I built a custom box for my son's car. I installed his system in the car a little over a month ago. The system was bangin for about a month. Now, both subs are shot. JL is going to replace them under warranty, but I want to know what killed them. I attached a couple pictures of the system. The box has each chamber separated and sealed. The one picture is the box under construction. He has 2-12" subs in the box & calculating the air space (tough with all the angles) is about .80. Is this too small for the 12" subs? Man, I want the kid to enjoy his music, not blow subs every month. I tried to convince him to go with 10" for the well, but you know how that goes...
I find it odd that both subs are dead (don't move up & down at all). I read that one thread about distortion causing heat build up and killing coils. Not sure if that's what happened - I am not an expert on audio, but I am trainable!
Thanks,
Corky

 

I have two alpine 12's in a box similar to that in my comvertible. And they have been thumping loud and hard for 8 months now. And never had a problem. The only thing I can think of is if your amp is pushing to much power. Or you don't have the amp adjusted right. Or the subs are 4ohm and you wired them wierd and now it's something else and just fried them. I had the same thing happen in another car where the speakers where 8ohm and if you added an aftermarket radio with 4ohm output it would fry the speakers. Adam :-)

 

It would be nice to know alittle more info on the sub and amp and how they are wired.

Are you sure its not the amp that got fried?

Kindof weird how both subs crapped out at the same time...

 

I agree, really weird that both are shot. I returned the amp to MTX & got it back last week - they said nothing was wrong with it.
I wired the amp with #4 cable directly from the battery (+ & -). RCA from panasonic deck to amp. AMP is a MTX TC6001 http://www.mtx.com/caraudio/products...ers/TC6001.cfm
Subs are 2 -12W3-V3 JL Audio 300w 4ohm
http://mobile.jlaudio.com/products_s...p?series_id=25
I simply wired each sub to each output on the amp. So, 2 outputs on the amp & connected 1 sub (+,-) to each output.
Thanks,
Corky

 

One, the box is way small for those subs, according to the JL site optimal is 2.806 cu. ft. plus the amp is too small for those subs, according to the chart on the JL site, optimal power is around 350 watts for just ONE speaker. The amp is clipping sending straight DC voltage to the subs causing them to travel as far as they can holding the there for a moment creating heat in the voice coil.

 

Good thing you went with JL. Any other brand and you'd probably be up the creek without a paddle.

 

Thanks for the input guys. You know, I went to Tweeter and asked for an optimum setup. The sales guy was spouting all kinds of techno-babble & that should have set off a red flag.
From what you guys are saying, we should use the existing amp and enclosure for a SINGLE sub (take out the internal separator). If we want to add an additional sub, we would either need a bigger amp, or a second amp to drive the second sub (and a bigger enclosure). Did I undestand that correctly?
Thanks,
Corky

 

have you figured out what the box size was without the seperator? And if you wanted to use 2 subs, you would need both another amp (actually would go with something other than MTX, but that's my opinion) and a bigger enclosure. I'm running 2 10" Pioneers in a box that has a total of 2cu/ft split in the middle with each side being 1cu/ft with an old Phoenix Gold M44 (40x4) wired 1ohm bridged pushing around 400watts to the subs and it hits pretty hard in itself (according to the manual that came with mine, bridged into 4ohm is 160 watts, so I've basically raised my output 4x which I'm pushing this amp too hard). You would end up needing a box 4cu/ft for optimal on it for it to work the best with at least 600 watts RMS for both speakers. The JL 500/1 monoblock would be a good one to use for the subs.

 

If that amp is running at 2 ohms there's no need to get another amp. I'd definately check out the air space in each chamber, you might need to make the box a little deeper, or just hook up one of those subs and send the other to me.

You can find the airspace by using packing peanuts or something of the equivilant. Just find a box 12"x12"x12" and you have 1 cubic foot. Fill up the chamber in your subbox, and then fill the 12"x12"x12" box to find how much space is there.

