Open Baffle Epiphany!

Made my first set of OBs today using a pair of Bozak B800Bc and a couple pieces of plywood a neighbor gave me. The baffles wound up 22" square because I had one piece that size and one a little bigger. They're not near big enough to give good bass, but the mids and highs are incredible. Now I know what you guys are talking about when you say OBs aren't colored by the cabinet. The DCM TF350s behind the OBs were recapped with Clarity PX caps and Mills resistors about a year and a half ago. I always thought they were a nicely balanced, fairly accurate speaker, till I started A - Bing them against the OBs. The mids and highs sounded a muted and lifeless compared to the OBs, and I could hear coloration from the cabinet. I'll have to sneak these into the house when the wife is away and listen to them in a bigger room.
 
Very ear opening is it not? Good start bigaltx24. When you get them in the next location try the driver close to the floor. Add tilt to aim at listening position. Also if possible corner loading can bring bass into the picture. Good luck.
 
I've owned these drivers for a couple of years and have never played them, plus I don't know how long they had sat before I got them. I put about 4 hours on them yesterday and towards the end I was getting respectable bass. I've seen this before with rubber surrounds, if they've sat a long time, it can take some time to loosen them up.
 
Tried out my Zenith 49ZCZ852s today, even on this small baffle these things have nice bass. The highs were a little grating when I first powered them up, but seemed to have mellowed with more playing time. I put about three hours on them today, and came away very impressed. They have a full, rich sound with lots of detail. The Bozaks will probably wind up in a small guitar cab.


 
The thing I like most about the Zeniths are the "to die for" mids. As Paul Klipsch once said, "we live in the midrange" and there's where most of our music comes from. Velvet smooth, relaxed, refined, and detailed enough, I could see the big Zenith as a single driver in OB and it would easily eclipse the smaller Betsy's and Tang Bands of the world. It makes just enough bass and adequate top end that you don't feel anything is missing. I've forgotten to turn on the woofer amp and didn't miss it but when I remembered and switched it on, then the difference was apparent. While smaller drivers can be more point source, the Zeniths yield a huge sound stage that spans the entire room. I hear as much sound between the speakers as anywhere else and they're a good 12 ft apart.

I wouldn't use the Zenith as a woofer as it's forte is running full range with nothing in the signal path. It needs no correction and sounds right as rain. I bring in my 15" woofers to reproduce the lower octave and provide the bass foundation which the Zeniths can't do.
 
The "Glow In The Dark" blog recommended a vintage tube amp for the OB Zeniths so I retrieved this gereatric receiver from storage and put it to good use. It's a Rotel EL84 and it probably makes 4 or 5 watts but those single ended flea watts are all the Zeniths would ever need. Lovely combination I must say. Still use a Yung SD 100 watt plate amp for the H-frame woofers.

PB220016.jpg
 
Ha! Ha! and thanks essNeff,

So is there a support group for addicted tinkerers like myself who won't leave well enough alone?
 
The "Glow In The Dark" blog recommended a vintage tube amp for the OB Zeniths so I retrieved this gereatric receiver from storage and put it to good use. It's a Rotel EL84 and it probably makes 4 or 5 watts but those single ended flea watts are all the Zeniths would ever need. Lovely combination I must say. Still use a Yung SD 100 watt plate amp for the H-frame woofers.

That's exactly where I'm headed with these. I pulled these from a Zentih console that also contained a Zenith 5G29 single ended EL84 amp. I rebuilt and modified the amp so that it's very similar to a Decware SE84. Now that I know how nice these things sound, I've got to build some nice looking baffles for them so they can go in my main system. I might do something like Glow In The Dark did, or like the JE Labs Arkiv.
 
Can I find those Zeniths on the ebay I suppose

I used to see them all the time but I hope for your sake that the word hasn't gotten out. I know a couple of guys on Audio Circle that bought theirs after I posted there. If you find one that's 12" and it looks like mine with Alnico mags and the model number is 49CZ*** buy it.

