Hey guys...we need a little rallying here... - Page 3

I might know a guy that can create the prototype using a CNC milling machine, I'd have to ask though. If so, I can then create the duplicates. I'll try to call on Monday to see what type of file they need. The company he works for might actually be able to make the duplicates too, I'll find that out as well.

If anyone here can create a file giving exact measurements of what most DIY guys might want, that would help of course. I'm just beginning to learn about the waveguides, so as of now, I really don't know which ones have the most demand. My work season has finally slowed down, so I can devote a decent amount of time to getting this done if you guys want to.


There is one thing that could cause a problem. I'm sure Zilch would test the one that was made, but I think we would really have to make sure it was going to test pretty good. The prototype work wouldn't be super cheap and each change would require a new prototype. And I think some of the WG's that look like they'd do okay don't perform as well as people thought? At least I think that was the case.

Doing a wood plug prototype would take tons of time, as you would be cutting many ellipses in wood, gluing them all together and filling and sanding to shape.

Unfortunately, using a CNC mill, unless it is a super one with LOTS of tool time will leave tooling marks that will also have to be hand sanded to final shape. With the wood option, you can at least see all the wood 'corners' as you are sanding to use a guide that you have sanded far enough....

Either way, you are looking at having someone that has great skill to do the final sanding....

Maybe a combination of using a CNC router table and using it to cut 1/8" wood into many ellipses would be a good compromise? Fill the 'corners' with something like Bondo (silicon microballoons and a low-shrink resin system, take your pick) and sand to final shape......then the part-making can begin....use a good, viscous resin for the 'finish', then use pigmented resin and choppped strand mat and resin would be pretty cheap and effective. you can then layer reinforcing cloth and resin on that to strengthen the build, and then peel-n-seal....the interface for the compression driver would be then added...

JSS

Maxmercy, I'm thinking of trying a different material for the original prototype. But you're right, it would take a decent amount of time either way.

If you went with wood, how thin do you think the layers would have to be to make it easier to get the exact shape? Are you talking about 1/8", or less than that?

Maybe this could be an option as a source?

http://www.woodlotharvest.com/Index/home.html

I'd go with 1/8" or 1/4" for the areas that change less (near the throat), 1/8" or even 1/16" for the areas that change the most (near the mouth). A bolt-on driver would be easier than a screw-on....Just make the horn onto the flange you will use to bolt the driver onto.....

For cost savings, use hardboard instead of wood for the initial plug. Do it in an insulated and climate controlled shop to avoid thermal and/or hygroscopic expansion problems.

Make the female mold from the original plug w/ fiberglass, then use the fiberglass 'master' to cast some silicone (or fiberglass) 'slave' plugs you can send out to individual users. Do not keep using the plug, just use it to make masters as needed. Too much work is in the plug to be using it often.

I'm sure there are other ways to do this, but this is how I would go about it with limited tooling and equipment...

JSS

I was thinking it could be machined from a more durable material than wood (metal or plastic). It would likely cost more and it would require recouping that cost. Bottomline is that this won't be a $15 horn but if it is the only elliptical OS horn available to DIYers it could be worth something.

I didn't buy the QSC's simply because they are cheap. I would have probably paid $100/ea for them simply because there aren't many good options out there. The 18Sound horns aren't what I'm looking for. Geddes stuff is way to expensive and axisymmetric. DDS is hit and miss plus it is expensive. QSC was doing us a favor really and it probably doesn't make business sense for them to sell to DIYers. You definitely can't count on something like that. Now Zilch has made a bunch of nice designs for a very limited number of people.

I know some people did buy the QSC simply due to its price. What percent would have bought one if it were $100? How about $100 and significantly improved?

I have no clue what a "superellipse" might be.

Look back to Earl's early work in OS, and you'll find the first experiments and publications used an elliptical design. The measurements evidence the on-axis "notch of perfection" in those, as well. That's the primary (stated, at least) reason he is considering alternatives to his current axisymmetric waveguides.

He claims that the (trade secret) knowledge he has accrued during the intervening years MAY allow him to come up with an improved elliptical design. He has not reported any progress with his prototype toward achieving these objectives of late, however....

