+1. agreed. JohnK is often not given enough credit for pointing everybody the right way.
Yep, they clearly made the room part of the design. I also take LX521 to be a no compromise i.e "a reference" design but have no room to accommodate them as such. I am already looking at putting them together with distributed bass (2 subs around the room), even though I believe for a 120Hz XO SL recommends bass drivers within 2 feet of the top section.
In the room of my first choice, I also cannot give them the required distance to the wall behind!! thus it just kills me now 😡 that SL only puts forward the added bass of LX521 as a true advantage over Mini, and little seems to have been traded off overall; which brings me to my question: can LX521 placement closer against the wall be also experimented with by trying some attenuators behind? in what shape and sizes should they come?
I built some quadratic diffusers, and they actually complement my decor pretty nice. They look like a sculpture if you finish them properly.
Absorbers on front wall do work well with dipoles positioned close to the wall. But you must do testing and measuring ourself. I think that big problems will not be realized.
Front wall reflections are mostly in 500-1200Hz region. Measure at listening position, both speakers separately - response with short IR gating, long gating and decay waterfall. Also RTA and RT30, EDT. Every setup in a room at home will have some problems! With dipole radiation, sidewalls are usually not a problem, which gives you odds regarding total performance.
Front wall reflections are mostly in 500-1200Hz region. Measure at listening position, both speakers separately - response with short IR gating, long gating and decay waterfall. Also RTA and RT30, EDT. Every setup in a room at home will have some problems! With dipole radiation, sidewalls are usually not a problem, which gives you odds regarding total performance.
Back to back with a polarity switch on one and an L pad on the front one (to similate a 901) is interesting...
Dan
treatments for HT
On the subject of treatments, I thought it was just me that was having trouble understanding m center channel movie dialog, but after checking on HT forums, its a common complaint. Many said dialog sounded better with NO center channel speaker and just running plain ol' stereo. I tried it and I agree. Just wonder if anyone can comment on what radiation patterns and treatments seem to be conducive to better (virtual) center channel movie dialog intelligibility..
Dan
On the subject of treatments, I thought it was just me that was having trouble understanding m center channel movie dialog, but after checking on HT forums, its a common complaint. Many said dialog sounded better with NO center channel speaker and just running plain ol' stereo. I tried it and I agree. Just wonder if anyone can comment on what radiation patterns and treatments seem to be conducive to better (virtual) center channel movie dialog intelligibility..
Dan
With 5.n systems the center channel delay and level settings are very very sensitive! +-1ms will change phase match drastically at the very critical upper mid -low treble range. Some amps don't have adjustable delays by ms, only by distance -but try it!
My HT setup has best center image and speech/soloist clarity/coherence with the center channel active! Much better than with just monopole or dipole mains in stereo.
My HT setup has best center image and speech/soloist clarity/coherence with the center channel active! Much better than with just monopole or dipole mains in stereo.
The LXmini advantage
In the past few days I have had a bit of a eureka experience where the LXmini advantage becomes apparent.
Even with directivity under control, the earliest arriving specular reflections from the listening room boundaries need to have the following attributes.
1 Be sufficiently delayed from the direct sound. Some suggest 10mS others 6 mS.
2 Be sufficiently lower in level than the direct sound.
"sufficiently" means amounts that prevent the perception of secondary sources and the resulting cluttered acoustic scene.
It has long been recognised that diffusion in room trouble spots, such as the front wall behind dipoles is usefull, but, to me at least, the reasons have not been spelled out.
Diffuse sound equates to decorrelated sound. Decorrelated sound has no perceivable direction of source, thus we have no false sources and no confused acoustic scene.
Linkwitz's clever idea was to add the diffusor to the speaker instead of the listening room wall, making the speakers sound good in any room. The directivity changes from omni to cardiode to dipole to a shrinking radiation area are probably best viewed as a bit of a collateral artifact in the overall scheme of the design.
Yes, the design contradicts some of SL's long held tenets, but as ever, he is prepared to move forward in his thinking in the light of new insights.
Keith
In the past few days I have had a bit of a eureka experience where the LXmini advantage becomes apparent.
Even with directivity under control, the earliest arriving specular reflections from the listening room boundaries need to have the following attributes.
1 Be sufficiently delayed from the direct sound. Some suggest 10mS others 6 mS.
2 Be sufficiently lower in level than the direct sound.
"sufficiently" means amounts that prevent the perception of secondary sources and the resulting cluttered acoustic scene.
It has long been recognised that diffusion in room trouble spots, such as the front wall behind dipoles is usefull, but, to me at least, the reasons have not been spelled out.
