rljones said:
Hi Robert,
"Back in the Day" Drew Daniels from Altec + Disney would just stack-em-up into a 55" cabinet and stick these columns behind the main screen. You might get away with this today if you have a big wall mounted LCD and used some sexy water colored silk fabric as the grill cloth. I would build this first to experience the best sound possible from the drivers.
John Kreskovsky's "ICTA" WMTMW dipole might look like an art object with some graphic silk grill cloth. Think Plus-Size hi-fashion models. With black grill cloth it becomes the 2001 Monolith. I'm crusing the Tang Bang W6-1721 midrange at Parts Express plus Lambda 15-Dipoles for an ICTA clone.
The W baffle would have resonance issues at your 200Hz Xover frequency and would need some Xover notch filter work to sound right, plus it would be a waste of the Lambda 15-Dipoles BW and superior sound. The push-pull cone mass cancelation is really nice. Lambda is considering a new 10" midbass that could be crossed lower like 80Hz to where a W baffle with the cheaper Lambda 15IB would work well.
I've never gotten good results with a side mounted woofer crossed over 60Hz.
Drew Daniels
http://www.audioheritage.org/html/perspectives/drews-clues/system.htm
John Kreskovsky's "ICTA" WMTMW dipole
http://www.musicanddesign.com/icta.html
Attachments
image height
This may be off topic, and if so I'll start a different thread. But I thought I remembered Lynn mentioning, way back there, image height (as in not too low) as an important subjective parameter in his desired outcome. Other than driver placement, what influences this - timing, reflections, or? Is there a deterministic approach to modifying it?
Sheldon
This may be off topic, and if so I'll start a different thread. But I thought I remembered Lynn mentioning, way back there, image height (as in not too low) as an important subjective parameter in his desired outcome. Other than driver placement, what influences this - timing, reflections, or? Is there a deterministic approach to modifying it?
Sheldon
Re: image height
Purely subjective preference. I find images that are lower than listening height to sound kind of unnatural - tabletop sized, as it were. Even back in the Shadow Vector/Audionics days in the Seventies, I'd set up the quadraphonic demo at the CES so the midrange was at listening height - anything lower than that, particularly in quad, would sound really weird, like the soundfield was coming from underneath you.
I visualize the horizon line, and set the midrange - or whatever drivers are carrying the 1~5 kHz range - at that height, or maybe slightly above it. This mirrors the situation in real life, where the orchestra, rock-n-roll band, or movie image is just a bit above the audience in the concert hall. Yes, I know, the cheap seats at the back of the hall, or in the balcony, have an image that is below where you sit, but why on Earth would anyone want to copy the crummy sound you hear from the back of the hall or in the balcony? I prefer a Row 10 perspective and immediacy - not surprisingly, those are usually the most expensive seats.
I should add if you had musicians in your home, including a singer, the HF components of the sound wouldn't be coming from less than 30 inches off the floor. You'd be sitting, and the musicians would be standing. You'd be looking up at them.
This is also the reason I don't care for the sound of the really big audiophile WMTMW systems with a 12" woofer hanging in the air five feet off the ground. C'mon now, how often does bass come from way above you? It doesn't. Bass instruments are usually pretty close to floor.
I've come the reluctant conclusion, particularly after spending some time listening the execrable JBL EON portable speakers (the worst speaker I have ever heard), that a lot of people no longer have any idea what live, acoustic (unamplified) music sounds like, and are quite willing to put up with very tipped-up and harsh spectral balance, severely distorted HF, and bizarrely unnatural image quality. I'm old-fashioned enough to consider real musicians sawing away on acoustic instruments to be the touchstone for realism - but I'll grant this appears to be a minority preference these days.
P.S. I have reservations about any kind of W-baffle, since they require sharp-cut lowpass filters to avoid box colorations. I'm not all that interested in the polar patterns of dipoles or quasi-cardioids, but am more interested in freedom from box coloration (which cannot be removed by equalization). W-baffles seem like a step backward - the inherent problems with LF rolloff and limited power-handling of dipoles, combined with the resonances of monopole box enclosures. The 200~800 Hz region is especially important in reducing or eliminating box colorations, since the drivers themselves are still in the piston band and have fairly low coloration.
What seems more interesting is a few dB of lossy attenuation for the rear wave, but no additional delay, resonance, or standing waves. That's the purpose of the C-shaped wrap of felt around the rear.
