Erik: There's a surprising amount of anger in this thread I think - any particular reason? If you had to get angry every time you saw an overpriced audio product you wouldn't be doing much else 
I'd be willing to bet that the percentage of people that frequent diyaudio yet own ready-made speakers in this sort of price range is small trending towards non-existing. We're simply not the market around here - and we never will be.
The only comment I'd offer is that I'm thinking "engineering statement" as well. Remember that B&O has been in a crisis for a long time now and inevitably it was announced a little while ago that the board has received takeover offers. It's fairly clear to me that this sort of project is a good way of demonstrating the capabilities in design, engineering, acoustics etc. that a prospective buyer would be interested in - and be willing to pay for, just as Harman did a while ago for B&O Automotive. Of course the BL90 doesn't do it on its own, but consider the trickle-down perspectives as technology improves and suddenly it starts making more sense.
B&O is a small player, so if they were taken over by a larger player with more production volume their products and technology could get much closer to mass-market that they are now.
/U.
I'd be willing to bet that the percentage of people that frequent diyaudio yet own ready-made speakers in this sort of price range is small trending towards non-existing. We're simply not the market around here - and we never will be.
The only comment I'd offer is that I'm thinking "engineering statement" as well. Remember that B&O has been in a crisis for a long time now and inevitably it was announced a little while ago that the board has received takeover offers. It's fairly clear to me that this sort of project is a good way of demonstrating the capabilities in design, engineering, acoustics etc. that a prospective buyer would be interested in - and be willing to pay for, just as Harman did a while ago for B&O Automotive. Of course the BL90 doesn't do it on its own, but consider the trickle-down perspectives as technology improves and suddenly it starts making more sense.
B&O is a small player, so if they were taken over by a larger player with more production volume their products and technology could get much closer to mass-market that they are now.
/U.
Erik: There's a surprising amount of anger in this thread I think - any particular reason? If you had to get angry every time you saw an overpriced audio product you wouldn't be doing much else
TRUE! I think it's because I feel some obligation to save those that may come after us.
I didn't know what state they were in financially. It does make more sense as a technology statement product than as a real living room product though, much like a concept car.
If it were wrapped in something more like the McIntosh speakers with their mini-tweeter arrays and only cost $70,000 a pair that would be something!
Best,
Erik
Thanks Patrick. Fun to read!
I have listened to Beolab 90 as well. I was impressed and I seldom am when listening to speakers. Especially at stores or demo rooms with no acoustics treatment. I find most sound mediocre at the very best.
The Beolab 90 was placed closed to the frontwall. Sidewalls were also close but the sidewalls only extended a 1 m or so. Distance to rear wall was far.
I was able to hear them both in wide and narrow mode. Omni wasn't ready yet, but I've never cared much for omni coverage. No room correction was used.
In narrow mode they sounded great and took much of the room contribution out; giving great clarity, localization and pin-pointing. The bass was powerful and full. No lean presentation which is so typical of much hifi today.
In wide mode the imaging collapsed but gave a wider soundstage. But I also found them to sound fatiguing in this mode, probably caused by the high gain early reflections and a less constant polar. This might have been better if they stood out further in the room, delaying the reflections. However, the wide mode is too wide in my opinion. There's really no need for a 100-120 degrees dispersion, sending energy towards even the frontwall and corners.
I also have a pair of Geddes speakers, Abbey. I listened to the Abbeys right after I came home with the same tracks. My home theater room with the Abbeys is heavenly treated and uses multiple subwoofers. I noticed that the Beolab 90 had better openness and clarity compared to my Abbey setup. Other than that there wasn't much difference besides my setups having a more powerful deep bass presentation with the multiple subs (two bandbass' and one Tuba HT horn). But obviously comparing a non treated room with a treated room is unfair. I'm quite sure the Beolab 90 would have sounded better than my Abbeys in the same room. The polar of the Beolab 90 in narrow is constant over a much wider frequency area.
But what about Beolab 90 compared to a bigger horn setup? Do they sound as engaging? No. Do they have the same openness, resolution and clarity? No. Do they sound as coherent as speakers with a low cross over? No.
My reference here is Klipsch K402 by the way. With a beryllium diagraphm driver and low Xover they are in other league. Even with a frontfiring 15" below the horn with no CD.
It would be hard to compare Don Keele's CBT36 vs Beolab 90 in narrow mode because of the different coverage. But in wide mode, I'm certain the CBT36 (with subwoofer!) creams them. The CBT36 has a more uniform horizontal response, somewhat narrower beamwidth, and they are text book vertically while the Beolab 90 will have considerably lobing in the vertical plane.
