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RE: Are you refering to a speaker?

Yes. I was referring to the fact that your box has a large window with an acoustically transparent diaphragm (cone) filling it.

I read through the Linkwitz diffraction from baffle edges one. He doesn't seem to think it very important but that doesn't seem to be the case from what little dinking I have done. I was able to greatly improve the clarity of my old Infinity Q3 speakers by putting a little bit of weather stripping along the emit tweeters to block surface transmission to the nearby cabinet edge. I've done a similar thing to the Celestion 3's I use in the study with good results. The newer infinity speakers I have solved it by placing the front surface of the film drivers tangent to the front of the grill cloth frame and have a piece of restickable tape cover the small gap in the cut-out. Thus the surface radiation is loaded right into the edge of the grill cloth and the whole shebang is tapered and blends into a rounded taper at the cabinet edge. In other words, they have gone to a lot of effort to manage diffraction.

As I stated, it is frequency and baffle shape dependent (I view a absorbers as a bit too crude, though effective). If you are that concerned with it, a minimum of a 3" roundover on the baffle edges should be used.

I don't have any proof, but I think the most audible problem is the delayed radiation messing up the time-domain response.

The delayed radiation would have to show in frequency response as well. It would just require sufficient detail. If radiation messing up the time-domain response is of serious concern to you, you do realize that the inside of your enclosure will not be 100% absorptive of the rear wave reflection? And there's this acoustically transparent window for it to come out back through...

I did indeed look at some of the Geddes site a few months ago but it was in regard to his distortion metric stuff.

He had a whole series on measurement of loudspeakers. I need to locate it, scan and host for download. It's a must read (for those in good mental health. Most here could not comprehend it and may react with horror).

As far as using a dipole, I don't see how that would help edge re-radiation.

What I cited was more a reference to baffle step and the difference between a boxed monopole. If the (dipole) source is in its omni range, there will be cancellation from the opposite phase secondary source from the rear radiation. As the driver becomes more directional, there will be less energy directed at the baffle edge. Here is some measurements of a dipole tweeter source (link).

It sort of looked like you are using a coaxial speaker and I can see how that may reduce the problem. I'd like to see in more detail what you are doing, if you have you already posted more detail somewhere I'd appreciate a link.

Yes, that is a coax. Yes it does reduce the problem, though most such drivers could be much better if designed properly. I did post the on axis FR in another thread
http://www.audioasylum.com/forums/hug/messages/13/135399.html
but I need to do post a lot more, including off axis and polars, which I would prefer to do outside. The rain here has been incessant. I'll get to it eventually.

cheers,

AJ






Funny thing, in Audiophile circles if you can hear things others cannot, you are revered, in society, you are sent for treatment.


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