Zaph|Audio Bargain Mini (ZBM4) HT Build

[liasom]

Building a 5.2 system (5 ZBM4s sealed and 2 sealed woofers) for a small room, a 2.0 system (2 ZBM4s sealed) for my dad's stereo AV system, and a 2.0 system (2 ZBM4s ported) for near field listening at a computer. My dad (he'll celebrate 82 soon) has some pretty bad hearing problems--mainly when there is complex or high amplitude low frequency information. That's why the sealed version for him and there may be some special tuning in room to get them dialed in for his listening pleasure.

I've been collecting parts here and there new and used for a while to get these done. I'll be using the MCM 55-3853 cast frame woofers. The .2 woofers for the 5.2 system are Peerless 830667 SLS 8" subwoofers. I'm building the crossovers with terminal strips installed so I can switch back and forth between the original crossover design and the reduced BSC option. Got a good deal on some 1.0 mH inductors. That will maybe help when finally setting everything up in the room, well at least give me some placement options without too much hassle.

If I've done my drawings and calculations right here's the size and tuning for the enclosures.

ZBM4 sealed version 3 liters F3 about 93Hz
ZBM4 ported version 4.8 liters tuned about 55 Hz
Peerless 830667 sealed 52 liters

Went to the wood store today for 2 sheets of 3/4" douglas fir marine plywood ($188.36) and a slab of douglas fir lumber is on the way via UPS from Oregon to Texas ($53.99) to mill solid 1/2" lumber for the face of the 2-piece baffles. The backs of the ZBM4 enclosures will be removable.

We chopped up the plywood today with a circular saw and created smaller and more manageable pieces for our newly made panel cutting sled. There certainly are a lot of pieces to cut for 11 boxes! Starting that tomorrow or on my Monday holiday.


The Douglas Fir Lumber for the Baffles


ZBM4 Baffle and Sealed Enclosure Side View


ZBM4 Back Brace and Ported Enclosure Side View


Peerless 830667 Woofer Enclosure (with a bracing idea sketch)

More to come...

[HareBrained]

I used the 3853 in an MTM, pair with the Vifa DQ25, and they play very nicely. But they don't surface mount as "nicely" as the 1853. Flush mounting is far more important with tweeters but you could have a little more raggedness in the midrange.

Changing the port location does have an impact on the port length because you've placed it within 1 diameter of the bottom. Your net tuning will be a little lower than desired. I would mount the port on the side, ensuring the interior end is more than 1 diameter from anything else.

Lastly, Zaph designed in 4db of baffle step compensation. This means you will have too much midbass for your nearfield and HT situations. But this will only become noticeable after the 3853's are broken in (~25 hours of playing). Overall, you may not notice or care, or you may like it that way. I'm just saying they weren't designed for how you're using them.

The bracing on the sub is interesting but technically, not as effective as perpendicular braces. And given that only you will ever see them, and only rarely at that, you might want to keep it simple for yourself.

[liasom]

Thanks, John!

I used the 3853 in an MTM, pair with the Vifa DQ25, and they play very nicely. But they don't surface mount as "nicely" as the 1853. Flush mounting is far more important with tweeters but you could have a little more raggedness in the midrange.

I'm making a router template to rabbet the baffle and flush mount the woofer. I have two different size drawings done for that and hopefully one of them will work. On paper they look pretty good. Oh well, if no-workee, back to DeltaCad for a resize. I think close/good enough will suffice for these woofer frames.

Changing the port location does have an impact on the port length because you've placed it within 1 diameter of the bottom. Your net tuning will be a little lower than desired. I would mount the port on the side, ensuring the interior end is more than 1 diameter from anything else.

I'd like to have the port on the front for aesthetic reasons. Also have read that port-on-the-front is good for near field use. I'm flexible on this. The ported stereo pair will be on mini-stands, so I could port them out through the bottom. Is having the port too close to the bottom surface of the enclosure going to cause any problems other than the tuning? I do have a couple of extra port tubes. Figured I'd need to dial in the port tuning to allow for calculation error anyway. I'd read on Zaph's website somewhere that most spreadsheets etc. indicate a higher tuning than what you wind up with. So they're actually tuned a little lower in reality than the calculations indicate.

