DIY New England - Saturday Oct 22

[dlr]

Posting here to avoid "thread drift" on the DXT tweeter thread, even though I got here from there.

Dave, IIRC you've always held that between driver felt was highly beneficial. Yet the dipoles you showed here appear to me to have just two pieces of felt in an "open V" shape around the tweeter.

Have measurements or listening in the last decade-and-change since your eye-opening diffraction article changed your position on optimal placement? Does the waveguide change something with the tweeter/midrange interaction?

Originally I had a small piece at the point of the V, it makes a measurable difference, but not a lot. The V shape seems to handle most of the diffraction, both the baffle edges and the midrange driver. I also just liked the looks of a simple truncated V shape and was looking for the least possible amount of felt. I had originally hoped that the DXT would obviate the need for felt other than between drivers, but was surprised that the edges required the usual treatment. The DXT waveguide loading just isn't sufficient to prevent baffle edge diffraction to the extent that I had hoped. I'm tempted to substitute another 1" dome to see how much difference there is. This was really only going to be a first try at a dipole system, I expected to go to a 4-way sooner, more like John K's approach. I still have plans for that and have a true dipole tweeter in mind.

The midrange itself doesn't have any appreciable diffraction insofar as the side edges go. But it did have an issue with the top edge diffraction, but that was related to the dipole characteristic. The midrange is operating almost fully in dipole mode in relation to the width, but the position of the driver below the tweeter on the rectangular baffle places the top edge too far away, so the dipole effect is in the transition range from dipole to monopole there. Raw baffle measurements showed a problem that I determined was the top edge. I experimented with felt and fixed it to some degree with felt at the top, but didn't like using that at all. I really wanted a more presentable system. So out of curiosity, I placed a thick piece of felt above the midrange on the rear of the baffle. This almost totally eliminated the bump measured on the front. This in essence cancelled out the additional depth of diffraction that is seen between monopole and dipole diffraction effects as seen from the front of the baffle. What this means is that the system is dipole primarily in the horizontal plane. Were it to be measured off-axis by rotating the system on the z-axis through 360 degrees, at some point the additional distance to baffle edges would slowly alter the response, lowering the frequency at which it is at the upper edge of dipole operation. But since this is not a coincident driver system, the change due to crossover integration off-axis will be far more detrimental than the small change in dipole range and that is all off-axis anyway, so I went for absolute best on-axis response that I could get with the geometry. Dipole, monopole, both are related to the distance to any point on a baffle edge, so the monopole diffraction changes as does the dipole interaction. My take from this is that for the absolute best, most complete dipole system, multiple drivers mounted on circular baffles is best (for round drivers anyway). Usually a dipole designer tries for a narrow baffle, but pays little attention to the vertical dimension. I suppose that the primary difference is not at the listening position direct response, it's in the total room radiation difference between monopole and dipole. Full dipole reduces the total energy vs. monopole by, what, 4.6db? I forget the exact number. To me this means that the vertical radiation (floor and ceiling portion) will be reduced with a full dipole, but that's only a portion of the dipole effect, so how much it may be perceived is anyone's guess. But I digress (a lot!).

At DIY NE I kept waiting for someone to ask about the big piece of felt (2" h, 6" w, 1" d) on the back, but apparently no one noticed it since it's not obvious. I also found that after installing the tweeter with the big motor sticking out in the back that the felt had much less effect, the tweeter already blocking a lot of the back wave from reaching the top edge directly. The impact of that really surprised me.

dlr

[Pallas]

DIY NE 2016 Pictures

dlr

Posting here to avoid "thread drift" on the DXT tweeter thread, even though I got here from there.

Dave, IIRC you've always held that between driver felt was highly beneficial. Yet the dipoles you showed here appear to me to have just two pieces of felt in an "open V" shape around the tweeter.

Have measurements or listening in the last decade-and-change since your eye-opening diffraction article changed your position on optimal placement? Does the waveguide change something with the tweeter/midrange interaction?

