Zaph SR71 Build Thread...

[lunchmoney]

So after weeks of agonizing over what speakers to build, I finally decided to go smaller and higher-end, and build the Zaph SR71's...

First things first: huge thanks and round of applause to Zaph for his enormous contributions to the DIY community, including this design. I have spent many hours pouring over his site, and have learned a tremendous amount from doing so.

Here is a link to Zaph's wonderfully detailed write-up of these speakers:

http://zaphaudio.com/SR71.html

So I ordered the "parts only" kit from Madisound... as much as I would have liked to build the crossovers from scratch, it was tough to pass up the 10% discount on all of the parts (including drivers) by buying the kit... I'll still have to solder up the crossovers, so I'll have some fun doing that...



I'll be building the cabinets from scratch, more or less exactly to Zaph's specs, so they'll look very much like these, only painted... not sure what color yet. The only other changes I'll be making is to make slightly thicker baffles (1.25" instead of 1"), and a bit more bracing.



So here we have the top of the cabinet being glued to one of the sides... in my opinion these first clamp-ups are the most crucial... get these nice and square and the rest of the cabinets will come together beautifully... the corner clamps shown here are an absolute godsend for this... sold for about $9 each at home depot... best $18 you'll ever spend... the clamp at the top of the picture is simply holding the assembly to a heavy iron right angle we have lying around the shop, so that I can hang the whole thing off theedge of the table, which makes it much easier to use the second right angle clamp underneath...



And now the bottom of the cabinet clamped up...



Here we have 2 layers of MDF (one .75" piece and one .5" piece) clamped up to make nice thick 1.25" baffles. I've made the baffles 1/8" bigger all the way around than the rest of the cabs, to be cleaned up later with a flush router bit. I'll also be routing a substantial chamfer on the back edge of the woofer hole so that the thick baffle doesn't interfere with the woofers...



Here we have a couple pictures of my secret weapon helping me glue up and clamp the other side walls on... this is the first time he's helped me build speakers and he's already got a full-blown case of the DIY bug...





While we're on the topic of gluing, a couple of pointers for anyone new to this...

- Do a dry run, at least in your head, of exactly how it's going to fit together, and how you're going to clamp it. Have all your clamps, wood blocks, etc ready. Know the sequence of which clamps are going on when. You'd be amazed at how quickly the glue will set up... you really don't want to be scrambling to find another clamp, or another block of wood to protect the surface your clamping etc, in the heat of the moment when the parts are already together...

- Always spread glue on both surfaces. I like to use a small brush to spread the glue. Spread enough to cover the surface thoroughly, but not so much that it's going to squish out all over the place and make a mess.

- If your clamps don't have rubber feet on them, use scraps of MDF to protect the panels... you can secure these scraps to the clamps using double sided tape, the thick masking-tape-like stuff. Do NOT just have loose floating blocks that you're trying to line up in the heat of the moment. This is such a pain in the keester. I've learned this the hard way. See the next picture, where I have scraps double-stick taped to the clamps.

- I'm a huge fan of Titebond III wood glue, because you only have to clamp it for 30 minutes... yes, that's right, only 30 minutes. Anyone who says otherwise is an old fart clinging to old wisdom ... the technology has improved. End of story.

Here's a close-up of it all clamped up...





Oh yeah... nice and square baby...



Here we have the horizontal braces stacked up in pairs with double-stick tape, and cut out with a bandsaw... I printed out the shapes from Solidworks and stuck it to the mdf with spray mount...



Here we have the horizontal braces glued and clamped... you can see here why I wanted to put the braces in prior to gluing the rear baffle on, as it allowed me to get some good clamping force on the braces... I also put a 1/4" radius on the edges of the braces (don't ask me why, it just looks nice).

The 4th leg on the upper horizontal brace (the lower one only has 3 legs) will attach to the front baffle between the drivers.



Here we have the vertical braces in place. I used 3/4" oak dowels, each one carefully sanded to a very tight fit. So tight in fact that I didn't even bother clamping.