Sheldon said:
Purely subjective preference. I find images that are lower than listening height to sound kind of unnatural - tabletop sized, as it were. Even back in the Shadow Vector/Audionics days in the Seventies, I'd set up the quadraphonic demo at the CES so the midrange was at listening height - anything lower than that, particularly in quad, would sound really weird, like the soundfield was coming from underneath you.
I visualize the horizon line, and set the midrange - or whatever drivers are carrying the 1~5 kHz range - at that height, or maybe slightly above it. This mirrors the situation in real life, where the orchestra, rock-n-roll band, or movie image is just a bit above the audience in the concert hall. Yes, I know, the cheap seats at the back of the hall, or in the balcony, have an image that is below where you sit, but why on Earth would anyone want to copy the crummy sound you hear from the back of the hall or in the balcony? I prefer a Row 10 perspective and immediacy - not surprisingly, those are usually the most expensive seats.
I should add if you had musicians in your home, including a singer, the HF components of the sound wouldn't be coming from less than 30 inches off the floor. You'd be sitting, and the musicians would be standing. You'd be looking up at them.
This is also the reason I don't care for the sound of the really big audiophile WMTMW systems with a 12" woofer hanging in the air five feet off the ground. C'mon now, how often does bass come from way above you? It doesn't. Bass instruments are usually pretty close to floor.
I've come the reluctant conclusion, particularly after spending some time listening the execrable JBL EON portable speakers (the worst speaker I have ever heard), that a lot of people no longer have any idea what live, acoustic (unamplified) music sounds like, and are quite willing to put up with very tipped-up and harsh spectral balance, severely distorted HF, and bizarrely unnatural image quality. I'm old-fashioned enough to consider real musicians sawing away on acoustic instruments to be the touchstone for realism - but I'll grant this appears to be a minority preference these days.
P.S. I have reservations about any kind of W-baffle, since they require sharp-cut lowpass filters to avoid box colorations. I'm not all that interested in the polar patterns of dipoles or quasi-cardioids, but am more interested in freedom from box coloration (which cannot be removed by equalization). W-baffles seem like a step backward - the inherent problems with LF rolloff and limited power-handling of dipoles, combined with the resonances of monopole box enclosures. The 200~800 Hz region is especially important in reducing or eliminating box colorations, since the drivers themselves are still in the piston band and have fairly low coloration.
What seems more interesting is a few dB of lossy attenuation for the rear wave, but no additional delay, resonance, or standing waves. That's the purpose of the C-shaped wrap of felt around the rear.
chrismercurio said:
Maybe some pictures when I'm getting more closely to a final state.
OB shape and PC-XO is waiting to be refined first.
Size of 6,5" for the mid was the way to go as "quasi full range / extended and XO free mid" was something I aimed for.
It allows me to cover the important band from 300 to 2,5kHz with a single speaker.
Split power operation with a second ( identical ) speaker allows for high output at low frequency XO and still keeping IM distortion very low.
Beaming doesn't get a problem as well and break up can be kept "outside" the operating band this way..
I was lucky to find a mid speakers with very low energy storage (fast decay in CSD), well controlled break up, low odd order harmonics and sounding life-like and un-strained at low and high SPL's equally.
When matching this Pro speaker with the Excel Millenium dome tweeter the differences between Home-Fi and Pro became quite obvious. The Excel Millenium - being a well regarded top tweeter I used and love for years now – simply couldn't keep up with the "speed" of that 6,5" PRO's.
Switching to AMT in the tweeter department – wow! – same league!
---------------
Lynn, having heard the Magnat ion tweeter same time back I don't share your enthusiasm for this principle.
http://www.plasmatweeter.de/magnat.htm
Sure the Magnat is 360° radiating and overall speaker integration was **** back then, but high frequency performance alone wasn't that impressive for me as well.
If I remember correct the Magnat ion speaker has pretty high distortion levels as well.
Did you have a chance to hear this one and can you comment on the differences to the ion speakers with horns you mentioned earlier?
Greetings
Michael
Well, I've heard the Magnat, Plasmatronics, and the RAAL, and the Magnat falls far short of the Plasmatronics and the RAAL. I don't know why, but the Magnat sounded inefficient and dynamically compressed, like an electrostatic with not enough stator voltage. My overall impression of the $150,000 Acapella system in which the Magnat was used was that it needed a lot more work, with a pretty disjointed and dynamically mis-matched sound - the tall cone woofer array didn't keep up with the horns, the horns had a fair amount of "plasticky" coloration, they didn't sound all that resolved or quick with a fair amount of on-axis coloration, and the Magnat had quite poor cohesion with the horns, sounding dim, weak and distant. There wasn't any part of the spectrum that was rendered all that well, and overall sonic cohesion for the big, complex, spatially dispersed system was quite poor (auditioned at a local Denver-area dealer).
