Bedlam in Goliath: RE Audio XXX18 subwoofer build - Page 7 - AVS Forum
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DIY Speakers and Subs > Bedlam in Goliath: RE Audio XXX18 subwoofer build
NEO Dan's Avatar NEO Dan 01:36 PM 10-09-2008
I think the ECM8000 Mic used to make the .cal file hosted on the "Shack" has been regularly used to compare newer ECM8000 Mic's. I think it would have been reported if there were reason to have another .cal file made for a newer version. You should probably ask Sonnie. Please let us know what you find out.

Ricci's Avatar Ricci 10:39 PM 10-09-2008
This is a close mic of an SDX 15 in 4cu ft and there's a crossover at 200hz. The Rane isn't in this system and the amp is a different ce4000. It's rolling off at greater than 12db octave too. It's about 18db octave. The XXX was about 16db octave.








This is with the amplifier switched to an AETechron 7560 that is supposed to be flat to nearly DC. Chuck measured it at -0.2db at 10hz I think. It changed the low end response a lot and the roll off is lessened to about 14db octave from almost 18db octave.










Makes me wonder whether the CE4000 starts rolling off at 20hz. The 30hz area is weird too. the peak there was reduced significantly by switching the amps. Here is the 2 graphs overlaid on each other. You can see what I'm talking about.





Dradius's Avatar Dradius 08:14 AM 10-10-2008
Posting at 12:39 AM on a Thursday night? Were you all hopped up on pumpkin ice cream and donuts from HH or something
Ricci's Avatar Ricci 12:36 PM 10-10-2008
I burn the candle at both ends man! Go to sleep at 1:00am get up at 6am. Drink coffee. Woooh! Wash, rinse, repeat. I was down there for a bit yesterday afternoon though. I'll probably go for a bit Saturday or Sunday too.
michael hurd's Avatar michael hurd 12:53 PM 10-10-2008
Like Kyle Keating was saying that with increasing load, amps as well as speakers start to act non-linear at higher and higher levels.

Very interesting measurement Ricci!
Ricci's Avatar Ricci 02:30 PM 10-10-2008
Haven't seen you around in awhile Mike. Kyle ain't lieing.

I'm just trying to figure out why my measurements of 3 different drivers in different enclosures all show a steeper roll off than the nominal 12db octave that a sealed is supposed to roll off at...
A9X-308's Avatar A9X-308 02:51 PM 10-10-2008
Quote:
Originally Posted by Ricci View Post

Makes me wonder whether the CE4000 starts rolling off at 20hz.

You have the ability to measure it, so why not do so and make sure that's not the issue?
Ricci's Avatar Ricci 08:55 AM 10-11-2008
The only way I have to do it is to run the power output of the amp straight back into my SC input at a very low level through a rigged up cable. I'm leery of doing this because something could easily get fried in my laptop or the SC. Is there a better way?
Ilkka Rissanen's Avatar Ilkka Rissanen 09:19 AM 10-11-2008
Quote:
Originally Posted by Ricci View Post

Makes me wonder whether the CE4000 starts rolling off at 20hz. The 30hz area is weird too. the peak there was reduced significantly by switching the amps. Here is the 2 graphs overlaid on each other. You can see what I'm talking about.





That is really strange because I have measured the FR of my CE4000(s), and it's dead flat down to ~10 Hz.

Also the whole FR looks strange when comparing it to what I measured using only a little bit under 4 cu ft enclosure. Your Fb seems s lot lower? Roll-off rate is around 13 dB/oct., and I used a CE4000.


Ricci's Avatar Ricci 09:51 PM 10-11-2008
I don't know. I used a wft3 to measure the impedance of both SDX's and the XXX sealed. The SDX's had the impedence spike at 31hz. I'm measuring with the ecm8000 about 3"from the cone at a moderate level, in room. My FB appears to be at 30hz where yours is at 40. Plus there a much more drastic roll off in the upper bass, not to mention the faster low end rate. BTW I trust yours are a lot more accurate than mine.

