I have asked simpler variation this question on another forum, so if you go there, please ignore this one.
The McIntosh XRT2.1K suspends a midrange and tweeter line in front of the woofers.
In my case I am thinking of suspending a line of 12 .9 inch wide PT-mini-6 planars(40 inches) in front of a line of 2.5 inch mid ranges(66 inches). The cross at 5000 hz will allow the sound to diffract around the line without obstructing the sound. Ostensibly, this will do two things: a) eliminate all vertical comb distortion(from the line of planars), and b) eliminate any horizontal comb distortion.
It will also allow a degree of integration of the mid frequencies(500-5000) with the treble above it, much like a full range line array.
If you are a purist, is this worth doing? For me, in my system, it would be pretty easy to do.
The McIntosh XRT2.1K suspends a midrange and tweeter line in front of the woofers.
In my case I am thinking of suspending a line of 12 .9 inch wide PT-mini-6 planars(40 inches) in front of a line of 2.5 inch mid ranges(66 inches). The cross at 5000 hz will allow the sound to diffract around the line without obstructing the sound. Ostensibly, this will do two things: a) eliminate all vertical comb distortion(from the line of planars), and b) eliminate any horizontal comb distortion.
It will also allow a degree of integration of the mid frequencies(500-5000) with the treble above it, much like a full range line array.
If you are a purist, is this worth doing? For me, in my system, it would be pretty easy to do.
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Might be worth sending this guy an email.
Roger Russell, McIntosh Lab., Scripto and Norma Pencils and leads
Helped me with a few questions. Interesting website too.
Roger Russell, McIntosh Lab., Scripto and Norma Pencils and leads
Helped me with a few questions. Interesting website too.
When I initially read your entry I immediately thought of this -
GRAND ORGUE | Visaton.
It is not exactly what you mentioned but it looks like an arrangement that would have good integration. I unfortunately have never heard them (but I would luv to).
GRAND ORGUE | Visaton.
It is not exactly what you mentioned but it looks like an arrangement that would have good integration. I unfortunately have never heard them (but I would luv to).
Yeah... I emailed Roger this morning. I’m not sure whether he worked on these before he and McIntosh parted ways.
He’s retired from McIntosh, and has his own full range line arrays: IDS-25.
The PT-mini-6 tweeters will function similar to other slot/planar/ribbon/AMT tweeters when used in a line array. Stacked vertically their horizontal dispersion will be very wide while the vertical dispersion will trend toward the height of the active area of the device at the upper end of their frequency response. I describe this performance on page 14 of the NFLAWP.
Don't expect significant issues from comb lines between drivers in a planar stack as their vertical dispersion has minimal overlap. Hence, you get very little SPL improvement versus frequency with these devices. This is unlike cone drivers which have overlap in their vertical dispersion.
For best coverage in a listening room you will need a line of PTmini-6 long enough to cover both standing and seated listeners. I am thinking 9 devices (about 30 inches long) total height or more as a minimal line. More devices will likely be needed for most situations.
With little SPL increase the stacked PT-mini-6 planars will not have pro sound output but they will be OK for a normal home situation. You might purchase a few of these drivers and try them out to get an idea of how they sound as some of the users on the PE site report issues with distortion. I suspect some buyers are buying these tiny drivers and expecting grand sound without an adequate crossover.
Jim
http://www.audioroundtable.com/misc/nflawp.pdf
Don't expect significant issues from comb lines between drivers in a planar stack as their vertical dispersion has minimal overlap. Hence, you get very little SPL improvement versus frequency with these devices. This is unlike cone drivers which have overlap in their vertical dispersion.
For best coverage in a listening room you will need a line of PTmini-6 long enough to cover both standing and seated listeners. I am thinking 9 devices (about 30 inches long) total height or more as a minimal line. More devices will likely be needed for most situations.
With little SPL increase the stacked PT-mini-6 planars will not have pro sound output but they will be OK for a normal home situation. You might purchase a few of these drivers and try them out to get an idea of how they sound as some of the users on the PE site report issues with distortion. I suspect some buyers are buying these tiny drivers and expecting grand sound without an adequate crossover.
Jim
http://www.audioroundtable.com/misc/nflawp.pdf
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Jim,
Right.... some of those issues are not consequential with a separate amp just for the tweeters and an electronic crossover. Its easy to adjust the output without having to worry about an l-pad because the sensitivities don’t match.
And yes in the nearfield 9 feet back, its not likely to be an issue.
I’m going to be using 12, btw, which will give me almost a 40 inch line, and and OK impedance calculation, particular for an active crossover. And since I’m equalizing the subwoofer to 27hz, its available for any mods I need in the upper ranges.
According to the PE site’s commenters, as well as the techs at PE, crossing at 5000 hz at 24 db/octave L-R, and using 12 of them, will sound great and be quite a bit away from distortion. Plus I won’t have to deal with intermodulation distortion feeding into the tweeter line.