There are two vertical braces tying to the top, as opposed to only one on the bottom, to allow for the port... they will also allow me to support the port later, probably with hot glue.

This arrangement of braces seemed like the most efficient way to support all of the walls while using a minimum of material and having a minimal impact on the internal volume.





More to follow...

[wkhanna]

What a great way to get in some ‘quality time’ with your boy!

Those are some well built cabinets. ;x(

[Jed]

Sweet braces! Very nice build

[gonar]

The only other changes I'll be making is to make slightly thicker baffles (1.25" instead of 1"), and I'm going to have the drivers be slightly closer together. Doubtful that these theoretical upgrades would make any difference that I'd be able to discern, but what the hey.

hmm, I thought that distance between drivers was very important to phase matching in the crossover, and directly related to xover frequency.

considering how picky Zaph seems to be about getting all those details exactly right, I wonder if changing it like that is wise?

[lunchmoney]

hmm, I thought that distance between drivers was very important to phase matching in the crossover, and directly related to xover frequency.

considering how picky Zaph seems to be about getting all those details exactly right, I wonder if changing it like that is wise?

Good point... I wrote that part days ago (this thread is a condensed version of a longer thread on the PE forum), and have since decided not to alter the spacing of the drivers... just deleted that part from the original post.

[lunchmoney]

What a great way to get in some ‘quality time’ with your boy!

Those are some well built cabinets. ;x(

Thanks

Really looking forward to the look on his face when he hears them for the first time... a fun lesson in how working hard and doing a good job yields great results.

[kevinp.]

Good point... I wrote that part days ago (this thread is a condensed version of a longer thread on the PE forum), and have since decided not to alter the spacing of the drivers... just deleted that part from the original post.

I understand there are issues with spacing drivers too far based on x-over point, but are there really negative effects of spacing drivers closer? Can someone explain/clarify that?

BTW, very nice work lunch!

[Jed]

I understand there are issues with spacing drivers too far based on x-over point, but are there really negative effects of spacing drivers closer? Can someone explain/clarify that?

BTW, very nice work lunch!

Any deviation from the original driver layout from which the crossover was developed will introduce a slightly different diffraction signature, which in turn will cause a difference in the FR.

[nmuntz]

Those clamps you have that hold the sides square are an awesome idea. I've never seen those before. I need to get some of those for whatever my next project is.

[lunchmoney]

Those clamps you have that hold the sides square are an awesome idea. I've never seen those before. I need to get some of those for whatever my next project is.

Yeah, they really are a great tool.... $9 each at home depot. Get at least 4 of them.

[Rolex]

am I the only one that can't see the photos? The first two show up. After that, nothing..

[Bill Schneider]

I see them. I tired several minutes after you left your message, so if there was a server issue it was resolved quickly. It appears that Photo-bucket is hosting the pictures you can't see.

[Rolex]

Yes, the ones I cannot see are photo-bucket images. Is that a problem on my end? I have not had this issue with photo-bucket before.

[b_force]

great, keep up to good work

tip:
Try to remove the glue directly when you use it.

It is sometimes difficult to sand it of or (in worst case) you can see it through the paint.

[tubbsbright]

What's wrong lunchmoney? This build thread wasn't getting enough attention at PE for you?

(I'm just lashing out with sarcasm because I'm jealous of your wood-working and your shop )

[lunchmoney]

great, keep up to good work

tip:
Try to remove the glue directly when you use it.

It is sometimes difficult to sand it of or (in worst case) you can see it through the paint.

Yeah, I should be better about that :roll:

Although I haven't had any difficulty sanding thru it it the past, and I plan on veneering these anyways.

Thanks

[lunchmoney]

What's wrong lunchmoney? This build thread wasn't getting enough attention at PE for you?

