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Magnepan Needs Your Help: 30.7 for Condo's Prototype Audition

Burning Sounds

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#21
Those don't look like Peter Gunn's work to me. And he generally steered clear of the ribbon-tweeter models anyways.
But, a nice looking set of speakers with LX521 dipole woofers mated. I imagine that setup sounds pretty good, if integrated properly.

Dave.
Yes I was aware of Peter Gunn's work when I had mine rebuilt. Some of his work looked very nice - although I was never convinced of the "better sound" argument for hardwood frames. Although I seem to remember he modified x-overs, too??

Originally I actually purchased the LX521 plans just to build the woofers for my Maggies. When it came to purchase the LX521 bass drivers here in the UK there was quite a savings if I bought the entire LX521 set. So I built the woofers first for the Maggies and then the LX521 upper baffle at a later date. The same carpenter that built the Maggie frames CNC'd the LX521 upper baffle for me from five bonded pieces of oak to minimize any chance of warping. The LX521 is my primary speaker, but I still like the Maggies - my first pair was bought more 40 years ago.
 

josh358

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#22
Producing bass from an array of small drivers instead of a single big driver is not a new idea, nor is a conventional driver set up as a dipole. But getting it to work together well still requires some engineering. Even their mid-sized model, the 3.6 or 3.7, are physically large and also require a medium to large room. They are large because they have limited excursion, but large surface area drivers at moderate SPLs are barely moving, which reduces distortion.

Most of the panel's size is dedicated to bass; if the panel only did midrange on up it would be less than half its size, so what Magnepan is doing here makes sense if you want a smaller speaker. But I don't see how a smaller speaker solves the problem of making them work in small rooms. Dipoles (even small ones) are more sensitive to room placement & configuration than normal speakers. They sound best in a medium-large room, placed a good distance away from the walls. I don't see how they could sound good in an apartment, condo or other small room.
3' from the front wall is pretty much the minimum, and 1' from the side walls (the dipole null helps here -- the problem is that if you move them closer, they develop too much bass -- although that affects any speaker and there's a setup, the Limage setup, that seems to work well with Maggies.

Otherwise, I've found that small rooms can work with careful placement and acoustic treatment if necessary. My own room is only 13' x 14' and it took me quite a while to get the kind of sound I wanted.

One clever tweak that someone just mentioned in another thread: The issue here is the path length of the backwave -- ideally, you'd have about a 20 ms delay (approx 10'), but in practice, they start to work nicely at about 5'. Basically, they develop more depth as you move them out further from the wall. So -- angle the speakers so the backwave strikes the side walls at the an angle so that it reflects to the center of the front wall. From there, it will reflect to the *other* sidewall and then back to your ears. So the path length is twice the distance from the speaker to the sidewall + twice the distance from the sidewall to the center wall, and you will develop a great deal of depth! This is basically a passive implementation of the reflection-free zone approach used in recording studios.
 

josh358

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#23
What bothers me is that Wendell Diller seems to think this is so innovative that Magnepan can get a patent.
The patent isn't on combining a dynamic dipole woofer array with a planar and DSP. Anyone can do that. I was sufficiently involved in the development to know what is being patented, and it's certainly innovative enough to be patentable.
 

dreite

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#24
The patent isn't on combining a dynamic dipole woofer array with a planar and DSP. Anyone can do that. I was sufficiently involved in the development to know what is being patented, and it's certainly innovative enough to be patentable.
The whole thing is much too coy for me.
I'm not sure why Magnepan need to resort to hand-waving marketing-speak in regards to this.

I assume that if they decide not to produce the product, the "innovation" will be released so we can all utilize it????

Dave.
 

josh358

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#25
Not sure what you mean by hand-waving, since the innovation is a real one. Which isn't to say that marketing didn't contribute to the decision to patent -- hybrids have a bad rep, and Magnepan wanted a way to say "this is different."

But the main reason was to insure that the inventor of the concept wouldn't lose the rights to his intellectual property -- he's a consultant rather than an employee of Magnepan. For that reason, I doubt that they'll disclose if they don't file for a patent.

Finally, the third reason was that a provisional patent would allow them to take the prototype on tour. But since they're taking it on tour and AFAIK haven't yet filed the patent, that presumably is no longer a consideration.
 

ajawamnet

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#26
Not sure what you mean by hand-waving, since the innovation is a real one. Which isn't to say that marketing didn't contribute to the decision to patent -- hybrids have a bad rep, and Magnepan wanted a way to say "this is different."

