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#1 |
diyAudio Member
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Hello,
I am currently designing a TQWT for a friend, based on a Supravox 165LB. (I gave up the horn, way too big !!) The previous enclosures I designed all used a frontal port, a solution that always gives satisfaction due to the synchronised driver and port waves. My friend has a small room, and I'd like to take advantage of corner and floor loading in my design, involving rather a back or side port than a frontal port. But I'm quite afraid to encounter phase problems and severe dips and peaks with a port that is not on the front of the enclosure. I have also heard using a rear port could reduce the midrange output through the port, which is a very good thing. I'm rather looking for a side port, because it doesn't involve leaving space behind the enclosure. So I'm asking you, port experts, ![]() ![]()
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#2 |
diyAudio Moderator
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Wavelengths at the frequencies the port is operating at are fairly long, so positioning isn't really a problem. The only issue I can see with side mounting ports is that box width is usually the smallest dimension, so if it's long, you might need to put a bend in the port.
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Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff? |
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#3 | |
diyAudio Member
Join Date: Mar 2003
Location: British Antarctic Territory
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Quote:
Rear-firing the port gives a little more boundary reinforcement for lows (expecially if near ground). It also attenuates some of the high freqs that aren't supposed to get through the port, but do. Unless you plan on having the enclosure flush against the wall, I think rear-firing is the way to go. |
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#4 |
diyAudio Member
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OK I'll try the side port, so.
Length of the port won't be a problem, I find it even really short on my TQWT. TLs often have big and short ports. Concerning the shape of the port, which is prefered ? A tube, a slot, a vertical slot, several tubes ? (my port will not be at the end of the transmission line, but 8" above the the bottom.)
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#5 | |
diyAudio Member
Join Date: Mar 2003
Location: British Antarctic Territory
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Quote:
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#6 |
diyAudio Moderator
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Yes, round should be fine. It's also easier to tweak if you need to!
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Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff? |
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#7 |
diyAudio Member
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OK thanks a lot.
I'll go to a DIY shop this week end to see which diameters of PVC pipes are available. Cheap, solid and acoustically neutral ![]() Just what I need ![]() Greets !
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#8 |
diyAudio Member
Join Date: Mar 2005
Location: UK
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Just to add my vote for the round ports. Much less ripple as a rule than a slot port. Remember not to place it right at the bottom of the cab. though. 3" - 4" up is usually a good place to start.
Cheers Scott
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#9 |
diyAudio Member
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Yes, I placed the port above the bottom.
I just have a little question about the speaker's position : How much space do you usually leave between the port and the wall, not to get a stuffy sound and uneven response ?
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#10 |
diyAudio Moderator
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Good rule of thumb is leave at least the diameter of the port to the wall or any other obstructions. That also applies internally.
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Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff? |
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