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Vent too long for enclosure

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snowflake View Drop Down
Old Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2021 at 10:57am
it looks to me like the KH310 uses a sealed-back mid, so it already has its own rear chamber built into the driver

google kh310 disassembly
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2021 at 7:10am
"Now I have to find how to do that in the most efficient way possible. Do you have any advice ?"

It's really quite simple. Something like this:-


Or just use a plant pot!  LOL





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Post Options Post Options   Thanks (0) Thanks(0)   Quote infrasound Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2021 at 9:57pm
Depends how big it needs to be.. But you can use a pot or pan with epoxy, or use bolts and bracing
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ssbb1fire Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2021 at 9:37pm
I've searched a lot this afternoon about that.
You're right, I have to isolate the medium for the woofer.
Now I have to find how to do that in the most efficient way possible. Do you have any advice ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote APW Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2021 at 9:22pm
The pressure generated by the woofer will cause the mid into high excursion.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ssbb1fire Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2021 at 8:28pm
Don't take it personnaly, but as I never heard of such thing, I'd like to know more about it. Can you explain to me why the medium would be influenced by the woofer if they are in the same enclosure ?
Where have you learned that ? A book, youtube, video, forum ? To get some data about it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2021 at 10:54am
Yes - the tweeter should be ok, as they are (usually) isolated already, but the MF driver won't. You can use something as simple as a plant pot! Anything that seals it off from the LF waves within the cabinet.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2021 at 10:40am
The LF driver will interfere with the MF driver. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ssbb1fire Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2021 at 9:52am
Why does the medium and tweeted must be acoustically isolated from the woofer ? That's the first time I've heard someone tell me that.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2021 at 3:38am
Originally posted by ssbb1fire ssbb1fire wrote:

Yeah Neumann uses a sealed enclosure, and they still have an outstanding frequency response and group delay. I'm guessing their self-made loudspeakers are just incredibly well tought to allow that.
It's not rocket science they are just using bass boost to bring the lowend up.


Originally posted by ssbb1fire ssbb1fire wrote:

I'm targeting the lowest air velocity possible of course.
But I think a limit to target is 15 m/s because there will also be pressure from others drivers and that will increase air velocity (I think ?).
No, the mid and high freq drivers do not contribute to port air velocity, in fact they must be acoustically isolated from the woofer either within their own sub enclosure or by having a sealed frame.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote infrasound Quote  Post ReplyReply Direct Link To This Post Posted: 29 March 2021 at 10:19pm
You can head up to 30m/s if you have well rounded edges on a round port, in my experience.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote ssbb1fire Quote  Post ReplyReply Direct Link To This Post Posted: 29 March 2021 at 8:40pm
Yeah Neumann uses a sealed enclosure, and they still have an outstanding frequency response and group delay.
I'm guessing their self-made loudspeakers are just incredibly well tought to allow that.
I don't have the same woofers but I can try to match their data (or even try to do better, who knows ?).

I'm targeting the lowest air velocity possible of course.
But I think a limit to target is 15 m/s because there will also be pressure from others drivers and that will increase air velocity (I think ?).
15 m/s is of course when the driver is exited with its maximum power (here 100 Watts).
I have put the dimensions for wich the air velocity is 15 m/s as an attachement, can you see it ? [IMG]uploads/24032/air_velocity.png[/IMG]

Ps : I have a problem, why does WinISD keeps setting the end correction of the vent as 0.732 ??? Changing it doesn't affect anything.
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