Mechano23 Open-source DIY Speaker Review

[Chris*42]

Congratulations to Jarek/ @XMechanik for this excellent work. IMO this is a benchmark in price/performance ratio!

And many thanks to Amir for testing this device and taking this contribution to the ASR front page. I think, this is a wonderful opportunity to give DIY-people a constructive feedback about their project with the help of professional tools (who has the opportunity to measure with a Klippel-System?)

By the way, I just ordered a set of these speaker parts...

…and this is the result. I build up these speakers with a little variation (passive radiators SB15SFCR-00 on the left/right side panel instead of BR vent on the back panel) to avoid the resonance (vent at 1 kHz) and let me easily change the tuning frequency. Without the additional mass, the system (PR and cabinet of ca. 7.5l) has a tuning frequency of 53Hz. Adding ca. 31g will result in a Helmholtz frequency round about 45Hz - this will be the next step in my experiments.

My instant impression of these speakers was, that they sound so very natural and absolut correct! Even the upper/mid bass is fine, as long as you don’t set the volume too high. These are really amazing speakers at this price level!

I can only repeat the congratulations to @XMechanik for sharing his construction and @amirm for making and publishing the measurements!

 

[XMechanik]

I build up these speakers with a little variation (passive radiators SB15SFCR-00 on the left/right side panel instead of BR vent on the back panel) to avoid the resonance (vent at 1 kHz)

Interesting approach but there may be some drawbacks. According to the simulations, spl characteristic for the passive radiator rolls back bit faster and steeper.

BR vs. PR comparison (both 45Hz):

 

[Salt]

No significant difference at -3 or -6 dB, and there room modes are the predominant problems, not so much a speaker.

 

[Chris*42]

Interesting approach but there may be some drawbacks. According to the simulations, spl characteristic for the passive radiator rolls back bit faster and steeper.

BR vs. PR comparison (both 45Hz):
View attachment 370666

Yes, I agree, there will be a small difference in bass performance. On the other hand you avoid the port resonance and the critical air speed discussion. IMO, you can decide which design is more suitable for your personal taste (and the PR solution is always more expensive).

 

[a4eaudio]

Agreed. If anything, my leisure time is often worth negative $/hour, as I'm often spending money(going out to eat, entertainment, etc.).

Thank you. I didn't reply earlier because I didn't want to preach from my economist pulpit.
The "Opportunity Cost" of ones time is the "Next Best Alternative" of that time. If you are taking time off (paid) work to build speakers, then you should, for sure, factor that cost in. But if you are building speakers instead of watching TV, taking a walk, etc. then that time did not cost you anything.

 

[Chris*42]

I have tried to do some simple measurements in my home environment to see the effect of the passive radiator. I own only a "hobby equipment", so the results are not very exactly and the acoustic measurements are of course dominated by room modes in the lower frequency range. But one effect of the PR seems to be apparent: the woofer shows a lower level of harmonic distortions at higher SPL. This result coincided with my subjective impression, that these speakers sound very clear and free of distortions when I hear them at a bit higher level.

 

[XMechanik]

Thank you @Chris*42 for sharing the measurements.

I'm a bit surprised that also the 400-2000Hz range seems to be less distorted (comparing to the characteristics taken by Amir, as below) and I wonder if changing BR to PR can be the reason or maybe there is some other factor?

 

[Chris*42]

Finally, I made some measurements with different masses (0g, 16g and 31g) mounted on the PR. As you can see both the cut off frequency of the woofer and the SPL of the PR decrease with greater mass. As @XMechanik mentioned above the characteristic of the frequency roll off is a bit faster and steeper compared to the BR solution.

After some listening tests I prefer the variant with m =16g. This is the best compromise between low frequency cut off and bass level according to my personal taste.

 

[Fred H]

Group buy thread at https://audiosciencereview.com/forum/index.php?threads/group-buy-for-mechano23-flat-packs.54813/

 

[S=klogW]

…and this is the result. I build up these speakers with a little variation (passive radiators SB15SFCR-00 on the left/right side panel instead of BR vent on the back panel) to avoid the resonance (vent at 1 kHz) and let me easily change the tuning frequency. Without the additional mass, the system (PR and cabinet of ca. 7.5l) has a tuning frequency of 53Hz. Adding ca. 31g will result in a Helmholtz frequency round about 45Hz - this will be the next step in my experiments.