(I'm just lashing out with sarcasm because I'm jealous of your wood-working and your shop )

I'm going to enjoy imagining the look on your face 8O when I post pictures of cutting the driver holes and recesses on a rotary table mounted on a milling machine

:B

[tubbsbright]

I'm going to enjoy imagining the look on your face 8O when I post pictures of cutting the driver holes and recesses on a rotary table mounted on a milling machine

:B

I have no idea what a a rotary table mounted on a milling machine looks like, so make sure you label it so I know what I'll be looking at.

What type of veneer are you going to use?
I thought the blue on your tritix's looked pretty good.

[b_force]

With veneer you have less problems, but you can have problems if the corners are not 45 degrees. You may see the little lines.

The glue with paint is just a disaster :cry:

[lunchmoney]

The glue with paint is just a disaster :cry:

Not if you paint them correctly

I don't think it's a big deal at all to have a little bit of wood glue mess prior to painting... just sand down the offending wood glue a bit, then seal the mdf, a good few coats of primer, sand again, then paint... here are a few pics of my last speakers, sloppy wood glue and all... the paint came out as good as you could hope for...

[b_force]

Nice finishing

I've always problems with the joints.
You can always see them through the paint.

I use Motip, very well (Dutch) performing paint.

[bobhowell]

I have been planning to build these in a few months. Are the beefed up baffles important?

[lunchmoney]

I have been planning to build these in a few months. Are the beefed up baffles important?

Depends who you ask.

There are those who think that a vented cabinet of this size would be just fine with ¾” mdf all around and no braces...

On the other hand, there are those who think it should be 2-inch thick concrete with 15 lbs of steel bracing inside.

I think my approach is somewhere in the middle, most likely a bit on the overkill side… but a bit of overkill makes me happy.

Here are a couple pics that were recently posted on the PE forum, from a very knowledgeable chap who firmly believes in going bananas with his bracing...

Image not available

Image not available

In theory it does make sense to me that going thicker certainly couldn’t hurt, to reduce resonance… I didn’t want to make the whole box that thick, as they would be getting absurdly heavy… but I figured “what the hey” and made the front baffle thicker, for two reasons:

1. The woofer is mounted to the front baffle, so it probably experiences more energy from the woofer than any other panel.
2. The front baffle can’t benefit from as much bracing as the other panels, since the woofer is in the way… this is likely a moot point though, since the woofers are extremely rigid and probably add support.

So will making the baffle thicker make a difference in SQ that anyone would notice? I have no idea, and will never know, because I’m only making one pair, and won’t be able to compare. My hunch is “probably not”. But it certainly won’t hurt, and as I said before a bit of overkill makes me happy.

This probably did nothing to answer your question. :roll:

[b_force]

Ehm, ok, I will try to explain this in English (hopefully you will understand it )

It really depends what you want to use the specific driver for.
According to the mass laws (read the book: Engineering noise, control for example), the panels must be as stiff as possible for the lower frequencies to get the highest transmission loss.
So your goal, for a woofer, is to get a high panel resonance frequency, because this frequency will not be triggered.
To improve the stiffness you can at materials that are more stiff, use round shapes (like a circle or tube) or at bracing to create more stiffness.

But whit a two way system you have a problem.
The best thing is to get panels resonances above your cross frequency, let's say 4kHz.
This is however practically almost impossible. Besides that, there are also some coincidence in the material which have a negative affect.

So for a mid range driver it would be better, according to the theory, to use double wall systems.
The extra benefit is the 18dB/oct instead of 6dB/oct (single wall), but it also has another problem, the resonance frequency between these two panels.

So you have to make these resonance as low as possible (for a 2 way BR system beneath 30Hz or so) and that is impossible with normal sizes.
For a 3 way system this would work great, because a resonance of 100Hz is possible to make.

Third there are some sandwich construction who are, I think, best of both worlds. (if used correctly, otherwise it will be worse)
But unfortunately the book does not go deeper in the theory.

So according to this theory, we have a problem with a 2 way system.

My suggestion is to at a little bit of bracing, but not to much. Just enough that the panels will not resonate to much. More bracing will probably not do anything better, but costs a lot of volume, work and off course money.

This is still according to the theory, what practically would be audible is something else.