I'd definately make sure those woofers have the proper airspace, even if you have to use one it will still sound way better than alot of other systems, although I think you'll really have room for both. Let us know what you find out.

 

Well, if the subs want 2.8 cu/ft of airspace for just one, then he would need 5.6 cu/ft for two, can you even fit a 5.5 cu/ft box in the back of an f-body? Also, I still don't trust the amp, $250 amp that MTX "says" will do 600 watts at 2 ohm or 300 watts at 4 ohm.

IMHO take the MTX back and get either the JL 500/1, granted it's twice the price of the MTX, or go on e-bay, pick up an old Phoenix Gold MS275 (75x2) run the subs at 1ohm bridged on one channel and be running around 500-600 watts of power but you get what you pay for (the 275 is stable at 1ohm). THD on the MTX is .25% which is pretty bad, the JL is .05% which is getting pretty good the MS275 has a THD of .005% (the lower this number is the better). This amp in 1994 went for around $1200 and you can get them for around $200-300 today. Again, just my opinion, but I have learned alot from a buddy at work on car audio and what is good and what to avoid, thus the reason I'm going with the old school amps with what I'm building. I've heard systems with MTX, and other newer brands, and for a 75 watt amp, the 275 will blow them out of the water.

 

I didn't say that he will or will not be able to have enough airspace for both, but that he should see how much he can get out of what he has and go from there. I personally have a backseat system so I can't say just how much airspace is available in the well from my own experiences. As far as the quality of that amp goes- sure the JL would be a much better amp and I would go with it as well- but not everyone is after the same thing. As long as price was a factor, there are far worse amps than that MTX. Just my opinion though.

 

How about this option. If I keep the same amp & same box, but switch to JL 8" subs. The 8" needs .79 air space (I got that) and the sub is rated at 150 Watts. If this is a viable option, I'll just offer the Tweeter dude an even swap 12" for 8", he'll be makin out on the deal & my son won't have to buy another amp (& I won't have to build another enclosure!).
Watta ya think?
Corky

 

Not for sure how good the JL 8" subs are. All these new amps are just a shadow of the old stuff that was out 12-13 years ago. Most of my info has come from the guy at work who competed nationally with IASCA the main reason I decided to go ahead with the old Phoenix amps.

 

did you break in the subs good or just pound away? i noticed that subs would pound harder after a nice break in period..

 

I don't believe there was a break in period - I am sure he went ***** to the wall! I always knew when he was in the neighborhood!
BTW 5678TA, I love the picture of the piston in your signature!
Corky

 

thanks Corky.. that was when my 383 seized up and threw 2 rods.. also bent all 4 valves in the 2 cylinders and the pushrods.. 3 other piston and rod assemblies were seized tight..

my avatar picture is my posi and spider gears after a bit of wheel hop..

 

amp way to small your'd need two in order to give those subs clean power.

 

New subs come in this saturday. I will see if they will make the swap of 12" for 8". If not, I will be figuring out how to get almost 6 cu ft of space out of the back of a gen 3 & where to bury a second amp. With the weight of all that MDF, I will need to upgrade the rear springs!
THanks for all your input - I'll let you know how it turns out.
Corky

 

hope i'm not tooo late!!! corky your 12's only need 1.25 cu ft in a sealed enclosure. its listed in your owners manual what you needed was a larger amp or a second of the same

12W3v3-2 - 1.250 ft³ 35.4 litres
so you need 2.5cu which is very doable

 

give them a little more airspace than the recomended. they always suggest a box thats a little smaller. if your amp isnt big enough and your son is cranking it it could be distorting it and ruining the subs

 

i agree but he doesn't need 6 cu ft lol

 

lool yes.. he can stick an 18" in a 6 cu. ft. box

 

Why has no one pointed to the most likely culprit, his sons use of the volume and bass controls. Those subs should work just fine in .8 cu ft they'll be a little peaky but not anything to terrible. Make sure your son knows not to crank the radio until it clips the amp. Just keep your 12's, I'de even keep the amp and just turn it down a bit. The box you made looks great it should work fine and keep your son happy for years to come.

