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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

I like the resourcefulness and re-use!

As drawn, the tube is in the same space as the side panel thickness, so that exact location isn't viable. But generally speaking, I don't see any problems with having the port off-center.

Maybe consider placing it centered horizontally left/right, and vertically just above the woofer magnet? Although the top ~ 1/3 of the port would then "overlap" the back of the tweeter, even that overlap portion would still clear the tweeter magnet by 18mm. Seems like such partial "blockage" wouldn't meaningfully inhibit air flow to the port.

EDIT: looking more closely at the driver dimensions, there is > 55mm distance between the woofer magnet and tweeter magnet. So the port would fit there, and have pretty good clearance to the front panel, but overlap a bit of the woofer chassis.

Maybe the best option is centered between the driver magnets vertically, and then offset only ~ 3cm left or right? That should provide ample clearance to the side panel (and any damping material there), as well as both driver chassis.
 
I like the resourcefulness and re-use!

As drawn, the tube is in the same space as the side panel thickness, so that exact location isn't viable. But generally speaking, I don't see any problems with having the port off-center.

Maybe consider placing it centered horizontally left/right, and vertically just above the woofer magnet? Although the top ~ 1/3 of the port would then "overlap" the back of the tweeter, even that overlap portion would still clear the tweeter magnet by 18mm. Seems like such partial "blockage" wouldn't meaningfully inhibit air flow to the port.

EDIT: looking more closely at the driver dimensions, there is > 55mm distance between the woofer magnet and tweeter magnet. So the port would fit there, and have pretty good clearance to the front panel, but overlap a bit of the woofer chassis.

Maybe the best option is centered between the driver magnets vertically, and then offset only ~ 3cm left or right? That should provide ample clearance to the side panel (and any damping material there), as well as both driver chassis.
Made a quick 3d simulation. Does this look right?
sim.png
 
Made a quick 3d simulation. Does this look right?
View attachment 419957
I think that would work pretty well. If you've got any plans for damping material on the sides, you may want to move it just a little bit further toward the drivers.

Nice you're able to draw that out quickly. I really need to break down and learn some 3D sketch software.
 
I don't know the reason, but several people have recommended a 5cm—50mm clearance from the port. This is another reason I went with higher tuning frequency on the 50mm port.
An often-referenced rule of thumb is clearance equal or greater than port diameter. So 45mm for @rokr's example. He's got that for the most part. The horizontal clearance to the closest portion of the woofer magnet circumference is far less than that, but I'm skeptical that makes much difference. So long as the area is largely clear, some minor protrusions into the region aren't going to do much.
 
Made a quick 3d simulation. Does this look right?
sim.png

I think that placing the port end near the midwoofer may involve some risk: port resonances can be effectively excited by the signal from the back of midwoofer cone. Some distance and damping material in between would be advisable. Maybe a bent port would be a solution? (it's enough to cut the tube at 45deg and glue it to create 90deg bend)
 
I think that would work pretty well. If you've got any plans for damping material on the sides, you may want to move it just a little bit further toward the drivers.

Nice you're able to draw that out quickly. I really need to break down and learn some 3D sketch software.
If you are looking for a simple 3d software, Tinkercad, its an online service, it's free, it even has a circuit board designer. Not a full 3d software (for that try Blender), but can do the job for simple tasks.
 
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I think that placing the port end near the midwoofer may involve some risk: port resonances can be effectively excited by the signal from the back of midwoofer cone. Some distance and damping material in between would be advisable. Maybe a bent port would be a solution? (it's enough to cut the tube at 45deg and glue it to create 90deg bend)
Something like that. I wonder if i can bend the tube using heat.
bent.jpg
 
Something like that. I wonder if i can bend the tube using heat.
View attachment 420064
The tube will likely get narrow in the bending place which will change the BR tuning.
I once tried a "45 degree cut" bend and AFAIR it didn't make much difference to the tuning.
 