[lunchmoney]

Machined the baffles today...

Here I did a printout from Solidworks, and taped it to the baffles to locate the holes with a centerpunch...



Small pilot holes drilled...



Counterbored holes for 8-32 Hurricane Nuts drilled with a .75" forstner bit...



.219" thru holes drilled for the Hurricane Nuts...



Now the fun part... I milled the driver holes and recesses using a rotary table on a milling machine... this method spanks using a plunger router... much more accurate, and harder to screw up...





The fuzz on the edge of the hole here had me concerned at first, but it sands off very easily with some 180 grit sandpaper...



Milling of the driver holes and recesses complete...









Here I added a 5/8" x 45 degree chamfer on the inside edge of the woofer holes with a router table to ensure that the woofers ventilate well...

[DeathMonk]

It sure would be nice to have that kind of equipment at my disposal

[LoopinFool]

It sure would be nice to have that kind of equipment at my disposal

Yeah, for my subwoofer I thought about doing something similar with a ShopSmith, a lazy susan, and some double-stick tape. I ended up free-handing it with a jigsaw (ugh).

- LoopinFool

[lunchmoney]

Everything I've done here can be done with a plunge router, a circle jig, and a hand drill... might not come out quite as well, but it doesn't need to.

[DeathMonk]

Everything I've done here can be done with a plunge router, a circle jig, and a hand drill... might not come out quite as well, but it doesn't need to.

I know.. But look at how cool that stuff is!

[lunchmoney]

Milled the holes and recesses for the ports...



Sealed the backs of the rear walls with 70 wood glue/ 30 water... I've decided that you can easily go less diluted than 50/50, to reduce the amount of moisture introduced to the MDF (although I've never had a problem with 50/50)... I did this to the rear walls at this point because the ports are going to be glued in prior to finishing... you can also see where I drilled holes for Dayton spring-loaded terminals... I decided to use these terminals instead of the terminal cups that came with the kit, as I think the cups looks kind of cheap...



Sealed the insides of the baffles... note that I was careful not to seal around the edges where the glue joints will be...



Sanded the "ears" out of the tweeter holes to fit the tweeter's terminals... used a drum-sander table for this...



Now for the hurricane nuts... here's the technique I use, which has worked very well in the past... haven't had one strip on me yet...

First I put a little bit of wood glue on the barrel of the nut... the glue won't stick to the nut, but it will harden the MDF after the nut digs in...



Then I use a screw and an allen wrench to drawn the hurricane nuts in... the nuts actually screw there way into the MDF this way, and end up being very strong... DO NOT SIMPLY POUND THEM IN WITH A HAMMER... that's a sure way to end up with strippage... the nut shown in this picture is not actually threaded to the screw, it's just acting as a washer...



Hurricane nuts installed... I love how these baffles turned out... almost a shame to hide them when the baffles are glued on...





Ports glued to the rear walls with hot glue... tough to see, but I left a bit of a gap between the milled hole and the ports, to allow hot glue to get in there...



1.25" Sonic Barrier applied to the rear walls... this stuff is great to work with... cuts easily on a band saw... the surface was sealed prior to sticking the Sonic Barrier on, which not only protects the mdf from moisture, but also makes the Sonic Barrier stick extremely well... note the holes left for the braces and terminals...



Sonic Barrier applied to the other walls... 1.25" on the bottom, .75" everywhere else... again the surfaces were sealed first... also sealed the braces (glue isn't dry yet, that's why it looks all blotchy on the braces)...





Rear walls glued and clamped... the blank piece on top is just a scrap of MDF for the clamps to bear on...



Inside flanges of the ports glued in...



Here you can see where I hot glued in a couple of little wedges of MDF to support the ports...



Front baffles glued and clamped...



All glued up... you can see that I left a bit of overhang with both the baffles and rear walls, to be cleaned up next with a flush trim router bit... (thanks to John Stockman on the PE forum for this trick!)...





Now for flushing up the edges... I used a long flush trim bit in a router table...









Next comes routing the corners and finishing... and the crossovers of course (external)...