But the main reason was to insure that the inventor of the concept wouldn't lose the rights to his intellectual property -- he's a consultant rather than an employee of Magnepan. For that reason, I doubt that they'll disclose if they don't file for a patent.

Finally, the third reason was that a provisional patent would allow them to take the prototype on tour. But since they're taking it on tour and AFAIK haven't yet filed the patent, that presumably is no longer a consideration.

We used to sell Magnapans at Opus One in Pittsburgh - interesting to see Butch's is filling that void (at the time I was at Opus it was Butch's Sound Shack)

Wow - provisional patent. Gotta be careful with that. I've seen situations when they do something like this, get mixed reviews and change something to address it, and void the provisional filing (you have to have everything in the provisional that will be in the utility patent. Also, having a loose provisional can be damaging to the inventor:

https://www.ipwatchdog.com/2018/01/20/provisional-applications-good-bad-ugly/id=92623/
"Bad provisional applications can be used against the inventor later as a weapon to demonstrate there was no invention, or at least that the invention had not ripened past the idea stage at the critical moment the invention was memorialized at the time of filing the provisional patent application. "

When we got bought by Verizon, we were looking for ways to shortcut the time. One was petition to make special, since it dealt with security of the US and was wanted by a branch of the fed. But we were warned about the requirements for prior art searches and how that can destroy any IP protection. We then mentioned the provisional and the Verizon as well as Softbank (one of our investors) again mentioned the limitations that a poorly done provisional can impose - to the point of invalidating the IP itself.

Also note - I recently had an interesting conversation with two drunk patent attorneys that worked at the patent office (I'm in D.C.) Quite fascinating and eyeopening on how the US patent system is being changed to favor first to file (2011 it changed). Sucks.

And I hope they did a foreign filing too, since they can knock foreign rights by showing it for sale... been there, done that. For instance, they now publish applications prior to grants. If you have not filed foreign, you will knock your rights overseas with your own patent application

https://www.ipwatchdog.com/2018/11/11/pct-international-patent-application-filing-basics/id=103231/

that and: https://ocpatentlawyer.com/pros-cons-securing-worldwide-patent-protection-steps/

You need to file a patent application before any marketing activities to preserve your right to seek worldwide patent protection. The reason is that most foreign countries require the “absolute novelty.” That is, if you file a patent application after marketing activities, your own activities makes your patent filing not novel.

In contrast to “absolute novelty” countries, the United States is a “relative novelty” country, because the U.S. government allows inventors to commercialize their invention for up to one year before the patent application must be filed. In other words, the invention does not have to be “absolutely,” but only “relatively” novel at the time of filing, due to the inventor’s own marketing efforts. If you are not interested in worldwide patent protection, you might think that you don’t have to file a patent application until one year after your marketing activities. However, that is not recommended because of the First Inventor to File rule [include link]. Just remember that if you start your marketing efforts before filing a patent application, worldwide patent protection is generally waived (see Figure below). If you decide that you need worldwide patent protection after you have already started your marketing activities, then you need to understand what you can and cannot get at this point so contact a patent attorney.

If this is truly novel, he better be careful...
 

MRC01

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#27
... One clever tweak that someone just mentioned in another thread: The issue here is the path length of the backwave -- ideally, you'd have about a 20 ms delay (approx 10'), but in practice, they start to work nicely at about 5'. Basically, they develop more depth as you move them out further from the wall. So -- angle the speakers so the backwave strikes the side walls at the an angle so that it reflects to the center of the front wall. ...
Maggies have another constraint on toe angle: the tweeter should be about 1" further from the listener than the center of the panel - for proper phase. That said, any toe angle makes the back wave distance traveled greater than the speaker's distance directly to the front wall (in front of the listener, behind the speaker). However, this discussion treats the bass like it's a laser bouncing around the room. I doubt the bass frequencies are that directional, even from a large panel dipole. Their wavelength is bigger than the panel dimensions (50 Hz is roughly 21 feet), so bass should be roughly line source propagation, and shouldn't that make the toe angle less important?
 

josh358

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#28
Maggies have another constraint on toe angle: the tweeter should be about 1" further from the listener than the center of the panel - for proper phase. That said, any toe angle makes the back wave distance traveled greater than the speaker's distance directly to the front wall (in front of the listener, behind the speaker). However, this discussion treats the bass like it's a laser bouncing around the room. I doubt the bass frequencies are that directional, even from a large panel dipole. Their wavelength is bigger than the panel dimensions (50 Hz is roughly 21 feet), so bass should be roughly line source propagation, and shouldn't that make the toe angle less important?
Yep. At higher frequencies, reflections are specular, but at lower frequencies, that isn't the case. I think in the latter case we just throw up our hands and say we can't do anything about it, so why worry. :) This is true even of the reflection-free zone in a studio control room -- the facets won't redirect a long wavelength.
Really, that's true of a lot of things -- absorption, diffusion, you name it -- that tend to become ineffective at bass frequencies so other means are used to control the bass, typically bass traps of various kinds.

