Any issues with 2 speakers slightly facing each other? Phase?Noise?Feedback?other?...

[gytyr1968]

I had an idea to have a custom cab built for a tweed bassman where the top 2 speakers will be standard forward and the 2 bottom speakers angled for more throw to the sides.
With speakers angled outward (magnets facing toward each other, like a V front) there is less room to angle as the speaker would begin to throw into the direction of the side of the cabinet.
But with the speakers inward, you can angle them more for an extreme left and right direction.
So would there be any issues with noise or feedback or phase or other?

Here is a pic of a similar cab...

http://www.bobkeefe.com/nogrilleclothfront.jpg

[Chuck H]

That "similar cab" is a bass cab. It's just moving air. Note how the speakers are set back. Any directional advantage from mounting angle becomes moot. Cancelled frequencies will be mostly upper end so that cab may have been done that way for that very reason.

For a guitar cab I think it's a bad idea. Even a V front has some different cancellation than a standard cab if it's an open back since the backs of the speakers are angled toward each other somewhat. Of much less consequence than the fronts of the speakers of course.

The short answer is that anytime you angle speakers toward each other there will be some phase cancellation, for better or worse. And the closer the speakers get to facing each other the more phase cancellation there will be. Again, for better or worse. You won't know what it sounds like unless you build one. I probably wouldn't.

[gytyr1968]

What if the speakers were angled away from each other like a V front...not toward each other....? Are there still any issues?

[jmaf]

As Chuck H said, the backs of the speakers still talk to each other. Why not build two smaller separate cabinets, each facing one way? Too much to carry?

[gytyr1968]

Yeah, too much to carry.
I had the idea of a "suitcase" type cab where 2 tall lean cabs with 2 10" speakers in each would open on a hinge, but even that seems like it would be big and bulky.
Then you would have to use a head instead of a combo.
So now it would be a big bulky cab with an extra head to carry and plug into.

Geez, I guess I;ll just stick with the standard bassman config...haha.
I'm a dreamer with OCD and must have something unique and easy to set and forget which sounds amazing on stage.

[jmaf]

A friend has a "band of one guy" he carries around with him. This is what he uses: Fender® Products

The two speaker enclosures attach to the front and back of the amplifier / mixer, it carries much a like a large luggage (not too much bigger than a Bassman in fact)....

[gytyr1968]

But what about the Watkins Dominator? Its an extreme front angle "V"...more so than Fender. I've never heard any issues with this model extreme V front.

http://www.vintagehofner.co.uk/brita...domreissue.jpg

[MWJB]

gyttyr1968 - You seem to be wanting a tweed style circuit in a compact 5E3 chassis, with a V Front cab...possibly with reverb...have you checked out Kendrick's V-Front amp?

[Chuck H]

+ on Kendrick. Most players still really like their PTP tweedy stuff.

Just to be clear, I didn't say that V front cabs were bad. I said there would be some phase cancellation due to speaker angle in an open backed cabinet. For better or worse was my stipulation. Phase cancellation is not a bad thing of itself, it's just a physical fact of life. Phase cancellation is used all the time in electronics to improve tone and performance. It certainly could be that you really like the sound of a V front cab. Build a quicky and see. If you like it you can build a nice one for your project.

[woodyc]

The thing that changes when you have speakers near each other is that each one affects the pressure at the surface of the other. When the result is in phase, you actually get more output at those frequencies from both speakers.

Facing two close speakers inward mainly causes a midrange hump, similar to what the speaker is already doing by virtue of its cone-shape. You may like it. And if you don't you can usually dial it out with tone adjustments. You can confirm this easily using any two in-phase cabs.

P.S. I think what people above mean by "cancellation" is interference. That's entirely different and its present whichever way the speakers are pointed. It just creates an interesting spatial pattern. It doesn't add or take away sound energy.

[jmaf]

"Interference" can be of several types, one of which is cancellation when opposite phase waves couple up and cancel. Positive interference may also happen and reinforce certain frequencies.

What I know about acoustics is that even with advanced computer simulation, it's hard to get right, so for us mortals who don't have BOSE level testing facilities, experimentation is what's left.

[woodyc]

"Interference" can be of several types, one of which is cancellation when opposite phase waves couple up and cancel. Positive interference may also happen and reinforce certain frequencies...

I'm not sure what your point is but thats right, you always have a pattern of constructive and destructive interference. It makes the soundfield interesting but it doesn't affect the loudness or frequency response of the source.

The midrange hump I mentioned comes about because of some other physics -- namely the sound pressure from one source affecting the efficiency of another. Mutual coupling is another example of the same thing.

[Chuck H]

And what formulas make us aware of the phenomenon as it pertains to different cabinets and speakers? And what test equipement do we need to rationalize it's relevance? And how do we quantify any results within our chosen avocation?

I'm going with my original suggestion... Build it and see.

[woodyc]

...I'm going with my original suggestion... Build it and see.

If carpentry is a more efficient way to design cabs than acoustics, someone should have told Harry Olson -- he wouldn't have had to write those useless books.

[jmaf]

I don't think anyone is trying to disqualify the merits of acoustics here. I just said that neither I (or most folks I guess) have the necessary infrastructure to evaluate acoustic theory with the complexity it requires so ear testing is my only resource....I speak for myself, perhaps you've got better infrastructure than I...

I've got this buddy who's intent is to build a home made airplane. He's read all the books..... I just like to have a beer and watch him...