[Jon L]

0220251622 by drjlo2, on Flickr

I always wanted to try the famed Zenith 12" 49CZ852 Alnico full-range driver and had a chance to pick up a pair. 
http://glowinthedarkaudio.com/zenith-49cz852.html

Instead of the usual 3/4" plywood panels, I opted to use table furniture, which happens to be 3/4" thick on the panel.  To avoid exposing the unfinished wood color more, i left the hole edges without roundover, which worked out fine since I have the drivers pointed straight at my ears in near-field setup, 4 feet away. 

Now I understand the saying, "There are people who have never built open baffle speakers, but nobody has built only one."   

Powered by single-ended 6 watt 829B transmitter tube, the good news is certain songs sound the best of anything I've heard in the past anywhere.  The bad news is certain songs sound some of the worst. 

To my ears, the rai·son d'ê·tre of this Alnico single-driver open-baffle setup is the almost mystical sustain-decay of vocals, especially female vocals.  After the initial attack of the vocal, when the singer holds the sustain and slowly lets the air flow out and diminish, it sounds and feels like vocal textures are delightfully and quietly exploding all around me and traveling right through me like champagne bubbles.  Special stuff.

Things like hard rock, electronica, metal just sound poor, especially compared to my horn speaker setup.  I do have some famed tweeters and woofers around the house, but it seems unwise trying to add huge woofer vibration to the actual vocal baffle, so a separate baffle will be considered.  Tweeters seem almost unnecessary, but I do have things like JBL 077 prism tweeters and Great Heil AMT's, so things can be tried for fun.  For now, I'm enjoying some crazy good vocal music. 

[FullRangeMan]

Thankyou for posting your review

[opnly bafld]

Thanks for sharing (if these are the ones I saw the price was very reasonable).

Things like hard rock, electronica, metal just sound poor,   

Makes sense that music people would have been playing on their consoles when new would sound good with these wideband drivers.
As I think you were alluding to making them part of a 3 way speaker would greatly improve their performance with the above genres.
I like kiss (not the music group  ), so if I ever decide to get a pair again it would just be bass help like before.

[FullRangeMan]

Do your wife already know what you do with her table?

[Jon L]

...And it looks like integrating a supertweeter to this fullrange is not going to be a trivial matter.  So far, even crossing tweeters in at ~10kHz results in a bit of loss of the magic.  I wonder if adding bass drivers will have similar effect on the coherence and vivacity.

[FullRangeMan]

To not prejudice the Zenith you woud add a 15" woofer in parallel after the Zenith, not in Serial, you can or not use a Inductor 0.47mH to cut at 360Hz.

[FullRangeMan]

[opnly bafld]

Bi-amping and as low as possible x-o is the way I would go, don't have the bass driver overlapping frequencies the Zenith is producing well.
Be sure not to have the bass driver playing too loud.

I have used 10~12 mH coils and plate amps successfully, for me which one I use depends on how well I can get 2 different drivers to sound like one.

[opnly bafld]

...And it looks like integrating a supertweeter to this fullrange is not going to be a trivial matter.  So far, even crossing tweeters in at ~10kHz results in a bit of loss of the magic. 

Did you try it firing backwards so the reflection is higher than the baffle or on the floor behind the baffle firing up at an angle so it reflects off the front wall and then the ceiling?

[Jon L]

Did you try it firing backwards so the reflection is higher than the baffle or on the floor behind the baffle firing up at an angle so it reflects off the front wall and then the ceiling?

I tried that too, but I don't get positive OR negative effects doing that, probably because I am sitting more near-field, with open baffle speakers ~1/3 way from the back wall (seat side) not the usual 1/3 way from front wall.  If I increase the output of the tweeter enough to notice its effect, then i start losing that coherence. 

I have many various tweeter types around and need to dig around to see if I can cross them even higher, but honestly, I don't feel like I *need* more treble due to the nice midrange.

