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Multi-Way Conventional loudspeakers with crossovers

Port Sizes and Effects???
Port Sizes and Effects???
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Old 30th August 2002, 01:34 AM   #21
kelticwizard is offline kelticwizard  United States
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Port Sizes and Effects???
Quote:
Originally posted by Claus, of Denmark
Make it easy, do like the rest of world. Use millimeters. What is 250 million people compare to 5 billions.
Ahem ahem.....I notice that your very own countrymen at Peerless of Denmark use inches in their product descriptions!
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Old 30th August 2002, 06:58 AM   #22
Claus is offline Claus  Denmark
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Well Well

We do a lot to please But under the skin it's millimeters.

CSX 257 SWR 39 115 SDX 4L AL 8 ohm

Diameter 257 millimeter 10" would be 254millimeter
Voicecoil 39 millimeter 1―" would be 38millimeter
Magnet 115 millimeter

So if you get used to millimeters, you will get more informations.

mvh
Claus
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Old 30th August 2002, 08:31 AM   #23
Xyberz is offline Xyberz
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Is there some way to bend ports, or use something that flexes and use that as a port? I'm looking to put a 4" port into a box that is only 4 3/4" in depth. As you can tell, with the speaker in the box, there is not 4 inces of space availabe in depth for a port. Also there is the consideration of maybe it not sounding properly? I hope someone can help me on this.
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Old 30th August 2002, 09:17 AM   #24
pinkmouse is offline pinkmouse  Europe
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Port Sizes and Effects???
Xyberz, you are aware that the volume that the port takes up in the box has to added to the total volume of the box, for example,

10 litre calculated volume + 1 litre port volume = 11 litre box

In bigger boxes this usually falls in the 10% fiddle factor you get in any box calculations, but for the small boxes you are planning, it could be a significant part of the box volume.

There is no reason you could not use flexible tubing for the ports, but it should be as rigid as you can find, and try not to have too many or too sharp bends,as this will affect air velocity in the port.
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Old 30th August 2002, 10:36 AM   #25
navin is offline navin  India
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usually add 30% for small boxes for port bracig etc. actually i add 20% for sealed boxes as there is no port and enough stuffing to make apparent volume 10% more.

cheers.

sealed boxes are:

1. easier to make
2. more tolerant of difference is real parameters v/s published ones.
3. tighter bass
4. smaller box

i know bass reflex and TL have their advantages but for me the 4 listed above are important enough for me to stick with sealed. (I have built a bass refex box using 2 8" Focal 8N515, a TL using Vifa M26WR, and 4th order 3 chamber band pass using 2 Peerless 831727 10" so it is not have not tried other designs.
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Old 30th August 2002, 01:31 PM   #26
kelticwizard is offline kelticwizard  United States
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Port Sizes and Effects???
Quote:
Originally posted by Xyberz
Is there some way to bend ports, or use something that flexes and use that as a port? I'm looking to put a 4" port into a box that is only 4 3/4" in depth. As you can tell, with the speaker in the box, there is not 4 inces of space availabe in depth for a port. Also there is the consideration of maybe it not sounding properly? I hope someone can help me on this.
Generally, white PVC plumbing pipe is used for ports. If you go to your local home impovement or plumbing store, you will see that they sell elbows of both 90 degree and 45 degree angles designed to fit over PVC pipe. The elbows' radius of turning is large enough so that they don't cause air flow problems-at least, I never heard of anyone having any air-flow difficulties when they use pre-made elbows.

That shoud set you up. If you use flares, they probably won't fit over the end of the elbow-the elbow is expanded to fit over the pipe-so make sure there is some pipe sticking out of both sides of the elbow when you plan your box.
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Old 30th August 2002, 06:12 PM   #27
Pete Mazz is offline Pete Mazz
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Try an electrical supply store. Ask for plastic sweep elbows. They're available in a lot of diameters. The larger the diam, the larger the sweep.

Pete
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Old 8th November 2018, 08:32 PM   #28
novoros1 is offline novoros1  United States
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Quote:
Originally Posted by Claus View Post
Hi,
I need your help. I have the cabinet with two ports L=3 1/2. OD= 3 5/8 ID= 3 7/16. I can't get the tubes of this size I have tube OD= 4" what length of two tubes should I have cut to get the same result as the originals. Thanks in advance.

About vent calculation



This is not true.
if you increase the area of the ports, you have to increase the lenght too. This has nothing to do with the volume of the port.

If you donīt do that the tuning frequency will increase,

Lv = (23562.5*Dv^2*Np/(Fb^2*Vb))-(k*Dv)



where,

Dv = port diameter (cm)
Fb = tuning frequency (Hz)
Vb = net volume (litres)
Lv = length of port (cm)
Np = number of ports
k = end correction (normally 0.732)

Best regards

Claus
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