My first JL TuN

[OldFatBald]

This is my first experience setting up a DSP and also setting up my first car audio system in about 25 years.

I am setting up my buddy’s 56 Ford F100 with the following;

Some aftermarket HU – I don’t remember what brand/model
(1) TwK-88

Speakers:
(2) sets of C3-570s
One set of the speakers will be full active
One set of the speakers will run through the JL passive X-overs as the TwK doesn’t have enough outputs

Amps:
(1) JL XD400/4 driving the door’s Mids & Tweets full active
(1) JL XD700/5 bridged driving a pair of C3-570s run through the JL passive X-over & (1) small 8” Kicker sub



Attachment 7658

[OldFatBald]

Not too much to show yet as I am setting up the TuN on my desktop and will transfer it to the TwK after I finish up a little more wiring, well and mounting the amps!

[JCsAudio]

Unfortunately those tweeters cannot cross very low and JL Audio does not publish the specifications. Normally you would cross the tweeter 1.5 to 2 times the fs of the tweeter but since JL recommends a HP at 4K 12 db then 3k at 24 db Linkwitz Riley filter might be ok. The lower you can LP the woofer the better it is because you stay out of the woofers beaming frequencies so that the reflected sounds are as close to the direct sound as possible. This is why most three ways have an advantage over a two way in a car. Set up your DSP and crossovers like this:

Check speaker polarity and make sure it’s right.
Measure distance from center of your head at listening position and input this into the DSP and never touch it again.

Set speaker crossovers as follows using the advanced mode and parametric filters:
C3 tweeters HP 3k LR4 which is short for HP 3000 Hz 24db Linkwitz Riley.
‘Mids HP 80 db LR4 and LP 3K LR4
Subwoofer LP 60 db LR4 so that the acoustic crossover is actually at 80 Hz and not higher. Set the level of the subwoofer at 15 to 20 db above the midwoofer.

If this is a ported subwoofer than you may want to set a HP filter 1/2 octave below the tuning frequency and with a 24 db butterworth filter but generally 20 Hz is good if you don’t know it.

Download REW and measure each driver with a UMIK microphone and then EQ each driver to your house curve. Measure the left side all together and make final adjustments against your house curve. Measure the right side all together and make the right side within 2 db or less of the left side so they match. Measure everything together and make any final adjustments against your house curve and personal preferences by ear.

Only use 24 db Linkwitz Riley filters because with these the acoustic response will more closely match the electrical response compared to others.

That is a good process in a nutshell. BTW I have several JL TwK88 DSP’s and they are solid DSP’s.

[OldFatBald]

JC, I was taught to set the tweeter X-over at 1.5 to 2 times the Fs but as you said, JL doesn't publish that data (which I find strange).

I did read on JL's site for the C3-100ct (1" tweeter) under the "Overview" tab;
"Inline 12 dB / octave high-pass filters with tweeter protectors are included with this kit. The C3-100ct is designed to operate above 4 kHz with a minimum high-pass slope of 12 dB / octave."

So what I did is send JL tech a question if they could provide the Fs (no was the answer) but below was also JL tech's reply; (which is why I set the x-overs where I did)

Hello, for the C3 speakers I would suggest a high pass no lower than 4,000 Hz at 24 db slope for the C3-100 tweeter.
Then bandpass the midrangefrom 4,000 Hz down to 80 Hz.

For the passive speakers I would high pass them at80 Hz at 24 db slope. Then low pass subs at 80 hz at 24 db slope. I hope thishelps.

[JCsAudio]

JL won’t share a lot of information that other manufacturers do which is a red flag that they are hiding something to me. If the HP on the passive is 12 db At 4K than an active HP of 3k KR4 might work out. Lower would be better and you can experiment while listening for distortion in the tweeter but I’m guessing its not going to be possible with that tweeter. A 3k or higher crossover for a two way is going to be tough to tune depending on actual speaker locations. You can certainly HP the mid at 80 and the sub LP 80 but if you do and you run the subwoofer 15-20 db more than the midwoofer than the actual acoustic crossover will be much higher than 80 Hz and you may have phase issues too which will show up on the RTA as a dip on the response after the crossover point. If you run the sub LP 1/2 octave lower than the HP of the midwoofer than your acoustic crossover will be closer to 80 which is what a lot of enthusiasts prefer.

[Bajbass]

So use the auto eq in rew to match the house curve or its better to just manually adjust the eq?

[JCsAudio]

The Auto EQ in REW works well to get you close and is great for learning the program but if you can do it manually using wider (lower #) Q's than you will use less EQ bands to get the same results. I used to use REW auto EQ a lot in the beginning and got great results so don't be afraid to use it. I've noticed that REW auto EQ likes to use a lot of Q's in the 5 range for some reason. You can also use auto EQ and then manually adjust the results while watching what happens to the predicted response in the EQ tab which is a nice feature of REW and helps beginners learn how the response is affected.

[Bajbass]

Ok thanks one other thing I see some people move the Mic around their face to take measurements is this more accurate or you prefer to keep the Mic stationary on the headrest?

[JCsAudio]

I've tried both methods and prefer to move the mic around my head from one ear to the other as close to my head as possible while REW averages the response. I feel like this is more representative of a persons head moving around while driving and so gives a more accurate response. I do 60 averages when measuring. Make sure you use the 90-degree calibration file and hold the mic pointing up but also slightly tilted towards the front if you can.