audiobahn amp, subwoofer, dead?

Well I have an older audiobahn subwoofer aw1005 (10" DVC, 2ohms each coil) paired with a A8002v 2 channel amp. The woofer is supposed to be 900 watts rms and the amp bridged into 1 channel is rated 800watts rms. I wired the bridged amp (rated 4 ohms) in series to the subwoofer (two 2ohm coils in series = 4ohm i think?) and all sounded well for about a week.

I suppose I was a victim to the overhype (car audio stuff is very new to me) by going with audiobahn (this conclusion coming from search = audiobahn), but I have already invested in it so now I just want it to work. I don't care about competition stuff etc, and I mostly just want some decent bass to back up the rock I listen too.

But anyway, I wired everything as previously mentioned, and it sounded great (to me) for about a week. Then one day I noticed it cutting in and out a little and now it's not working at all. The sub isn't moving at all, but the amp appears to be getting juice (built in meter thing has a read out), the protect light isn't on, and all the connects (rca wires from deck, speaker wires) seem secure. I'm clueless as to what is causing the problem, and all of the local shops seem like idiots. (I had a guy at one tell me "the wiring didn't matter as it would all sound the same" when I asked him how I should wire the sub). I bought a multimeter with hopes of testing different parts of the wiring to see just what is not getting a signal but have no idea how to use it :( (It is a greenlee dm-40 that I grabbed from Lowes and while I understand basic concept of multimeter, applying that concept to troubleshooting amp isn't working too well for me!) I haven't been able to find a good guide on web either :-(

Also, I am wondering if the box size could be causing a problem. The box is really big for a single 10 (like over 2 cu. ft.), and I am curious how a more appropriate box could help (the car being a 93 honda civic coupe).

Any and all help / guideance is much appreciated.

IMO the sub might well have gone into over excursion in that large enclosure.  You should pull the sub out and manually push on the cone and let the forum know if it moves without noise or other trouble.  You also have to troubleshoot the amplifier because at this point you don't know whether it's the subwoofer or the amp that is acting up.  Borrow another sub, in box, and connect it to your amp for testing.  The DMM isn't going to help you at this point.

I hope that it is the subwoofer that's broke and you at least have an amplifier to work with while selecting a new sub / box combination.  That sub is worth less than the amp and is difficult to model decent sound output with any type of box alignment.

You can also put the meter on "ohm" on the lowest setting and tell us how many ohms it reads. It could even be that one of the wires inside of the box came undone. I had a woofer a long time ago where the wire from the sub's terminals to the voice coil came undone. It could be that the voice coil overheated and melted. Sometimes when this happen because the load gets gradually lower it will overheat the output transisters in the amp just enough to fry them but it doesn't end up setting off the thermal overload protetion in the amplifier.

Anyways, if you hear any distortion at all turn the subs down. At that point something is going seriously wrong. Your amp could be clipping which puts out a lot of power but isn't moving the subwoofer anymore and can overheat the voice coil. The sub could also be reaching the limits of it's syspension. I have a 1211a infinity amp that puts out around 1,000 watts rms to subs that are rated to handle 150 watts rms. I have had these subs for 13 years now used on and off with amps that put out much more power than they are rated for.

Ok, I finally had time to look at this some more. I pushed on the speaker and it seemed to go up and down with no problems at all. There wasn't any grinding noises or anything like that.

I also tried to use the DMM to check the resistance on the woofer, but I'm not sure I did this correctly considering I don't know how to use a MM.  The lowest settng for ohms (funny horseshoe symbol) on my meter was 200 (others being 2000, 20k, 200k, 20m) and put each of the leads on the speak wires that go to the amp. My reasoning was that this would measure the resistance the amp gets which should be the resistance through the series, roughly (hopefully) 4 ohms. However when I put the leads to the wires (I disconnected them first), the number just sorta jumped around like crazy. Again that is probably from me doing it wrong. I did use the continuity feature on the same wires and it beeped leading me to believe that the wires are good.

There has never been any distortion in the sound at all. It has always been either it worked or it didn't.  Is there a way for me to use the DMM to make sure the amp is sending out a signal and that the rcas are sending out a signal? Which setting would need to be used for that?

