narrow width OBs

[zelgall]

Other than the floor space claim, is there any reason that so many of the OB designs posted recently are so narrow? It would seem that they would be severely compromised in the bass area with the typical approx 24" widths that seem popular. Would it not be better to use a 48" wide x 60" tall baffle for improved bass? If you need to EQ your design to get it to sound good, is it the best route?

[Saurav]

It's a trade-off between bass response and off-axis / polar response. The narrower baffles generally end up with more uniform off-axis response over a wider frequency range, and there is some evidence that points to that being important for overall good sound. If you're building a 3 or 4-way, one option is to use wider baffles for the woofers, and narrower baffles for the midranges/tweeters. This reduces the EQ needs on the woofer, while maintaining good off-axis response where our hearing is more sensitive to it.

That's the 'in a nutshell' version of my understanding of this, which is extremely limited compared to many of the people here.

[thomasjefferson]

With a baffle as large as you suggest, it would interfere with the sound reflected from behind the speaker, which is part of the ambient character of OB speakers. And a baffle that large would tend to radiate sound, unless it's made of concrete or lead. It would take special steps to make it sound neutral. As Saurav suggests, it's ideal to make the baffle smaller toward the top. The ideal way to extend bass response is to have an infinite baffle subwoofer.

[zelgall]

Thanks for the responses. Would a horn help the Mid/High dispersion? The idea with most horns is dispersion control.

[Saurav]

I spent about a year with a horn tweeter, dipole mid and woofer. I was running a passive crossover at the time, and my passive XO skills are minimal at best, so this isn't the best comparison. But I always felt that the soundstage was disconnected. The midrange and bass would be behind the speakers, but the treble always seemed in front. Now I have a dipole tweeter (and a DCX for a crossover, so the phase integration etc. is better), and I no longer have that issue.

So - I can't say how much was due to a poor crossover and how much due to not having a rear-firing tweeter, but that's my experience.

[twest820]

Originally Posted by zelgall

Would a horn help the Mid/High dispersion?

I'm not sure I'd use the word help. It'll change it in ways which may or may not be better depending on your design requirements and goals. Probably the most interesting area for dipole horns is H baffles which, if you think about it, are basically really badly built horns. I haven't seen any work in this space, which isn't too surprising as getting good low frequency measurements is tough without an anechoic chamber. Simulation could be useful, though.