Edit: http://en.wikipedia.org/wiki/Superellipse

Does not address the symmetry/center-to-center distance issue, apparently.

I agree about the goodness of the DE250.


I thought the clay was just for filling in any gap, not for determining geometry.



Presuming ND means a neodymium magnet, less weight.

Doesn't the size need to be decided on?

My vote is for a WG matching to a 12" driver with XO close to 1 kHz.

Zilch, do you have a take on why the Geddes OS horns have a null on-axis? Is it a function of the ellipse (in Geddes case a "circular ellipse") or the large CTC spacing or both? The QSC horn is essentially a very large N superellipse or "squircle". It doesn't exhibit this null to the best of my knowledge.

At the very least, an elliptical OS WG should improve on the CTC spacing from Geddes round designs. It could give us a nice low horizontal pattern control without intruding on the vertical with a narrow null.

These are the specs I'd shoot for with the EOS WG:

• 90x50 pattern
• Good directivity down to 800-1000hz (~17" wide before roundover)
• CTC spacing of ~10.5" for a 12" driver (~8" tall mouth with a notched roundover)
• Match a 15* driver exit angle to work well with the DE250 and CP380
• Work well with a 1000hz crossover point

I guess I could live with the "Geddes null"/"notch of perfection" if those specs are met at a reasonable price.

Could it be that JBL's non-symmetric horns are addressing Geddes's null issue? It would be difficult to build an odd mouth shape unless we could get a mathematical representation of the specific mouth shape like we can with a circle, ellipse or rectangle.

Yes, with any symmetrical shape, the diffraction occurring at the mouth exit, whether it's from a sharp edge or a roundover, sums and interferes on axis as a function of wavelength. Perfectly round shapes are the worst in this, and the on-axis notch in Earl's designs is greater than 6 dB deep, and owing to the roundover, presumably, fairly wide. By 7.5° off-axis, it's all but gone, but its presence mandates that his designs do not perform well on-axis, and he cautions not to listen or EQ them there. I suspect that's why JBL and others generally do not use axisymmetrics in their designs -- an axial response anomaly of this magnitude is a deal-breaker in SR applications.

I would advise against locking into any waveguide design so wide as 17" plus. Listen to Earl on this one, and optimize for a total width more on the scale of Abbey. QSC got it right, in my view, at 14" wide with roundover; 15" total width would be a practical maximum. If Brandon's preliminary measurements are correct, that'll get down to 1 kHz for mating with 15" woofers at 90°, and still not be overly wide for use with 12s. Note that Earl's designs are NOT 90° (-6 dB), rather, somewhat narrower. I'm with Noah on this -- 12" woofers are more easily workable, and probably ideal.

Yes, there are those who want to do much bigger, and they are vocal about that, but statistically, they are not "mainstream," and not going to be truly satisfied unless they can get down to 800 Hz, or an octave lower, even, with large-format drivers, added supertweeters, and yada, yada....

Not in my experience. I tried it with the original Ewave waveguide and some woofers. The problem that comes up is that the total highpass cutoff slope on the waveguide (acoustical + electrical) is pretty steep, so below the point where the horn stops providing significant output you are left with two separate woofers spaced fairly wide apart and both covering around 1kHz, which gives them notches at smaller angles than you'd get if you just used a single woofer and horn which can get closer together. MTM can make your horn's axis the same as the system's axis, but seems to narrow the vertical null-free zone.

I've noticed that same notch on some Tannoy coax's and never knew why. Thanks. I assume the less "round" the mouth is, the less this notch exists. For instance a square would have much less than a circle (or rectangle vs ellipse). In that case, a superellipse with a higher N would make the ellipse less "round" and possibly lessen the null.

I found a quote from Geddes on DIYA saying that his ideal was an 18" wide WG mated to a 12" woofer. (http://www.diyaudio.com/forums/multi...on-thread.html) He doesn't specify if that includes the roundover or if it is the OS portion only.

What is wrong with a wider WG? Is it extra horn depth making passive crossovers more difficult? Cabinet size?

