I’m installing a powered 8” Kicker compact sub in the rear hatch area next week and considering whether to tap into the front-door or rear woofer signals. I’ve done some quick testing with a tone generator app and found:



Below 100 Hz most all of the output comes from the rear woofers, above 100 Hz output mostly from the front-door woofers. Also I get pretty bad resonant buzzing from the rear woofers at about 60-65 Hz. Based on these results I’m planning to tap into the rear woofer speaker signals - I’m mostly interested in augmenting kick drums and bass guitar in the below-100 Hz range.



Does this seem about right?



I’ve searched and have seen a fair bit of discussion on the front vs rear woofer crossover freqs but nothing very definitive. I’m also curious why Jaguar would bother with Dual Voice Coil drivers for the rear in a factory system with two woofers.



I have the 770 W Meridian system in a 2016 Coupe.



I’d appreciate any thoughts, particularly if anyone has experience adding a powered sub to the stock system. Thanks!

 

The subwoofer signal is centered around 30hz but the sweep is very narrow and isn't very musical. What we used to call a "one note wonder". The door midbass is centered around 100hz and runs between 30 and 300. The sub signal below 50 is quite loud and the midbass in that area is more subdued but there is plenty to work with.

Given you need to disassemble most of the trunk trim to get at the signal leads, I'd extend them all to a suitable length that gives you some flexibility. Try using the sub signal, it may meet your needs. But if not, you'll have access to the midbass leads without tearing apart the car again. Like I said, extend them all. Depending on goals and budget, it'd be pretty easy to get project creep and wind up with a full DSP amp repower. The Jag's sound system "tune" is the second biggest problem.

I'm using the midbass signal because I'm running my sub up to 70hz, 24db slope with time alignment set at 10'. That puts the lower end of the kick drums and bass guitar into a 12" driver with 1200 available watts that sonically is right up front and blends with the 100-300 signal coming from the doors.

 

Thanks Rob, excellent info and advice. I’ll definitely wire out taps to both sub and mid bass channels as you suggest. I’m tempted to wire out all speaker channels just in case I succumb to project creep but all I really need is a just bit more thump.



Since I’m using a mono sub with stereo inputs, I’m wondering what would happen if I wire the mid bass into the left channel and the sub bass into the right (for example). I could see this producing funkified results on the rare songs with strong stereo bass content, but it seems like a free way to get two band signal summing. System tuning might be a hassle with this set up. Is this a terrible idea for some reason I’m missing?

 

So, a couple things. Want to be careful about terminology and such. I said extend the speaker leads and you said tap them. Two different things. For your purposes, tapping them will work but if you wind up doing a DSP you'll need great big loops of leads for the coming and the going. So do extensions back into the trunk and then go ahead and tap them but at least you'll be prepared. I added 15' of speaker wire to each and almost every channel coming out of the factory amp (skipped the stupid mids above the subs), all looped back to the spare wheel well. Mind the polarity and label everything! Either way, you'll want to disconnect the existing subs, all four leads. There is no "stereo" below 90hz, not really. It's not "localizable". You definitely don't want to try and blend the sub channel with the midbass channel unless you have a DSP with summing and then it's not a great idea anyway. (That is straight from the AudioControl support rep!) The powered sub you have might show left and right inputs but I guaranty they're getting summed into the sub. Go ahead and use one left and one right from either the sub OR the midbass channels.

Fun fact: The 1998-2002 XJ has a 6X9 "sub" in the hat shelf. Dual coil. Clients existing driver was nothing but dust and JLR had no stock. I wound up using a PowerBass driver, only dual coil 6X9 I could find.

 

Thanks again. I’ll plan on using the door mid bass signal and maybe try the rear sub signal depending on results.

 

In the speaker upgrade megathread there is somewhat of a consensus on driving aftermarket subs off of the door woofer signal. It's what I've done.