|14th March 2013, 03:41 AM||#31|
Join Date: Mar 2013
Would I lose SPL or they would have more port noise?
1. two 3" ports 17" long tuned to 18hz
2. two 3" ports 15" long tuned to 19hz
Sub Driver should arrive eventualy Amp Ill order when I decide port size
|15th March 2013, 12:16 AM||#32|
Join Date: Mar 2013
currently I'm deciding between a Flared port & a Vented port
Crossover is build into plate amps correct?
Sub-woofer itself should arrive tomorrow
rest of parts Ill order sometime soon after I start box.
|23rd March 2013, 04:44 PM||#33|
Join Date: Feb 2006
Do you have the subwoofer already (Stereo Integrity HT 15")? Does it look good?!
Now ports size (internal diameter/length) they are related to the tunning frequency. That's a constraint of the bass reflex type of enclosure. Very low tunning frequency gives a gigantic almost impossible port length (several feet). To work in the limits of the practical, one dimension of the enclosure would be the max length of the port, that's what I have in mind. I need to know the 3 dimensions (of the enclosure) available or the one for the port you choose to be located (H, L or D internal of the box).
Now (example) for a Ported = 5ft³ tuned to 22 Hz
(5ft³ = 141.58L)
(note: the problem with tunning FB = 16.9 Hz is a port so many feet long that it doesn't fit inside the subwoofer enclosure and it's quality is bad.)
Max tunning frequency FB = 20 Hz.
So this is very critical if you do or don't have the space inside the box for this port. (When you don't have the electronics to modify the output curves of a speaker) The best bet, in this case, is to make say an ideal box with ideal (or more practical in this case) tunning with higher Fb.
It doesn't matter if you use a box from 3.5ft³ (99L) to 6ft³ (170L) it takes a max. tunning of 20Hz for a close to ideal alignment and with this driver.
1. Let's say 5ft³ (141.58L) tunned to FB = 16.9 Hz (ideal),
port 4", length ~20", air speed very high @70.4 m/s (max. 25.5 m/s).
(very difficult to work with the low frequency tunning)
2. 5ft³ tunned to FB = 20 Hz
port 4", length ~14", air speed very high @95.8 m/s (max. 25.5 m/s).
3. (Now with 2) 2 ports 4":
port 4"(x2), length ~29", air speed high but better @47.9 m/s (max. 25.5 m/s), results in a very long and bad port length.
4. Let's make another test with the port with a rectangular port:
port 1"x20" (HxW), length 15", air speed very high at high volumes 95.2 email@example.com dB but ok at low volumes 13.7 firstname.lastname@example.org dB.
So, I would use this alignment with this port if testing assure me it's ok.
5. Let's make yet another test with another rectangular port an different alignment:
Ported = 5ft³ tuned to 18 Hz
1"x20" (HxW) rect. port, length 19" (L), air speed high at high volumes 78.5 email@example.com dB, ok at low volumes 15.4 firstname.lastname@example.org dB.
So, after all this is my last simulation for such an alignment and the dimensions of the port system with the Stereo Integrity HT 15" in response to your PM.
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