But I'm thinking there must be a number of wide band speakers like the Zeniths from the late 50's that could be just as good. I'd look for large ones like the 12" with alnico magnets and try to determine if the console they came from had an open back.
 
That's exactly where I'm headed with these. I pulled these from a Zentih console that also contained a Zenith 5G29 single ended EL84 amp. I rebuilt and modified the amp so that it's very similar to a Decware SE84. Now that I know how nice these things sound, I've got to build some nice looking baffles for them so they can go in my main system. I might do something like Glow In The Dark did, or like the JE Labs Arkiv.

Your EL84 amp was voiced for the Zenith speakers so now you can really get fired up to finish the baffles. I sold my Zenith amp as it was mono and I didn't want to look for a mate.
 
The spousal unit was out tonight, so I brought the OBs in and hooked them up in my main system. Man they really sound sweet with the tube amp. What really surprises me is how balanced they are. There's no part of the music that stands out, but there's nothing that's missing either. Also I have them about eight feet apart and the soundstage is huge. The wifey will not be pleased that they in the house, but I'll take that heat for a while while I get some nice baffles made.
 
The spousal unit was out tonight, so I brought the OBs in and hooked them up in my main system. Man they really sound sweet with the tube amp. What really surprises me is how balanced they are. There's no part of the music that stands out, but there's nothing that's missing either. Also I have them about eight feet apart and the soundstage is huge. The wifey will not be pleased that they in the house, but I'll take that heat for a while while I get some nice baffles made.

:thumbsup:
 
Here is my OB experiment -
After buying a near empty home built console stereo and realizing that I paid too much to just flip the drivers, I searched for something to do with the Bozak drivers. An Open Baffle seemed like a good project as I had a pair of 12" woofers, 8" aluminum mids and four 209yc tweeters and two crossovers. The crossovers are set at 800 and 2500 with 6db cutoff.
I had some 2x2' sheets of 3/4 mdf, a jigsaw and a router. It took me the better part of a day to get everything cutout and assembled. I am encouraged by the results. The Mid range and highs are very good. The sound stage is excellent. The LF is a bit muddy and is at a much lower SPL than the mids and highs. I am going to experiment with room placement first and see how that affects the LF.
The photo was taken with the panoramic mode - thus the distortion. The speakers are toed in approx 15 degrees. Layed back approx 20 degrees. The back wall is approx 2.5 feet from the back wall. The back wall has an angled transition to the ceiling. I am thinking that I might be able to use this for corner loading. The back wall is approximately 14 feet across and the room is approx 30 feet deep.
IMG_7992.JPG
Any questions or suggestions are welcome!
 
When I enlarged your photo, the wall hanging reminded me of a past LSD trip I once had.
Crazy Man!
I have some old Magnavox 12" Woofs and 4" Tweets (Eminence sourced?) that I want to fool around with similar to your rig.
I wonder how similar they are to the Zenith 49's? Did Zenith produce their own speakers?
Nice Job!
 
When I enlarged your photo, the wall hanging reminded me of a past LSD trip I once had.
Crazy Man!
I have some old Magnavox 12" Woofs and 4" Tweets (Eminence sourced?) that I want to fool around with similar to your rig.
I wonder how similar they are to the Zenith 49's? Did Zenith produce their own speakers?
Nice Job!
Thanks - that was the look I was going for. Tie-Dyes are a lot of fun to make. This one was double dipped!

Look for the six digit EIA codes on the back of the speaker cones. Magnavox will start with 232 and Zenith will start with 343. The next three digits are the date codes. They might also be stamped into the baskets
 
This question may have been answered many times already, but I haven't read the entire thread — 1,700 posts!

I have a very clean pair of Electro Voice 12-TRXB's: 12" woofer, center-mounted horn tweeter, and a whizzer. I've had them for years, never used them.

Have any of you used them in an open-baffle design? Or have an informed opinion of their suitability?
 
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