Stereo Questions....HELP

[hobertgracie]

OK....about a year ago I had a custom stereo put in - new deck, 12inch subwoofer in the passenger floor board, 2 - 6 1/2 in the doors, 1- 5 1/4 in the center and a amp put in the trunk.

Here is the deal....it sounds great, bass, loud....but something I have never understood that the installers could never explain or resolve for me is what I need some input on. When the volume gets above 22 (tops out @ 35) the volume gets lower and then it overloads or something if the song gets too loud because all speakers (except the one in the middle shut off (I assume because its not connected to the amp). I would like to be able to turn up the volume without the speakers shutting off....would this be an amp setting? The installers tuned it a few times, but this cant be normal operation for an expensive stereo install. Any input would be helpful!

 

[DocL]

I'm not a stereo professional, but it sounds like the amp is "clipping" out because the speakers can't handle the power.

 

[CL65 Captain]

Yep. turn the gains down. As amps start to clip they get very inefficient and produce alot of heat and thus tripping the thermal protection on the amp. You are lucky that you haven't toasted the speakers yet. It is obvious that you need more power...and alot more. The truth of the matter is that you need to turn the amp down AND stop listening to the stereo that loud. I am sorry, but a 10x increase in power is what it takes to increase 3db. It is a never ending chase so... long story short, turn the music down a bit unless you are willing to open your wallet big time and the NSX is one of the worst platforms to try to do a stereo in.

 

[01blacks4]

alpine radio?

 

[sptrader]

That can also be caused by running power or speaker leads with too high of a gauge of wire. (I've experienced both)
(wire is too thin for the current that you're pulling to drive the amp or speakers etc)

 

[Hugh]

a 10x increase in power is what it takes to increase 3db

Actually it is a 2X increase in power that produces a 3db increase in volume.
1 db is the smallest change in sound level detectable by the human ear while 6 to 10db is perceived as a doubling of volume. Of course this is subject to some variance depending on the speaker's efficiency.

With a 12" sub and 3 mid-highs our friend hobert's single amp is obviously not up to the task. The sub is what is causing the problem and needs it's own amp of about 150 watts while a 3 channel amp at 75 to 100 watts a channel should do the trick for the 3 amigos.

 

[Hugh]

I'm not a stereo professional, but it sounds like the amp is "clipping" out because the speakers can't handle the power.

No you're not. An amp "clips" when it exceeds it's rated output voltage. It's the other way around from what you said. The problem is the amp not having enough current to drive the speakers.

In other words you're much more likely to blow up your speakers with an underpowered amp and one rated at a higher output than the speaker's rated input. Reason being is the underpowered amp will easily be driven to high distortion levels in an attempt to produce the same volume level as the higher powered amp will while driving the speakers with a nice clean signal.

 

[TURBO2GO]

You need to tell us what you have. It sounds to me like it could be not enough power, but most likely the amp is seeing to low of a load and is therefore shutting off. I don't know what the amp is, how it is configured, or how the system is wired, but the quickest way to send an amp into protection is to give it too low of an impedance to deal with. I can almost guarantee you that if you look at speaker impedance and what the amp is designed to drive, there is a problem.

I smell inexperienced installers here... a 12" is really too big for the floor, which means the box is probably too small... also I really wonder how some people run amps in an NSX trunk... that area has no ventilation and gets very hot especially with an aftermarket exhaust. I put my car wash towels in my trunk and a week later they are still wet. I mean that is one sealed cavity... so your amp may be trying to deal with heat issues as well.

 

[DocL]

No you're not. An amp "clips" when it exceeds it's rated output voltage. It's the other way around from what you said. The problem is the amp not having enough current to drive the speakers...

Good to have you back. I knew it was either the speakers are under rated or the sub was too small but I wasn't exacly sure. Besides, the OEM Blows stereo sounds just fine to me That's why I'm not a professional.

 

[hobertgracie]

wow....great feedback.

OK...here are the details on what I got and I will respond to a few other things:

Apline Deck (ALPCDA9856)
2 - Kappa 6 1/2 door speakers - Infinity 62.7i Infinity Kappa 62.7i 6.5" 2-Way Speakers (Pair) Model 62.7i
1 - Kappa 5 1/4 center speaker - Infinity 52.7i Infinity Kappa 52.7i 5.25" 2-Way Speakers (Pair) Model 52.7i
Alpine Amp (ALPMRVF345) 75 Watts x 4 Channels
Premier Sub - could be 10" and not 12" as previoiusly stated (yea...im not a stereo guy )

I have had great stereos in the past and have never seen this problem and I would think it would be an easy fix to get some LOUD music out of it without this problem.

The entire reason for getting a beafy system was so I could hear it when the top was off going down the road...its works for the most part but I have to be careful how loud because it will shut off on me and I have to power off the deck and power on again.

Thanks again guys for all the feedback! Let me know some suggestions and I will attemp to resolve!

 

[Ponyboy]

hobertgracie, when are you going to come to a local event?! Please forward your contact info when you get a chance.

At the Sept. 1st event, Shaun Rey showed off his stereo system. I think you would have gotten a kick out of it.

 

[hobertgracie]

Sent you my contact info...looking forward to the next event!

 

[Shaun Ray]

Just curious how the sub is wired up to your 4-channel amp. I presume 2 channels are bridged to mono. If so, the sub woofer must be 4-ohm load minimum. If the sub is a dual voice coil, it might be configured to a 2-ohm load. This would over work the amp.

Also, is the amp in the trunk? If so, just curious if the problem may be heat related - the trunks get hot! Or, do you see a drop in volume right out of the gate.

Come up to Wichita some time. I'd be glad to take a look at it.

Shaun

 

[hobertgracie]

Getting a little technical, I dont know how the sub is wired so couldnt answer that one. The amp is in the trunk, but the problem happens right out of the gate so I dont think it is an overheating problem...It must be a configuration issue or something. I have tried different settings on the deck to get different results that produce pretty good quality.

I was hoping that it might just be a power issue that I need a larger amp, but I am told this should be enough for what I have to do what I want....I couldn't answer that one.

That would be great if we could plan a time for me to come up, I actually have family in Wichita and could stop by to get someone that knows what they are doing to take a look. Send me a private message and let me know how to contact you and we can set something up.

Thanks!

 

[Hugh]

Good to have you back. I knew it was either the speakers are under rated or the sub was too small but I wasn't exacly sure. Besides, the OEM Blows stereo sounds just fine to me That's why I'm not a professional.

You're extremely professional, you're just not an audiophile. On another note I was speaking with Ben about getting my HREs re-conditioned and he told me someone slashed all 4 of Ted's tires and then Tire Rack somehow ruined his wheels. Since I'm not talking to the little bald fuck I don't know the details.

 

[MiamieNeSeX]

Good to have you back.

Why do you encourage him?


Armando