This is not true. What I said above does work in practice. It's very similar to increasing the depth of the wings on a H frame dipole. Try it, I did.
OK. Just to be clear, were the drivers operating in-phase, and was the enclosed volume small?
They were operating as a dipole, not a bipole. Enclosure volume is largely irrelevant in this case, the air just moves back and fourth adding a little moving mass to the two drivers and lowering the resonant frequency and raising Qt slightly.
But that's the point - you'd get the same effect by adding a few grams to a single driver's cone.
That would lower fs, as you say, and raise Qts, at the expense of sensitivity. The change would depend on the amount of air in the enclosed volume.
I don't see any positives in adding the extra driver in this way.
Thanks Bushmeister!
I had some speakers that looks very much like yours, there are some pictures at the end of this thread The Totem of Tone, an active 3-way dipole and active subwoofer (A very interesting thread BTW) I dismantled them because I could not get these fit nicely in our living room, with the kids running around etc. I do have a mancave (our cellar), but that is long and narrow, so I have only a mono channel there, which currently is a line array as well (post 3227 in the big thread https://www.diyaudio.com/forums/multi-way/123512-ultimate-baffle-gallery-162.html#post6449620)
My idea was to build dipole line arrays in our living room using the 3" FR from SB, I ordered 68 of them. I made one array, than the GRS slim drivers came out. That one array went to the cellar, and 28 slims were bought (some spares). My wife and I decided on these "room dividers" + speakers and I think their positioning could not be better in the room, they have all the space to breath. We like their "invisible" look and they were really easy to mount. The parts for the shelves were cut by the local DIY wood shop (I have no woodworking tools), I just screwed them together. Only two holes in the ceiling for attaching the multiplex plate from which the drivers are hung. Made some jigs to space the drivers evenly along the wires (that suspend the drivers, and do feed them the music). Some 3D printed parts made life much easier as well 🙂 I have checked your synergies and other builds, and always thought: that is a lot of work, no way I can do that. I can't really think about something that would be better. Well, maybe replacing the woofers with some other 10" (as the scan speak discovery 26W) or maybe adding a subwoofer for the low bass, but no sealed unit to not disturb the neighbors. So, quite happy overall!
I still have all the parts for the dipole based on the NEO10 and Mundorf AMT and the SB woofers. I also created my frankenstein project, pictures here https://www.diyaudio.com/forums/multi-way/123512-ultimate-baffle-gallery-164.html#post6493752 (post 3279). The idea is to put the speakerrs away in a compact fashion (and indeed, one can mount the woofers on top of each other, or in front of each other) So maybe one day I will remake the NEO10 and Mundorf AMT dipoles, hanging them in this frame, and compare to the line arrays. I have amplifiers and a 8 channel DSP, so I could do it, but currently working on DIY amplifiers for the line arrays: I like tubes, and the increased sensitivity (due to multiple units) and possibility for higher loads (connecting all speakers in series) opens a lot of opportunities to try unconventional tube amplifiers 🙂
regarding the GRS. I have the slims, the same as shown in xrk971. I think these are rather unique drivers (there is no similar B&G). Similar line arrays were built by members here, one using Radian planar drivers (as wide as the NEO8), other using the actual NEO8. Both projects were done before the slims came out, and in both projects the creators played with additional tweeters (the Dayton PTMini 6) and IIRC eventually took them out. And the slims do, I think, highs better and theoretically with a better dipole pattern. And they are much cheaper!
Member OllBoll also bought a lot of the slims and measured them all, observing a very good consistency. Another advantage.
I had some speakers that looks very much like yours, there are some pictures at the end of this thread The Totem of Tone, an active 3-way dipole and active subwoofer (A very interesting thread BTW) I dismantled them because I could not get these fit nicely in our living room, with the kids running around etc. I do have a mancave (our cellar), but that is long and narrow, so I have only a mono channel there, which currently is a line array as well (post 3227 in the big thread https://www.diyaudio.com/forums/multi-way/123512-ultimate-baffle-gallery-162.html#post6449620)
My idea was to build dipole line arrays in our living room using the 3" FR from SB, I ordered 68 of them. I made one array, than the GRS slim drivers came out. That one array went to the cellar, and 28 slims were bought (some spares). My wife and I decided on these "room dividers" + speakers and I think their positioning could not be better in the room, they have all the space to breath. We like their "invisible" look and they were really easy to mount. The parts for the shelves were cut by the local DIY wood shop (I have no woodworking tools), I just screwed them together. Only two holes in the ceiling for attaching the multiplex plate from which the drivers are hung. Made some jigs to space the drivers evenly along the wires (that suspend the drivers, and do feed them the music). Some 3D printed parts made life much easier as well 🙂 I have checked your synergies and other builds, and always thought: that is a lot of work, no way I can do that. I can't really think about something that would be better. Well, maybe replacing the woofers with some other 10" (as the scan speak discovery 26W) or maybe adding a subwoofer for the low bass, but no sealed unit to not disturb the neighbors. So, quite happy overall!
