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How to improve a Large Ported enclosure transient response?
How to improve a Large Ported enclosure transient response?
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Old 24th March 2015, 03:39 PM   #1
dannyjmf is offline dannyjmf  Malaysia
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Default How to improve a Large Ported enclosure transient response?

I just yesterday finished my giant 12inch subwoofer project. The specs are as below:

Driver T.s parameter

Model: Jaudio 2100 12Y (12inch subwoofer driver - rare stuff from China)

Parameters were measured - I dont know how accurate yep
Qts: 0.512
Qms: 1.77
Qes: 0.720

Fs: 38.5 Hz
Vas: 42L
Power handling (Rms): 200W
Nominal Impedance: 8ohms

I here attach few photos and a graph of simulated response. Currently the sub is in a giant 75L box with a 4inch diameter PVC pipe with a length of 9inch tuned to 32Hz. This subwoofer is capable of very low frequencies tested from todays listening session. Bass is fairly thumping with no sign of over excursion stress. But as for the transient response i am not really satisfied. The bass sound a little bit delayed (somewhat) as it somewhat unable to keep up with the midbass from my mains ...

Any suggestions can be given to improve a ported enclosure transient response besides adding damping / bracing into the box? Currently inside the box has some foam damping lining on few sides of the enclosure (plan to add lining to the whole box but didnt order enough ... will do it once i receive the extra lining) ...
Attached Images
File Type: png sub response actual.png (127.1 KB, 384 views)
File Type: jpg 10922720_785293464859949_3082571916804611257_n.jpg (34.1 KB, 380 views)
File Type: jpg complete 1.jpg (99.3 KB, 382 views)
File Type: jpg complete 2.jpg (51.8 KB, 378 views)
File Type: jpg 8991_779390695450226_2514501530343834867_n.jpg (32.9 KB, 374 views)
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Old 24th March 2015, 03:58 PM   #2
richie00boy is offline richie00boy  United Kingdom
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How to improve a Large Ported enclosure transient response?
Because you have some bass lift it is causing boom and slowness to the sound. Your crossover to your main speakers may also be a factor.

If you cannot make a longer port then I suggest you to lightly stuff the box with polyester wadding used for pillow and bed duvets.
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Old 24th March 2015, 04:06 PM   #3
dannyjmf is offline dannyjmf  Malaysia
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Besides stuffing ... is there anyway electronically (equalizers, phase controllers, delay units, filters) can tackle this transient response issue? Currently i am using this (ready made subwoofer controller that has low pass ... subsonic filter ... and bass boost ... )
Attached Images
File Type: jpg controller.jpg (50.6 KB, 82 views)

Last edited by dannyjmf; 24th March 2015 at 04:08 PM.
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Old 24th March 2015, 04:34 PM   #4
papasteack is offline papasteack  France
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Amp used ? Crossover frequencies ? Crossover slope ? Main speaker ? Re, Le, BL, Sd ?

Low frequencies are slow. It's not "transient response" problem. Group delay, maybe, but even big group delay problem is not such a problem for ear if crossover is done right (the biggest deal). And going such low (<50hz) you have to deal with big acoustic room problems wich will cause big dips in frequencie response, whatever (or near...) you can do with you speaker box.
Richie by advising stuffing/tweaking port, suspect port noise.
Do you have a mic ?
Your ear cannot detect by themselves transient problem. What a sub by itself sound, is pretty awful, even the best of subwoofers. (not talking about woofer)
And transient problem, are in fact conjonction of phase (ie. delay) and/or eq problem. Often, sub problem are crossover problems. And crossover problem, are often due to crossing speaker in frequencies regions where they're not at all linear. And such 12" car speaker are really probably not linear at all, having big inductance, the "Le" thiele parameter, playing as a filter. So you problably cross your sub in a frequencie region where response is "sloppy". And ear don't like large dips in frequency response.

Try to find a not too bad mic. Do 4 measurement with Room Eq Wizard your box : at 1 meter of your sub, really near your 12" speaker cone, inside the vent, and your main speakers separate. Post the result here. So we should be able to work seriously.
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Old 24th March 2015, 04:58 PM   #5
dannyjmf is offline dannyjmf  Malaysia
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currently using this amp for subwoofer duty ... TDA8950 configured in BTL ... it is a ready made kit purchased ... the crossover slopes i am not really sure because it was purchased ready made ... Will get a mic this thursday (i do own a mic but it was broken ... !!!) ... BTW where i can download the Room Eq Wizard software?
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File Type: jpg class d amp.jpg (22.5 KB, 61 views)
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Old 24th March 2015, 05:38 PM   #6
pcb121055 is offline pcb121055  United States
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with a QTS of 0.512, I would have expected a sealed box.
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Old 24th March 2015, 06:16 PM   #7
tonitonitoni is offline tonitonitoni  Croatia
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hi i had similar problem but when active crossover was made it started sounding better. its completly wrong measurments and too large box.

some time was thinking of closing port and making decent speaker out of this , maybe you should try that also
Qts: 0.583
Qms: 4.98
Qes: 0.66
Fs: 28 Hz
Vas: unknown
Power handling (Rms): 110W
Nominal Impedance: 4ohms

white plots are closed box. while still false measurments i think it would improove
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File Type: jpg IMG_00012.jpg (106.7 KB, 59 views)
File Type: jpg Untitled.jpg (328.6 KB, 58 views)
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Old 24th March 2015, 06:18 PM   #8
Sonce is offline Sonce  Macedonia
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Quote:
Originally Posted by pcb121055 View Post
with a QTS of 0.512, I would have expected a sealed box.
+1
Box is too large. Squeeze foam inside the vent (to block it), fill the box with polyester wadding and listen - it should be much better. If very low frequencies are lacking, use bass boost.
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Old 25th March 2015, 07:08 AM   #9
GM is offline GM  United States
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Quote:
Originally Posted by dannyjmf View Post
Besides stuffing ... is there anyway electronically (equalizers, phase controllers, delay units, filters) can tackle this transient response issue?
Hmm, too small a cab tuned too high with too small/short a vent for the amp power, so it would need at least a 50 Hz hi-pass, ergo better overall to stuff the cab to lower vent mach/cab Qt, then use adjustable phase, delay to fine tune it as required if available.

GM
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Old 25th March 2015, 02:44 PM   #10
dannyjmf is offline dannyjmf  Malaysia
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Just this evening added some pillow stuffing inside the box ... the bass response has improved a little bit ... still need to work on the filter circuits and maybe to build a subwoofer equalizer and phase controller ... however after adding the pillow stuffing some of the stuffing will tend to find its way out through the port ... so how do i need to secure the stuffings?
Attached Images
File Type: jpg extra stuffing.jpg (87.7 KB, 51 views)
File Type: jpg inside out.jpg (142.6 KB, 43 views)
File Type: jpg inside.jpg (150.1 KB, 46 views)
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