Car Domain...

Discussion in 'Off Topic [BG]' started by Dave, Jul 11, 2005.

  1. Ok heres a little background info.

    I got a MTX power amp from them 340 watts at 4 ohms. Hooked up to my subs in my car, and the thing over heats like crazy. I double check everything and made sure it is hooked up right, it was. My subs are rated at 300 watts at 8 ohms each ( 2 tens) so the amp was puttin out 340 watts. I call Cardomain and they say they'll email me a shipping label, so thats cool.

    I get the email today and they say they cant take it back because they say I misused the amp driving those speakers.

    Am I correct in my thinking that I did not harm the amp at all by hooking it up to these subs.

    Keep in mind that used to drive these same subs with a really cheap Bazooka amp that only did 150 at 4 ohms and never had any issues save for it wasnt very loud.

    Just wanted to rant/see if anyone can verify that I didnt do anything wrong.


  2. BTW, heres the email

    Greetings from

    Thanks for contacting us about your order. According to the discussion over the weekend, you said you were running two 300w subwoofers off this amplifier—this is well beyond the designed specifications for this amplifier. It’s not designed for such a load and so it’s overheating is not a defect or flaw in the product. Such overuse may actually damage the product and per our return policy we do not accept “Products that have been modified or damaged due to incorrect installation or misuse.”

    Please do not hesitate to contact us should you need additional information.
  3. Trevorus


    Oct 18, 2002
    Urbana, IL
    You may want to ask them if it is improper to run speakers that can handle more power than the amp can give out. It is obvious that running too small of a load on an amp will make it overheat, but you were not creating this condition. How exactly did you have everything hooked up?
  4. I had everything hooked up exactly like my old power amp was, I basically just switched one out for the other (Yes, I had the correct guage power cable running to the new amp). The old one was installed by Best Buy and never had any issues. The speakers are set up for a 4 ohm load, had the power cable, ground, remote turn on, and RCA cables hooked up in the respective plugs.

    Nothing was disconnnected from the CD player or from the subs. I did have to disconnect the batterey while installing, for obvious reasons, but Im quite fluent in this kind of stuff so I know I didnt hook it up wrong.

    On the phone the guy was teling me that I should not have gotten a two channel amp and bridged it, that I should have gotten a mono sub amp. Why do that when the mono sub amps are more expensive?

    When running a bass amp we dont worry about speakers trying to draw too much out of a power amp (which is basically what the guy was telling me I was doing), so why does the guy think its different for car subs.
  5. Trevorus


    Oct 18, 2002
    Urbana, IL
    That may be the problem. Don't bridge it. Set it up to run one 8 ohm speaker per channel. That should solve the problem.
  6. Because the mono sub amp won't melt down under a 4 ohm load. Is your new amp a stereo amp rated at 340W @ 4 ohms per channel?

    If you bridge that, it will only handle an 8 ohm load. Running with a 4 ohm load puts each channel at a 2 ohm load. If that's what happened, he's got a point, you definitely could have damaged the amp, at least overheating is a near certainty, if it still works, but gets hot quickly, you probably didn't destroy it yet, in case they don't want to take it back.

    Regarding the original post, the amp only sees the ohm load. The amp is unaware what the power handling capability of the speakers is, and doesn't care. If you really have a 340W amp capable of driving a 4 ohm load, your 2 10's fit the bill perfectly.

    The second post about bridging the amp would put you in the wrong, if each amp channel can only handle a 4 ohm load.

  7. Then it only puts out like 60 watts or something ridiculous like that.

    I checked the manuel and depending on the voltage given it puts out either 240 or 340 watts, at 12.2 V or 14.4 V, respectively.

    The amp is designed to be bridged for a mono load, so I dont think that affects it that much.
  8. Yeah the amp is rated at 340 watts at 4 ohms bridged.

    Heres a link to it.

    MTX Power Amp
  9. Well, its clearly rated for bridged operation with 4 ohm loads, and thats precisely what 2 8 ohm spkrs in parallel provide. They are absolutely completely full of crap to claim abuse and deny the warranty. You may quote me on that.

    Email them that link and tell them to explain to you again REALLY SLOW why its considered abuse to use the amp for what its rated for.

    By the way, if he's claiming using 2 300W speakers somhow attempts to suck a total of 600W out of your amp, he's either a liar or an idiot. You need to see his supervisor in either case.

    Here's a link to the manuf web site, listing that amp as producing 170W@2 ohms per channel, which also equals 340W bridged into 4 ohms.

    mtx news re new MTX amp specs

    Just in case they try to weasel out and say their web site info was mistaken. Even if it was, they ought to be responsible if they recommend doing something that would have fried the amp. In this case, its clearly correct though.

  10. Yes, thank you very much.

    I sent them an email saying that except I explained the whole concept in lots of detail.

