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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > AUDIO/VIDEO + BLUETOOTH + Electronics/Alarm/Software > gone from sealed to ported sub - less output



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      10-18-2017, 03:42 AM   #1
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gone from sealed to ported sub - less output

Had a JL audio 10" sub in a sealed box (0.6 - litres correct for sub) in corner of boot/trunk firing across said boot/trunk

Was great. Hit hard with sharp punch bass all the way from 60hz down its natural roll off hz (allegedly 20-30hz). Played rap music with long n low bass notes and punched for higher hz dance music.


Swapped out the sealed for a ported box for space spacing (moulded fibreglass 1.2 ish litre ported box - correct according to Jl website- sitting in the same corner but over the wheel well)

Seems to be holes in the bass. If i play something like bass xtreme cd with long low hz notes its there a plenty. But a lot of the higher more dance music bass tracks i used to play with the sealed sub just seems completely absent/quiet. Gonna run some test tones with a microphone later to check db outputs across the freq range but,

Wondering if because its ported and the port is effectively at the top right hand corner of the box aimed at the small area above the wheel instead of firing across the boot whether this has any impact on bass performance or does it not matter where the port physically is? Only the length of port?


(Nb. measure the ported box and its roughly around 1.2 litres which is the correct ish volume for the sub in a ported box according to JL. As box appears to be tuned for 30hz, i have high pass xover subsonic filter set at 30hz with 18db and LP set to 55Hz 24db cut). Ps same amp for sub used at same outupt level of 300w rms (multimeter measured level).
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Last edited by sparkymarky; 10-18-2017 at 03:52 AM.
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      10-18-2017, 04:01 AM   #2
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Excuse the boot floor - in need of a hoover and clean!



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      10-18-2017, 04:07 AM   #3
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Note: sub cone seemed to move physically more in the sealed - less movt in the ported box. Not sure if this is correct or not.
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      10-18-2017, 07:00 AM   #4
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Ps sub was in phase in this test. Not swapped it to out of phase yet.
Crossover at 20 to 55hz on sub, underseats = 70hz to 200hz ish, mids/tweets = 200 upwards.
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      10-18-2017, 10:01 PM   #5
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The physical location of the port makes no difference.
It looks to me like phase cancellations with the output from your main speakers. You need to play around with phase & polarity.
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      10-20-2017, 05:40 PM   #6
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Is the port the correct length? Also, putting bends in a port can change the output. I would go back to sealed.
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      10-20-2017, 06:36 PM   #7
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I agree. sealed is much better - it may have a bit less output below resonance but it has 1/2 the phase shift and much less group delay, meaning it integrates much better with the main speakers and with the internal car boundaries.
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      10-22-2017, 07:19 PM   #8
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Sealed are known for having better frequency response as compared to ported. I think the holes you describe are an expected result.

As an example look at this overlay which shows much higher peaks in a ported enclosure

http://vseriesforums.com/forums/inde...&attach_id=403
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