Something New Cooking...............................

[dlneubec]

That would certainly present a problem for castable silicon. They would have to stick very well to the plastic to be of value.

[JonP]

Yep, Paul's got a point, don't bother. More of that dim memory of my Dad using that stuff comes back... He used a spray release for the epoxy casting, but almost didnt need to.

Stuff wouls be better suited to making molds of waveguides, then casting them in plaster... Hmmmm....

Not sure if you meant soft putty, or that hardening water putty stuff. Not sure if the latter has some potential, might if it could dry/harden well in the enclosed space... and stick well.

[dlneubec]

Yep, Paul's got a point, don't bother. More of that dim memory of my Dad using that stuff comes back... He used a spray release for the epoxy casting, but almost didnt need to.

Stuff wouls be better suited to making molds of waveguides, then casting them in plaster... Hmmmm....

Not sure if you meant soft putty, or that hardening water putty stuff. Not sure if the latter has some potential, might if it could dry/harden well in the enclosed space... and stick well.

I was thinking the soft stuff. It seems to stick well to hard surfaces and maintains its soft, dense form for years. I'm thinking your better off with something that is very dense, stays soft and can completely absorb vibrations. Could be wrong, of course, but at a $5 for 5lbs at Menards, it is a cheap option to test.

[dlneubec]

I’ve been doing a little more on this design this weekend. First up, I tried out using plumbers putty for a dampening agent for the plastic waveguides. It is a sticky, soft, pliable clay-like material that is supposed to stay pliable for years. I applied nearly about 4 pounds of the 5 pound bucket to the two diffusers. I coated the inside of the diffusers with putty with between about 1/4” and 1/2” of putty over most of the surface. I have no measurement data, but it seems to do a great job of deadening the plastic so there is no ringing when rapped with a metal wrench and there is a significant lowering of the resonant frequency.

Below is a picture of the inside of the bottom diffuser partially lined with the putty. I applied an equal amount to the top diffuser.



The waveguide at the top will have a second waveguide set over top of it. In the photo below, you can see the recessed lip for the second waveguide. They are on backorder at PE until December 11th. In the interim, I applied some plumbers putty to this waveguide as well, though I’m not sure if this solution will work as a sandwich between the two parallel waveguides.



I also did some additional crossover tweaking and as part of that effort, I wanted to see if I could find a way to lift up the drooping top end. This first graph is a farfield of the previous crossover that illustrates the drooping top end.



The diffuser inside of the waveguide comes to a sharp point. It turns out, that if I place a little ¼” disc and place it over the sharp tip, I believe it acts like a phase shield and the result is a lifting of the top end. The graph below shows the improved top end. I think this can be further improved upon with more testing. I’ve also merged in a nearfield on the woofer and the port response here.



Finally, I did some impedance measurements of the flexport to determine exactly the ranges of tuning available from port adjustments. This does not include the sealed tuning setting, since I had the cable that runs from the woofer to the XO going through the port, so it was not possible. The FB range available is from approximately 29hz to 39hz. These were taken in about 1" increments of length change.

[cjd]

You could always try a 1/2" dome to try to fill out that very top end... if it doesn't hurt impedance too much.

Looks excellent.

[dlneubec]

Chris,

Agreed, that would be an option.

It doesn't sound lacking at the top end in this latest rendition, at least to my ear, so it may not need anything further. The challenge I enjoy is staying both a 2-way and truely omni, at least in the horizontal direction.

A 12" 2-way with a 1" dome tweeter is pretty uncommon. :E

[cjd]

Agree on the fun, and the less significant impact of the droop. I assumed a filler tweet would fire up and still be omni, but not 2 way any more.

I'm not surprised about the point, though I suspect its more about throat reflections than the point. A 1/2" tall felt slug instead of the point might work wonders. Or not. I was able to clean up throat issues with the neo in a waveguide along these lines.

[dlneubec]

I did try a felt disk first. Not so good despite my similar intuition. It killed the high end which rolled off at about 4th order, IIRC, starting around 8-9khz!

I think it is acting more like a phase sheild that you often see on hard domes, but know way to know. I will try more materials and perhaps different shapes and sizes. The results presented uses a flat piece of rubber gasket, about 1/16" thick and 1/4" in diamter. I bet adjusting the distance from the dome to the disk will also make a substantial difference.

[Paul W]

Maybe counter-intuitive, but you might try a blunt diffuser that never goes below about 1/2" in diameter...or KEF style vanes.

[JonMarsh]

Some nice looking curves there, Dan! Have you tried doing any distortion sweeps?

I'm jealous of all the progress you guys have been making- while I've been working on the weekends getting ready for this trip (writing this from SFO airport, departing this afternoon to Frankfurt). But after I get back on the 14th, I'll have three weeks off to catch up! Also have some questions about your Echelons, but that will have to wait till later.... Now, I just got an email from PE for their new catalog, and I could swear they're on the front cover! Have you seen that? :W

[dlneubec]

Hi Jon,

My wish for you is that you can retire soon and spend all your time geeking out on speakers, tools, audio equipment, music and whatever else you currently don't have time for.

