U Frame OB with side mounted drivers

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sfdoddsy

U Frame OB with side mounted drivers
« on: 11 Jul 2019, 01:55 pm »
Can anyone hazard a guess what the radiation pattern for an OB woofer section in a U frame with dual side-mounted woofers might be?

Like this:






And any advantage over a regular U frame?

matevana

Re: U Frame OB with side mounted drivers
« Reply #1 on: 11 Jul 2019, 02:22 pm »
Assuming the woofers are wired with the same polarity, it will likely throw an irregular figure eight pattern, which often requires more complex correction to address phase abnormalities. While you might be able to make an argument for force cancellation in a sealed enclosure, this would have little benefit in an open box.

matevana

Re: U Frame OB with side mounted drivers
« Reply #2 on: 11 Jul 2019, 02:41 pm »
What might be more interesting is an experiment wiring the woofers in push-pull. You would likely wind up with a dispersion pattern similar to that of the single woofer Gradient Helsinki. Many people seem to like this speaker.




sfdoddsy

Re: U Frame OB with side mounted drivers
« Reply #3 on: 12 Jul 2019, 12:15 am »
Thanks. Upon further research Danny from GR Research is proposing something similar as a base for his OB speakers.

Is it really as easy as he makes out?

https://www.audiocircle.com/index.php?topic=126112.msg1331035#msg1331035

« Last Edit: 12 Jul 2019, 02:32 am by sfdoddsy »

matevana

Re: U Frame OB with side mounted drivers
« Reply #4 on: 12 Jul 2019, 09:37 am »
You would still wind up with an asymmetrical radiation pattern with heavy cancellation in the rear. This design seems to be purpose built as stands for mini monitors that are placed close to the front wall. The best sounding systems that I have heard seem to strive for symmetrical radiation throughout most of their range, along with ample space from room boundaries.

sfdoddsy

Re: U Frame OB with side mounted drivers
« Reply #5 on: 12 Jul 2019, 10:54 am »
My long-term Orionish open baffles successfully used a flat baffle and then an H-Frame stuffed with big drivers well out from walls. Alas, for space and aesthetic reasons I'm not able to do that with this build.

I'm actually going for something that can be used close to a front wall to support (possibly physically) an OB mid-tweeter section from around 300 to below 80.

Sealed would be easy. My most recent speakers used a pair of sealed boundary woofers like the Lyngdorf DP1 but I'm not sure I can get that through again in our new home.

And I could just do a sealed mid-bass box with an OB panel above.

Tempting would be trying for cardiod with a slotted acoustic resistance enclosure like the Dutch and Dutch 8c.

The side mounted U frame felt like it might be somewhere in-between.

The ability to reverse connections and approximate the pattern of the Helsinki makes it even more appealing.

On the other hand, a simple U-frame can be sealed if it doesn't work.

Decisions.


AJinFLA

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Re: U Frame OB with side mounted drivers
« Reply #6 on: 12 Jul 2019, 11:04 am »
The side mounted U frame felt like it might be somewhere in-between.
The radiation pattern (cardioidish>dipole) is frequency dependent, including of course the baffle size. I have measurements somewhere of a design (from 2012ish) that used that exact layout, so I'll try to dig up for you.

sfdoddsy

Re: U Frame OB with side mounted drivers
« Reply #7 on: 13 Jul 2019, 11:37 am »
Thanks AJ. I'd be most curious. Do you recall if they needed as much EQ as normal dipoles?

AJinFLA

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Re: U Frame OB with side mounted drivers
« Reply #8 on: 13 Jul 2019, 12:28 pm »
Thanks AJ. I'd be most curious. Do you recall if they needed as much EQ as normal dipoles?
At lowest frequencies, because the baffle size is small relative to wavelengths, yes, or close to as much.
What bandwidth is your intended use?

sfdoddsy

Re: U Frame OB with side mounted drivers
« Reply #9 on: 13 Jul 2019, 07:40 pm »
250 down to 80hz or so.

AJinFLA

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Re: U Frame OB with side mounted drivers
« Reply #10 on: 13 Jul 2019, 08:28 pm »
250 down to 80hz or so.
80?? That's a midbass Steve.  :wink:
Almost begs the question why an opposed U? How wide is the coax upper baffle? IIRC, you're going heavily WAF with these?
If 8.5" (215-220mm) is slim enough, you could get away with multiple front mount 8s and easily get good output to 80hz with minimal sides depth

sfdoddsy

Re: U Frame OB with side mounted drivers
« Reply #11 on: 14 Jul 2019, 04:27 am »
Well, lower might also be nice.

:)

The coax is the Seas C18, but I also have a set of BG Neo 10s and Neo 3s hanging around which would require a thinner baffle.

The mid-bass drivers in question will either be my exisiting RS225s or possibly Anarchies.

Mind you, I also have some SLS10s floating around somewhere.

:)