I just recently found out that my T400-4 has some major issues with crosstalk.

Using my ipad mini and 3.5mm to rca cable I confirmed major cross talk within the amp. With the mids connected to the rear channels of the amp I connected my ipad to the amp rear input and listened to how it sounded. I then connected to the front input(tweeter disconnected of course) and I should have head nothing, but it was almost as loud as when connected the the rear, but with a faint buzz in there as well. I decided to swap the mids to the front channels of the amp to see if it was happening that way as well and sure enough, same damn thing. Apparently my T400-4 is junk?

I talked with a local guy advertising on CL for amp repair and $25 for testing and flat $125 for repair has me wondering if it would be cost effective to fix it vs selling it cheap to someone that wants to mess with it and getting new amp(s) to properly power to my mids. The ad in question is http://phoenix.craigslist.org/evl/eld/4346888840.html

I am trying to run a set of ID X65 and XS28 in a 2-way active setup. I have been eyeing the arc foose amps and the zapco st-x and st-d lines if I were to change what I was running. My goals are to utilize my current drivers in the stock door locations to start with, have great clarity and impact, and a halfway decent stage. 2002 tahoe is what I'm working with interior wise.

I guess my main question is, to fix or not to fix? If I don't end up repairing my current amp am I looking at some good clean amps without breaking the bank? Any input is welcomed.

Edited March 18, 201411 yr by hdrox88

I vote fix

Love my t8004ab

Get rid of... Best time to upgrade is when something breaks... Look at zed?

Get rid of... Best time to upgrade is when something breaks... Look at zed?

I too, typically run by this philosophy. The Draconia looks very nice, just don't want to push the tweeters too far. I know you can adjust gains to suit, but being my first active install, I am slightly nervous about tweeters. They seem so fragile, haha.

Are you running it in four channel mode? These amps have major crosstalk issues when put into four channel mode, even new. Your best bet is to put it into 2 channel mode and it should kill the noise.

Are you running it in four channel mode? These amps have major crosstalk issues when put into four channel mode, even new. Your best bet is to put it into 2 channel mode and it should kill the noise.

His original thread, he did test it. Just lowered a bit

I was trying to use it for a two way active setup, so 2ch mode would be no good for me. Is that true of all rockford amps? Sounds pretty shifty to me for their top line of amps to have that kind of issue. One thing I didn't check is L to R cross talk, that would not be fixed by a 2ch switch and would not be very good for the clarity of the sound either.

Yeah it's pretty common on the 400-4 and some of the lower line 4 channels for some reason in some cars.

Well that blows, where was RF r&d on that one? Kinda turns me off to them altogether now. I always wondered why something just never sounded right in the years I've run this amp. I just chalked it up to poor install procedure, now I know why. Of course install is still important.

Honestly you can blow equipment on very little power.. Install and settings can/will affect how a speaker reacts to the power applied, top that with the fact that all music is dynamic... AND you're fckd!!! Lol...

Edited March 19, 201411 yr by Shogen

I've read lots of stuff today and lots of controversy on blowing stuff up. Power kills speakers, not clipping. Low power can kill just as easy if set up improperly. Clipping kills things way before power will, etc, etc, etc.

What I'm taking away from it all is that power isn't so much a factor as install and setup. Of course doubling something's rated power isn't a great idea if it is expected to last.

I've read lots of stuff today and lots of controversy on blowing stuff up. Power kills speakers, not clipping. Low power can kill just as easy if set up improperly. Clipping kills things way before power will, etc, etc, etc.

What I'm taking away from it all is that power isn't so much a factor as install and setup. Of course doubling something's rated power isn't a great idea if it is expected to last.

 

Why not?  Depending on the person controlling the volume knob it could last longer.  I've been running the 3" full range drivers in my Jimmy on about 4x their rated power with no issues.  The 4x6's I just put in my Olds are on more than 3x their rated power and I expect them to last plenty of time.  Hell, Brad (Impious) ran/is running his Bravox CS603CF's on around 4x their rated power and they have done great.  The point is that if you know how to listen for stress from the drivers and setup crossovers and EQ's correctly there's not a single good reason that running more than rated power would cause a problem.  On that note there's all kinds of good reasons that running 2x or more rated power and the headroom it gives you can be a VERY good thing.

My virgin ears need some training. Lol just trying to get a good start I suppose. I don't want anymore failed equipment!

My virgin ears need some training. Lol just trying to get a good start I suppose. I don't want anymore failed equipment!

 

lol, no one wants failed equipment, ever.  Don't get me wrong either I'm still training my ears for everything associated from stress in the drivers to what ill effects the installation itself or the settings I've set in the signal chain are doing to what I hear so it could still very well happen to me.  My point was really that it's not black and white, running more than rated power isn't necessarily be the direct cause for the drivers failure.  

