Open Baffle Epiphany!
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Poultrygeist
Lunatic Member
Did I say it was a CD?
dnewma04
The Healer
It just occurred to me that EV used to produce a compression driver designed to re-enter the back wave into the horn. They used it in a monopole horn design but it might be worth a listen with dipole horns. You'd get the side nulls from the horns so their would be any nulls from front/back wave cancellation but it would make for a real dipole. As I recall the frequency response front and rear was quite different, though, so I have no idea of the real world effect of this idea. Lots of measurements would be necessary.
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dnewma04
The Healer
I just had a quick chat with a friend who designs compression drivers for one of the big driver houses. He said that some of their designs don't measure noticeably different with the back on or off and a few do. I wonder if contacting Radian directly would allow you to get a pair of just the backs? If you have access to a mill or a large stepped drill bit, you could easily mimic what emerald is doing with the screen and a rubber grommet. Maybe the Radian is a design that wouldn't have a significant effect outside of potentially diminished power handling.
tomlinmgt
Lunatic Member
Hmmm...the pair of Orion speakers I heard and saw a couple years ago used indentical tweeters, one firing forward and the other back.
With regards to the pattern question of a removed back CD....I've heard and don't know the truth of, is that this is where the dome tweeter came from. Designed after using the CD diaghram, turned around and used as a forward firing tweeter. If this is all so, then you could expect it to have a similar pattern I would think.
EV3
dnewma04
The Healer
EV, the rear firing tweeter became an option later for those who wanted it.
With the back fully removed, it might behave a little like a typical driver of the same width. I just don't know if it was surrounded like Mister Pigs by a ridge what the response would look like. It seems like off axis would certainly be impacted.
With the back fully removed, it might behave a little like a typical driver of the same width. I just don't know if it was surrounded like Mister Pigs by a ridge what the response would look like. It seems like off axis would certainly be impacted.
tomlinmgt
Lunatic Member
^^^
It would almost certainly have to be....with the dome recessed in the housing rather than protruding unobstructed such as is the conventional configuration. I can't imagine that thing having much, if any, dispersion off axis. It would be like shooting water out of a nozzle.
It would almost certainly have to be....with the dome recessed in the housing rather than protruding unobstructed such as is the conventional configuration. I can't imagine that thing having much, if any, dispersion off axis. It would be like shooting water out of a nozzle.
There's been a lot of discussion about extending the low bass, and I'd like to give it a try with my Corals before committing to cutting holes in wood. How well will old 15" Magnavox woofers (CTS manufactured 8ohm) from a console work for this application? I'm thinking they should work fine for OB but have no idea how low they might go and/or what I'd need coil-wise to cross them to the Corals.
Poultrygeist
Lunatic Member
Are the Magnavox woofers from an open back console?
Quick Update on my Morel Experiment, below. I swapped out the temporary tweeter cutoff that's seen below (A resistor and cap to cut the low freq's) with a choke and capacitor that I pulled from another Morel 2-way box where the enclosure was toasted. The frequency is the same 2500 Hz, BUT the sound is MUCH different. Everything got immediately better. The high end is much cleaner and more crisp and the midrange clarity is also improved. Running those big 12" paper cones full range was not advantageous. My guess is that the VCs have enough resistance on their own to not need any extra resistors in the circuit? might keep tweaking, but so far this is a cheap, fun experiment with terrific results.
OK, here's my first foray. I just mounted these to some leftover OBX that I had lying around and plucked a simple 1-st order 2-way crossover from a bookshelf pair that I had lying around with no drivers.
The drivers here are Morel Integra 12. 12" treated paper woofer and the classic Morel 1-1/8" dome tweeter, horn loaded, and mounted coaxially with the woofer cone. The woofer is a dual magnet, as is the tweeter. The crossover point is somewhere around 2500 Hz I believe with the woofer running full range with no choke.
Rudimentary, but it actually sounds quite good! Need to be within 8 feet of the speakers or the bass drops off like crazy, but within range, the sound is full and very appealing.
With some tweaks, this could be a nice experiment. THANKS ALL!
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I haven't contacted the seller, but here's a clip from the ad:
"is a pair of 8 ohm 15" woofers / speakers removed from a 1964 vintage Magnavox "Astro-Sonic 100" console stereo (model 1-ST680). This was their top-of-the-line console stereo for that year that included a separate solid state amp (A590) rated at 50 watts/ch RMS"
Poultrygeist
Lunatic Member
I pulled these 12 inchers from an old Zenith open back console and they work well in OB. Like many consoles they were paired with tweeters and are really more wide band speakers than woofers. They needed the Alphas for bass support.
mhardy6647
Lunatic Member
Nope, but Fs is probably 50 Hz or higher (very likely highter) and Qts is probably high (1.2 or even more)... accordion paper surround and pretty stiff suspension, I reckon.
Over the years, there were plenty of 15 inch midranges produced ;-)
Usually a quick tap on the cone will give a good qualitative assessment of how high or low Fs is... otherwise a quick frequency sweep with a generator or s/w and your sound card will give a fine estimate of Fs using no other instrument than your ears
Over the years, there were plenty of 15 inch midranges produced ;-)
Usually a quick tap on the cone will give a good qualitative assessment of how high or low Fs is... otherwise a quick frequency sweep with a generator or s/w and your sound card will give a fine estimate of Fs using no other instrument than your ears
Thanks for the thoughts and info. I guess I'll just pass on these and experiment with a sub to see just where I need the support before doing anything more. I'm also planning on putting the Corals back in their cabinets and add some extra Poly-fil. They only came with a layer of what looks like carpet padding stapled to the sides and rear baffle.