Zaph SR71 Build Thread...

[lunchmoney]

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

Thanks James!

I've been slaving away at this project in my free time for about a month... gotta be a good 50 hours at this point.

The crossover box will reside in my components rack, right on top of my CD player.

[M.Roberts8]

Wow! very impressive build thread. Is that your personal shop? What kind of primer is that? I've tried painting mdf and so far have not been too happy with the results. I haven't built anything in a while this is getting me anxious to get back at it.

[lunchmoney]

Wow! very impressive build thread. Is that your personal shop? What kind of primer is that? I've tried painting mdf and so far have not been too happy with the results. I haven't built anything in a while this is getting me anxious to get back at it.

It's the prototype shop where I work.

It's 3-4 coats of high-build primer over 3-4 coats of a 50/50 wood glue/water mixture.

[lunchmoney]

The seam between the precision ports and the rear wall were being quite stubborn... after sanding, primer, and more sanding, the seams kept emerging... so I used some 3M Acryl-Green Spot Putty on the seam, then sanded, then more primer...



Here they are all sanded up with 400 grit, ready for paint... as you can see, the mdf poked through the primer here and there, but in my experience this isn't a big deal... I certainly didn't sand through the sealant underneath... it's smooth as glass even where the mdf poked through, and you absolutely can't feel any difference in the surface...





Here you can see that I finally did manage to make the seams around the ports disappear... this wasn't easy, and took a lot of patience... almost gave up on it, glad I didn't...

[ThomasW]

The crossover box will reside in my components rack, right on top of my CD player.

Not the best idea......

The leads from a passive crossover to the drivers should be as short as possible. Putting them on the floor below the speakers would be a good spot.

[lunchmoney]

Not the best idea......

The leads from a passive crossover to the drivers should be as short as possible. Putting them on the floor below the speakers would be a good spot.

Oh crap... really?

If I knew that, I would have put the crossovers in two different boxes, and put them near each speaker...

The crossover box I made was intended to be on the component rack, which is halfway between the two speakers.

Is this really a big deal?

[Dennis H]

Is this really a big deal?

I doubt it as long as you use decent sized wire to keep the DC resistance low. A resistive wire could change the transfer functions of the crossover a bit.

[lunchmoney]

They'll be 14 gauge wires, about 8-9' long.

[ThomasW]

How long is the run from the rack to the speakers?

[lunchmoney]

How long is the run from the rack to the speakers?

Just answered above ^^^

[ThomasW]

That's probably ok, I was afraid it was going to be 25' or something silly like that...

[lunchmoney]

Ok, good...

Ya know, in car audio it's done all the time... crossovers mounted in the trunk, with 12' runs going to the front speakers... I've never heard it mentioned as a concern... (that doesn't mean that it ISN'T a concern of course... all sorts of bad practices are done in car audio quite regularly)

Is there some way that I can measure different lengths of 14 gauge cable, to see if 9' is too long? I could compare it to a 3' run or something...

How would I measure it? Probably more complicated to figure out than just resistance with an ohmeter, right?

[ThomasW]

In home audio we're dealing with AC power ..... EMI/RFI are issues too

I'm not a fan of long runs of unshielded wire. So my thing is if needed .... long runs of shielded interconnects and short runs of speaker wires

[jkrutke]

Oh crap... really?

If I knew that, I would have put the crossovers in two different boxes, and put them near each speaker...

The crossover box I made was intended to be on the component rack, which is halfway between the two speakers.

Is this really a big deal?

One thing I would be a bit concerned about would be destructive interference between power supplies and the inductors in your crossover box. Keep the box away from other components and I bet it would be fine. I would only be guessing however about how far away is far enough.

[lunchmoney]

One thing I would be a bit concerned about would be destructive interference between power supplies and the inductors in your crossover box. Keep the box away from other components and I bet it would be fine. I would only be guessing however about how far away is far enough.

Thanks.

