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) ...
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) ...
Attachments
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 ... )
Attachments
Last edited:
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.
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.
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?
Attachments
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
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
Attachments
+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.
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
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?
Attachments
Hi dannyjmf,
In Post #1 you are showing the screen capture of a WinISD window, could you show the T/S parameter window that was used in WinISD?
Also, have you measured the impedance of the finished subwoofer, and do you get anything that looks like the two impedance peaks around fs that would be typical for a bass-reflex enclosure?
Regards,
In Post #1 you are showing the screen capture of a WinISD window, could you show the T/S parameter window that was used in WinISD?
Also, have you measured the impedance of the finished subwoofer, and do you get anything that looks like the two impedance peaks around fs that would be typical for a bass-reflex enclosure?
Regards,
The impedance i didnt really know the method how to measure it ... can u pls guide me how to do so ... and also here is the graph of the transfer function magnitude with the parameters of the driver ... the parameters i know they are not as accurate as it should be ... i tried the best i can to get the parameters by measuring ... parameters not provided when i bought the woofer ...
Attachments
Midbass actually is a full range 3" TangBand W3-593SG ... it runs all the way down at the lower end frequency and crossed over to the tweeter at around 3Khz ... The TangBand were housed in sealed box and their bass response were excellent ... really accurate and tight ... unlike my subwoofer ...
Historically, you roughly lined the cab with cheesecloth to create a bag to tie off to keep stuffing from getting into the driver, vent or if the cab needed a heavy stuffing density, then the cheesecloth was loosely stapled over the driver and vent if it had one.
GM
FYI, the 11.5" effective diameter is too large for a large surround 12" woofer, so what is it when you measure the outside [o.d.] and inside [i.d.] diameter of the surround, then Dd = [o.d. x i.d]^0.5
I'm guessing it will be < 10".
GM
... i am just a beginner sorry abt that Hi dannyjmf,
As GM pointed out in Post #16 the Sd is probably not correct. For a 12" driver of this type you are looking @ 470 to 500 cm^2 (or so). Try measuring from the middle of the surround side-to-side. Re looks high too. I would recommend that you measure the driver again.
Here is a good reference for measuring T/S parameters (including impedance):
Measuring Loudspeaker Driver Parameters
also:
The Subwoofer DIY Page
Regards,
As GM pointed out in Post #16 the Sd is probably not correct. For a 12" driver of this type you are looking @ 470 to 500 cm^2 (or so). Try measuring from the middle of the surround side-to-side. Re looks high too. I would recommend that you measure the driver again.
Here is a good reference for measuring T/S parameters (including impedance):
Measuring Loudspeaker Driver Parameters
also:
The Subwoofer DIY Page
Regards,
pretty much this.
in my experience, when trying to put a driver that "wants" a sealed box into ported enclosures tuned low or "low-ish" group delay becomes a major factor. If this works correctly, attached are quick plots i did with the specs you gave for the driver, green = a sealed box w/ Q of .707, purple = your design, pink = "maximally flat" ported enclosure. pretty clear what's going on with group delay
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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