Diffuse sound equates to decorrelated sound. Decorrelated sound has no perceivable direction of source, thus we have no false sources and no confused acoustic scene.
Linkwitz's clever idea was to add the diffusor to the speaker instead of the listening room wall, making the speakers sound good in any room. The directivity changes from omni to cardiode to dipole to a shrinking radiation area are probably best viewed as a bit of a collateral artifact in the overall scheme of the design.
Yes, the design contradicts some of SL's long held tenets, but as ever, he is prepared to move forward in his thinking in the light of new insights.
Keith
Member
Joined 2006
Great explanation.🙂
What if I drill a sizable hole at the back of the tweeter pipe of my plutos...
Would that work!?😀
What if I drill a sizable hole at the back of the tweeter pipe of my plutos...
Would that work!?😀
WOW. I think you really nailed it here.
The cardioid horns I made for my car sounded spectacular. And what you've posted would help explain that. You don't need to completely obliterate that rear wave, if you can attenuate radiation by even 6-10dB it will make an audible difference.
I found that the caridoid horns were more intelligible than monopoles, basically it was easier to hear low-level details than the monopole horns I was accustomed to.
Perhaps this is because the lower midrange on a monopole horn will 'wrap' around, and then get reflected back when it hits the rear wall. A cardioid horn will be less susceptible to this; the sound that wraps around will be partially nullified by radiation from the rear.
Of course, a very large horn would work even better, but even a 12" wide horn is pushing it when you're using a car.
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CFT, thanks for your remarks. I think the Pluto crosses over to the tweeter at around 900Hz? Something else that I had been mulling over was the fact that a number of well regarded speaker designs seem to get by with major "gear changes" in directivity at around 700 odd Hz, such as the Geddes Suma.
It occurs to me that this is the frequency where the human auditory system changes direction sensing from arrival time/phase differences to intensity differences due to head shading. Maybe this upper part of the spectrum needs more attention to be paid to bad reflections than lower down.
The problem with the pluto tweeter is that it is monopole in nature and thus we are not able to get a null that we can aim at the nearest sidewalls to reduce the level of these reflections. Boring holes in the back of it may give it some dipole attributes but would not constitute a diffusor, at least along the lines of the LXmini diffusors. My guess would be that hole boring would probably ruin the tweeter😡
When I first read SL's challenge to the speaker industry I thought it was a bit audacious, but when armed with the present insights you realise that the diffusors are a bit of magic sauce allowing these cheap speakers to punch way beyond their weight category!
It is a bit maddening that the Seas factory has gone on holidays/vacation when we are all waiting to get some reports on what all the excitement is about.
Keith
It occurs to me that this is the frequency where the human auditory system changes direction sensing from arrival time/phase differences to intensity differences due to head shading. Maybe this upper part of the spectrum needs more attention to be paid to bad reflections than lower down.
The problem with the pluto tweeter is that it is monopole in nature and thus we are not able to get a null that we can aim at the nearest sidewalls to reduce the level of these reflections. Boring holes in the back of it may give it some dipole attributes but would not constitute a diffusor, at least along the lines of the LXmini diffusors. My guess would be that hole boring would probably ruin the tweeter😡
When I first read SL's challenge to the speaker industry I thought it was a bit audacious, but when armed with the present insights you realise that the diffusors are a bit of magic sauce allowing these cheap speakers to punch way beyond their weight category!
It is a bit maddening that the Seas factory has gone on holidays/vacation when we are all waiting to get some reports on what all the excitement is about.
Keith
I understand it's best that all three fronts are identical. Since my mains will be some form of minis, a center channel is not an option for me for obvious reasons...
Dan
I was meaning to edit my initial post in this thread but it had timed out.
Sorry about the lack of rigor in discussing diffuse and decorrelated sounds. Of course mono sounds can be diffuse and lacking directional cues, but it is the decorrelation of the reflected sounds between the stereo channels that stops the ears from assigning directions to them.
In the second post the boxing analogy should have included the thought that maybe SL is punching below the belt in expecting industry products to be competitive with a design that has a paradigm shift in the form of a new way of controlling reflections besides time and intensity.
CFT, sorry I missread your suggestion re Pluto tweeters. You asked about modifying the mounting tube rather than the tweeter. I think that this has been discussed on the OPLUG forum. We need dipole directivity to narrow the radiation pattern at low frequencies. The question then arises what to do with the rear radiation. I don't know the details of this tweeter whether cone or dome? Sealed at the back or open?. Even if an open backed cone it would probably not have enough excursion capability for dipole operation.
Keith
Sorry about the lack of rigor in discussing diffuse and decorrelated sounds. Of course mono sounds can be diffuse and lacking directional cues, but it is the decorrelation of the reflected sounds between the stereo channels that stops the ears from assigning directions to them.