I could easily put it on the floor, underneath the component rack, and it would therefore be more than a foot away from any other power supply... that would shorten the wires by a couple of feet as well...

[ThomasW]

I could easily put it on the floor, underneath the component rack, and it would therefore be more than a foot away from any other power supply... that would shorten the wires by a couple of feet as well...

that's a good idea.... :T

[Dennis H]

Twisting does about the same thing as shielding. Easy to do with the apexjr mil-spec wire or you can buy the 12 ga. Belden from bluejeanscable pretty cheap. Note, I'd go with 2 pieces of the 2 conductor rather than the 1 piece of the 4 conductor star quad because you could get crosstalk between the the woofer and tweeter with the star quad.

http://www.bluejeanscable.com/store/speaker/index.htm

[lunchmoney]

Thanks.

Should the two pairs of wires going to each speaker be separated from one another? I was hoping I could simply bundle them with zip ties...

[Dennis H]

Bundling is okay as long as they are individually twisted. It's when all 4 wires are twisted together that you can get crosstalk. Some guys over at the Orion forum tested that stuff for different cables. With an 8 conductor cable for the 4 drivers you could make it work but you had to be careful how you hooked it up or you might get subwoofer signal bleeding into the tweeter -- not good.

[ThomasW]

This is a + step forward.

Will you hear a difference?

That's totally dependent on the quality of the everything in the playback chain. At least you know you've done nothing to hamper the playback SQ

[lunchmoney]

This is a + step forward.

Will you hear a difference?

That's totally dependent on the quality of the everything in the playback chain. At least you know you've done nothing to hamper the playback SQ

Thanks Thomas,

What's really interesting is that I'll be able to push the boxes back together, and see if I notice any difference.

[fbov]

The worst case would be stacking them, coil over coil. If you can't detect a difference between widely separate and stacked, you have nothing to worry about. I'd expect a loud signal in one could induce sound in the other if they were interacting. Don't know what else one might (readily) look for.
Frank

[lunchmoney]

Here you can see I found a solution to the old "how do you paint the bottoms" dilemma (ah yes, that old chestnut)... I made some simple pedestals with 3/16" steel rods, which fit right into the 1/4" recesses I milled to accept the spikes... this worked really well, allowing me to easilt paint the bottoms at the same time as the rest of the cabinets...





Here I'm installing the drivers... you can also see that I added a bit of stuffing behind the woofers... the braces worked great to hold the stuffing away from the woofers...

[lunchmoney]

And here they are finished!!!... well, almost... couldn't find black screws long enough for the tweeters, so those are on order... and I need to repaint the crossover boxes... and tidy up the cables... but whatever...

I've got them set up temporarily in a back room where I work... the lighting is very harsh, bright fluorescent... the burgundy looks much nicer under softer, warmer lighting (i.e. the room in my house where they'll live)... that's a buddy's drum set in the background...















Much better photos to follow when I get them into out makeshift photo studio here...

[lunchmoney]

So how do they sound? I'm never very good at this, as I don't speak audiophile...

I guess a good way to put it would be to compare them to the 22 liter vented Tritrix's I made... bear in mind that these aren't yet broken in yet...

Compared to the Tritrix's they are... well... better.

Much more detailed mids and bass. Much lower and fuller bass. They sound, well, bigger... despite being 2/3rds the volume of the Tritrix's.

The highs are extremely detailed without any harshness... very smooth and non-fatiguing.

Not sure what else to say about them, I'm too much of a noob to elaborate any further without talking out of my b*tt... other than to say that I'm just blown away by these. They're absolutely incredible. I'll post further impressions after they've broken in a bit.

[ThomasW]

So how do they sound? I'm never very good at this, as I don't speak audiophile.......

Compared to the Tritrix's they are... well... better.

Much more detailed mids and bass. Much lower and fuller bass. They sound, well, bigger... despite being 2/3rds the volume of the Tritrix's.

