Let's take a trip back in time. I'm glad I'm a "pack rat" and save lots of speaker measurements etc. So, Curt and I started the Statements development in 2006. We had listened to a design using Visiton (I think) titanium drivers and liked the sound. We didn't like the price so we bought a TB W4-1337SA for testing. Based on Curt's testing it came in at around .1% 3rd harmonic distortion in the 400-4000 Hz range that we'd be using them in.
They worked very well and the Statements sounded great. However, as my audio tastes evolved I found myself hearing a slight metalic sound on some recordings which prompted us to go on the search for a hard cone paper driver. The NE123W's won the search and the Statements II were born. It's a great driver and we're sorry it's no longer available.
As new designs popped into my head and SB grew in the market and tested extremely well, we just had to use them. The SB CAC's drivers have become my favorite. Extremely smooth with exceptional clarity, detail and super low distortion. They are in our new Anthology II design that'll "officially" be published at Iowa DIY this fall. I also used them as the mids in the Traveler's design.
I'm attaching distortion testing of the TB W4-1337SA since there was discussion about them. This is from long ago...
Jim
Troels Gravsen lately found 3" for midrange in classic 3 ways was a little too weak relative to the emisse surface (Sd), and he swaped to 5".
C. Campbell maybe saw Ne123W being more a 4" as week as well, and it was doubled for MTM and for a littlier 3 ways he used te 5.25" NE 149W (Micro Statment, Finalist Monitor, Finalist 3 ways)
I made a 8" + 3" + 0.75" but perhaps a little 3 ways is becoming only interresting VS a 2 ways from 10" (or 8") + 5" + 1" ?
C. Campbell maybe saw Ne123W being more a 4" as week as well, and it was doubled for MTM and for a littlier 3 ways he used te 5.25" NE 149W (Micro Statment, Finalist Monitor, Finalist 3 ways)
I made a 8" + 3" + 0.75" but perhaps a little 3 ways is becoming only interresting VS a 2 ways from 10" (or 8") + 5" + 1" ?
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I would not use anything smaller than a single 5" driver as a mid or mid woofer. However MTM style speakers can easily use 4" drivers if selected properly.
The plus of the NE123's was they were exact drop in's size wise to replace the W4-1337's in the original Statements design so it was a no brainer for us.
Jim
The plus of the NE123's was they were exact drop in's size wise to replace the W4-1337's in the original Statements design so it was a no brainer for us.
Jim
Of topic : I am trying to make a MTM with two NE149W despite it is not easy due to the frequency curve behavior and increased center to center.
Some noticed Sd in most homes when talking about midrange should be 6" to 8" surface... I do not have any idea as I tried to find two NE123W per channel but finally just found four NE149W-08. Which is of course way more difficult than 2 littlier drivers for MTM , non saying the NE149W is less flat than the NE123W.
Wonder how it will sound with the tunnel load of the Finalist design but MTM.
Some noticed Sd in most homes when talking about midrange should be 6" to 8" surface... I do not have any idea as I tried to find two NE123W per channel but finally just found four NE149W-08. Which is of course way more difficult than 2 littlier drivers for MTM , non saying the NE149W is less flat than the NE123W.
Wonder how it will sound with the tunnel load of the Finalist design but MTM.
Just circling back on this. When you say tapered bevel, is this something that you had in mind?
How does one decide on where the taper starts and at what angle should it be?
In there a simulator that does it?
Intuitively I would say start a far away from the tweeter as practically possible, and go as close to the tweeter dome as practicality possible. And the facet should be 45 degrees. But intuition is fraught with danger.
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Yes that is the general idea of a tapered bevel.
Heissmann did a study where they showed that anything from 30 degree to 45 degree was a good chamfer (bevel). This is relative to the baffle, so 0 degree no bevel at all.
https://heissmann-acoustics.de/en/schraege-fasen/
I tend to use 33 to 35 degrees relative to the baffle.
The taper angle is mostly driven by the geometry of the cabinet. If the box was significantly wider than the woofer, we would not need to taper the bevel.
