Quiet piggy. 
11 Likes
Amusingly (to me), ChatGPT pulled the inductance figure from the 3B driver rather than the 3. Doesn’t make any difference to the output in this instance, but it does go to show how staggeringly useless AI shit is. You always need to check, so does it really save any time?
1 Like
Love the pork, the pork needs love.
OK, the enclosure isn’t that easy to get at right now but:
Aperture front horn
Vent for back horn starts at about 60mm up on the cabinet
Vent is about 100mm wide
And 60mm high (Missed that pic)
This is one of the side mounting bolt holes
1 Like
1 Like
Here’s some BD5 pics
Looking at the foam in comparison with a 5mm O ring - this appears overkill but the cone is very free so maybe under pressure it would move up and down a fair bit?
Underside:
Haha 2026’s forum tagline sorted
14 Likes
You found the Mitutoyos
1 Like
Haha indeed - bastard things think they can hide from lord piggly!
OK I don’t think there’s much we can do until I have a helmet chamber in my hands and can take measurements. Then I should be able to make something within a few days. Here’s how I see it working:
1 - mounting the driver to the baffle
You’ll need to mount the driver directly onto the horizontal baffle. You’ll need to drill 4 holes for this and I suggest to use winged t-nuts and m6 bolts (the mounting holes are 7mm). I’ll print a pair of 5mm TPU gaskets.
2 - mounting the helmet chamber to the baffle
The helmet chamber will use 4 connections to the horizontal baffle - the 2 existing vertical threads, and 2 more where you’ll need to drill again as above. There will be a 1mm TPU gasket.
3 - mounting the helmet chamber to the horn
The chamber vents to the green felt gusset. I’ll print a gasket for this. I think that I’ll make the helmet chamber so it should be fairly snug, and make gaskets of various thicknesses.
I’ll make a slot where a nut can be dropped in, so a machine screw can come from the outside and clamp the chamber to the start of the horn.
Sound good?
1 Like
With S1 now measured at 600 (6cm x 10cm), the response (with Vtc 500) is now this:
Increasing Vtc to 1000:
And to 3000, which is about what the Lowther one has:
Not sure I’m getting wildly excited about the differences. I imagine that 1000 is the about smallest I could reasonably make; even that would have to follow the contour of the back of the driver fairly closely.
The thing to do is model the response that the original driver, with original throat chamber gives into the horn, and try to match it.
You can use offset driver mode to model both front and rear horns as a system.
I’ve just started printing a second TPU gasket and it occurs to me that the interface from helmet chamber to horn is probably best done using a neoprene gasket. You can buy neoprene sheets in varying thicknesses, and since the shape is a simple rectangle within a rectangle, it should be easy to cut wit a craft knife.
And now I’ve ventured down an internet rabbit hole of laser-cut rubber and think that that would be a great idea for the other gaskets. Maybe that could be stage 2 after proving the concept with 3d printed ones?
Remember, you can always shrink the throat chamber. Enlarging it is harder 
I’ll look at the offset driver thing. Do you fancy having a bash at HornResp though? I’ve not used it for anything like this, and I really don’t have a good feel for how it works.
I agree the principle of matching the Lowther response, although I can’t find much on the PM3s. I imagine that the data on their modern drivers will be very different from a proper oldie like this.
Agree also on the large chamber idea. Maybe make it large and it can be stuffed with Blu-Tac until it sounds/measures best? I wonder whether the best idea will be to do 2 different sizes and they can be swapped?
If you post some info on the horn flare parameters (both horns), and driver TS parameters (both drivers), I can take a look, but not today…
2 Likes
Using the x2 existing threads vertically is no problem - The two horizontal and much bigger bolts that go through the sides of the back of the cab clamping the base of the pan next to the rectangular exhaust to the rear horn chamber are quite critical
- Again with the Lowther re done by Lowther these bolts did not align (Thanks to the thickness of the 10mm protruding new shit they put on it. In short the thickness of the BD5 frame and the 5mm gasket will need to be accounted for when working out A) where the helmet meets the LF mouth B the bolt position (Both will be in the new pan 12mm lower to account for the 'raising of the BD5 mount - Pan will be sent today -