Zenith parameters from search (actual measurements)
Re: 5.85 ohms
Fs: 84.79 Hz
Qts: 1.67
Qes: 1.86
Qms: 16.11
Le: .26 mH
Mms: 21.14 g
Vas: 2.6 cu. ft.
BL: 5.92 Tm
Dia: 10.5"
Sensitivity: 95.81 db/w

I already have a pair of 15" Goldwood GW1558, which has similar sensitivity as Zenith.  I think i want to just blend in the bass below the Fs (85Hz), with the first goal of coherence.  Inductor value is then getting pretty large (13-15 mH) and seem not that easy to find.  May need to connect two inductors together.  Any brand (reasonable price) recs?  Combined prices for nice inductors may even exceed good plate amps

0212251907 by drjlo2, on Flickr

[viggen]

if you have it, try using the original fu19 tube?  my 601c sounds more modern with the fu19 as it has less mid and seemingly more highs.

[opnly bafld]

I have Dayton SPA250 amps and it's not always easy to get a good blend with the 24/oct low pass.
Bought my coils from Madisound before copper became a precious metal, I think I paid about half of the current prices.

https://www.parts-express.com/speaker-components/crossover-components/crossover-inductors/solid-core-inductor-crossover-coils/brand/Dayton%20Audio?order=base_price:asc

[Poultrygeist]

I've enjoyed the Zenith 49CZ OB's for well over ten years. I had used the separately powered H-frame Alpha's with other projects and so it was easy to add the Zeniths to them. While bass support is needed with the Zeniths adding a tweeter proved to be a challenge even though my goal was just a bit of sizzle on top. I first tried a compression tweeter ( shown in this picture ) with a single cap as its a good match with its higher sensitivity. It proved a little too hot for my liking and I also knew a front firing tweeter wasn't the best course to follow but trial and error is your friend.







 

[Poultrygeist]

After trying several combinations I came up with the addition of rear firing Realistic super tweeters wired out of phase with the compression tweeters driven by the same SET amp that powers the Zeniths. While this arrangement might appear unorthodox to some all I can say is it really works for me and my passion for small group acoustic jazz. High hat cymbals shimmer like never before. Shown here are just the OB tops which rest on the H-frame bass woofers.

[Jon L]

I have a feeling my dipole Great Heil AMT will fare better, but the darn thing is 14.5 Lbs, and I can't quite figure out how to mount it securely to this baffle.

0530241858_HDR by drjlo2, on Flickr

[Poultrygeist]

I would mount them in a cut out on a shelf extending on both sides of the baffle. How would you integrate them? They're 4 ohms and more than just tweeters.

[Poultrygeist]

Using your "table" baffles I would mount them below the Zeniths. From your picture I can't tell if the baffle is perpendicular to the floor but it would need to be.

[jk@home]

I have a feeling my dipole Great Heil AMT will fare better, but the darn thing is 14.5 Lbs, and I can't quite figure out how to mount it securely to this baffle.

0530241858_HDR by drjlo2, on Flickr

I have Heils that I will be using on my OBs. Using 1/4" aluminum angle, which bolts to the back (thru to front) of the baffle and resting the AMTs on those.

https://www.amazon.com/dp/B0DD1P4XPW?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1
or
https://www.amazon.com/dp/B0C4FX14JD?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_2

Heres one example (not me)
https://www.fedde.nu/audio/chill-baffle3.html

[jk@home]

I had started out with taller baffles, used the 3 x 3 angle.


Later chopped down the baffles, will be using the 2 x 3 in the same way. Heil mounted on top, like the "Chill" example posted above.

[Jon L]

I decided not to add bass drivers to main baffle in order not to smear vocals.  For now added outboard subs speaker-level, which are working out nicely, so much so that I have my plans for building open-baffle bass units on hold.   
I also felt the upper-midrange was a bit too lively, which was ameliorated by adding open-cell foam around the driver. 
This 96dB efficient system, when driven by low-power single ended tubes, is quite special indeed 

0309251414_HDR by drjlo2, on Flickr