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

Hi all!

If these speakers are used in a 5.1 HT setup with 3 sealed SW crossed around 80-100Hz... would you recommend going with a sealed alignment? Or that would require a re-work on the XO circuit?

@XMechanik thank you again for sharing, and also want to ask if you consider this design a finished one or it's a WIP?
 
@XMechanik thanks again for sharing.
Mechano23-2.png
I would like to ask you what the following change would mean on the front face. See attached photo.
 
mga2009 said:
If these speakers are used in a 5.1 HT setup with 3 sealed SW crossed around 80-100Hz... would you recommend going with a sealed alignment? Or that would require a re-work on the XO circuit?
Click to expand...
Probably with the sealed approach Xmax will be reached with higher drive, if we are talking about frequencies lower than say 35Hz. On the other hand BR enclosure have an advantage above this frequency due to the 45Hz tuning which decreases cone excursion in the region of this frequency. I've usually assumed that most of the signal energy is above 40Hz but it may be no longer valid with HT. It would probably be best to actively filter out the signal that the SWs take over if your AV amp/processor has an option like this.
mga2009 said:
thank you again for sharing, and also want to ask if you consider this design a finished one or it's a WIP?
Click to expand...
Even though the design can be considered finished, there is "Mechano23 playground" in this thread, so any on can experiment, modify, share results, suggest changes (even if only for discussion).
 
Gada said:
@XMechanik thanks again for sharing.
View attachment 408661I would like to ask you what the following change would mean on the front face. See attached photo.
Click to expand...
The impact of changes in the front panel would be easier to estimate if the dome was aligned with the panel but here it is placed quite deep in the horn. As I understand it, the idea here is to widen the dispersion of the tweeter by narrowing the enclosure near the tweeter. Since the dome is placed deep in the horn, the effect may be weaker than expected. Secondly, the idea of widening the dispersion raises some doubts. Wide dispersion means low directivity, and here the tweeter with the horn was intentionally selected to increase the directivity and match it to the directivity of the much larger (and therefore more directional) midwoofer. Directivity control is the key to smooth PIR and PR characteristics with constant on-axis response.
But there is no doubt that the enclosure with such a front panel would look far more attractive than a simple box like in the original.
 
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XMechanik said:
The impact of changes in the front panel would be easier to estimate if the dome was aligned with the panel but here it is placed quite deep in the horn. As I understand it, the idea here is to widen the dispersion of the tweeter by narrowing the enclosure near the tweeter. Since the dome is placed deep in the horn, the effect may be weaker than expected. Secondly, the idea of widening the dispersion raises some doubts. Wide dispersion means low directivity, and here the tweeter with the horn was intentionally selected to increase the directivity and match it to the directivity of the much larger (and therefore more directional) midwoofer. Directivity control is the key to smooth PIR and PR characteristics with constant on-axis response.
But there is no doubt that the enclosure with such a front panel would look far more attractive than a simple box like in the original.
Click to expand...
What is clearly reduced with such a design is the edge reflection on the front panel.
I also share your concerns about the effects of the horn/waveguide.
 
Do you think it would be possible to 3d print the front face? Any idea how thick it would need to be in that case?
 
Ulf said:
Do you think it would be possible to 3d print the front face? Any idea how thick it would need to be in that case?
Click to expand...
Yes, if you have a large enough printer. A similar thickness to wood should work if you have a high infill percentage, or if you fill with something like a plaster of paris / PVA mix. The PVA stops the plaster ringing.
 
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My printer claim to be able to print 30x30x40 cm so it should be possible to do the whole enclosure (shell) in one print but I don't know if that's a good idea.. Thanks for the PVA tip, I would not had thought of that.
 
Ulf said:
My printer claim to be able to print 30x30x40 cm so it should be possible to do the whole enclosure (shell) in one print but I don't know if that's a good idea.. Thanks for the PVA tip, I would not had thought of that.
Click to expand...
I would strongly advise against it. On the one hand, the plastic would dampen very strongly, and on the other hand, the resonances would be catastrophic. The chassis would also be exposed to micro-vibrations, which would worsen the listening experience.
I know of a few DIY and commercial projects where you have already reached many limits with smaller housings.

You could try printing it solid with a hard plastic, which would not only be expensive.
Or you could print with newer materials for technical areas, but that would cost around €200/kilo, the material is very abrasive and requires high temperatures.
It would be cheaper to have the fronts milled.
 
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BTW, I've designed a port to print on 3d printer, also I'll try to make something similar to Polk ES20 port redirection.
 
Here are a few pictures of my build. I really enjoyed putting them together and the sound is excellent, as far as I can tell. Big thank you for the design!
All parts came from Soundimport except the wood and fibreglass plates for the crossovers.

I rounded the sides of the front, mainly for estethics. It came out nice I think with the veneer. Since I completely forgot about the bracing Im now a bit worried. Do You think the radius of the baffle sides makes it even weaker? Maby some kind of reinforcement could be glued in the inside corner, or is the bracing better?
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How complicated is the crossover to build for a novice? Does anyone make PCB for these?

Edit: I literally scrolled up two posts. THANK YOU!
 
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HighFutility said:
How complicated is the crossover to build for a novice? Does anyone make PCB for these?

Edit: I literally scrolled up two posts. THANK YOU!
Click to expand...

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

Okay, finally got all my parts in. Would appreciate it if anyone could verify my crossover wiring. Arrows just indicate left or right wire of each component . Thanks in advance! The wiring looks ok, except the place marked with question mark. It seems that tweeter coil (0.39mH) is shorted an...
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Good morning @Woody99 would it be possible to have a print in pdf format of the MDF board of the crossover.
Thanks.
 
Gada said:
Good morning @Woody99 would it be possible to have a print in pdf format of the MDF board of the crossover.
Thanks.
Click to expand...
See attached. Board dimensions are 176mm x 115mm x 6mm and is designed to fit through the woofer hole and sit on speaker floor fixed with four corner screws. Component dimensions, holes and spacing are designed to suit crossover parts easily available in Australia and keep costs low, so best to check the layout using your own components.

A fully-illustrated instruction manual for the Mechano 23s is now complete and can be downloaded from NB Audio's 'Projects' page here.

The manual is intended primarily for use by Men's Shed members but in the spirit of this open source project can be used by anyone. It includes a complete component list and current pricing for Australian builders along with lots of hints and tips for beginners. NB Audio in Adelaide were kind enough to cut the crossover boards for our Men's Shed project. The board was designed by Phil Norman in Melbourne.

I think the combination of XMechanik's wonderful design and this instruction manual makes the Mechano 23s ideal bookshelf speakers for first-time builders. We will be having our first Mechano 23 speaker-building workshop at our local men's shed early next year in Sydney.
 

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