What I would like to see and have thought about it for a long time is doing something similar with CBT. A way to change the beamwidth, for example between 80/90 degrees and 45 degrees but with the vertical benefits of CBT. This is possible but it will take a lot of drivers and amps!
To sum up I will say that while changing beamwidth of Beolab 90 is fun and a gimmick I'm not sure there's any point with the beamwidth in wide and omni. Wide mode is wider than what's really needed and causes too much acoustic problems. And omni never sounds good IMO in any small rooms. Either the wide mode should have been something like 70-90 degrees or they could have dropped it. And for the latter it's possible to do something similar much cheaper with another design.
The question then becomes; is there really any point to this? Besides being a cool gimmick that will sell on it's own my opinion is that it really isn't. However, it may be the window to the future where better an more appropriate beamwidth coverages/modes can be chosen.
I have listened to Beolab 90 as well. I was impressed and I seldom am when listening to speakers. Especially at stores or demo rooms with no acoustics treatment. I find most sound mediocre at the very best.
The Beolab 90 was placed closed to the frontwall. Sidewalls were also close but the sidewalls only extended a 1 m or so. Distance to rear wall was far.
I was able to hear them both in wide and narrow mode. Omni wasn't ready yet, but I've never cared much for omni coverage. No room correction was used.
In narrow mode they sounded great and took much of the room contribution out; giving great clarity, localization and pin-pointing. The bass was powerful and full. No lean presentation which is so typical of much hifi today.
In wide mode the imaging collapsed but gave a wider soundstage. But I also found them to sound fatiguing in this mode, probably caused by the high gain early reflections and a less constant polar. This might have been better if they stood out further in the room, delaying the reflections. However, the wide mode is too wide in my opinion. There's really no need for a 100-120 degrees dispersion, sending energy towards even the frontwall and corners.
I also have a pair of Geddes speakers, Abbey. I listened to the Abbeys right after I came home with the same tracks. My home theater room with the Abbeys is heavenly treated and uses multiple subwoofers. I noticed that the Beolab 90 had better openness and clarity compared to my Abbey setup. Other than that there wasn't much difference besides my setups having a more powerful deep bass presentation with the multiple subs (two bandbass' and one Tuba HT horn). But obviously comparing a non treated room with a treated room is unfair. I'm quite sure the Beolab 90 would have sounded better than my Abbeys in the same room. The polar of the Beolab 90 in narrow is constant over a much wider frequency area.
But what about Beolab 90 compared to a bigger horn setup? Do they sound as engaging? No. Do they have the same openness, resolution and clarity? No. Do they sound as coherent as speakers with a low cross over? No.
My reference here is Klipsch K402 by the way. With a beryllium diagraphm driver and low Xover they are in other league. Even with a frontfiring 15" below the horn with no CD.
It would be hard to compare Don Keele's CBT36 vs Beolab 90 in narrow mode because of the different coverage. But in wide mode, I'm certain the CBT36 (with subwoofer!) creams them. The CBT36 has a more uniform horizontal response, somewhat narrower beamwidth, and they are text book vertically while the Beolab 90 will have considerably lobing in the vertical plane.
What I would like to see and have thought about it for a long time is doing something similar with CBT. A way to change the beamwidth, for example between 80/90 degrees and 45 degrees but with the vertical benefits of CBT. This is possible but it will take a lot of drivers and amps!
To sum up I will say that while changing beamwidth of Beolab 90 is fun and a gimmick I'm not sure there's any point with the beamwidth in wide and omni. Wide mode is wider than what's really needed and causes too much acoustic problems. And omni never sounds good IMO in any small rooms. Either the wide mode should have been something like 70-90 degrees or they could have dropped it. And for the latter it's possible to do something similar much cheaper with another design.
The question then becomes; is there really any point to this? Besides being a cool gimmick that will sell on it's own my opinion is that it really isn't. However, it may be the window to the future where better an more appropriate beamwidth coverages/modes can be chosen.
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Now that the review is out of the way, here's a couple of interesting things I noticed about the Beolab 90:
1) I'm willing to bet B&O is losing money on the speaker. I work for a company that partners with B&O, and if you look at B&Os financial statements, a lot of their income and profits are coming from the headphones and the cheap stuff nowadays. My 'hunch' is that the Beolab 90 is a 'halo' item, where they lose money on it, just to show the world what they're capable of. Volkswagen does the same thing with the Bugatti Veyron; it sells for a million dollars and they've lost money on every single one of them. It's an engineering statement.
