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Old 15th August 2012, 06:01 PM   #591
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Box colourations - really ?

Post 215

I find this interesting and wonder what would be the effect of adding this acroos the panels of the PHY baffle? Are these reflections a non issue with OB? It would seem that this might get you closer to an IB concept. Sort of a hybrid BIB. It my mind, the baffle begins to look like the Acapella from Troels Graverson's site. This thought could be in line with the DUMB part of the title of this thread.
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Last edited by buzzforb; 15th August 2012 at 06:03 PM.
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Old 15th August 2012, 06:07 PM   #592
tsiros is offline tsiros  Greece
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Quote:
Originally Posted by Melon Head View Post
Should this equate to better sound?
jumping right to the crux of the matter

you know better than i do that the question is absurd... a speaker can not be judged by itself. you need to factor in the room that will receive it and the amp that will drive it.

you try out different materials and positions and orientations and observe when it sounds better.
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Old 15th August 2012, 06:09 PM   #593
ra7 is offline ra7  United States
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Speaker dave contends that back reflections are harder to deal with in an OB. You have to pretty much treat the entire backwall and even then you may not absorb the backwave fully. A closed box in comparison can absorb the backwave to 99%. Reflected sound coming from the same direction, something that happens in OB when the sound reflects from the wall behind the OB, is perceived as a change in frequency response, i.e., not good.

All this good science not withstanding, there is something to be said about OB sound. At the very least, it's different. And fun.

In my brief experience, after using fiberglass and following the instructions from Speaker Dave, the sound improved a lot. As did the measurements. It's a coloration that you know was there after it is removed.

What's a PHY baffle?
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Old 15th August 2012, 06:24 PM   #594
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ITs basically OB with wings that are angled back. Looks like an open back version of the Acapella on troels site. Ra7, Are you saying you like boxes over OB? No political correctness here. If you have an opinion, state it, and put on your helmet and prepare for the Tomatoes
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Old 15th August 2012, 06:28 PM   #595
tsiros is offline tsiros  Greece
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back reflections with an OB aren't supposed to be absorbed. if you're to do that, you might as well do IB.
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Old 15th August 2012, 06:30 PM   #596
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hahaha... no, I have no opinions... I was doing OB a year ago and enjoying it immensely... since then, I built the paper mache horns (Building John's Paper Mache Horns) and OB is no longer an option because of the efficiency and excursion trade-offs.

I see where Speaker Dave is coming from and maybe if I listened to my old OBs again, I might find they are colored too. They were certainly a lot of fun and very easy to build.
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Old 15th August 2012, 06:36 PM   #597
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Quote:
Originally Posted by tsiros View Post
back reflections with an OB aren't supposed to be absorbed. if you're to do that, you might as well do IB.
That's one line of thinking. Reflections arriving from the same direction as the direct sound are perceived as a change in frequency response, and hence, not preferred. Reflections from the side are perceived as added spaciousness and are preferred. OBs have least radiation to the side and max radiation to the back. By toeing them in heavily you can angle some of that radiation to the side, but you would still want to absorb the one coming from directly behind the speaker. And if you analyze the angles, it turns out that its a large portion of the back wall.

Melon, this is not meant to detract you from your endeavors. You've given us a lot of good info.

Last edited by ra7; 15th August 2012 at 06:40 PM.
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Old 15th August 2012, 06:38 PM   #598
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Quote:
Originally Posted by ra7 View Post
hahaha... no, I have no opinions... I was doing OB a year ago and enjoying it immensely... since then, I built the paper mache horns (Building John's Paper Mache Horns) and OB is no longer an option because of the efficiency and excursion trade-offs.

I see where Speaker Dave is coming from and maybe if I listened to my old OBs again, I might find they are colored too. They were certainly a lot of fun and very easy to build.
So you use monopole woofers with high compression horns? Would be nice to see your setup. I have seen carpenter's horns. Very nice.

Quote:
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back reflections with an OB aren't supposed to be absorbed. if you're to do that, you might as well do IB.
That was the point of the question. IB from this driver or other larger diameter woofers would be VERY large. It would be interesting if you could cheat and get an IB out of something smaller. The BIB is nothing but a large box that is open ended. Measures miserably, but suppposedly well regarded.
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Old 15th August 2012, 06:40 PM   #599
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by ra7 View Post
hahaha... no, I have no opinions... I was doing OB a year ago and enjoying it immensely... since then, I built the paper mache horns (Building John's Paper Mache Horns) and OB is no longer an option because of the efficiency and excursion trade-offs.
I really like those horns, but I don't think they are very practical and an OB would suit you better. The good news is that I'm willing to take those horns off your hands, just PM me when you're ready
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Old 15th August 2012, 06:42 PM   #600
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Quote:
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so... it sounds better without any acoustic dampening?!
I have not actually listened yet.
With accoustic insulation there is a 5dB reduction between 100Hz and 200Hz but why? Is it because there is less energy available to excite the walls into their natural resonant frequency, or is it just reducing the amount of energy being reflected back out of the cone?

It does not matter really however I would like to understand a little bit more

Last edited by Melon Head; 15th August 2012 at 06:47 PM.
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