Big hello with Christmas 2023. Scan Speak project. 🙂
2.5 way tapered transmission line with Scan Speak units. Always wanted to build something with legendary 18W Revelators and this year two pairs landed in my workshop. One pair is from 2022 and bought 6 months ago. One pair produced in 2023 I bought now as a Christmas present from me to myself. All four look the same and I hope they will sing the same. Illuminators D3004/6600 will come in January and be installed in augerpro's waveguide to complement the package.
Why TL? Because I would like to hear that deep dry bass 😎 and I don't want to build another too small 6+1 inch speaker whistling around 50 Hz through its too small port. I want to build something bigger and different. That's why double dose of 18Ws as a bare minimum with Sd surface of 10 inch driver. Later to overstuff it and test how too big aperiodic / sealed box with low Q would sound and would I like it or not - for my future projects.
Idea is for a longer time in my head, I went through Onley, Bailey, Augspurger and MJK and all available here on diyA. I have come to the level where I can produce TL in Hornresp in a few seconds 🙂 and it was good course about behaviour, changes and important parameters in Tls. MJK made nice writings recently as an extension of his work from two decades ago. He is trying to demistify and make fair comparisons to various bass enclosures. It was a good guide for complete TL design from scratch.
So, few goals:
1. 2.5 way tapered TL towers with 2x SS 18W/8531G00 plus D3004/6600 in waveguide;
2. Internal volume around ~ 60 liters plus minus 3 dB;
3. Tuning not below 30 Hz and especially not above 35 Hz;
4. Bass quality above quantity and lowest minus 3dB point;
5. 5:1 taper as an optimum between length, width of the box, physical buildable size, Start and End cross sections and slow blow mouth velocity;
6. Low diffraction cabinet with thick rounded front baffle (I have CNC router) for directivity control of midbass for better match with waveguide;
7. Additional external curved sides to make elegant teardrop-ish cabinet, glued with CLD layer;
8. Simple minimal audiophile passive crossover 😍;
9.. High end sound of course;
10. Sexy look blink blink;
In next few posts drivers measurements with DATS, calculations of geometry according to MJK methodology and Hornresp simulations...
Goal for this Christmas vacation time is to cut and build-with-screws test boxes as a hardest part. If they pass initial measurements then will be glued and further developed into something serious...
2.5 way tapered transmission line with Scan Speak units. Always wanted to build something with legendary 18W Revelators and this year two pairs landed in my workshop. One pair is from 2022 and bought 6 months ago. One pair produced in 2023 I bought now as a Christmas present from me to myself. All four look the same and I hope they will sing the same. Illuminators D3004/6600 will come in January and be installed in augerpro's waveguide to complement the package.
Why TL? Because I would like to hear that deep dry bass 😎 and I don't want to build another too small 6+1 inch speaker whistling around 50 Hz through its too small port. I want to build something bigger and different. That's why double dose of 18Ws as a bare minimum with Sd surface of 10 inch driver. Later to overstuff it and test how too big aperiodic / sealed box with low Q would sound and would I like it or not - for my future projects.
Idea is for a longer time in my head, I went through Onley, Bailey, Augspurger and MJK and all available here on diyA. I have come to the level where I can produce TL in Hornresp in a few seconds 🙂 and it was good course about behaviour, changes and important parameters in Tls. MJK made nice writings recently as an extension of his work from two decades ago. He is trying to demistify and make fair comparisons to various bass enclosures. It was a good guide for complete TL design from scratch.
So, few goals:
1. 2.5 way tapered TL towers with 2x SS 18W/8531G00 plus D3004/6600 in waveguide;
2. Internal volume around ~ 60 liters plus minus 3 dB;
3. Tuning not below 30 Hz and especially not above 35 Hz;
4. Bass quality above quantity and lowest minus 3dB point;
5. 5:1 taper as an optimum between length, width of the box, physical buildable size, Start and End cross sections and slow blow mouth velocity;
6. Low diffraction cabinet with thick rounded front baffle (I have CNC router) for directivity control of midbass for better match with waveguide;
7. Additional external curved sides to make elegant teardrop-ish cabinet, glued with CLD layer;
8. Simple minimal audiophile passive crossover 😍;
9.. High end sound of course;
10. Sexy look blink blink;
In next few posts drivers measurements with DATS, calculations of geometry according to MJK methodology and Hornresp simulations...
Goal for this Christmas vacation time is to cut and build-with-screws test boxes as a hardest part. If they pass initial measurements then will be glued and further developed into something serious...
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Variations of TL tunnels for same tuning frequency of 35 Hz (actually ~ 33 Hz - difference between physical and effective length) with similar volumes but different taper ratios. Bigger taper, shorter line, coefficients 0.80, 0,71 and 0,62 from MJK tables...
