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"What a larger magnet can do" was one of the central topics in the modeling world
wrt Inductance and how much of a "tweak" was / might be needed as a necessary non-standard function in many (?), a few (?) of the standard modeling programs.
iirc, @chapladm in Australia had a published paper and was one of the behind the scenes gurus contributing, along with @LTD02 and no doubt a few other to
the finalized model of the Submaximus V3. 40 cu. ft. FLH, UXL 18", at about 350 lbs total. only took me 19 days to build it and get it tested and performing.
subsequently, I had a good correspondence with @hd0823 when he got excited and wanted to build 4-which he then upgraded to using 21's.
His dedicated HT , the pics- and a few more subs, excellent throughout.

an excellent launch for this project also, getting the T/S specs
"May the good specs be yours"
 
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and then after getting the T/S spec,
given the re-coning and other changes . .
 

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Discussion Starter #83
Well, finding the T/S params in REW is not working at all like it's supposed to.
Ironically, I can't get them to work at all using a Focusrite Scarlett 2i4, which is pretty much front and center on the REW page.
I keep getting "the level difference between the channels is larger than it should be blah blah... calibration not valid"
So then I tried it directly connected to the PC mic/stereo jack. That time all of the calibrations went through, with the exception of it saying at the end that the level is low, so results may not be as accurate (I raise the level and it clips).
So then I hook it up to the sub and this is the impedence curve:
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The amount of time after work I've put into just trying to get this cable to work is getting pretty frustrating. I think I'm going to remake the cable, even though I triple checked it for accuracy, and of course, soldered everything. You never know I guess.
The only thing I know for sure right now is the subs are dual 1.7ohm.
 

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surely . .
huge space to work with
huge drivers,
huge resources / motivation to get it right
ATTITUDE IS EVERYTHING
 
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John Mulcahy is a frequent poster on Audio Nirvana where the download is hosted. Pop in there and ask him.

Well, finding the T/S params in REW is not working at all like it's supposed to.
Ironically, I can't get them to work at all using a Focusrite Scarlett 2i4, which is pretty much front and center on the REW page.
I keep getting "the level difference between the channels is larger than it should be blah blah... calibration not valid"
So then I tried it directly connected to the PC mic/stereo jack. That time all of the calibrations went through, with the exception of it saying at the end that the level is low, so results may not be as accurate (I raise the level and it clips).
So then I hook it up to the sub and this is the impedence curve:
View attachment 3044421

The amount of time after work I've put into just trying to get this cable to work is getting pretty frustrating. I think I'm going to remake the cable, even though I triple checked it for accuracy, and of course, soldered everything. You never know I guess.
The only thing I know for sure right now is the subs are dual 1.7ohm.
 

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Discussion Starter #87 (Edited)
surely . .
huge space to work with
huge drivers,
huge resources / motivation to get it right
ATTITUDE IS EVERYTHING
True that. Attitude really is everything.
You know, I want to call out that I appreciate the responses from you guys more than you know. It really motivates me.
Even in the little time I've had this build thread going, I've considered just buying another pre-fabbed sub and calling it good. I'd listen to a song on my system right now and think, "hmmm that's pretty decent bass." Watch a movie, "hmmmm that's pretty decent bass." I think to myself, "what are you doing?"
Then I come back and see posts from you guys. You're not cheerleaders or fans (weird), but you are people who are genuinely curious as to what is happening here. That's neat to me that I can present something like this for you all to enjoy as well.

GK- I love your sig for unobvious reasons. Also, thanks, I didn't think of simply asking directly there. If I can't get it to work with the new cable, that's exactly what I'll do.

I was thinking about the fact that this subwoofer is HUMONGOUS... so how much added mass am I going to have to add to the cone to get an accurate measurement? I mean in the video, the guy uses about 320g of playdoh for a woofer that's maybe 7" lmao. Glad I've got weights in the basement. Seriously though, I've got them down to 1.25lbs- I'm sure it doesn't need more than some of those.
Also had me wondering with regards to the added mass method, why do people use playdoh? I think it's because you want whatever added mass is there to stick, and not bounce. I mean I can't really see it bouncing though with the power of a PC sound card, but that's the thing that makes the most sense to me.

Alright, I am remaking the cable now.

EDIT:
(example uses a focusrite scarlett- SCORE)
 

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Discussion Starter #88
So I am 100% positive I made the wire correctly this time.
I'll have to ask at the AV Nirvana forums like GK suggested.
Oh well, I'll try again tomorrow.