I did a study where I showed that a tapered bevel can be simulated in VituixCad as if it were a straight chamfer. I will try to find the link
Here are some recent examples I have done.
Heissmann did a study where they showed that anything from 30 degree to 45 degree was a good chamfer (bevel). This is relative to the baffle, so 0 degree no bevel at all.
https://heissmann-acoustics.de/en/schraege-fasen/
I tend to use 33 to 35 degrees relative to the baffle.
The taper angle is mostly driven by the geometry of the cabinet. If the box was significantly wider than the woofer, we would not need to taper the bevel.
I did a study where I showed that a tapered bevel can be simulated in VituixCad as if it were a straight chamfer. I will try to find the link
Here are some recent examples I have done.
Hi Mike,
Curt and I will both be there. Please come up and introduce yourself. We look forward to meeting you!
Jim
@hifijim There has been quite some studies done on this.
Even by a German magazine Hobby Hifi over two decades ago.
But I recall quite some more from 10-15 years ago.
If you're really interested I can dig them up (really have to search though).
From an acoustic point of view, you just have to create a smooth transition to prevent any acoustic impedance jumps.
So a big round over blend will often be good as well.
Tapered bevels do have a bit of a harsher transition, although you still can get nice results with them
Even by a German magazine Hobby Hifi over two decades ago.
But I recall quite some more from 10-15 years ago.
If you're really interested I can dig them up (really have to search though).
From an acoustic point of view, you just have to create a smooth transition to prevent any acoustic impedance jumps.
So a big round over blend will often be good as well.
Tapered bevels do have a bit of a harsher transition, although you still can get nice results with them
Here is the link to the study I did. I built some prototypes from XPS foam board to see how tapered bevels compared to simulation.
https://www.diyaudio.com/community/...ations-with-ideal-drivers.380658/post-6986539
Posts 211 - 225 show how the measured data compares to VituixCad diffraction simulation.
The final conclusion of this is
j.
Ctc spacing at 1.2 times the wavelength at the XO point can provide a smoother power response. If you look at Jim's posts you should find the rationale. Vituixcad author I believe has documented this. This is contrary to the 'pack as close together as possible ' but measurements prove otherwise. I'm not sure what crossover topologies this spacing is best suited for. The compromise is vertical off axis response but again I don't know if equal or less in overall in room response performance
Here is a concept sketch for this project. The design is not finalized, but things are coming together. I have firmly decided on the Dayton RS270-4. The SB29SDAC has the right combination of directivity and low-crossover capability, and the price is within budget. I have not decided on the midrange driver yet, but the two leading candidates are Dayton RS125 and SB15NBAC30.
j.
I think these guys are comfortable with cutting tapered bevels because they know I have done it, and I would be available to help them do it... Its not hard, but it seems intimidating until you do it the first time.
j.
Cutting tapered bezels intimidates me every time, it is pretty much the the last machining step and the chances of turning an enclosure into another pile of scrap is a very real possibility.
I would suggest the RS270P-4 with the paper cone instead of the RS270-4 metal cone. You get another 2db and much smoother breakup. I just used it little brother the RS170P-4 and I'm quite happy with it.
I would suggest the RS270P-4 with the paper cone instead of the RS270-4 metal cone. You get another 2db and much smoother breakup. I just used it little brother the RS170P-4 and I'm quite happy with it.
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Re: RS125 vs SB15NBAC
RS125- wider dispersion, good looks (consistent with R270), smooth top end roll off.
SB15NBAC-narrower dispersion but more Sd, lower distortion and potentially better (particularly if you extend the speaker with dual RS270!),
Tough call!
Either way, I think you’re going to have lots of builders, I think for this high performance, high value, active hybrid.
For your research pleasure:
https://www.divine-audio.com/
RS125- wider dispersion, good looks (consistent with R270), smooth top end roll off.
SB15NBAC-narrower dispersion but more Sd, lower distortion and potentially better (particularly if you extend the speaker with dual RS270!),
Tough call!
Either way, I think you’re going to have lots of builders, I think for this high performance, high value, active hybrid.
For your research pleasure:
https://www.divine-audio.com/