Anybody else running SDX's that would like to get a comparison FR measurement with REW?
Ricci's Avatar Ricci 12:14 PM 10-16-2008
I guess nobody has an SDX 15 that they could get a close mic FR from?




Pics of a disassembled XXX. I had a tapping sound out of one of the drivers abruptly at about 30mm one way that was not normal. The other 3 had been driven much further and never exhibited any sound like this. I took apart the offending driver to see what was up and discovered a bit of excess glue that was contacting the pole piece. Tearing it apart wasn't too bad, but reassembly was a real bear PITA. Trying to get all 16 of the bolts into the motor to line up and then centering the coils was very frustrating. An interesting note is that at the bottom of the motor back plate where the vc would bottom if you can ever get it there, is what appears to be a peanut butter colored ring of silicone or rubber. I couldn't get a picture of it.

















































Nuance's Avatar Nuance 10:08 PM 03-07-2009
Great thread, Ricci. It took me forever to read it! Better late than never, though. I had a couple Antikythera CD's spinning to help pass the time while I read. You ever heard of them, Ricci?

Well, you've outdone yourself man! Well done sir - I love it! Now how do I convince my wife we need one just like it?
Ricci's Avatar Ricci 12:38 PM 03-08-2009
Quote:
Originally Posted by Nuance View Post

Great thread, Ricci. It took me forever to read it! Better late than never, though. I had a couple Antikythera CD's spinning to help pass the time while I read. You ever heard of them, Ricci?

Well, you've outdone yourself man! Well done sir - I love it! Now how do I convince my wife we need one just like it?

Thanks man! It's a long thread for sure. I'm still impressed by this sub.

BTW don't listen to that stuff too much. It's an aquired taste.
Warpdrv's Avatar Warpdrv 01:05 PM 03-08-2009
Ricci.....

Ya gotta update your thread with some pics of the new enclosure

Its a dam nice box if I do say so my damn self...
Nuance's Avatar Nuance 01:48 PM 03-08-2009
Quote:
Originally Posted by Ricci View Post

Thanks man! It's a long thread for sure. I'm still impressed by this sub.

BTW don't listen to that stuff too much. It's an aquired taste.

Well, we all know I have a soft spot for underground heavy metal. Thanks again for hooking me up with your CD's. You're the drummer, right?
Ricci's Avatar Ricci 01:57 PM 03-08-2009
Quote:
Originally Posted by Nuance View Post

Well, we all know I have a soft spot for underground heavy metal. Thanks again for hooking me up with your CD's. You're the drummer, right?

Yep. We're in the process of booking some gigs in the Chicago area with a possible stint up to Milwaukee as well.
Nuance's Avatar Nuance 01:58 PM 03-08-2009
Quote:
Originally Posted by Ricci View Post

Yep. We're in the process of booking some gigs in the Chicago area with a possible stint up to Milwaukee as well.

Do let me know when you'll be in the area, even if it's only Chicago. I should be able to make the trip.

Thanks bud.
Ricci's Avatar Ricci 02:35 PM 03-08-2009
Will do man. We just shipped off the art proofs and master for the new album to Discmakers Friday. That's the one I gave you that is just a burnt disc. It'll probably be early May when we get up to that area.
Ricci's Avatar Ricci 07:44 AM 03-12-2009
Here's a few pics of the box that Warpdrv made for the GTG.






Ricci's Avatar Ricci 09:36 AM 03-12-2009
I did some messing around last night with the 24" cube (6ft) XXX and ran into some interesting things. First if I push it hard it will start to rock the whole cabinet, just like the LMS did at the GTG. Second these drivers are a real PITA to remove from the cabinet once they are in there. I smashed another finger and lost the first couple of layers of skin due to the driver getting wedged. . I took the driver out so that I could stuff some pillows in there and smooth things out a bit. I'll post up the data from the WT3 impedence traces and close mic FR measurements for before and after stuffing the enclosure. One thing I am concerned about in an enclosure this small with stuffing the 5 pillows in there is heat build up when pushing it hard for extended periods. In this size of a box the Q is getting up close to 1.0 with this driver, so it's a bit peaky at 30hz. The pillows seemed to help flatten it out a bit. Still a larger enclosure volume would help out a lot there.