Have a good evening!
 

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"hmmm that's pretty decent bass."
not to be much more than the devils advocate / Capt. Obvious here
however
Some REW work to establish a baseline (no pun intended) for what is happening in the room NOW
can be a guide to contrast / guide expected / achieved improvements

i.e. with the 2x4, my 3 THTLPs may not get the full oompah-loompah of the EOT opening but I don't think the cost / benefit ratio can justify the time and expense for the last 8-10 seconds of that opening clip. that's what the 2 x12's nearfield are for, at least wrt TR and then there are the 4 Aura shakers well anchored to the seating.
rabbit hole? what rabbit hole?
 
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Discussion Starter #90 (Edited)
You've got a point- I have measured the room for dirac live on my receiver, but I've never measured it using REW. I'm sure I will end up doing that, as I've got the tools anyway.
Speaking of tools, I decided to just grab a few USB sound cards from online. I'll return two of them. I'm sure it's the Focusrite that is causing the issues, as I can get somewhat of a measurement from the ports on my desktop computer. Also, that is no fault of the Focusrite--I am probably incorrectly setting the dials. USB sound cards are a dime a dozen these days. I'll just follow the video to the 'T'.

That's about the only update right now. I plan on having some fun with REW tomorrow now that the workweek is over.

Closing thoughts: A subwoofer can only play as low as the input tells it right? Well, what are the lower limits for amplifiers? Do certain types of amplifiers have certain cutoff frequencies they won't play below? I imagine so, as I've read something like the lower the hertz, the more power that is drawn. That's probably wildly incorrect to someone more knowledgeable on the subject, but I believe it's true enough to help make my point. I imagine amplifiers that can play down in the single digits have no filter, or a 'lower' filter. I think I read that actually- which is one of the reasons I chose the Behringer, or a P.A. for that matter. These professional amplifiers don't have that low Hz cutoff, so they can play as low as they can go until thermal overload I'd imagine lol. I probably need to read up a lot on that because now I'm very curious and I need something to do before those sound cards get here.

I'm also curious of the Sanway amplifiers. Chinese clones of great amps I guess. I'm sure at least a few of you here have used them as they are fairly popular it seems. I believe they are considered professional as well though, which would make sense combined with my previous statements about being able to play low. So perhaps when it comes to types of amplifiers, there are car amps, home theater amps, and professional amps (for venue/stage use). Sanway is just another type of professional amplifier that people use for subwoofers as well because of the output. Same reason I bought the Behringer.

(P.S. I know about Bass EQ because of that video you posted, asarose. That's amazing that you can add back in the original lowest frequencies of films.)

Alright, I'll be posting again tomorrow I'm sure. I've got a lot to do.
 

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Discussion Starter #91
Alright so hopefully I'm meeting a guy this morning/afternoon to pick up a DATS V2 (I'm sure it still works, even if it's not the latest V3), miniDSP 2x4HD and a UMIK-1. I already have an EMM-6 mic, but that requires phantom power, and the scarlett I am only borrowing. I'll end up selling the EMM-6 when I grab this. That being said, I am grabbing the miniDSP because I want to experiment. I'm sure my receiver's Dirac Live would work for the subwoofers, but I want to be able to really fine tune multiple subwoofers. I think the 2x4 HD will come in handy for that, especially helping me to learn the ins and outs of REW and that ever-so-popular 'House Curve' I hear everyone talking about :)

Just waiting for those USB sound cards to get here so I can begin having some fun. Then I'll compare those findings to the DATS findings. Why not? It's all in the sake of fun.

I hope everyone has a terrific Saturday!
 
