Installed the Alpine 7894 HU last week. This weekend I finished the sub box and got the amp and sub installed. The amp is the Alpine MRD-M300 and the sub is the Alpine SWR-1041D. I turned on the subwoofer output on the HU and used the standard configuration for the amp that was in the instruction manual - NO THUMP!? The sub turns on and is working but at VERY low levels. Need help.

PLEASE! Thanks in advance.

 

Okay, I'm just going to throw a ton of ideas at you.

First, double check the crossover settings on the amp. Make sure that it's set to LP (low pass) and tuned to an appropriate frequence (say 100Hz, but depends on personal preference). Play some different test frequencies to be sure the crossover is working correctly.

Make sure the amp gains are where you think they are. I have some older V12 Alpines and the gain pots can be hard to read. You may think you're at 80% power when you're really at 30% (180 degree difference on the dial). Play around with the gain dials while everything is off (can't damage anything that way) to make sure you know where the rails are.

Are you playing with the HU at or near max volume? Your other speakers are more efficient than the sub and depending on what's driving them they may simply be outplaying the subs at normal listening levels. You might just need to adjust the gains to balance everything out.

If you're using a dedicated sub RCA output from the HU, make sure it's turned on, and check the output level (boost, reduce). Check if the HU has a built in low pass filter, and make sure it's not set to -24dB/octave above 20 Hz. That would hurt the output just a tiny bit. If you're using a crossover in the amp, turn off the one at the HU, unless you want a REALLY steep rolloff curve above the crossover point. Remember, those rolloff slopes are additive if you have multiple crossovers acting on the signal!

If you're using rear RCA outputs for the sub, make sure the fader isn't pushed to the front.

If your amp has independent power supplies and multiple fuses, check all of them, one may be burnt, taking out one of the amp channels.

Your sub might be mismatched to the volume of the box, thereby reducing its efficiency further. May need to try a different driver.

Hope that helps,

My 2

 

adjust the gain or input sensitivity

 

I have the exact same sub and amp and you will love it when it's set up right...i find the front door components are very important in giving you great sound(i have Focal 165 V with external amp)

 

Here we go. Before I begin thanks to those who have tried to help. This is what I have done thus far.

1) Turned on the Subwoofer output on the HU - using dedicated RCA sub-out
2) Turned off HPF and LPF on the head unit
3) Turned bass and treble to '0' on head unit so I could determine that the bass was not from front or rear speakers
4) Configured the amp with standard settings as denoted from the factory
5) *There is no gain adjustment on this V12 digital amp. Alpine technically terms it 'input' (this is where I think I am missing something).

6) For the 'input 'Alpine instructions say to increase the volume continuously until the 'over' light blinks on the amp. At that point set the input. I did this at 24hz (factory recommendation) and at 0hz. At 24hz the amp registers about 14.8v and at 0hz it registers about 13.9v.

7) On Alpines web-site I found 2 documents. One was for distributors on maximizing settings for a demo board. I changed my amp settings to those recommended, a little difference but nothing to brag about. The second was similar but discussed more about digital vs. analog amps and this is where they made the distinction between 'gain' vs. 'input'.

Here is the URL to Alpine's tech center if interested: Alpine Tech Center

The first document is called Maximizing the output of your MRD-M300MRD-M500 the second is V-12 AccuClass-D Basics
You can also view the owners manual for any of there products.

Although bass, quality, etc... can be subjective my expectations were that I would here some modest bass/thump while listening to Drowning Pool, Linken Park, AC/DC and similar at reasonable listening volumes in the car (not moving!). I only hear any discernable bass when listening to RAP -- I don't listen to RAP. When I read about others who have this configuration and they say there sub rocks at 70 mph I don't get it. Are my music preferences or expectations skewed?

Sorry for the long one but really need more help. THANKS!!!

 

[QUOTE]Originally posted by TampaS2k
[B]
6)

 

For the input 0hz is the lowest and 24hz the highest. As for adjustable bass there are 2. One is for the amp on the HU which from what I can tell controls the bass on the fronts and rears as well as a subwoofer control which I enabled when I connected the subwoofer pre-outs. The bass control works fine but the subwoofer control doesn't seem to do anything.

 

OK - after reviewing the Users Manual I have a couple ideas

First - I think you have to do step 1-2 (set input level) before you do 1-1

1-2 set the level at 0.5V (or -0 dB)

then go back and do Step 1-1

Then do Step 2-1 - turning on the LP filter

Then do Step 2-2 - set Freq at 120 Hz

You can play around with the sub-sonic equalizer if you like but I assume the defaults should be ok to start

Then do Step 9-1 and make sure your safe mode is off

Hope this helps

 

I'll give it a shot tomorrow - thanks for taking the time in read the Users Manual. I'll repost after I try.

 

One other last thought - did you wire your sub in series?

Since it is a Dual Voice Coil (2x2ohm):

If you wired it in series you would have a 4 ohm load and get 150Wrms from your amp.

If you wired it in parallel you would have a 1 ohm load and your amp is not 1 ohm stable - so it may be entering the protection mode.

The image below shows a dual voice coil (2x4ohm) possible configurations. Your sub is a dual 2ohm coil sub - but the idea is the same.

You will want your sub wired as shown in the lower drawing.