2) I'm a total basshead, I listen at deafening levels. One thing that really impressed me about the Gedlee Summas was that they were so clean and dynamic, you'd THINK you were listening at 90dB when you're listening at 100dB. The Summas are just *effortless.* When Geddes demo'd them at the RMAF I actually lost my voice from having to shout over the music. IE, it *seemed* like we were listening at a polite level, but the speakers were actually louder than it seemed. But due to very low power compression and distortion, you wouldn't know it. The Beolab 90s were very similar in this respect.
3) The Danley SH50s are noticeably directional. For instance, when I had them in my house if you walked around the speaker it was really noticeable how the intensity of sound was greatest in front of the speaker. It's a phenomenon that's really hard to describe unless you've heard it for yourself. Obviously most speakers are *brighter* on-axis, but the SH50s are noticeably LOUDER on axis. As you walk around the speaker it feels like someone is slowly cranking the volume know.
The Beolab 90s do this too; I walked behind the speakers and the lack of midrange and treble energy was very noticeable.
4) The bass on the Beolab 90s sounds like a dipole. Very 'dry.' Again, a lot like headphones. No boom whatsoever.
5) Obviously the most exciting part about the Beolab 90 is that it doesn't NEED to cost eighty thousand dollars. Just the driver cost alone is thousands of dollars, and eighteen channels of Icepower doesn't come cheap. It seems really obvious that the ideas embodied in the speaker will 'trickle down' to affordable speakers.
Thanks for the lengthy review Patrick/John
Basically like I expected, not a bad speaker at all. I agree that this seems like an all out: "let's show them what we can do with technology" project rather than making sane speakers for sane people.
I'm sure they will sell a few, as prestige often sells, though in a really small circle.
From your review I gather they do work. And that's interesting news for us DIY people. I'm still waiting for B&O to post more measurements like impulse, STEP. I have asked for them on the blog from "tonmeister" Geoff. He wasn't opposed to the idea but wasn't ready yet at that time.
I hope to see people inspired by this type of technology and see some spin offs created in DIY territory. Your idea of combining a Synergy with the bottom end inspired by the Beolab 90 makes sense. As soon as I saw that monster project my wheels started turning as well.
It is hard to see significant trickle down with low-tech engineering (if we can build it in a garage it is low-tech!). The speaker consists of a box, a bunch of standard drivers and a bunch of standard DSP, amplifier and power supply modules. In a technology sense it is hard to see anything that has not been in some soundbars for quite a while. Heat management perhaps?
B&O presumably suffered badly from the large reduction in the disposable income of the middle class and without much sign of it coming back they are presumably shifting the focus upwards and downwards in price. This looks like a product for the 1% with a nice effective marketing story but since it seems to be built from components that have already been developed I would expect the costs of the package to be modest without pushing and forcing the development of internal capabilities in any significant sense. I would agree it demonstrates internal capabilities.
B&O has been an admirable company in the field of home audio with a significantly greater emphasis on R&D and design than most. It has relied on a strong brand to support higher prices compared to hardware with equivalent technical performance. I doubt the brand will be as effective for the 1% because it is/has been a brand for the masses. At the low end cost is a strong factor and manufacturing in Denmark is going to rather limit how low they can go. I think they also manufacture in the Czech Republic? Elsewhere? If they get bought by a larger company with manufacturing facilities in developing countries it would allow the brand to expand at the low price end.
You can come fairly close to the "narrow" BeoLab 90 setting with only one driver and an acoustic resistance box in the 200-1khz range. With 3-4 drivers/dsp/amp channels you could probably do what they're doing in this range, but you need to ask yourself if it's worth the cost and complexity to achieve this. Just build a bigger horn
I've thought about building it just for the fun of it.......it might be interesting as well to build a small Synergy horn, and then use control drivers on the side and back of the cabinet to tighten up the pattern down low if you can't/won't have a 3-4' wide horn in your room. Amps and dacs are fairly cheap nowadays if you don't feel the need for "high end" stuff.
Patrick - did they demo the different directivity settings?
I'm still trying to figure out why the drivers are in a triangular array. My 'hunch' is this:
I think that you could control horizontal directivity by using drivers with a width equivalent to their frequency. A 1" tweeter for the octave at 13500hz, a 2" midrange for the octave at 6750hz, a 3" midrange for the octave at 4500hz, etc.
