Waveguide shootout

[Paul Spencer]

Hi guys, thought some of you might be interested in a little get together we had this weekend. Four Aussies got together on a sunny saturday, measured some compression driver + waveguide combos, set up active crossovers and listened to about 7 different versions with some dynamic torture tracks that will quickly show up any amount of harshness.

We tried two different oblate spheroids, a few econowave type waveguides (18 sound XT and a JBL lookalike) and a few popular compression drivers - Faital pro, B&C and Selenium.

Measurement setup:



We measured them and Andi put together some directivity plots like this:



You can see the summary here:

http://redspade-audio.blogspot.com/2011/01/waveguide-shootout.html

Or some of the comments in the original thread:

http://www.stereo.net.au/forums/showthread.php/31776-Waveguide-GTG

We plan to do some more, this is just the beginning!

At the end of the day we also compared a dome tweeter. There was an obvious difference but the group picked the compression drivers. It was an enjoyable day, especially when someone else is taking care of the techy side of things!

[Saurav]

Thanks for posting those directivity charts, that's interesting information. Do you have any plans of testing a single CD tweeter with multiple waveguides, and then a single WG with different tweeters? That would help separate the effect of the WG from the tweeter's design. For instance, I wonder how much the different phase plug designs affect the polar responses.

[dlneubec]

Paul,

The inexpensive 10" PE WG is a real eye-opener in your results. What was paired with it and where was the crossover point? Thanks for posting your study. I look forward to more.

[Mark K]

Paul,

The inexpensive 10" PE WG is a real eye-opener in your results. What was paired with it and where was the crossover point? Thanks for posting your study. I look forward to more.

I was glad to see that. I played around with a modified 10" PE WG in my dipole panel. (Yes, the one that never got off the ground... :tired: ) I thought the perfromance with a dome looked very reasonable. I didn't make pretty, colored directivity plots, but the equivalent off axis curves looked respectable.

Everyone was a bit ambivalent on the PE since the plastic is a bit thin, and it has an edge at the flare. Since the edge is 5" away from a very big roundover, so to speak, the diffracted wave isn't probably much compared to a non WG tweeter.

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

Anyway, it just makes me more sure to just go ahead and proceed with the PE 10"

[ttan98]

Hi,

The Dayton 10" wave guide seemed to perform well on paper, I bought a a pair from PE and mounted them on an OB configuration and crossed it around 1.7KHz. The sound I obtained was not very promising I was getting a "honking" sound(not severe though) typical of complain from waveguide users.

I then replaced it with this waveguide, RCF, H100(cheap too) and coupled it with DE250, the combo was a good match. see details of RCF at this site:

http://www.loudspeakersplus.com/cgi-bin/commerce.cgi?search=action&category=RCHN

[Paul Spencer]

The day did illustrate that other measurements are needed to get more of an indication of sound quality. The polars are a useful tool, but you can't look at them and say which one would sound better. My little 6" sounded better than the better measuring Selenium/JBL guide.

Saurav,

Good suggestion. We might have done it had we started with that question. We just wanted to measure and listen and see what we found. It's given us a whole lot of questions, so now it's time to go back with some more specific things like that to chase up. So from here I think it gets even more interesting. We have our opinions, but it's always good to test them like that. This has also got me wanting to do some more reading on the topic to see what others have found.

The inexpensive 10" PE WG is a real eye-opener in your results. What was paired with it and where was the crossover point? Thanks for posting your study. I look forward to more.

Dan,
We used the Selenium D220Ti and the crossover? Hmmmm we measured only the waveguide so I don't think we had a crossover, or if we did it was probably only to protect it. Not sure if we high passed it or just limited the signal to 500 Hz.

PS - try not to notice our woodworking! Chipboard baffles cut with a jigsaw by hand here! I've seen that fancy baffle and woodwork of yours around the traps before and this is the extreme opposite end of woodworking!

Mark,
I wouldn't be put off by the Dayton by it being thin. In fact, I'd rather get it thin and cheap and fix it up than get it perfect with a price to match! Having said that, when I do actually decide on one to do properly, I'm thinking of building one from scratch, quite possibly from a CNC mould.

I had a look at your link. I'd guess that you would find Arta pretty easy to figure out. After seeing it in action I'm keen to give it a go, the plots make it easier to analyse the results. I used to look at these kinds of plots and think "what the heck am I seeing here?!" Now they just make sense.

But here's something that doesn't make sense. I tried to get results in Hornresp matching the oblate spheroid we measured. They don't match up.

http://redspade-audio.blogspot.com/2011/01/simulating-waveguides-in-hornresp.html

The charts are in there, I won't post them again.

ttan,
which CD did you used that honked? We didn't listen to the Dayton WG, but I would have liked to have heard it. It had a Seas woofer, but apparently there were issues with breakup that Andi found objectionable.

The Vifa P13 on a tiny baffle had constant directivity down to 200 Hz! We measured but didn't listen. As it was we heard about 7 combinations and that kept Andi busy making up the crossovers on MiniDSP! It was a superhero effort and made the day relaxed for the rest of us who stood back yapping most of the time until Andi said "I need quiet!" Oooops ....

[Saurav]

Saurav,

Good suggestion. We might have done it had we started with that question. We just wanted to measure and listen and see what we found.

Yeah, I know how that goes. I was most interested in the XT1086 because I've used that in the past. I don't recall the response narrowing like that in the upper treble, which is why I'd be interested in seeing that WG with a BMS / B&C tweeter.

Having said that, that was also before I had ARTA so I was looking at overlaid FR curves, and the sonograms definitely make it easier to see what's going on. I don't think I have any of my old measurements, or I'd try and run them through ARTA.

[ttan98]

I use the Dayton with the De250, a very nice CD.