The tube will likely get narrow in the bending place which will change the BR tuning.
I once tried a "45 degree cut" bend and AFAIR it didn't make much difference to the tuning.
Thanks. 45 degree it is.
 
Hi
New here, but have read a fair bit already.
I'm about to build a pair of these speakers. But want to ask you who seem to understand these things much better than I do; are these also viable to use laying down as a centre channel speaker in my apartment living room theatre? A pair for front channels an one as centre. Looking at the graphs for directionality I would assume it works, but would be happy to hear someone elses opinion as well. Are there any other concerns regarding using one as centre channel? Should I look at something else to build as centre instead?
 
Hi
New here, but have read a fair bit already.
I'm about to build a pair of these speakers. But want to ask you who seem to understand these things much better than I do; are these also viable to use laying down as a centre channel speaker in my apartment living room theatre? A pair for front channels an one as centre. Looking at the graphs for directionality I would assume it works, but would be happy to hear someone elses opinion as well. Are there any other concerns regarding using one as centre channel? Should I look at something else to build as centre instead?
Unfortunately the way midrange and tweeter output waves sum up in most loudspeaker prevents them from laying them down on the side. If look at radiation patterns, horizontal vs vertical, you will discover that there are places were the output varies in frequency when you measure them above and below mid-tweeter axis and side to side, especially around crossover frequency. That's because there's not only vertical or horizontal spacing between drivers but also because there's time arrival difference of sound wave caused by the midwoofer's cone shape (the acoustic center being behind the the tweeter). Most proper center channel speakers have tweeter placed above midrange, with woofers placed on the sides of the box.
In case of of XMechanik's design, the tweeter is placed inside waveguide which moves the tweeter acoustic center closer to the midrange, so the effects shouldn't be as pronounced as with tweeter dome being flushed with baffle surface.
Here are Amir's measurements and if you notice there are some places around crossover frequency 3kHz where the output changes around 30° above and below axis (blue wish dots) where the output drops.

 
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Does anyone have a source for the project woofer and tweeter? Solen and Madisound are OOS. Thanks
 
Hi
New here, but have read a fair bit already.
I'm about to build a pair of these speakers. But want to ask you who seem to understand these things much better than I do; are these also viable to use laying down as a centre channel speaker in my apartment living room theatre? A pair for front channels an one as centre. Looking at the graphs for directionality I would assume it works, but would be happy to hear someone elses opinion as well. Are there any other concerns regarding using one as centre channel? Should I look at something else to build as centre instead?
If you can live with the atypical appearance, this speaker would be fine in the center in its normal vertical orientation. Placed below a television, it may be a bit lower than ideal, but still fine. You could tilt up slightly if you like.
 
Does anyone have a source for the project woofer and tweeter? Solen and Madisound are OOS. Thanks
Consider audiohobby or soundimports in Europe. The typically lower prices and no sales tax tend to cancel the higher shipping fees. Shipping times are usually very reasonable, less than one week in many cases for me.
 
Inductors:
  • L1 330 uH 0.258 R
  • L2 560 uH 0.51 R
  • L3 1.5 mH 0.94 R
  • L4 390 uH 0.42 R

Capacitors:
  • C1 6.8 uF
  • C2 27 uF
  • C3 18 uF
  • C4 820 nF
  • C5 3.3 uF
  • C6 2 uF

Resistors:
  • R1 12 R
  • R2 8.2 R
  • R3 15 R
Just reading through this thread and seems like a super interesting build!!

I haven’t made it through all 22pg yet - lol, but looking at compiling a build parts list at Madisonsound.

Wondering if this is still the x-over parts list or if any recommended changes have come about?

Has anyone perhaps put together a BOM for the x-over components?

Thanks All!
 
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There is a BOM for the xover components in post 1 of the review thread. It has links to order. It's based on ordering from stolen ca. This is the BOM I based my PCB on.
 
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