Box colourations - really ?

[Bigun]

I keep reading that Open Baffle is the dogs bollocks these days for sound quality. And a key reason is lack of box colourations. And especially the bass - afterall, many OBs use monopole tweeters. However, despite the wealth of objective data for speaker performance I've not found a link to information on box colourations. I'm wondering if it's become one of those concerns that people re-quote because they read it somewhere else. Is the benefit of OB really a lack of box-colourations or is it really all about dipole vs monopole and nothing to do with the box. How bad is box colouration when a box is built with care - good design and appropriate materials. Is the distortion down in the noise. Would anybody really build an OB just to escape from box colouration alone ? Or is it about the time delays of reflex and or TL enclosures, would the use of sealed boxes 'fix' this aversion. Or is it not about the box, but the standing waves that must occur in a BR/TL design even if the box were perfect (no vibrations at all) ?

[Cal Weldon]

Originally Posted by Bigun

Is the benefit of OB really a lack of box-colourations

Yes, I have built a few and that's the reason I do it.

and nothing to do with the box.

Everything to do with the box.

How bad is box colouration when a box is built with care

Less if built well but it's not just the box resonation that is a concern, it's the pressure waves inside.

Would anybody really build an OB just to escape from box colouration alone ?

That's the only reason I would ever doing it. Everything is a compromise.

Cheers.

[fpitas]

Assuming you control the resonant modes in the box with enough Acousta-Stuf, acoustic tile etc. (and that's a big assumption), it's very difficult to build a box that doesn't have panel resonances at various frequencies.

[chlorofille]

A little bit of box coloration can be a good thing. It gives more "body" to the sound. These days I use multi-layer stacked panel approach to building the enclosure, to push resonances as high as possible. Variable wall thickness and non-parallel walls help to mitigate standing waves.

[Bigun]

Originally Posted by chlorofille

A little bit of box coloration can be a good thing. It gives more "body" to the sound. These days I use multi-layer stacked panel approach to building the enclosure, to push resonances as high as possible. Variable wall thickness and non-parallel walls help to mitigate standing waves.

hmmm, interesting comment, but I'm not looking to add box colouration 'on purpose'. Your approach to making a good box looks superb. Did you try OB to compare ?

Originally Posted by Cal Weldon

That's the only reason I would ever doing it. Cheers.

You are the 'man' when it comes to Big speakers so when I hear you like OB then it gets me curious. What's your approach to OB - do you have a thread ?

[planet10]

Boxes suffer from the internal volume (this also gives them their benefits). Many speaker boxes suffer from just being poorly constructed from a panel modes point of view, but an OB suffers from its own set of panel resonances.

dave

[Cal Weldon]

Originally Posted by chlorofille

A little bit of box coloration can be a good thing.

I find that interesting as well.

Originally Posted by Bigun

What's your approach to OB - do you have a thread ?

It was planet10 that got me on the path. I have to admit I haven't found a way to make OB bass good for me but with mids, I will have a hard time doing anything else. Once Dave showed me the difference, the boxy sound I used to accept is now something I find unpleasant. Here are some front and back shots of 3 of them. The last one is a bunch of holes drilled in the rear but it offers the same relief. I have one set more underway.

I guess only the first one is a true OB but they give me what I need in the way of no-boxy.

[tvrgeek]

You might trip over to Linkwitz to see what is involved with OB. Not easy. There is a whole sub culture (pun intended) dedicated to IB subs. I find it is easier to build a good box that to tame an OB. Others may have more skill than I. Sigfried Linkwitz for one.

[picowallspeaker]

In Ob you simply avoid the backwave to return to the membrane , after having traveled inside the box chaotically . Because the cone is so thin and it's acoustically transparent ,specially to the lowest tones , that they don't even 'see' the enclosure

[Bigun]

I'm pretty sure I'm not as skilled as Linkwitz (or many other people who contribute on this forum) so I'll ask a related question:

Has anybody built a box speaker where they believe it has been designed and constructed to equal the 'no colouration' performance of an OB ?

Originally Posted by Cal Weldon

I find that interesting as well.

It was planet10 that got me on the path. I have to admit I haven't found a way to make OB bass good for me but with mids, I will have a hard time doing anything else. Once Dave showed me the difference, the boxy sound I used to accept is now something I find unpleasant. Here are some front and back shots of 3 of them. The last one is a bunch of holes drilled in the rear but it offers the same relief. I have one set more underway.

I guess only the first one is a true OB but they give me what I need in the way of no-boxy.

I'm a little surprised - I didn't think Dave liked OB's much. He's a man with many talents.

I like some of those speakers you've built - the one with a special section behind for the mid-driver to be OB is unusual. The first one, well it does kinda look like a coffin

The box with many holes looks cool, a giant kitchen appliance if I ever saw one ! - perhaps more like aperiodic than OB and that's something I know Dave is a big fan of. Do you find the many-holes works as well as a 'pure' OB ???