It seems like the driver in the smaller box distorts earlier than it should. Once the excursion gets up around 2.5" p2p things start to sound different. In the larger 10ft box, or the 25 footer it does not do this. I free air all of my drivers and note the point at which they start to "lose it" and this one is the same as the rest of the XXX's which is utterly clean mechanically until you start approaching the outer limits. I don't think it's related to the power either. The CE4000 is not clipping at all and it is not happening at the higher bass freq's where the power related issues should be worse. Neither the amplifier or the driver are out of their operational envelope at the point it starts happening. It's only once the excursion starts to get high. I've not noticed it with actual material either. Just sine waves or sweeps. Could this be the dreaded ASD kicking in, or perhaps it's related to an air leak? Something else? I'll be dragging my 10ft test box out there for a heads up test between the 2.

One other thing that I figured out last night is that somewhere around 120db the ECM8000 is overloaded and it probably starts distorting well before then. At some point it quits increasing the signal it puts out and compresses like all get out. I figured this out doing close mic stuff. If you put the mic 3" from the center of your 18" subwoofer cone it doesn't take much at all to hit 120db there. I was trying to set all of my gains ( around 7 total) and was running into huge compression somewhere in the chain. After checking nearly everything else I figured out it was the mic. It also seems to vary somewhat with the frequency range. I'm going to buy another ECM8000 that's professionally calibrated and see what happens. Maybe mine is defective. This also makes me wonder about how much of the compression I encountered during my sweep tests was actually the subwoofer and what was the microphone's contribution. I'm starting to think that the mic had a significant impact on the highest sweep levels, since I should've easily heard that much, but didn't. I don't know how much it may have affected the rough THD measurements too. Someone had brought this up as probable before. I think it was Noah Katz. I just assumed that it wouldn't be more than a very tiny effect compared to the rest of the system. Maybe it's time to look into something a little better in quality.
robseyes's Avatar robseyes 10:52 AM 03-12-2009
Quote:
Originally Posted by Ricci View Post

I did some messing around last night with the 24" cube (6ft) XXX and ran into some interesting things. First if I push it hard it will start to rock the whole cabinet, just like the LMS did at the GTG. Second these drivers are a real PITA to remove from the cabinet once they are in there. I smashed another finger and lost the first couple of layers of skin due to the driver getting wedged. . I took the driver out so that I could stuff some pillows in there and smooth things out a bit. I'll post up the data from the WT3 impedence traces and close mic FR measurements for before and after stuffing the enclosure. One thing I am concerned about in an enclosure this small with stuffing the 5 pillows in there is heat build up when pushing it hard for extended periods. In this size of a box the Q is getting up close to 1.0 with this driver, so it's a bit peaky at 30hz. The pillows seemed to help flatten it out a bit. Still a larger enclosure volume would help out a lot there.

It seems like the driver in the smaller box distorts earlier than it should. Once the excursion gets up around 2.5" p2p things start to sound different. In the larger 10ft box, or the 25 footer it does not do this. I free air all of my drivers and note the point at which they start to "lose it" and this one is the same as the rest of the XXX's which is utterly clean mechanically until you start approaching the outer limits. I don't think it's related to the power either. The CE4000 is not clipping at all and it is not happening at the higher bass freq's where the power related issues should be worse. Neither the amplifier or the driver are out of their operational envelope at the point it starts happening. It's only once the excursion starts to get high. I've not noticed it with actual material either. Just sine waves or sweeps. Could this be the dreaded ASD kicking in, or perhaps it's related to an air leak? Something else? I'll be dragging my 10ft test box out there for a heads up test between the 2.

