Subwoofer playing very low/quiet - diagnose?

[ls20 10+ year member]

I went home at lunch today to pick up my new Image Dynamics ID8 v.3 dual-2ohm today. I didn't have much time, so I hastily wired it up and threw it in the trunk

It plays , but very very quietly - I can BARELY see the cone moving. Its definitely NOT using its 17mm of excursion!!!

Since I am currently at work, I cant go out and start diagnosing it, so curious if anyone can throw some suggestions out here.

HU: Alpine 9857

Amp: JBL GTOII 75.4

Speakers: Boston Pro60 - 125W RMS, 3-ohm

Sub: ID8 v.3 - 150W RMS, dual 2-ohm

Amp makes 100 x 4 @ 4-ohm,

140 x 4 @ 2-ohm

280 x 2 @ 4-ohm (bridged)

Subwoofer recommended ~.4ft sealed box. I put it in ~.4ft sealed box. Connect them in series to present 4-ohm load. (bridged+ to vc1+, vc1- to vc2+, bridged- to vc2-).

HU at 70% volume. EQ off. Subwoofer level set to 0. Bass boost on amp 0dB. Gain setting at 4v = sub barely plays. (comparatively, at same gain settings for speakers, theyre loud).

Flip the filter between Flat and Low pass (120HZ)... nope... still quiet. crank gain up.. louder, but BARELY.

If I give it a bit bass boost, notch up the gains a bit (say, 500mV), add about 10 points to subwoofer level on the head unit, I can get start to get acceptable levels out of the sub

So what the heck is going on? Also tried swapping the sub connector from bridged to single channel mode... not much diff. Do you think I swapped the polarity? messed up when I connected the voice coils? (cant wait to get off work!)

Click to read more...

 

[Hundreth 10+ year member]

Set the subwoofer level to +15 on Alpine units otherwise you aren't getting the rated pre-out voltage.

 

[2loud4u 10+ year member]

Set the subwoofer level to +15 on Alpine units otherwise you aren't getting the rated pre-out voltage.

x2 reset the gain with sub level all the way up.

 

[jimrhit 10+ year member]

See if you wired the coils out of phase from each other ... basically they could be working against each other.

 

[Calikid 5,000+ posts]

//content.invisioncic.com/y282845/emoticons/word.gif.64b12e39f936af3b4fff38a1c0bd0244.gif

 

[Hundreth 10+ year member]

See if you wired the coils out of phase from each other ... basically they could be working against each other.

That would result in no sound at all...

 

[LowEnd85 10+ year member]

im having the same problem with my sub. sometimes it will come back full swing and have full bass, then cut back down. its almost as if someones in my trunk turning my gains up and down randomly

 

[jimrhit 10+ year member]

That would result in no sound at all...

Sure it would ... not much, but I can assure you it would be moving a tad. Go try it yourself, it can move, but barely (don't give it a lot of power or do it too long, you'll cook it)

 

[ls20 10+ year member]

Set the subwoofer level to +15 on Alpine units otherwise you aren't getting the rated pre-out voltage.

serious?

i read this suggestion while researching, too... thats really BUNK!!!

i presume this is with newer alpines? i had 9815 with a weak kenwood amp and baloney cheap subwoofer and that one performed well without tweeking up the sub control.

jimrhit - when i set the amp on Flat (no filter), i could hear the upper range of music (vocals and all), so i think the phase is alright... but maybe its not indicative and i could very well be wrong

thanks so far!

 

[Calikid 5,000+ posts]

That would result in no sound at all...

wrong, u can still hear it, it will move but will sound all distorted.//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[ls20 10+ year member]

ahhhh yeaaaaa this thing pounds at sub level 12-15.

it wasnt getting progressively/linearly louder from 0-10, so i thought my install/setup was wrong. i thought default/flat level was 0, and didnt want to "artificially boost" the setup

now ive only got to get this thing to blend in well with the nice solid mids of the Bostons....

thanks !