I think B&O may be doing this. But instead of using eight different diameters, they're using four. And they're using two in a row for some of the elements. IE, instead of using a 2" driver for 6750hz, they're using two 1" tweeters side by side.
By using this scheme, the speaker is naturally omnipolar. Then interference from the side drivers determines the beamwidth.
Here is a hint from the B&O blog:
"The basic problem when trying to do directivity control actively is that you need the loudspeaker drivers to be as close together as possible to have control of the beam width in their high-frequency band – but as far apart as possible to be able to control their low-frequency band. In the case of prototype 1, the drivers were simply too far apart to result in an acceptably constant directivity. (In other words, the beam width was different at different frequencies.) So, we had to try to get the drivers closer together."
I think that you could control horizontal directivity by using drivers with a width equivalent to their frequency. A 1" tweeter for the octave at 13500hz, a 2" midrange for the octave at 6750hz, a 3" midrange for the octave at 4500hz, etc.
I think B&O may be doing this. But instead of using eight different diameters, they're using four. And they're using two in a row for some of the elements. IE, instead of using a 2" driver for 6750hz, they're using two 1" tweeters side by side.
By using this scheme, the speaker is naturally omnipolar. Then interference from the side drivers determines the beamwidth.
Here is a hint from the B&O blog:
"The basic problem when trying to do directivity control actively is that you need the loudspeaker drivers to be as close together as possible to have control of the beam width in their high-frequency band – but as far apart as possible to be able to control their low-frequency band. In the case of prototype 1, the drivers were simply too far apart to result in an acceptably constant directivity. (In other words, the beam width was different at different frequencies.) So, we had to try to get the drivers closer together."
And also requires SMALL drivers, as do all arrays (or small, close, ports in the case of the Synergy). But a Synergy or Abbey based design with phased array bass could be just the ticket. And no need for ICE amps, even T-amps or IRS2092 amps can do great at LF and cost trivial bucks.
Just thinking out loud here, I think this is how it's working. My hypothesis in post 48 is probably wrong.
Here is the wavefront shape of a conventional loudspeaker. The sound radiates in 360 degrees - it radiates in a sphere. (Of course, it *doesn't* radiate in 360 degrees when the speaker is beaming. But we won't need to worry about beaming, because we'll use our drivers in a range in which they're NOT beaming.)
If we limit the radiation to ninety degrees we're putting way WAY more energy into one direction. A speaker like the Gedlee Abbey does this; you can see that the waveguide radiates sound into a ninety degree arc.
The interesting thing here is that you can get the same beamwidth if you use an array with the same shape. IE, instead of using a ninety degree waveguide that's eight inches deep, you can use a ninety degree array. And as illustrated above, the depth is very shallow. For instance, a ninety degree waveguide that's fifteen inches wide is 7.5" deep. Once you add in the compression driver, you're looking at a depth of about eleven inches. An array with a beamwidth of ninety degrees that's fifteen inches wide is just 3" deep!
One of the earlier prototypes of the Beolab 90 appears to use this idea. There's a five element array, and note that the elements are curved; they're creating a curved wavefront, just as a good waveguide would. According to the blog, "Although Prototype #2 sounded great in the sweet spot, it lacked the versatility of the first prototype. In other words, it was an amazing loudspeaker for a person with one chair and no friends – but it was not really a good loudspeaker for sharing… So, we started working on a third prototype that merged the two concepts – now called 'Beam Width Control' and 'Beam Direction Control'".
Unless I'm missing something, it seems like you could ditch a TON of the DSP complexity by simply using a fixed beamwidth. B&O themselves stated that the earlier prototype was "an amazing speaker." All that added complexity with the DSP is mostly there to change the wavefront shape. IE, they're delaying each driver to bend the wave from "wide" to "narrow." Personally, I want narrow, my goal is to make the room disappear. I don't care if I can use a wide beam to make the speaker sound good in the kitchen, that's not important to me. What IS important to me is the beamwidth control of a waveguide without a cabinet that's as deep as an SH50!
Here is the wavefront shape of a conventional loudspeaker. The sound radiates in 360 degrees - it radiates in a sphere. (Of course, it *doesn't* radiate in 360 degrees when the speaker is beaming. But we won't need to worry about beaming, because we'll use our drivers in a range in which they're NOT beaming.)
If we limit the radiation to ninety degrees we're putting way WAY more energy into one direction. A speaker like the Gedlee Abbey does this; you can see that the waveguide radiates sound into a ninety degree arc.