    Im glad Im not going mad and being upset at these idiots for no reason.
  11. I'll be generous and assume the guy that sent you that email is new on the job and un/misinformed.

  12. I really hope so, I dont want to lose my 150 bucks, it going to help me pay for a Eden WT550 when I get the money back.
  13. I recieved another email. Is this guy just full of crap or am I just uninformed about how speaker and power amps interact?

    Greetings from

    Thanks for writing to us with your question.

    I was the representative you talked with over the weekend and I was in error in setting up a return for this product.

    While speakers can and will function at lower wattage, subwoofers do have a minimum level of wattage and will try and draw that amount from the amplifier and if the amplifier cannot meet that power requirement, it will cause the product to work harder than it's designed to.

    You mentioned over the weekend you were running two subwoofers off this amplifier-- what brand of subwoofer were they? I believe the subwoofers you told me are rated at 300w a piece, which is 600w total. As this amplifier can only handle (at best) 340w, you've seriously overtaxed this amplifier.

    If you wish to discuss this further, I invite you to discuss it with my supervisor. His name is Shuyler-- call us directly at 1-800-597-9776 and ask for him and provide your order id# of EJV050704X as reference.


    Joe Z
    CarDomain Customer Care
  14. What a doofus... he IS thinking the 600w capacity of the speakers is somehow attempting to suck excess power out of the amp!

    Jeebus... customer service is pretty much guaranteed to suck there, eh?

    The ohm rating of the speakers is all that matters. 2 8 ohms = 4 ohm load. The speakers are capable of getting louder if you had 600W available to drive them. But the only problem of lower power available is less volume. If you're clipping the amp, there's potential for probs, overheating, etc, but no point bringing that up, they're pulling stuff out of their butts now, no sense giving them a plausible excuse for a lifeline.

    Try the supervisor.


    This is electronics 101 stuff, not rocket science. 3 1/2 years of electrical engineering at University of Michigan is way more than I need to cover this concept.

    Try writing an email to mtx directly if the supervisor tries to shaft you. They should put pressure on them, correct their misconception if they refuse to take your word for basic electronics.
  15. subwoofers are just speakers, what mystical properties do subwoofers possess that "normal" speakers have that tricks amplifiers into putting out more power? That's ludicrous. The power amp is a voltage amplifier with low output impedance. rated to produce up to about 36.8V output at the rated distortion. 36.8V squared / 4 ohms=340W of power. The power from the amp depends on the input signal and the impedance. The RMS power rating of the speakers is irrelevant. How does the power amp even KNOW what the power rating of the speakers is? It can't! It only sees how many ohms it has to drive. It doesn't know if you put a 50 watt speaker or a 5000 watt speaker. It only cares if you use 2 8 ohms (total 4 ohm load) or 2 4 ohm spkrs (total 2 ohm load= BAD). If you're sure they're 8 ohm spkrs, you're in the clear.

    Again, total crap. Using 600 W of speakers with a 340 W amp means you probably aren't going to melt the voicecoils down from too much power no matter what you do. And you can't get the speakers to their maximum loudness. As you said, you've been running them off a 150W amp up to now, with no meltdowns of the amp.

    If both speakers are moving, (i.e. not damaged), and both are 8 ohms, there is nothing wrong with the setup you have.

    If they are claiming that their 340W@ 4 ohm amplifier cannot actually drive 4 ohm loads without breaking down and overheating, even though its clearly labelled as such on their and the manufacturers website, they owe you a refund, and maybe they can recommend another amp that is NOT intentionally overrated and misrepresented.

  16. Here's the definitive answer from the MTX website recommending subs/amps compatibility regarding power ratings.

    mtx website for recommended amp power for given spkr power rating

    Clearly states that their 300W woofer should be powered by a 150- 300W amplifier. I'm going to venture a guess that means it would be ok to power a 600W pair of woofers with a 300W - 600W amplifier. Since 340W is within 300-600W, the MTX website CLEARLY shows that you have an appropriately rated subwoofer for the amplifier you bought. The MTX website recommends anywhere from half the spkr rated power to the same RMS rating as the speakers. Throw that link in his face, he's going to be a little embarrassed.

    End of discussion.
  17. Yeah this guy is a true idiot. Just got off the phone leaving his supervisor a message saying that this is basic electronics and there is no way I have harmed the amp and would like a refund.

    Tis truely sad who theyll hire these days...
  18. Absolutely positive, they are dual 4 ohm voice coil speakers, allowing either a 2 ohm or 8 ohm config for each speaker. I have them wired for 8 ohms each = 4 ohms total.
  19. See what the supervisor says.

    Only thing that cheeses me off more than incompetent people like that is the though that they know better and are trying to pull the wool over your eyes because they think they can get away with it. 90% of the time they can, people aren't usually aware of electronic things. Like mechanics taking advantage of women for car repairs. How many others have they screwed with these misconceptions, who accepted their fate cause they took their word for this crap?