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6 Posts
Discussion Starter · #1 · (Edited)

Hi Guys,
I am looking to properly setup my JBL MS-8 to the best of my ability.

Sorry for my long first post, but wanted to provide as much info as I had available to me to get settings recommendations.

I need to configure the crossover settings on my JBL MS-8 before doing the timing and delays using the headset microphone. So I was wondering, using the data below, what you audio pros would recommend I set the crossover frequencies and slopes to during the MS-8 setup. Or any other settings I should look at. I know it won't be perfect without measurement tools, just looking for a good starting point, or what settings you would use 9/10 times given the situation.

I am mainly just confused, what to set the MS-8 crossover network settings for the front and rear (sides) speakers as the speakers are connected to their own crossovers, so to me it is a double crossover. Just don't want to cut off too much of the signal or mess up the phase using the wrong slopes.

Also when tuning the amp gains, can I set them as I normally would with a multimeter to get best output or do I have to under compensate for the center channel not being amped and will be directly connected to the output on the MS-8? Just don't want the center to sound washed out.

Thanks for any recommendations / suggestions you could provide. I just want the best suggestions to get great sound, doesn't have to be perfect. I do not own an oscilloscope, but I do have a fluke multimeter to set amplifier gains and such using various test sine waves.

Sound Source:

2014 Ford Fusion Titanium AWD 2.0L
Microsoft Sync System w/ Sony DSP (Deactivated)

Note: Sony DSP Disabled/Unplugged, Ford sound processing bypassed
Audio Control Module - Reprogrammed using Ford IDS As-Built Data so vehicle doesn't rely on factory amp and no longer outputs high level audio. Now outputs clean low level output, (not sure of output voltage at max volume...), instead of processed audio to reprocess again by MS-8.

Front and Rear (In Front and Rear Doors - Two Sets):
Polk SR5250 (2-way) - 5-1/4" - Connected to Kicker SX700.4 from MS-8 RCA

Using Polk Crossovers - Connected to amp in 1-way setup.
MS-8 --> Amp --> Polk Crossover --> Woofer/Tweeter (Separate Outputs)

Continuous Power Handling: 50-100 Watts
Peak Power Handling: 200 Watts
Impedance (Nominal):4 Ohms
Frequency Response (+/-3dB): 60 Hz - 30 kHz (30,000 Hz)
Sensitivity (2.83V): 89 dB
Crossover Frequency: 4600 Hz (2-way external Zobel crossover network including Mylar Film Capacitors and Air-Core Inductors)
Driver Crossover Slope (Low Pass): 2nd Order, 12 dB/Octave
Tweeter Crossover Slope (High Pass): 3rd Order, 18 dB/Octave
Tweeter Attenuation Level Settings: +2 dB, 0 dB, -1.5 dB, -3 dB
22mm Ring Radiator - Tweeter
Aerated Polypropylene / Butyl Rubber - Woofer w/Phase Plug

Front Center Speaker (Connected directly to MS-8 Output (Internal Amp)):
Kicker 41KSC354 3-1/2" (Tweeter 1/2")

Impedance: 4-Ohm
RMS: 2-50 Watts
Sensitivity: 88 dB
Frequency Response: 80Hz-20kHz
Tweeter: Neodymium/Silk
Woofer: Polypropylene

Subwoofer - Vented (In Trunk - Pointed towards vehicle tail, not cabin):
Kicker 12" Solo-Baric L7 (2007) 04VS12L74 - Connected to Kicker SX650.1 from MS-8 RCA - 2-Ohm

Power Handling (RMS): 750 Watts (w/25Hz, 24dB/octave subsonic filter), 400 Watts (without subsonic filter)
Frequency Response: 24-100Hz
Two 4-Ohm Voice Coils - Parallel Wiring (2-Ohm Final Impedance)
Sensitivity: 87.4 dB

Digital Amplifiers (Built-in DSP/Crossovers currently disabled):
Kicker SX700.4

RMS @ 13.8V (Input Power): 82x4 Watts 4-Ohm (2 Separate Internal Amps)
Frequency Response: 20Hz - 20kHz
SNR: >100 dB
Input Sensitivity: 62.5mV-16V

Kicker SX650.1 (Class D)
RMS @ 13.8V (Input Power): 325 Watts 4-Ohm
RMS @ 13.8V (Input Power): 650 Watts 2-Ohm
Frequency Response: 20Hz - 200Hz
SNR: >98 dB
Input Sensitivity: 62.5mV-16V

116 Posts
The crossovers that came with the speakers are used between the midrange and tweeter. The MS8 will crossover the speakers between the subwoofer and midrange.