After numerous variations and simulations I decided for 5 : 1 as an optimum.
After numerous variations and simulations I decided for 5 : 1 as an optimum.
Non-tapered 1:1 TLine and tapered 10:1 TLine responses. It is easily seen how taper moves all resonant modes to the right where it will be easier to damp them out with stuffing. Such a big taper moves 5/4 WL and 7/4 WL modes more than 100 Hz toward higher frequencies and also greatly reduces all higher modes. But 10:1 also means very small terminus which I don't like and shape of the box which would not be floorstander of good proportions. It is also problematic to instal drivers and tweeter to the proper listening height.
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This is response of 5:1 tapered line which I would like to build. This is for 63 litres volume and maybe I increase this a little bit, but we will see what T/S parameters of 18W will be like - becuse they are off in comparison to datasheet. Qes and respectively Qt are higher and Vas is lower.
Here shown is one critical parameter...driver offset down the line. Good offset completely removes 3/4 WL resonant mode and if you miss for only 1-2 cm up or down resonance wiggle develops very quickly. So it is important to install drivers in sweetspot. Test box will have one fold, two drivers instead of one and will be different in geometry than this perfect simulated shape. I will make test front baffle to be able to "slide it" a little bit up or down and see with measurements where will be perfect offset position.
Here shown is one critical parameter...driver offset down the line. Good offset completely removes 3/4 WL resonant mode and if you miss for only 1-2 cm up or down resonance wiggle develops very quickly. So it is important to install drivers in sweetspot. Test box will have one fold, two drivers instead of one and will be different in geometry than this perfect simulated shape. I will make test front baffle to be able to "slide it" a little bit up or down and see with measurements where will be perfect offset position.
Quick check with DATS...bunch of cold units, from the box. Satoris didn't play for 6 months, fullrangers for 3 months and Revelators didn't play at all.
Measurements taken in a way that I press them against surface with hand. Proper clamping is necessary that wiggles around main impedance bump go away. These are lighweight drivers and sweep from lowest frequencies produce reation forces. I will give now few days of burn in and warm room to Scan Speaks, then I measure them more serious clamped to baffle and in vertical position.
Lower picture all four units, pair from 2022 has higher Fs and pair from 2023 lower. I guess, longer they don't play, stiffer is the suspension...Resonance bump around 800 Hz easily seen like in datasheet, nothing critical in break up region above 2 kHz, that is nice...Qes and Qts much higher...
Satori brothers...of course that I will try these also in TL... 😀
Bump around 1400 Hz - cone edge resonance, then mild resonances on 3.5, 6.5 and 12 kHz....controlled impedance rise toward higher frequencies, like in other measurements on internet...
Four fullrangers SB20FRPC30-8
Measurements taken in a way that I press them against surface with hand. Proper clamping is necessary that wiggles around main impedance bump go away. These are lighweight drivers and sweep from lowest frequencies produce reation forces. I will give now few days of burn in and warm room to Scan Speaks, then I measure them more serious clamped to baffle and in vertical position.
Lower picture all four units, pair from 2022 has higher Fs and pair from 2023 lower. I guess, longer they don't play, stiffer is the suspension...Resonance bump around 800 Hz easily seen like in datasheet, nothing critical in break up region above 2 kHz, that is nice...Qes and Qts much higher...
Satori brothers...of course that I will try these also in TL... 😀
Bump around 1400 Hz - cone edge resonance, then mild resonances on 3.5, 6.5 and 12 kHz....controlled impedance rise toward higher frequencies, like in other measurements on internet...
Four fullrangers SB20FRPC30-8
Conclusion is that I have confidence in DATS, just need to fix drivers more properly.
We continue after Christmas...
Cheers!
We continue after Christmas...
Cheers!
Happy Holidaze and all that jive! 😎👍
Based on the original reflex patent, design in theory is based on a vent area (Av) = driver effective piston area (Sd), which IME allows plenty of pipe length to work with.
Based on the original reflex patent, design in theory is based on a vent area (Av) = driver effective piston area (Sd), which IME allows plenty of pipe length to work with.
This is the 3rd time I've seen recent Scan woofers with Qes and Qts DATS measurements over 50% off from datasheet. Are their published specs just a fantasy?
Kind of drugged up, so maybe 'can't see the forest for the trees', but how can it measure T/S accurately without a piston diameter or otherwise added mass?
T/S Explained
T/S Equations and how each one affects the others
T/S Explained
T/S Equations and how each one affects the others
Just a quick Christmas sweep to see where are Fs of drivers...after burn in and screwing them to baffle I make Vas measurements with added mass...