In any case, the relationship of toe-in to bass is a bit complex. If the bass panel is parallel to the front wall, you get maximal cancellation of the lateral room modes, because they're smack dab in the middle of the dipole null. But you also get maximal effect from the rear wave cancellation where the speakers are 1/2 wavelength from the wall. So you're improving one thing and disimproving another. But I think it's moot with the single-panel Maggies since you can't adjust the woofer angle independently, and as you say, you want to stay on the crossover axis. If I ever do this, I'll have to biamp my mid-tweet panels so I can use delay, an expensive endeavor!

The alternative would be taking the RFZ approach and putting facets on your front wall to deflect the sound where you want it -- either large ones (I saw a planar room designed by Rives that took this approach) or Fresnel reflectors.
 
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RayDunzl

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#29
Reflections:

MartinLogan reQuest ESL hybrid (1998 model, still going strong)
JBL LSR 308

I have dipoles and a relatively untreated room.

Measuring at the listening position, the highest reflection level shown in an extended Impulse Response is about 25dB below the direct sound (as I interpret the readings), in my non-anechoic room

There are JBL LSR 305 adjacent to the mains. Their room reflections are more numerous, and as high as -10dB relative to the direct sound.

Spatially, the dipoles sound more precise, the cones less distinct. I don't listen to the JBLs critically. They distort early at higher listening levels. But I use them all day long for TV and Radio and other casual listening.

Red - JBL
Black ML
"Uncorrected" traces for both, left and right speakers active, measured at 10 feet.

1576534685111.png




ML Black:
1ms - bounce off mic stand/top of sofa
7ms - dipole bounce off front wall
27ms - double room length bounce

JBL Red
Never tried to figure out what the bounces are.

1576535073261.png




Unsmoothed Frequency Response over the dipole range:

I've been told to "ignore" this, it is said I can't hear it, but, I hear something.

Main dipole bounce off front wall at 220Hz, nd multiples (more or less).

The panel crosses to the cone woofer at 180Hz, so that is chosen for the low end here.

1576535368295.png


Measured nearfield, the JBL does not show that hash, so, I infer it must be room reflections.
 
Last edited:

RayDunzl

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#31
Your reflections look to be at only -8.5dB relative to the direct...
 

josh358

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#32
Reflections:

MartinLogan reQuest ESL hybrid (1998 model, still going strong)
JBL LSR 308

I have dipoles and a relatively untreated room.

Measuring at the listening position, the highest reflection level shown in an extended Impulse Response is about 25dB below the direct sound (as I interpret the readings), in my non-anechoic room

There are JBL LSR 305 adjacent to the mains. Their room reflections are more numerous, and as high as -10dB relative to the direct sound.

Spatially, the dipoles sound more precise, the cones less distinct. I don't listen to the JBLs critically. They distort early at higher listening levels. But I use them all day long for TV and Radio and other casual listening.

Red - JBL
Black ML
"Uncorrected" traces for both, left and right speakers active, measured at 10 feet.

View attachment 42745



ML Black:
1ms - bounce off mic stand/top of sofa
7ms - dipole bounce off front wall
27ms - double room length bounce

JBL Red
Never tried to figure out what the bounces are.

View attachment 42746



Unsmoothed Frequency Response over the dipole range:

I've been told to "ignore" this, it is said I can't hear it, but, I hear something.

Main dipole bounce off front wall at 220Hz, nd multiples (more or less).

The panel crosses to the cone woofer at 180Hz, so that is chosen for the low end here.

View attachment 42747

Measured nearfield, the JBL does not show that hash, so, I infer it must be room reflections.
You should be able to hear the null from that main dipole bounce. Above the Schroeder frequency, I don't think it's much of an issue. Great impulse response, though, better than I've been able to get with my Tympanis and a very undersized listening room.
 