Try setting the front/sub crossover point to 100hz, sides to 100 hz, and center to 200 hz. That should be a good starting point based on the size of the midranges.

Use 24db/octave slopes all around.

957 Posts
I have a similar setup in terms of speakers and sizing.. I had a lot of issues using certain crossover points and speaker setups, so I'll tell you what worked..

May be different for you, but I had a huge issue with a 3.5inch center channel with the ms8.. If I tried to cross over at 300hz 24db/octave, it would completely destroy my midbass. It EQ'ed every speaker in the car to sound like a 3.5, despite them being crossed over much lower. Not sure why it tries to level match so much below the crossover point, but I just know I tried probably 50 times before I "solved it"..

I'd suggest crossing the 3.5 over at 500hz, that seemed to fix my midbass issues, 500hz 24db slope and the midbass isnt' massively cut by the auto EQ.

For the rest of your xover points, I'd do other mids around 100hz. If your using the passives that came with the speakers, there is a "different" setting you can try, that worked best for me.

Tell the system during setup there is NO sub in the car. Then choose 2 way for your fronts. The sub will be the bottom half of your 2 way. So pick a hpf appropriate for your subwoofer, probably 20-25hz. Then it'll ask for your lpf, which will be 100hz.

The advantage to his is 2 fold. One it will time align the sub, second, it will sometimes give a more accurate calibration.

I know whenever I choose subwoofer, no matter how gains are set my bass is boomy. Having it setup where it EQ's the sub like a front speaker, it does a GREAT job.

Anyways, feel free to start by trying more standard numbers.. 300hz for you 3.5, 80-100hz for the fronts, and tell the ms8 you have a sub.. If it works fine for you that way, go with it..

Oh lastly, i would level match the rest of your speakers to your center before it calibrates. Seems the closer you start to a "good" tune, the better the ms8 can do. -35 will likely be a good volume to level match everything when doing sweeps.

6 Posts
Discussion Starter · #4 · (Edited)
Oh lastly, i would level match the rest of your speakers to your center before it calibrates. Seems the closer you start to a "good" tune, the better the ms8 can do. -35 will likely be a good volume to level match everything when doing sweeps.
Thanks T3mpest for your detailed response, that is a lot of good information... and to billw.

What would the best way to level match my amplifiers with the MS-8 be? Would this be lowering the gains on the speaker amplifiers to get in the dB range of the center channel? Should I measure the output of the MS-8 Center High Level with a DMM? Just curious how this would be done.

As far as setting the gains properly on my two Kicker amplifiers, correct me if I made any mistakes here:

So for the Kicker SX700.4 its total output (RMS) is: 82 Watts x 4 Channels @ 4-Ohms. However this amplifier has basically two separate amps inside of it. So it is really two 82 Watts x 2 Channels @ 4-Ohms as there are two separate gain controls.

So if math serves me right: 82 Watts RMS x4 Channels=328 x 4-Ohms = 1312 ... Divide 1312 in half to account for the two separate internal amps = 656. Then take the square root of 656 which = 25.612 Volts AC..... So I should be looking for this 25.612 Volts AC using a DMM with no speakers connected with a 100Hz Uncompressed Sine wave playing on repeat on the cars CD Player while playing at 75% of max volume?

Similar for my Kicker SX650.1 Class D Sub Amp:
RMS: 650x1 @ 2-Ohms... 650x2=1300.... Square root of 1300 = 36.055 Volts AC. Do this with a 60Hz Uncompressed Sine Wave measured with the DMM?

Did I make any mistakes?

The JBL MS-8 is 18 Watts RMS x 8 Channels @ 4-Ohms.... 18x8=144... 144x4=576.... SQ Root of 576 = 24 Volts AC

Should I try to get my Kicker SX700.4 Speaker amp to the same 24 Volts AC that the JBL MS-8 should be putting out? Or should I keep the kicker amp at its calculated 25.6 Volts AC? I know the numbers are pretty darn close.

Thanks again for anyone who wants to chime in on this...
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