Two-Way Version 2 build thread

[DeZZar]

Hi All,

Thought I would start a build thread to share my current project. I'm working on a second iteration of a design I started last year which I had jokingly called the "Quick Two Way" thinking I would just throw together a two way design during one of our countries COVID lock-downs to keep me occupied.

There ended up being nothing quick about it of course but I was seriously impressed with the results and instead of moving on to another planned project I really wanted to try another version with an improved cabinet design and bass alignment.

The original project I posted here for feedback some time ago:
http://techtalk.parts-express.com/fo...two-way-design

In the second version of this I wanted to:

• Reduce the cabinet size to something more reasonable for a two-way floor standing design
• Change the alignment a little and ultimately correct an issue where the tuning of the original cabinet ended up being a lot lower than modelled (which I couldn't do anything about after the fact)
• Experiment with some internal sound energy dissipation ideas
• Change the aesthetic design

This design uses the Dayton RS180P-4 7" woofer and the SB Acoustics SB29RDAC-C000-4 tweeter with a 1,750Hz crossover point.

So I finally pulled the trigger and have started the new build. Here is the revised design


Cabinet has been reduced to a net effective internal volume of 26L vs the original 32L and tuning moved to 39Hz. This will produce f3 around the 36-37 Hz range.

The offset rippled interior. I have no proof that this does anything meaningful - its an idea I had years ago and never really had the chance to execute on it. I thought it might be a pointless idea until I happened to stumble upon one other commercial example of this which motivated me to try it out.

The theory is simple - remove the possibility of any directly reflective surface - in this case particularly with respect to the waves directly behind the drivers - using a pattern that should in theory scatter the sound waves and use up more of their energy before they have a chance to interact with the driver again.

I hypothesize that any legitimate improvement here would be seen in the areas affected by standing waves and in distortion measurements. I still have the first versions with me so I'll be able to make comparative measurements.

Before anyone asks, there is no science to the shape and size of the ripples. I just drew up what I thought was reasonable and sent them off to my CNC guy to be cut.

Sheet stock cut down into the panels. This is a layered construction so starting with 12mm (1/2 inch) MDF.


Internal braces cut

Just testing the layout and thinking about which way to go about the glue up.

[DeZZar]

The CNC cut rippled panel. There is a bit extra in here for another project - was obviously just more economical to get it all cut at the same time.



Ready for glue up. This is the section that forms both the bottom surface of the cabinet that the woofer sees as well as the wall for the slot port.


In the previous version I found there were some obvious standings waves corresponding to cabinet height seen particularly in the port measurements. So this time around I wanted to see if I could improve on these by first curving the bend in the port as well as better treating the bottom surface of the cabinet.

These curved sections were rather painful to make but they make sure the port follows a proper radius as it bends towards the exit.

[AEIOU]

Open cell Egg Crate foam will work much better.

[DeZZar]

Cabinet gluing up. In this design the sides have to be glued on last so here just gluing the tops and bottoms to the rear panel.

I used several dowels to strengthen the joints here and help with alignment when clamping.


The small rear enclosure for the crossover added as well.


Baffles prepared and here making the cutouts and recess for the drivers. (yes that's a home made circle cutting jig if anyone's wondering)


Cutouts finished and a chamfer added to the rear for the woofer.

[DeZZar]

For the finish on these versions all corners are rounded - top, bottom, sides and corners - and the intention is that they would be wrapped in "leather". Before committing to this I wanted to make sure it was possible (as in possible for me and to a high standard) so I made a small version to test it out.

36mm round over for front edges and 25mm for the sides. The side panels are just screwed on to start with so they can be separated.


Next the sides are removed and the joined edges receive a small recess to cater for the thickness of the leather.

You can see the final gap here


Having covered things in "leather" before I knew that corners tend to be the hardest part and you need space for inevitable "bunching up" of the material, so I used a dovetail router bit to cut a gutter in the back edge:

[DeZZar]

Gutter works well and when you bring the two back together they meet up nicely.

The timber underneath the model is solid Jarrah which will complete the side panels.

[Steve Lee]

Really nice set-up and interesting project, DeZZar.

Keep going . . .