I still have all the parts for the dipole based on the NEO10 and Mundorf AMT and the SB woofers. I also created my frankenstein project, pictures here https://www.diyaudio.com/forums/multi-way/123512-ultimate-baffle-gallery-164.html#post6493752 (post 3279). The idea is to put the speakerrs away in a compact fashion (and indeed, one can mount the woofers on top of each other, or in front of each other) So maybe one day I will remake the NEO10 and Mundorf AMT dipoles, hanging them in this frame, and compare to the line arrays. I have amplifiers and a 8 channel DSP, so I could do it, but currently working on DIY amplifiers for the line arrays: I like tubes, and the increased sensitivity (due to multiple units) and possibility for higher loads (connecting all speakers in series) opens a lot of opportunities to try unconventional tube amplifiers 🙂
regarding the GRS. I have the slims, the same as shown in xrk971. I think these are rather unique drivers (there is no similar B&G). Similar line arrays were built by members here, one using Radian planar drivers (as wide as the NEO8), other using the actual NEO8. Both projects were done before the slims came out, and in both projects the creators played with additional tweeters (the Dayton PTMini 6) and IIRC eventually took them out. And the slims do, I think, highs better and theoretically with a better dipole pattern. And they are much cheaper!
Member OllBoll also bought a lot of the slims and measured them all, observing a very good consistency. Another advantage.
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There is no question the H frame is a more cost effective approach. I am suspicious about the nude clamshell arrangement and its supposed 3dB efficiency gain. I may have to do some experiments myself.
Wow Erik! What a lot of impressive builds! You are clearly almost as mad as me!!!
Don't you just love this journey!?
I'm wondering if this works by simulating an H-baffle with similar dimensions - so efficiency gains are mostly down to reducing the frequency of the dipole peak?
In which case, the separation of the two drivers might make a difference?
In which case, the separation of the two drivers might make a difference?
in my own prototyping thread, i recently wrote that a high pass filter (DSP) is a must to protect woofers on OB (i would even say IB and very big boxes too)...
Variations on a new OB project
to my surprise, there were quite a few sceptics.
in your case, a steep filter at 35-40hz (depending on your usual listening level) would have been enough and you could be enjoying amazing OB bass even with ultralow bass notes filtered out.
very high excursion drivers are also an option but they are typically low sensitivity. and i am positive that your AE drivers would beat them in bass quality (resolution drops as cone moves too much).
now the bad news: i bet your woofer is blown.
have it repaired, apply steep high pass.... and enjoy 🙂
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Would this be why Erik only saw the 3 dB increase?
"Now I am curious why I only got about 3dB increase with the compound dipole. I used 1 amplifier to feed either one or both drivers (they are 16 ohm, so no problem for the amp driving 2 in parallel), you used 1 amplifier per driver, but the effective power (and therefore displacement) of each speaker is the same in both cases."
He used the same amp, so there was no doubling of power, whilst because each of my drivers have their own amp, I saw 6 dB increase??
This would make much more sense to me, and make our data congruous.
I think not, as in my case the amplifier delivered twice the power (theoretically same output voltage, half the impedance). It is a good class AB amplifier, so I assume it is a good voltage source.
I have just realised - you probably don't have the set up still made up looking at all your project since!??
Ah well - hopefully others might try this too. I may try to get more measurements tonight.
Ah well - hopefully others might try this too. I may try to get more measurements tonight.
@zymrna
Yes, I am absolutely in agreement that a highpass filter should be used in these OB and Baffle-less designs.
Unfortunately, as I said, I learned the hard way.
I think we all sort of hope that the worst hasn’t happened (blown driver)...but more than likely I will end up shipping it back to AE for a rebuild.
When I did a resistance test on the voice coils things appeared normal compared to the other drivers.
I need to disassemble all the drivers and want to test them beyond just a voice coil resistance test to make sure its only an issue with one driver.
Perhaps using REW to generate frequency sweeps across their range.
I managed to get all (4) drivers used for about the price if (1)...so I’m not completely devastated about having to spend a couple hundred dollars to fix one.
It’s hard to be patient and not jump on another driver option, but I agree that these drivers are worth the effort.
Yes, I am absolutely in agreement that a highpass filter should be used in these OB and Baffle-less designs.
Unfortunately, as I said, I learned the hard way.
I think we all sort of hope that the worst hasn’t happened (blown driver)...but more than likely I will end up shipping it back to AE for a rebuild.
