gedlee said:
I've heard that Bruce Edgar is changing out phase plugs in his top model; probably a JBL driver, but just speculation.
Perhaps you can get an incomplete driver from the manufacturer and put in a phase plug. You could probably find a local machinist to do it for you. It's been a while since I looked at the one I have apart, but I seem to recall it was probably press fit.
Interesting about the phase plugs coming out, but I think that you guys are missing my point. I have neither the time nor the finances to do prototyping work. It makes no sense to prototype a new phase plug if there isn't some sense of a viable business. I don't have that sense. I need to see some means of reasonable return before I invest significant time and money into something. I don't see that here.
Improved sound quality!? All twenty people who care about such things? There simply isn't a great deal of demand for sound quality in the marketplace. There may be here in its own small way (if it DIY), but certainly not enough to warrant a new compression driver.
Eminence agreed to custom make me a compression driver, but when we went through the tooling costs etc. it simply wasn't a viable business proposition.
What has to change for any of this to make sense is the interest level in high quality sound. As long as it satys low, like it is now, there will never be a market large enough to support development work.
Plastic molding:
I am not going to pick appart the proposals, but I will say that I tried three different methods, destroyed three molds in the process and spent hundreds of hours before I could make decent waveguides with the casting method. Now that I can do that, all I can say is that you will be far better off just buying them from me than you will be trying all of these things yourself.
Improved sound quality!? All twenty people who care about such things? There simply isn't a great deal of demand for sound quality in the marketplace. There may be here in its own small way (if it DIY), but certainly not enough to warrant a new compression driver.
Eminence agreed to custom make me a compression driver, but when we went through the tooling costs etc. it simply wasn't a viable business proposition.
What has to change for any of this to make sense is the interest level in high quality sound. As long as it satys low, like it is now, there will never be a market large enough to support development work.
Plastic molding:
I am not going to pick appart the proposals, but I will say that I tried three different methods, destroyed three molds in the process and spent hundreds of hours before I could make decent waveguides with the casting method. Now that I can do that, all I can say is that you will be far better off just buying them from me than you will be trying all of these things yourself.
NO, not in general, only in cases where the waveguide does not add significant HOMs would the advantages of my phase plug design be evident. There-in lies the problem. Until everyone is using my waveguide designs there isn't much point. And based on my and several others opinions of my Summas there isn't likely to be much gain. Its not like the situation in the Summas is a glaring problem. In fact no problem is evident at all. The problem is that the Summas are too big, and too expensive. So thats where I spend my resources these days. Solve the big problems - don't obsess over the little ones.
I have designs, and one-offs can be cut on my lathe (I have a machine lathe and the plugs can be cut from alluminum stock), but thats a lot of time, something that I don't have free to give. Thats the point. I find the Summas just fine the way they are so I'm not driven to "improve" them and I can't just donate my time. I just don't see where my motivation is coming from. "Sharing" the costs implies that I'm part of that sharing, but I fail to see the benefit to me.
Then there are the molds to be made and on and on. I'm a one man show here and thats everything from Accounts Receivable to Packaging and Shipping and Marketing. There is no free time.
For me to do phase plugs for sale or something like that I think that you would be looking at several hundred dollars each. It just doesn't make sense unless the volumes are such that the impact on the piece cost is insignificant.
If you are suggesting that you arrainge for a group of people to pay for the tooling costs to have Eminence build them then I'm all for that. But your looking at about $10,000. Not chump change. And in the end there is no guarantee that it will make that much audible difference and clearly ONLY if you use my waveguides.
Then there are the molds to be made and on and on. I'm a one man show here and thats everything from Accounts Receivable to Packaging and Shipping and Marketing. There is no free time.
For me to do phase plugs for sale or something like that I think that you would be looking at several hundred dollars each. It just doesn't make sense unless the volumes are such that the impact on the piece cost is insignificant.
If you are suggesting that you arrainge for a group of people to pay for the tooling costs to have Eminence build them then I'm all for that. But your looking at about $10,000. Not chump change. And in the end there is no guarantee that it will make that much audible difference and clearly ONLY if you use my waveguides.
Vertical nulls
I think you guys should listen to Earl's hesitance to go larger than 12" or 15" for another reason.
A larger horn necessarily increases the vertical distance between the acoustic centers of the midwoofer and tweeter. The further apart they are, the narrower the angle of coherent summing. A 15" to 18" round tweeter horn above a 15" midwoofer can't possibly be less than 15" apart, center-to-center. That gives you about 10 degrees above and below the forward axis where nulls form. Pretty narrow, in my opinion.
