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

https://photos.app.goo.gl/cg64ScibP75b1YVF6

My very last DIY effort after doing the DIY Speaker thing (for myself only) for 35 years (only 5 pairs built in that time). These are my best effort WRT to sound quality. Bass down to 30Hz, sweet treble and midrange to die for.

All Parts Express Drivers. GRS Planar, GRS 12" (Qts = 1.27) Woofers, and Dynavox 5 1/4" midrange/midbass Drivers. All in $600. Still some tweaking to to on the Cabinet and the Crossovers. A simple 1st Order 16uF Sonicraft Capacitor on the Tweeter and a 2nd Order Bandpass on the 3 Dynavox Drivers. The H-Frame Woofers section is powered by an ICE Power Class D (1000W@4 Ω). Two for stereo of course. MiniDSP dialed in for a 250Hz Linkwitz-Riley 4th Order LPF, the Bandpass is 250Hz - 2500Hz, and the Magnetic Planar BG knockoff by GRS takes over at 2500Hz. No L-Pads anywhere !

My question is what is the Phantom Center like ? Mine is not as focused as I’d like it to be. But my God, the soundstage, imaging, front to back depth is amazing. Clarity like I’ve never heard before form a Box Speaker and the Bass is like I’ve never experienced. No Box Boom. 40Hz all Day and I can hit 30 Hz with very little attenuation

rajugsw
timlub
2,041 posts
 
Seal the midbass in a small stuffed box, change the crossover between the mids and woofers to 120. 2500 is fine on top. You are getting that free air woofer out of the vocal range. Leave the woofer free air. Everything will snap into place instantly.  You can dial it in and try it without the midbass baffle, but you will have a hole in your frequency,  the Dynavox won't go down to 120 without the box.  
Be careful experimenting,  use low power, the Dynavox have an xmax of 2mm.  They won't like going down in free air.  
jaytor's avatar
jaytor
766 posts
 
Just noticed that autocorrect changed "wing" to "wrong" in my post. Meant side wing on the inside side of the speakers. 
atmasphere's avatar
atmasphere
11,938 posts
 
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.
roxy54's avatar
roxy54
8,066 posts
 
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. 
bdp24's avatar
bdp24
9,923 posts
 
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.
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