[jclin4]

Hi Dave, thanks for publishing the webpage and for your pics and comments on the builds. I much enjoyed being there. I shared the link with my wife to give her a peek into these gatherings. She liked the last pic of the three rescue dogs!

[dlr]

Thanks for putting up the pictures. I think Jon's speakers were using the 4 ohm Anarchy woofer. Build thread: http://techtalk.parts-express.com/fo...-rs100p-8-sb19

Thanks for the info. I've updated the page and included a link to his PE build thread.

dlr

[johnnyrichards]

DIY speakers and dogs? Awesome - reminds me of DDIY 2013, the so-called informal debut event. Looks like a lot of fun!

[Michael P]

Thanks for putting up the pictures. I think Jon's speakers were using the 4 ohm Anarchy woofer. Build thread: http://techtalk.parts-express.com/fo...-rs100p-8-sb19

[dlr]

Hi Dave,

I looked up your pictures and descriptions in http://diyne.speakerdesign.net/diy20...2016_pics.html

It is impressive what you have managed to accomplish with UE5 and good, reliable Delta410 soundcard.
I am glad you enjoy the outcome and so the other listeners.

Best Regards,
Bohdan

Once I got past the hurdle of the old XP PC board causing the sound card issue, it's been quite a difference.

The Delta 410 Win7 driver has some problems, so I would recommend anyone else to go for any of the newer options. Of course the 410 is obsolete, but they're probably easy to find on ebay. The most recent puzzling problem came about after I created a new, non-admin account to use. The card came up as only being capable of 48K. Nothing would change that, even reinstalling the driver. The odd thing is that with a 44.1K input, it would show sync, but at 48K. The admin account started showing the same thing.

Eventually I tried the UE at 44.1k setting in the preferences anyway and it performed successfully, despite the driver dashboard saying it was locked at 48K. So it is still working, but the driver (last Vista 6.0.8) is quirky. Sine it works, so I'll continue to use the 410. I had plans for a 4-way plus sub, so the Delta 1010 that I have will eventually be in use.

dlr

[bohdan]

Hi Dave,

I looked up your pictures and descriptions in http://diyne.speakerdesign.net/diy20...2016_pics.html

It is impressive what you have managed to accomplish with UE5 and good, reliable Delta410 soundcard.
I am glad you enjoy the outcome and so the other listeners.

Best Regards,
Bohdan

[dlr]

I've added a page with pictures and some descriptions of the systems at DIY NE this year. I've included the comments of jclin4 and Michael P. from this thread in the page, so those are verbatim copies of what they said here.

DIY NE 2016 Pictures

dlr

[DearSX]

I am sorry I missed this event, I've been wanting to go for a while. Just had too much going on in my life. Hopefully next time.

[kenny_k]

Well......it is speaker porn.

[dlr]

This is like playboy mag without pictures.
Pictures please!

I have photos (none that would ever show up in Playboy!) and will put up a page soon. But yeah, pictures are worth 1000 words.

dlr

[r-carpenter]

This is like playboy mag without pictures.
Pictures please!

[Michael P]

I liked your speakers a lot, they were solid all around (and I appreciate the cabinet design and finish... creative, but not *too* creative). The damped open back let the midrange "spread out" a bit, and we were able to position the speakers wide apart to get a big soundstage without it collapsing to the left/right. Pretty impressive considering there weren't any costly components in there. These, among a few other designs I've seen recently, have enlightened me about the virtues of small 3-ways (as long as you are brave enough to tackle the mid/woofer crossover). Now you just need to try an active crossover.