And I know(because we’ve talked and I also talked with Roger Russell) that the comb filter distortion is not hearable if I sit still---anyway, but certainly the horizontal stuff that the Haas Effect cancels will simply be tken out of the equation.
My real question was more along the line of “what is the impact of suspending them directly in a line in front of the 2.5 inch mids. The mid sound should diffract around them. Certainly it will below, and as much as three-four octaves above. So diffraction issues shouldn’t be a problem.
But are there other effects? Like would they approximate open feeling of a single speaker full range line like you have built(excluding the bass of course)? What other impacts might I hear in the sound?
Sometimes it can be substantial, like the fact that I use individual 23 inch PVC tubes for each of the midranges stuffed completely with pink fiberglas.
Right.... some of those issues are not consequential with a separate amp just for the tweeters and an electronic crossover. Its easy to adjust the output without having to worry about an l-pad because the sensitivities don’t match.
And yes in the nearfield 9 feet back, its not likely to be an issue.
I’m going to be using 12, btw, which will give me almost a 40 inch line, and and OK impedance calculation, particular for an active crossover. And since I’m equalizing the subwoofer to 27hz, its available for any mods I need in the upper ranges.
According to the PE site’s commenters, as well as the techs at PE, crossing at 5000 hz at 24 db/octave L-R, and using 12 of them, will sound great and be quite a bit away from distortion. Plus I won’t have to deal with intermodulation distortion feeding into the tweeter line.
And I know(because we’ve talked and I also talked with Roger Russell) that the comb filter distortion is not hearable if I sit still---anyway, but certainly the horizontal stuff that the Haas Effect cancels will simply be tken out of the equation.
My real question was more along the line of “what is the impact of suspending them directly in a line in front of the 2.5 inch mids. The mid sound should diffract around them. Certainly it will below, and as much as three-four octaves above. So diffraction issues shouldn’t be a problem.
But are there other effects? Like would they approximate open feeling of a single speaker full range line like you have built(excluding the bass of course)? What other impacts might I hear in the sound?
Sometimes it can be substantial, like the fact that I use individual 23 inch PVC tubes for each of the midranges stuffed completely with pink fiberglas.
Yes, the sound will diffract around them, but as with all diffraction this will be heavily dependent of sizes and frequencies. I would expect substantial axial and polar effects once the wavelengths of the radiated sound reach 1/4 wave of the physical size of the obstruction. Basically, I don't think that it is a good idea. I would never do such a thing.
"My real question was more along the line of “what is the impact of suspending them directly in a line in front of the 2.5 inch mids."
I have a number of experiences with such arraignments, however ALL of them are using planer bass/mid "lines" with ribbon tweeter "lines" in front. I say "lines" as the examples range from 24" to 50 inch long. None were full floor to ceiling lines.
The examples range from relatively narrow planer bass/mids ( approx. 7 inches wide) to panels about 14 inches wide. The ribbons tweeters range from 2 inch wide to 1/4 inch wide, most around 1 inch wide. Crossovers were ALL much lower than you plan. They were anywhere from 350 hz to 1.5 khz. 12 and 6 db/oct passive. So there is a bit of range here in experiences.
Heres the deal, in every one of the examples there was an improvement in that the systems were less sensitive to placement in room and seated position. It wasn't a huge difference BUT it was noticeable. With this I noticed that the speakers were more neutral sounding on more material. There was less of that sounds great on one track and so so on the next. They were more consistently well balanced tonally and spatially.
That said I believe when set up just right I reached higher levels of wow, both on sound quality and image, with the standard tweeter to the side arraignment. I dont know why but suspect that with the tweeter to the side you can design to get the best handling of diffraction. and as the good Dr. says that seems the likely culprit.
In the end I designed a planer that had the tweeter conductors ridding on the same film as the woofer conductors and it was a concentric so tweeter right in middle of the woofer panel and on same plane. It was a pretty darned good setup especially when operated from 70hz on up.
IMO its worth trying what you mention IF its cheap to do and even then only because that tweeter is sooo tiny that physically you can make such a small structure (maybe small pipe to hold them?). I suspect however as some have mentioned that rigid aluminum diaphragm in the tweeter you show will have some serious issues at some freqs but maybe ok above 5k?? I would get one and measure.
I have a number of experiences with such arraignments, however ALL of them are using planer bass/mid "lines" with ribbon tweeter "lines" in front. I say "lines" as the examples range from 24" to 50 inch long. None were full floor to ceiling lines.
The examples range from relatively narrow planer bass/mids ( approx. 7 inches wide) to panels about 14 inches wide. The ribbons tweeters range from 2 inch wide to 1/4 inch wide, most around 1 inch wide. Crossovers were ALL much lower than you plan. They were anywhere from 350 hz to 1.5 khz. 12 and 6 db/oct passive. So there is a bit of range here in experiences.
