CSS Quartet12XB Build - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #1 of 8 Old 11-16-13, 02:46 PM Thread Starter
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Jeff
 
Join Date: Oct 2013
Location: Regina, SK
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CSS Quartet12XB Build

Hello,

I was hoping to get some input regarding my latest subwoofer build. It is nothing to fancy, just the CSS Quartet12XB kit built to the recommended specifications. I finally good it all finished last night I started to listen to some of my reference scenes, the aquarium tapping scene in Finding Nemo and the grenade scene in World War Z. Both of these scenes causes to sub to bottom out, I think that is the wording, at even very low volumes. The gain on the amp is set to 1/4 and my avr has the sub channel at -6.0db. I have the passive radiators tuned with the recommended amount of washers, 18, and I tried adding 2 and removing 2 washers as well. Something definitely isn't right and I hope its not a bad woofer. I looking for any recommendations on how to troubleshoot and possible causes for the issue. I've attached a video of the sub bottoming out in Finding Nemo to illustrate the problem.

Let me know if the pictures and video aren't accessible. Thank you.

https://www.dropbox.com/s/lm4snxg8bb...2010.57.52.jpg
https://www.dropbox.com/s/op4q0p2faw...2012.06.51.jpg
https://www.dropbox.com/s/ongeb38qoc...2010.59.22.jpg
https://www.dropbox.com/s/w0e24osihz...2021.56.43.jpg

The the video
https://www.dropbox.com/s/qlwf0pj9s6...2019.15.06.mp4
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post #2 of 8 Old 11-16-13, 04:15 PM
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Re: CSS Quartet12XB Build

The "bad" sound does not sound like the driver bottoming to me.
The "bad" sound is NOT normal.
With the sound track from a movie, it's hard to make some audio differentiation.
I would get a test disc with single low notes 10Hz and up, record your own. You can down load single freqs. on the internet. Play the single freqs. looking for the particular one that causes the distortion. That way it's easier to isolate the problem.
I would look at your mounting of the driver and PRs PLUS the Bash amp. Look, feel, sniff, for air leaks and loose screws and/or box joints. That'll best be done with single freqs. down low at higher volumes.
As a last resort, I'd pull the driver and (carefully!) load it with some low notes in free air making sure that the surround, leads, spider, and voice coil are all intact and move without interference. Maybe some glued joints have separated. With the PRs you MIGHT be able to hear either one of THEM making the noise. Check both of the PRs for loose parts too especially your added tuning weights.
Lastly, the Bash amp may be hitting it's limit and going into protection making that braaaaat sound.
Nice work on the box by the way!
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post #3 of 8 Old 11-16-13, 04:42 PM
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Bob
 
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Re: CSS Quartet12XB Build

Very nice work on the cabinet. Please do check for air leaks, etc as was suggested. Not sure if there are different connection option on the BASH to consider.

In any case we stand behind our products and will look after you.

Bob
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post #4 of 8 Old 11-16-13, 08:59 PM Thread Starter
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Jeff
 
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A bit of an update. It seems like the culprit is indeed an air leak. I wasn't able to determine where exactly but I have a few ideas. I glued up the holes where the cabinet feet go through the bottom of the enclosure. This was the last thing that I did on the box and I didn't recall hearing the noise when I briefly tested the sub before installing the cabinet feet. I think this is the most likely spot for a leak. While I had the passive radiators out I ran a bead of silicon around the openings before I reinstalled them. There was no foam gasket around the PRs, just the rubber surround on the PR itself. The silicon is just some added insurance. I am just waiting for the silicon to cure before I test the sub again.

If it still seems like it is leaking after I test it I will take off the plate amp and remove the foam gasket and use silicon instead.

I feel that the driver is sealed up good and tight with no chance of leaking. I used lots of wood glue and all of my joints are solid so I doubt the box itself is leaking. I will update again after I test it. Thanks for the help so far.
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post #5 of 8 Old 11-17-13, 01:16 AM Thread Starter
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Jeff
 
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Well my issue seems to be solved for the moment. How it got fixed exactly, I'm not so sure.

I ended up putting some silicon around the amp opening so there is good seal there. Both PRs appear to be sealed up as well. I played some test tones and felt for air but could not find anything. The sound was still present at frequencies 35hz and below.

When I pushed in the cone I could see the PRs extend and they very slowly retracted when I held the cone pressed it. If there was a leak it must be tiny.

I decided to play with some settings on my AVR. I turned off Audssey EQ and ran some more test tones. It seemed like a slight improvement. Then I tried raising the gain on the sub amp from 1/4 to 1/2 and lowered the channel level on my AVR. No difference with the test tones. Was just about ready to give up for the night but I decided to turn the Audssey EQ back on. Played some more test tones and my reference scenes, everything is perfect. Why I have no idea. For whatever reason my AVR was sending a clipped signal. So it appears the all is good with the sub. The only bad part is that I scratched the paint working on it tonight, oh well.
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post #6 of 8 Old 11-17-13, 11:45 AM
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Re: CSS Quartet12XB Build

Quote:
I decided to turn the Audssey EQ back on. Played some more test tones and my reference scenes, everything is perfect. Why I have no idea. For whatever reason my AVR was sending a clipped signal.
Interesting. I will definitely remember this the next time someone needs help troubleshooting a sub. Thanks for posting.

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post #7 of 8 Old 11-17-13, 01:00 PM Thread Starter
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Jeff
 
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Audessey EQ seems to be the culprit. I think it is trying to boost the low end frequencies and causing a clipped signal to be sent or over driving the amp. I read that Audessey will boost the low frequencies because the human ear perceives them as being quieter and Audessy tries to adjust the volume to be consistent at all frequencies. I will leave it turned off for now.

I am considering moving the sub to the corner of my room to help reduce some strain on the amp/sub. I think I might need some better sub EQing though because I've always found my sub's to be way too boomy when corner loading in this room. My calibrated mic should be here this week and then I can find the best location for the sub. Thanks for the help everyone.

Edit: Yep that was the problem. Calibration mic was sitting in a null, Audyssey was applying the maximum boost to correct for it causing it to distort. Moved it to the corner of the room and reran Audyssey. Everything sounds great now, I'm really impressed with the sub now.

Last edited by Jdiesel87; 11-17-13 at 05:55 PM.
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post #8 of 8 Old 02-21-14, 03:57 PM Thread Starter
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Jeff
 
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Re: CSS Quartet12XB Build

It's been a while since I've given an update. I purchased a calibrated microphone and a MiniDSP to avoid having to use Audyessy which was not working for me. It was difficult to find a suitable location for the sub in my listening room because of my extra wide seating area. I ended up having nulls in one of the main listening positions when the other position was perfect. I ended up having to stick the sub back into the front corner and EQ all of the peaks out between 30hz and 70hz. The sub starts to roll off sharply at 70hz so I ended up using 70hz as a crossover point with my mains. I have plenty of headroom left in the sub but I am still considering building a second one to even out the response across all the listing positions. Hopefully adding a second sub will also help me recover some of the <20hz output that I lost by sticking in the corner.
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