Dayton RS28F on PE 8" waveguide

[Mark K]

I finally got around to a quick mock up of the RS28F on PE 8" waveguide combo.



More info can be found on my RS225 dipole project ruminations page...

http://www.audioheuristics.org/RS225%20dipole%20project/whats_new.htm

[JonMarsh]

Interesting, Mark. Would have been nice if things have been a little more closely spaced in the 8-14 kHz area. Did you do any measurement curves more focussed on just the 0-45 range? And averaging that? What do you think about the transition from the waveguide to the baffle, which looks a little abrupt- any thoughts on that?

[Mark K]

Interesting, Mark. Would have been nice if things have been a little more closely spaced in the 8-14 kHz area. Did you do any measurement curves more focussed on just the 0-45 range? And averaging that? What do you think about the transition from the waveguide to the baffle, which looks a little abrupt- any thoughts on that?

Well, the separation of the off axis curves is exaggerated a bit, maybe 2 dB or so. My off axis measuring setup isn't quite correct for a horn. As you go further off axis, the driver distance increases somewhat. So I think that's somewhat of an artifact.

I plan on trying two other mounting arrangements. For the first, I'm going to mill down the WG even more so it fits over the edge of the RS28F (i.e. take off the outer faceplate of the RS28. There will be more of an edge, on the other hand the dome will be farther in, and the WG will be a bit less deep, making this arrangement a bit more shallow.

With the other WG, I'm going to mill it a bit less so it matches up a bit better. There will be less of a transition irregularity, but the effective depth will be a bit more.

So we'll see if either is an improvement.

I think I can live with the transition to the baffle. Not ideal, but not bad. I really want to try to stick with the RS because it's otherwise smooth and remarkably low distorting. The MCM might be smoother, but the directivity probably starts a bit higher than I'd like. The PE 10 may be better, but it's just too big...

PS did you see this graph? I added it after my initial post.



But I'll do a few more detailed 5 degree plots next week out to 45 deg



So this may represent the best compromise.

[---k---]

Hi Mark,

Nice tests.

I've read once that a waveguide reduces baffle edge diffraction (and off the woofer). But, I see that you're using a massive 3" roundover. Can you comment on how important the edge treatment is when a waveguide is used???

Can you also share how you made that 3" roundover. That is impressive.

Thanks,

[Mark K]

Hi Mark,

Nice tests.

I've read once that a waveguide reduces baffle edge diffraction (and off the woofer). But, I see that you're using a massive 3" roundover. Can you comment on how important the edge treatment is when a waveguide is used???

Can you also share how you made that 3" roundover. That is impressive.

Thanks,

That's my standard test baffle. I typically make a 9x17 rectanglar insert out of 3/4 mdf. The roundover is actually from Rockler, IRC. You can buy it by the ft. You just have to cut it sort of like crown moulding. Bit of a pain. I guess I could have gone for a very larqe quasi infinite baffle or the standard IEC baffle, but this is what I came up with years ago, and so I keep using it...

I'm a proponent of roundovers as much as practical. The reality is that it's hard to roundover more than 3/4-6/4" For sure, it makes measuring and modeling easier. How important is diffraction audibly is a different matter with no easy answer.

[evilskillit]

Well Mark, thanks for giving this a shot. I have a suspicion that 2010 will be the year of the waveguide, and we will all be better for it.

[HareBrained]

Well Mark, thanks for giving this a shot. I have a suspicion that 2010 will be the year of the waveguide ...

... in a monkey coffin... :B

[dwk]

The roundover is actually from Rockler, IRC. You can buy it by the ft.

I also have some of this Rockler roundover, and unfortunately unless I'm missing something they stopped carrying it a couple years ago. Too bad, because it's pretty cool stuff. I'm still hoarding it waiting for the right project,

[Dennis H]

You can still get the roundovers at http://www.aitwood.com/ .

[Paul W]

I had some 6" AIT roundovers shipped cross-country...poorly packed and arrived in rough shape. (They were just wrapped in kraft paper.) AIT wasn't concerned about it, so I haven't purchased anything from them since.

Suggest, at the time an order is placed, you make it clear you won't pay for damaged goods.

[---k---]

Thanks Mark.

[Paul Ebert]

It appears that the roundovers can still be purchased here:

Tape Ease - MDF Quarter Rounds

I've never done business with them.

It is too bad that Rockler stopped carrying them. Maybe if enough of us asked...

[Mark K]

I did a few more measurements with waveguides of different depths

http://www.audioheuristics.org/RS225%20dipole%20project/whats_new.htm

So now it's time to redo the entire dipole baffle and get some measurements.

[JonMarsh]

You've been busy, Mark! Too bad I don't get WiFi on the airplane flights I've got tomorrow, so I could have some time to read it all!