Mid-bass 'hole' with SWS-8

josh · 10-24-2008, 06:39 AM

I installed a pair of SWS-8's in a stock base US system and powered the whole with an PDX-5 amp. I'm getting a significant 'mid-bass' hole around 150 Hz despite fiddling with the crossover, and the SWS-8's sound more 'boomy' than I'd like, almost like they have a resonance at 40-50 Hz. I mostly listen to jazz, classical, voice, etc where a boomy bass is a hindrance.
Has anybody else seen this? I understand that sealing the enclosure is a way to 'tighten up the bass and am wondering whether this would buy me anything. Is there a way to extend the freq. range of the SWS-8 upwards a bit?

Also, the rest of the system is currently stock. I'm looking at Diamond audio upgrades and am wondering whether they would extend the lower end down a bit over stock speakers.

Bye Bye GTI · 10-24-2008, 12:12 PM

I have put both of mine in but havent gotten the PDX 5 installed yet so I can't help that much. Suggest that you post this on e90.com as more people on there have done this upgrade. I think that there is only one other person on the board that has upgraded with the sws-8's.

Your issue sounds like a crossover setting that needs to be adjusted but hard to tell over the net. Did you seal the speakers to the enclosures during install? The sws 8's are taller than the enclosures and I used weatherstripping and broke the tabs on the base of the enclosure to get a good seal.

Let us know how it goes - I am on the fence about installing a 12 in the back after hearing the sws8 just off the factory amp. Very impressed with those subs so far.

josh · 10-25-2008, 10:47 AM

The SWS-8's are sealed pretty thoroughly, with insulating tape and then a bead of silicone caulk. I made PVC plugs for the OEM connector cutouts and sealed those as well. The bottom ribs from the enclosure are removed, and speaker bottom clears the enclosure bottom. There is no dynamat in the enclosure.

Technic · 10-28-2008, 07:20 AM

You will need a multi-band EQ to adjust that "hole"; personally I don't use any aftermarket amps' built in crossovers as they commonly are not too precise in their adjustments.

Have you played specific 130 - 200Hz tones thru your system to clearly pinpoint where and how wide is this "hole"?

Quote:

Originally Posted by josh

I installed a pair of SWS-8's in a stock base US system and powered the whole with an PDX-5 amp. I'm getting a significant 'mid-bass' hole around 150 Hz despite fiddling with the crossover, and the SWS-8's sound more 'boomy' than I'd like, almost like they have a resonance at 40-50 Hz. I mostly listen to jazz, classical, voice, etc where a boomy bass is a hindrance.
Has anybody else seen this? I understand that sealing the enclosure is a way to 'tighten up the bass and am wondering whether this would buy me anything. Is there a way to extend the freq. range of the SWS-8 upwards a bit?

Also, the rest of the system is currently stock. I'm looking at Diamond audio upgrades and am wondering whether they would extend the lower end down a bit over stock speakers.

josh · 10-28-2008, 07:51 AM

I use Audacity http://audacity.sourceforge.net/ to inject a white noise sequence into the AUX port and record spectral levels on two microphones located at driver's and passenger head locations. There's about a 15 db 'hole' from 150-180 Hz.

There's also a ~4 dB 'hump' around 40 Hz which leads me to believe the SWS-8 may be underdamped in that enclosure.
If I restrict (or close off) the enclosure, should I expect the 40 Hz hump to decrease and get more energy up at higher frequencies (near 150 Hz)?

Technic · 10-28-2008, 12:29 PM

Quote:

Originally Posted by josh

I use Audacity http://audacity.sourceforge.net/ to inject a white noise sequence into the AUX port and record spectral levels on two microphones located at driver's and passenger head locations. There's about a 15 db 'hole' from 150-180 Hz.

There's also a ~4 dB 'hump' around 40 Hz which leads me to believe the SWS-8 may be underdamped in that enclosure.
If I restrict (or close off) the enclosure, should I expect the 40 Hz hump to decrease and get more energy up at higher frequencies (near 150 Hz)?

Nice...

I do not know if restricting the enclosure opening will increase the energy around 150Hz in particular, but what I do know is that these SWS-8 optimum enclosure size is 0.6 cuft in volume, which the OEM enclosure is perhaps 10% of that by volume by itself so the door sill cavities are used to create this bigger chamber. And this chamber size was measured based on the OEM woofers particular response and not the SWS-8.

