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box design help

post #1 of 10
Thread Starter 
im needing some help in picking a design for my sub. i am currently using a sonotube setup with a sinlge polk momo, tuned @ 23hz.
At high levels the mains will drown it out. i have 2 of these subs available if it would help output. im just lost as to what setup would be best.

i had a friend recommend using the jensen imperial plans, but im not sure if i want to invest into a refrigerator sized sub if its only a marginal improvement over what i have now. http://www.decware.com/imperial.htm

the space i have designated is a 40"wx36"d space. height would be dependent on design. the ceiling is 9', but anything under 48" high would be ideal.

if anyone has any ideas or input for the best possible design it would be appreciated.
post #2 of 10
Quote:
Originally Posted by mcdizzle View Post

i had a friend recommend using the jensen imperial plans,
The Imperial is not a subwoofer and should not be considered for any use, being a design that was rendered obsolete some 30 years ago by modern driver technology.
post #3 of 10
Thread Starter 
it looks very similar to a folded horn design, and was used for speakers with a lower xmax, which is why i thought it might be feasable to use. what would your choice design be, based on the info i gave in the first post?
post #4 of 10
Quote:
Originally Posted by mcdizzle View Post

it looks very similar to a folded horn design, and was used for speakers with a lower xmax,
It's a rear loaded folded horn, and it was designed in 1956, when the average fifteen had 1mm xmax. The horn is only seven feet long, so the best it will do is about 50Hz. If you want to do a modern horn look at lilmike's designs here or the Tubas on my website.
post #5 of 10
+1 to Bill's comments. Horn subwoofers are a wonderful thing if you have the space for them, and Bill's site sells plans for some very good ones, too. But... I suspect anything along these lines is overkill for your needs.

Speaking of your needs... what do you need? You have a Polk sono-sub, but I can't find any products based on your description. You say your mains drown it out, which is odd as most subs tend to behave badly when driven too hard, the opposite of what you report. Having two helps, but not until we understand the problem...

I need more information
- what sort of amp is driving them? Power? Boost? Filters?
- how big is the room? Are there doorways to the rest of the house?
- what are you mains?
- how is the room laid out?
- what's wall/ceiling/floor construction?
- any dedicated acoustic room treatment?

And your preferences...
- what do you listen to?
- how loud do you listen
- what do you feel you're missing now?

For reference, I don't listen very loud, moreso movies than music, but I also have a wonderful room for low bass, owing primarily to construction and floorplan. A single 15" does a good job, although hanging out here always gets you to make a second, which I've done. The question is if my path would be suitable for you? If not, what do we customize?

HAve fun,
Frank
post #6 of 10
Thread Starter 
Quote:
Originally Posted by fbov View Post

+1 to Bill's comments. Horn subwoofers are a wonderful thing if you have the space for them, and Bill's site sells plans for some very good ones, too. But... I suspect anything along these lines is overkill for your needs.

Speaking of your needs... what do you need? You have a Polk sono-sub, but I can't find any products based on your description. You say your mains drown it out, which is odd as most subs tend to behave badly when driven too hard, the opposite of what you report. Having two helps, but not until we understand the problem...

I need more information
- what sort of amp is driving them? Power? Boost? Filters?
- how big is the room? Are there doorways to the rest of the house?
- what are you mains?
- how is the room laid out?
- what's wall/ceiling/floor construction?
- any dedicated acoustic room treatment?

And your preferences...
- what do you listen to?
- how loud do you listen
- what do you feel you're missing now?

For reference, I don't listen very loud, moreso movies than music, but I also have a wonderful room for low bass, owing primarily to construction and floorplan. A single 15" does a good job, although hanging out here always gets you to make a second, which I've done. The question is if my path would be suitable for you? If not, what do we customize?

