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Discussion Starter · #1 ·
This is my first DIY sub, and first post on the forum. After 3 weeks of messing around in the garage I came up with a decent result. Output so far seems great, but I may need some adjusment on the HPF. When testing the sub using the opening explosion in Hurt Locker and opening scene in War of the Worlds it bottomed out a few times. Not prolonged, but audible.

I think I need some guidance at this point. I modeled this using Unibox. Here are the particulars:

2.5L
Tuned to 22hz +/-
4" x 25.25" port flared on both ends
F3 of 20 hz or so

According to the modeling this will hit XMAX around 19hz. The Bash 300 comes with a stock 17.7 HPF that I thought would be sufficient to avoid XMAX. But maybe not......I was not sure if I created the HPF circuit using Bagely's circuit designer program correctly, when I imported it into Unibox. I am using the LFE input and have it crossed over at 80hz on my Marantz reciever. Here are my questions:

1. Does the LFE input bypass the 17.7 HPF on the Bash 300? If so I guess I need to used the Line Level Inputs in order to use the HPF.
2. If it does not, then it sounds as if I may need to raise the HPF. Right?

I welcome all thoughts and advice. Thanks in advance...

sdx10.JPG
 

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Nice sub build. I take it you mean the cabinet volume is 2.5 cu.ft. tuned to 22 hz. To protect the driver from bottoming out you should change the HPF to 20.4 hz with 1 db of boost in the 31 - 35 hz range. This will keep the driver within Xmax. the LFE input does not bypass the HPF.

What is the size of the room the sub is in?

What is the internal height of the cabinet?
 

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Discussion Starter · #3 ·
Nice sub build. I take it you mean the cabinet volume is 2.5 cu.ft. tuned to 22 hz. To protect the driver from bottoming out you should change the HPF to 20.4 hz with 1 db of boost in the 31 - 35 hz range. This will keep the driver within Xmax. the LFE input does not bypass the HPF.

What is the size of the room the sub is in?

What is the internal height of the cabinet?
Mike,
Thanks for the reply. Yes, I meant 2.5 cu ft. The room is 14x11x11. The internal height is 31" so I have enough clearance at the end of the port, if that is where you were going.

Ok, so guess I will be doing some modifications to the amp. So, I can either buy a soldering iron and do it myself. $30 to $50. Or I can send it out to CSS. I wonder if Meniscus Audio who I purchased the driver through might modify these? Have you modified one these? Was it difficult?

Thanks
 

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Discussion Starter · #5 ·
Hmmmm. I ran down to Radio Shack today and picked up some resistors and a soldering iron.

Made the modifications to increase the HPF to 20.4hz with 1db of boost in the 31-35hz range. Well, good news is I didn't screw it up. It still works, but my fine soldering leaves something to be desired.

Bad news is, it still seemed to bottom out during the explosion at the beginning of the Hurt Locker. The volume was no more than normal listening level. I am not sure what to think of this.....

My Outlaw Audio LFM-1 Compact which uses a Hsu 10" driver with inferior specs does not do this, even at Reference levels.

Maybe I need to contact the folks over at CSS. Any suggestions?
 

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Discussion Starter · #7 · (Edited)
First things first. You need to make sure there are no air leaks from the driver, port, and amp mounting.

The "bottoming out" may well be the amp clipping due to being over driven.
Yes, I guess your right. I am fairly certain there are no leaks, but I will check thoroughly again. This is a very demanding audio sequence but really with the increase in the HPF there should not be a problem I would think. Thanks for the reply Mike. More testing tomorrow when everyone is awake I guess.
 

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Discussion Starter · #8 ·
After going over the sub today, I did not find any leaks.

Still perturbed here. I made a dummy plate today and hooked up my Bash 250 from my Outlaw sub today. After recalibration, went through same scenes and was able to replicate it with the second amp. So not an amp issue. After putting the outlaw back together which is about a 49L enclosure, went through the same scene. The Outlaw bested my design and no distortion or mechanical noises.

Anyway, it must be my enclosure or the driver. The size is not much bigger than the Quartet 10 design so I would not think the size is the problem. Maybe some kind of air flow or resonance is throwing the cone off.

