|
[Previous Message]
[Next Message]
|
| Date: |
March 05, 2009 at 00:54:53 |
| From: |
norman bates, [173-20-191-217.client.mchsi.com] |
| Subject: |
nice driver |
|
|
|
|
Yes, ideal ported you need 6.4ft3 and tune to f3 which is 21.74hz.
The problem is the port size. Xmax with cone area, that is crunched to get a mach value (air pressure in port). At tuning frequency, the driver should stop (if the port is big enough). The further the driver moves, the more distortion and the closer to your sub is to going klank (bottoming out). If you keep the volume low, you can get away with a smaller than ideal diameter port.
Passive radiator is an option but may cost another $100.
I had a dual 18 box 18ft3, it had a 12" port about 17" deep (27hz). That was 2 x 18's with 8mm xmax (each). That was fine for me. People thought they heard 20hz. Insted they got 123db+ of 27hz (anechoic, no room boost). Flattening loud with a wonderful sound.
I was sketching a box for an 8" with 13mm xmax. I figured it'd need a 4" port, but to tune to 30hz in a 1ft3 box, the 4" port needed to be almost 30" long.......
The max excursion is about 1/3 octave above tuning.
If you tuned to 30hz, you may need 100 watts at 40hz to skip past xmax.
If you tune to 20hz, you may only need 25 watts to skip past xmax at 27hz.
You have to play around with win isd to see how much power it takes..........
If you want some driver protection when the kids crank it, I recommend a 3.2ft3 sealed box (qtc .707). But that sealed box has an f3 of 37hz. And the amp can still clip then ring then bottom the driver out.
I know a qtc .707 sealed with f3 of 45hz was lame compared to a ported f3 of 27hz.......... In the exact same corner, same amp too........
Yup, brace the schmoo out of it.
Forget any fill or carpet.
1" wood is good (especially hdf).
I have just recently heard the difference changing from 40hz to 30hz. The 30hz is like an extended bass shelf, but to me it is deeper and quicker (it hides better). Those drivers I have ideally want 8ft3 each with a 30hz tuning. I have both in 8ft3 tuned to 30hz. Similar to Japanese speakers that go for a lean, quick sound (think low tuned ports or Qtc .577 sealed making great low group delay numbers).
I think 27-30hz tuning works well.........
You can tune the port to whatever frequency you want.
I think it would be neat to have a pair of 15's with dual ports. Then you block 1 for a 20hz tuning, leave both open for 27hz.......
Here are some ideas for you woodworkers out there...
http://www.hometheaterhifi.com/volume_12_3/images/triad-gold-subwoofer-internal-bracing.jpg
http://www.mrcrackers.com/images/subwoofer/bracing_front.jpg
|
|
|
| View the previous message in this thread
Go to the top of this thread
View entire thread |
Posted with TalkShop version
2.77 BETA |
[Previous Message]
[Next Message]
|
|
|
Follow Ups: |
|
|
|
[
The Subwoofer DIY Page - Discussion Forum ] [ FAQ ] |
|
|
|