Heres the deal, in every one of the examples there was an improvement in that the systems were less sensitive to placement in room and seated position. It wasn't a huge difference BUT it was noticeable. With this I noticed that the speakers were more neutral sounding on more material. There was less of that sounds great on one track and so so on the next. They were more consistently well balanced tonally and spatially.
That said I believe when set up just right I reached higher levels of wow, both on sound quality and image, with the standard tweeter to the side arraignment. I dont know why but suspect that with the tweeter to the side you can design to get the best handling of diffraction. and as the good Dr. says that seems the likely culprit.
In the end I designed a planer that had the tweeter conductors ridding on the same film as the woofer conductors and it was a concentric so tweeter right in middle of the woofer panel and on same plane. It was a pretty darned good setup especially when operated from 70hz on up.
IMO its worth trying what you mention IF its cheap to do and even then only because that tweeter is sooo tiny that physically you can make such a small structure (maybe small pipe to hold them?). I suspect however as some have mentioned that rigid aluminum diaphragm in the tweeter you show will have some serious issues at some freqs but maybe ok above 5k?? I would get one and measure.
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OK... I get that. But 1/4 wave of the physical size of the obstruction is above 20Khz---which is three octaves down from the crossover.
Is that the only concern you would have?
Looking at the response of that tweeter there is a wiggle at 5k that might have quite a bit of energy storage there. I have seen ribbon / planers with similar issue. The FR not to bad BUT the CSD might show a long tail there and with that a harshness in extended listen.
They would fit glued on a small 1/4 inch by .90 inch x 42 inch piece of oak supported with three bolts into the baffle which holds the 2.5 inch mid ranges.
But cheap.... no. Its something you do: you either choose to to that, or you put them up against the edge of the 2.5 inch mids, which makes the edge of the ribbon not more than about 2 inches from the center of the midrange line.
A line of the tweeters is $250. Some people would find that cheap, but I am not one of them.
That issue will dealt with or ignored. The items are in my possession. Crossing at the wiggle(active 24 db. L-R) may have an impact on dropping it(or not), but I’m not having to deal with it in a passive crossover anyways.
It was a factor that I chose to ignore in purchasing them because people said that in groups of more than 5(I’m using 12), crossed at 5Kz or above, they were stunning.
"It was a factor that I chose to ignore in purchasing them because people said that in groups of more than 5(I’m using 12), crossed at 5Kz or above, they were stunning."
Yes. People would be surprised at how good even to crudest of planers can be when you up the surface area enough.
Yes. People would be surprised at how good even to crudest of planers can be when you up the surface area enough.
This is exactly what I needed to know. The placement on the side and the placement in the center is only a distance of less than 2 inches. I suspect that from a distance of 10 feet listening in the nearfield, that the two placements would probably be the same.
Thanks again for taking the time to answer.
Roger Russell tells me that he would not expect frequency response changes, but that he would expect issues on the time domain.
Since Lowmass suggests that the Wow Factor is lessened, and the fact that Gedlee suggests issues in the diffraction, the only person who, without specification, said that it was all up, was Bill Fitzmaurice.
Since the planar tweeter line will actually be less than 2 inches from the edge of the planar to the center of the mid in the horizontal direction, I see no reason to use the line across the center---EVEN IF IT WOULD LOOK REALLY CLASSY. For me to do it, I would have needed to hear people tell me that the only reason it wasn’t done was because of the complexity of doing it. That’s not what I heard.
I thank everyone for their suggestions. As to measurement, people seem to have different views of how exactly to measure the output of a line array, and it often involves more than one microphone. I’m only making them for me, so actual measurement is less important than how they sound to my brain.
Since Lowmass suggests that the Wow Factor is lessened, and the fact that Gedlee suggests issues in the diffraction, the only person who, without specification, said that it was all up, was Bill Fitzmaurice.
Since the planar tweeter line will actually be less than 2 inches from the edge of the planar to the center of the mid in the horizontal direction, I see no reason to use the line across the center---EVEN IF IT WOULD LOOK REALLY CLASSY. For me to do it, I would have needed to hear people tell me that the only reason it wasn’t done was because of the complexity of doing it. That’s not what I heard.
I thank everyone for their suggestions. As to measurement, people seem to have different views of how exactly to measure the output of a line array, and it often involves more than one microphone. I’m only making them for me, so actual measurement is less important than how they sound to my brain.
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You will need to contact Roger yourself. I’m not going to be the go between for you. Roger is easy to talk to and will respond to your email about a line of tweeters placed in front of a line of woofers or mids..
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I would have made this point if it had not already been made.
The time/frequency co-dependence guarantees that if the time domain changes then the frequency domain must change as well (except in some rare circumstances of course, which would definitely not be true in this case.)
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