My instant impression of these speakers was, that they sound so very natural and absolut correct! Even the upper/mid bass is fine, as long as you don’t set the volume too high. These are really amazing speakers at this price level!

I can only repeat the congratulations to @XMechanik for sharing his construction and @amirm for making and publishing the measurements!

Would it reduce the speakers' performance it I install the passive radiators, SB15SFCR-00, on the back panels rather than on the left/right side panels?
Thanks for taking the Mechano23 design in an interesting new direction.

 

[Chris*42]

Would it reduce the speakers' performance it I install the passive radiators, SB15SFCR-00, on the back panels rather than on the left/right side panels?
Thanks for taking the Mechano23 design in an interesting new direction.

Most of the solutions I have seen so far have the PR mounted on the back panel. This was also my first approach, but the most important goal during my considerations was not to change the size of the front/back panel. I only increased the thickness of the front panel (21mm BB) for stability reasons.

In the back panel solution there would be very little space for solid terminals, so I decided to put the PR on the left/right side panels.

IMO mounting the PR on the back panel will certainly show equally good results.

 

[Salt]

Most of the solutions I have seen so far have the PR mounted on the back panel. This was also my first approach, but the most important goal during my considerations was not to change the size of the front/back panel. I only increased the thickness of the front panel (21mm BB) for stability reasons.

In the back panel solution there would be very little space for solid terminals, so I decided to put the PR on the left/right side panels.

IMO mounting the PR on the back panel will certainly show equally good results.

You can install a frame into the back that fits the PR.

 

[BossBunos]

…and this is the result. I build up these speakers with a little variation (passive radiators SB15SFCR-00 on the left/right side panel instead of BR vent on the back panel) to avoid the resonance (vent at 1 kHz) and let me easily change the tuning frequency. Without the additional mass, the system (PR and cabinet of ca. 7.5l) has a tuning frequency of 53Hz. Adding ca. 31g will result in a Helmholtz frequency round about 45Hz - this will be the next step in my experiments.

My instant impression of these speakers was, that they sound so very natural and absolut correct! Even the upper/mid bass is fine, as long as you don’t set the volume too high. These are really amazing speakers at this price level!

I can only repeat the congratulations to @XMechanik for sharing his construction and @amirm for making and publishing the measurements!

Very nice pr variant Chris! Did you still use the same amount of stuffing as the original design? I just ordered the parts my self

 

[Chris*42]

Very nice pr variant Chris! Did you still use the same amount of stuffing as the original design? I just ordered the parts my self

I used one layer of polyurethane foam („Bondum 800“) on the panels (see attached picture) and polyester wool for the inner volume (unfortunately I didn’t take a picture of this state of construction). As you can also see, I divided the crossover into two parts, one for the woofer and one for the tweeter to reduce the complexity of the layout.

Good luck in building your pair of speakers!

 

[Salt]

Isn't coil wire a bit inflexible for internal wiring?

 

[Chris*42]

Isn't coil wire a bit inflexible for internal wiring?

I prefer this kind of wiring because I can shape the wire the way and where I want it...

 

[Salt]

Agree for woofers, but tweeter's soldering post often are attached delicate and there I prefer some flexibility.

 

[Rick Sykora]

I prefer this kind of wiring because I can shape the wire the way and where I want it...

How do you keep the wire from rattling or buzzing?

 

[Salt]

Damping

 

[BossBunos]

I used one layer of polyurethane foam („Bondum 800“) on the panels (see attached picture) and polyester wool for the inner volume (unfortunately I didn’t take a picture of this state of construction). As you can also see, I divided the crossover into two parts, one for the woofer and one for the tweeter to reduce the complexity of the layout.

Good luck in building your pair of speakers!

Thanks for the info! It will be my first DIY speaker ever. How do you prevent the stuffing from touching the rear of the driver/PR? Or doesn't that matter at all.
And do you think the improved distortion result has to do with the inceased baffle thickness, the use of the PR or lining the inner walls with the foam?