Hey guys...we need a little rallying here... - Page 28

OT but interesting....

http://www.supravox.fr/anglais/haut_...av_1_pouce.htm

Its not CD, but notice the shape and mouth dimensions.

At some point we have to transition from the 16.5deg angle to the angle of the SEOS waveguide so there is always going to be a transition point where the angles change and diffraction happens.

Is there any other way of doing this?

Most exciting CD horn is Smith type JMLC, "Midrange" horn.

This is how it should (IMHO) look like at the throat.

This pretty much answers the question to the new issue right?

Yes, I think Earl was a little off in his 6.5deg value. It should have been 7.3deg because he is only referring to the half angle of the 14.6deg conical opening.

Jzagaja, if there is no way to manufacture a waveguide that starts at the green arrow from my prior drawing I think we have a real issue.

Maybe I'm misinterpreting what you are saying. Are proposing that the conical section is cut off after manufacturing? If so, that would be fine so long as the throat matches the 1" exit of the drivers.

I don't think so. I understand that the CD exit is conical and that ideally it would be an OS profile but that is not a possibility right now. Since we have to deal with off the shelf parts we want to transition as smoothly and as soon as possible from the conical CD exit angle to the OS profile. Extending the conical portion of the CD into the WG is not a good thing.

The idea behind starting the WG throat and OS profile where the tangent angle equals the exit angle is to minimize the throat diffraction. It is the core concept behind the OS. Transitioning at this point is the smoothest possible transition point from conical to OS.

Make sense?


I agree that would make for the ideal CD exit. Basically start the OS profile in the phase plug. Even "more ideal" would be to make it ellipitical. Do you guys have the means to prototype this? If so, PM me offline when you get a chance.

I just want to make sure my posts don't make it seem like I'm knocking Jzagaja. I think what he is doing is great and he is very capable. I simply want to make sure there isn't a deficiency in the design that is avoidable. J, please keep up the good work.

Max

It will start - this extension is only technological step required for different drivers with slightly different throat diameter. Without it every horn is useless.

Are you saying the conical section is there to help match up to variances in the CD exit diameters?

Yes it takes into account material shrinkage, mold wearing, throat diameter variations in drivers.

Bump.

I know that there are things happening with this project that are happening in the background, but I was wondering if we could hear about it.
Even if it is simple as: Yep we are still working on this.
Given that it has been a week.

I was told they might have time to start on it this week. Obviously at this time of year, things can change so I didn't want to bother them for a few days. Maybe I'll send them an e-mail tomorrow just to see how things are progressing.

Thanks.

I knew that we were waiting on this part, and obviously this time of year is hectic on everyone. I just wanted to keep everyone posted and up to date with this.

I got an e-mail from them letting me know that they're currently working on it. So it's a little ahead of schedule.

We can start think on another OS-18, SEOS-10, JMLC-OS-18...

I vote for a SEOS-18 90x45...

Earlier I thought the SEOS-10 might be a neat idea. I sent an e-mail this morning letting him know. The SEOS-12 is probably too close to the 15, so dropping down to a 10" might not be bad.

But I'm wondering if it would make sense to get testing done on the SEOS-15 first? I'm going to be sending that prototype to Zilch.

Heck if you have the machinery to do the 10" right now, and if it keeps prototype pricing down because you're doing similar designs at the same time, I'm in. I'll e-mail you later.

I think anything over a 15" baffle mount might be a tough sell. Maybe an OS-15? Not sure it's a big enough jump over the OS-12 though.

2 votes now for that one.


No doubt the larger choice is not popular with this crowd and its not going to be a mass market purchase but I still want one. Its what I want in my 2011 HT re-do.

I am not size restricted at all, though 18 would be overkill for my room. (But who here isn't about overkill?)

I would be very interested in the 18 size, though I do agree and I think we need to measure the one that we are working on now first.

Eric, will have to answer it all but if they are offering a second choice for some great value then its not a bad idea to get 2 instead of 1 now. Donig one later might cost more money.

I think the SEOS-12 is the sweet spott.

As Geddes says about his own designs, the 12" is very close in performance to the 15" at half the box size and cost, but a significant step up in performance over the 10".

This actually might be a great idea for people looking to do Surrounds in the same type of format. if the space/cost/time is right.

He's talking primarily about the woofer with those comments, though, IIRC. He was also talking about doing a speaker with a 15" WG and a 12" woofer.

Geddes has commented several times that smaller waveguides are not as good as the larger ones. He likes to Crossover below 1KHz and he likes directivity down that low, a 10" OS waveguide gives him neither.

Im one of those that thinks larger woofers are not the best SQ choices above 1KHz. Maybe matching a 6.5" pure mid range with a smaller waveguide will work but listening to 10", 12 and 15" woofers above 1kHz has me wondering if they are as good as pure mid range smaller choices. I have some higher quality choices too so its not a question of driver choice.

I remember a discussion on DIyAudio about the size of the piston dictate the hypothetical limits where it performs the best. There was a formula used too but I can not find it right now.

Hi Penn,
Generally speaking the directivity control of the woofer narrows or begins beaming as the wavelength approaches the piston diameter, hence bigger woofers beam at lower frequency's than the smaller woofers. This is not taking into account cone breakup that can also limit a woofer's useful upper limit. Cone breakup is usually used to extend the response of a woofer, kind of a trick if you will. One must be careful when looking at data sheets; a "nice extended response" on a big pro driver is most commonly a byproduct of the cone breakup, it is distortion. Look for ripples in the electrical phase and impedance, also note that paper cones with the circular ribs are specifically engineered to use the breakup to extend the response.

Won't be too long from now for the prototype to be completed. They want to make sure everything is cured and stabilized. The company does great work, so these should look really nice.


By the way, I'm going to try and set up a way to get all those past "Group Buys" from other websites into one package to be shipped here from Poland. That shipment won't contain these WG's, but any of the other ones they offer. Like the Iwata-300! Even the empty "mummie" cabinets.

Shipping is going to stink no matter how you slice it, but a full pallet should hopefully knock that down a bit per item. I'll drive up to Chicago to pick up the pallet, then ship each piece out. Yes, it's a long drive, but I'm still going to do it. I'll give more info on all this later.

I hope this isn't going too far off the current path of this thread, but does anyone know how to progress from a styrofoam form to a usable waveguide? It occurs to me that it shouldn't be too difficult to make a series of thin elliptical shaped sheets of styrofoam, stack them, and smooth down the edges to make a form for the inside of a waveguide. (I haven't actually tried this, but it seems like that part should be pretty straightforward).

The next step isn't so straightforward, though. I'd need to make the template able to withstand the temperature and chemical effects of molding an actual guide from it. Is there something that could be used to coat it to seal, smooth, and vapor proof it? Maybe white glue? I know that a lot of chemicals turn styro into goo.

Or maybe there would have to be more steps -- make a guide in plaster from the stryo, then make another template (using ??) from the plaster guide, then fabricate from there? Any molding experts out there, or does anyone know any good books on the subject.

Yes, this is toward making an 18 or 20" EOS waveguide, if I get time to try.

No, he was comparing the Abbey and Summa.



It's not always that bad.

If the cone profile is curvilinear and the material well damped, the high freq response isn't output from the uncontrolled breakup areas but from the center of the cone decoupling from the outer portion.

This reduces the effective mass being driven and widens dispersion.