[scottvalentin]

Wow excellent work! Great attention to detail, high value drivers, solid construction - sure to be a winner! Well done

[Steve Lee]

DeZZar - tell us more about that ROUTER in the circle cutting jig, PLEASE?

It looks like you made a dust collection base for it and reused an existing laminate router motor - please elaborate because I NEED ONE JUST LIKE IT.

Thanks.

[tomzarbo]

Now we're talking! That looks gorgeous!

Do you know that weight of the leather you used? Looks to be 2.5 to 3.5 ounce? The thin stuff seems to be very expensive.
I'm in the process of doing some leather side panels on speakers but nothing that difficult.

You really pulled that off nicely! Have you worked with leather before?

TomZ

[DeZZar]

DeZZar - tell us more about that ROUTER in the circle cutting jig, PLEASE?

Hi Steve,

Correct I took the standard base the trim router came with and modelled a new one with dust collection. Its 3D printed. Happy to send you the 3D print file if you're interested and have access to a 3D printer.

It accepts what I believe to be a fairly standard trim router body size of 65mm (2.5inch). The one I'm using is just the corded Ryobi trim router (https://www.ryobi.com.au/products/de...outer-rtr400-s) but I believe the Makita option will work as well.




The little hole on the side and the flat surface is for mounting an LED light so you can see what you're cutting.

[DeZZar]

Do you know that weight of the leather you used? Looks to be 2.5 to 3.5 ounce? The thin stuff seems to be very expensive.
I'm in the process of doing some leather side panels on speakers but nothing that difficult.

You really pulled that off nicely! Have you worked with leather before?

Thanks Tom.

I've worked a little bit with this "leather" before so I'm familiar with what it will and wont do. The parenthesis around "leather" is because its not real hide - its a leather look material backed PVC vinyl. I would definitely like to use real leather but the cost is quite high and I'm not familiar with how well it would take to these shapes.

The stuff I'm using is about 0.7mm in total thickness (I'm not sure how that translates to the ounce measure).

I have a whole heap of different samples as its hard to find really good stuff. Most only stretches' in one direction and its almost impossible to find without the material backing on it. The stuff I settled on isn't too shiny or dull, has a nice grain texture to it that is sufficiently random that over large surface areas you cannot see any repeating patterns. I've got samples here where the quality is really nice but when you lay it out you can clearly see a small repeating pattern.

[tomzarbo]

Thanks Tom.

I've worked a little bit with this "leather" before so I'm familiar with what it will and wont do. The parenthesis around "leather" is because its not real hide - its a leather look material backed PVC vinyl. I would definitely like to use real leather but the cost is quite high and I'm not familiar with how well it would take to these shapes.

The stuff I'm using is about 0.7mm in total thickness (I'm not sure how that translates to the ounce measure).

I have a whole heap of different samples as its hard to find really good stuff. Most only stretches' in one direction and its almost impossible to find without the material backing on it. The stuff I settled on isn't too shiny or dull, has a nice grain texture to it that is sufficiently random that over large surface areas you cannot see any repeating patterns. I've got samples here where the quality is really nice but when you lay it out you can clearly see a small repeating pattern.

I have some material I purchased from Hobby Lobby that resembles grained leather as well, but is a thin fabric. I would say it's pretty much the same as what you described. I hope my project comes out quality looking as yours did. I'm encouraged to give it a try now.

TomZ

[DeZZar]

So long as the material has some flex/stretch to it you can definitely get it to mold around corners. I did attempt to cover the entire curved edge/corner in one piece rather than two and this doesn't work - it just doesn't have enough stretch and its impossible to smooth out where it needs to bunch up. With the two part approach you can get a really good finish.

[DeZZar]

Glued in the first braces


And then the rippled panel pieces glued up for the top section, trimmed and glued in place!



Top sections all glued up ready for mounting the baffles.

[wogg]

That is going to be a ridiculously solid cabinet. Well done sir!

[DeZZar]

First baffle glued up.




Slot port section all glued up and just placed in position to see how it looks.


The rounded back corner of the port needed to have the transitions smoothed over so I've added some filler and sanded that smooth as well. This will get a couple coats of sanding sealer to harden and polish up the surface so its nice and smooth.