The highs are extremely detailed without any harshness... very smooth and non-fatiguing.

other than to say that I'm just blown away by these. They're absolutely incredible. I'll post further impressions after they've broken in a bit.

Nice job.... :T

'Audiophile' speak is describing what you hear. And it seems to me you did a fine job of that.

Perhaps now you know why we advocate for the use of higher end drivers ....

[lunchmoney]

Nice job.... :T

'Audiophile' speak is describing what you hear. And it seems to me you did a fine job of that.

Perhaps now you know why we advocate for the use of higher end drivers ....

Thanks... ya know, I did agonize for a while over whether to do fewer higher end drivers (TM)... or more lower end drivers (MTM or 3-way)...

In the end, my curiosity for higher end drivers, combined with less work involved, won out, thus I built these...

Although I'll always wonder how the Statement Monitors stack up against these... I'm guessing a bit better, but I've never heard them.

[JonW]

lunchmoney,

I have to say that this is one of the best build threads ever. :T You have lots of detail here for people to follow. Your workmanship and attention to detail are amazing. Second to none. Even for the little things that are inside and will never be seen once it’s all closed up. Heck, I’m impressed that you can glue up a square edge. (I’ve got those corner clamps but I’m still working on that skill here…) Glad to hear you really like the sound. :T

[exojam]

Lunch,

You have made a very good looking and from your thoughts and very good sounding speaker. Congratulations on a job well done.

Since I have no experience with wood working tools, I was looking at the first page where you were milling the holes and was wondering how the board was actually held down during this process.

James

[lunchmoney]

lunchmoney,

I have to say that this is one of the best build threads ever. :T You have lots of detail here for people to follow. Your workmanship and attention to detail are amazing. Second to none. Even for the little things that are inside and will never be seen once it’s all closed up. Heck, I’m impressed that you can glue up a square edge. (I’ve got those corner clamps but I’m still working on that skill here…) Glad to hear you really like the sound. :T

Thanks brother!

Your skills ain't too shabby either... those giant tapering bevels ya got there are incredible.

Hey, what led you to build such a high-end TM design?

With what you spent on those, you could have easily built very nice MTM's, or 3-ways, or line arrays, etc...

So why just a TM? Just curious, thanks.

[lunchmoney]

Lunch,

You have made a very good looking and from your thoughts and very good sounding speaker. Congratulations on a job well done.

Since I have no experience with wood working tools, I was looking at the first page where you were milling the holes and was wondering how the board was actually held down during this process.

James

Double stick masking tape holds them down, believe it or not... very common technique.

[JonW]

Thanks brother!

Your skills ain't too shabby either... those giant tapering bevels ya got there are incredible.

Hey, what led you to build such a high-end TM design?

With what you spent on those, you could have easily built very nice MTM's, or 3-ways, or line arrays, etc...

So why just a TM? Just curious, thanks.

Thanks man. I just made the slanty cabinets because I can't glue up a straight box.

Those speakers were my first design attempt. So best to stick to a simple MT design for a first run. And I knew I'd end up spending a lot of time trying to figure out how to make a speaker. So might as well use the good drivers. The expense isn't too bad considering it was the only project for 1.5+ years. And I tend toward a 'build it once' approach so I don't get an upgrade itch. It was a fun project, indeed.

Enjoy your new toys. :B Really, your workmanship there is amazing. :T

[jkrutke]

Nice job, and nice build thread. Impressive attention to detail. Not a MDF seam visible anywhere. I like the way you made the port look like it was molded into the cabinet.

I've got them set up temporarily in a back room where I work... the lighting is very harsh, bright fluorescent... the burgundy looks much nicer under softer, warmer lighting (i.e. the room in my house where they'll live)... that's a buddy's drum set in the background...

Someone's got a drum set at work? Heheh, I'd like to see the engineering dept where I work skid to a stop when I start pounding out an impression of Neil Peart on Tom Sawyer. (doh, I can't play the drums)

[lunchmoney]

Nice job, and nice build thread. Impressive attention to detail. Not a MDF seam visible anywhere. I like the way you made the port look like it was molded into the cabinet.