HAve fun,
Frank
thanks for the response

sorry, forgot to mention the sonosub is a DIY, using a polk sub that i've had collecting dust in the garage. it is being ran by a 300w yung plate amp. no boost, crossover is around 40hz, not sure how steep the roll off is. 4 cubic ft, port tuned to 22hz. packed with fiberglass insulation.

the mains are also DIY, using 2 8" hivi m8n and B&G planar, crossover is 6db/oct @ 1800Hz, port tuned to 40hz, rear port.

was going to describe the room, but a picture is 1000words...
from the hallway leading into the greatroom

from the corner the sub is located

back corner in dining room

from kitchen sink


sounds as if the sub has a steep roll off around 35, and 20 is barely audible. what leads me to believe the enclosure is not ideal, is at high levels it will walk across the floor if standing on tile or hardwood. on the carpet the enclosure will wobble back and forth. my guess is the energy the sub is producing at low frequencies is being transferred to the box. this is making me want to build something new around the 100lb+ range so it wont move at all.
post #7 of 10
Quote:
Originally Posted by mcdizzle View Post

...forgot to mention the sonosub is a DIY, using a polk sub that i've had collecting dust in the garage. it is being ran by a 300w yung plate amp. no boost, crossover is around 40hz, not sure how steep the roll off is. 4 cubic ft, port tuned to 22hz. packed with fiberglass insulation....
...sounds as if the sub has a steep roll off around 35, and 20 is barely audible...
Let's start with that sono-sub... no problem with DIY subs, but occassionally, something gets mixed up.


This shows the contributors to a speakers's LF output. Note that the driver (black line) dives below 30Hz while the port output is rising to a peak at 22Hz. Put a sock (foam plug, Nerf football, diaper, etc.) in the port and see if removing the port contribution changes the sound. I'm betting it won't, and the fix is trivial.

I'm banking on the phrase: "packed with fiberglass insulation." You don't pack a vented box as you damp the box resonance you're tuning for.
- Line the walls, at most, with 1-2" of foam or fiberglass.
- Make sure the port mouth is unobstructed for its diameter in all directions, if possible
- test again with and without a sock in the port.

I'm hoping that the low bass is back. If not...
- the amp's SSF may be too aggressive
- you may be using a driver that's not a good match to your enclosure.

There is a lot of confusion regarding the FR of Yung amps and boost / SSF. The best data I see says -3dB point is 21Hz for unboosted amp, the right choice for your design; you want to protect the driver below resonance:
http://techtalk.parts-express.com/showthread.php?234409-Yung-or-Bash&p=1869684#post1869684

Let us know what you get!

Have fun,
Frank
post #8 of 10
Thread Starter 
Quote:
Originally Posted by fbov View Post

Let's start with that sono-sub... no problem with DIY subs, but occassionally, something gets mixed up.


This shows the contributors to a speakers's LF output. Note that the driver (black line) dives below 30Hz while the port output is rising to a peak at 22Hz. Put a sock (foam plug, Nerf football, diaper, etc.) in the port and see if removing the port contribution changes the sound. I'm betting it won't, and the fix is trivial.

I'm banking on the phrase: "packed with fiberglass insulation." You don't pack a vented box as you damp the box resonance you're tuning for.
- Line the walls, at most, with 1-2" of foam or fiberglass.
- Make sure the port mouth is unobstructed for its diameter in all directions, if possible
- test again with and without a sock in the port.

I'm hoping that the low bass is back. If not...
- the amp's SSF may be too aggressive
- you may be using a driver that's not a good match to your enclosure.

There is a lot of confusion regarding the FR of Yung amps and boost / SSF. The best data I see says -3dB point is 21Hz for unboosted amp, the right choice for your design; you want to protect the driver below resonance:
http://techtalk.parts-express.com/showthread.php?234409-Yung-or-Bash&p=1869684#post1869684

Let us know what you get!

Have fun,
Frank

the box was originally assembled without any packing. since, it has been lined. the port is unobstructed. ive tried eliminating the port, no difference. there was an increase in clarity one the box was lined, but the depth is still missing.
post #9 of 10
Am I reading right above that the HPF is set at 40HZ but the port is tuned to 22HZ?
post #10 of 10
Thread Starter 
it would be lpf I think. sub plays from 40-down.
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