not a live sound question but i figured you guys canhelp it'sabout caraudio
Home > Home Recording Forum > Live Sound Reinforcement > not a live sound question but i figured you guys canhelp it'sabout caraudio
Posted on Mar 09, 2009 02:48 pm
acalasiasound
Member Since: Feb 05, 2009
So my buddy came to me with this question so I tried my best to explain on what I thought was happening and wanted to check to see if anyone else has any thoughts. He got a new car and has a 1200 watt amp with 2 twelves all pre wired so I'm assuming that this is all wired correctly. The problem is for some reason he has spliced the signal being sent to his rear speakers for the signal to be sent to his amp. Now I know this is wrong in the first place since the line is post amp...I'm surprised that amp still works. He was wondering why when he turns up the volume why the bass doesn't get louder. My explanation was the resistance to the speakers opposed to the amp was lower thus sending more of a signal to the speakers. Now since with we're dealing with resistance as he turns the volume lets say at a normal volume 50% of the signal is being sent to the speakers and 50% is being sent to the subs amp. As he turns it up since the resistance is different i'm guessing the ration changes more to 80% to the speakers and 20% to the sub's amp. That's at least what I explained to him as why the subs don't get louder as he turned up. Now he wants to know how to fix it, so I explained he needs to find a way to get a line signal from his deck. He doesn't want to get a new deck so My question is Is there a way for him to get a line signal from his deck or do you think it's easier to just get a JVC or Alpine deck that have line outs already or even Sub outs, or find a way to get a signal off the line out before it goes to the amp in the head unit. His deck is a stock one that comes in a Mercury Mountaineer and the reason he wants to keep it is because it has a 6 disc changer!
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Mar 09, 2009 04:09 pm Wow! I had to read this several time figure out what was going on here.
Form what I can deduce here. You have a signal that is sliced off of the amp, going to the input of another amp. Correct?
If this is the case, then you have found your problem.
You can not take an amplified signal, and run it to an input.
Your finding out the reason why. The input of an amp is looking to see a signal that is referred to as line level. That means that it will be a signal that gets no stronger then 1.23v. Or, what we call +4 dB.
When you send a signal that is stronger then 1.23v, you get what is known as a square wave. A square wave is a clipped signal. That means that you have exceeded the limit of what the preamp can handle. So, the preamp takes the level of voltage as high as it can go. The input voltage continues to rise. The preamp can no longer match the in coming signal, so it flattens out. Making the wave look like a square.
When a square wave is present. There is no way an amp can see the bass. Since all of the bass waves are now a square. And, this is doing a lot of damage to his amp, and speaker.
Why? Well, the square wave tells an amp to go to full power. Hold that power, then let it go. And the speaker, is moving all the way out. Staying there. And then moves back. All of this creates just tons of heat. The heat will eventually destroy all of his gear.
Now think of how a bass wave looks. Large rolling waves right? So, if the speaker is being held out by the amp, there is now way you can hear the bass. The time that is needed for low end, has gone by. While the amp is holding out the speaker.
The louder you try to make the bass, the bigger the square wave, the less bass will be produced.
He needs a radio that has a Aux out. That is what goes to the sub amp. And that will give you nice strong bass.
Mar 10, 2009 12:50 pm The key words I saw were "Mercury Mountaineer". I used to own a '95 Ford Explorer (twin of the Mountaineer), and it had a separate 6" woofer (with it's own amp) in the rear area (passenger side, behind the last seat row). It was a stock system, I think by JBL. I suspect the signal you are tapping (that runs to the back door speakers) has already had all the low freq's stripped off, and his subs are not getting anything they can reproduce. I agree with the other gentleman's comments about feeding the amp speaker-level signals. That is not good, unless the amp is designed to take speaker-level signals (a lot of car audio amps are).
Have your friend take apart the interior trim near the stock woofer, and trace the wires back to the stock woofer amp (I can't remember if it's on the same side as the woofer). He might be able to tap into the line-level signals there. If his amp can accept speaker-level inputs, you can tap in after the stock amp. Either way, you'll at least have a signal that contains the bass frequencies.