Thanks Zaph!

And also, of course, thanks for a great design! They sound incredible... all I did was build 'em...

For music, would you bother using a sub with these? They sound amazing run full range, but could maybe use a bit of low end grunt on certain tracks with very low bass... haven't decided yet if I'm going to bother with a sub...

But if I were to build a sub for these (probably a sealed 10"), at what freq would you recommend that I high-pass 'em? I know the answer depends on a number of different factors, but maybe you could recommend a ballpark starting point? Yes I would use an active crossover to high pass them...

Thanks!

[Cataclysm]

For music, would you bother using a sub with these? They sound amazing run full range, but could maybe use a bit of low end grunt on certain tracks with very low bass... haven't decided yet if I'm going to bother with a sub...

It depends on what you listen to and at what volume, but my SR71's run full-range get some spooky amounts of excursion when they unload below the tuning frequency.

Paired them with a 15" servo sub, never looked back.

[lunchmoney]

It depends on what you listen to and at what volume, but my SR71's run full-range get some spooky amounts of excursion when they unload below the tuning frequency.

Paired them with a 15" servo sub, never looked back.

At what freq did you high pass them? (assuming you high passed them)

[Cataclysm]

I let my Audessey Multi-EQ calibrate them, but I recall it crossing them over at 60hz.

[cray54]

Lunchmoney: awesome attention to detail in your builds. Also, awesome pictures (particularly of your blue speakers in post 20).

Out of curiosity, is there any documentation of a sealed version of the SR71 (I’ve noticed some of Zaph’s designs offer enclosure suggestions for both sealed and vented).

-Chris

[JonP]

Uh, just imagine Lunch's build thread, but with smaller boxes and no vents... :B

Really, if you keep the important dimensions the same, (width of baffle, spacing of drivers and distance from edges, length of baffle to a smaller extent) and reduce the volume by pulling in the depth and maybe a little of the height... you're there.

[cray54]

I found an answer to my question here:

https://www.htguide.com/forum/showpost.php?p=371813&postcount=31

On another note, I'm not going to recommend sealed with the SR71 design. I believe I may have listed it as an option with the L18 system, but in hindsight I probably should not have. Woofers with a Qts in the .3 range are destined to only work well in vented boxes.

[MT Speakers]

Any tips for milling the holes?

[lunchmoney]

Any tips for milling the holes?

The most common method is with a router and a Jasper Jig (circle cutting jig)... you can find them at parts-express.com

I used a milling machine of course, but not everyone has access to one of those.

[JonP]

The Jaspers are good... I have the 1-7 1/2" and the bigger one that goes >18". There are a few similar others out there like the Router Buddy, a Sears one that Zaph swears by.. and some make there own.

There were a few recent threads on this subject, on here and the PE forum, including some creative ways for a homebrewed one.

Bottom line, Jaspers are nice in that they have all the pre drilled holes, just put it on, (uh, the RIGHT hole) and around you go. Down side, you have a minimum of whole 1/16" measurments. Might be a bit too big or too tight, but a max 1/32" gap isn't that bad and it's often closer in my experience. Your driver may vary...

The adjustables as well as the home made ones can get to just about perfect, but their down side is the extra fussing to get them set dead on... or drilling the hole wrong or measuring wrong with the holes in a plate homemades...

[MT Speakers]

Here's my jig for making circles. I actually made it with my router. Works great.

[dlr]

Bottom line, Jaspers are nice in that they have all the pre drilled holes, just put it on, (uh, the RIGHT hole) and around you go. Down side, you have a minimum of whole 1/16" measurments. Might be a bit too big or too tight, but a max 1/32" gap isn't that bad and it's often closer in my experience. Your driver may vary...

If you really want a close fit, just use a 5/16" bit in place of the 1/4" and if it needs to be smaller rather than larger, back off one hole position. You get 1/32" settings this way.

Dave