In the second post the boxing analogy should have included the thought that maybe SL is punching below the belt in expecting industry products to be competitive with a design that has a paradigm shift in the form of a new way of controlling reflections besides time and intensity.
CFT, sorry I missread your suggestion re Pluto tweeters. You asked about modifying the mounting tube rather than the tweeter. I think that this has been discussed on the OPLUG forum. We need dipole directivity to narrow the radiation pattern at low frequencies. The question then arises what to do with the rear radiation. I don't know the details of this tweeter whether cone or dome? Sealed at the back or open?. Even if an open backed cone it would probably not have enough excursion capability for dipole operation.
Keith
Member
Joined 2006
Hi Keith,
Thanks for the follow up.
The Pluto tweeter, Aura nsw2-326-8a, is a 2" "fullrange" open backed cone unit with an Fo of 250 Hz. See spec:
The Madisound Speaker Store
I suppose it could handle an fc of 700Hz.
Will take a look at the OPLUG. Thanks for the suggestion.🙂
Thanks for the follow up.
The Pluto tweeter, Aura nsw2-326-8a, is a 2" "fullrange" open backed cone unit with an Fo of 250 Hz. See spec:
The Madisound Speaker Store
I suppose it could handle an fc of 700Hz.
Will take a look at the OPLUG. Thanks for the suggestion.🙂
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SL stated that he preferred to diffuse the rear radiation in the upper midrange so the speaker wouldn't have as bad a reaction to room acoustics when the speaker is placed closer than 3 ft from the front wall of the listening room. If you look real close at the pictures, it looks to me like that tube around the high frequency driver is mostly there as a mount, and less as a diffuser. The rear vents of the driver are mostly outside of the tube. The tube grabs the driver by its magnet, and may even add some cavity effect (not good).
Personally, I would use a Peerless 3 inch TG driver (glass fiber cone - $22 at Madisound) (or the Vifa TC driver - paper cone $12 at Madisound) instead of the Seas driver for the upperband, and minimize the length of the tube so no cavity effect. If you don't want rear radiation I just hang some very thick furry cloth behind this upperband driver. The TG or TC driver has a better high end response (more extended and possibly smoother) than the Seas and is slightly smaller (3 inch instead of 4 inch) so better off axis response.
The rest of the design looks pretty good. If the woofer didn't have such a hard cone (and the upper-mid severe resonance that invariably comes with that) this system could use a passive crossover to save money if that's an issue (I'd definitely go 4th order active myself). Forcing a 5 or 6 inch woofer to go down to 40HZ is possible with active EQ (if the enclosure is sealed - not ported) but wouldn't do well at higher listening levels or in big rooms. Since the woofer is aimed straight up, most of it's energy goes to the ceiling, not the listener.
No.
A 6" woofer goes omni at 2.25khz. (speed of sound / diameter) = (13500 / 6") = 2250hz.
Because the speaker is omnipolar, a fraction of the radiation goes towards the ceiling, a fraction goes towards the listener, a fraction goes towards the wall.
Patrick, you're right. Thanks for the correction. If it's a 5 inch woofer I think it will get a little beamy at the top end though. Not a big deal.
Adhanda, a pipe of any length will have a cavity resonance effect, longer would do it worse. I would just front flushmount the driver in 1/2 inch wood (probably Oak or MDF), and put furry cloth behind it if I didn't want it to be dipole. Linkwitz claims that a driver has less coloration if it's mounted by its magnet, instead of its rim. I don't buy that. The rim is light weight compared to the magnet, and seems much more likely to ring if not well braced/damped by a baffle panel.
Right now I believe that only the lower mids (80HZ - 1kHZ) and the high treble (7kHZ and up) benefit from dipole operation. The Orions didn't have the kind of low bass I like (and am getting from my two monopole closed box actively EQ'd woofers), and dipoles in the upper mid are more likely to have frequency response differentials that will mess up imaging clarity a bit. Since inter-aural crosstalk screws up image clarity in the lower midrange, we depend on the upper-midrange imaging info to paint the scene. It's arguable that the upper midrange driver is better off having restricted radiation (2kHZ - 6kHZ), so there's less room acoustics at play causing inter-channel frequency response variations at the listening position which would deteriorate imaging clarity and consistency over frequency. You'd get less of the side wall reflection fake spaciousness, and more clarity of any imaging cues in the recording.