When I did a resistance test on the voice coils things appeared normal compared to the other drivers.
I need to disassemble all the drivers and want to test them beyond just a voice coil resistance test to make sure its only an issue with one driver.
Perhaps using REW to generate frequency sweeps across their range.
I managed to get all (4) drivers used for about the price if (1)...so I’m not completely devastated about having to spend a couple hundred dollars to fix one.
It’s hard to be patient and not jump on another driver option, but I agree that these drivers are worth the effort.
Here are a couple photos taken in better lighting so you can see the construction in more detail.
I decided to go with a 'stone effect' granite finish on the baffle to keep with the industrial feel of them - I didn't feel trying to soften them would work given how they are designed.
The baffle is 22mm BB plywood sheeting with hardwood - oak baton braces.
I was going to CLD them with two ply layers and a CLD layer between - something I have done a fair bit in previous builds - but due to the decoupling of the drivers I didn't feel it was required. There is no movement or vibrations at all even at very high SPLs.
I am using pro- 8 pole and 4 pole neutrik speakon connectors - two per speaker, as the subs have two amps - one each, and then there are three amps for the woofer, mid and tweeter.
Neutrik NL8MPR Male Silver Nickel 8 Pole Speakon Chassis Panel Mount.
These really help with active designs where lots of connections are needed and are really solid. You can see the sub connection in one photo - the woofer/mid/tweeter connector is beside it.
As you can see from the side profile, I have suspended the woofer - the deltalite 2515 at about a 5 degree tilt - this is because it is below the listening axis and helps with the polars a little.
Also I have both the speakers on decent quality 1" castors - these are life changing for me - I can literally roll them about the room with one finger - something I feel is essential for open baffle speakers if you don't want them sitting in the middle of the room all the time. If any of you have open baffle speakers and you are constantly lifting them back and forth - try some castors 😀 Keeps my wife happy as I can push them right back against the wall when not listening.
Thanks to the advice here, I have put a 30Hz high pass filter on the subs - 48dB and this really seems to keep excursion down when switched on (the subs FS is 29 Hz).
I have discovered the dipole bass needs very little room EQ compared to my monopole - literally only one slight peak at 47Hz needs to be addressed with a -5 dB peak filter - much less than the push-push sealed subs - so it is true that dipole bass have very different room interactions.
I was going to make lots of measurements last night, but after dialling in the bass a little, I'm afraid I got distracted listening to all my usual fave tunes 😱
I promise I will get some more done soon!
I decided to go with a 'stone effect' granite finish on the baffle to keep with the industrial feel of them - I didn't feel trying to soften them would work given how they are designed.
The baffle is 22mm BB plywood sheeting with hardwood - oak baton braces.
I was going to CLD them with two ply layers and a CLD layer between - something I have done a fair bit in previous builds - but due to the decoupling of the drivers I didn't feel it was required. There is no movement or vibrations at all even at very high SPLs.
I am using pro- 8 pole and 4 pole neutrik speakon connectors - two per speaker, as the subs have two amps - one each, and then there are three amps for the woofer, mid and tweeter.
Neutrik NL8MPR Male Silver Nickel 8 Pole Speakon Chassis Panel Mount.
These really help with active designs where lots of connections are needed and are really solid. You can see the sub connection in one photo - the woofer/mid/tweeter connector is beside it.
As you can see from the side profile, I have suspended the woofer - the deltalite 2515 at about a 5 degree tilt - this is because it is below the listening axis and helps with the polars a little.
Also I have both the speakers on decent quality 1" castors - these are life changing for me - I can literally roll them about the room with one finger - something I feel is essential for open baffle speakers if you don't want them sitting in the middle of the room all the time. If any of you have open baffle speakers and you are constantly lifting them back and forth - try some castors 😀 Keeps my wife happy as I can push them right back against the wall when not listening.
Thanks to the advice here, I have put a 30Hz high pass filter on the subs - 48dB and this really seems to keep excursion down when switched on (the subs FS is 29 Hz).
I have discovered the dipole bass needs very little room EQ compared to my monopole - literally only one slight peak at 47Hz needs to be addressed with a -5 dB peak filter - much less than the push-push sealed subs - so it is true that dipole bass have very different room interactions.
I was going to make lots of measurements last night, but after dialling in the bass a little, I'm afraid I got distracted listening to all my usual fave tunes 😱
I promise I will get some more done soon!
![IMG20210630181300[1].jpg](/community/data/attachments/866/866939-7499df58909e851959ea2cd5626bd125.jpg?hash=dJnfWJCehR)
![IMG20210630181333[1].jpg](/community/data/attachments/866/866949-150a1e1c388b69411d4cedf44fef0ca5.jpg?hash=FQoeHDiLaU)