 

I discovered completely on accident many years ago the benefits from running more than rated power to a speaker.   Right out of high school I ran a cheap pair of Audiovox 6x9 3 ways rated for 40wrms on a Profile California A600XL which was rated 150wrms x 2 because at the time I wasn't aware of the insignificance of MAX power ratings.  The power ratings matched up and I thought it was good to go and in fact that little setup impressed a lot of people at how clear and distortion free it was for what it was and it wasn't until years later I discovered what I had done.  I ran them in that setup for several years without ever having any issues and when I would hear a little distortion, or something not sound right I would just turn it back down a notch or two until it sounded right again and went on.  That was why they worked so good for so long and really all it takes to use speakers in a similarly overpowered way.

I've read lots of stuff today and lots of controversy on blowing stuff up. Power kills speakers, not clipping. Low power can kill just as easy if set up improperly. Clipping kills things way before power will, etc, etc, etc.

What I'm taking away from it all is that power isn't so much a factor as install and setup. Of course doubling something's rated power isn't a great idea if it is expected to last.

Just to make things easy on you....power is the ONLY thing that kills speakers. It is literally impossible to damage a speaker without overpowering it (outside of physical damage). There is no such thing as "low power can kill speakers" and clipping does not "kill a speaker before power will" because POWER is what killed the driver. The rated power of the amplifier may be less than the rated power of the speaker, but if you blow the driver you overpowered it....plain and simple, no two ways about it. Clipping will only damage a speaker if the resulting increase in power exceeds the drivers thermal or mechanical limits. Clipping might be the cause of the overpowering by increasing average power over time.....but the fact remains that TOO MUCH POWER was the factor that killed the driver.

I've read lots of stuff today and lots of controversy on blowing stuff up. Power kills speakers, not clipping. Low power can kill just as easy if set up improperly. Clipping kills things way before power will, etc, etc, etc.

What I'm taking away from it all is that power isn't so much a factor as install and setup. Of course doubling something's rated power isn't a great idea if it is expected to last.

Nope. The ONLY thing that can kill a speaker is too much power. Peak and you have over excursion damage and average power and you have thermal problems. Nothing else will do it besides physically destroying them by manual means.

Next time I read page 2 before posting.

Thanks for all the insight guys, definitely learned a thing or three in the past few days. Something I was curious about that I have yet to see anyone else mention or question has to do with setting amp gains. Everyone always says to set the hu to 75% volume and set gains from there by ear. My question is, if you are using your ear to set the gain, could you not use your ear to find the sweet spot on the hu volume first with gain zeroed? Then you have the potential for a lower noise floor by getting the most out of the hu before adjusting the input sensitivity? That's actually how I set mine up in the past and never broke anything.

Thanks for all the insight guys, definitely learned a thing or three in the past few days. Something I was curious about that I have yet to see anyone else mention or question has to do with setting amp gains. Everyone always says to set the hu to 75% volume and set gains from there by ear. My question is, if you are using your ear to set the gain, could you not use your ear to find the sweet spot on the hu volume first with gain zeroed? Then you have the potential for a lower noise floor by getting the most out of the hu before adjusting the input sensitivity? That's actually how I set mine up in the past and never broke anything.

 

the hu signal could be clean all the way up to 100% but thats not the reason why you set the gain with the hu at 75%.  say you have a song that is recorded at a lower reference level. if you set the gain with the hu at 100% then that song would always be quieter relative to other tracks. but if the gain is set with the hu at a lower volume (755%) you can turn the hu up past that point so the song is as loud as everything else. 75% is pretty pretty arbitrary, you could pick 50%, set the gains accordingly, and you wouldn't hear a difference. 

as to your question. your method is fine but doesn't result in any differences. unless the hu output get dirty before hitting 75%, in which case you would pick a lower volume level. you won't gain any magic db's or anything like that... 

I understand what you are saying. I wasn't necessarily concerned about more db output, I was curious if there was any benefit to the noise floor by using a higher hu volume if available. After thinking about it while writing this, the result is probably negligible until you switch to a much higher voltage signal via a different hu or processor, etc. Am I correct in my thinking? Just trying to be sure, not make assumptions.

Your initial assumption was correct. For optimal (i.e. minimum) noise you want the "gain" in the system as early as possible. So you want the maximum "gain" to be at the head unit, which means ideally setting the system gains with the volume at a high setting. However as lithium pointed out, you want to leave some headroom in the volume range to account for recording levels.....which is where the arbitrary 75% HU volume setting comes from.

After sleeping on it and reading again, it makes sense. Thanks again all who replied, there is definitely a wealth of knowledge on this forum.

If you want to get rid of that amp for cheap I might he interested