The interesting thing here is that you can get the same beamwidth if you use an array with the same shape. IE, instead of using a ninety degree waveguide that's eight inches deep, you can use a ninety degree array. And as illustrated above, the depth is very shallow. For instance, a ninety degree waveguide that's fifteen inches wide is 7.5" deep. Once you add in the compression driver, you're looking at a depth of about eleven inches. An array with a beamwidth of ninety degrees that's fifteen inches wide is just 3" deep!
One of the earlier prototypes of the Beolab 90 appears to use this idea. There's a five element array, and note that the elements are curved; they're creating a curved wavefront, just as a good waveguide would. According to the blog, "Although Prototype #2 sounded great in the sweet spot, it lacked the versatility of the first prototype. In other words, it was an amazing loudspeaker for a person with one chair and no friends – but it was not really a good loudspeaker for sharing… So, we started working on a third prototype that merged the two concepts – now called 'Beam Width Control' and 'Beam Direction Control'".
Unless I'm missing something, it seems like you could ditch a TON of the DSP complexity by simply using a fixed beamwidth. B&O themselves stated that the earlier prototype was "an amazing speaker." All that added complexity with the DSP is mostly there to change the wavefront shape. IE, they're delaying each driver to bend the wave from "wide" to "narrow." Personally, I want narrow, my goal is to make the room disappear. I don't care if I can use a wide beam to make the speaker sound good in the kitchen, that's not important to me. What IS important to me is the beamwidth control of a waveguide without a cabinet that's as deep as an SH50!
Well, with at least decent hardware (such as miniSharc) DSP complexity is just code and development time. For DIY no need to code for other than the intended placement and room. Until you move houses, but then you just develop new code. Unless you are making a public applicable design for, say, diyAudio, or somewhere like that.
The really tricky part in the B&O design is that they're using the side drivers to change the beamwidth of the front drivers.
For instance, in the earlier prototype, the midrange array was about fifteen inches in diameter and there were no side drivers. To me, this indicates that the midrange drivers were a conventional curved array. Similar to a CBT90, but in the horizontal axis not the vertical. Monte built one of these and posted it on his blog.
The production version of the Beolab 90 is a different beast; the array is smaller and there are drivers on the side. It's safe to assume that those drivers are playing out of phase, to change the beamwidth. This is similar to how a Dipole works, but without the SPL limitations.
The really skull crushing part is that they're using FIR filters, so they can vary the phase with frequency to get the optimal beamwidth. IE, at 1000hz the side drivers might be 180 degrees out of phase, but at 2000hz they might be ninety degrees out of phase. You would vary the phase difference until you got the correct polar response.
CRAZY.
For instance, in the earlier prototype, the midrange array was about fifteen inches in diameter and there were no side drivers. To me, this indicates that the midrange drivers were a conventional curved array. Similar to a CBT90, but in the horizontal axis not the vertical. Monte built one of these and posted it on his blog.
The production version of the Beolab 90 is a different beast; the array is smaller and there are drivers on the side. It's safe to assume that those drivers are playing out of phase, to change the beamwidth. This is similar to how a Dipole works, but without the SPL limitations.
The really skull crushing part is that they're using FIR filters, so they can vary the phase with frequency to get the optimal beamwidth. IE, at 1000hz the side drivers might be 180 degrees out of phase, but at 2000hz they might be ninety degrees out of phase. You would vary the phase difference until you got the correct polar response.
CRAZY.
The horizontal CBT-esque prototype made more sense to me when I saw it on Geoff Martin's blog. Plus it has precedents for use in vertical beamforming applications. Leads me to wonder if it was a deliberate concession to aesthetics.
Someone touched on Meyer and Aya earlier and what pro systems are accomplishing with phase control. Active cardoid control has nearly limitless possibilities with today's recursive filters. Wesayso touched on it with his full range arrays by measuring a single listening position to have smooth response and minimal phase and excellent vertical directivity......the only thing missing is horizontal. As DIYers, we can all accomplish this by various means as we have the luxury of designing a speaker for our individual listening rooms and cover all the bases. B&O has to cross the hurdle of making a speaker that sounds great in all listening rooms. I would guess that the audition of the WIDE preset would have had a much different outcome had the space been a small well treated one in the nearfield.