Unfortunately, I don't know anyone who I can borrow another sub to test. As for testing the sub itself, is there any other way I can do that?

I am probably going to get the materials to build a new box soon. Assuming the subwoofer is bad, does anyone have a recommendation for a new 10-12" woofer for this amp (800 watts rms)?

Again, all and any help is much appreciated.

xtremej wrote:

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And you may want to use the woofer wiring guide to the right as you either had it wired to 2ohm or 8 ohm. If wired to 2 ohm then your amp may be cashed in.

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I'm pretty sure two 2 ohm coils wired together in a series is a 4 ohm load? Atleast according to: https://www.the12volt.com/caraudio/woofer_configurations.asp?Q=1&I=22 it is.

However, thanks for the recommendation. I am going to check it out. I also wonder, since it is a two channel amp, would it sound better (be cheaper) if I got two lower power speakers? Again price is my primary concern with SQ being my second.

xtremej wrote:

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If you had a 27 volt system you could hit numbers as audiobahn is advertising?

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Yes?

That actually makes a lot of sense because the built in meter thing in the amp is constantly reading 13.x.

Also as an update. I have been driving around the past week with the fuse out of the block between amp / battery. I feared that if it was the big box or something screwing stuff up, it would be better to leave the power off and salvage what I can. I was planning on taking my car to a local sound shop today so I put the fuse back in the block thing and turned down the gain and LPF on the amp. To my surpise the dam thing is magically working again. I went there anyway and the guy said my box should be ok. I turned it up a little, and it sounds good now. I am thinking that I possibly had the setting too high on the amp.

You have to consider the efficiency of the amplifier as well.  An amp will always pull more power than it will output;  the heat you feel coming off an amplifier is a necessary waste of some of that input power.  Depending on the class of amp, there is an average efficiency that you can assume.  Does it feel very warm to hot in operation?  Probably 50 - 55% efficient, or thereabouts.  Or does it feel slightly warm to cool to the touch?  Most likely 80 -90% efficient.

Here's an alternative formula to use.  The object with this is to find out how much power an amplifier uses in order to produce results:

e = efficiency of amplifier
total RMS = watts demanded from source

(RMS X 2) / (e X 2) = total RMS

Then use Ohm's Law I = P/E to find demand in amperes.

In using this efficiency formula, you have to be fairly certain of the true RMS output of the amplifier at the impedance load it is working with.  But as many of the common amplifiers on the market now are suspect in their ratings, output can't be determined with formulas or counting up fuses.  The output has to be directly measured in a controlled test.

The fuses' total rating can be a general guide for the more experienced installers / users, as xtremej was speaking of.  They will consider build quality, brand stability and all that comes into play due to having experience with the various brands and models.  Shady manufacturers can put any fuses they want to in an amplifier whether the amp is truly capable of producing results with that amount of current or not.  And I've seen at least one time when it was apparent that the assembly line put in the wrong fuse rating in a production run.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Ahh gotcha. Well is runs pretty hot so I would definately guess its not very efficient. Although my trunk isn't exactly climate controlled either. In other news, the amp wasn't working again this morning, but was working this afternoon. I have heard of amps over heating but it seems like mine is underheating (lol). The only time it is going dead is when it is real cool.

I am guessing this is probably related to the thermal properties of metal + cheap design. Perhaps getting too hot caused the metal to expand and push out other components so that when it cools they no longer touch? Or maybe this just happened at its operating temps due to cheap design. Its hard to say, but I'm probably going to try and contact audiobahn in hopes of an RMA. Actually now that I think of it, I may just contact the vendor and see about a refund.

If no one has a suggestion to fix this, does anyone have a suggestion for new brand / model of amp? Audiobahn has the speaker rated at 900watts rms. Assuming this is overated aswell, what would be a good way to get an accurate number?

Also, thanks a ton for input and help. This website and forum are incredibly informative.

Well I finally had time to take my car to a local shop. After running a DMM and a toner tester (where can I get one of those?), the guy discovered my rcas were bad. We pulled the rcas and sure enough there was a pinch in the wire. I let him re run a new wire (17ft rca cable cost 18$ ? pretty sure I got ripped) and it works fine now.

So after all that trouble, imagine that.