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Discussion Starter #93
Definitely enjoying reading about your journey! Good luck with your endeavors this weekend!
Glad you're enjoying and thanks- ENDEAVORS THEY WILL BE!
No excuses, so I guess I'll actually have to find these T/S parameters now... ;)
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Discussion Starter #94
Hahaha, well never count your chickens before they're hatched as they say.
Finding the Thiele/small parameters for these are proving to be really challenging. The problem is, the results very too much. For instance, I measure with the driver on the carpet- F(s) 17Hz. On a foam pad, 19Hz. On top of a couple sideways 2x4s, 20Hz. Vas ranged anywhere from 17 cu ft to 25 cu ft. Sometimes the amount of added mass was enough, sometimes it wasn't. Qts from .7 to .86.
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I 100% believe this is because of the lack of amplification for a driver this size. 1 volt is only going to get you so far with a 24", 3000W RMS driver. So now I have to look in to how I can add an amplifier to this mix, without blowing anything, while measuring
There were a few things that remained constant throughout the tests, FOR WHAT THEY ARE WORTH.
The impedance graphs were consistent.
SPL was mostly always around 87-88
R(e) always around 1.65 Ohms
Here's an example of one of the test results:
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As I said, some or none of that may be worth anything at this point. I feel with the way the measurements vary so much, I'm going to have to introduce an amplifier in to the equation before I can get any kind of consistent, repeatable results I can trust. Some new questions were raised today as well with regards to getting accurate measurements:
1) Does the hole in the bottom of the motor need to be open/vented underneath or can the driver be measured while sitting on the floor?
2) Does the room need to be extremely quiet in order for these tests to be accurate? For instance, will the low 'hummmm' of a desktop pc or the sound of air conditioning invalidate measurement results? I know for Dirac, the room is supposed to be so quiet, you should not be able to hear things like the refridgerator running (ideally they say).

I got the number of the gent from Sundown who swapped out the motors and reconed the subs, so I'll probably give him a holler tomorrow to see what he thinks about the parameters.
 
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The underside of the woofer should be vented for most accurate TS parameter checking. I usually use some thick foam gasket stuff under the drivers, it's about 1/4-1/2" after being compressed. Horizontal would be better but vertical is fine, haven't seen a huge different either way. PC operating or AC unit won't significantly impact TS parameter reading.
 

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Discussion Starter #96
The underside of the woofer should be vented for most accurate TS parameter checking. I usually use some thick foam gasket stuff under the drivers, it's about 1/4-1/2" after being compressed. Horizontal would be better but vertical is fine, haven't seen a huge different either way. PC operating or AC unit won't significantly impact TS parameter reading.
Chris, thank you sir!
No offense, but I can't go around just believing what everyone tells me.
That being said, by the unwritten book of the internet, you've got nearly 1000 posts, appear to have used your real name, joined almost 15 years ago, and are a contributing member, so I take your word!

Alright, so I guess I had the right idea with elevating the sub and trying to give that area to breathe. Only thing is, these are so damn heavy AND the underside of the motor is kind of slanted, making it difficult to get it to stay rested on anything without covering the holes (the holes are in the part that's flat of course). In fact, I'm going to go weigh this beast and take pictures of what I'm talking about. I'm also curious as the motors were swapped, so they aren't the standard HS24 weight. One moment. Okay, so I got 93lbs a piece. Interesting- the OGs are 95, so for all intents and purposes, these way the same (I'm sure my scale isn't completely accurate).
Here is a picture of the bottom. The non-blurry part is the part that's flat. So I'm unsure how to elevate these to allow those holes to breathe. Perhaps the racquetballs were the best way- wedging them under there in the slanted part... being rubber, they grip the slanted sides.... just a pain in the arss.
3045419


So now I've got to figure out how to amplify this signal for the measurements... off I go.
 

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Alright, so I guess I had the right idea with elevating the sub and trying to give that area to breathe. Only thing is, these are so damn heavy AND the underside of the motor is kind of slanted, making it difficult to get it to stay rested on anything without covering the holes (the holes are in the part that's flat of course).
I would build a 2x4 frame large enough to hold the sub by the basket and put legs on it (fast, cheap). Or put it between 2 saw horses and screw it directly to them.
 

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Discussion Starter #98
I would build a 2x4 frame large enough to hold the sub by the basket and put legs on it (fast, cheap). Or put it between 2 saw horses and screw it directly to them.
Great idea!
Don't mind if I do...
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I thought it was pretty cool how that worked out. Now let me tell you, F that a million times getting them in and out of there. At one point I was putting the second woofer down into the contraption, and for a good 20 seconds I just sat there with a couple fingers pinched. I realized my best bet was to use my legs and push up with my quads. I should make an engine hoist lmao. (really, I do need to get a pully system for when I attach it)

The parameters were more consistent this time. That's good! I still think I may need to figure out the amplification measurement technique, but I am unsure. What do you think?
1602469205001.png 1602469169026.png
 
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@ SteveCallas
I certainly don't have the background ,JS
do you have a short answer layman orientated about why the parameters don't matter for IB.
 
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