The foam surround is made from closed cells foam, so there should be no problems with it absorbing humidity, and the shape is pressed at more than 200°C. So I don’t think you have any reason to worry.
Frank
SAL with Emenence Betas 15"
SAL baffle board/s are made up of 5 x 6mm MDF 'laminated' which where CNC machined to provide exact alignment as will the Beta 15" divers. This was achieved via 4 x 5mm holes and drills. I went down this route because 25mm mdf is 'soft in the middle' but by laminating 5 layers this results in a much stiffer (inert) baffle which is for more resistant to 'squeese'. The front face of the baffles will be covered with black acrylic. Fixings with be hidden 'nut serts'
I'm awaiting funds to be become available to purchase the SALs units but the rest of project can move ahead as most of it are favours owed. (Apart from the outlay for the 4 x Emenence bass units.)
More to follow...
SAL baffle board/s are made up of 5 x 6mm MDF 'laminated' which where CNC machined to provide exact alignment as will the Beta 15" divers. This was achieved via 4 x 5mm holes and drills. I went down this route because 25mm mdf is 'soft in the middle' but by laminating 5 layers this results in a much stiffer (inert) baffle which is for more resistant to 'squeese'. The front face of the baffles will be covered with black acrylic. Fixings with be hidden 'nut serts'
I'm awaiting funds to be become available to purchase the SALs units but the rest of project can move ahead as most of it are favours owed. (Apart from the outlay for the 4 x Emenence bass units.)
More to follow...
Attachments
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I am contemplating about a new build of an aperiodic box with a sensitive fullrange driver (Qts around 0.7). Shouldn't be too big, but sufficiently sensitive for a 15W tube amp (sensitivity around 93 dB/W/m). Using a subwoofer with an x-over frequency somewhere in the 50-100 Hz range would be ok (fs below 100 Hz, and sufficient Sd and Xmax to move some air without going far out of linear operation).
The SAL driver is certainly an option. I am also looking at the Supravox 165-2000. The Supravox does away with the whizzer and has very similar specs / Thielle-Small parameters, except that it can move about 2.5 times more air due to its larger Xmax and Sd. It does not cost substantially more than the SAL. I have not heard either the SAL or the Supravox.
Any comments or suggestions for other drivers to consider?
The SAL driver is certainly an option. I am also looking at the Supravox 165-2000. The Supravox does away with the whizzer and has very similar specs / Thielle-Small parameters, except that it can move about 2.5 times more air due to its larger Xmax and Sd. It does not cost substantially more than the SAL. I have not heard either the SAL or the Supravox.
Any comments or suggestions for other drivers to consider?
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That looks great, very nice job... Looking forward to se more.
I did a laminate with 4 psc 19mm MDF, it was heavy as 
but very stiff.
This is how I use my SAL drivers.
I use the SAL drivers in a 2-way system in an open baffle with the dimensions of 150 X 50 X 4 cm. The woofers that I use are SP 382PA from Monaco.
At first, I used a passive x-over filter crossing over at about 115 Hz, with the SAL driver was connected in reverse. I have always had a challenge with x-over’s, there is a lot of factors that must be taking in consideration and it takes a lot of work to get it right. I find that even a small change can have a huge impact, but after many hours of experimenting I got the result that I was looking for.
After a while I was lucky, and got a hold of a First Watt active x-over, from Nelson Pass. This active x-over can be adjusted in so many ways, to insure a good result. This took me a while, but it is easy with this x-over, just a flick of a switch and you have a new setting. I can highly recommend this x-over, it’s easy to use and have a lot of different settings and it made my system sounds even greater.
I use some Antique Sound Lab singled ended (20W) triode based on an 845 tube, mono block to drive the SAL units, the 4 Woofers is driven by to Advance Acoustic Technology (400W) M1000 mono blocks. The X-over is a First Watt B5, CD is a Mark Levinson NO 37, DAC Mark Levinson No 36 and preamp Mark Levinson No 38, plus some other stuff.
Frank
I use the SAL drivers in a 2-way system in an open baffle with the dimensions of 150 X 50 X 4 cm. The woofers that I use are SP 382PA from Monaco.
At first, I used a passive x-over filter crossing over at about 115 Hz, with the SAL driver was connected in reverse. I have always had a challenge with x-over’s, there is a lot of factors that must be taking in consideration and it takes a lot of work to get it right. I find that even a small change can have a huge impact, but after many hours of experimenting I got the result that I was looking for.
After a while I was lucky, and got a hold of a First Watt active x-over, from Nelson Pass. This active x-over can be adjusted in so many ways, to insure a good result. This took me a while, but it is easy with this x-over, just a flick of a switch and you have a new setting. I can highly recommend this x-over, it’s easy to use and have a lot of different settings and it made my system sounds even greater.
