Yes they come apart very easy as you discovered already. That does make for easy VC replacement despite being sold as sealed units. I've repaired a few that way using the 25TFF VC asy.
You have to protect the dome with a cap that sits on the inner edge of the ring and using a dremel tool, grind away most of the ring. I run a bead of T7000 adhesive around the outside to seal it back up.
The unit you have with the copper backing is the one I prefer to modify, since it has the copper there as.a shorting ring for the woofer VC.
I've also tried the SB21SDNC and SB26STCN compact domes, which requires trimming the flange to fit in place of the original. The SB26STCN sounds the best here and doesn't break a sweat with its higher sensitivity. The slight WG loading makes it easier to transition to the cone shape.
You have to protect the dome with a cap that sits on the inner edge of the ring and using a dremel tool, grind away most of the ring. I run a bead of T7000 adhesive around the outside to seal it back up.
The unit you have with the copper backing is the one I prefer to modify, since it has the copper there as.a shorting ring for the woofer VC.
I've also tried the SB21SDNC and SB26STCN compact domes, which requires trimming the flange to fit in place of the original. The SB26STCN sounds the best here and doesn't break a sweat with its higher sensitivity. The slight WG loading makes it easier to transition to the cone shape.
Strange that such a venerable company can't figure these things out. Good going!
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Tenson,
Much better polar response compared to the original !
One could expect a smaller diameter tweeter to have better polar response, but yours also appears to have improved the Tymphany Tweeter's polar response too.
By the spec sheets, the Seas tweeter appears to have almost three times the displacement of the Tymphany OX20SC00.
Seas Tweeter- .4mm peak to peak (.2Xmax) x 7cm2 Sd =1.4 cubic centimeters
Tymphany Tweeter- .1 Xmax) x .49cm2 =.049 cubic centimeters
1.4/.049=2.857
The reduction of displacement would amount to just under 9dB less clean output before exceeding Xmax, the Tymphany Tweeter sounding about half as loud before distortion and dynamic compression setting in.
You didn't state the distance, so no comment 😉 .
The woofer should be capable of around 114dB clean at one meter at 200Hz in free space.
With ~6+dB gain over omni provided by the cone "waveguide" the original tweeter at ~2.3kHz crossover would probably be capable of around 112 dB clean.
http://www.baudline.com/erik/bass/xmaxer.html
I probably would not want to trade the better polar pattern for a 9dB reduction in the high frequency output capability- I'd rather the woofer "craps out" before the tweeter.
Art
Thanks for the calcuation Art!
I agree that reducing the tweeter size will limit SPl, I didn't realise the Xmax was half though 🙁
I set the distortion SPL at 90dB 1m using an iPhone with the NIOSH app and white noise from 3000Hz up.
Certainly for my listening levels it is enough and I would trade such a significant improvment in polar respopnse over max SPL every day. However I know some listen a lot louder than me and have bigger rooms. Also one benefit of a large 6" midrange is obviously high SPL. So I do recognise this as a drawback.
How did you fit an SB26STCN inside the Seas VC? Did you extract the dome and motor and make your own back chamber?
I agree that reducing the tweeter size will limit SPl, I didn't realise the Xmax was half though 🙁
I set the distortion SPL at 90dB 1m using an iPhone with the NIOSH app and white noise from 3000Hz up.
Certainly for my listening levels it is enough and I would trade such a significant improvment in polar respopnse over max SPL every day. However I know some listen a lot louder than me and have bigger rooms. Also one benefit of a large 6" midrange is obviously high SPL. So I do recognise this as a drawback.
If you can grab some on axis and maybe 30 degrees measurements that would be really nice to see! Handheld mic say 50cm away should be enough to get the idea since we are interested only >1KHz.
How did you fit an SB26STCN inside the Seas VC? Did you extract the dome and motor and make your own back chamber?
@Tenson I trimmed the flange on the SB26STCN to fit inside the Seas VC cavity. Luckily its not that tall. The trick is mounting in from the back like the old tweeter. I epoxied a small nut under the SB26 rear chamber and trimmed a screw to fit in length. The final tweeter OD happened to line up well with the LF cone. It looks like it belongs there and it can be crossed pretty low thanks to the generous xmax compared to most Seas tweeter elements. There is a small elevation of H2 down low, but its not so noticeable, as it dominates over H3, which is reasonably low.
I have these drivers in their shipping boxes right now under a bunch of stored equipment and will try to get them out of there soon. My garage shop is currently taken up by my little turbo fiesta which is getting an LSD installed, so that needs to be done first before we get into the high 90s temps.
I have another pair of MR18 going into a set of 3 way monitors with SB34NRXL LF drivers. Those wil have wider baffles, so they will need fresh measurments to determine driver location on the baffle for best diffraction behavior. I suspect it won't be that much of an influence on the tweeter FR using the cone for a WG, which tends to lessen diffraction issues.
I have these drivers in their shipping boxes right now under a bunch of stored equipment and will try to get them out of there soon. My garage shop is currently taken up by my little turbo fiesta which is getting an LSD installed, so that needs to be done first before we get into the high 90s temps.
I have another pair of MR18 going into a set of 3 way monitors with SB34NRXL LF drivers. Those wil have wider baffles, so they will need fresh measurments to determine driver location on the baffle for best diffraction behavior. I suspect it won't be that much of an influence on the tweeter FR using the cone for a WG, which tends to lessen diffraction issues.