Lastly, Zaph designed in 4db of baffle step compensation. This means you will have too much midbass for your nearfield and HT situations. But this will only become noticeable after the 3853's are broken in (~25 hours of playing). Overall, you may not notice or care, or you may like it that way. I'm just saying they weren't designed for how you're using them.

I read and viewed on Zaph's website that the 3853s have a little more output in the midbass. I'm hoping that by having my crossovers variable between the original version and the reduced BSC version that the tonal balance will be acceptable for near field use when I have them wired up for reduced BSC. I know the reduced BSC version is not optimal. For my dad's sealed versions the reduced BSC crossover might probably be used in any case. But maybe not. Depends on what he likes when he finally hears them. That's another reason for having both crossover versions on the same board. On the 5.1 build I think the L and R channels will be OK with the original crossover version as they will be on stands and away from the walls. Depending on the mounting of the C and the L/R surrounds I can fall back on the reduced BSC crossover if it sounds better.

The bracing on the sub is interesting but technically, not as effective as perpendicular braces. And given that only you will ever see them, and only rarely at that, you might want to keep it simple for yourself.

I hear ya on the KISS method! That was an idea inspired by a few doses of Shiner Bock :beer:. And that idea didn't get deleted before I posted. Meant to, but was too lazy by that time to do any editing. I likely will use a couple of 2x4s to brace side-to-side and one top-to-bottom and epoxy them in and also tie together in the middle area.

[liasom]

Cut some plywood today. Got all the pieces roughed out and then worked this afternoon on the tops and bottoms. They have a rabbet cut along each side to reduce the amount of edge showing after the glue up. Also to add a little more surface area for glue. A nice start to the morning. Not too hot here in Dallas. Afternoon though brought on Mr. SUN! :evil:




The panel cutting sled is a real good thing. Works great for repetitive cuts. Happy I decided to build one. Here's some photos of it mounted on dad's ShopSmith.





Made a tenoning jig to cut the face of the rabbet joints on the tops and bottoms. Didn't get a photo though. My camera was inside out if the heat.

[liasom]

Router Templates

These are a reverse print version to use so I can melt HP Superfine toner off of coated paper onto 1/2 inch MDF. I have a LaserJet 4MV printer that will do 11x17. Going to try to iron on the toner and then release the paper with a bit of acetone. 300dpi printing is done, but I need to experiment a little to get the transfer to happen. Suggestions are welcome if you've been down that road before. AND...more to come on that process.


To cut the rabbet for flush mounting the woofer.


To chamfer the plywood layer of the baffle around the woofer cutout. Leaves full thickness of 1 1/4 inches baffle for mounting the woofer using 8-32 hurricane nuts from PE. Plan is to perform the solid Douglas Fir baffle chamfer with a wood rasp or two, a few files, and some sandpaper. Dad has a varied and large collection of files...


For cutting the inside of the baffle for mounting the tweeter. Making a rear-side MDF "plug/bracket" to apply pressure to the rear of the tweeter to lock it in good and hopefully stiffen the baffle in that area.


For cutting the inside profile for the flange that will hold the hurricane nuts for the bolt-on-back of the enclosures.


Crossover board that will piggy-back mount onto the bolt-on-backs. This is for the sealed enclosure version only. I'm using two separate and smaller boards for the ported version that will mount on either side or top/bottom of the box. I purchased a new template follower router bit (1-1/4" IIRC). Looking forward to see how that bit works. I can think of a lot of things to use that for.

Off to see the fireworks! Dallas "screwed the pooch" and the official fireworks show is tonight, July 5. :letitout:

[BretH]

Not tooting any horn, but if you need protection for the tweeters here's what I did:

http://www.htguide.com/forum/showthread.php4?t=35143&highlight=bargain+mini

[---k---]

Looking good. I enjoy these threads with lots of complicated woodworking - I always learn something.