 

^^ probably what the main problem is.. keep your bass boost set at 0 or lower also

 

Corky you have enough space for 4 12's in a 3rdgen. I had 4
L7's 12's and they sounded fine except for the window cracking, and then i had a baby so i bumped it down to 3L7 10's now thinking of 3 L7 8's. 2 kicker 1200.1 on each set of 12's.Anyway i have the same opinion change the amp, he must have played the he// out of those subs.

 

He may have very well played the hell out them - we could hear him coming 4 blocks away. All the info is a little confusing. I returned the subs tonight (I was a little busy replacing the K-member on the car - see suspension forum) & the store got the replacements in last Thurs & one of the sales guys sold them on Sat. I asked him to order 2 8" subs, but if the concensus is that the 12's should work with less gain, I'll call and change the order. When we first had the system running, it sounded great. Maybe I'll set the gain & unplug the remote switch.
Thanks again,
Corky

 

I really don't think you'll be too happy with 8's anyways. That's a big difference in size, and volumne compared to what he has now.

Just make sure you have that gain turned down. If you have it maxed out, and he's clipping the signal. that's most likely what killed them.

 

I changed the order back to the 12" subs. I'll put them back in and give my son a little education on operating the tunes - so next month he'll be replacing them again (bang head against wall).
Corky

 

Corky try lettin him turn the radio up as loud as he wants it and set the gains for volume of the radio. Ya know anything is worth a shot!

 

I've been thinking about this, and if he's clippnig the signal, I would be afraid of an amp that won't turn off if it starts clipping.

 

Klortho,
Is that some sort of protection an amp should have? And pardon my ignorance, but can you explain clipping? I am an old dog, but I still like to learn new tricks!
Thanks,
Corky

 

Straight from the wikipedia

The distored waveform drives the subs to the full range of motion and holds it for a moment which results in blown speakers. I know that my Phoenix Gold amp has a red light on it and when it starts clipping, it turns on and the amp shuts down to keep from blowing the speakers.

 

Most amps can be clipped ALOT before they overheat, especially class D amps. You can clip an amp just enough to melt a sub and the amp won't shut down. Also you can feed a clipped signal from the head unit to the amp, the amplifier won't be maxing out at that point but the signal it's getting basically does the same thing to the sub and burns stuff up.

 

Finally picked up new subs tonight. Store sold the last set they got in by accident & then we were getting the runaround. I put both subs back in the same enclosure & only hooked up one for now. He adjusted bass boost way down & played with the gain until tunes sounded good. Everything sounds pretty good & I will play with it this weekend. I will try to get gain & boost adjusted with both subs hooked up & see if the subs survive. In the meantime we are looking for a second amp.
Thanks to all for your expertise!
Corky

 

if you still blow subs get a good amp anymore the wattage dosen't realy matter my guess is that the amp you have is what we at my old sound system job called dirty power yeah it has a lot but it is not clean power usually sony and all the name brands list 1000+ power ratings you don't need that much power. only about 200- 400 depending on the subs. your box is perfect looks exactly like mine i bought from a manufacturer. my best suggestion is either planet audio amp or any of the memphis audio line they are what we call clean power with little to no distortion. we rarely get any coustormers that come back with bad comments about any of these lines. also dont crank all of the gains use about only half of the dial. I personally have all speaker and sub wise memphis line. my amp is a planet audio and i use a eclipse head unit. i do enter sound competitions every now and then and i haven't blown any thing yet. theses comps. push your equipment to the max. and even after a year still thump asa loud as ever.

if i knew how id show you my set up but i don't know how to place pics. any way just let this bit of info help from a person who did this for some extra pocket change.

( i hit 146 dbs with only 2 12in subs and my power from my amp is cut back ,airplaines purgeing there turbine engines before take off read a 132dbs.) yeah its that loud.