The Plasmatronics was something completely different. System integration wasn't all that good, with slow and murky paper-cone midrange direct-radiators (I think they were CTS or some other mundane US-made cone mid). But the range above 3 kHz was astonishing, the most realistic HF I've ever heard, with the ability to put percussion (particularly xylophones and marimbas) right in the room. No compression AT ALL, in fact, a lot more dynamic than any horn I've heard before or since. (Horns play loud with no trouble, the problem is rapid onset of harshness at high levels - level-dependent perception of HOM's or rapid buildup of high-order distortion, take your pick.)
The RAAL is the only tweeter I've heard that remind me of the Plasmatronic - they don't really sound like ribbons at all, and certainly nothing like the Magnat. The only other choice that I can think of that would even come close would be Heil AMT's, but the vintage ones are quite variable (6 dB!), and I have no idea if the modern re-creations are good or not.
The Plasmatronics was something completely different. System integration wasn't all that good, with slow and murky paper-cone midrange direct-radiators (I think they were CTS or some other mundane US-made cone mid). But the range above 3 kHz was astonishing, the most realistic HF I've ever heard, with the ability to put percussion (particularly xylophones and marimbas) right in the room. No compression AT ALL, in fact, a lot more dynamic than any horn I've heard before or since. (Horns play loud with no trouble, the problem is rapid onset of harshness at high levels - level-dependent perception of HOM's or rapid buildup of high-order distortion, take your pick.)
The RAAL is the only tweeter I've heard that remind me of the Plasmatronic - they don't really sound like ribbons at all, and certainly nothing like the Magnat. The only other choice that I can think of that would even come close would be Heil AMT's, but the vintage ones are quite variable (6 dB!), and I have no idea if the modern re-creations are good or not.
Hello Mr. Olson,
Your review on the Plasmatronic is interesting. Isn't this HF unit using a small horn in order to increase the directivity of the sound pressure and so increase the sensitivity? I know that plasma tweeters are pretty in-efficient. That makes it a horn system right?
May I ask if you've started auditioning the midrange drivers you have? I'm very curious on your impressions but I hope I'm not putting any pressure
Thank you!
Your review on the Plasmatronic is interesting. Isn't this HF unit using a small horn in order to increase the directivity of the sound pressure and so increase the sensitivity? I know that plasma tweeters are pretty in-efficient. That makes it a horn system right?
May I ask if you've started auditioning the midrange drivers you have? I'm very curious on your impressions but I hope I'm not putting any pressure
Thank you!
The Plasmatronic did not use a horn. You could easily see the glowing purple cloud of ionized helium (it didn't ionize air) floating in front of a small mesh - it was about 2 inches across, and pulsed with the music - rather hypnotic to watch, actually. The charge system was all around it - imagine a Dyna Stereo 70 with a shiny concave metal disc in the middle of the chassis, a mesh in front of the disc, a purplish glow floating between the mesh and the disc, and the whole assembly sitting on top of a big conventional speaker.
All of this ironmongery was normally hidden with grille cloth, but for the CES, the grille frame was removed for the entertainment of the visitors, who were admonished to keep their cotton-pickin hands off the machinery or risk a nasty shock. Show-goers aren't the brightest people in the world, and are too dumb to associate an obvious corona discharge with high voltage. Dr. Hill hovered pretty close to his speakers the whole time, and I didn't blame him. Very nice guy - as the really smart ones usually are - and quite open about how the Plasmatronics worked. To repeat, it sounded nothing like the dynamically constrained and fairly directional Magnat - the Plasmatronics had stunning dynamics, and you could easily hear the extended HF.
This was in 1979, before the cursed Red Book CD, and they were playing Sheffield direct-disc LP's with a top-quality moving-coil cartridge - and those things are good for 50 kHz and beyond. As a fan of extended bandwidth and advanced tweeters, I rue the day when the Red Book 20 kHz brickwall filter sidetracked research into more advanced tweeters. In the late Seventies, anybody with a good moving-coil cartridge and line-profile stylus (as an offshoot of the JVC CD-4 FM-carrier disc) could quite easily have a source bandwidth of 50 kHz or better.
