I've spent some more time working on these speakers and the results are worth it. Of course there was crossover work and some room positioning work. One major difference yesterday was that I switched to the long wall of the room, so that wall behind the speakers was a plane, not a stepped alcove like the short wall. Here are photos of the two different placements. In both cases the rear of the baffle was 7' (~2m) from the wall, or 7 & 13' (4m) for the alcove setback. These are large speakers, but hardly look it in a room like this!
These two placements sound about as different as you would imagine. With the dual depth provided by the alcove, the sonic image had good depth, but almost everything with depth ended up back in there, the spread usually wasn't wide. Playing the flat wall, there was less illusion of depth, but the image was wider and not many sounds stuck to the speakers. Voices seemed more present and realistic on the short wall. One odd thing that was noticeable was how the depth was flipped compared to my lava cave system. https://www.diyaudio.com/community/threads/caveman-speakers-the-troglodytes.269864/ The cave system would put voices right at the speaker line, with orchestral stuff behind, for example Frank Sinatra with orchestra. But this room and speakers flipped that with Sinatra deep and the orchestra more up front.
I don't understand how that happens.
One recording was spectacular on the short wall. "The Power and the Majesty" by Brad Miller. https://www.discogs.com/master/303132-Brad-Miller-The-Power-And-The-Majesty This is a field recording from 1978 of a thunder storm. Wow! The effect was uncanny. My brain simply would not believe that it wasn't real and that it wasn't outside in the distance. The illusion was so powerful that I had to stop the track mid thunder a couple of times, because I had doubts. It sounded so real, so far away, so huge, so outside the room. Sometimes there was thunder behind me Not many speakers can do that. My own thunder recordings done in Florida a few years ago where a pale, sad version of Brad's. He did amazing work. It was like hearing a magic trick.
These two placements sound about as different as you would imagine. With the dual depth provided by the alcove, the sonic image had good depth, but almost everything with depth ended up back in there, the spread usually wasn't wide. Playing the flat wall, there was less illusion of depth, but the image was wider and not many sounds stuck to the speakers. Voices seemed more present and realistic on the short wall. One odd thing that was noticeable was how the depth was flipped compared to my lava cave system. https://www.diyaudio.com/community/threads/caveman-speakers-the-troglodytes.269864/ The cave system would put voices right at the speaker line, with orchestral stuff behind, for example Frank Sinatra with orchestra. But this room and speakers flipped that with Sinatra deep and the orchestra more up front.
I don't understand how that happens.One recording was spectacular on the short wall. "The Power and the Majesty" by Brad Miller. https://www.discogs.com/master/303132-Brad-Miller-The-Power-And-The-Majesty This is a field recording from 1978 of a thunder storm. Wow! The effect was uncanny. My brain simply would not believe that it wasn't real and that it wasn't outside in the distance. The illusion was so powerful that I had to stop the track mid thunder a couple of times, because I had doubts. It sounded so real, so far away, so huge, so outside the room. Sometimes there was thunder behind me Not many speakers can do that. My own thunder recordings done in Florida a few years ago where a pale, sad version of Brad's. He did amazing work. It was like hearing a magic trick.
Crossovers. A lot of different configurations were tried. On the short wall I tried a 100Hz low pass and 2kHz high pass, both first order. This did work well and help vocals, for sure. But it wasn't perfect. After trying a few more things I settled on 60Hz low pass (1st) and 800Hz high pass on the horn, 2nd order Butterworth. Horn same polarity as the woofer. That cleaned up vocal and had the best tonal balance of anything I tried. Still not perfect but getting there. These two different crossovers sounded similar, more similar than expected. A PEQ was used to bring down the horn peak at 1550 Hz by 4 dB. It made a bigger difference with the 800 Hz 2nd order high pass, as you might imagine.
Moving to the long, flat wall, the mixed 1st & 2nd order was not the preferred filter. After a good bit of trial and error, I ended up back at the all 1st order - this time low pass @90 Hz and high pass @2 kHz, I sill used the notch at 1550 Hz, but it wasn't absolutely necessary. EQ and levels were tuned by ear and with non-correlated pink noise. This is where the system ended up on the long wall, with the crossover just mentioned.
Overall it is very very good, but not quite where I want it. If memory serves, it is as good or better than the version we had at RMAF 2008. It has many of the same strengths and weaknesses.
Moving to the long, flat wall, the mixed 1st & 2nd order was not the preferred filter. After a good bit of trial and error, I ended up back at the all 1st order - this time low pass @90 Hz and high pass @2 kHz, I sill used the notch at 1550 Hz, but it wasn't absolutely necessary. EQ and levels were tuned by ear and with non-correlated pink noise. This is where the system ended up on the long wall, with the crossover just mentioned.
