Home Theater Forum and Systems banner

1 - 7 of 7 Posts

·
Banned
Joined
·
361 Posts
Discussion Starter #1 (Edited)
OK, may I have a fresh start?

So I played with WinISD. I know, I didn't account for in-car effects. Please bear/bare with me? There is no 22" Fi subwoofer. So I used a Maelstrom-X to simply model 4 things. Bare with me there as well?

1: (yellow) sealed in recommended
2: (red) sealed in max available space with my dimensions 48" X 32" X 24" for 18 cubes
3: (purple) vented recommended
4: (blue) vented 14 cubes 12Hz

1st pic:
FR curve... I was surprised that the recommended looks much more desirable for my personal tastes than the 14 cubes/12Hz I originally wanted. All the way down to 12Hz I am seeing more output. Sealed is not an option.

2nd pic:
Group Delay blue is obviously much better than purple.

3rd:
Port Gain shows that even with the super low tuning, the port helps all the way up to 65Hz. So huge super low tuned still has gain from the port over both .707 and super large sealed.

4th:
blue is obviously better on velocity

5th
SPL obviously much better ported than sealed, and recommended better than super large and low (purple better than blue)

6th
I sit corrected. I thought the blue would have better excursion control than sealed. It does not. BUT, I think when lowering power input so that output is the same.... it takes less power therefore still less excursion in the blue to be equal or better than sealed. If I were to put less signal power to the blue to make it match up with the sealed output, then cone excursion should still be superior large ported to both sealed enclosures.
 

Attachments

·
Premium Member
Joined
·
1,941 Posts

·
Banned
Joined
·
361 Posts
Discussion Starter #3
That's normal because the tune is low.
With my [email protected] I never had a problem with the trunk closed. But when i was showing it off, I could get excessive excursion from 30Hz-40Hz. Shouldn't there still be less excursion or equal excursion if tuning too low verse a same sized sealed enclosure? I can't see the port actually increasing excursion.
 

·
Premium Member
Joined
·
1,941 Posts
Sorry, don have too much time tonight, but you should read Steves LLT thread again where he speaks about over excursion above tuning.
 

·
Banned
Joined
·
361 Posts
Discussion Starter #6
Sorry, don have too much time tonight, but you should read Steves LLT thread again where he speaks about over excursion above tuning.
" In the higher frequencies, when port output isn’t coming into play, output is solely a result of air displacement from the driver, just like having the enclosure sealed. Because of this, the same amount of excursion will always result in the same amount of output – all that is changed with larger enclosures and lower tunes is the sensitivity, or how much power is needed to achieve the needed excursion. In addition, since all of the negative effects of traditional ported design have been pushed deep down into lower frequencies, and less power is needed, you gain large advantages in reduced distortion. "

from the tutorial...still reading....
 

·
Banned
Joined
·
361 Posts
Discussion Starter #7
" To visualize this concept at its most extreme, model two enclosures of the same size using the same driver, one ported and one sealed. Feed them both with the same amount of power and tune the ported sub to ~2hz. From about 7hz on up, they behave identically in just about every performance parameter – FR, group delay, output, and excursion, and the port velocity from the ported design won’t yet have come in to play. What does this mean? This reinforces that when port output is not in play, a ported and sealed sub behave virtually identically. The key is to utilize that port output while minimizing the noise distortions and transient response degradation as much as possible so that they are inaudible, reaping all of the benefits without suffering the negative side effects - having your cake and eating it too. The LLT design allows you to do just this. The resulting natural FR works better in room than any other alignment in terms of achieving a flat FR naturally, and for the usable extension you are getting, the THD stays lower than sealed at any given output level, as the sealed sub isn’t getting any relief. Unless one is using enough drivers to get them flat with low distortion to 1hz at their desired playback levels while sealed (very inefficient usage), there is always room for improvement with a port. "
 
1 - 7 of 7 Posts
Top