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From endless contemplation to fruition: James' First DIY 18" Sub. How low can you go...$-wise? - Page 3

post #61 of 195

Isn't the Cap ported?  I have not had good results mixing ported and sealed.  The FR at and below tuning gets wonky.  I never figured it out and gave up to go all sealed.

post #62 of 195
Thread Starter 
ahhhh the turn in my punchbowl! Just kidding. Yeah I did think about that, but decided to roll the dice anyway, lol. I have another room or folks that can take advantage of it.

I simply cannot use the size of a ported box right now...unless someone tells me it can be 5.5^3 or less. Most of what I've thrown into calcs and read point to something closer to 7-10^3, unfortunately.

James
post #63 of 195
Quote:
Originally Posted by mastermaybe View Post

By the way, I have to purchase the software to "model" the driver(s), correct?
No, there's Unibox (my preference but needs Excel) and WinISD for free, plus a couple of online ones.
post #64 of 195
Quote:
Originally Posted by mastermaybe View Post

ahhhh the turd in my punchbowl! Just kidding. Yeah I did think about that, but decided to roll the dice anyway, lol. I have another room or folks that can take advantage of it.
I fixed that for you. wink.gif

You really need to time align the subs to your seat, especially if you're putting the sealed sub closer to you. A MiniDSP might help but it only has 7.5ms of delay which might not be enough depending on how much closer you're placing the sealed sub to you than ported sub.
post #65 of 195
Thread Starter 
^ I'm sorry, what did you "fix"?

Not trying to be a DB, just want to make sure I haven't missed something.

thanks

James
post #66 of 195
Quote:
Originally Posted by mastermaybe View Post

^ I'm sorry, what did you "fix"?

Not trying to be a DB, just want to make sure I haven't missed something.

thanks

James

Haha he fixed your misspelling of "turd." Hes an expert on those.
post #67 of 195
Thread Starter 
I'm utterly confused. Is there another way outside of "turd"?

OOPs, just noticed I typed an "n" instead of a "d".

holy hell.

James
post #68 of 195
Quote:
Originally Posted by mastermaybe View Post

ahhhh the turn in my punchbowl! Just kidding. Yeah I did think about that, but decided to roll the dice anyway, lol. I have another room or folks that can take advantage of it.

I simply cannot use the size of a ported box right now...unless someone tells me it can be 5.5^3 or less. Most of what I've thrown into calcs and read point to something closer to 7-10^3, unfortunately.

James

See?

 

Don't worry about it, SD was being funny and taking a jab.  It was funny, I laughed.rolleyes.gif

post #69 of 195
Thread Starter 
Yep, I got it, prolly just varying opinions on humor. It's all fine.

So am I buying the wal mart pillows to stuff this thing?

If so, how much/many?

the whole stuffing thing is an unknown to me.

thanks


James
post #70 of 195
Thread Starter 
Ok, with my beautiful 13 month daughter running around the house today one word occurred to me...well, one hyphenated word anyway: down-firing.

Possible? Doesn't this work against the suspension and motor?
What happens with re to response/performance?

You don't see a huge number of high-performing down firing subs (yes I know that they exist though) so I'm just wondering. I can always build a grill.

Thanks
James
post #71 of 195
Quote:
Originally Posted by mastermaybe View Post

Ok, with my beautiful 13 month daughter running around the house today one word occurred to me...well, one hyphenated word anyway: down-firing.
Possible? Doesn't this work against the suspension and motor?
What happens with re to response/performance?
You don't see a huge number of high-performing down firing subs (yes I know that they exist though) so I'm just wondering. I can always build a grill.
Thanks
James
DriverOrientation.pdf 9k .pdf file
Driver Orientation by Dan Wiggins, back when Adire existed.

