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Can't get rid of port noise  

post #1 of 15
2/21/06 at 9:04pm
Thread Starter 
I built a 4.5cu box with an infinity perfect kappa 10.1 driver, and had a 3" x 11 port.

at about 24Hz or so i got awful port noise at volume.. then i put in a 4" x 16 port because i calculated i needed a 3.7" min port to avoid noise... well at 22Hz and a little higher on the volume (95-100db @ 1m) i get noise again.. and its very noticible... stays until about 25hz.... if i lower the gain it goes away.

question is, is this because of the port or the driver? im not 100% what port noise is but i know this is noise.. and its coming from the port, so im guessin im on the right track. id try out a 6" port but the length would get to be an issue and it would be hard to pipe it thru the bracings... where can i get some flexible tubing? i hate working with PVC bends and the such.

i dont want to keep going bigger on the port diameter unless i know for a fact thats what it is.

any ideas on a PR? when i plug in the numbers for 2 of the partsexpress 10" cheap PR the results dont look as good on winisd...steep drop at 28-30hz. i want it deeper... thats why i went with a 4.5 box.

am i just asking too much from this current driver?

edit: actually i can get 22hz on the winisd if i added 100g to each PR... but thats another $50 to get the PRs

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post #2 of 15
2/22/06 at 9:03am
this occurs when the air velocity is too high of the air leaving the port is too high. You could also try using flared ends

You should try using unibox to determine the optimal port length and size.
post #3 of 15
2/22/06 at 2:48pm
Thread Starter 
the ends were flared as well, forgot to mention that. unibox syas i need a massive 6" port while other programs only said 3.7" . quite the difference.

no way i can fit a 6" x 32" port in there.
post #4 of 15
2/22/06 at 2:53pm
Quote:
Originally Posted by irfan
the ends were flared as well, forgot to mention that. unibox syas i need a massive 6" port while other programs only said 3.7" . quite the difference.

no way i can fit a 6" x 32" port in there.
unibox is generall the prefered program to use as it is know to be more accurate. my 220L tempest used dual 4" ports...12" long. Try playing around with the number of ports as well
post #5 of 15
2/22/06 at 3:04pm
Sorry to hear about your problem. Any chance of 2 4" ports or 3 3" ports? The air coming out of 2 4" ports would still be faster then 1 6" but they would be shorter. You could also go with a slotted port but you would have to build a new box.

I will have to look at this when I get home. I can't believe a 10" is giving port noise out of a 4" flared port. Thats too bad.
post #6 of 15
2/22/06 at 3:04pm
you also might be asking a little much of that 10" driver...do you have the T/S params, I am not familiar with it. in a vented box, as you get near the tunning frequency, the airspeed is going to go out of the roof.
post #7 of 15
2/22/06 at 3:38pm
Thread Starter 
THIELE-SMALL PARAMETERS
VOICE COIL DC RESISTANCE: REVC (OHMS) . . . . . . 4.11
VOICE COIL INDUCTANCE @ 1 KHZ: LEVC (MH). . . . . . . . 2.96
DRIVER RADIATING AREA: SD (IN2) . . . . . . . . 53.40
SD (CM2). . . . . . . 346.00
MOTOR FORCE FACTOR: BL (TM) . . . . . . . . 16.64
COMPLIANCE VOLUME: VAS (FT3). . . . . . . . . 1.36
VAS (LITERS). . . . . . 32.13
SUSPENSION COMPLIANCE: CMS (µM/N) . . . . 189.00
MOVING MASS, AIR LOAD: MMS (GRAMS) . . . . 166.71
MOVING MASS, DIAPHRAGM: MMD (GRAMS). . . . 163.01
FREE-AIR RESONANCE: FS (HZ) . . . . . . . . 28.35
MECHANICAL Q: QMS. . . . . . . . . . . . 8.83
ELECTRICAL Q: QES . . . . . . . . . . . . 0.44
TOTAL Q: QTS . . . . . . . . . . . . 0.42
MAGNETIC-GAP HEIGHT: HAG (IN) . . . . . . . . . 0.39
HAG (MM) . . . . . . . . 9.80
VOICE-COIL HEIGHT: HVC (IN) . . . . . . . . . 1.50
HVC (MM) . . . . . . . 38.10
MAXIMUM EXCURSION: XMAX (IN) . . . . . . . . 0.56
XMAX (MM). . . . . . . 14.15

Box: 4.5cu-ft ..about 127L?