As far as Dave's speakers, they were quite an experience to listen to; all of the permutations were technically excellent, and we were able to make comparisons that explored the realm of perception and differing tastes. I was of two minds about the first TM module. I like the focus of the DXT tweeter, and it played clean and loud (preserving the bite on electric guitars, without bothering your ears). The sound from the dipole 15W[?] midrange was incredibly clean and spacious (another word that came to mind is "liquid"). In fact, Dave mentioned that he had matched the polar response of the tweeter to the front half of the polar response of the mid. So they were perfectly integrated tonally, but I felt a bit of a spatial disconnect between the monopole treble and dipole mid. I found the second module (12M/OW1) with monopole mids to be more comforting even though they were not as outwardly impressive. I preferred the LR8 version to the LR2 version, which sounded a bit subdued (or maybe compressed) in the midrange by comparison. And the third module (with the Kevlar mid) was interesting too. The highs didn't have the "Technicolor" detail of the OW1 and voices were very similar tonally, but perhaps slightly less clean. It was really interesting to listen to the (mostly subtle, sometimes mildly obvious) variations between speakers that all had quality drivers and a ruler flat frequency response.

I remember thinking the bass section (H-frame) was pretty strong, but that this is the way most larger speakers sounded in that room. It was a nice quality bass, much more even than what I can get in my room. (I guess in my room I have about the same broad balance, but all of the bass is around 40 Hz, so the upper bass is leaner.) We got those woofers moving (with, what was it, Pink Floyd?).

I liked the tone of Mike A's speakers, they sounded plain and neutral. He was just getting started on the crossover but I thought it was an improvement from the last time I listened at his place. It was also a big help to use the digital input and avoid going through an extra ADC. However, the bass made me scratch my head a bit, wondering if there was a phase issue. All the other speakers sounded richer to me, and I'm not sure why--maybe part of this was the quality of the DAC and amplifiers. We'll keep working on them, and post some more information about the Raspberry Pi crossover setup and build photos in the near future ... I guess he has to decide what they should be called first! (The midrange is a Scanspeak 10F/8414.)

[jclin4]

Yes agreed, many thanks to Dave for opening up his place for this gathering. It was small this time, but this allowed for more listening to each system and also more discussion about them. I always learn something new when attending DIY events, but even more so at this event, given the intimate gathering and setting.

As Mike P mentioned, active systems were center of the day, as were three-ways. I was the throw back, bringing my horizontal monitors with passive XOs.

Mike A and Mike P brought a stand-mount 3-way with Hiq OW1 tweeter, small format mid (make which I did not capture), and SEAS ER18RNX woofers. A nice complement of drivers, and well put together in reasonably sized cabs. But the star of this setup is the active crossover implemented in python script and associated python and C libraries running on a raspberry pi 3. This was software they created on their own and not an off the shelf software package. Mike A was able to make adjustments to the crossover by changing parameters in his code on his macbook (I think the Rpi and Mac were using his phone as a wifi access point). The system, which is a work in progress, also included a Sure 6-channel amp board and USB sound card (not specifically designed for raspberry pi, but on a circuit board similar in size). As a WIP, it's probably not fair to evaluate for SQ, but what I heard sounded good and offers great promise, particularly as they refine the software and iterate on improving and optimizing components, like the power supply.

As mentioned, Dave demonstrated an interchangeable active system that was actually 3-systems-in-1. The base (or bass) of it all are dipole, H-frame woofers (15" I think?), two per side. The first tweeter+mid module on top were dipole mids (Revelator) + SEAS DXT tweeter. This combination sounded fantastic. Very open and dynamic, with great detail.

Next module had a smaller mid (Scanspeak, I think, about 3-4") in monopole configuration with Hiq OW1 tweeter. This sounded very different than the dipole module. The upper XO was LR2 and for kicks, Dave changed this to LR8 on his PC running Ultimate Equalizer software (try doing LR8 with a passive XO!), and we listened some more. Immediately the midrange became clearer and more well defined. Pretty much all there heard this.

Last module had Scanspeak tweeter (9300 or 9500) and a 4-5" fiberglass mid (apologies for not getting the exact driver models...these are in a higher-end space I generally do not play in), like the second module also in a sealed box. These sounded very neutral and balanced and I would be very happy listening to this configuration over the long-term, but then we then ended by putting the dipole module back in just to get one more listen. These were magic!