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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > AUDIO/VIDEO + BLUETOOTH + Electronics/Alarm/Software > Sub cancellation issue



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      04-29-2015, 11:11 AM   #1
david in germany
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Sub cancellation issue

Ok Iam running a jl audio stealthbox in my e90 off of a Digital Designs SS1a amp wired with the technics Logic 7 harness but am having a weird cancellation issue. Anything over 50-60 hz seems cut unless I wire the subs out of phase. Has anyone else had any issues like this?

Thanks all!
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      04-29-2015, 12:24 PM   #2
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I don't know how the stealth box is mounted but I had cancellation issues with my JL sub firing inward towards the cabin through the seat pass through. I originally had it mounted facing to the rear, which increased cabin gain but gave me issues with time delay (using simple RCA patch so non-adjustable). When I faced it in towards the interior I expected that I would have some cancellation issues when wired normally, which I did, so I've been running it with the phase reversed ever since with no issues.

In my case it seemed that the sound pressure generated by the JL sub and the sound pressure generated by the stock speakers/subs were working against each other when all of the speaker cones were facing inward.
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      04-29-2015, 12:44 PM   #3
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The jl is rear facing on the stealthbox. Maybe the Logic 7 is doing something that causes the stock woofers to run out of phase.
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      04-29-2015, 09:06 PM   #4
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Quote:
Originally Posted by david in germany
The jl is rear facing on the stealthbox. Maybe the Logic 7 is doing something that causes the stock woofers to run out of phase.
You are probably overlapping the midbass and sub, correct? In that case reversing polarity may help, but you should also try lowering the sub amp low pass filter to around 50hz.
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      04-30-2015, 01:42 AM   #5
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Thanks, I was also going to look at bringing the Frequency up on the underseats to around 80hz or so. It will be easy to stick a passive filter inline using the technics harness.
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      04-30-2015, 02:05 AM   #6
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What are your slopes on you sub and midbass crossovers?
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      04-30-2015, 07:45 AM   #7
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Quote:
Originally Posted by david in germany View Post
Thanks, I was also going to look at bringing the Frequency up on the underseats to around 80hz or so. It will be easy to stick a passive filter inline using the technics harness.
Better to amp them. You'll be very surprised how good they sound once you add the power, plus you'll have a "free" HPF which works better than an in-line filter. If the filter is 24dB/oct, I'd recommend a 55Hz crossover point, or 80Hz with 12dB/oct.
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      04-30-2015, 08:51 AM   #8
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Quote:
Originally Posted by taibanl View Post
What are your slopes on you sub and midbass crossovers?
All stock.

Quote:
Originally Posted by kaigoss69 View Post
Better to amp them. You'll be very surprised how good they sound once you add the power, plus you'll have a "free" HPF which works better than an in-line filter. If the filter is 24dB/oct, I'd recommend a 55Hz crossover point, or 80Hz with 12dB/oct.
I know the L7 underseats are very capable but I really wanted to keep them on the stock amp. I think I have a 80hz 12db passive pair in my stash that I can connect up.
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      05-01-2015, 10:48 AM   #9
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I dropped the cover frequency for the sub and I cleared up a bit of the cancelation. I found that I have a set of 12db 80hz Passives that I will try out but I need to first see if I can find a molex plug that will match up with the technics harness plug so I don't need to cut mine.
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      05-01-2015, 12:38 PM   #10
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I haven't tried every combination but I have found better results with 90 degrees out of phase (12db mid bass & 24db sub bass slope) than in phase (24/24). Kaigoiss I think runs 180 degrees out of phase (12/12)
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