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Multi-Way Conventional loudspeakers with crossovers

how long need a port be away from sidewalls?
how long need a port be away from sidewalls?
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Old 25th June 2018, 09:55 PM   #1
hugo stiglitz is offline hugo stiglitz  Germany
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Default how long need a port be away from sidewalls?

hi there,

I am about to finished my first DIY speakers. ATC SCM100 clones.
Now I am thinking about the bassreflex tube.
I am using an elbow piece and its a tricky to let the tube go 90 degrees up.
Since there is not enough space I have to either let the elbow go to the right or left. Now I was wondering what the distance between a sidewall and the inner port should be minimum?
Any suggestions?

Lenght ca. 14cm
Diameter 10cm

Last edited by hugo stiglitz; 25th June 2018 at 10:42 PM.
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Old 25th June 2018, 10:31 PM   #2
Qts is offline Qts
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I have told many times the diameter of the port. I would say it could be even little closer. If you have calculated length with some software, in real life pipe would be shorter. Something like 70-80% of calculated.
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Old 26th June 2018, 12:55 AM   #3
moray james is offline moray james  Canada
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I have read, though it was year ago so I have forgotten where that the air in a reflex vent will at full resonance moves 1.5 times the vent length both in and out of the vent. well worth remembering when designing a build/ The top panel of a cabinet is probably the very best pace to mount a reflex vent so long as you don't have little kids or wives with knick nacks or plants.
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Old 26th June 2018, 05:51 AM   #4
hugo stiglitz is offline hugo stiglitz  Germany
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so you say 1.5 times the length of the port should be the minimum distance between port and any wall?
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Old 26th June 2018, 08:20 AM   #5
chris661 is offline chris661  United Kingdom
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Quote:
Originally Posted by moray james View Post
I have read, though it was year ago so I have forgotten where that the air in a reflex vent will at full resonance moves 1.5 times the vent length both in and out of the vent. well worth remembering when designing a build/ The top panel of a cabinet is probably the very best pace to mount a reflex vent so long as you don't have little kids or wives with knick nacks or plants.
That depends entirely on the SPL being produced.

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Old 26th June 2018, 11:18 AM   #6
Jerms is offline Jerms  United Kingdom
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Quote:
Originally Posted by hugo stiglitz View Post
hi there,

I am about to finished my first DIY speakers. ATC SCM100 clones.
Now I am thinking about the bassreflex tube.
I am using an elbow piece and its a tricky to let the tube go 90 degrees up.
Since there is not enough space I have to either let the elbow go to the right or left. Now I was wondering what the distance between a sidewall and the inner port should be minimum?
Any suggestions?

Lenght ca. 14cm
Diameter 10cm
Have looked online for images of ATC SCM100s. The port is offet as are the mid and tweeter. I assume their port angles towards the middle of the enclosure. Assuming a built baffle with port hole made...

It is what it is. do the best job you can to find free space in the enclosure for the end of the port away from the walls.

Depending on anticipated SPL, you might want to experiment with a smaller diameter port. Small diameter = smaller length and more room to play with.

J.
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Old 26th June 2018, 11:26 AM   #7
Pano is offline Pano  United States
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how long need a port be away from sidewalls?
Darn, I used to know this. You can put it against the side wall, but it will change the length needed. But I can not remember by how much or even which direction. Someone here ought to know.
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Old 26th June 2018, 11:52 AM   #8
Qts is offline Qts
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14 cm elbow tube? Why not straight one?
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Old 26th June 2018, 12:05 PM   #9
mark100 is offline mark100  United States
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I know this is a pain to do, but I find that port tuning nuances matter enough, that building a throw away prototype box for trial and error tuning (around modeled design) is the only way to really dial in a port.
Sure, we can get lucky sometimes, with modeling working exactly.....but being able to tinker and measure rules IME. Plus, you get to try anything...

I can't specifically answer OP's question, other than to say I measure a port lengthening effect when running close to, and parallel with wall. And a can't predict effect pointing into a wall...although usually lengthen.
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Old 26th June 2018, 12:24 PM   #10
hugo stiglitz is offline hugo stiglitz  Germany
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14 cm elbow tube? Why not straight one?
for reasons
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