I'd personally like to take advantage of the DE250/CP380's ability to play down to 1000hz. I'd also like the WG to hold pattern below my crossover point to some extent as well since I'm not going to use a brickwall filter. I guess I'd like something closer to the large format experience without the drawbacks in the higher frequencies. I'm not sure any of this stuff is "mainstream" but you are right it would make for pretty large enclosures. There is probably a compromise to be had.

No doubt there are some that would like the 18" WG, but I bet most people think it's just too big. The end design could be over 20" wide.

As for the less 'round' mouth, do you mean something like this:

Well, filling the gap and smoothing out manufacturing defects in the early models.

I think the point about the throat is that having a transition that feels smooth to your finger is more important than having it exactly follow some curve.

Random thoughts, grain of salt, blah, blah:

My QSC horns have an initial angle much steeper than any CD. And the hole isn't even round. I figure I'll need to add a wooden spacer and sand it and the horn to get a nice, smooth transition.

If the initial angle of the horn is too shallow, it's easy to fix with sanding. If it's too steep, you have to add material and then sand. See above.

Augerpro is hearing something he doesn't like with the Beyma and the QSC. He likes a budget B&C better. Throat mismatch?

Tom Danley always stresses that you can't just pick a driver and a horn. You have to pick a driver and a horn that work well together. He says the non-Neo BMS works as well as anything he's seen with conical horns -- which implies horns with a less-than-perfect throat transition.

The four 1.5" exit re-entrant ring radiator BMS 4555s?

[In the other computer, apparently.... ]

Edit: Here go:



That's dialed in on vintage Altec Model 19 HF comp plus a spike killer LCR notch at the very top, maybe, as I recall. Same settings for all four; I just swapped them onto the JBL PT-F95HF waveguide....

how about this for rallying:

http://www.youtube.com/watch?v=iTLB3wFM9nU

I have read some opinion that using thick felt in the gap between the horn and the CD helps eliminate the HOM produced by the difference in angles. I couldnt get valid meaurements on that topic though.


I can hear something different with the BMS vs the Radian. I can not spot it in the measurement differences. The BMS is just cleaner sounding.

I never read that Brandon is having issues with the Beyma, from all posts about them and the QSC I would have thought they are the best choices. I want to use Brandon's Beyma XOs but if the B&C option is better then I will buy that instead.

Even DL86 and A9X love the Beyma choice with QSC

Im not getting this "not mainstream" stuff. None of this is really mainstream period in the first place. I also get the whole thing that you are on Wayne's side vs Geddes, Alliances are formed since Geddes was not nice about the original Econo waveguide builds which I also think sounds less then perfect with the JBL/Selenium original choices. We have to remember Geddes Summa's are large speakers that have an incredible track record for measurements and sound so lot of discussion about nothing in my books, just setup the speakers and do the right XOs. Plus you just have to look at Paul W's raptor build to see how a larger waveguide can be used successfully, he does not add a supertweeter either.

We set XOs in the 1KHz to 1500Hz range because of the size choices but that is really still a compromise to the best SQ , XOing lower then 900Hz does improve the voicing/SQ of the speaker (Geddes didnt blindly do this for no reason). Its nicer to push more vocals onto one driver. It also takes stress off the larger woofers because running them 60Hz to past 1000Hz has its own issues.

Of course we have been through this many times already, I just know there are succesful builds on both side of the aisle and everyone has to simply pick their compromises they want to live with. I would worry less about nulls at specific angles and more about overall voicing SQ myself since we can control those nulls we can not control the voicing.

Catapult, I've noticed the same thing about the shallow exit of the QSC horn. My guess is that QSC was dealing with a number of compromises concerning packaging which is a big concern with SR applications. Maybe it is related to the CD's QSC uses. It doesn't seem to meet the OS ideal in the throat.

That BMS on the JBL looks nice but it is a 1.5" exit which is an odd size therefore there are few alternatives and that horn doesn't hold pattern low enough. It is a very nice setup though. I'd also like to see polars with the 4555 on that horn. Does JBL have 1" PT horn that holds pattern to 1khz?

