Time for an Amp upgrade?

The most recent tuning of my system used an oscilloscope as well as the RTA program on my laptop and revealed some distortion in the ~200Hz and 315-400Hz ranges on the front stage speakers. I suspect this has to do with the power they're getting. I haev the gains set at a very modest 30-35% and used the GEQ to get rid of the pesky trouble frequencies.

I have the 5.25"midrange and 6.5" midbass on a single channel from the "Front 2" on the Alpine PXA H701. From active the processor it goes to an Alpine MRp F250 amp that I have wired bridged (100w per channel) to the Left and right door speakers (tweeters are on a different amp). Those channels are then split by the Alpine SPX 17MB passive crossover to the mid and midbass.

THe Midbass has a 40w RMS while the midrange has a 35w RMS. I Think my 100w per channel just isn't enough to give me the powerful midbass I want (Especially competing with the JL 500/1 and 12w6v2 sitting in the back)

Thankfully I built my amp rack with room to expand and i have enough room for the slightly larger MRP F450 which could give me 200w per channel allowing me to crank the full range speakers without distortion.

thoughts?

doooooo it

Do you realize that having flat and equal output from the speaker leads does NOT result in flat output? Tuning from the leads is not actually much tuning at all.

i want pics of your setup ,,, NOW

Here was the most recent procedure:


1) turn all gains down, turn radio to level 30 (about 90% power)
2) Set all GEQs to flat and disconnect subwoofer (I tune that seperately)
3) Run sine-wave test tones at various frequencies to set gains using ossiloscope to look for distortion.
4) With gains set, run pink noise and using the RTA, adjust GEQ on each channel for a flat response curve.

JSewell wrote:

i want pics of your setup ,,, NOW

say please...

hey now, i don't make your mom say please

jk man

Lol. you made me laugh, that's good enough. Here are the pics:

niceeee, im diggen the box design, i assume custom fab'd

did you dampen the entire car, all i see is the door

JSewell wrote:

niceeee, im diggen the box design, i assume custom fab'd did you dampen the entire car, all i see is the door

Yes, the box is DIY. Wish i'd learned how to do fiberglass Before i built it tho.

I dampened the whole car, plus acoustic foam in key areas:

Dear god, I love your system.

jw, does the matting help with the cooling of your car too?

all that mat makes this wanna be my first mods to the upcoming truck

JSewell wrote:

jw, does the matting help with the cooling of your car too? all that mat makes this wanna be my first mods to the upcoming truck

I'm not sure if it makes a difference here in the houston heat. It's been 100+ in the shade for the past week.

Radioflyer wrote:

Here was the most recent procedure: 1) turn all gains down, turn radio to level 30 (about 90% power) 2) Set all GEQs to flat and disconnect subwoofer (I tune that seperately) 3) Run sine-wave test tones at various frequencies to set gains using ossiloscope to look for distortion. 4) With gains set, run pink noise and using the RTA, adjust GEQ on each channel for a flat response curve.

I'm not sure how you're sensing the output but a oscope isn't doing much. It sounds like a good idea to use an oscope but it’s not. Like I said, flat output from the speaker leads is not flat output to your ears. Why?

One, theoretically speakers are linear but in reality they aren't. Cone shape, material, imperfect magnetic flux, metal flaws, etc. cause the output to not be flat.

Two, the effects of the car on the system is a TON. The most basic effects are that anything below ~250Hz gets a 12dB/oct boost (frequency varies by vehicle size) and there's going to be a couple peaks at ~350Hz & 500Hz due to the reflections in the cabin (again, these are estimates and vary a little by vehicle size).

The only way to know that what you hear is flat and true is to have a few microphones and measure it.

would testing with the top off, hatch and doors open isolate the driver's acoustics?

I only have one mic input at the moment.

You want to test it as you would be listening to it. Windows open vs closed will make a difference (primarily in bass output). With everything sealed up you are able to pressurize the cabin and bass increases. Think of the car as a speaker box b/c that's really what it is. It's a very small space that acts like a box, you just happen to be inside it.

PwrRngr wrote:

You want to test it as you would be listening to it. Windows open vs closed will make a difference (primarily in bass output). With everything sealed up you are able to pressurize the cabin and bass increases. Think of the car as a speaker box b/c that's really what it is. It's a very small space that acts like a box, you just happen to be inside it.

So far i've been testing it with me in the drivers seat, the Mic mounted on a suction cup aimed at the channel in question.

Radioflyer wrote:

JSewell wrote: jw, does the matting help with the cooling of your car too? all that mat makes this wanna be my first mods to the upcoming truck I'm not sure if it makes a difference here in the houston heat. It's been 100+ in the shade for the past week.

ahh I was jw, im actually in the same situation as you, experiencing this heatwave from hell