One other thing that I figured out last night is that somewhere around 120db the ECM8000 is overloaded and it probably starts distorting well before then. At some point it quits increasing the signal it puts out and compresses like all get out. I figured this out doing close mic stuff. If you put the mic 3" from the center of your 18" subwoofer cone it doesn't take much at all to hit 120db there. I was trying to set all of my gains ( around 7 total) and was running into huge compression somewhere in the chain. After checking nearly everything else I figured out it was the mic. It also seems to vary somewhat with the frequency range. I'm going to buy another ECM8000 that's professionally calibrated and see what happens. Maybe mine is defective. This also makes me wonder about how much of the compression I encountered during my sweep tests was actually the subwoofer and what was the microphone's contribution. I'm starting to think that the mic had a significant impact on the highest sweep levels, since I should've easily heard that much, but didn't. I don't know how much it may have affected the rough THD measurements too. Someone had brought this up as probable before. I think it was Noah Katz. I just assumed that it wouldn't be more than a very tiny effect compared to the rest of the system. Maybe it's time to look into something a little better in quality.

Q of 1.0? Wow that thing likes a hugebox! Just for fun I ran the numbers in unibox & in 6 cubes excursion shelves at 44 mm (3000 watts). Ten cubes definitely models better. How does it sound in the 6 cube box?
Ricci's Avatar Ricci 01:52 PM 03-12-2009
Quote:
Originally Posted by robseyes View Post

Q of 1.0? Wow that thing likes a hugebox! Just for fun I ran the numbers in unibox & in 6 cubes excursion shelves at 44 mm (3000 watts). Ten cubes definitely models better. How does it sound in the 6 cube box?

Yeah. It does. Try entering in an LE of 3.8mh also into Unibox. That's about the average that I get back from the WT3. I'm running about 2800w on them from the CE4000's.

I'm trying to figure out how it sounds in the 6ft box. I'd love to be able to run them in this size enclosure, but I'm not sure yet. It seems a bit peaky. I've not had a lot of time with the 6ft cab yet and the 2 places I've heard it at so far, I'm not familiar with. One was Warpdrv's house of course and my practice/rehearsal space which is a gigantic and lossy 40x20x18, or about 14000cu ft, which I've never had a real subwoofer in until lately. That's part of the reason I'm going to take my 10ft beater box up there, so I can compare the 2. I know that it sounds pretty good in the 10ft cab. I think this driver might be smoother in the bigger airspace.
Warpdrv's Avatar Warpdrv 02:15 PM 03-12-2009
Wow.... I thought it sounded really really good at the GTG, likely because WE couldn't handle it running full bore in that smaller room. It didn't seem like it was compressing in that little room...

I can couple that thought in ref to my F112.... I have read a good amount of people that have gotten the F112 to hit the built limiter on it when running full out, but in my small room I have never ever heard it kick in (due to the small room?).
robseyes's Avatar robseyes 10:02 PM 03-12-2009
Quote:
Originally Posted by Ricci View Post


I'm trying to figure out how it sounds in the 6ft box. I'd love to be able to run them in this size enclosure, but I'm not sure yet. It seems a bit peaky. I've not had a lot of time with the 6ft cab yet and the 2 places I've heard it at so far, I'm not familiar with. One was Warpdrv's house of course and my practice/rehearsal space which is a gigantic and lossy 40x20x18, or about 14000cu ft, which I've never had a real subwoofer in until lately. That's part of the reason I'm going to take my 10ft beater box up there, so I can compare the 2. I know that it sounds pretty good in the 10ft cab. I think this driver might be smoother in the bigger airspace.

