Sorry - missed that because I thought it was perhaps the modded one. Ok the woofer runs full range. Good way to save on costs for a large inductor but needs the woofer to mechanically. Is the XO circa 3k5?
Optimus 1B woofer and tweeter impedance, TS params
Forgot I used DATS V3 to measure impedance of woofer and tweeter and the overall impedance an amplifier would see.
Tweeter Fs = 210.6 Hz
The speaker impedance seems to be tube friendly.
New to using DATS so welcome any corrections.
Forgot I used DATS V3 to measure impedance of woofer and tweeter and the overall impedance an amplifier would see.
Tweeter Fs = 210.6 Hz
The speaker impedance seems to be tube friendly.
New to using DATS so welcome any corrections.
Attachments
Optimus 1B woofer impedance and response curve
Found second woofer in box and ran DATS to show curve down to 20Hz.
Also, ran frequency response curve with Omnimic with mic at 1 meter distance from speaker and at height of lower tweeter and tweeter level switch on speaker set to Normal. Speaker on stand 25 inches off floor.
Like I said, I am not a speaker designer and a little knowledge can be dangerous. So I'm not sure if I have this set up correctly for testing.
But from the response curve if the crossover is close to 1.4Khz should the woofer polarity be switched since its a 2nd order crossover on the tweeter?
The woofer I found looks like the ones in the two speakers and has
Woofer 2510Aa Japan , written on the magnet so I assume its for an Optimus 1B although the parameters are not an exact match to the ones from the previous woofer I measured.
Found second woofer in box and ran DATS to show curve down to 20Hz.
Also, ran frequency response curve with Omnimic with mic at 1 meter distance from speaker and at height of lower tweeter and tweeter level switch on speaker set to Normal. Speaker on stand 25 inches off floor.
Like I said, I am not a speaker designer and a little knowledge can be dangerous. So I'm not sure if I have this set up correctly for testing.
But from the response curve if the crossover is close to 1.4Khz should the woofer polarity be switched since its a 2nd order crossover on the tweeter?
The woofer I found looks like the ones in the two speakers and has
Woofer 2510Aa Japan , written on the magnet so I assume its for an Optimus 1B although the parameters are not an exact match to the ones from the previous woofer I measured.
Attachments
I bought a pair in 1975 on sale at Radio Shack. They are in as near new condition; however, the tweeters are inoperative. I am looking to update, so I would like to know what the OP did two years ago. Any suggestions are welcome.
I know nothing about designing crossovers. I need to identify a pair of expensive tweeters I have and can use in these speakers, maybe home them out?
Regards, Ken
I know nothing about designing crossovers. I need to identify a pair of expensive tweeters I have and can use in these speakers, maybe home them out?
Regards, Ken
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Hi Ken!
I hope you have noted the earlier comments that these are mid/tweeters and not normal tweeters.
Any replacements would need to have a low resonant frequency, unlike normal tweeters.
Check out Member concertgrand's measurements above.
I hope you have noted the earlier comments that these are mid/tweeters and not normal tweeters.
Any replacements would need to have a low resonant frequency, unlike normal tweeters.
Check out Member concertgrand's measurements above.
In 1977 I bought NIB a Marantz 2220B & a pair of Realistic Nova 7Bs' ...very similar to the 1Bs' here, except the 7Bs had the three tweeter-mids. The Marantz wood case matched the veneers on the Novas beautifully.
I had the Novas up thru about 1981 until I brought them in my 70 Mustang, intent on music at a football pitch, I stood them up on top my car...I had the new Pioneer GM-120 "component" amp & the KP-66G cassette playing music...until the vibrations had them falling off my cars roof.
It was interesting & revealing just how poorly they were structurally constructed...the squiggled lines of hot-glue everywhere, but not enough & not in the right places. Both speakers broke apart into their components panels...
I would suggest an individual with these series of speakers slather some epoxy inside the cabinets, trying to reinforce all the corners & edges...trying to get inside the inevitable gaps.
----------------------------------------------------------------------Rick....
I had the Novas up thru about 1981 until I brought them in my 70 Mustang, intent on music at a football pitch, I stood them up on top my car...I had the new Pioneer GM-120 "component" amp & the KP-66G cassette playing music...until the vibrations had them falling off my cars roof.
It was interesting & revealing just how poorly they were structurally constructed...the squiggled lines of hot-glue everywhere, but not enough & not in the right places. Both speakers broke apart into their components panels...
I would suggest an individual with these series of speakers slather some epoxy inside the cabinets, trying to reinforce all the corners & edges...trying to get inside the inevitable gaps.
----------------------------------------------------------------------Rick....
Note the low resonant frequency and the impedance.
I presume Pete must have altered the crossover to suit the 8 ohm impedance of the replacement Dayton drivers.
Hopefully, Pete will chip in with the first-hand information.
TBH it's been a while, my daughter got these & my record player....! IIRC I ran the woofer full range, and probably something simple on the Dayton, Either just a cap, or cap + inductor; I'll consult the archives and see if I made any notes (If they survived last nights storm)....
