Help with bipolar Metronome

[prezden]

I have 4 Aura NS3-193-8A left over from some other projects that want a home. I was thinking of building a pair of bi Metronomes with them. Because I'm math challenged and can nor figure out how to calculate the proper specs I have simply scaled Dave at Planet 10's plans for a 3" driver. Could someone kindly take a look at the drawing dimensions and tell me whether it will work or not, or how to improve them.

Thanks 🙂

 

[xrk971]

Did you ever build the Met with the W4 TB Bamboos I designed for you? Or did those end up in the 22 in Cornu?

 

[prezden]

Hi X- They went into the Cornu in the end. That's why I'm thinking of using the 4 Auras.

 

[xrk971]

Ok, I will see what I can cobble up with the four Auras for a bipolar Met sim for you.

 

[prezden]

Thanks X- I really appreciate your help 🙂

 

[xrk971]

Design for Bipole Met with NS3-193's

Prez,
Here is the sim for the design that you posted above with the NS3's. As you can see, there isn't much bass extension given the NS3's deep-bass capabilties. Next plot is the optimized design, third plot is impedance, and fourth plot is cone excursion. All are 1 watt at 1 meter away with speaker located 60 in from a back wall. As you can see, with the bipole design, there is no need for BSC.
The design (in inches) is as follows:

| Enclosure dimensions for Met with NS3-193, all internal dimensions

Width_top = 3.00
Depth_top = 0.75
Height = 40.0
Width_bot =5.00
Depth_bot = 8.50  | Note depth is larger than width to accommodate bipole drivers
Leg_Height = 2.0
Driver_pos = 18.50   | Distance from top  

| Port depth and length
Port_length = 5.50
Port_dia = 2.00

The design produces quite a nice low bass extension for a 3 inch driver, cone movement is well controlled (although you have xmax of 10 mm!). The efficiency isn't so good but with 10 mm of excursion, just pump more watts into it to get a decent volume. These sound like they will be fun to build and should produce a nice balanced output down to high 48 Hz. Not too bad for a 3 inch driver.

 

[prezden]

Thanks X- You help is invaluable! This should be lots of fun 😀

I haven't decided whether to build them out of 5/8" baltic birch ply or a foam core 1/8 ply laminate. The base is quite small. Is there any way to weight it down a bit at the bottom for more stability?

 

[xrk971]

Attach feet to a larger plywood plate, or add weights to underside or inside base.

 

[prezden]

I was thinking a nice thick ceramic tile might work well. Would that have much effect on the sound?

cheers- prez

 

[xrk971]

Tile is perfect, just don't drop it though. Good luck!