randomwalk101

I did Dr.Cookie's sub mod (RMB8) with an aftermarket amp and using stock HU. The problem is the stock head unit doesn't have the BASS control for the sub only. Some musics, the bass is too much. I want to tone the RMB8 down with certain musics and bring it back up with certain ones. If I use the bass control on the stock HU, it will bring down ALL bass (ei., all the bass in the door's speakers). Is there any simple device I can get installed to control only the REAR SUB? I'm thinking something that can attach to that aftermarket amp and control only that amp or that RMB8 that is being powered by that amp and leave the door speakers alone?? This device can have a remote or even a wire/knob that I can run to the front and velcro'ed somewhere that I can turn up or down the rear bass....

Thanks for the help guys. BTW, the amp I am using to power that RMB8 is Alpine V12 2 chanels 340watts bridged. Not sure the model...i think it's something like MRV-T340 ??

egilsrud

Random,

I looked at Crutchfield's web site for some info on your amp...looks like you have an Alpine MRV-T420, correct?

Unfortunately, this amp doesn't have an input for a remote subwoofer level control. Two Alpine mono amps, the MRD-M300 and MRD-M500, can use an optional remote level control knob (RUX-4180). So you're stuck with your current level, unless you can exchange your amp for a different model.

I have an Xtant A3001T mono amp powering my subwoofer (Diamond Audio M10D4). I wasn't entirely happy with the setup until I added Xtant's remote level control. It is mounted in the unused slot to the right of the display brightness control. It makes a HUGE difference - I can tailor the sub level to the music I'm listening to. It's useful when listening to sources that overemphasize bass (like FM).

randomwalk101

Okay, just pulled out the amp and looked for the model #...
It's MRV-T502 !!!! any luck with this model?

egilsrud

I found a spec sheet for the MRV-T502 on the web:

http://www.ifb.pl/~mateo/car-audio/m...ec-install.pdf

Unfortunately, it doesn't provide an input for a remote subwoofer level control, either.

randomwalk101

Thanks for your fine research. I have an IDEA that MIGHT work

Okay, you can add another EQ and control it...but then you will need to add an aftermarket amp and by pass the stock amp, stock EQ etc... too much trouble...

Now, you can get a cheap EQ (there are some for like $30). Use the RCA (input) which you spliced from the stock "Blose" sub that is currently feeding the amp (aftermarket) that is powering the RMB8 rignt now, hook that RCA to your newly added EQ (input). The sub OUTPUT from that EQ, run that and use that as INPUT to your amp that is powering the RMB8....all other output from the EQ is ignored. So now you can use the SUB control button on the EQ to boost up or tone down the rear sub ONLY...which is what you want.

Analysis:

1) Yes, input to the EQ from stock sub line is (pre-amp), low pass, thus u will not get a full range at output..but you dont' need full range...you only use the output for sub only thus it is okay.
2) Since you have not touch the mid/high etc output/input from the stock HU to speakers, they should function as normal.
3) This serves as an EQ but only controlling the sub. All other knobs on the EQ is not use (just for dummy since their output are not used).


WHAT DO YOU GUYS THINK? WILL THIS WORK? (not tested...just idea)

I've also seen cross-over with remote gain..you can run the RCA input from stock sub feed line to cross-over and then to amp that is powering the RMB8 and use the remote gain from the cross-over to control the sub..but this cross over is expensive $150 and up....The EQ is probably better and will fit nicely in that storage slot above the stock HU (non navi cars).

randomwalk101

so no one knows if it (the above) will work???

Of course, there is a inline (RCA) volume control made by PAC ...just found out today from a audio enthusiast..probably going to give that a try first.

egilsrud

I'm still trying to completely understand your first idea - guess I'm a slow reader

Seriously, my suggestion to you was going to be to use a potentiometer to adjust the line in signal strength - but I see someone beat me to it! That's definitely the way to go - nice 'n simple.

Good luck, and let us know how it turns out!

randomwalk101

Okay, my first idea is this...

RCA (input signal) -----> amplifier (for sub) ---> sub

mod:
RCA(input signal) ---> EQ ----> amplifer (for sub) --> sub

So basically, you put the EQ in the dash somewhere...turn the volume control knob or the bass control knob or whatever control knob on the EQ to tone down or up the signal to the amp thus in effect controlling the sub volume...so some songs like jazz etc, you don't want your sub to boom like crazy...and some songs like hip-hop, rap, you want to crank it all the way up... That's the idea.
But the potentiometer is cool too...i'm looking into that

randomwalk101

problem solved...thx for your help ( i guess that's egilrud only?)

SwampGas

Why can't you just run the preamp signal line to the amp through a potentiometer? Go to radio shack, buy one, and just put it inline with the signal. Done.

egilsrud

Random, glad to hear that you've got things worked out...I assume you went with the inline volume control (basically a potentiometer), correct?

Your EQ idea is interesting - but I would characterize it as a "Rube Goldberg" solution - which means it has way more complexity than necessary. Adding an EQ into the bass circuitry merely to adjust the input level is overkill. A cheap EQ could also introduce noise into the signal, and that's not good.

Give us the details of your solution, please! I gotta know!

randomwalk101

It's a inline volume control for amplifier..has couple pairs of RCA, one to hook to input, and the output from the controller goes to the amp. The knob adjust the volume (signal) to be received by the amp. thus controlling the output volume. That's it. So yeah, it's basically a potentiometer in theory...just that I don't have to do all the soldering or what nots. Only $12..can't beat that

fsttyms1

or you could open the amp up solder a couple wires where the gain on the amp is and relocate the amp gain to where you are sitting... many have had sucess with that mod