All of this ironmongery was normally hidden with grille cloth, but for the CES, the grille frame was removed for the entertainment of the visitors, who were admonished to keep their cotton-pickin hands off the machinery or risk a nasty shock. Show-goers aren't the brightest people in the world, and are too dumb to associate an obvious corona discharge with high voltage. Dr. Hill hovered pretty close to his speakers the whole time, and I didn't blame him. Very nice guy - as the really smart ones usually are - and quite open about how the Plasmatronics worked. To repeat, it sounded nothing like the dynamically constrained and fairly directional Magnat - the Plasmatronics had stunning dynamics, and you could easily hear the extended HF.
This was in 1979, before the cursed Red Book CD, and they were playing Sheffield direct-disc LP's with a top-quality moving-coil cartridge - and those things are good for 50 kHz and beyond. As a fan of extended bandwidth and advanced tweeters, I rue the day when the Red Book 20 kHz brickwall filter sidetracked research into more advanced tweeters. In the late Seventies, anybody with a good moving-coil cartridge and line-profile stylus (as an offshoot of the JVC CD-4 FM-carrier disc) could quite easily have a source bandwidth of 50 kHz or better.
German based Mundorf company makes modern AMT's that get quite good reviews:Lynn Olson said:
http://www.mundorf.com/english 1.1/speakerschassis/index.htm
They offer more models than listed in the catalog, btw. They are found in about the same price regions where the RAAL's are, and unlike the RAAL's they are completely open-back, true dipole. I haven't heard them yet (the RAAL's neither), my only experience with AMT's is the original big Heil's -- and that was an eye-opening experience for me...
- Klaus
SunRa said:Hello Mr. Olson,
Your review on the Plasmatronic is interesting. Isn't this HF unit using a small horn in order to increase the directivity of the sound pressure and so increase the sensitivity? I know that plasma tweeters are pretty in-efficient. That makes it a horn system right?
Lynn Olson said:
SunRa, perhaps you are thinking of Ionofane? It was manufactured by Fane in the sixties and used ionized air to produce sound.
Cheers,
Jon
Hi Lynn,
I have been following this thread and have learned a lot from it. I have a question about the choices that you have made that have lead to the current configuration. Why the larger format compression driver (Altec 288) that requires a supertweeter to augment the top end, rather than the Altec 802/902 series? I use the GPA 414-C 12 woofers (in sealed boxes) crossed over at approximately 850 hz to Altec 902s on Edgar 650 hz "salad bowls". With a little compensation on the 902s, I get high frequencies past the limits of my hearing. (To be fair, I'm over 50 and don't think that I am hearing much beyond 14 khz. I also don't normally listen at loud volumes) The 288 is a beautiful device, but doesn't adding a supertweeter add interference and lobing between the two drivers?
I have been following this thread and have learned a lot from it. I have a question about the choices that you have made that have lead to the current configuration. Why the larger format compression driver (Altec 288) that requires a supertweeter to augment the top end, rather than the Altec 802/902 series? I use the GPA 414-C 12 woofers (in sealed boxes) crossed over at approximately 850 hz to Altec 902s on Edgar 650 hz "salad bowls". With a little compensation on the 902s, I get high frequencies past the limits of my hearing. (To be fair, I'm over 50 and don't think that I am hearing much beyond 14 khz. I also don't normally listen at loud volumes) The 288 is a beautiful device, but doesn't adding a supertweeter add interference and lobing between the two drivers?
P.S. I have reservations about any kind of W-baffle, since they require sharp-cut lowpass filters to avoid box colorations. I'm not all that interested in the polar patterns of dipoles or quasi-cardioids, but am more interested in freedom from box coloration (which cannot be removed by equalization). W-baffles seem like a step backward - the inherent problems with LF rolloff and limited power-handling of dipoles, combined with the resonances of monopole box enclosures. The 200~800 Hz region is especially important in reducing or eliminating box colorations, since the drivers themselves are still in the piston band and have fairly low coloration.
Since your initial design relies on the horn midbass drivers, you pretty much have limited yourself to having the bass drivers on a flat baffle. However, you will have issues with the bass drivers causing the speakers to shake like refigerator boxes in a gale wind. Flat panels just don't have the inherent strength that boxes do, particularly if you rely on 3/4 inch thick plywood. Also, keep in mind that you are designing your system to play music at 100 db, or more, which is much more demanding than my system which only operates in the lower 90 db region. Bert Doppenberg designed his Quasar open baffle to be 4 inches thick to address this very issue.
