qmantran

I've had a single sub (Image Dynamics IDMAX v3 12") and amp (JL Audio JX1000/1) installed in the car for 7 years now. Recently the voice coils on my sub shorted out, so I swapped it for a JL Audio 12" W3v3-4.

In the past I tapped into pins 23, 24, 25, 26 for RCA inputs going into my amp.



Now that I have a JL 12w3, I noticed the bass is almost non existent when the volume is under 50%.

I have adjusted the gain on my JL Audio amplifier using both a volt meter and oscilloscope method. First I used the manual which says to use a meter with a target voltage of 44.7vAC. Turned the headunit bass/treble to 0 and set headunit volume to 80%.

Wasn't impressed with the bass output so I tried it using the oscilloscope method and adjusted the gain until I could visually see clipping occur on the display. Still not impressed with the bass output.

Majority of the bass seems to only be heard when the volume is in the 60-80% volume range. Even with the volume set to 70-80% the bass provided at-times does not feel/sound all that impressive and I feel like there is definitely more left on the table.

I am suspecting it's because pins 23 thru 26 is meant for speakers, therefore the bass signals on these channels are low/weak.

I plan to re-wire the system to incorporate a L2Ci device to my setup and thought about getting signal from pins 16 and 17 which are factory pre-amp subwoofer specific wires.




The youtube videos I've watched regarding L2Ci installs from these youtube channels "Car Audio Fabrication" "AudioControl" and "Boost & Shutter" all briefly mention how important it is to tap into subwoofer specific outputs if you are only trying to power a sub to ensure you are getting the correct signals for the aftermarket sub.

I am thinking this may remedy my concern regarding the bass not being very impressive for a $450 subwoofer.

Can someone tell me if using pins 16 and 17 for pre amp sub would be OK?

I've been using pins 23 thru 26 for 7 years and now I'm wondering if pins 16 & 17 would be better.

beefychicken

Since the only thing that changed was the sub, it is possible that the amp is not putting out enough power to drive the new sub or there is an impedance mismatch between the new sub and exisitng amp.
Just a thought since i ran into this recently when i replaced my sub. I returned the one i bought and installed the original. I figured it was because i am running a low powered system, When i built it, i was just looking to fill in the low freq gaps of the Bose system, not trying to blow out the tail lights : )

13_SkylineSedan

Here's how I understand the Bose rig - and I could be wrong. There are four line-level audio signals from the head unit to the stock amp; front L/R (pins 33 through 36) and rear L/R (23 through 28). Those are all line level full-range signals.

Pins 16/17 are a MONO, line level, LOW-PASS audio output sent to the stock Bose rear deck sub, which had its own small amp.

The way you have it wired, 23-, 24+ and 25-, 26+ to the RCA inputs of your 1000/1D should be the best way to do it. Be sure you've got the polarity correct on those two cables they could cancel each other out. (Unpluging one input would let you know if that was an issue).

Importantly, the way you've wired it and the way the stock Bose sub worked is that the sub signal is only pulled from the rear speaker inputs. So if you've got the head unit's "fade" control set all the way forward to the front doors there will be no sub signal.

The only difference you would achieve by tapping pins 16+, 17- instead of 23 through 26 is that it would be a mono low-pass signal going to your amp. I think you're better off running it as you have it so YOU can choose the filter frequency and bass boost at the amp to suit your taste. That Bose sub output was set up for their stock unit so I'm not sure how the signal is being processed.

Of course as beefychicken mentioned, if it all worked fine before and you've only changed one component, better look closely at that piece...

qmantran

Well I went ahead and re-wired the sub. I used posi-taps in the past so it was easy work removing the 4 connections.

My fader setting has always been set to default.

I've read so much conflicting information regarding tapping into the rear speaker inputs. Some say it's full range, others say it's less focused on bass notes and tapping into the front speakers will provide more bass compared to the rears.

I asked crutchfield about tapping into speaker wires vs the factory subwoofer wires when it comes to getting signal for a dedicated amp/sub combo. They replied back stating that tapping into the factory sub wires would always be best for this case.

So I'm now getting signal from the factory sub connection. On the RCA cable I twisted both + together and both grounds together and used the posi-tap to make the connection. I left the factory sub connection unplugged, so it's no longer in-use. Only my 12" w3 is being driven.

The difference is NIGHT AND DAY. Now the bass hits exactly how i was hoping it would. I compared the gain dial on my amp to see how far I had to turn it until I got clipping on the o-scope.