I use some Antique Sound Lab singled ended (20W) triode based on an 845 tube, mono block to drive the SAL units, the 4 Woofers is driven by to Advance Acoustic Technology (400W) M1000 mono blocks. The X-over is a First Watt B5, CD is a Mark Levinson NO 37, DAC Mark Levinson No 36 and preamp Mark Levinson No 38, plus some other stuff.
Frank
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Frank,
I was getting ready to cut plywood and decided to measure my own T/S parameters first.
Attached are my impedance plots with different masses added to the cone. Looking at the 6g figures, I'm getting Vas arounf 11 litres. What are you using for piston area?
Thank you,
Mike
I was getting ready to cut plywood and decided to measure my own T/S parameters first.
Attached are my impedance plots with different masses added to the cone. Looking at the 6g figures, I'm getting Vas arounf 11 litres. What are you using for piston area?
Thank you,
Mike
Attachments
Low ply MDF plywood… why not use real plywood? It would be stiffer, lighter and better damped.
dave
Frank,
I was getting ready to cut plywood and decided to measure my own T/S parameters first.
Attached are my impedance plots with different masses added to the cone. Looking at the 6g figures, I'm getting Vas arounf 11 litres. What are you using for piston area?
Thank you,
Mike
Hi Mike,
I use the Dayton measure device, I don’t know Clio Pocket.
But here is the result from my Dayton, se picture below.
Frank
Attachments
Hi Frank,
A couple of things. The piston diameter is noted as 6.5 inches on your screenshot. That will throw-off the calculation. Also, 40g would be way to much added mass for your light cone. I measured both speakers using 6,10, and 15g weights, then calculated Vas by hand to be sure. I'm seeing Vas = 11-13 litres.
The good news is: that would explain why the speaker sounds decent is a smaller box.
I'm working on a little article and hopefully I'll get it out before BAF.
A couple of things. The piston diameter is noted as 6.5 inches on your screenshot. That will throw-off the calculation. Also, 40g would be way to much added mass for your light cone. I measured both speakers using 6,10, and 15g weights, then calculated Vas by hand to be sure. I'm seeing Vas = 11-13 litres.
The good news is: that would explain why the speaker sounds decent is a smaller box.
I'm working on a little article and hopefully I'll get it out before BAF.
Hi Frank,
A couple of things. The piston diameter is noted as 6.5 inches on your screenshot. That will throw-off the calculation. Also, 40g would be way to much added mass for your light cone. I measured both speakers using 6,10, and 15g weights, then calculated Vas by hand to be sure. I'm seeing Vas = 11-13 litres.
The good news is: that would explain why the speaker sounds decent is a smaller box.
I'm working on a little article and hopefully I'll get it out before BAF.
Hi Mike,
I am looking forward to reading your article, will you be posting it on this forum?
Here is why I used 6.5”. The cone diameter is to determent the area of the cone, but the since the cone is not flat but has a conical shape, I calculated the area. And since the air-load affects both the cones, I used the combined area of both the main cone and the wizzer.
If you look at the picture you can see, the area that I used for my calculation.
I agree 40g is a lot, but the Dayton is measure at a higher level of delta fo, so it need a larger weight.
Frank
Attachments
No. The relevant effective area (Sd) for the emitted sound is the plane projection of the cone (at least at low frequencies, remember we're talking Thielle Small here!). Sd does not depend on the 3D shape of the membrane. Otherwise one could simply make a very deep cone to obtain a large Sd in a driver with a small diameter.
Or, in other words: the volume of air that is "moved" by the driver is V = X * Sd, where X is the membrane excursion and Sd = pi * r² is the effective membrane area (r is the membrane diameter plus half of the surround). The volume of air that is "moved" by the driver does not depend on the 3D shape of the membrane.
Yep, I stand corrected. What I was thinking of was the air load on the cone, and this somehow, I got it mixed up with the measurement of Vas. Sorry about that.
I did some new measurements with the new diameter and got Vas to be around 17 L.
Frank
Cool! That means that an aperiodic box does not have to be very large to keep the system Qt close to the driver Qts.
If I were to add a subwoofer (using active filters), what would be a suitable x-over frequency?
I use the First Watt B5 filter from Nelson Pass. The x-over is set to 140 Hz with -12 dB slopes. It is my experience that my preferred x-over frequency is not always the same, it depends on the recording of the music. But usual I end up around 120-160 Hz.
If you are planning to place the woofer away from the speakers, I would go even lower.
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