Wow, how did those get on the PE cover? (thanks for the setup)

Actually, they sent me a complimentary catalog about 2 weeks before the started shipping them. There is some photo magic going on there, because the speakers were picked up and taken to PE in Springfield/Dayton Ohio. I don't think there are any oceans in Dayton. :B

I have not done any distortion sweeps. Of course, these are very low distortion drivers to begin with, as you know and then equalizing the boost the waveguide/horn provides to the tweeter should reduce the tweeter distortion even more on the low end. However, I don't know how much distortion a horn configuration like this might impart in and of itself. Intuitively you would think there has to be some extra reflections going on, though it sounds very coherent.

I'm really anxious to hear a pair in room, but that's still probably a couple months off. It's interesting and possibly beneficial to do intial voicing with a single speaker because it takes the stereo/imaging/soundstage element out of the mix and you can concetrate on balance. I have found some tweaking is still necessary after you hear a pair and you can't really get a feel for the full character of a speaker until you hear them in stereo and can bring those other elements to the table for evaluation.

[Hank]

I just saw your speakers on my new PE catalog cover - congratulations! And yes, my first thought was: Photoshop. Anyway, your work deserves to be on the cover. Good call on the disk - curve looking very good now.
Retirement for Jon is an option, but if he gets a promotion, I'm afraid he'll stick around work another few years. Maybe I should find him a job here in Austin. Apple is building a big facility here...

[Hdale85]

Weren't the Hoss's on a cover at one point as well?

[dlneubec]

Thanks, Hank. The folks at PE are some of the most supportive people I've met in this hobby, so for me, it's a real honor for a creation of mine to be on their catalog cover.

Hdale, yes my HOSS design was on the cover for 2009, IIRC.

[Squidspeak]

I’ve been doing a little more on this design this weekend. First up, I tried out using plumbers putty for a dampening agent for the plastic waveguides. It is a sticky, soft, pliable clay-like material that is supposed to stay pliable for years. I applied nearly about 4 pounds of the 5 pound bucket to the two diffusers. I coated the inside of the diffusers with putty with between about 1/4” and 1/2” of putty over most of the surface. I have no measurement data, but it seems to do a great job of deadening the plastic so there is no ringing when rapped with a metal wrench and there is a significant lowering of the resonant frequency.

Below is a picture of the inside of the bottom diffuser partially lined with the putty. I applied an equal amount to the top diffuser.



The waveguide at the top will have a second waveguide set over top of it. In the photo below, you can see the recessed lip for the second waveguide. They are on backorder at PE until December 11th. In the interim, I applied some plumbers putty to this waveguide as well, though I’m not sure if this solution will work as a sandwich between the two parallel waveguides.



I also did some additional crossover tweaking and as part of that effort, I wanted to see if I could find a way to lift up the drooping top end. This first graph is a farfield of the previous crossover that illustrates the drooping top end.



The diffuser inside of the waveguide comes to a sharp point. It turns out, that if I place a little ¼” disc and place it over the sharp tip, I believe it acts like a phase shield and the result is a lifting of the top end. The graph below shows the improved top end. I think this can be further improved upon with more testing. I’ve also merged in a nearfield on the woofer and the port response here.



Finally, I did some impedance measurements of the flexport to determine exactly the ranges of tuning available from port adjustments. This does not include the sealed tuning setting, since I had the cable that runs from the woofer to the XO going through the port, so it was not possible. The FB range available is from approximately 29hz to 39hz. These were taken in about 1" increments of length change.

Dan,

Being a cabinet maker for a good part of my life, I've taken a few kitchens apart some old some not so old. Point being, plumbers putty usually dries up and crumbles/cracks after a few years so long term maybe not the best material for your purpose. Squid

[dlneubec]

Thanks for the heads up Squid!

Actually, that may be ok with me. As an active designer, I typically don't use speakers more than a year or two (the Echelon's may be the exception to that) and often repurpose drivers, XO parts, etc. At $5 a speaker and an easy installation, it would probably not be that big a deal to replace after a few years, if needed. I can also pretty much seal it up inside the diffusers, if I want and that may extend its life some, kind of like it is still in the tub.

Of course, if I eventually get these turned in wood, I won't have to worry about it.

[Squidspeak]

Thanks for the heads up Squid!

Actually, that may be ok with me. As an active designer, I typically don't use speakers more than a year or two (the Echelon's may be the exception to that) and often repurpose drivers, XO parts, etc. At $5 a speaker and an easy installation, it would probably not be that big a deal to replace after a few years, if needed. I can also pretty much seal it up inside the diffusers, if I want and that may extend its life some, kind of like it is still in the tub.