When tapped into the speaker wires I had to turn the gain up a bit before the o-scope showed clipping.

When tapped into the sub wires I did not have to turn the gain **** up as much until clipping occurred.

If anyone in the future is wondering if you should tap into the rear speakers (pin 23 thru 26) or factory subwoofer (i did my connection at the connector going to the tiny amp under the factory sub, it's a small connector with only 5 or 6 wires total going into it) definitely tap into the sub wire for signal.

I can't believe I was using the rear speaker wires for signal for the last 7 years. So much bass is still left on the table when using the speaker wires. Going straight to the sub allows the aftermarket sub to work to it's full potential.

It's crazy to think that there are thousands of people out there that are probably running their aftermarket subs getting signal from the rear speakers all because of a DIY post on here from 2015 or 2016. I was one of those people. Hopefully someone else finds this helpful.

Also if you are making the change, like I did, make sure you turn your gain back down to 0 before testing the sub with the new connection. The sub wires seem to provide more voltage compared to the speaker wires, therefore your gain setting you were using will be too high and will require re-adjusting again.

I also did not use the L2Ci module. Just straight to my jl audio jx1000 amp, no line out converters.

13_SkylineSedan

Hey thanks for the great report. Glad you found the best way to wire your rig so you got the low-end you were hoping for. I have just a couple questions...

When you talk about "speaker wires" you don't mean the "outputs" of the Bose amp right? Like pins 1-6, 14/9, 18/19 and 29-32 which are the actual speaker outputs from the amp? You're talking about 23-26, 33-36 and most importantly 16&17 which are low-level signals, right? All except 16/17 are listed as "inputs" so they are the low-level signals from the head unit. 16/17 is listed as an "output" but it's the signal from the main Bose amp to the OEM sub amp - so that's still "line level" and not a "speaker" level, I guess.

And that's the one you tapped right? And you tied the two RCA connectors to your amp together so that signal was going into both RCA jacks?

One more experiment if you have a minute... I was always under the impression that the Bose amp's OEM sub was only working with the rear speaker channels (which is why I thought those was the logical signals to tap). But would you try using your head-unit's "Fade" control to move the sound all the way to the front door speakers - and then see if the sub is still pumping?

Excellent work!

qmantran

For clarity, when I mention "speaker wires" I'm referring to the pre-amp signal wires. In my scenario previously I had tapped into the "Rear Door Speakers" which are located on connector B41. There are 2 brown colored connectors of different sizes going into the factory BOSE amplifier. Connector B41 is the bigger of the two. It's located on the right when you are facing it.

• Pin 23 - Sky Blue - Rear LH -
• Pin 24 - Violet - Rear LH +
• Pin 25 - Yellow - Rear RH -
• Pin 26 - Brown - Rear RH +

These connections turned into RCA plugs that go straight into the amplifier L and R inputs. I do not recommend tapping into these.

After I re-wired the sub, I actually used connector B46. This is also a brown color connector, however it plugs into the factory BOSE subwoofer amplifier which is located in the middle of the rear dash (directly underneath the factory mounted rear subwoofer). Keep in mind that my car is a Sedan. I do not believe the Coupe models have a subwoofer mounted in the middle of the rear dash. I think the Coupes have 2 speakers mounted on the Left and Right side of the rear dash instead.

• Pin 1 - Violet - Subwoofer -
• Pin 2 - Sky Blue - Subwoofer +

I tied the two positive RCA wires together and tapped into Pin 2. The two negative RCA wires were twisted together and tapped into Pin 1.

The factory subwoofer has been left unplugged.

I will report back to you regarding the fade control setting.

qmantran

To answer your question about setting the "Fader" to full front with the factory subwoofer unplugged, the aftermarket subwoofer still works. I only tested it for a minute. With the trunk open, I could still see the subwoofer was moving with the bass.

I couldn't tell you exactly how much the bass output was reduced, but it was still enough to make the rear view mirror assembly vibrate with the volume set to 70%. The factory door and rear dash subwoofers never produced enough bass to cause the rear view mirror assembly to vibrate.

13_SkylineSedan

Thanks for the test and for clarifying which pins you worked with. That's interesting, so it seems the main Bose amp derives the sub signal from all 4 channels - which it should, but I didn't think it did. That's good to know. And we're glad you've got your low-end back. Strong work.