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Post by mashaffer on May 16, 2006 22:06:27 GMT -7
How important is it that an IB have an airtight seal between the front and rear spaces? I ask because I have a nice big sliding glass door in my listening room which leads to the patio. For quick testing of drivers it would be nice if I could just slap a baffle in the opening, brace it up and maybe run some duct tape around it.
How fussy would I need to be about the seal?
mike
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Post by chrisbee on May 17, 2006 1:50:53 GMT -7
Thomas suggested to me that you would only get a narrow trough in the response from leaks. The frequency of the trough would depend on the distance from the drivers to the leak.
My own experience of having leaky french windows (glazed double doors) right beside my 4 x 15 vertical array is that you can't hear anything wrong in the bass reproduction. But you can hear the house creaking at high levels and the doors and windows are visibly moving in and out from the loads placed on them.
It can be quite good fun if you run the fast test sweep in REW. The doors and windows shaking violently is the first clue the sweep has started from 10Hz. If you know "The Haunting" you'll get the right idea. ;D
Make sure your baffle is well fixed for tests and you shouldn't have any problems. You could use long threaded rods with washers and nuts to sandwich the doorframe between your temorary baffle and your rear cross braces. Just make sure the cross braces don't interfere with the drivers.
The tendency is for the drivers to make the baffle lean backwards towards the magnets anyway. I had mine just leaning up against my "hole in the wall" for a couple of days with a safety prop. But don't try this youself. My 1.5" thick plywood baffle was so heavy with four drivers fitted it was nearly immovable.
You'll need to use T-nuts on the back of the baffle unless you have a willing helper to hold the nuts still as you bolt the drivers in place. You won't be able to reach round the back with the baffle in place in the doorway.
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jeffp
New Member
Posts: 41
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Post by jeffp on May 17, 2006 5:37:01 GMT -7
Hijack mode: Speaking of which where have you guys located T-nuts? Does HD or Lowes carry them? I looked breifly the other day at HD and didn't see them.
Thanks,
Jeff
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Post by lhreeves on May 17, 2006 8:41:17 GMT -7
I've seen them at Lowes in the specialty hardware drawers in the hardware section.
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Post by Darren on May 17, 2006 9:10:28 GMT -7
I always order them from parts express unless I don't have time.
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Post by carpenter on May 17, 2006 9:46:55 GMT -7
Home Depot carries t-nuts. They're in the screw section, where the plastic sacs of screws hang on the racks in little clear bags with green print. John  |
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Post by ThomasW on May 17, 2006 15:00:53 GMT -7
It's a great testing idea and you don't really need to worry about creating much of a seal at all. There maybe some 'chuffing' around narrow gaps, but other than that you'll certainly be able to test your idea.
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Post by mashaffer on May 17, 2006 18:25:15 GMT -7
Thank you all very much. I figured that with the pressure being so diffused that it wouldn't be a problem but I wanted to check just to be sure.
I am planning to test a pair of old organ speakers in hopes that they will at least be a step up from my little 8" AR cheapy until I can afford some more substantial drivers. The little AR runs out of steam at about 40Hz. I am using some home built OBs for my mains and so an IB sub seems somehow appropriate.
mike
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Post by ThomasW on May 17, 2006 19:34:02 GMT -7
Organ speakers probably aren't going to hold up well in this situation depending on their design....
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Post by mashaffer on May 20, 2006 5:30:31 GMT -7
Organ speakers probably aren't going to hold up well in this situation depending on their design.... xmax issues? mike |
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Post by ThomasW on May 20, 2006 7:12:55 GMT -7
Probably, organ speaker aren't known for having a high Xmax. They also usually have accordion surrounds that can 'chuff' when driven hard.
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Post by mashaffer on May 21, 2006 19:46:41 GMT -7
Thanks for the help.
Sorry, but what is Chuffing?
I realize that these may not be the best but my intention is initially only to improve on the little 8" AR box that I am currently using. It starts to run out of steam below 40 Hz. The room is only about 14' square and I don't do movies so I don't need a lot of power.
If I can get a little improvement for essentially zero outlay I will be pleased. Later on I can spring for some proper drivers.
The drivers I have were designed for open back enclosures so the Q is probably reasonable. In the organs they provided pretty high levels at low frequencies (down to around 30Hz est.). I will play around a bit with what I have and report back. Unfortunately ideal drivers are pretty darned expensive.
mike
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Post by ThomasW on May 21, 2006 20:32:39 GMT -7
Chuffing is the sound 'air' makes other than the note when you blow over the top of a bottle
You'd probably be better off using the drivers in a ported box.
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Post by mashaffer on May 23, 2006 23:21:59 GMT -7
Ahh. Thanks.
I am in the process of getting everything together to measure params on the drivers. When I get some measurements I will have a better idea of what I can do. Depending on the Vas I might try EBS. I have two identical 12" ones that I could use in isobaric.
Someday I would still like to try IB though when proper drivers are available.
mike
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Post by ThomasW on May 24, 2006 7:07:29 GMT -7
EBS designs work better for drivers that have high Xmax. IMO you'd be better off using an alignment that has a higher tuning frequency.
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