Can't find any schematic, FWIW I'd usually cross over an FR Driver like the PS95 at the baffle step freq
Can't find any schematic, FWIW I'd usually cross over an FR Driver like the PS95 at the baffle step freq
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I wonder about replacing mid/tweets with a planar mid/tweet.
Another approach I have wondered about is angling a pair of mids either convex or concave. Back in the day this was occasionally done perhaps for wider dispersion or higher system sensitivity. The concave orientation might bring the acoustic centers closer together mitigating comb filtering. Of course convex orientation would give wider dispersion but the concern is interference on axis. Has anyone seen any studies of such orientations?
Another approach I have wondered about is angling a pair of mids either convex or concave. Back in the day this was occasionally done perhaps for wider dispersion or higher system sensitivity. The concave orientation might bring the acoustic centers closer together mitigating comb filtering. Of course convex orientation would give wider dispersion but the concern is interference on axis. Has anyone seen any studies of such orientations?
I still have a complete set of original mid-tweeters in good nick if anyone wants them for the cost of shipping
I might take you up on that, but which way do the speakers sound better? It seems to me since the OEM speakers are 4 OHM, one can just run the single 8 OHM and use the existing crossover? I have no experience in designing speakers.
I'd say they sound better with the PS95, probably be cheaper for you as well. Re:'use the existing crossover' - not a great idea, speaker impedance is something you need to come to grips with when dealing with xovers, it's not linear, and varies with frequency.
I'd start off just using a single bipolar cap on the PS95s, assuming the 8 ohm version 56uF would do it
I'd start off just using a single bipolar cap on the PS95s, assuming the 8 ohm version 56uF would do it
When my Nova 8Bs, (not 7Bs') self destructed via the force of gravity...I was presented with eight drivers to do with as I pleased. One thing I did was to take one of the mids' , cut the ultra-wide flange down to a more reasonable size...When the quality of sound of my JC Penny AM/FM clock-radio sounded like crap...I opened it up, removed the el-cheapo pancake speaker...re-arranged the boards & power supply & jockeyed in the relatively massive driver. The 'new' mid driver was approximately the same radiating surface, with the magnet assembly nearly the same 2 1/2 inches diameter...it took some time & effort to get it to fit...It sounded far far better...& nearly doubled the weight of the whole clock-radio.
I recall the very day I pitched it into the dump-yard, out the back of my Dodge 1500 pickup, the weight carrying it far off in the distance...it had fully malfunctioned at one point. 1978-1992.
----------------------------------------------------------------------Rick....
I recall the very day I pitched it into the dump-yard, out the back of my Dodge 1500 pickup, the weight carrying it far off in the distance...it had fully malfunctioned at one point. 1978-1992.
----------------------------------------------------------------------Rick....
My 1st speakers I ever owned were the Optimus 1Bs, I got them for my 10th BDay in 1977. I just ran across a pair on Craigslist for $60 and couldn't pass them up. The drives are all in very good shape, the crossover caps look fine. Cabinets are fair to good.
When I 1st hooked them up, they sounded like turning on a transistor radio compared to my other spks, but the more I listened to them, the more I enjoyed them. Their sound was familiar, vocals are quite nice, they imaged decent also. The bass is nice just where I like it, the lower end of the bass guitar sounded very appealing to me.
But by far their biggest draw back is the 2 T/M drivers so far apart, causes nasty lobing. I tried them on stands, but the bass vanished, so on the floor tilted back was the best option. Is it practical at all to design a Xover that would run 1 T/M as a Tweeter and the other as a Mid? I don't want to butcher the cabinet, but running those both as mids and adding a tweet as someone said, sounds like not a bad idea.
I only have a basic understanding of Xover design, it was easy to see the woofer runs full range by looking at the Xover, but I don't understand the coil hooked in line with the T/Ms. I am not asking for a class on Xover design here, just looking for possible directions to go, and I will study what I need to after figuring that out.
Thanks
When I 1st hooked them up, they sounded like turning on a transistor radio compared to my other spks, but the more I listened to them, the more I enjoyed them. Their sound was familiar, vocals are quite nice, they imaged decent also. The bass is nice just where I like it, the lower end of the bass guitar sounded very appealing to me.
But by far their biggest draw back is the 2 T/M drivers so far apart, causes nasty lobing. I tried them on stands, but the bass vanished, so on the floor tilted back was the best option. Is it practical at all to design a Xover that would run 1 T/M as a Tweeter and the other as a Mid? I don't want to butcher the cabinet, but running those both as mids and adding a tweet as someone said, sounds like not a bad idea.
I only have a basic understanding of Xover design, it was easy to see the woofer runs full range by looking at the Xover, but I don't understand the coil hooked in line with the T/Ms. I am not asking for a class on Xover design here, just looking for possible directions to go, and I will study what I need to after figuring that out.
Thanks