MRC01

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#34
Your reflections look to be at only -8.5dB relative to the direct...
Yes, and the timing correlates to front-side wall reflection distance. The back & front walls and corners are well damped. But the room sounds too dead for my taste when I also damp the side walls. The CSD shows it's more or less evenly distributed across the spectrum.
 

josh358

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#35
Yes, and the timing correlates to front-side wall reflection distance. The back & front walls and corners are well damped. But the room sounds too dead for my taste when I also damp the side walls. The CSD shows it's more or less evenly distributed across the spectrum.
Have you tried diffusion on the front wall, at the point at which it reflects to the side wall? That should reduce the amplitude of the sidewall reflection without making the room too dead -- see my measurement with and without diffusion above.

I haven't had much luck with diffusion on the side walls, perhaps because the diffusers are poorly behaved at those angles of incidence, or perhaps because they're too close to the listening position. I'm not any fonder of absorption there than you are.
 

MRC01

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#36
Have you tried diffusion on the front wall, at the point at which it reflects to the side wall? That should reduce the amplitude of the sidewall reflection without making the room too dead ...
No, but I'll add this to my list of things to try. The room sounds fantastic but there is always room for improvement.
 

josh358

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#37
No, but I'll add this to my list of things to try. The room sounds fantastic but there is always room for improvement.
I and some others have had great results putting diffusion in the front corners. In my room, I have them in front of the bass traps, making an isoceles triangle.

Diffusion is generally the preferred room treatment for dipoles, which dump 4.8 dB less than omnis into the off-axis sound and so require a liver acoustic. Wendell Diller said that on his nationwide 30.7 tour the best sounding rooms all had something in common -- diffusion.
 

josh358

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#38
We used to sell Magnapans at Opus One in Pittsburgh - interesting to see Butch's is filling that void (at the time I was at Opus it was Butch's Sound Shack)

Wow - provisional patent. Gotta be careful with that. I've seen situations when they do something like this, get mixed reviews and change something to address it, and void the provisional filing (you have to have everything in the provisional that will be in the utility patent. Also, having a loose provisional can be damaging to the inventor:

https://www.ipwatchdog.com/2018/01/20/provisional-applications-good-bad-ugly/id=92623/
"Bad provisional applications can be used against the inventor later as a weapon to demonstrate there was no invention, or at least that the invention had not ripened past the idea stage at the critical moment the invention was memorialized at the time of filing the provisional patent application. "

When we got bought by Verizon, we were looking for ways to shortcut the time. One was petition to make special, since it dealt with security of the US and was wanted by a branch of the fed. But we were warned about the requirements for prior art searches and how that can destroy any IP protection. We then mentioned the provisional and the Verizon as well as Softbank (one of our investors) again mentioned the limitations that a poorly done provisional can impose - to the point of invalidating the IP itself.

Also note - I recently had an interesting conversation with two drunk patent attorneys that worked at the patent office (I'm in D.C.) Quite fascinating and eyeopening on how the US patent system is being changed to favor first to file (2011 it changed). Sucks.

And I hope they did a foreign filing too, since they can knock foreign rights by showing it for sale... been there, done that. For instance, they now publish applications prior to grants. If you have not filed foreign, you will knock your rights overseas with your own patent application

https://www.ipwatchdog.com/2018/11/11/pct-international-patent-application-filing-basics/id=103231/

that and: https://ocpatentlawyer.com/pros-cons-securing-worldwide-patent-protection-steps/

You need to file a patent application before any marketing activities to preserve your right to seek worldwide patent protection. The reason is that most foreign countries require the “absolute novelty.” That is, if you file a patent application after marketing activities, your own activities makes your patent filing not novel.

In contrast to “absolute novelty” countries, the United States is a “relative novelty” country, because the U.S. government allows inventors to commercialize their invention for up to one year before the patent application must be filed. In other words, the invention does not have to be “absolutely,” but only “relatively” novel at the time of filing, due to the inventor’s own marketing efforts. If you are not interested in worldwide patent protection, you might think that you don’t have to file a patent application until one year after your marketing activities. However, that is not recommended because of the First Inventor to File rule [include link]. Just remember that if you start your marketing efforts before filing a patent application, worldwide patent protection is generally waived (see Figure below). If you decide that you need worldwide patent protection after you have already started your marketing activities, then you need to understand what you can and cannot get at this point so contact a patent attorney.

If this is truly novel, he better be careful...
Interesting and informative, thanks -- I'll pass it on.
 
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