First CD Waveguide built

[keyser]

Hi guys,

I'm going to build a constant directivity waveguided speaker. A pair of 12" midwoofers are on their way, as well as a pair of Dayton H12RW's. My intention is to be as cheap as possible, but not to compromise quality too much. The woofers will be used in semi- open baffle configuration with dampening material at the back, to let directivity shift from dipolar at the lowest frequencies to something like super-cardioid at higher frequencies.

The obvious compression driver to use with the Daytons might be the Selenium D220Ti , as it is being used frequently and with good results. It is reasonably priced too. But, it's not the cheapest around . The Eminence ASD 1001 costs half as much as the Selenium. Okay, it has lower efficiency and it is advised not to be used below 2.5 khz, but the speaker is going to be used in a normal living room, so output demanded from the speakers will probably never exceed 110 dB at 1 meter.

Plus the Seleniums are hard to obtain in The Netherlands.

What are your thought? Should I go for the sure choice of the Seleniums or might the Eminences be just as good for this application?

Cheers!

[MunkeyQ]

In my experience, the Eminence isn't great at all...you get what you pay for, big time. Even on a decent waveguide, it can't go much lower than 2.5khz without getting ragged and there's some nasty peaks at 6khz and 12khz.

I've never heard the Seleniums but the consensus seems that it's a very good driver for the price. It's a pain to get them outside of the US...look into the BMS 4524, Celestion CDX1-1745 and B&C's offerings, although they tend to be a bit more expensive. Worth it though!

[keyser]

Okay, better safe than sorry I guess. I'll try to obtain a pair of Seleniums. Thanks!

[D OB G]

Hi keyser.

I hope you have more success with the Dayton 12" WGs than I had.
Even with a 30ppi open-cell plug, and equalized flat with a DEQX, I could never remove a residual harshness, evident on vocals, and in particular with "operatic" or massed choral works.
The Dayton waveguides are not a big investment. I'd strongly suggest trying their 6" X 6" elliptical WG as well, although it can only retain pattern control down to 2.2kHz, so the 12" would have to be used higher than its directivity should dictate. (Although the WG is 80 X 40 IIRC, so it mightn't be such a bad match afterall).
Just a thought.

David

[keyser]

Hmm.. That's too bad, the 12" WG's are already on their way. Any idea as to what might have caused this problem? Did you dampen the waveguide with something like bitumen or hot-glue?

[djn]

I messed with that 12" WG and got it sounding REALLY good.....after I went three way with a tweeter. I cross over to the Phillips AD tweeter at 3500hz.

[keyser]

Okay, did you find it lacking above 3.5 khz? Many people use similarly size waveguides all the way up.

@ the mods: would any of you please change the title of this topic. Now it looks as though the speakers are already finished .

[D OB G]

djn.
That's a very interesting idea. It WAS higher up that the problem seemed to appear (tried lots of xover points). The WG seemed good down around the 1200 cut-off.

keyser.
I thoroughly damped the outside of the WGs with a very thick layer of plasticine.

David