Adhanda, a pipe of any length will have a cavity resonance effect, longer would do it worse. I would just front flushmount the driver in 1/2 inch wood (probably Oak or MDF), and put furry cloth behind it if I didn't want it to be dipole. Linkwitz claims that a driver has less coloration if it's mounted by its magnet, instead of its rim. I don't buy that. The rim is light weight compared to the magnet, and seems much more likely to ring if not well braced/damped by a baffle panel.
Right now I believe that only the lower mids (80HZ - 1kHZ) and the high treble (7kHZ and up) benefit from dipole operation. The Orions didn't have the kind of low bass I like (and am getting from my two monopole closed box actively EQ'd woofers), and dipoles in the upper mid are more likely to have frequency response differentials that will mess up imaging clarity a bit. Since inter-aural crosstalk screws up image clarity in the lower midrange, we depend on the upper-midrange imaging info to paint the scene. It's arguable that the upper midrange driver is better off having restricted radiation (2kHZ - 6kHZ), so there's less room acoustics at play causing inter-channel frequency response variations at the listening position which would deteriorate imaging clarity and consistency over frequency. You'd get less of the side wall reflection fake spaciousness, and more clarity of any imaging cues in the recording.
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Bob,
I talked to SL recently and be assured he has thought about those things.
-The tube on the back is not just a mount and the tube length is intentional
-Drivers are heavily EQ'ed so you can't substitute another driver easily, and a conventional crossover wouldn't be simple, if it were possible to even do the same.
-The woofer doesn't send most of its energy to the ceiling as has already been mentioned.
I contacted him because there seem to be so many polarized opinions, mostly from people who haven't heard them. I've listened to various of his previous speakers at Burning Amp and they always sounded especially good, and that's the point right? So I had to know! I live in SF so could pop up to audition the pair he has at Sea Ranch.
Well they DO sound very good. I won't go on about them too much because I'll be accused of sounding like a magazine or some such, but in a medium room there is no sign of strain, even with the EQ. Resolution is noticeably very good and the high end sparkling-(although keep in mind I'm 61) Clearly the upper driver is pretty special, and the woofer has lots of excursion so they sound effortless.
The presentation is very interesting. It's not only that the imaging is very good, it's that the sound just materializes in mid air. NO awareness of speakers at all and sitting off center doesn't destroy the effect as much as you'd expect. They don't remind me of the LX521 that much, except for the high res and lack of resonances, because they aren't anchored with the really solid deep bass that the 521's have, though it's been a while since I heard the 521's in an optimal room,. However I think that helps to create the disappearing act. I think the tone is quite good too.
IMHO there's something special going on here but I haven't listened to every commercial and DIY speaker out there..then, who has?
Oh one more thing- I didn't like the look of the upper tube at all in the photos, but it's hard to realize how small these speakers are. Instead of a clumsy big cylinder on top, they look delicate and kinda cute.
Mark
I talked to SL recently and be assured he has thought about those things.
-The tube on the back is not just a mount and the tube length is intentional
-Drivers are heavily EQ'ed so you can't substitute another driver easily, and a conventional crossover wouldn't be simple, if it were possible to even do the same.
-The woofer doesn't send most of its energy to the ceiling as has already been mentioned.
I contacted him because there seem to be so many polarized opinions, mostly from people who haven't heard them. I've listened to various of his previous speakers at Burning Amp and they always sounded especially good, and that's the point right? So I had to know! I live in SF so could pop up to audition the pair he has at Sea Ranch.
Well they DO sound very good. I won't go on about them too much because I'll be accused of sounding like a magazine or some such, but in a medium room there is no sign of strain, even with the EQ. Resolution is noticeably very good and the high end sparkling-(although keep in mind I'm 61) Clearly the upper driver is pretty special, and the woofer has lots of excursion so they sound effortless.
The presentation is very interesting. It's not only that the imaging is very good, it's that the sound just materializes in mid air. NO awareness of speakers at all and sitting off center doesn't destroy the effect as much as you'd expect. They don't remind me of the LX521 that much, except for the high res and lack of resonances, because they aren't anchored with the really solid deep bass that the 521's have, though it's been a while since I heard the 521's in an optimal room,. However I think that helps to create the disappearing act. I think the tone is quite good too.
IMHO there's something special going on here but I haven't listened to every commercial and DIY speaker out there..then, who has?
Oh one more thing- I didn't like the look of the upper tube at all in the photos, but it's hard to realize how small these speakers are. Instead of a clumsy big cylinder on top, they look delicate and kinda cute.
Mark
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Sounds similar to my impression of the Chinese manufacturered version of the Pluto earlier this year at a local HiFi show. I was struck by the way the music didn't seem to be 'attached' to the speakers at all and by the lack of identifiable 'speakerishness'. I think the enclosure form/ design and materials use is very clever on the Plutos and the LXmini.
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