Sub Enclosure problem on a PG RSDc 10" Sub

finkle636 · Post by **finkle636** » Tue Oct 14, 2008 12:21 pm

Right. I've reverted back to the 2nd (deeper) box and its far better.

I still think the trunk was making up for the subs incorrectly designed box when placing it in the centre.

Now i have a new problem.

The sub kicks hard and does play low but some lower freq's seem to be missing from some songs (and i know they're there dammit!!)

When i turn the remote lpl up i can just about hear them but they are not as loud as they should be, and by that point the other freq's are far to loud.

I thought the boost affects the whole 30hz - whatever the x-over is set to. ?

I have tried adjusting the x-over with no success as its the lower tones its missing at any given point and the subsonic filter is resting on its 5hz stop.

Capital_M · Post by **Capital_M** » Tue Oct 14, 2008 12:42 pm

Boost only affects the 45hz area

Post by **Bfowler** » Tue Oct 14, 2008 12:42 pm

do you have the bass boost (on the head unit or amp) up? maybe the low end isn't lack so much as the high end is over compensated?

from my experience with the RSDc's, the extreme low end is its main strength

finkle636 · Post by **finkle636** » Tue Oct 14, 2008 12:51 pm

I think i've figured this one out.

I'm using a Sven 4 line out convertor connected to the rear speakers as i'm using the stock bmw head unit.

I think i have turned the boost up on the amp and increased the sensitivity to make up for the 'quietness' of the channel.

So what i'm hearing is an over amplified 'boost window' if it only affects the 45hz area.

And everything outsided this boost window is quiet as the boost is turned up that much just to get some sound out of the sub.

Does this make sense?

finkle636 · Post by **finkle636** » Tue Oct 14, 2008 1:10 pm

Should i buy a PG line driver to compensate?

Post by **Bfowler** » Tue Oct 14, 2008 1:18 pm

thought that boot looked a little familiar!

so when you attached the LOC, did you use the amp inputs, or rear outputs (the speaker side)?

sounds like one of the problems you may be running into is the factory amp has already crossed over the sound, which you are "re-crossing" on the amp

finkle636 · Post by **finkle636** » Tue Oct 14, 2008 1:28 pm

I dont have a factory amp (well i do but i can unplug it and the speakers keep on running), it runs straight from the back of the head unit to the speakers (i know cos the colours are the same).

I have it soldered it to the rear speakers

finkle636 · Post by **finkle636** » Tue Oct 14, 2008 1:34 pm

Should i be getting an adequate amount of volume from the sub without having to use the boost?

Post by **Rold Gold** » Tue Oct 14, 2008 1:36 pm

I'd say change out the HU...........

Post by **Bfowler** » Tue Oct 14, 2008 2:12 pm

ok....so starting from the begining (source)

you have the bmw head unit, which is going to a 4 channel LOC, which then goes into a 4 channel amp?

and the sub amp is getting signal from the left rear channel of the full range speaker amp?

so you are bypassing the factory amp altogether

that should be leading to a clean signal... this is very odd

finkle636 · Post by **finkle636** » Tue Oct 14, 2008 2:24 pm

No,no

Head unit to all 4 speakers (forget the factory amp)

rear rsd 4" coax speakers have the loc rear channels soldered to them in correct polarity (front cannels on LOC are unused)

LOC to RSD600.1 monoblock amp

Amp to sub

finkle636 · Post by **finkle636** » Tue Oct 14, 2008 2:33 pm

Diagram

Post by **Bfowler** » Tue Oct 14, 2008 2:52 pm

I'm at a loss. i can't think of any reason you would be getting the results you are getting.

maybe try posting the question on a bmw forum?

that is a e46 convertible yes?

you might try e46 fanatics or bimmer forums

finkle636 · Post by **finkle636** » Tue Oct 14, 2008 3:14 pm

The more i think about it, the more i'm sure i'm not getting enough voltage out of the LOC.

I think the ONLY thing i'm hearing is the effects of the bass boost on that quiet signal. As it amplifies only a few freq's around 45hz

This would explain why the extreme lows (and probably highs) are faint but it kicks like hell.

Post by **stipud** » Tue Oct 14, 2008 3:51 pm

Or your rear speakers have a factory high-pass crossover on them. That is more likely I would think...

finkle636 · Post by **finkle636** » Tue Oct 14, 2008 3:58 pm

If i was to play a test tones cd, would this rule that out?

Post by **stipud** » Tue Oct 14, 2008 4:05 pm

Audibly perhaps, but no way to truly measure it unless you have an oscilloscope or true-rms voltmeter handy.

Post by **VW337** » Tue Oct 14, 2008 4:31 pm

BMW?

3 series most cases** Looking into the trunk, behind the left side panel there is a factory amp. this amp receives 4 channels from the factory HU and passes 8 amplified and XO'd channels out. The leads into the amp from the HU can be tied directly into for RCA level to the RSd amp. You do not need the LOC.

Also when you rebuild your sub enclosure make the face or the back slanted slightly.

Post by **Bfowler** » Wed Oct 15, 2008 7:24 am

^thats what i thought...see his diagram

finkle636 · Post by **finkle636** » Wed Oct 15, 2008 8:38 am

Progress update.

It was as i thought.

I turned the boost totally off and increased the sensitivity to max. and all the sounds were present and in balance with each other(although very quiet).

I removed the rear speakers so the only output on the rear channel coming from the head unit would be the LOC only. This made the sound alot louder so i was able to reduce the sensitivity on the amp.

I have ordered a PG line driver to up the input signal a bit more as its still not that loud (although its better with no rear speakers).

Thanks for all your help guys and im sure it will all go to s**t again once i make another box that fits under the trunk expander (although it will be much deeper this time!)

Post by **Bfowler** » Wed Oct 15, 2008 9:07 am

so why are you so against a aftermarket head unit?

seem like this would eliminate teh line driver, and LOC's

Post by **stipud** » Wed Oct 15, 2008 9:08 am

Or if you can splice into your factory RCA wiring, you can add an RCA end and bypass the LOC completely. A linedriver can still help in this case, but I would get that good-for-nothing LOC out of the equation ASAP!!

finkle636 · Post by **finkle636** » Wed Oct 15, 2008 9:14 am

Im not against them, i just dont have the funds... yet.

My plan is for the Nak cd400 as i can get it from a registered uk dealer with a warranty.

I had an alpine 9835r but i sold it a year ago with my last car.

I have to use a sven 4 line driver as the bmw head unit uses a differential signal or something (isolated form ground), according to e46fanatics.com

Post by **Bfowler** » Wed Oct 15, 2008 9:19 am

you are actually the first and only person i have ever heard of powering speakers directly from the head unit in a e36 or newer bmw

did you run new wires for it?

the nak is a sweet deck that blends perfectly with the interior.

Post by **stipud** » Wed Oct 15, 2008 9:26 am

finkle636 wrote:I have to use a sven 4 line driver as the bmw head unit uses a differential signal or something (isolated form ground), according to e46fanatics.com

Do you mean balanced signal? If so, you can use something like an Audiocontrol Three.1 or Four.1 like I do (my Saab also has a balanced signal). Alternatively you can splice into the + signal, and then just take a ground for your RCA pole somewhere. Leave the stock - signal as-is.