RCA Cable Length = big power drops??

[ChrisCan 10+ year member]

How bit a deal is the length of the RCA cables? I remember reading that you loose signal strength more if the cables are longer, how much are we talking about?

I just wired a 4 channel 75 Watt RMS channel to fronts and rears in my car. Although they sound good, it doesn't seem to be much louder than my old 30 Watt per ch 4 channel Rockford Fosgate amp. I also replaced my OEM speakers with some same sized aftermarket ones. The way I figure, it should sound louder and better- but right now, it just sounds better and not so much louder. My 4X75 amp is an Audiobahn A6004T, which I heard was over rated, but I figure it should still be noticeable louder.

I have some pretty long RCA cables from the head unit to the channels on the amp for the rears (probably they are 3-4 feet longer than needed- it was all I had), and they are the ones that seem not to be so loud (they are 6 1/2, the fronts are only 4" and sound almost as loud right now). I have both of then on a HPF, since I have trunk subs on a second amp. The amp gains to both are maxed out,

Could a longer-than-needed RCA cable make that much power difference? The amp is under my passenger seat, so it is not so far from the HU. I can shorten the cables pretty easy, but is this likely the problem? Are there other things I should check, too?

Power on the amp seems to be 13.8 V when engine is running.

Thanks,

Chris

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[SSS 18734 5,000+ posts]

not enough to make the slighest audible difference.

 

[jrz126 10+ year member]

hearing is logarithmic, for it to sound like it is twice as loud you need to increase by 10 dB. And you need twice as much power to get a 3 dB gain. I read that somewhere, I dont know if it is correct or not.

 

[JimJ 5,000+ posts]

Unless you have over a hundred feet of RCA cable, you're not going to notice any differences.

 

[Alpineinstaller 10+ year member]

take the amp off HPF to FULL. See if that helps.

 

[Loud3 10+ year member]

hearing is logarithmic, for it to sound like it is twice as loud you need to increase by 10 dB. And you need twice as much power to get a 3 dB gain. I read that somewhere, I dont know if it is correct or not.

Actually, 3db to 4db more than what you started with is the same as doubling your output.

 

[JoseMCeee 10+ year member]

take the amp off HPF to FULL. See if that helps.

I would just leave it on HPF and lower the xover.

Also play with the gain. What is it at right now?

 

[ChrisCan 10+ year member]

The crossover for the HPF goes up to 750 Hz; that is where I have it now for both channels 1+2, and channels 3+4.

I have gains maxed out as well for both channels 1+2 and 3+4. I figured I'd need to lower the gain on the fronts, since they are only 4" (maybe handle 25W RMS) and the amp is supposed to be 75W RMS per channel.

I'll try to play with the crossover and gains.

Thanks,

Chris

 

[Silver 10+ year member]

I heard powerwire is more likely to do this than a RCA. Also are your wires hooked right up to the speaker or do you have a 16ga harness for each? IMO

Only because I run 12ga throughout my whole car. Moving to 16 or 18 ga harness would defeat the purpose coming for running a 12 wire..

I dunno though, just my thoughts.

For example, a Q-Logic box has like 20ga OEM. Hooking up sub wire (12ga) to the box would make the 20ga not handle the complete power coming from the 12ga, amp, ect, ect.

I ran 12ga from the amp to sub and it makes a difference for listening issues.

 

[n2audio 5,000+ posts]

It's been said, but I just thought I'd add -

You're not losing signal strength in your rca's. Yes, the wire is very small, and in your case fairly long, but the current flowing in them is microscopic and there's not enough voltage drop to make any difference at all.

As for your output problem -- You have the HPF at 750hz??? That is WAY too high - even for the 4's. You're cutting pretty much everything below high vocals.

Set your 6.5's to high pass at 60 hz or so, and the 4's 100-150. That should make a HUGE difference. Lower both gains before you do this. Start with them at the minimum and adjust from there.

 

[JoseMCeee 10+ year member]

It's been said, but I just thought I'd add -You're not losing signal strength in your rca's. Yes, the wire is very small, and in your case fairly long, but the current flowing in them is microscopic and there's not enough voltage drop to make any difference at all.

As for your output problem -- You have the HPF at 750hz??? That is WAY too high - even for the 4's. You're cutting pretty much everything below high vocals.

Set your 6.5's to high pass at 60 hz or so, and the 4's 100-150. That should make a HUGE difference. Lower both gains before you do this. Start with them at the minimum and adjust from there.

yea man. HPF at 750hz is only playing 750hz and above. A lot of stuff happens between 100hz and 750hz. Follow the steps as N2 described and it will be much louder. Again lower the gain first then adjust the xover. When the xover is set, turn the music volume to the loudest you will ever play it at (usualy 3/4ths of the volume) then turn the gain up slowly until it sounds good and doesnt distort