New WR125ST TL design

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I've been contemplating what to do with "Rosa" for a few months now and finally decided to go ahead and share the design with everyone. My thanks to David Dlugos for creating a very professional drawing of the design. I'm hoping a few people will take the plunge and build this little beauty. It runs at about 88db efficiency and has very friendly impedance so it works well with both tube and solid state amps. Here's the link to the design. I hope you like it.
http://www.timn8er.com/alegria_audio_rosa_tl.htm
 
I like the looks of this tower with the narrow front and small overall footprint. But while the performance of this design is likely quite pleasing, it can be even better. With a change or two, the overall performance can be improved.

Notice that the frequency response graph tails down about 3 dB below 5-600 Hz. This can be improved with baffle step compensation. BSC would flatten the overall performance.

Furthermore, the roughness in the upper part of the response is caused by interaction between the two woofers (at frequencies beyond one wavelength center to center spacing between these drivers). This can be fixed if the woofers were attenuated by an inductor and the crossover network adjusted to bring the tweeter in a little sooner.

Jim
 
Jim Griffin said:
I like the looks of this tower with the narrow front and small overall footprint. But while the performance of this design is likely quite pleasing, it can be even better. With a change or two, the overall performance can be improved.

Notice that the frequency response graph tails down about 3 dB below 5-600 Hz. This can be improved with baffle step compensation. BSC would flatten the overall performance.

Furthermore, the roughness in the upper part of the response is caused by interaction between the two woofers (at frequencies beyond one wavelength center to center spacing between these drivers). This can be fixed if the woofers were attenuated by an inductor and the crossover network adjusted to bring the tweeter in a little sooner.

Jim

Thanks for your input Jim. I should point out that while I said "in room response" it's actually a quasi-anechoic measurement taken at about 2 meters, therefore, there isn't any room enforcement of the bass response taking place. BSC may or may not improve things depending on placement. As for the crossover, there is certainly room for experimentation. I was going for the "full-range driver" concept with a helper tweeter. The FT207D is no help below 5k but it may be worth trying a 2nd order just above that point to take care of the peaking from the woofers. For those that would like to experiment it may be worth trying a different tweeter. The selection of shielded super-tweeters is very limited, however, there are many un-shielded models to choose from. One that I've been eye-balling is the Hi-Vi radial planer.
 
Tim, I realize that room placement can impact BSC. The rear port would encourage placement away from the back wall. The measurement shown is indicative of the performance at that specific location in the room and I'm pointing out that you could flatten out the overall response via BSC.

Someone asked about specific crossover values. Now any good overall crossover design would start with good measurements on these drivers in this enclosure. Hence, the crossover values would be derived based on the crossover point and the response flatness achievable. A capable crossover design program that uses these measurements would be what I would suggest to derive the values vs. the target performance response.

Jim
 
Jim Griffin said:
Tim, I realize that room placement can impact BSC. The rear port would encourage placement away from the back wall. The measurement shown is indicative of the performance at that specific location in the room and I'm pointing out that you could flatten out the overall response via BSC.

Someone asked about specific crossover values. Now any good overall crossover design would start with good measurements on these drivers in this enclosure. Hence, the crossover values would be derived based on the crossover point and the response flatness achievable. A capable crossover design program that uses these measurements would be what I would suggest to derive the values vs. the target performance response.

Jim

Agreed. Thanks again for your comments. This could be a very good starting point for someone willing to do some tweaking. I may get back to it sometime but it would be interesting to see others give it a shot. We should be seeing a bipole variation soon (I hope).
 
The reason I asked about the crossover frequency that would be required to avoid problems by the interaction of these woofers in close proximity would be to help determine the optimal tweeter to be used. Many are using the WR125 without, or in Tim's case with, a helper tweeter. I would rather use a tweeter where it's dispersion starts to narrow between 4-5khz. I was just wondering weather I will avoid the proximity problem of the woofers and also be able to avoid using the inductor when crossed over in this range.
 
frugal-phile™
Joined 2001
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Here is a bi-pole version that i drew up -- Scott is still building the prototype...

dave
 

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frugal-phile™
Joined 2001
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Just a comment on the WR125 designs i have heard... in each and every case the more larer the role of the tweeter the less engaging the speaker sounded... the sample was limited to some early designs at the last RAW-fest, but i would be very cautious when doing a design that puts anything between the amps & the WR125. You may end up with a speaker that measures flatter, but it may not sound as good... FR is only one facet of making an engaging speaker ... in many a case pursuing flat FR as an end in itself leads to a sterile speaker.

dave
 
Here is a bi-pole version that i drew up -- Scott is still building the prototype...

I'm looking forward to hearing it. This may be the best solution. Despite what some think of bipole speakers I've found them to be extraordinary when done correctly. My RS 40-1197 versions are still in regular use. My wife loves opera and the bipole 40-1197 reproduces the vocals in a very special way.
 
Bipoles

I am with you on that one Tim. I have made two sets of bipoles and absolutely love them both. You designed both of them and they seem to fit just right in my listening room. I really do hope to get into the shop tonight and Sunday to make some phase plugs and at least get a start on the 125st bipoles. I have some lovely lumber to work with. Based on the results I have from your other designs I am going to take a chance and go straight to a finished cabinet. Some how a nice looking cabinet seems to sound better? I hope to have something to take down to Victoria in June for Dave to enjoy.

Hmmmmmm that sounded like a commitment. Better be careful I willhave to come through.

Nuff said for now
 
Hmmmmmmmmmmm
I may never live that one down.
Apparently super short wires are a challenge for some. I had no trouble???
I will use a few more centimeters of wire so those with big mits can get at my handiwork...
I was quite proud of my work.

Nuff said for now
 
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