Curved Natalie P design thread (my first build)

[voltage23]

Hi all,

I've been lurking for awhile and am finally getting close to starting my first build. I've decided to attempt the Natalie Ps (link here), but plan to make a curved cabinet for aesthetics. I'm quite confident in the woodworking aspect, but since this will be my first build, I want to make sure I'm not missing anything from an auditory perspective. Recognizing that in any build there will be tradeoffs, here are a couple that impact my build:

1) Speaker location: These will be going in a niche in the wall on either side of the TV (picture below). Not a great location I'm sure, but it's the only place they can go. They will be firing into a big open living area so I'm sure the room effects will be horrible. I hope to eventually connect these to a DiracLive processor to compensate.

2) Aesthetics: I am willing to trade a little bit of sound quality for a more unique look (hence the curved shape). That said, if I'm doing anything really stupid please let me know. Or if I could make minor tweaks to my design to improve the sound quality, I'd be interested in considering them.

So, on to the design:


That’s a 3” Precision Port at the bottom. The width at the widest point is 9”, the depth is 14.25” and the height is 34” (36” including the stand). The internal volume is about 1.4 cu. Ft (40 L), so it’s right in between the two recommended sizes in the original thread.

The below snips show the method I’ll use to build the speaker. I’ll be building the speaker with 19 layers of 3/4" all glued together. The middle layers will alternate between a three brace design and a two brace design as shown. It will be very well braced!


Seeing as this is my first speaker build, I have some questions:
1) Which crossover? Given the niche these will be sitting in, am I better off with the original crossover or the in/on wall one?
2) Port tuning: the original thread recommends a 30L box tuned to 32 hz or a 50L box tuned to 28 hz. Since I am right in between at 40L, any recommendations on what I should tune the port to? There’s no subwoofer in the near future, so some additional bottom end would be helpful.
3) Damping: I see whispermat recommended for internal damping. What is the best place to purchase it? Where should I be applying it? Any reason to consider something different?
4) Securing the port tube: since this port will be pretty long (it will need an elbow), I’m assuming I should support it along its length somehow? What would be a good way to do this? Stick some whispermat between it and the braces to prevent rattling then secure it to one of the braces with straps?
5) Anything else I’m overlooking?

Thanks for your help!

[JonMarsh]

Regarding your questions-

1) Unless you actually build them into the wall, go with the standard crossover. It's better to have a fat lower mid and bass subjectively, than to be too leaned out. If you have system EQ, you can always tailor that later.

2) With no subwoofer in the picture, better to use the lower tuning to keep the driver loaded. It won't be as flat down low, but you won't get into trouble. Model it in Unbox for the specifics, or if you need, let us know and one of us can model the specifics.

3) mass loaded Whisper mat is hard to find these days. You might want to try a combination of Dynamat to damp the enclosure wall, and denim based liner, or fiberglass or acoustic foam. PE is a reasonable place to check, but the denim stuff is available at Home Depot, of all places...

4) Port length tuning that box could be a problem- normally you don't need that long a port with the recommended alignments to worry about any additional support- the tube is pretty light and strong. An option to consider is top or bottom mounting of the port.

5) I'm sure you'll think of something once you get into this... read up on other translam builds, such as Steve Mannings, and I highly, HIGHLY recommend using threaded rod the whole length of the build. Check out how Gauder Akustik builds theirs.


http://www.6moons.com/audioreviews/isophon/1.html

[TEK]

Hi
Looks like a really cool build. I really looking forward to following this!
It is impotant to keep the individual placement of the drivers as well aa the baffle width.
For port tuning I would think that 30hz is the magic number with a 50l cabinet.

I see that you are planning on making the curved shape using a trans-slam design?
What material will you be using? How willl you cut out the parts, cnc? And what finish are you planning fi

[TEK]

5) I'm sure you'll think of something once you get into this... read up on other translam builds, and I highly, HIGHLY recommend using threaded rod the whole length of the build. Check out how Gauder Akustik builds theres.

I have heard other that have done this where the wood has broken up as the wood and the steel expand different at various temperatured. As a minimum you should ensure that the bars are not beeing glued to the wood in the translam.

[voltage23]

Regarding your questions-

1) Unless you actually build them into the wall, go with the standard crossover. It's better to have a fat lower mid and bass subjectively, than to be too leaned out. If you have system EQ, you can always tailor that later.

2) With no subwoofer in the picture, better to use the lower tuning to keep the driver loaded. It won't be as flat down low, but you won't get into trouble. Model it in Unbox for the specifics, or if you need, let us know and one of us can model the specifics.

