Blown Multiple Subs

[scotty3x3]

So I recently blew my second sub in a matter of about 2 months. The first lasted about 7 months or so and the most recent only lasted 3 weeks. The latter was an Alpine SWR-12D4 and again, it was brand new with a brand new Alpine M110 mono amp. I took it back and the shop swapped it out for me but while I was there, he told me a couple things that I don't understand or agree with.

Basically he says since I have a 4 volt radio (Pioneer AVH-4000NEX), that I should have the amp gain turned all the way down to zero and the I should crank the head unit as loud as I want to. The head unit maxes out at 40 and they say they have put meters on this particular unit, and it does not start distorting until around 37 on the volume dial. Basically saying that if I turn up the volume on the radio versus the gain on the amp, that it is better for the sub.

Seeing as I've blown two subs I'm inclined to take their advice but this is where I'm confused. If I turn my radio up to 35, as opposed to 22, and I achieve the same volume level, won't the amp be pushing the sub just as hard? I mean 50db (just a round number for arguments sake) is 50db whether the radio is at 37 or the amp is at half gain. 500 watts is 500 watts either way. So he must be trying to say that the amp is clipping and sending distortion to the sub. That's the only thing that makes any sense to me at all. But am I really to believe that an 1100 watt RMS amp starts clipping at half gain with 0db bass boost?!?! This just doesn't make sense to me.

Any light on this situation is appreciated.

Click to read more...

 

[keep_hope_alive Premium Member]

yes, the amp will clip at half gain when you give it more than 2V input. gain is input sensitivity and it's measured in volts. it's a setting where you determine what is the maximum input signal you will give the amp. with a 4V headunit you leave the gain at 4V and use the head unit volume (assuming you have a separate amp for the mids/highs and have it's gain also set at 4V). some people don't like this method because it is too safe and means you won't get rated power out of the amp unless you have songs with very strong bass lines. they will risk damage to the equipment in order to get as much bass as possible. the safer way to approach bass is to have more on tap than you need/want so that the equipment is always operated at a level comfortable for the equipment.

If you're running speakers off the head unit also then the problem changes because while the RCA output may be clean to vol 35 the speaker output is not.

what box do you have the sub in? specs on the box?

 

[scotty3x3]

Q Bomb 12 VL Single 22 x 15 x 13 1/2 1.8cu

That all makes sense, but the problem I have is believing that the sound I am getting now is anywhere CLOSE to 1000 watts RMS. Turning the gain all the way down on the sub amp and turning the "sub volume" on the radio up, at best, i would say is maybe 400 watts. So it's strange to me that the sub is rated at 1000 RMS and I can only safely use 400. RMS is "supposed" to be the safe level versus max output.

 

[los33]

Most of those q power subs cannot take more then 800 rms from what i seen. Whats the exact sub model you have?

 

[scotty3x3]

The box is "q bomb". The sub is an Alpine SWR12D4.

 

[BoomTaco64]

hate to break it to you but your alpine type r sub in not 1000w rms nor would i put that much power on that sub. its the same sub that they have been making for the last few years and magically the rms keeps going up every year. having your radio volume at its peak before distortion is best for the amp. i have tested many radios with o-scopes and DMM's and a lot of them will have a full output without distortion or at least 95% of the available volume. when you put a higher voltage into the amp the gain will not be turned up that much and the amp will work a little bit less in order to achieve the power you were looking for. Dont believe it, Test it your self and see the results. My factory 2001 toyota tacoma non tape, non cd player ratio had a 9v output on the speaker wires and un-clipped signal at full volume. My kenwood excelon kdc-x395 has no distortion on the rca outputs until level 35(Max volume) and i have the almost full 4v ac output at 34/35(3.943v ac). on the speaker wire output i get a full volume output un-clipped at 35 and get 9.258v ac from them.

 

[Jeffdachef 5,000+ posts]

Q Bomb 12 VL Single 22 x 15 x 13 1/2 1.8cu
That all makes sense, but the problem I have is believing that the sound I am getting now is anywhere CLOSE to 1000 watts RMS. Turning the gain all the way down on the sub amp and turning the "sub volume" on the radio up, at best, i would say is maybe 400 watts. So it's strange to me that the sub is rated at 1000 RMS and I can only safely use 400. RMS is "supposed" to be the safe level versus max output.

How loud your gonna get is based on the box. You bought a premade box cant hope to get that loud and low with such little port area. Your gains should not be at 0 normally its somewhere between 15-60% based on if your head unit preout voltage is true to specs. Learn to set gains with a digital multi-meter on a -6 db 50hz/40hz test tone.

To set it by ear, max the high pass filter for the speakers, put on a 50 hz test tone, and put the volume to 80-85% of the head unit's max. Then go to the amp and slowly turn up the gain until you can hear the tone of the bass actually start changing(this is distortion point) then turn it back down a few notches.

Also, if your electrical charging system is weak, you might need to do the big 3 upgrade. To see if its weak or not, turn on maximum AC, blast your sound system and use a digital multi meter to see how low your voltage drops. If your seeing 13V or under then you need to do the big 3 upgrade.(google it up)

If you have dirty bass boosted songs in your playlist, they will blow subs easily too.

 

[michaellane 5,000+ posts]

Lol they gave you that info because you are doing something wrong blowing your speakers.