As far as the vertical offset of the mid high drivers, that serves to produce an irregularly shaped but always eminent lobe. Push the lobe a few degrees to the side and up or down and it's far less noticeable on axis.....so it further helps the system accomplish the disappearing act. CBT does it strictly in the vertical.......curve the array horizontally and you fix the entire problem. But that approach with arrays introduces complex construction problems and significant design complexities. Multiple channels of DSP and discreet amplification could conquer that beast for DIYers.
Patrick's statements ring true. If you could create controlled directivity without a horn or waveguide, why wouldn't you? Eliminate the eminent horn reflections and all of their complex phase interactions, reduce it to minimum with filtering and a few drive units eliminating the exponential collisions.
If some DIY maniac wanted to try something completely over the top using small arrayed full range drivers, a three sided floor to ceiling array with active cardoid control would be quite the accomplishment. I'm not sure the design couldn't be simplified even further with passive resistive loaded enclosure for proof of concept where the back wave of the fwd facing drivers was allowed to leak out of the sides.
The point is, B&O are on to something of solving the room problem using the DSP tools available. Meridian has been doing it on a simpler scale for a while now. Pretty smart!
As far as the vertical offset of the mid high drivers, that serves to produce an irregularly shaped but always eminent lobe. Push the lobe a few degrees to the side and up or down and it's far less noticeable on axis.....so it further helps the system accomplish the disappearing act. CBT does it strictly in the vertical.......curve the array horizontally and you fix the entire problem. But that approach with arrays introduces complex construction problems and significant design complexities. Multiple channels of DSP and discreet amplification could conquer that beast for DIYers.
Patrick's statements ring true. If you could create controlled directivity without a horn or waveguide, why wouldn't you? Eliminate the eminent horn reflections and all of their complex phase interactions, reduce it to minimum with filtering and a few drive units eliminating the exponential collisions.
If some DIY maniac wanted to try something completely over the top using small arrayed full range drivers, a three sided floor to ceiling array with active cardoid control would be quite the accomplishment. I'm not sure the design couldn't be simplified even further with passive resistive loaded enclosure for proof of concept where the back wave of the fwd facing drivers was allowed to leak out of the sides.
The point is, B&O are on to something of solving the room problem using the DSP tools available. Meridian has been doing it on a simpler scale for a while now. Pretty smart!
It's really a transformational technology. All serious pro sound reinforcement arrays are now active real time DSP controlled for even SPL at front of orchestra to same as top of mezzanine. Now moving to home and hifi.
It's like when aircraft fighters went from fly by cables and levers to fly-by-wire we never went back. The gains in performance of manueverability of an F16 vs old style F4 Phantom was unmistakable and industry could not go back. Now, all commercial aircraft are fly-by-wire. It adds the computer as a level of safety check in between with many other benefits.
Direct access multi-driver arrays via DSP will be more and more common. Given how small and cheap a 60 watt amp is now - there is no reason not to put an amp right on the magnet/basket of each driver. Then only a power bus has to be provided and small signal lines can be run to each driver rather than a massive rat's nest of 18 gauge wires.
Here is one of the new TPA3118D2 PBTL mono amps I just got - size of large postage stamp. 36mmx44mm 60watts mono. $9 ea.
It's like when aircraft fighters went from fly by cables and levers to fly-by-wire we never went back. The gains in performance of manueverability of an F16 vs old style F4 Phantom was unmistakable and industry could not go back. Now, all commercial aircraft are fly-by-wire. It adds the computer as a level of safety check in between with many other benefits.
Direct access multi-driver arrays via DSP will be more and more common. Given how small and cheap a 60 watt amp is now - there is no reason not to put an amp right on the magnet/basket of each driver. Then only a power bus has to be provided and small signal lines can be run to each driver rather than a massive rat's nest of 18 gauge wires.
Here is one of the new TPA3118D2 PBTL mono amps I just got - size of large postage stamp. 36mmx44mm 60watts mono. $9 ea.
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Well there is at least one reason that they might not like a strong magnetic field, but you knew that
I proposed that idea of a 3 sided array too, posted here: http://www.diyaudio.com/forums/full-range/274020-all-aspiring-full-range-array-project-26.html#post4477394
Seemed like a very cool idea after "getting" the concept of what B&O were doing
. Now I'm not complaining about my DSP/Array results, not at all actually , but it would be fun to be able to narrow the directivity to avoid having to treat the walls. I bet this 3 sided array would make a great speaker though.
I posted a comment on the designer's blog and he was kind enough to add me to the reviews: BeoLab 90 reviews earfluff and eyecandy
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