@wafflesomd Its not so much about continuous SPL, but the dynamic peaks will be limited. 112dB is alot for a small coax, but the MR18 easily will hit those peaks. It would be a shame if the tweeter was the weak link. By substituting the SB26, it may not be an issue as that tweeter will do 110 dB peaks crossed above 2.3k 3rd order and could be crossed lower with the help of a WG.
If you want clean sound at standard listening levels (80-85 dB average) at normal distances in a normal room that will tend to require something like clean 110-115 dB peaks at 1m. Possibly a touch less for a tweeter given typical energy distribution in music but 112 dB is in the right ballpark for peaks.
Still don't think it's a problem at all. I've managed to take pretty much every tweeter I've owned to hearing damage levels and they all live and sound fine, distortion looks fine in measurements. I really think this is just a non-issue for most domestic listening environments. On paper it all makes sense, in practice it's fine. Similar to how to everyone tells you never to take certain tweeters below 2k and yet my experience hasn't really lined up with that take at all.
Must be a tight pucker job trimming this to fit in a 38mm voice coil! Would love to see some photos if you have any?
Can I ask if anybody know is the SICA coax really measures as good on-axis as they show in the manufacturer data?
https://sica.it/prodotto/5-5-c-15-cp/
NVM found this. https://www.diyaudio.com/community/threads/sica-5-and-6-hifi-coaxials-measurements.401394/
https://sica.it/prodotto/5-5-c-15-cp/
NVM found this. https://www.diyaudio.com/community/threads/sica-5-and-6-hifi-coaxials-measurements.401394/
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Unfortunately I cannot disclose anything because of NDA reasons, but I received some nice samples today of a established brand we all know of some possible new coax units.
They seem to have a very smooth high frequency response.
I can't say much about them, except that it looks like that these double or triple surrounds have at least something to do with it.
Well and obviously some additional parts. 🙂
They seem to have a very smooth high frequency response.
I can't say much about them, except that it looks like that these double or triple surrounds have at least something to do with it.
Well and obviously some additional parts. 🙂
Tenson,
As Andy already pointed out, peaks can be +20 over the average levels reported on a dB meter, even when it is set on "fast".
Many people are surprised to find that ordinary noises like hand claps can exceed 120dB peak at one meter, snapping fingers ~116dB. Just dropping a spoon on a plate may be over 125dB peak at one meter!
Though most recordings compress peaks, there are still some that don't, and on those, a limited dynamic range can reduce the realism.
As a dynamic range example, using a little toy 6” (150mm) drum one meter from the microphone in a 4x4meter room, with a noise floor of 40-50dB(C)Fast (Interstate Highway 75 outside the window..), the eight drum hits rise from 68 to 104dBC(fast), while the peaks range from 75 to 122dB(Z).
This drum would sound balanced with an acoustic guitar played at average level in a living room.
The LZpeak at 122dB actually may have been less than actual- the mic used clips around that level.
Certainly not a Grammy winning performance, but illustrates a “drum solo” with a dynamic range of 80dB or more, with peaks above 120dB 😉
Art
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Have a look at @vineethkumar01 's measurements:
https://www.diyaudio.com/community/threads/a-3-way-design-study.376620/post-7334531
I think he used 3d-printed enclosures.
And here:
https://www.diyaudio.com/community/threads/a-3-way-design-study.376620/post-7339708
(I like your coaxial very much, by the way!)
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It would be interesting to see how the
And nice work Tension. It would be interesting to see how the performance would be using the OT19NC too.
This is exciting!
And nice work Tension. It would be interesting to see how the performance would be using the OT19NC too.
@weltersys Art (and everyone really) as a reference for my listening levels I played Welcome to the Pleasure Dome (Frankie Goes To Hollywood) at what I would consider a loud listening level. I also consider this quite a dynamic track among my usual listening repertoire. I would very rarely listen to anything louder. I'm not making a counter-point to Art's earlier post BTW, just adding for more clarity.
I saw a peak of 102 dB at just one point in the track, the rest was peaking around 98 dB @ 1 m from the right speaker.
Interestingly, I only observed about a 3 dB drop at my listening position 3 m from the speakers. I guess this is due to moving equally between both speakers rather than near only one, and the room not being an anechoic chamber of course.
(and yes, your hearing will be affected if this level is maintained for greater than 30 min on a regular basis)
EDIT:
According to this calculator I was probably hitting just on max what the tweeter can do at 2.3 KHz. 99dB - 6dB for the xover filter = 93dB. Then again... not anechoic. Probably more suited to a 3 KHz xover.
I saw a peak of 102 dB at just one point in the track, the rest was peaking around 98 dB @ 1 m from the right speaker.
Interestingly, I only observed about a 3 dB drop at my listening position 3 m from the speakers. I guess this is due to moving equally between both speakers rather than near only one, and the room not being an anechoic chamber of course.
(and yes, your hearing will be affected if this level is maintained for greater than 30 min on a regular basis)
EDIT:
According to this calculator I was probably hitting just on max what the tweeter can do at 2.3 KHz. 99dB - 6dB for the xover filter = 93dB. Then again... not anechoic. Probably more suited to a 3 KHz xover.
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