First time OB builder - Page 15

Silent Screamer · 17th September 2012, 01:57 AM

Separate but together is what I posted in my last Sketch Up pic… Are you saying that it is good to have some bass up high to disperse it better throughout the room like this? (modified photo of StigEriks setup)
I want to run a centre and surround channel (for movies only) so I can’t go crazy spreading bits around the room.

Silent Screamer · 11:24 AM

One of the challenges with an OB is trying to de-ugly it a bit, or trying to make it a bit more partner friendly... So I had an idea today that I have put down on paper.

Drawn to scale with 2 x 15", but could easily be switched to 2 x 18" without throwing the design out of whack. Drawing is 1.6 meters tall. (63")

Silent Screamer · 17th September 2012, 12:08 PM

Put one together with a pair of 18's for comparison...

puppet · 08:48 PM

Quote:

Originally Posted by Silent Screamer

… Are you saying that it is good to have some bass up high to disperse it better throughout the room like this? (modified photo of StigEriks setup)

I think it's worth trying out. ... but I was thinking along the line of separate enclosure placement. Might work well near one of the mains ... another might be placed along a wall at some distance and elevated at that location might work better still.

When I placed mine I used that trick of putting the sub/woofer at the listening position and roamed the room till the bass sounded strongest ... one sub went there. I repeated the operation for the next sub.

Silent Screamer · 18th September 2012, 12:37 AM

Couple of questions around a U or H box,
Do they need to be square? I have a router and could make them in round slice with some feet shaped on the bottom.
Do they need to be sealed both sides like a typical U or H box? If I made the tube round with a small gap all the way around I could suspend the driver in the middle of the tube.

natehansen66 · 18th September 2012, 12:45 AM

You can make it round I don't see any reason why it would behave much different. It's the depth or front to back difference that determines how it'll perform.

I wouldn't leave a gap though that will allow cancellation directly around the woofer. With an h or u frame the goal is to make the front to back distance greater for reasons stated a few posts back. I honestly don't see any good reason to go to the trouble of decoupling the woofers like you do the mid and hf drivers. I would instead make the h or u frame solid and look into damping it's walls.

Silent Screamer · 18th September 2012, 01:09 AM

Ok thanks so direct driver cancellation is of a greater priority than driver vibration isolation…
That could be easy done by just make the mounting board slice with a slightly smaller inner hole to screw the driver to.
Is there a formula or calculator to determine the length / volume front and rear?

studiotech · 18th September 2012, 03:57 AM

Quote:

Originally Posted by Silent Screamer

Ok thanks so direct driver cancellation is of a greater priority than driver vibration isolation…
That could be easy done by just make the mounting board slice with a slightly smaller inner hole to screw the driver to.
Is there a formula or calculator to determine the length / volume front and rear?

If you go with dual 15's or even 18's, there will be significant vibration once EQ'd to play flat to even 30-40hz. I would use at least a U frame to get back some efficiency. It makes no sense to run the woofers nude since the wavelengths are so long. Mids and highs I can see the case for it, but it still does not guarantee a better result than some form of baffle.

I would not attach the mids and highs to the woofer panel without more significant bracing or isolation. That kind of defeats the purpose of running nude, so maybe make the mid and high support legs straddle the woofer frame without touching. Then you've got complete isolation the the ability to move them around relative to each other.

Silent Screamer · 05:37 AM

Thinking along the lines of something like this... Just think I can make a prettier looking speaker with round shapes.

Edit:
Possibly place some rubber in between top and bottom cylinders and do something like this...

Silent Screamer · 18th September 2012, 12:51 PM

Ok so its no Rembrandt, but its not boring either...
Still could use a bit of tidying up but it does allow a 21" and a 15" to be used without looking massively disproportionate.

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18th September 2012, 12:37 AM	#145
Silent Screamer diyAudio Member Join Date: Feb 2012 Location: Sydney	Couple of questions around a U or H box, Do they need to be square? I have a router and could make them in round slice with some feet shaped on the bottom. Do they need to be sealed both sides like a typical U or H box? If I made the tube round with a small gap all the way around I could suspend the driver in the middle of the tube.

18th September 2012, 12:45 AM	#146
natehansen66 diyAudio Member Join Date: Mar 2011 Location: Rochester, MN	You can make it round I don't see any reason why it would behave much different. It's the depth or front to back difference that determines how it'll perform. I wouldn't leave a gap though that will allow cancellation directly around the woofer. With an h or u frame the goal is to make the front to back distance greater for reasons stated a few posts back. I honestly don't see any good reason to go to the trouble of decoupling the woofers like you do the mid and hf drivers. I would instead make the h or u frame solid and look into damping it's walls.

18th September 2012, 01:09 AM	#147
Silent Screamer diyAudio Member Join Date: Feb 2012 Location: Sydney	Ok thanks so direct driver cancellation is of a greater priority than driver vibration isolation… That could be easy done by just make the mounting board slice with a slightly smaller inner hole to screw the driver to. Is there a formula or calculator to determine the length / volume front and rear?