3) mass loaded Whisper mat is hard to find these days. You might want to try a combination of Dynamat to damp the enclosure wall, and denim based liner, or fiberglass or acoustic foam. PE is a reasonable place to check, but the denim stuff is available at Home Depot, of all places...

4) Port length tuning that box could be a problem- normally you don't need that long a port with the recommended alignments to worry about any additional support- the tube is pretty light and strong. An option to consider is top or bottom mounting of the port.

5) I'm sure you'll think of something once you get into this... read up on other translam builds, such as Steve Mannings, and I highly, HIGHLY recommend using threaded rod the whole length of the build. Check out how Gauder Akustik builds theirs.


http://www.6moons.com/audioreviews/isophon/1.html

Thanks for the responses, it's an honor! I'll certainly look into the threaded rod, thanks for the tip. Is the parts express sonic barrier a good substitute for whispermat?

[voltage23]

I see that you are planning on making the curved shape using a trans-slam design?
What material will you be using? How willl you cut out the parts, cnc? And what finish are you planning fi

The layers will be 3/4" MDF. My plan is to make a template by printing out the shape on a plotter, glue it to a piece of MDF, rough-cut with a jigsaw and then sand to the exact edges. Once I have the template, I'll use a pattern matching router bit to make the copies. I wish I had access to a CNC mill, but I think this will work even if it takes a while.

The front baffle will be 3/4" hardwood (haven't decided species yet) glued to 3/4" MDF. The MDF sides will be painted black (won't be able to see them in the niche anyway). The front panel will probably get satin poly.

[voltage23]

Regarding your questions-

1) Unless you actually build them into the wall, go with the standard crossover. It's better to have a fat lower mid and bass subjectively, than to be too leaned out. If you have system EQ, you can always tailor that later.

2) With no subwoofer in the picture, better to use the lower tuning to keep the driver loaded. It won't be as flat down low, but you won't get into trouble. Model it in Unbox for the specifics, or if you need, let us know and one of us can model the specifics.

3) mass loaded Whisper mat is hard to find these days. You might want to try a combination of Dynamat to damp the enclosure wall, and denim based liner, or fiberglass or acoustic foam. PE is a reasonable place to check, but the denim stuff is available at Home Depot, of all places...

4) Port length tuning that box could be a problem- normally you don't need that long a port with the recommended alignments to worry about any additional support- the tube is pretty light and strong. An option to consider is top or bottom mounting of the port.

5) I'm sure you'll think of something once you get into this... read up on other translam builds, such as Steve Mannings, and I highly, HIGHLY recommend using threaded rod the whole length of the build. Check out how Gauder Akustik builds theirs.


http://www.6moons.com/audioreviews/isophon/1.html

Thanks for the responses, it's an honor! I'll certainly look into the threaded rod, thanks for the tip. Is the parts express sonic barrier a good substitute for whispermat?

[ergo]

I've done a cylinder shape project in past that was consisting of horizontal slices of MDF. I did use threaded rods, but I oversized the hole somewhat so that if some glue gets in there it probably will not make the rod/box very rigidly tied.

Another note is that be prepared to a LOT of glue cleaning and sanding. I did the Minerve_EE boxes with top and bottom done with such sliced method. The CNC cuts were very close tolerance and I assumed I have very little to sand, but after glue up it did turn up to take major time and effort. Perhaps cleaning up the glue already after the clamps are applied for some tens of minutes would help... as later the glue hardens and becomes a hassle to remove. The thin trace of it should be easier to sand back.

[voltage23]

That's a nice looking cabinet! Do you have a build thread?

[Steve Manning]

The layers will be 3/4" MDF. My plan is to make a template by printing out the shape on a plotter, glue it to a piece of MDF, rough-cut with a jigsaw and then sand to the exact edges. Once I have the template, I'll use a pattern matching router bit to make the copies. I wish I had access to a CNC mill, but I think this will work even if it takes a while.

The front baffle will be 3/4" hardwood (haven't decided species yet) glued to 3/4" MDF. The MDF sides will be painted black (won't be able to see them in the niche anyway). The front panel will probably get satin poly.

Trust me it will take a while ...... 8O I used an mdf template when I did mine and it worked well. Ergo has got a good idea with whipping the glue squeeze out off. If you go with something like Titebond III, it wipes off well with a wet rag. Smearing it around over the surface will actually help seal the edges, which you will need to do prior to painting anyway.

With you baffle idea, if you can get what ever wood species you decide on, quarter sawn , it will help a lot with stability.

Looking forward to seeing some pictures.

