As fate would have it, I addressed this in another thread today: Help/Evaluation of first sub build - diyAudio
Right, for a given vent CSA, longer = lower tuning.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Which I checked out. Thanks Again GM for all your kind support and patience as sometimes it takes me a little time to fully understand your explanation/meaning and you always remained patient with me.That in it's self means a lot to me. :thankU: JohnOriginally Posted by GM
I should be bringing the cabs home maybe by the weekend so the fruits of your labor will be coming to fruition.I promise to send many,many pictures.:2thumbsup: :lollipop: Thank You Greg !!!!!!
You're welcome!
Yeah, I get this a lot, but I'd rather educate than just answer a specific Q in the hope that it might do some good to more than just the one person/situation.
Looking forward to your impressions and final tuning choices.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Hey GM, OK I've been doing some calculations,shopping around, and my Home Depot don't carry a 6" PVC I have to check with a plumbing supply house if they have a 6" pipe available.
The first dims you gave me of the rectangular port on the front baffle came out to a area of 50.625" (16.875" x 3") with a vent length of 4" for a 25 Hz tuning
Now the second Dims of the 2 6" PVC pipes (Side Ports) comes out to a (CSA) of 56.52" (pi x 3 x 3)which will be approx. a difference of 5.895" of area. now will I need to shorten length of the port ??
Also would I be able to use 2 ports of different size if need be. A 4" pipe(vent) with a 2" pipe(vent) above that.(Over & Under) with the larger port on the bottom of course.
I would of course rather the one 6" PVC pipe.I didn't have time to get to the Plumb.S.H. in time to check if they have it. Thanks !
Greets!
Bummer, last time I looked, the local Lowe's had it.
No, all else =, pipe length increases with increasing CSA, so would be around 5" normally.
Only if the smaller of the two was big enough for a low vent mach, so for all practical purposes the answer is 'no'.
One 6" is way too small in theory. Anyway, since it will be on the side and not quite so obvious if on the side closest to the room side wall, might as well just use an 8" cardboard tube: Ash Grove 8 in. Form Tube AG - 489.08.04 at The Home Depot
Since it's waxed on the inside, forget painting it/whatever, especially since you will probably have to add a stretched cloth or similar grill over it to critically damp it.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
No it is actually 2 - 6" pipes/vents on each side of cabinet so the area would be 56.52" of vent area.That is almost 6" bigger than the front baffle vent that was 50.625" That is too small still.If I have to use bigger ports for the side I would just assume put the rectangular 16.875" x 3" port on the front baffle with 4" length 3" from bottom of cabinet.Veneering is almost done.Tops are coming out of the press.
Added: I found these what do you think they are a bit pricey though as i would need 4 of them.But I like them, they are already black and wouldn't need to paint them.
http://www.parts-express.com/pe/show...number=268-354
I think an 8" vent is huge and wouldn't look right remember the sides are only 10" with a 6" on each side would look a little better IME
GM I'm using two 6" ports on each side will the length still be 4" or will it be longer ? I figured the (CSA) of the two ports to be 56.52" Thanks !
These port tubes are 17" so can be cut any length, I guess I can tune them when I get them home.They should be delivered by end of week from Parts Express.And cabinets to follow middle of next week they should be a done deal.
Precision Port 6" Flared Port Tube Kit | Parts-Express.com
Again, (1) 8" dia. = 8^2*pi/4 = ~50.27"^2 pipe is sufficient, ergo (1) 6" dia./side is plenty: 6^2*pi/4 = ~28.27"^2*2 = ~56.55"^2 and since this is a corner loaded cab I'm hoping that the additional calculated length due to the additional frictional losses of multiple vents with a larger total area (CSA) will be shortened back to the 'ideal' 4", but only measurements will 'tell the tale', so if a potentially few Hz higher Fb is a big deal to you, then start with 5-6" long vents and shorten them if these tune them too low.
BTW, measured the 6" rated Schedule 40 pipe at Home Depot yesterday and it was 6.125" i.d., making them even larger/longer, so wouldn't hurt to accurately measure yours just in case.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
OK GM, I was getting confused about the 8" pipe you are talking about.Since I'm not using 8" I'm going with 6" flared port tubes(Kits).And I must admit I was quite a bit confused on what size you were actually trying to tell me.Were just waiting for them to be delivered now from PE. But I'm putting 1 vent on each side of cabinet so there will be 2 vents per cabinet 4 total for both cabs and they will be 3" from the bottom. My biggest worry was that they would be too big.WRT the higher Fb I would be happy with them being close to 30 Hz or thereabouts it doesn't have to be exact.I think the cabs will have plenty of bass.
These port tubes are 17" long so I can shorten them up quite a bit as you recommend 5-6" I think I will start with them long as I can always cut them down,but can't add it back and at almost $32 each I don't want to make a mistake.
Again I was worried that 2 round 6" ports on each cabinet was going to be too big.That was what I guess I was just trying to verify.But as you say it will be fine as I will be tuning in room by shortening the ports.See I told you about your patience.First Class Thanks GM !! :2thumbsup: :thankU:
The 8" was the original design, so when we went to side firing, I spec'd the nearest oversize.
FYI, The dual 6" dia. pipes are big enough that flaring isn't required unless you under-size them. Also, flared vents typically must be a lot longer for a given tuning, so with no way for me to sim them accurately, you're on your own beyond the ROT of adding the length(s) of the flare(s) to a straight pipe's calculated or measured length.
Hmm, if the basic pipe is around 6" i.d., then you may need only one/speaker since it's flared.......
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
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