Man have you tried a 6db shelving filter on that that behemoth? With all that excursion, it's a no brainer (especially corner loading it). I wouldn't worry too much about going thermal if you are going to go sealed with 4 of them (unless of course you really like to run sine waves at silly levels on a regular basis). The room does have a huge effect.......I would love to hear what you think in a room that is more reasonable in size.. We played around with my friend's 8ft sealed Maelstrom in his living room (20 ft ceilings & open architecture) & it was surprising how much of the ultra lows were lost (we even bridged my Crown CE4000 into it & were playing it at stupid levels). I tried to convince him he needed multiples, but he got discouraged & bagged the DIY route. He wouldn't believe me until he got an Epik Conquest in there & it didn't even fill the room like he would have liked! It wasn't until he moved that he finally saw (or heard) the light when he got his theater into a room that actually gave him some gain.
Ricci's Avatar Ricci 11:03 PM 03-12-2009
Quote:
Originally Posted by Warpdrv View Post

Wow.... I thought it sounded really really good at the GTG, likely because WE couldn't handle it running full bore in that smaller room. It didn't seem like it was compressing in that little room...

I can couple that thought in ref to my F112.... I have read a good amount of people that have gotten the F112 to hit the built limiter on it when running full out, but in my small room I have never ever heard it kick in (due to the small room?).

I thought it sounded good too. It's not compressing. It's hard to explain. I heard something in the sound once a pretty good excursion level was reached, but keep in mind it only happened with large excursions and not with higher bass freq's even at much higher levels. I'm talking about still well within the drivers linear comfort zone too. Hell man you saw it at the GTG, you know what I'm talking about here. Smooth. I only heard it with a sine wave and it's in a huge 14000ft room in a warehouse now, so there's not a whole lot of gain. We only used actual material and had a much better space at your place. It's not like a overloaded, driver unhappy kind of sound. I'll be able to investigate more soon. I'm thinking it may be just an air leak around the driver, or mounting screws that gets exacerbated more by high excursions...or it may just not be enough airspace for it to do it's thing.
Warpdrv's Avatar Warpdrv 06:30 AM 03-13-2009
Had to go messin around with a good thing by takin it out of there huh....

Did you ratchet it down with a bit driver like I did at the GTG.... like tightening up a wheel with torque sticks. That a great method for insurring a good seal...

Its weird, the only time I ever get into situations like that where I encounter problems like your suggesting is in my great room... an open cavernous area just like yours there... why is that.... no room gain to react with the driver, it should have no bearing on it at all...
Ricci's Avatar Ricci 07:23 AM 03-13-2009
Quote:
Originally Posted by Warpdrv View Post

Had to go messin around with a good thing by takin it out of there huh....

Did you ratchet it down with a bit driver like I did at the GTG.... like tightening up a wheel with torque sticks. That a great method for insurring a good seal...

Its weird, the only time I ever get into situations like that where I encounter problems like your suggesting is in my great room... an open cavernous area just like yours there... why is that.... no room gain to react with the driver, it should have no bearing on it at all...

Yeah I know...: I just can't leave things alone.

I don't remember hearing it until I took it out to put the pillows in. It probably is just an air leak. I thought that I torqued it down pretty good in a criss cross pattern just like changing a drum head or wheel, but I did use a screwdriver.

It's hard to get that tactile low bass out of a sealed sub in a friggin cavernous area!
Nuance's Avatar Nuance 07:39 AM 03-13-2009
Ricci,

Are you putting some sort of weather strip or sealant pad around the baffle, between the driver and baffle? My TC had an air leak until we put that around the edge. Now it doesn't bat an eye until extreme levels.
Ricci's Avatar Ricci 07:40 AM 03-13-2009
Yes. It still has the wather stripping that Patrick put on there at his place.
Warpdrv's Avatar Warpdrv 08:00 AM 03-13-2009
You should get a drill with a ratcheting torque setting set it to like 4 and go all the way around, and then up the setting to 5 and do it again... thats a #3 philips bit on those big ass stainless screws, so no worry about stripping the head out...

I got that method down pretty good, and it goes quick. The weather stripping with the little cut outs where the holes work great so you don't wrap that stripping around the screw when its going in....
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