[TEK]

Are there a special reason you have choosen the translam approach for this speaker?
I'm sure it will work, but I also think that there are other approaches that might work just as well.
One approach would be to just make the top and bottom (where you have the sharpest bend) out of pices of MDF that is going from fronth to back and then glued and shaped. The rest of the sides have quite little bend and could be made by gluing several thin sheets of MDF glued to a frame.
There are some ideas here that might be used for the top:

http://www.htguide.com/forum/showthread.php?42662-Building-In-Khan-Neatos-for-the-living-room&p=607766&viewfull=1#post607766

This method will use less MDF and might be easier all-in-all.

[ergo]

That's a nice looking cabinet! Do you have a build thread?

It's part of the Minerva general thread

http://www.htguide.com/forum/showthread.php?43049-Minerva-Monitor-quot-Patience-my-ass-I-m-going-to-go-build-something!-quot&p=610847&viewfull=1#post610847

+ here

https://www.flickr.com/photos/140323147@N06/albums/72157664509581331

[voltage23]

2) With no subwoofer in the picture, better to use the lower tuning to keep the driver loaded. It won't be as flat down low, but you won't get into trouble. Model it in Unbox for the specifics, or if you need, let us know and one of us can model the specifics.

I modeled it in WinISD. Here's what I'm showing:


The green is 28 Hz, pink 30, and blue 32. Recommendations?

[voltage23]

Are there a special reason you have choosen the translam approach for this speaker?
I'm sure it will work, but I also think that there are other approaches that might work just as well.
One approach would be to just make the top and bottom (where you have the sharpest bend) out of pices of MDF that is going from fronth to back and then glued and shaped. The rest of the sides have quite little bend and could be made by gluing several thin sheets of MDF glued to a frame.
There are some ideas here that might be used for the top:

http://www.htguide.com/forum/showthread.php?42662-Building-In-Khan-Neatos-for-the-living-room&p=607766&viewfull=1#post607766

This method will use less MDF and might be easier all-in-all.

Good idea. I'll think about it.

[voltage23]

Trust me it will take a while ...... 8O I used an mdf template when I did mine and it worked well. Ergo has got a good idea with whipping the glue squeeze out off. If you go with something like Titebond III, it wipes off well with a wet rag. Smearing it around over the surface will actually help seal the edges, which you will need to do prior to painting anyway.

With you baffle idea, if you can get what ever wood species you decide on, quarter sawn , it will help a lot with stability.

Looking forward to seeing some pictures.

New plan: after reading some more, I've got myself nervous about the hardwood splitting if I glue it, so I'm going to screw it in from the back instead (with oversized screw holes in the MDF to allow movement). Will I need some sort of gasket between the hardwood and the MDF to seal it, or should the tension of the screws give a good enough seal? Also, I'm leaning toward using canarywood. Anyone worked with it before?

[TEK]

I think you need a gasket...

[Steve Manning]

Here is an example of what Magico does. Not sure of the exact material, but I would imagine McMaster Carr would have something.

[fbov]

Here's a different perspective.

1) doesn't matter if you're doing room correction. Having made freestanding and in-wall NatP's, this speaker placement will have better tonal balance with the in-wall XO. However, room correction fixes it, and changing applications (freestanding speakers work in many locations) supports Jon's advice.

2) may matter tremendously, depending on your taste and the room size. Judging by the reflection in the display, this is a large room, with a low frequency threshold for room gain. In this application, I'd tune the box higher, to insure a good strong bass presence through 40Hz, given there will be little room reinforcement this high. In a mid-sized room, like mine (~2,500 cu. ft.), I'd tune lower, trading a now-reinforced 40Hz response for more and lower bass response.

I also ran a Unibox simulation using the current RS180-8 datasheet.
40Hz tune needs a 6" port, gives flat response and a 30Hz F10 (-10dB is perceived as half as loud)
35Hz tune needs an 8" port, give a -2dB shelf
30Hz tune needs a 12" port, gives a -4dB shelf and a 25Hz F10

I've intentionally rounded the lengths, because small distances are insignificant when 1" length change is only 1Hz shift in tune. You might start with a 12" length and tune by ear down to 6" (or shorter (higher tune) if that's what your listening prefers. A 4.5" port predicts a 1.5dB peak at 50Hz.

As to the rest... I suggest using an epoxy wood finish (West is one good one) for assembly, and lots of it. Wood is insatiable in it's thirst for moisture, and it's propensity to dry out. I'd also install the brace styles in pairs, for strength, or add a perpendicular piece tying them together.

Neat project, if well into the advanced skill arena. Plain boxes can sound as good as fancy, if issues arise, but fancy is more fun.

HAve fun,
Frank