Thanks for the paper - it is nice to read audio language from 1930. 🙂
Thanks for the paper - it is nice to read audio language from 1930. 🙂
DATS does an initial set (it keys off the generated impedance curve); you can then enter the piston diameter & have the choice of four different methods to derive VAS -the two usual suspects of known volume test box, added mass, and the two mathematical derivations keyed from entered known SPL or known Mmd. I actually use known Mmd a lot of the time & in most cases, it's as accurate as anything else -certainly within a reasonable comparative tolerance.
DATS does measure at low drive voltage, so Q can end up on the high side & Vas on the low, especially if the suspension etc. is also a bit stiff with new units. That's a fairly consistent theme when you compare to measures taken with Clio, LMS or similar. But it's generally accurate for those levels.
Thanks for input, I'm far away from being laboratory measurement expert, but I will try my best... In DATS v2 white paper is written that it is possible to change signal level. I have DATS v3 and can't find where should I be able to change level...If somebody knows...
Sure. If you go into the Oscilloscope mode, at the bottom of the left-hand click-menu, you'll find a box 'Z Sweep Amplitude', which allows you to alter the drive level -this applies to the Impedance Analyser & T/S measurement mode also. On paper the maximum 11.4dBu setting is equivalent to 2.878v, although as a USB device & IIRC a constant current source, to the best of my knowledge it isn't outputting that so much as interpolating it. Whatever the details though, that's the highest drive setting option available, so aside from doing some of its linearity & rub & buzz consistency testing (not without interest) I tend to default to it for T/S etc. measures since it's probably more representative of how the driver will be behaving under real-world conditions. YMMV as always of course. 😉
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OK, default level in DATS was set to 9 dBu, which would be 2.183 V. That's fair. 🙂
Will try 3 levels for every unit to observe trends...I return with results for a few days...
Will try 3 levels for every unit to observe trends...I return with results for a few days...
I have DATs as well, I've found older scan spec sheets say from 15-20 or so years don't match up well but later are closer.
I always get much lower inductance on bass and mids so much so I thought my unit was defective, but measuring some
Tweeters I get similar results to the spec sheet.
I measured a few 15W revelators from Scan and they did not match the spec but we're similar to online measurements
from others so I tend to believe the DATs data.
Scan Speak Tech Notes
"Measurement of Thiele Small parameters can lead to quite a bit of discussion within the loudspeaker community. " 😀👍
And also they measure response on 6 x 7 m baffle (wall I guess) with 320 liters closed box behind the drivers. Why they miss to write correct Fs in almost all datasheets is a mistery to me. But OK, it was nice reading.
"Measurement of Thiele Small parameters can lead to quite a bit of discussion within the loudspeaker community. " 😀👍
And also they measure response on 6 x 7 m baffle (wall I guess) with 320 liters closed box behind the drivers. Why they miss to write correct Fs in almost all datasheets is a mistery to me. But OK, it was nice reading.
It would be, but whether that's the actual output voltage or an extrapolation thereof, I don't know off-hand. Which seems to be as good a reason as any for me to check it, as I've got the calibrated gear here to do just that, and there's been a question about this floating about for some time, on & off.
Edit: TBH, I suspect you'll find little difference, except potentially at the extremes of what it can do, although I have know it happen a few times.
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I'm thinking about box look and shape how to mount drivers. Idea is to produce complately rounded front baffle which will without disruptions continue to side walls...minimum radius in corners would be 50 mm. We learned that louspeaker enclosures are waveguides and shape should help to control directiviy under tweeter waveguide frequencies...
Something like combination of these two. I really like the shape of this KEF QX. It just needs extension of front baffle like this Magico M3 to become nicely teardrop-ish...
Top view with 18W in it's place...to peak out on sides a little bit and to be flushed a little bit in the middle. That would also look nice I think.
Something like combination of these two. I really like the shape of this KEF QX. It just needs extension of front baffle like this Magico M3 to become nicely teardrop-ish...
Top view with 18W in it's place...to peak out on sides a little bit and to be flushed a little bit in the middle. That would also look nice I think.
Developing the box "around the tunnel". With augerpro's 25mm deep waveguide tweet and mid are already aligned on vertical baffle. But speaker would look really nice tilted few degrees back. Then this difference should be compensated If I decide to make crossover for tilted version...
Nothing wthout test box and first measurements....
Nothing wthout test box and first measurements....
Maximum box height 110 cm because 120 cm is max what is going into my CNC table. Will be built from 19 mm MDF mostly, but finished speaker will have double sides and be very thick. Brace in the middle is 30 mm. This upper rounded part on top I will make laminated to follow the shape. Bottom will be removable for easier access and stuffing and will hold crossover to be out of vibrations from the box...