You could also enter the driver parms into Unibox and check for suitability in the Down Fire Application box.
post #72 of 195
I got a .95 downfire rating in Unibox with this driver. Seems acceptable to me to be used in that configuration.
post #73 of 195
^^ Wiggins paper says 5% (= 0.95) is OK.
post #74 of 195
Yup. smile.gif

Better if it were less but 5% is acceptable.
post #75 of 195
Thread Starter 
Thanks guys. Perhaps I'll think about it more today before I start cutting tonight. Cabinet size and all being equal, is the performance comparable...I realize I lose a smidge of Xmax, but what about THD and SQ, and vessel gain?


Thanks!

James
post #76 of 195
FWIW,

I believe there's a myth regarding gravities effect on long throw drivers in that most everyone believes that when the driver is in a vertical position (basically, how drivers are stored on a shelf or in a down or up firing configuration) there is a deal breaking effect vs when it's in a horizontal position (mounted in a front firing configuration) where there is zero effect.

sag_zps4f325a17.jpg

After having thought about the situation a long time ago, I decided that the ill-effects of sag in a FF config are far worse than the alternative. The relationship of the coil to the gap regarding how close the coil is to the pole piece on the inside and the top plate hole on the outside is a very tight tolerance. The smaller those distances, the higher the motor strength. But, the smaller those distances, the higher the chance of rubbing/destruction. In the worse-case compromise of a larger gap to insure against rubbing, there is still a very small distance involved.

IOW, in a down firing position, sag can be considerable and not cause failure of the driver, but in a horizontal position, just a wee bit of sag can cause destruction.

I believe that, short of adhesives or spider and surround materials failure, a top shelf driver should last virtually forever. I also believe that the downfall of these drivers is time and the effect of gravity causing the coil to move off center in the gap more so than any other reason, assuming the driver isn't abused.

I decided to go 1 up, 1 down because as long as the VC remains centered in the gap in a concentric manner it will continue to work, whereas if it moves off center in an inward/outward sense, it will only lose some X-max and suffer some asymmetric 2HD. But, every 5 years or so, you simply remove the drivers and reinstall them in switched positions. I haven't commented much on this in the past because I wanted to wait 10 years and observe and measure the results vs arguing endlessly against some ancient and untested math formula.

Again, that's in the FWIW, YMMV folder, since cone sag came up in the thread.
post #77 of 195
Thread Starter 
Makes sense, and some time ago I actually considered the very aspect you brought up above when considering some of these LARGER (18") drivers with heavier (treated paper) cones (hanging/sagging down over time).

thanks for the insight.

James
Edited by mastermaybe - 10/12/12 at 12:19pm
post #78 of 195
Thread Starter 
Just an iphone snap...I don't know where I fall in the "bracing debate" but after having just 4 of the panels together and two braces front to back, I'd be confident to use it for a jack stand...ok, maybe not, but it's absolutely rock solid.


FCC78D09-654C-4C84-8CE4-B696B7849384-1549-000000B672411A1A.jpg


James
post #79 of 195
Why didn't you put the braces in the middle of the box instead of so close to the ends?
post #80 of 195
Thread Starter 
Because that would be impossible, lol. Those are on either side of the driver, front to back. I'm going to add two connecting the sidewalls this evening.

James
post #81 of 195
Thread Starter 
By the way, the driver itself is quite good looking, and even the surround/mounting flange is nothing I'm too concerned with hiding.

So that said, I can I simply mount it to the baffle and not worry about counter-sinking it? I know with mid's and tweeters you're looking to avoid diffraction/coloration, but I shouldn't really be running into that with this build, correct?

B79DC03B-7B28-4D32-8D2C-F6DA6C894429-1549-000000B8AE99F5B8.jpg

thanks

James
post #82 of 195
Quote:
Originally Posted by mastermaybe View Post
 
I don't know where I fall in the "bracing debate" but after having just 4 of the panels together and two braces front to back, I'd be confident to use it for a jack stand...ok, maybe not, but it's absolutely rock solid.


