Here we go, I used 11 mm OSB ( I am trying out an other prototype that might look retro in OSB). Not to keen on the material rough and flaky as it is. I had the sides cut to size and then just 6 strips 180mm wide and about 700 mm long. I used a pull saw for the cutting of the various smaller parts that all are 180 mm wide.
I used white wood glue, plenty of it to seal the various parts. Late in the evening I discovered that I had no window sealing strips, I cut up some wider sealing strips/insulation. My luck as the glue sticks way better than window sealing strips. That corner clamp is a handly little thing!
I used clamps to attach the side, I will get some more clamps from the garage before I start doing all the measurements. But that will not be today, but soon
The plan for measurements are as follows:
Impedance: (Dayton Woofer Tester )
Frequency response: (Omni Mic diver near field and horn opening)
Conditions: totaly empty, damping material as Kings article. Variants with various compartments with damping material removed.
I used white wood glue, plenty of it to seal the various parts. Late in the evening I discovered that I had no window sealing strips, I cut up some wider sealing strips/insulation. My luck as the glue sticks way better than window sealing strips. That corner clamp is a handly little thing!
I used clamps to attach the side, I will get some more clamps from the garage before I start doing all the measurements. But that will not be today, but soon
The plan for measurements are as follows:
Impedance: (Dayton Woofer Tester )
Frequency response: (Omni Mic diver near field and horn opening)
Conditions: totaly empty, damping material as Kings article. Variants with various compartments with damping material removed.
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Nice prototype DrBoar! I dig the top-mounted terminals, like I did on my little BLH for FF85WK - function before form! I'll be looking forward to your measurements.
FF85WK back load horn - YouTube
IG
I'll be looking forward to your measurements.FF85WK back load horn - YouTube
IG
Its a Tangband 4", that I bought back in 2002, look at page 2 in this thread for specifications, measured, official and compared to Kings Fostex driver. It is a pretty good match apart from surface area that is substantially smaller. Fr was way higher than specified out of the box but Rammstein really loud for hours on end have helped to both lower the Fr of the drivers and for me to discover many more good songs apart from Du Hast
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Dr Boar,
OK, so the trick to quick break-in of drivers is to play Rammstein - would other metal bands work ? How loud do you play it - b'cuz around my house, I would have to put it in a sealed cooler with pillows and foam to absorb all the sound from breaking in. Otherwise, I do it slow and gentle with normal jazz or pop for days on end - which is not a problem.
OK, so the trick to quick break-in of drivers is to play Rammstein - would other metal bands work
? How loud do you play it - b'cuz around my house, I would have to put it in a sealed cooler with pillows and foam to absorb all the sound from breaking in. Otherwise, I do it slow and gentle with normal jazz or pop for days on end - which is not a problem.
I play so loud that the cone move several mm, for some drivers I used ear protectors before entering the room. So I start the music then leave the house!
Today I have made impedance measurements and taken pictures
1. No damping
2. Damping as article
3-5 variants of removed damping.
At the end I discovered that it easy to get leaks as the newer clamps had to have their plastic feet removed to reach over the boxes and they can slide around a bit. I edited all the images but then Photobucket or my computer did something odd with the series of images so all the .jpg are now identical?
The impedance peaks are hardly changed by having the horn in a corner or in mid air. So tomorrow I will redo all the impedance measurements with the horn lying down on a flat surface with a gravity seal assisted by two 15" drivers to add some mass.
Today I have made impedance measurements and taken pictures
1. No damping
2. Damping as article
3-5 variants of removed damping.
At the end I discovered that it easy to get leaks as the newer clamps had to have their plastic feet removed to reach over the boxes and they can slide around a bit. I edited all the images but then Photobucket or my computer did something odd with the series of images so all the .jpg are now identical?
The impedance peaks are hardly changed by having the horn in a corner or in mid air. So tomorrow I will redo all the impedance measurements with the horn lying down on a flat surface with a gravity seal assisted by two 15" drivers to add some mass.