Overall it is very very good, but not quite where I want it. If memory serves, it is as good or better than the version we had at RMAF 2008. It has many of the same strengths and weaknesses.
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Your ceiling would appear to be your main source of earlier reflections (vs later). Your listening distance would appear to be the arbiter of the tone of those reflections should they fall near any variations in coverage angle.
In addition, regarding the ceiling level, ie it's relative sound level to the rest of the room. I don't see that it needs to be fixed (unchangeable).
In addition, regarding the ceiling level, ie it's relative sound level to the rest of the room. I don't see that it needs to be fixed (unchangeable).
Yes indeed, other than typical floor bounce, he ceiling is the major reflection. The floor and ceiling can easily be seen in the impulse plot at 48cm and 128cm path difference.
One thing I realized when looking at the sort wall is that (of course) there are a lot of reflections off the wall from the woofer, but almost none from the tweeter horn. That means that everything below 500Hz has a lot of room reflections and room tone, whereas above 500Hz the ratio of direct to relfected is much different. My first successful OB was with 15" woofers and an Altec 811b horn and it did work well in a much smaller space than this. Getting it right wasn't easy or quick.
As @planet10 has mentioned to me, getting good vocals out of an 18" is not easy. It sure isn't. The 1.4" compression driver and the large cone help, but it's still tricky.
One thing I realized when looking at the sort wall is that (of course) there are a lot of reflections off the wall from the woofer, but almost none from the tweeter horn. That means that everything below 500Hz has a lot of room reflections and room tone, whereas above 500Hz the ratio of direct to relfected is much different. My first successful OB was with 15" woofers and an Altec 811b horn and it did work well in a much smaller space than this. Getting it right wasn't easy or quick.
As @planet10 has mentioned to me, getting good vocals out of an 18" is not easy. It sure isn't. The 1.4" compression driver and the large cone help, but it's still tricky.
Do you have any small full range drivers or tweeters on hand? With a room that large you could use a small full range to complement the roll off of the 18" and create a more symmetrical polar response, placing it behind the speaker pointing toward the rear. Might find that little something you've been missing and at the very least some interesting experiments.
Unfortunately no, no full range drivers on hand. And today is my last chance to work with these until the spring of 2024.
When I had my "Lounge Lizard" OBs with horn on top, I tried a lot of rear facing tweeter tricks and never found one that I liked. I did find that the rear facing driver had to be darn loud to be heard at all. I still think it's a good idea, but I have not yet been able to get it work.
Currently my main problem with these is that there is a certain frequency circa 2 kHz that will jump out and bite you. Not on every recording, but from time to time when someone hits that note -ZING! It's painful. I remember this from working on the horn part of the passive crossover and never did fix it. A few years later John told me that it was not the horn, it was the woofer. He added a trap to the woofer and the problem went away. So today I will be in search of that harsh resonance, wish me luck finding it. I'm still convinced that it's the horn, but I'll look at both equally.
When I had my "Lounge Lizard" OBs with horn on top, I tried a lot of rear facing tweeter tricks and never found one that I liked. I did find that the rear facing driver had to be darn loud to be heard at all. I still think it's a good idea, but I have not yet been able to get it work.
Currently my main problem with these is that there is a certain frequency circa 2 kHz that will jump out and bite you. Not on every recording, but from time to time when someone hits that note -ZING! It's painful. I remember this from working on the horn part of the passive crossover and never did fix it. A few years later John told me that it was not the horn, it was the woofer. He added a trap to the woofer and the problem went away. So today I will be in search of that harsh resonance, wish me luck finding it. I'm still convinced that it's the horn, but I'll look at both equally.
It was my last day with these big beauties. They are back in storage until springtime.
Finding the zinger note was not difficult, I just listened to the note in a few songs where it hit hard, guessed it to be just a little more than 2K and did an FFT of the notes. 2130 Hz turned out to be what was biting my ears. With a 10dB notch Q=5 on the horn the harshness went away, everything is smooth now. No bite left, except where it should be.
Funny thing is, I can not see it in the measurements. Don't see it in FR or phase and don't see it in waterfall or spectrogram. But I sure could hear it. And the notch worked to get rid of it. The Q of the notch could probably be fine tuned tighter, and the depth could be adjusted, but 2130Hz seems to be it. Happy to have found it.
It was fun to get to play with these big coax drivers so many years after first hearing them. They would have been fabulously amazing in my old lava cave. By coincidence, there was another pair of these drivers at RMAF that year - in huge bass reflex cabinets with lovely woodwork. They sounded just as big and dynamic as ours, and they used nothing but a single cap on the horn. Our OB version did sound better, but the two versions were more similar than different.
