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Discussion Starter · #1 ·
I'm relatively new to car audio as this is my first personal system, but I'm completely out of ideas as to what may be going on even after months of searching.

I bought a 600w subwoofer package back in March of this year which included a Boss CXXM1250 amp and an Audiopipe TXX BD1-12 sub. The BD-12 is a DVC sub rated at 600w rms and I have it wired at 2 Ohms. The amp is 635w rms at 2 ohms, so I figured it would be a perfect match. If you type in 600w and 2 ohms into an Ohm's law calculator, you get around 34 volts, so that's what I was aiming to hit.

Immediately when I got the system I tried tuning with a DMM but was only able to hit 6.5v with gain and bass boost maxed and head unit volume at 3/4 playing a 50hz test tone. Bass boost on the amp is 18db at 50hz, by the way. I figured the problem was my preamp voltage from my head unit, as it is a pretty crappy one I got for 30 bucks. I bought a PAC LD-10 Line driver thinking it would fix my problems. And it did, for the most part.

Now, with the line driver maxed, the gain, bass boost, and volume maxed, I am able to get a reading of 30.2v on my DMM. When I turn down the gain to about 3/4 of max I get the same reading, 30.2v. At that level my amp is clipping like crazy and sounds like ****. I also get a ton of alternator whine.

So I have a couple questions. 1) What do you think is wrong with my system? Is it my amp? My head unit? My line driver? and 2) Is it going to damage my sub if I am under powering it with an amp that is clipping that bad? I have no intention of running it this way for an extended period of time, just until I get my new amp here in a couple weeks.

Thanks for any help
 

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How is the line driver hooked up? RCA level or speaker level? Or are you referring to a line level converter?

I'm not familiar with BOSS amps, but I wouldn't count on anywhere near the rating printed, no matter what signal you feed it.
 

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Discussion Starter · #6 ·
Yeah, kinda figured the problem was my amp. Read online that it may be more like 400w at the best, but I'm inclined to believe DD at this point. 6.5v at 2 ohm is 21w. How the hell this thing got a 635w rms rating is beyond me. Oh well, getting a Planet Audio AC2600.2 here in a couple weeks anyway. Thanks for confirming my suspicions, guys. :laugh:
 

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Discussion Starter · #7 ·
As a testament to my noobishness, I have no idea the difference between "RCA level" and "speaker level". It's got RCA inputs for left and right and 2 dials to adjust the power driven through the exit RCAs. I only use the left channel though, because it makes the alternator whine a tad less loud and pushes more power through the one RCA.
 

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Your last post make it sound like a shorted or grounded RCA could be an issue.
Where are you getting the RCA signal from? A line driver? Factory radio or aftermarket headunit?
21 watts sounds way too low, even for that amp.
The 2nd channel is a big issue that most likely will carry over to your next amp, unless the Boss itself is at fault.
 

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Discussion Starter · #10 ·
Here's how I have it set up: RCAs from an aftermarket head unit to the line driver. Then from the line driver to the amp. That is getting me 30.2v. Originally I had RCAs from the aftermarket head unit right to the amp, which is what got me the 6.5v output. Also, as a reply to your second post, I'm guessing the dials on the line driver are sort of like gain on an amplifier, correct?
 

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I didn't realize you were referring to the dials on the line driver, but either way you have to crank the amp gains to get anything respectable?
That amp ~should~ function correctly w/o a line driver, even from a 2v HU. Most amps have the lower voltage in the milliamp range.
Seems like something else is amiss if you need to jack the input signal that high just to get results.
Then again could be the amp itself.
Ever tried the high level inputs? (speaker level) Just to see if you get the same symptoms, you could just [being careful] jump the RCA ends to the bare tinned wires to test.
A word of caution, turn all gains down before you do this or you'll get a surprise.
 

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Discussion Starter · #12 ·
No, I haven't considered that before. I don't really have the stuff here in my apartment to do that either. I do remember my head unit has a <1v pre amp, though, even though it claims 2v. I don't know. I'm wondering if it's even worth it at this point to go through the troubleshooting process if I'm getting rid of it in a couple weeks.
 

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Discussion Starter · #14 ·
Anything you would personally recommend? I'm looking for something that produces 1200w+ rms bridged or 600w rms x 2. I'm in college so I don't have a huge budget, I was hoping to spend 100 - 150 bucks. This thing claims 1800 rms bridged, so I was assuming it would at least do 1200.
 

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Should be able to get a solid [email protected] ohms IMHO.

The alternator whine is most likely a grounding issue, which is probably adding to the issue of the inability to get proper power form the amp.

HOWEVER, you are setting gains all wrong with the setup. The amp is sure to be over rated an incapable of producing rated power, so you shouldn't be using the DMM method to set the gain for a 600W output.

And with the voltage you're getting, the gain is set to "try" and get 450ish Watts from the amp, which is around twice what it can actually do.

I honestly recommend setting the gain by ear with the aid of test tones (and ear plugs). You should easily hear when the tone changes in the sub. Heck, you can visually see when the movement changes with the onset of 2nd and 3rd harmonics, if you just don't trust your ears.

And the new amp may do around [email protected] ohms, so again, I strongly recommend setting the gain by ear and/or sight with the aid of test tones.

What Is Distortion?

Using test tones to set amplifier gain

https://www.youtube.com/watch?v=WhrDqke8BKo
 

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Discussion Starter · #17 ·
Yeah, originally I was just tuning my amp by ear. I just figured this would be a more accurate way. I always use test tones, by the way. And you are recommending to try and set this amp to 450w correct?
 

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No, I said you currently have it set for around 450W, which as you can tell is clipped power. Amop probably does around [email protected] ohms, but such is not guaranteed, it may do 150RMS with the current electrical connections you have (power/ground), may do 250ish RMS (but I doubt such, unless you address the electrical to the amplifier).

Need to find the HU's maximum clean volume level, which you may well be setting the gain with the HU clipping the signal already for all we know. And as said, Bass Boost is generally frowned upon using. For every 3dB of boost, you are asking the amp to double it's power output. Doesn't take much before you are asking too much of the amplifier.
 
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