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Suggestions for driver please.

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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 05 March 2020 at 6:16pm
Sorry, just read your post properly - you want to use these above scoops as mid-bass? That will be OK, and you're going to want a reflex box for that application.
A quick look at Hornresp tells me that if you build a 150 litre box, with a 500cm2 port 30cm long (for a tuning frequency of 42Hz) it will work well for mid-bass. If you cut it at 87Hz with a 24dB/oct filter, you should be able to put 400 watts into it without exceeding Xmax. It will then play from about 95Hz upwards, flat to about 300Hz. Max output about 124dB.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bin juice24 Quote  Post ReplyReply Direct Link To This Post Posted: 05 March 2020 at 9:32pm
A 500mm x 500mm x600mm type thing?
And just whack a hole in the front for the driver?
Should a port be round or any shape? Does it matter wheee it is?
Any chance of a fag packet sketch?
Thanks 
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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 06 March 2020 at 12:03pm
Something like that but you would need to add the port volume on, it's not part of the chamber volume. So actually 500wx600Hx600D would do it. Doesn't really matter where port goes but conventionally, under the driver on the front baffle is the place. A nice fat round over on the port edges (interior and exterior) helps with port noise.
Use a router with circle jig or compass attachment to "whack" that hole in there, and add plenty of bracing on the interior walls, or indeed right across the inside of the cabinet. Also add fibreglass or polyester stuffing to taste. 100mm or so over four interior surfaces is a good start.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bams Quote  Post ReplyReply Direct Link To This Post Posted: 06 March 2020 at 12:30pm
If you’re really interested in all the magic behind the numbers..

Just started reading in it and blown away.. steep learning curve ahead but worth it
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bin juice24 Quote  Post ReplyReply Direct Link To This Post Posted: 06 March 2020 at 2:21pm
Cheers guys,
For the port, is there any specific material to use? 3 inch down pipe?
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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 06 March 2020 at 2:45pm
Just make the port part of the box. So your front speaker baffle could be 500x500, leaving a 500x100mm gap underneath. This is the 500cm2 port exit. Then you put a 30cm long board extending back inside the box, at the bottom of the baffle. This forms the 30cm port length. Put a couple of vertical braces inside the port and the job is a good one.

edit: That might seem like a big port, but really, for PA work, the bigger the better. Smaller ports have more problems with air movement noise and excessive velocity. If the air in the port moves so much that the entire "slug" is actually expelled/withdrawn from the port, they stop working as acoustic springs and you will suddenly get problems with driver over-excursion. A big port containing a lot of air, mitigates this.


Edited by studio45 - 06 March 2020 at 2:48pm
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bin juice24 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bin juice24 Quote  Post ReplyReply Direct Link To This Post Posted: 06 March 2020 at 4:16pm
Thanks, that sounds much less complicated. I can visualise it now, just a shelf, effectively, with vertical supports.

Cheers!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bin juice24 Quote  Post ReplyReply Direct Link To This Post Posted: 01 April 2020 at 2:15pm
Update, first one nearly finished. Quite excited to hear it.
Thanks guys.

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