the max volume was for that test tone, i tried running the amp with the subs hooked up. The db804's are spec'd at 180W RMS, so i thought they'd be a good match for the amp. I'm running them in a sealed box with 0.35cu ft per woofer, along with lots of polyfill to dampen those backwaves. When i cranked the volume to the same level that produced max clean power on the c300.2, the woofers were moving like mad! The Xmax on these subs is about a quarter inch in one direction. I was visually observing approximately half an inch of overall travel, which is right around that Xmax spec. At this volume level, the little subs looked like they were ready to jump out of the enclosure, but they took it. The amp/sub combo runs nicely, right to the ragged edge of power delivery.

The pics above show clipping of the amp. Now, i didn't dare raise the volume to the image of severe clipping, but the mild clipping is one volume level higher than the clean output available. When i raised the already loud volume one level higher, I could really hear a difference in the sound. This might be harder to hear while playing music, but a continuous test tone really brought out the clipping.

So, Polk really came through on this one. Their products have shown to perform as advertised. You guys got me sold on your products, for sure

kismetcapitan

I'm also running a 300.2 for subs - great to see independent test results back up a subjective great sound. Mine tested at 192W per channel per the certificate...but solid sound is solid sound and kudos to Polk!

PolkThug

Its a great 'little' amp. I'm using mine in bridged mode to push two Polk 15" DVC's.

bknauss

I wish all consumers would properly set gains like that! Good job man.

exalted512

bknauss wrote:

I wish all consumers would properly set gains like that! Good job man.

gain? Isnt that the volume control? I usually turn mine all the way up
-Cody

Sami

kismetcapitan wrote:

I'm also running a 300.2 for subs

Hopefully not in the GT-R!

hondahirny

I've been sold on Polk since i bought my first set of speakers from them... a pair of MMC690 6x9's. You certainly get what you pay for! I'm now trying to scrape the $$$ for MMC6500 for the front. I've been very happy thus far and I definitely like the geeky side of audio. Doesn't everyone have a toy oscilloscope?

denim

nice specs