Look at the vertical pattern when deciding how large your horn should be. In general, bigger is better. But where these vertical nulls are concerned, there's a trade-off that probably should be considered. Ten degrees is not a lot.
gedlee said:
I think you guys should listen to Earl's hesitance to go larger than 12" or 15" for another reason.
A larger horn necessarily increases the vertical distance between the acoustic centers of the midwoofer and tweeter. The further apart they are, the narrower the angle of coherent summing. A 15" to 18" round tweeter horn above a 15" midwoofer can't possibly be less than 15" apart, center-to-center. That gives you about 10 degrees above and below the forward axis where nulls form. Pretty narrow, in my opinion.
Look at the vertical pattern when deciding how large your horn should be. In general, bigger is better. But where these vertical nulls are concerned, there's a trade-off that probably should be considered. Ten degrees is not a lot.
Wayne - on this point we can agree (which seems to be rare). The disadvantages are getting too great for the advantages. There is a sweat spot. Clearly 45° (90 total) seems to be it for directivity, and 10" is too small to control the pattern well, 12" is a lot better. 15" may be better in terms of pattern control, but its pushing the distance between the drivers up - not good. 18" is most likely too much in this regard.
I found the 12"waveguide and 12" woofer in the ESP12 to not sound quite as good as the ESP15 (although I won't bet on that limited data), but it was very close. Its unclear if the waveguide made the difference or the woofer or both. That is as yet undetermined.
I found the 12"waveguide and 12" woofer in the ESP12 to not sound quite as good as the ESP15 (although I won't bet on that limited data), but it was very close. Its unclear if the waveguide made the difference or the woofer or both. That is as yet undetermined.
Dr Geddes,
I doubt that while 15inch is said to work perfectly, 18inch should allready be a bad distance. It isnt that much of a difference, regarding the vertical pattern.
Also, thanks for the concerns about building waveguides - i bet most of us here are inexperienced but eager to try it out. If you could drop some practical hints about how to be successfull, it would be really great.
I doubt that while 15inch is said to work perfectly, 18inch should allready be a bad distance. It isnt that much of a difference, regarding the vertical pattern.
Also, thanks for the concerns about building waveguides - i bet most of us here are inexperienced but eager to try it out. If you could drop some practical hints about how to be successfull, it would be really great.
All that I can say about making your own waveguides is to go in knowing how difficult it will be. Its not as simple as cutting a couple of boards on a table saw. It takes messy, smelly materials, tools that are uncommon, a lot of mistakes and trail and error.
It just bothers me whan I see people post how easy this "should be" when I spent countless hours and dollars to get it right. Its not going to be easy or inexpensive.
Here is what I ended up with - a two part mold, one part in alluminum and the other in steel. The molds cost about $2500. A fixture to clamp all this together very tightly as even a small leak will ruin the parts. I had to find a local company who makes two part polyurethane with a cure time of about 10 minutes. I bought three different companies products until I found one that worked the way that I needed it to work - one cured too fast, I couldn't work that fast and one was not rigid enough. In each case I had to buy about $500 worth of material just to try it. All told I spent about 200 hours to get the first part right.
You can get decent materials from TAP Plastcs but its expensive. Mine comes from a local shop in Lansing, MI.
It just bothers me whan I see people post how easy this "should be" when I spent countless hours and dollars to get it right. Its not going to be easy or inexpensive.
Here is what I ended up with - a two part mold, one part in alluminum and the other in steel. The molds cost about $2500. A fixture to clamp all this together very tightly as even a small leak will ruin the parts. I had to find a local company who makes two part polyurethane with a cure time of about 10 minutes. I bought three different companies products until I found one that worked the way that I needed it to work - one cured too fast, I couldn't work that fast and one was not rigid enough. In each case I had to buy about $500 worth of material just to try it. All told I spent about 200 hours to get the first part right.
You can get decent materials from TAP Plastcs but its expensive. Mine comes from a local shop in Lansing, MI.
Vertical nulls
There are a handful of things to balance here. The smaller midwoofer drives the crossover point up, in order to match horizontal directivity. But that also makes the vertical null angle smaller. Larger horns have better pattern control, but they increase the distance between sound sources, again, making the null angle smaller. It seems to me that getting the horizontal pattern to match at 90 degrees is actually the easiest part. Getting a horn size/shape and crossover that works nicely in the vertical is the hard part.
Good luck doing that with a round horn.
gedlee said:
There are a handful of things to balance here. The smaller midwoofer drives the crossover point up, in order to match horizontal directivity. But that also makes the vertical null angle smaller. Larger horns have better pattern control, but they increase the distance between sound sources, again, making the null angle smaller. It seems to me that getting the horizontal pattern to match at 90 degrees is actually the easiest part. Getting a horn size/shape and crossover that works nicely in the vertical is the hard part.
Good luck doing that with a round horn.
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