I would also recommend testing the new amp/woofer with a known signal (IPOD's can put out close to a line-level signal, but if you had a portable CD player, you might get better lows out of it). If he did indeed hook a line-level input to the speaker outputs, he could have blown the amp.
Lastly, make sure the sub amp has good power and ground connections. We're talking at least 10 gauge wire in both the red and black lead. You might want to hook up a voltmeter or test light while the amp is cranking to make sure that's all good.
Mar 10, 2009 06:56 pm Alright thanks guys sorry the question was weird. My buddy just asked me about what he was doing and if it was right and if I could find another line level source without him getting a whole new head unit. If it was me I would have just gotten a whole deck instead of cutting into an amplified source, but I should be able to help him. Thank you jim i'll definitely check to see if he has a line level source anywhere in his car that would save a lot of trouble!
monmixrIf 50hz 60 will kill ya.Member
Since: Jan 08, 2009
Mar 10, 2009 10:14 pm Crap, so your saying I cant take the output from an 8001 and run it into the input of another 8001 to get more power??? now I have to rewire everything!!
Mar 11, 2009 12:04 am Uh... If you have two 8001's in a rack.... I'd ask you to replace it. Or, at least give me a crane to move it.
My back still hurts from the last time I moved a amp rack that had 2 8001's and a 9001.
Ouchy!
monmixrIf 50hz 60 will kill ya.Member
Since: Jan 08, 2009
Mar 12, 2009 04:13 am MT-4 baby! I have several tons of 8001s lol
monmixrIf 50hz 60 will kill ya.Member
Since: Jan 08, 2009
Mar 12, 2009 04:21 pm Actually, thats not true, I thought about it today, and I have 1 and 1/4 tons of 8001s
Mar 12, 2009 04:29 pm Oh, so half of a standard amp rack.
Noize2uCzar of MidiAdministrator
Since: Apr 04, 2002
Mar 12, 2009 07:49 pm Crest Audio??
monmixrIf 50hz 60 will kill ya.Member
Since: Jan 08, 2009
Mar 12, 2009 08:35 pm Yup, crest audio. MT-4 uses a rack of 3 8001s per block. LOL yea Rob, half a standard rack, and although that is funny, DB at one time used a 6 pac rack. (6 blocks of MT-4 power in one aluminum rack) thats 18 8001s in one rack, fed by feeder. That was not funny.....
Mar 12, 2009 09:04 pm Oh, come on Noize. Crest Audio was huge in the 80's.
Just about every Meyer rig that was non-self powered, was ran by Crest amps.
And the Crest X8, and X4 were the club standard mixing console. Still see a lot of them still working as well.
In the 90's. Crest was bought out by Peavey. And Peavey has destroyed Crest Audio. Even to the point of dropping the console side of the company.
All of the electrical engineers have left to form APB DynaSonics. And now they copy the analogue boards that they use to make back in the day.
Which isn't all that bad. Before Peavey bought them, they were copying a lot of ATI stuff. Such as the Paragon 1. On the Crest VX, there are no capacitors in line with the output audio path. Not to shabby of a design either.
They just never made it to the top line up with there consoles. But just about every live sound company has or had one in their inventory.
Mar 12, 2009 09:10 pm OH DEAR GOD MONMIXR!!!!! 18! Freaking 18!
What kind of casters had to be on that rack?
Or, did you just leave it in the truck and run all of the wires from there?
18.... I just can't imagine how heavy that was.
Mar 12, 2009 10:12 pm WOW! I just looked it up. And Monmixr, you weren't lying. 1530 lb's, and that is not counting the weight of the rack itself.
Man... I thought I had it bad when we had a giant rack of Crown 3600's. I think that we had about 10 in this one rack. We use to call it the refrigerator.
And we had to change the casters on it, at least once every three months.
Here you go Noize. I found the pdf for the 8001.
www.fmsystems.net/pdf/cutsheet/8001.pdf
monmixrIf 50hz 60 will kill ya.Member
Since: Jan 08, 2009
Mar 13, 2009 07:08 pm Ive looked all over for a pic of the 6 pack rack and cant find one, but Im sure someone has one. As soon as I can find one Ill post it.