[exojam]

Man I wish I could just cut a straight piece of wood, let alone make sweet cabinets like that.

[lunchmoney]

Man I wish I could just cut a straight piece of wood, let alone make sweet cabinets like that.

All you need is a circular saw, a straight edge to put it up against, a plunge router, lots of clamps, and maybe a jigsaw.

Might take a bit longer, but you don't need a shop like the one I'm using in order to get great results.

[exojam]

I was never a good wood worker before being in a wheelchair and now I really have a hard time (that damn MDF gets heavy quick). I spent about 4 hours just making a little sandbox for my turn table and still had a heck of a time and that was only four sides and a bottom! For me it was so much easier having Curt and Wayne make me a custom L-C-R setup.

I just like seeing folks make nice stuff in areas I cannot.

James

[thadman]

Those look fantastic! Great work!

[lunchmoney]

Smoothing out the seams is one of my favorite steps... makes a lot of dust, but very satisfying (yes I use a mask)... I used a palm sander with 60 grit...

This is where all the careful construction and the "overhang then flush trim" trick really pay off, as this only took a couple of minutes per face...





Roundovers next...

[bikedave]

Those are looking really good lunchmoney, I'll be interested to here how you think they compare to your Triunes.

Your shop is great, and its like you said, all you need is a jigsaw, circular saw and router to do it all. I know because that is my shop. But man, the right tools make the job go 10x faster! That vertical milling machine is great, you should turn it into a CNC! Check it out: http://www.diycnc.co.uk/html/my_project.html

[lunchmoney]

3/4" roundover on all of the vertical corners... it's remarkable how much smaller the cabinets look now as a result...

[lunchmoney]

Here's a picture of the cabinets being sealed with a mixture of wood glue and water, approximately 60/40... shown here are the bottoms being sealed, the sides and top are already sealed and dry... I used 2 coats on the entire cabinets, with an extra coat on the end grain and roundovers... they could probably soak up even more, but the heavy build primer that goes on next can certainly handle it from here...



Here I've cut the gaskets out of some thin closed-cell foam leftover from a car audio project... I cut out the screw holes using a hole punch and a mallet...

[lunchmoney]

Wiring plan for the crossovers... hopefully correct... anyone wanna double check me here? Pretty please?



Gluing up the columns for the stands... yes, they eventually got a 4th side...



Gluing up the tops of the stands (2 layers of 3/4" mdf)...



Tops glued and screwed to the columns... the 4 holes at the corners are for 1/2" PE spikes, facing up of course... the big hole in the middle is where I will eventually fill the columns with sand...





Bases for the stands next...

[lunchmoney]

Bases glued and screwed... you can also see the 1/2" PE spikes sticking out the top... same spikes also used pointing down from the base... the four holes in the corners of the bases will be filled with scraps of 1/2" dowel...



I milled four 1/4" holes, 1/4" deep, on the bottoms of the cabinets to simply act as locators for the spikes... I created the holes with a flat end mill, so there is no point at the bottom of the holes... the holes are just large enough in diameter that the spikes still bottom out on their points... this worked really well for locating the speakers on the stands... I've always hated the guessing game of trying to center speakers on stands...



Boy was this a satisfying moment ...

[lunchmoney]

Primered!









al... most... done... (gasp)...

[b_force]

Beautiful details!

Very nice

(and grey at the moment :P)

[lunchmoney]

Absurdly large crossovers complete... :roll:

[exojam]

Lunch,

Hopefully you do not mind me throwing out some questions to you. How long did it actually take you to build this whole setup? Where are you actually going to be placing the crossover box at?

By the way I think the everything looks very nice. I am always envious of folks like you who can take a piece of wood and make something like this. By the looks of things you have a very nice wood working shop but it still takes some skill in making use of the tools. Even if I had that kind of setup I could not make something like that.

James

[Bastek]

A pro box for a passive crossover? Wow! This can probably serve as a speaker base? Overkill is always better than underscore! Keep them coming! :T