I am pretty much convinced that fin cutting will be a part of my 511B ringing control plan. Sam P. (below) also did this and reported good results. He used a sawzall and needed to make several cuts per fin to remove enough material. How did you cut them and what tool(s) did you use? Any hind-site observations greatly appreciated.

Good idea using the radial tire matrerial (to damp radial horns!). In as much as I do play some blues and rock on my system, perhaps I should use material from off-road radials.

Regards,

AstroSonic

I had not considered a cutting wheel for cutting out the welds. I imagine that the working room was pretty tight? The hand drill I have would probably not allow a square cut with a cutting wheel - it would have to be angled in. Were you able to get reasonably straight, clean cuts? How would you describe the resulting improvements in sound quality?
Regards,
AstroSonic

I build boxes that went up to the rear flange. I wanted the ability to change the driver conveniently. If your going to use the same driver you could box the whole rear portion. On the front side the sides of the box came up to the flange but the top and bottom extended past the flange. I would consider this a matter of taste in decorating only. You could damp the lips if the cabinet covered them too.

I pretty much always multi amp this stuff. Almost all compression drivers need compensation when used in a 2way or 3way, and I wouldn't cross a 511 any lower than 750 - 1000 hz IMO

Bill

Bill

Over the years, I've crossed large-format midwoofers a variety of crossover points from 100Hz to 3kHz. Usually in a three-way system, I'm using the LF driver as a woofer and crossing between 200Hz and 500Hz. That tends to keep the woofer in its pistonic range, or within an octave of it. I tend to expect 250Hz is pistonic range and 500Hz is the first breakup mode.

In a two-way system, I'm usually crossing over much higher, in the octave where midwoofer DI and compression horn DI match - between 800Hz and 1.6kHz. In this regard, my designs are much like JBL's two-way monitor speakers that are almost always crossed over above 1kHz. The JBL 68881 is a 1.5kHz passive two-way crossover and it is a good example, being used with a 15" midwoofer and a 1" exit compression horn tweeter on a radial horn flare.

But whether a person uses two-way or three-way configurations, the drivers are going to be used in their breakup modes over a large part of the audio band. I think its important to consider all things, and drivers that are designed to be used at high frequencies usually have well-behaved cone flex patterns and don't become excessively anomalous. Lots of high-efficiency drivers are made this way, especially compression drivers and high-efficiency large format cone midrange and midwoofer drivers. I find that a well-designed midwoofer operates pretty well in the vocal range, provided its breakup modes are well damped, which is something that is easy to determine from its response graph.