Noize2uCzar of MidiAdministrator
Since: Apr 04, 2002
Mar 13, 2009 09:04 pm Rob, Crest was powering my first owned rig in the cities here. Before clubs had their own FOH gear you either rented or owned your own. It was easier to keep our own gear instead of counting on the likes of Eclipse concert systems to get it there on time and in good shape. There just were not any good outfits that you could count on in the late 70's and early 80's.
I was looking for some old pic's from the playing days but not having any luck. Somewhere there are some from one of the bigger clubs that was down were I live now back in the day it was the biggest stage in a club in the state. Doc Holidays was what it was called.
But ya, I remember that crap being extremely heavy indeed.
monmixrIf 50hz 60 will kill ya.Member
Since: Jan 08, 2009
Mar 13, 2009 09:31 pm I dont think Id call the pro series crest amps crap. Heavy yes, but the fact that you can still buy 8001s, 9001s and 10001s 20 years after they hit the market I think is a testimony to their reliability. I still use MT-4 and still use 8001s. I use nexo too, but for an outdoor fest or rave, MT-4 walks all over nexo.
Noize2uCzar of MidiAdministrator
Since: Apr 04, 2002
Mar 13, 2009 09:56 pm Oh no, I don't mean they crap. Just the rig's themselves being heavy made them crap. In those days you couldn't get good help around here that would stay sober long enough to move any gear.
And indeed they are good. I wish I still had just one 8001 to power the large format speakers in here now. I keep switching between a Peavey and a couple different Crown units. I need an Iso cab to run the Crowns though as they are louder then **** with the fans all running. That was the only reason I bought the Peavey for the quietness and higher power.
monmixrIf 50hz 60 will kill ya.Member
Since: Jan 08, 2009
Mar 13, 2009 10:52 pm Yea, crowns are a little loud for the studio...
Noize2uCzar of MidiAdministrator
Since: Apr 04, 2002
Mar 14, 2009 06:01 pm I only use them for playing live synth stuff in here. I have a thing about having to feel the sound. So the need for a bigger amp and speaker set up. If I could find something better then the Peavey though that had as quiet a fan set up I would run it. I need something with about 900 minimum.
monmixrIf 50hz 60 will kill ya.Member
Since: Jan 08, 2009
Mar 14, 2009 06:42 pm Or replace the fans with quiet daytons.
Noize2uCzar of MidiAdministrator
Since: Apr 04, 2002
Mar 14, 2009 09:17 pm Ya now, I never even thought about tearing into it to replace the fans. Funny, I'll rip into the PC first time it even skips a beat or makes a whisper. But the amp I never even thought about that. I've got em swapped out of the rack now so I'll be opening them both up for surgery. Then off the Peavey as I like the Crown's better.
Sometimes we can't see the forest for the tree's.
I owe ya one.
Mar 14, 2009 11:36 pm Hee. Sometimes we can't hear the music above the fan noise. =P
That was my chief complaint when doing monitors for a quite show with Crown amps.
We had the board over the amp racks, and you couldn't hear a word that was said on stage.
That is why I like the QSC's. But the heat you get from a QSC. I feel like an chicken being slowly roasted.
Noize2uCzar of MidiAdministrator
Since: Apr 04, 2002
Mar 15, 2009 05:09 pm Ya, tried a QSC without knowing exactly how hot they got. It went back after running it 2 days and raising the temp in here about 15 degree's. Don't need that. The Peavey isn't bad for heat. I simply like the sound of the Crown better.
I can't imagine sitting over a rack or two of those QSC's though.
Mar 15, 2009 05:34 pm Great for cool weather days. Sucks for outdoor shows during the summer.
And the new 3602's seem to be really bright in their sound. Almost to the point of being brittle.
So, I'm with ya on the sound of the Crest and Crown amps. Can't beat the sound. Certainly could due without the weight.
Noize2uCzar of MidiAdministrator
Since: Apr 04, 2002
Mar 15, 2009 08:08 pm Ya, my youngest hates helping me change em out. They are not light by any means.