If i go with 2 of the 4" ports.. in unibox is the portlength the TOTAL port length or the length of each port?
post #8 of 15
2/22/06 at 4:19pm
Quote:
Originally Posted by irfan
THIELE-SMALL PARAMETERS
VOICE COIL DC RESISTANCE: REVC (OHMS) . . . . . . 4.11
VOICE COIL INDUCTANCE @ 1 KHZ: LEVC (MH). . . . . . . . 2.96
DRIVER RADIATING AREA: SD (IN2) . . . . . . . . 53.40
SD (CM2). . . . . . . 346.00
MOTOR FORCE FACTOR: BL (TM) . . . . . . . . 16.64
COMPLIANCE VOLUME: VAS (FT3). . . . . . . . . 1.36
VAS (LITERS). . . . . . 32.13
SUSPENSION COMPLIANCE: CMS (µM/N) . . . . 189.00
MOVING MASS, AIR LOAD: MMS (GRAMS) . . . . 166.71
MOVING MASS, DIAPHRAGM: MMD (GRAMS). . . . 163.01
FREE-AIR RESONANCE: FS (HZ) . . . . . . . . 28.35
MECHANICAL Q: QMS. . . . . . . . . . . . 8.83
ELECTRICAL Q: QES . . . . . . . . . . . . 0.44
TOTAL Q: QTS . . . . . . . . . . . . 0.42
MAGNETIC-GAP HEIGHT: HAG (IN) . . . . . . . . . 0.39
HAG (MM) . . . . . . . . 9.80
VOICE-COIL HEIGHT: HVC (IN) . . . . . . . . . 1.50
HVC (MM) . . . . . . . 38.10
MAXIMUM EXCURSION: XMAX (IN) . . . . . . . . 0.56
XMAX (MM). . . . . . . 14.15

Box: 4.5cu-ft ..about 127L?

If i go with 2 of the 4" ports.. in unibox is the portlength the TOTAL port length or the length of each port?

the length of each port..when i get a few min ill run those numbers
post #9 of 15
2/22/06 at 4:31pm
Thread Starter 
well it seems id need 30inches per 4" tube apparantly. thats a tight squeeze again.

im thinkin of selling the driver on ebay (just pulled it out of my car anyways) and go with a dayton 12"... and build a new box for it all together. maybe just a 1ftx1ftx4ft box to slip behind the couch. although i do prefer it out in the open i seem to get best response from right around the couch. maybe a piano black finish with an aluminum woofer (any $100 12" aluminum woofers around?). there is a 12" version of the current driver i have thats aluminum also.. but again it is designed for a car, i think the car design is ruining the HT performance?
post #10 of 15
2/22/06 at 4:42pm
using a 4" port about 25.25" long would work. In a 127l box that brings the tune to about 25hz, assuming i didnt make a typo anywhere....but im not at all happy with the FR curve that unibox spits out.

where did you get the volume of the box from?
post #11 of 15
2/22/06 at 4:46pm
Quote:
Originally Posted by irfan
well it seems id need 30inches per 4" tube apparantly. thats a tight squeeze again.

im thinkin of selling the driver on ebay (just pulled it out of my car anyways) and go with a dayton 12"... and build a new box for it all together. maybe just a 1ftx1ftx4ft box to slip behind the couch. although i do prefer it out in the open i seem to get best response from right around the couch. maybe a piano black finish with an aluminum woofer (any $100 12" aluminum woofers around?). there is a 12" version of the current driver i have thats aluminum also.. but again it is designed for a car, i think the car design is ruining the HT performance?
if it was me, id go the dayton route....whats your budget?

Alot of the car audio drivers dont do to well in HT. I'd say that kappa is probably not designed to get the extension that your looking for. The FS at 28.3hz is pretty high.
have alook at some more of the dayton or other popular DIY drivers...ascendant, soundsplinter, etc.
post #12 of 15
2/22/06 at 4:54pm
graphs
LL
LL
LL
post #13 of 15
2/22/06 at 5:01pm
Thread Starter 
well if i sell the kappa and the old sub i have i think id get about 120 bucks out of that... should be enough for a dayton driver and a sheet of MDF. in your diagrams its seems u left the power at 150W... i have a 240W amp and with that the peak excursion is reached at 22.9Hz. even with a dayton 12 the peak seems to be reached early around 30hz ... fluctuates depending on box size.

i chose the 127L because i wanted a box that could go deep without needed a ton of piping inside it. it was still someone arbitrary but there was no way i coudl tune it to 21hz and keep the size small.
post #14 of 15
2/23/06 at 9:08pm
Thread Starter 
well i havent changed anytyhing, just laid it on its face and turned the gain down a little... no more port noise (at least not that i can hear)... maybe the loud volume that the noise it at ends up washing it away? its mostly disappeared tho so it'll hold me over til i get some free time to build a new box/driver. thanks for the help tho i appreciate it.

i got a bfd 1124p to help with the equalizing... tinkered for 2 hours trying to get the house curve going... til i found out i could simulate the whole damn thing in roomEq wizard:) then it took a whole 10min to do :)

quick Q: when u guys do a measurement of the room via SPLmeter hooked to RoomEQ do you just do a sine sweep or do u take individual measurements (1,2,5 Hz increments?)
post #15 of 15
2/24/06 at 6:42am
Quote:
Originally Posted by irfan
well i havent changed anytyhing, just laid it on its face and turned the gain down a little... no more port noise (at least not that i can hear)... maybe the loud volume that the noise it at ends up washing it away? its mostly disappeared tho so it'll hold me over til i get some free time to build a new box/driver. thanks for the help tho i appreciate it.

i got a bfd 1124p to help with the equalizing... tinkered for 2 hours trying to get the house curve going... til i found out i could simulate the whole damn thing in roomEq wizard:) then it took a whole 10min to do :)

quick Q: when u guys do a measurement of the room via SPLmeter hooked to RoomEQ do you just do a sine sweep or do u take individual measurements (1,2,5 Hz increments?)
sweep
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