The W baffle is really helpful to reduce this baffle shaking phenomenom and packs the drivers into a relatively smaller package. For my system, I low pass the bass drivers at around 100 hz, because I have a single widerange driver which can handle frequencies down to around 100 hz, I can afford to use a W-baffle because the roll off is below the resonance frequency of the W-baffle. In my system, I initially only relied on 15 inch drivers mounted on the same baffle as the widerange driver and it was terrible. I then purchased a pair of 18 inch drivers and I have those mounted in W-baffles (in series with the 15 inch drivers). Despite the sharing of the signal with the 18 inch drivers, the 15 inch drivers still shake the baffle a lot.
Before contracting someone to build a pretty set of baffles for you, my suggestion would be to cobble together a test baffle (perhaps that is what this initial design is) with the 15/12 and 18 inch drivers and give them a spin with some music. It may be an important learning expierience. In fact, I suggest playing around a lot with some cheap wood before figuring out a serious pathway.
There is a lot about open baffle speakers that isn't well known and testing with different configurations is very helpful.
Retsel
Since your initial design relies on the horn midbass drivers, you pretty much have limited yourself to having the bass drivers on a flat baffle. However, you will have issues with the bass drivers causing the speakers to shake like refigerator boxes in a gale wind. Flat panels just don't have the inherent strength that boxes do, particularly if you rely on 3/4 inch thick plywood. Also, keep in mind that you are designing your system to play music at 100 db, or more, which is much more demanding than my system which only operates in the lower 90 db region. Bert Doppenberg designed his Quasar open baffle to be 4 inches thick to address this very issue.
The W baffle is really helpful to reduce this baffle shaking phenomenom and packs the drivers into a relatively smaller package. For my system, I low pass the bass drivers at around 100 hz, because I have a single widerange driver which can handle frequencies down to around 100 hz, I can afford to use a W-baffle because the roll off is below the resonance frequency of the W-baffle. In my system, I initially only relied on 15 inch drivers mounted on the same baffle as the widerange driver and it was terrible. I then purchased a pair of 18 inch drivers and I have those mounted in W-baffles (in series with the 15 inch drivers). Despite the sharing of the signal with the 18 inch drivers, the 15 inch drivers still shake the baffle a lot.
Before contracting someone to build a pretty set of baffles for you, my suggestion would be to cobble together a test baffle (perhaps that is what this initial design is) with the 15/12 and 18 inch drivers and give them a spin with some music. It may be an important learning expierience. In fact, I suggest playing around a lot with some cheap wood before figuring out a serious pathway.
There is a lot about open baffle speakers that isn't well known and testing with different configurations is very helpful.
Retsel
I was looking through this thread as there was lots of really interesting info and it looks that is getting really close to project I was interested in.
I got a pair of PAudio 12' BM12CX38 coaxial drivers: http://www.loudspeakersplus.com/images/BM-12CX38-15CXHC.pdf)
At the moment they are mount in 2.8 cabinets, with just one capacitor on the HF driver and pot to reduce HF output.
I really like the voice reproduction, but there are many other things that sound "wrong", so really wanted to try something completely different with this drivers.
Was thinking about using them in open baffle and having 2 separate subwoofers; kind of simmilar to Bastanis.
I seen that bastanis also uses just capacitor in his designs, so was wondering if this might work in my case, or is this wrong driver to do this.
For active subwoofer I am planning to do IB as I got already openings ready in the wall and would use parametric equalizer to tune it to room.
The other option is, of course, to just make a sealed box subwoofers, as Bastani uses.
As I am really new to this any advice would really help; the main one trying to understand if drivers I got are actually suited for this aplication.
Thanks, Robert
I got a pair of PAudio 12' BM12CX38 coaxial drivers: http://www.loudspeakersplus.com/images/BM-12CX38-15CXHC.pdf)
At the moment they are mount in 2.8 cabinets, with just one capacitor on the HF driver and pot to reduce HF output.
I really like the voice reproduction, but there are many other things that sound "wrong", so really wanted to try something completely different with this drivers.
Was thinking about using them in open baffle and having 2 separate subwoofers; kind of simmilar to Bastanis.
I seen that bastanis also uses just capacitor in his designs, so was wondering if this might work in my case, or is this wrong driver to do this.
For active subwoofer I am planning to do IB as I got already openings ready in the wall and would use parametric equalizer to tune it to room.
The other option is, of course, to just make a sealed box subwoofers, as Bastani uses.
As I am really new to this any advice would really help; the main one trying to understand if drivers I got are actually suited for this aplication.
Thanks, Robert