So restricting the OEM enclosure could simply choke any response unless you do it in measured steps, by software simulation or simply create your own custom enclosure that has your particular set of requirements.

Or simply use an EQ and "fix" that response by force. :biggrin:

josh · 11-01-2008, 05:47 AM

I tried equalizing, but I had to compensate by over 12 dB to boost the response in the 'dead band'. This, of course, means that I can deliver only 1/16th of available amplifier power. (-12 dB = 1:16 power ratio). On top of that, I was getting THD up well over 5% near 150 Hz at 10w RMS.
So, I'd say it's a no-go, and I need to replace mid-drivers as well.
The point of this post is that just popping in SWS-8's into an otherwise stock system does not do much other than provide some 40 Hz 'thump'.

10-24-2008, 06:39 AM	#1
josh Private First Class 12 Rep 127 Posts Drives: E36 M3, 135i Join Date: Oct 2007 iTrader: (0)	Mid-bass 'hole' with SWS-8 I installed a pair of SWS-8's in a stock base US system and powered the whole with an PDX-5 amp. I'm getting a significant 'mid-bass' hole around 150 Hz despite fiddling with the crossover, and the SWS-8's sound more 'boomy' than I'd like, almost like they have a resonance at 40-50 Hz. I mostly listen to jazz, classical, voice, etc where a boomy bass is a hindrance. Has anybody else seen this? I understand that sealing the enclosure is a way to 'tighten up the bass and am wondering whether this would buy me anything. Is there a way to extend the freq. range of the SWS-8 upwards a bit? Also, the rest of the system is currently stock. I'm looking at Diamond audio upgrades and am wondering whether they would extend the lower end down a bit over stock speakers.
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10-24-2008, 12:12 PM	#2
Bye Bye GTI Private First Class 8 Rep 127 Posts Drives: 135i Join Date: May 2008 Location: Alberta iTrader: (0)	I have put both of mine in but havent gotten the PDX 5 installed yet so I can't help that much. Suggest that you post this on e90.com as more people on there have done this upgrade. I think that there is only one other person on the board that has upgraded with the sws-8's. Your issue sounds like a crossover setting that needs to be adjusted but hard to tell over the net. Did you seal the speakers to the enclosures during install? The sws 8's are taller than the enclosures and I used weatherstripping and broke the tabs on the base of the enclosure to get a good seal. Let us know how it goes - I am on the fence about installing a 12 in the back after hearing the sws8 just off the factory amp. Very impressed with those subs so far.
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10-25-2008, 10:47 AM	#3
josh Private First Class 12 Rep 127 Posts Drives: E36 M3, 135i Join Date: Oct 2007 iTrader: (0)	The SWS-8's are sealed pretty thoroughly, with insulating tape and then a bead of silicone caulk. I made PVC plugs for the OEM connector cutouts and sealed those as well. The bottom ribs from the enclosure are removed, and speaker bottom clears the enclosure bottom. There is no dynamat in the enclosure.
	Appreciate 0 Quote

10-28-2008, 07:51 AM	#5
josh Private First Class 12 Rep 127 Posts Drives: E36 M3, 135i Join Date: Oct 2007 iTrader: (0)	I use Audacity http://audacity.sourceforge.net/ to inject a white noise sequence into the AUX port and record spectral levels on two microphones located at driver's and passenger head locations. There's about a 15 db 'hole' from 150-180 Hz. There's also a ~4 dB 'hump' around 40 Hz which leads me to believe the SWS-8 may be underdamped in that enclosure. If I restrict (or close off) the enclosure, should I expect the 40 Hz hump to decrease and get more energy up at higher frequencies (near 150 Hz)?
	Appreciate 0 Quote

11-01-2008, 05:47 AM	#7
josh Private First Class 12 Rep 127 Posts Drives: E36 M3, 135i Join Date: Oct 2007 iTrader: (0)	I tried equalizing, but I had to compensate by over 12 dB to boost the response in the 'dead band'. This, of course, means that I can deliver only 1/16th of available amplifier power. (-12 dB = 1:16 power ratio). On top of that, I was getting THD up well over 5% near 150 Hz at 10w RMS. So, I'd say it's a no-go, and I need to replace mid-drivers as well. The point of this post is that just popping in SWS-8's into an otherwise stock system does not do much other than provide some 40 Hz 'thump'.
	Appreciate 0 Quote