I think I need to email CSS at this point. I am willing to create another enclosure, but just don't want to waste my time if the driver has a problem.

This is frustrating...
 

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Discussion Starter · #10 ·
With the 20.4 hz HPF you are under Xmax, there must be problem somewhere. Any chance you have a SPL meter?

EDIT: It appears the Outlaw Audio LFM-1 Compact would have a HPF in the mid 20's, makes me think you have a driver problem.
I do have an SPL meter. What did you have in mind?

I plugged the port and it seemed to make things worse. I am leaning in the direction of a driver issue too.
 

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Do a frequency sweep and adjust the gain to the so the sub isn't making any noises at the low frequencies. Then use separate test tones and post the SPL at 17, 20, 25, and 30 hz measured from 3 feet.

I need to know what make and model of SPL meter you have so a correction file can be applied.

Also did you use foam tape to seal the driver to the cabinet?
 

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Discussion Starter · #12 ·
Well, I am satisfied now. After some himming and hawing I decided to return the SDX10 driver. I replaced it with a Dayton 10" Reference HF driver. I am happy I did.

The difference was apparent right away. In passages where the SDX10 seemed to be moving a lot without really producing an equivalent SPL and lacked any real composure, the Dayton just smoothly pumped away producing clean, low, house shaking bass without really moving whole lot.

The Dayton is well suited for my larger enclosure and seems to be the ideal drop in replacement. It may be that the CSS unit just did not like such a large ported enclosure even though the modeling indicated it would be fine. But I also think that my particular driver despite the robust appearance might have a problem and I don't know what to say about why the SDX10 driver appeared to have so much linear movement compared to the Dayton. hmmm, who knows. I really wanted the SDX10 driver to work, but it just was not in the cards in this configuration.

I did some test runs yesterday, using the War of the Worlds passage that seemed to create the problems in the SDX10 driver. Turned it to the same volume after calibration, and did not hear any problems. Smooth, un-strained bass. I could not test it completely as the wife's patience were already being tested. The Hurt Locker will have to wait until another day but I am sure it will work fine given it's performance with War of the Worlds.
 

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I have four of these subs in my HT. I know at least one of them makes the same detenation sound you are describing. The noise only happens on certin scenes and at higher volume levels (what I would call Referance level). My subs are sharing 1000 watts RMS in sealed cabinets.

This is for sure mechanical noise made by the sub itself. I would guess it the VC hitting the back plate, but I'm not driving the subs that hard, so it could be another reason?

I haven't bothered contacting CSS. But I've been tempted.
 

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Discussion Starter · #14 ·
That is interesting to hear. So I am not crazy. What size enclosure is it in! I am sure 4 of them sound awesome. It might be the case that we would never hear this anomaly during normal listening. But when you spend time and money on a project in hopes of exceeding the performance of your lesser quality sub, you can't help but be a little picky.

Thanks for commenting.
 

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I have four of these subs in my HT. I know at least one of them makes the same detenation sound you are describing. The noise only happens on certin scenes and at higher volume levels (what I would call Referance level). My subs are sharing 1000 watts RMS in sealed cabinets.

This is for sure mechanical noise made by the sub itself. I would guess it the VC hitting the back plate, but I'm not driving the subs that hard, so it could be another reason?

I haven't bothered contacting CSS. But I've been tempted.
In my experience with these drivers, I've found that they will let you know in no uncertain terms when they aren't happy. Before I put the tapped horn together with them, I had no problem running them in free air during break in at the whole 18mm Xmax rating.

But stick them in the horn, feed them with too much power, and fail to set the highpass properly? "Hello, backplate. I'm voice coil. How are ya?"
 

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My subs are in 2 cubic foot sealed cabinets ( two subs per bOx). It is a bit of a disappointment to have this issue. And its actually scary to hear when you aren't expecting it. I'm sure I will swap the subs at some point. Maybe if CSS offers a decent trade in program, I will give the a try on the next model that is produced?
 

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If it's just one driver doing it, there could be other problems with it. Why not contact CSS and see what they suggest?

I've been told the SDX10 is going to be around a while - no replacement planned for the foreseeable future.
 
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