James

 

Wow man, 2x4s for bracing?  Those are way too flimsy, I'd use at least 2x6s or 2x8s....  tongue.gif

 

Keep dem pics comin.....  More of the driver especially of you don't mind, particularly the suspension and motor structure.......

post #83 of 195
Thread Starter 
oops
Edited by mastermaybe - 10/15/12 at 9:49am
post #84 of 195
Thread Starter 
Ha ha, yep. Had one (2x4) laying nearby, so I figured, wth?

I'm drawing my volume closer to 3.5^3 so it should end up just peachy for my amplifier.

I've done my fair share of woodworking so I wasn't terribly surprised by how fantastically strong/rigid a 3/4" plywood cube is when properly joined, straightaway, but this thing is ridiculous, and outside of a driver capable of physically moving the cabinet (which I'm well aware exist, LMS Ultra anyone?) I think you could easily spend more time, money, and material over doing bracing for many drivers. Just an opinion, we're all free to do what we like.

I'll get some more pics of the driver this PM, I have to say that I"m really happy with its build quality and aesthetic- the aluminum cone and rubber surround are a great combination. The frame and motor also appear to be stout and quite capable for this $-figure.

James
Edited by mastermaybe - 10/15/12 at 9:00am
post #85 of 195
Quote:
Originally Posted by mastermaybe View Post

By the way, the driver itself is quite good looking, and even the surround/mounting flange is nothing I'm too concerned with hiding.
So that said, I can I simply mount it to the baffle and not worry about counter-sinking it? I know with mid's and tweeters you're looking to avoid diffraction/coloration, but I shouldn't really be running into that with this build, correct?
James

No. Don't worry about that. There will be no measurable difference and really it just makes installation/uninstallation that much easier. wink.gif
post #86 of 195
Thread Starter 
^ figured as much, thanks. And I'm not even convinced it (counter sinking it) looks any better, anyway.

James
post #87 of 195
Quote:
Originally Posted by NicksHitachi View Post

Wow man, 2x4s for bracing?  Those are way too flimsy, I'd use at least 2x6s or 2x8s....  tongue.gif

Keep dem pics comin.....  More of the driver especially of you don't mind, particularly the suspension and motor structure.......

This! Moar pics!!!
post #88 of 195
I am looking forward to hearing how this driver sounds and compares to some of the other 18" drivers that are out there!
post #89 of 195
Thread Starter 
a little updates...

Some more driver pics...

F9B3E5C6-E36E-41A1-83E4-461FC5FCAD8D-854-000000634EBCC3B6.jpg

aluminum cone is quite thick...

29173DF6-6272-4415-896C-DC12955BE794-854-0000006345DECE41.jpg


052AD81B-AF8F-4550-AAC9-1D1FB10521E3-854-000000633B58A219.jpg

Plenty of ventilation...

90A212F9-0A25-4B5F-8027-47A74888CD55-854-000000632D1B9DC8.jpg

Boxed up...

29C80721-13E8-4D6E-94DE-B75E3722F91E-854-00000062FDF433B5.jpg

Sure footed...don't worry about those edges, they will be filled and sanded glass-smooth. I've found that depending on a circular saw to cut perfect 2 foot edges (or even taking your time to do it) really are not minutes best spent with a good orbital sander and 80 grit on hand, lol.

50BB6EC4-5BDC-4B6F-AD9A-260AE29CEE62-854-000000630EA35390.jpg


Going to get the driver and speaker terminal holes cut tonight. Apply cross brace and battens, internally seal, fill and finish-sand cabinet. Hopefully will be ready to take paint by tomorrow. Internal volume will finish right around 3.65 ^3's.


James
Edited by mastermaybe - 10/16/12 at 8:18am
post #90 of 195
Quote:
Originally Posted by Martycool007 View Post

I am looking forward to hearing how this driver sounds and compares to some of the other 18" drivers that are out there!

I have no doubts that this one will sound pretty damn good. wink.gif

Quote:
Originally Posted by mastermaybe View Post

a little updates...
Some more driver pics...
James

Sweet! Thanks
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