Measurements!
As impedance curves with the horn in a corner, freestanding or sideways on a table overlap I have done all measurement using the table as a side wall and with me as weight. Using the cabinet alone or just a 15" driver as a weight was not enough. When using the horn freestanding and clamps great care has to be taken to make sure that everything is properly sealed.
The fluffy things are at 3x 25g(chamber, IPA and P3) one of 15 g (P2) and 2,6g (p1)
The IPA should have had 23 g but I did not think about using a marker on that one to keep it apart from the two 25 g ones. My kitchen scale goes all the way up to 5000 g I have not tried to calibrate it to see how accurate it is. As 1 ml= 1gram (and 1cc) it is not hard to do.
Just to make clear what I mean by chamber, IHR and P1-P3
Then for the impedance measurements. First out is with no damping what so ever. This curve is then in as a green reference curve in the other measurements
Adding 25 gram of fibers to the driver chamber
And then 25 g to the IHR as well
And some few grams in P1
15g in P2
fully stuffed
As impedance curves with the horn in a corner, freestanding or sideways on a table overlap I have done all measurement using the table as a side wall and with me as weight. Using the cabinet alone or just a 15" driver as a weight was not enough. When using the horn freestanding and clamps great care has to be taken to make sure that everything is properly sealed.
The fluffy things are at 3x 25g(chamber, IPA and P3) one of 15 g (P2) and 2,6g (p1)
The IPA should have had 23 g but I did not think about using a marker on that one to keep it apart from the two 25 g ones. My kitchen scale goes all the way up to 5000 g I have not tried to calibrate it to see how accurate it is. As 1 ml= 1gram (and 1cc) it is not hard to do.
Just to make clear what I mean by chamber, IHR and P1-P3
Then for the impedance measurements. First out is with no damping what so ever. This curve is then in as a green reference curve in the other measurements
Adding 25 gram of fibers to the driver chamber
And then 25 g to the IHR as well
And some few grams in P1
15g in P2
fully stuffed
Regarding density I ment water
These are the measurements for a full damping of the pipe
I run a impedance sweep before before measurements to make sure that the box is properly sealed.
Driver 10 on axis
Increasing the distance to 30-50 cm increase the output above 10 kHz, the 6 kHz peak remain. Note the dip in the driver around 75 Hz
Pipe output in the middle of the opening
With the horn in a corner at 1 m in front of the driver
The clutter around is reflected in the poor water fall response
In Kings simulation if I read it correctly the pipe output has - 6dB points at 40 and 200 Hz, I get more like 65-150 Hz and about 12 dB down at 40 and 200 Hz.
Time to investigate what that IHR is doing and the damping material in the pipe
These are the measurements for a full damping of the pipe
I run a impedance sweep before before measurements to make sure that the box is properly sealed.
Driver 10 on axis
Increasing the distance to 30-50 cm increase the output above 10 kHz, the 6 kHz peak remain. Note the dip in the driver around 75 Hz
Pipe output in the middle of the opening
With the horn in a corner at 1 m in front of the driver
The clutter around is reflected in the poor water fall response
In Kings simulation if I read it correctly the pipe output has - 6dB points at 40 and 200 Hz, I get more like 65-150 Hz and about 12 dB down at 40 and 200 Hz.
Time to investigate what that IHR is doing and the damping material in the pipe
Waddya know, water is ~1g/cc - probably something I've known at some point, thanks for specifying!
Overall response is quite decent IMO. You're getting the typical BLH suckout right below 200Hz. Naturally, the horn's upper cutoff rolls-off quite smoothly with all the damping, it will be interesting to see if that's what you find sounds best in the end.
IG
Overall response is quite decent IMO. You're getting the typical BLH suckout right below 200Hz. Naturally, the horn's upper cutoff rolls-off quite smoothly with all the damping, it will be interesting to see if that's what you find sounds best in the end.
IG
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