Of course, if I eventually get these turned in wood, I won't have to worry about it.

Dan, if you could find a way to seal it off from the air around it that would be great. I just had visions of chunks falling into the
diffusers as it got older and dried out. There maybe another product with
similar properties that doesn't dry out but dont know of one .

[dlneubec]

Well, I can seal off the mdf with the finish to some degree. The waveguides are bolted to the mdf and I can use weather stripping to seal that interface. Perhaps that will be enough.

[JonMarsh]

I just saw your speakers on my new PE catalog cover - congratulations! And yes, my first thought was: Photoshop. Anyway, your work deserves to be on the cover. Good call on the disk - curve looking very good now.


Retirement for Jon is an option, but if he gets a promotion, I'm afraid he'll stick around work another few years. Maybe I should find him a job here in Austin. Apple is building a big facility here...

Ruh Roh.... sitting in my hotel room in Vienna, tomorrow flying to Klagenfurt to spend time in Villach next week (our main facility for power electronics in Austria, and our main wafer fab, too), and I get a call from my boss...

How's that saying go? Four more years? Or more? Surprising me, anyway, he has verbal confirmation from HQ that the promotion is going through. :B

So, I really appreciate Dan's wishes for me to be able to get to this fun stuff full time, but it looks like for me to catch up with Dan's productivity is a lost cause! :roll: At least not for a few more years... :roll:

So threads like this one will help me deal with the intermittent and vicarious nature of my DIY efforts!

Besides, if I had too much free time, I'd probably try to build this other DIY idea I have that I think would be complementary to my current project- for now, I settle for plugging research data and concept drawings and vendor info into my new favorite tool, Evernote, and imagine what it would be like with some actual spare time!

But coming up will be three weeks off.... for me that will be Xmas Speaker Camp- and sorry for the thread jack- just had to share!

[dlneubec]

Congrats on the promotion, Jon!

Xmas speaker camp sounds like fun. Hears hoping for good weather so that doesn't hold you back.

[JonMarsh]

Thanks, Dan- fortunately, I've gotten most of the big stuff done that favors or requires the "work patio", and my GF has offered some time in her garage, too. Of course, there's a certain quid pro quo, as we'll be re-insulating her attic soon!

In the meantime, I'm counting off the days until I fly back (while sitting in the Vienna airport at my departure gate this AM!) thankfully, Vienna has decent airport WiFi!

So, back on topic, do you consider these done "for now", or have you got some specific plans underway to continue the development of how you make your waveguide/diffusor? BTW, I have some questions I'll post about the Echelon's when I get back- some things I'm curious about the BG10s.

[dlneubec]

Jon,

I'm still playing around a little to tweak the phase shield inside the horn, but pretty much completed that last night and have a pretty flat response out to 15khz or so, with a drop off of 4-5 db above that. I'll post that response when I get a chance.

I'm considering working with another DIYer to have the waveguides turned from laminated BB wood, probably with the outer ring in the same wood I have on the trim. This would be ideal from a performance/aesthetics standpoint. He would provide labor for free. However, it will be a lot of work for him and I want to be sure it is worth all that effort. I think it would probably be best for me to complete the second speaker (I've build only one so far) and XO and listen to the pair to before I consider having him to take the time to do that.

The other issue I'm wrestiling with, is this. Though I would prefer the look of laminated wood, it would likely make it very hard for anyone else to build, should there be some intrepid sole out there who wants to replicate this design. Using the PE waveguides is inexpensive and is something a lot more people could do themselves, I think.

So, to answer your question, I will build the second speaker so I can listen to a pair and finish the XO. I will probably finish the bass bins of both so that all I'm left with is to finish up the top section before next years DIY events. Then I will decide which direction to go in with the omni horn section.

I'd be happy to answer any questions I can about the Echelon's.

[dlneubec]

I've been playing around more with the phase shield idea and I think this is about the best I can do with the top end. I've done a little more minor XO tweaking as well. The graph below is a nearfield on the woofer (setup in the sealed setting) merged with the farfield response of the combined woofer and tweeter.

I started building the second speaker today. I don't think I can do any more on the crossover until I have a pair to listen to.

[Juhazi]

What a remarkable graph! Being omni, I bet that you'll have to attenuate 2-6 (-15) kHz area or the speakers may sound harsh?

[dlneubec]

Juhazi,

So far, I have not found that to be the case, but that is auditioning with just one speaker, not a pair and in my garage, not in a typical room. If anything, I would expect the upper end to be a little less promnent in a room with drapes, carpets, furniture, etc.

This has also not been the case with prior "omni" speakers I've designed, though those were mostly hybrids of omni and monopole or omni/bipole, so this one could be different, being essentially omni in the horizontal plane.

I'll find out more when I have the pair built and can audition them inside my home. I'm sure some voicing adjustments will need to be made at that time.