Open Baffle Opinions - I Won't go back to Boxed Speakers Evr Again (maybe....)

Yes, the one big problem is OB’s will tell you immediately how good/bad your room acoustics are. You do "hear" the room. My listening space is not ideal. Basically a square room with the hallway down the left side Speaker and a pocket where the entrance is and a lot of Glass on that side.

You mentioned center fill as an issue. The way an OB system is supposed to work is that the rear firing information bounces off of the wall behind the speaker and thus arrives at least 10mS later than the first arrival.


If it does that the ear uses the delayed information to echo-locate, IOW to help out the sound stage. If it is less than about 10mS then the information contributes to harshness. As a general rule of thumb you want such a speaker to be at least 5 feet from the wall behind it. If less than this it won't image right because of the reasons I stated.

I wonder if the center image problem is because of the deep walls on either side of the midrange drivers. I have never seen an open baffle speaker that looked like that before. 

Ralph's (atmasphere) advice matches my experience with planar loudspeakers. The common wisdom for dipole/wall spacing is at least 3' from the front wall (behind the speakers), but that is incorrect. As Ralph said, we want the rear wave to reach our ears no less than 10ms after that from the front of the speaker. Any less than that, and the rear wave in effect sounds like a smearing of the front signal, rather than a separate event. As sound travels at approximately 1' per ms, that requires the dipole be 5' from the wall (5'/ms from speaker to wall, 5'/ms from that wall back to the speaker). 

And diffusers on that wall can help disperse rather than absorb the rear wave, a good thing if your room is on the warm side. Absorption on that wall will reduce the amount of life and energy the speaker produces, which can be good if your room is too live, and perhaps cold/bright.

As sound travels at approximately 1' per ms, that requires the dipole be 5' from the wall (5'/ms from speaker to wall, 5'/ms from that wall back to the speaker).

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The main reason I had a difficult time getting a Dipole common baffle to work.  You cannot get the timing correct front to rear. The further you get from the front wall the WORSE the timing will be not better. Lets move it closer to the wall. HOW will you ever get the timing correct. Front to rear. 

The only way is to separate the poles and add drivers to the rear pole also.

A rather sloppy way is to add a WEIR, to the inside of both monitor sections. I chose to hinge mine and set the toe on the baffle face. After the phantom speaker is kinda figured out you set the inside weirs parallel to each other.
 
What about the outside of the baffle adjacent to the outside wall, where do you think all that "out of time" stuff is going.. NOT WHERE YOU WANT.. I assure you..

So a box (It has to be a box it can't be open) has to be DEAPER and that distance from the front wall to the rear pole is the distance from the rear pole the front pole BUT only if the distance is the same. So a 20" deep speaker would be 20" from the FRONT wall. The further you pull the speaker into the room the more of a 3/D effect you get BUT loss of imaging. There will be a point where your ears will just QUIT making sense of the music. A sound effect chamber...

The numbers you quote are arbitrary. I've never heard the "within10ms rule" I've found in speaker building that it to be just the opposite.

If you want to smear the image and ruin the sound stage, let like firing drivers fire at different distances from your ear as you're proposing with a common Dipole baffle. You will get one thing "SOUND EFFECTS"

OB Look cool though..

Excellent comments from all of you once again.

Here's my responses (so far) and thanks for the good advice :

1. The side wing (a la NX-Otica's - Danny Richie - I watch his Video's too) idea is one I will try 1st and foremost. Makes sense and he gives an excellent explanation why as you mention too. It's the center focus problem. I have enough material that I can temporarily make a side wall on top of the 1.5" thick side panels of the H-Frame Woofers.
2. Build a box around just the Midwoofers leaving just the 12" Woofers and the Tweeters Dipole. Changing the crossover points from 250Hz - 2500Hz to 120Hz - 2500Hz won't be hard. I have lots of Inductors laying around that I can cobble something together. Lowering the 12" Woofers LPF  to 120Hz is a snap with miniDSP.
3. Placement currently is 5ft. exactly from the "front" (TV) wall to the back of the H-Frame Subs (5', 9" to the Midbass/Tweeter Baffle). Right side is only 2.5ft. from the room's side wall and the left side is a whopping 7", 4" from the entrance/side pocket opening/WINDOW (I have to draw it out for you Guys), Also on the right side the Speaker face a Hallway. Also the swinging doors to the kitchen are wood in a glass frame window embedded. I'll take some pics and a floor plan with room dimensions.
4. Toe-in on most box Speakers friends have lent me gives me a great center phantom image when placed straight out into a room except for a pair of KEF R3's that worked best with about 10deg of toe-in.

Thanks again for the kind words of encouragement.

BTW, I'd seen a lot of OB designs that that either integrate an H Frame stacked or not stacked Woofer cabinet below the OB Panel so my panel was tall enough (barely) to accommodate. The difference is I have no top brace/shelf in my design.

I also saw a Video with Clayton Shaw (Spatial) who suggests the upper Woofer be crossed over higher while the bottom one is X'd at 90Hz.

Baby steps but I can hear the potential.