Finding the zinger note was not difficult, I just listened to the note in a few songs where it hit hard, guessed it to be just a little more than 2K and did an FFT of the notes. 2130 Hz turned out to be what was biting my ears. With a 10dB notch Q=5 on the horn the harshness went away, everything is smooth now. No bite left, except where it should be.
Funny thing is, I can not see it in the measurements. Don't see it in FR or phase and don't see it in waterfall or spectrogram. But I sure could hear it. And the notch worked to get rid of it. The Q of the notch could probably be fine tuned tighter, and the depth could be adjusted, but 2130Hz seems to be it. Happy to have found it.
It was fun to get to play with these big coax drivers so many years after first hearing them. They would have been fabulously amazing in my old lava cave. By coincidence, there was another pair of these drivers at RMAF that year - in huge bass reflex cabinets with lovely woodwork. They sounded just as big and dynamic as ours, and they used nothing but a single cap on the horn. Our OB version did sound better, but the two versions were more similar than different.
It's really nice you've been able to start this project and that you've made some serious headway on it rather quickly. Looking forward to your reports as you continue the work in the spring.
When John had them at the Lone Star Audio Fest, coupled with 21" woofers, Bob Brines wandered into the room to listen. Bob made single driver speakers in transmission line boxes that were about as different from these OB's as you could get. He did nice work.
After listening a bit Bob had a huge grin on his face and said something to the effect that John obviously really knew what he was doing. It was a nice compliment from another talented speaker designer. But it wasn't what Bob said, it was the huge grin that drove the message home.
John had 2 and 5 watt amps in the room that year. Given the size of the hotel room all the amps had too much power. It was an amazing experience.
Glad you're getting them up and running again.
When John had them at the Lone Star Audio Fest, coupled with 21" woofers, Bob Brines wandered into the room to listen. Bob made single driver speakers in transmission line boxes that were about as different from these OB's as you could get. He did nice work.
After listening a bit Bob had a huge grin on his face and said something to the effect that John obviously really knew what he was doing. It was a nice compliment from another talented speaker designer. But it wasn't what Bob said, it was the huge grin that drove the message home.
John had 2 and 5 watt amps in the room that year. Given the size of the hotel room all the amps had too much power. It was an amazing experience.
Glad you're getting them up and running again.
Thanks Barry! yes it was fun to finally get to play with these. I never heard the version with the 21" woofer, although I did have those MCM 21s at my house for a while. Just about the perfect OB woofer. I had kludged together a big OB with the 21, a 10" mid and 3" tweeter. Sounded like crap, but the bass was great! You sent me a photo of the 18+21 rig at LSAF, but I can't find it now. If you have it, post it!
I did find a photo of our RMAF 2008 rig. Small room, big speakers. We got shut down by the neighbors, who were family of "The Absolute Sound"
Now if I could just reverse engineer the crossover from that photo......
I did find a photo of our RMAF 2008 rig. Small room, big speakers. We got shut down by the neighbors, who were family of "The Absolute Sound"
Now if I could just reverse engineer the crossover from that photo......
Yes there were many big smiles at John's speaker demos. Not the P.Audio but here is one that I remember, likely some pipe organ music.
As one listener said at the end of a demo "Damn, I need a cigarette and a bear after that!"
John's speakers where also good, but they were also a whole lot of fun.
The line was "Now I need a cigarette and a change of underwear". I remember it because I was the one that said it. One of the other guys in the room at the time will now ask me, every year, how my underwear is doing.
I think that photo is the original Widow Makers. Never heard an orchestra reproduced anywhere near that well before. It was magnificent.
Here's the coax from 2016. I never heard them without the 21" woofers but have no doubt they didn't need them. At least not in that room.
I think that photo is the original Widow Makers. Never heard an orchestra reproduced anywhere near that well before. It was magnificent.
Here's the coax from 2016. I never heard them without the 21" woofers but have no doubt they didn't need them. At least not in that room.
I have these on order :
https://www.aliexpress.us/item/3256...f99e48&afSmartRedirect=y&gatewayAdapt=glo2usa
@DavidVicente Those look very nice, never seen them before. The basket and magnet cover look Altec inspired, but the coax horn not at all.
The 0.6 QTS would do well on OB. My favorite OB woofers were Selenium 15s with a Qts of 0.6-0.7 IIRC.
Please let us know what you thing when they arrive. Are you planning to put them in a box, or on Open Baffle?
The 0.6 QTS would do well on OB. My favorite OB woofers were Selenium 15s with a Qts of 0.6-0.7 IIRC.
Please let us know what you thing when they arrive. Are you planning to put them in a box, or on Open Baffle?