Small 2-way speakers with linear on-axis and power response characteristics (Scan Speak and SB Acoustics drivers). H&V off-axis measurements included

[mmi]

Reminds me of the Heissmann Susie Q, just the driver and nice simple cabinet:

Suzie "Q" | Scan-Speak Discovery compact speaker

Noble Scan-Speak loudspeaker at the “cheap trick” rate. Equipped with Discovery H2606 / 920000 and 22W / 4534G00.

heissmann-acoustics.de

 

[J49]

Thanks . It remains to be hoped that my home made measurements and processing are correct. And even if they are, it have to taken into account that these filters were tailored to my specific driver copies. The question remains, would these characteristics be still good with drivers from a different lot?

I've ordered all the parts for a pair of these! Will post an update here with the results once finished

 

[JLGF1]

An excellent SBA 5 inch cast-frame woofer (at an excellent price) that I recently deployed in bamboo cabinets.

 

[XMechanik]

I've ordered all the parts for a pair of these! Will post an update here with the results once finished

I'll be really curious about the results. Will you take some measurements too?

 

[J49]

I'll be really curious about the results. Will you take some measurements too?

Yeah, I plan to at least get some gated on-axis measurements

 

[XMechanik]

You may also try to measure impedance characteristics, which is easy and helpful to confirm that crossover (a bit complicated) is assembled properly.

 

[XMechanik]

I'm back to the topic of THD measurements. I've upgraded Clio Pocket to version 3, it turns out that there is no need to replace the USB module. In fact, it would not even be necessary to perform new measurements to get THD graph, it would be enough to open the .crp file in the new software and select "THD" instead of "Frequecy response" in the options.
I'm still a little unsure with these THD measurements. The peak above 2kHz is ~37dB lower than the fundamental signal, which translates to 1.4% if I calculate it correct. However, previously (using a series of FFT analyses), a similar level of distortion was obtained for 96dB and now for 86dB. I wonder if everything is OK with my measurements. Anyway, THD 1.4% is not a disaster, but compared to available measurements of similar systems, the result is not impressive.

Mechano23 THD: gated (green), not gated (pink), fundamental gated (red)

 

[J49]

So, an update: I did actually build these! Some pictures below. I don't have any measurements for you though as they already went to a friend. I'll see if I can get over there to take some eventually. Subjectively, they are great.

They are Baltic birch with a simple Danish oil finish. I cut strips and laminated them to get the striped end grain look. The white is a pseudo leather vinyl I experimented with. It turned out well and I'd use it again, but I learned some things to try differently.

I built some custom stands to compliment the look. Also birch with a thin inlay of the white vinyl.

 

[XMechanik]

Your woodwork looks great!

I see you placed them away from walls. In my case they were placed quite close to the walls and this arrangement subjectively suited me best.

When it comes to measurements, try to at least measure the impedance characteristics, this is the simplest method to make sure that the circuits have been soldered properly. The impedance characteristic is in the first post, if you get identical or almost identical, it means that everything is ok.

Once again, great work and the final effect!

 

[XMechanik]

They are Baltic birch with a simple Danish oil finish. I cut strips and laminated them to get the striped end grain look.

Just wondering if you haven't any problems with enclosure leaking with these "sandwich" walls? Once I tried to do enclosure like this and discovered few leaks as the inner layers of the plywood had some knots. I ended up painting the enclosure on the inner side with epoxy.

 

[Gringoaudio1]

Baltic birch is super dense. Won’t have voids or knots.

 

[Gringoaudio1]

I thought the strips were applied like veneer over the solid birch plywood.

No?

No. This would be stacked identical layers of dense clear plywood. I always wanted to do some boxes like this. Bravo to the builder. Layers probably cut with a router using a pattern out of a sheet of 1” ply. So you are seeing the layers. It’s a different kind of plywood than most people have ever seen. A real premium product. From Finland or Russia. In 3mm thickness it bends in one direction but is stiff in the other. Good for laminating into curves. The thicker like this is just perfectly uniform great birch.

 

[J49]

Just wondering if you haven't any problems with enclosure leaking with these "sandwich" walls? Once I tried to do enclosure like this and discovered few leaks as the inner layers of the plywood had some knots. I ended up painting the enclosure on the inner side with epoxy.

As someone mentioned, birch is pretty dense and I also tried to pick pieces with few visible knots.

I definitely chose looks over practicality with this design though. This would be another reason the impedance measurement would be useful.

 

[J49]

I thought the strips were applied like veneer over the solid birch plywood.

No?

No. This would be stacked identical layers of dense clear plywood.

It is solid birch. I originally wanted to make them curved like the Magico Mini, but in the end decided that would waste too much birch and raise the cost higher than the target of this project. It is indeed premium; very expensive plywood lol.

The plywood was ripped on a table saw to create many 18x25mm (0.75x1in) pieces. Then the strips were turned on end and glued together to create the panels for sides and back.

Important note: make the laminated panels slightly over sized so you can trim them to size and have perfectly flat edges. Otherwise it'll be a heck of a time trying to line up the ends of all those strips. Use bracing rods to keep the strips flat and keep the panels from buckeling while clamping.

 

[Gringoaudio1]

I thought it was layers of Baltic Birch like this.

 

[XMechanik]

This would be another reason the impedance measurement would be useful.

If this is the wiring, everything should be OK with the filter assembly.

Anyway, it's probably better not to give up measurements. The impedance characteristics can tell a lot, not only about the crossover assembly, but also resonances in the cabinet and the tuning of the BR. You have different panel thickness (and that may affect box volume and the tuning frequency) and from what I can see the BR port is different (wider?).

 

[J49]

...port used is Monacor MBR-35 adjusted to 140mm. It wouldn't be bad to use a bit wider port for Mechano23 (keeping 45Hz tuning). The driver SB13PFCR25-4 has 13 in name but it's actually a 15cm driver.

Yes, you mentioned this port. I used the closest one I could find from parts express since it was way easier to get shipped. It has a flare and is a tad wider (+6mm) and a tad longer (+3mm). So tuning will probably be different.

Speaker Cabinet Port Tube 1-7/8" ID x 5-5/8" L Flared. Part #260-476

Speaker Cabinet Port Tube 1-7/8" ID x 5-5/8" L Flared

Speaker Cabinet Port Tube 1-7/8" ID x 5-5/8" L FlaredThis high-quality port tube features an external flare for reduced port turbulence and enhanced aesthetic appeal. Perfect for tuning small high-performance bookshelf or standmount speakers. Ports are a press-fit style and can be trimmed to...

www.parts-express.com

Hopefully this isn't too much of a sin in the face of this objective focused community and/or your meticulous write up of the project! I tried my best to keep baffe dimensions and internal volume the same. Panels final thickness was a fair bit less than 25mm because they required lots of sanding to get flat (part of the reason for cutting them thicker).

I also had a bit of fun with the woodworking so it's not a state of the art production process haha. Keep the designs coming btw, I love reading about them.

 

[sweetchaos]

Amir’s review is out:

Mechano23 Open-source DIY Speaker Review

This is a review, listening tests and detailed measurements of the "Mechano23" open-source DIY speaker. A pair was kindly sent to me by the member. You can read more about it here. Baltic birch cabinet seems quite solid and well above what you get commercially. I was surprised to see a...

www.audiosciencereview.com

 

[TLEDDY]

XMechanik:

Brilliantly done…just brilliant!

I appreciate many members of this Forum and you are now in that laudatory group!

Thank you for sharing your expertise…

Tillman

 

[Rick Sykora]

Nice effort and results!

No problem here with higher component count in a passive crossover. Allowing more design freedom is DIY's advantage over commercial products.