As was discussed in another thread, there doesn't appear to be a 1" throat constant directivity horn available to the public that holds pattern down to 1khz. My belief is that for SR applications, power handling is much more of a concern than for HT apps therefore the CDs we could play down to 800-900hz wouldn't hold up in SR applications. That is why the large format drivers are used instead...but they have obvious drawbacks in a home setting.

Concerning horn width, I agree that some people would like to compromise how low pattern is held in order to have smaller cabinets. I imagine some others could live with the larger horn in order to get the ultimate performance. I guess I'd fall into the latter camp but I'm pretty happy playing with the QSC horns right now.

IMO, the Zilch/Parham vs Geddes is overblown. I don't know about the personal differences that may or may not exist, but from a technical perspective they have much more in common than not. I think the main differences are more an issue of where each guy chooses to make the necessary compromises.

It appears that Zlich likes to design speakers that are easy to build/adapt. He is the MacGyver of horn designers. What he has done with the Econowave movement is pretty awesome and a great contribution IMO.

A wider wg would not fit in a pre-built box or many existing cabinets and would make it less "econowave-friendly". A wider WG would also lend itself to a more optimal result, IMO.

Now that sounds easier to DIY.....conical is not super-tough.

JSS

So how hard would it be to modify the jbl to a 1" exit? Or would changing that portion simply screw things up?

JBL offers it in both 1.5" and 1" variants. The 1" is the original $9.90 EconoWaveguide, which we cross at 1.6 kHz. They run the 1.5" lower, but I doubt it holds pattern control well down to 1 kHz or below; I could measure easy enough, though.

Both are 12" x 6.5", 90° x 50° pattern, with minimal mouth roundover. As I view Brandon's study of the 1" version in comparison to the QSC 152i, they exhibit similar pattern control charactistics. It's the integral mouth roundover in the QSC that makes it 14" x 10" in my view; the "business" portions of the two are similar in scale.


I have plenty of wider waveguides, up to and including the 30" JBL Screen Array, which I studied in another thread here, and which also comes in both 1" and 1.5" variants. Yes, the big ones sound bigger, and are more transparent down to lower frequencies, but they are also impractical, so I ask what I consider to be the appropriate question: "What is reasonable to build and will work for the broadest range of applications?"

This K2-H9800, for example, does NOT suck:

I certainly don't believe the K2-H8900 sucks although I haven't heard them. I also don't mean to imply that the QSC sucks or any of your econowave designs. Speaker building is an exercise in compromise. I think your econowave designs are top notch when you take into account the parameters you've set for yourself.

The JBL 2374 is a nice horn but 30" would make my proposed 18-20" wide horn look tiny. It also costs $150 although that might not be far off the cost of an elliptical OS when it is all said and done.

So Zilch, you'd prefer basically a slightly improved QSC 152 version (elliptical OS, 90x50, better throat transition, similar dimensions to the QSC). I'd prefer the same but a little bigger, but I would be thrilled with an improved 152 too. I understand that it would serve a larger market.

Why not make the mold out of foam and then fiberglass it?

H9800 is 18" wide, actually, and H4338, the enlarged version of it, arguably JBL's best TOTL biradial short of Everest II, just over 20". I'm just arguing that, in terms of practicality, 152i at 14" is a better DIY format. Abbey is 15" total cabinet width, and more in keeping with my own perception of rational scale, and going back to where I started this, I believe Earl would agree.

Yes, there's a market for K2-S9900, the scaled-down Everest II at 22" wide:

http://www.audioheritage.org/vbullet...24086-K2-s9900

Summa is 24":

http://www.gedlee.com/summa_.htm

[Just tryin' to put some numbers on real stuff here.... ]

That was sort of what I was planning, but using something different than fiberglass to cover it. Once you get the exact design, adding fiberglass could change the shape of the mold a little, and certainly make sanding much harder and time consuming.

I've ordered a bunch of items to get the ball rolling, but at this time of year, who knows how long it might take to get those items. It could be a couple weeks.

After that it might take me another couple weeks to figure out the best way to go about doing this in a productive manner. I've got quite a few ideas, but I'm not sure which one makes the most sense right now.