general sub advice

Now please don't take any offense as I am not trying to disrespect you in ANY way however I'm guessing you are more knowledgeable with home audio however car audio is an ENTIRELY different situation. I will respond in bold to your comments below.



The volume control..I was answering on the implied fact he doesn't turn the volume control down.

It does appear he keeps it cranked up however we'll have to teach him that proper setting of input sensitivity and restraint with the volume control are necessary factors to keep from blowing any sub.

Don't understand "In any case a more common dual 2 ohm or single 4 ohm sub would do the same thing as a dual 8 ohm". He appears to be running two channels of output to the sub, so assuming one driver running dual VCs in series is out. So a 2 Ohm is half a 4 Ohm, a 4 Ohm is half a 8 Ohm, and I understand those are "nominal" resitances that vary with frequency. Amps tend to clip a lot less at seen higher impedance loads, but of course a 16 Ohm load isn't really ideal either. If he bridged the amp, and ran a dual 4 in series, that would be a 8 Ohm load, or just a single 8 Ohm driver, either would limit the output current of the amp.

The MTX 801D is a "mono" amplifier. Also, 8 ohm dual voice coil "car" subwoofers are not very common which is what I was referring to.

Efficiency of the driver also comes into play, one with a SPL of 93db at 1 foot will require a lot less power to drive to intolerable volume levels than one with a 88db SPL. Lots more headroom in the amp before it starts squaring off the peaks.

Very true however you will find that subwoofers designed for "car" audio tend to be very inefficient since most people prefer/only have space for smaller enclosures. In order to give consumers what they want car audio manufacturers build these high excursion behemoths that handle TON's of power in small enclosures but you sacrifice efficiency of course.

Was going on the 10 inch sub, since space in tacos isn't all that much.

True again but he actually mentioned somewhere down the line that he has a Corrolla!

How about this one: http://electrovoice.com/products/307.html

There's several sizes available, of course the bottom end changes with driver size, the cabinet size and type, construction, mounting, resonant frequency and damping effect of the envorment it's firing into.

You're going to be hard pressed to find ANY 10 inch sub that'll honestly go below 100hz..and if you do, they're going to be rated down there at -3 or -6db (or worse), or their distortion level is so high you wouldn't want to listen to them.

Actually there are a lots of 10 inch and several 8 inch high excursion car audio drivers that can play down as far as 20hz with authority and distortion levels that are inaudible (you also get a pretty good amount of cabin gain in a car which helps a lot). If I can find it I will post a picture of RTA graphs showing my JL Audio 10W7 playing a sweep of Pipe Organ notes down to 18hz

Again my intention is NOT to disrespect you in ANY way so please don't take offense to anything I have said!

 

Oh heck no I'm not gonna take offense...it's excellent to hear from someone that knows something about this! That's how we learn!

 

Wow! You guys were busy in the 2 hours since I left work!

To clarify a few things, last sub I had was a dual 4, wired in parallel. I just ran 1 set of wires from 1 "channel" on the mono amp to the box, and split it to both voice coils inside the box.

The volume on the head unit is always relatively low. The car is at my in-laws at the moment, but it's rarely above 10-15. Even that is usually only for radio or very quiet MP3's. Most CDs and MP3s make me keep the volume around 5-6 max. (BIG difference from my truck were it's usually between 15 and 25! )

The measurements for my current box are: 12" tall, 19" wide, 11" deep with a 9 1/4" diameter hole for the sub.

I'm not really locked into $100 or less. I could save some more once the paychecks from my new job start rolling it. My problem is going to CC, BB, Crutchfield, etc and having one of their "experts" or "installers" sell me something for $500 and have it take a crap 6 months or even a year later. Then I've basically just pissed away a truck payment or mortgage payment if that makes sense. And right now, with 4 subs blown I'm hesitant to put that much money into it!

Yeah, that's want I'm thinking... Well, either that or my sub is pushing more than 600RMS @ 2ohms I suppose.... I'm so confused!

Yeah, again as I mentioned above it's mainly just that I don't want a $400+ paperweight this time next year. I mean, they don't work well for holding tools or anything less, and are kinda expensive for door stops!

Yes, you are quite famous sir! I was honored that you posted here! Hell, I didn't even know you were on this forum!

I think I get the gist of it.... Ignore peak, focus on constant/RMS power, and the sub must have been grossly over rated! Assuming I'm running at 1/4 volume to 1/2 volume most of the time the amp should have been pushing around 400w, maybe 600 max then correct? So if it was a "true" 600w RMS sub it should still be working.

Would I also be correct in assuming that having the gain cranked up wouldn't be that big of a deal with lower volume settings? I don't have the car here to check, and it's mounted under the rear deck behind the seats with 5" bolts so it's kinda hard to see anyway.