Killabee44

Guys,

Old school setup! lol

I just got a hold of an old JL Audio 300/4 and a pair of old MB Quart QSD216 speakers that I plan on using for the front of my 04 TL (hopefully they fit).

I would like to add one sub to run in bridged mode for the other two channels of the 300/4.

What's the best way to do this? would a line converter work? Or would I need a sound processor?

Also, I have no idea how to set up the crossovers for the quarts. If anyone can help me with that, I would appreciate it.

It's been a while since I've messed around with car audio so bear with me.

Budget: I would like to spend maybe $300 or less for the sub. I know it's not a lot, but it's what it is..

Also, how to:

Tap into the factory amp for the leads to the front speaker and the rear sub.. Which wires are which? Which are the inputs to the factory amp? Does anyone have pics?

Thanks.

DiamondJoeQuimby

iTrader: (2)

You'll need something 8 ohm. The 300/4 uses one power supply and will give you 37.5 watts on the front end w/ 4 ohm speakers and a 4 ohm bridged sub. You need the total impedance across both channels front and rear to be the same.

Killabee44

Wow, didn't know that. I thought it would put out 75 watts to each speaker?

So, even if I get an 8ohm sub, would my two front speakers still get 37.5 watts each? If so, that's terrible..

Is it that you only get the 300 watts if you use 8 ohm speakers all around?

Killabee44

Also, thinking of adding a Rockford Fosgate BLD. Do you think that would help?

About the BLD's. Do you only usually use them on the sub? What about the front speakers? Would I need another? or do they sell 4 channel BLD's. Thanks.

MarcoNorthPolo

37.5 watts to your front speakers is more than what the stock speakers get, they're rated at 15 watts or 20 watts each (I can't remember which.)
The stock sub is rated at 40 watts.

Killabee44

Yeah, I read that our stock speakers are rated at about 20 watts, but Im replacing them with some rated at 90 watts. I was hoping to push at least 75 watts out to them.

DiamondJoeQuimby

iTrader: (2)

No. In order to get 75 x4 the impedance on each pair of channels needs to be the same. The range is 1.5-4 ohm stereo, or 3-8 ohm bridged.

It will use the lowest impedance voltage rail based on the connected load. So if you have 4+4 on the front (8 ohm total) and 4 ohm bridged on the back (4 ohm total) it will use the 4 ohm rail. But the front will have an 8 ohm total load thus halving the power. It's kind of a quirk to the 300/4 that you don't run into on their amps that have independent power supplies for each channel pair.

As long as you go 4 ohm stereo front and 8 ohm bridged rear you'll get 75x2 front and 150x1 bridged on the rear.

DiamondJoeQuimby

iTrader: (2)

You don't need a BLD. That amp has a balanced differential input. You can input just about anything short of screaming at it with a bull horn and it will work fine.

And as a side note those QSDs (if the old school circa early 2000s) are truly badass speakers. The x-overs are assembled with an aluminum base to dissipate heat so the values of the components does not change thus affecting performance.

Killabee44

Great info. Thanks.. I was thinking a BLD or a Matrix since the voltage coming out of our stock stereos is so weak, I thought it would make a difference, but I guess not with this amp! Saves me some $.

I'll look for an 8 ohm sub. Would I need to use the crossovers with this amp and the factory tweeters?

Killabee44

Hmm..

Ok, so while looking around for a 8 ohm sub, Im finding that they aren't really used very much. So, it will be harder for me to sell mine when the time comes.

I can use the JL amp to push two 12" 4 ohm subs, but I would need another amp to push the front speakers.

Can anyone recommend a decent amp to push those quarts? Im looking through the Black Market.. but not sure what to get.

thanks.

DiamondJoeQuimby

iTrader: (2)

You can use a DVC 4 ohm sub to get to 8 ohm as well.

Do you not have the full QSD kit? (QWD164 + QTD25 + x-overs) If so, no need for the factory tweeters.

Killabee44

I have the full kit, but not sure how to wire those crossovers or where exactly Im gonna install them inside the door panel. Im gonna need a hand with that. ..They do look badass though.



As far as the DVC 4 ohm sub, any you can recommend?