Just FYI, you can save yourself some effort and skip the hurricane nuts. Just use wood screw to hold the drivers in place.

[liasom]

Toner Transfer From Paper to Template

Earlier this morning I lightly sanded the surface of a piece of 1/2-inch MDF with 220-grit, stretched the paper as tight as I could, and stapled it above and below. Then set an iron on max heat and ironed it until the paper toasted in some places to a very light caramel color. That was mainly toward the middle of the template, I imagine the heat gets concentrated there. I think I made about five moderate speed passes over the paper with the iron from top to bottom and side to side. The heel of my iron covered about 1/2 of the surface for each pass and overlapped in the middle. After the whole thing cooled a bit I sliced off the paper with a utility knife. The paper released immediately, so I didn't need to use acetone like I was prepared to do. Glad for that because then this is pretty simple to do.


The MDF template with the remnants of the paper.


Detail of the toner transfer. It is more sharply focused than I can represent here. Not razor sharp, but close.

BTW the template in this post is to be used for flush mounting the woofer with a 3/4-inch OD template guide on the router and a 1/2-inch downcut spiral or a 1/2-inch straight cutting bit, whichever bit works best on my test piece of the baffle's solid wood layer. It's a group of 4 circular segments. The two "outlines" of the woofer frame are the path the guide will follow and the inner line represents the cut, there being a .125-inch allowance for the guide/bit combo. Note the center lines that appear above the dimension numbers. Those represent the center of each of the 4 circular segments that make up the path the guide will follow. One center mark each for the four. I'm hoping the 1/4-inch radius that will result at each corner works well for the actual woofer frame. I can always use a chisel to dress the corners if they need to be different. If the arcs look off when I eyeball my test baffle piece--having a woofer temporarily mounted on it--I'll need to make another template using a newly calculated radius for the 4 circular segments.

Note: These factory woofers may not have a high degree of symmetry when it comes to the frames. Since it is a cast frame I do suspect though that they are all 9 identical in their "offness" instead of being individually "off". I'll test fit a couple before doing the real baffles and then during the running of the 9-speaker assembly line I can rotate the orientation of each woofer to best match the rabbet and the holes.

Now, among all the other things to do..., I need to do the transfer process for the other 4 templates. For the others I have a buddy with a scroll saw or dad may want to work on these to machine the MDF into the real templates. Probably will be able to do them with a jigsaw, his collection of files, and all the other tools he has that are known and unknown to me.

[liasom]

Not tooting any horn, but if you need protection for the tweeters here's what I did:

http://www.htguide.com/forum/showthr...t=bargain+mini

Protecting the dome on the NT1 yet having the least impact on sound is definitely a goal for my project. When I saw your original post a while back I put your idea on the list and it is a very good one. I have some silver grill cloth that I'm going to try using your method.

Another material I've found that I want to try is an ultra fine synthetic mesh that I salvaged from a bow on a gift basket. The stuff I have is very bright red. If it works and I choose it, I'd need to try to find a different color.

Updated 5/2/2010 - See post 26 for information on tulle fabric, the fine mesh I've mentioned above. -Mike

[stangbat]

Thanks for posting this. Nice work and nice information.

[liasom]

Looking good. I enjoy these threads with lots of complicated woodworking - I always learn something.

Thanks for posting this. Nice work and nice information.

I've built a few things out of wood over the last 35-40 years. Mainly utilitarian stuff. Never anything that could be described as fine woodworking. So I decided to change that. My clandestine goal is to get good enough at this "hobby" to tackle a few home improvement projects for myself--and yeah, build some more enclosures. Oh, and now I can invest in a collection of good basic tools. My most recent purchase is one of the Craftsman 21829 table saws and a couple of Freud TK806 (80T, $30) blades from the Rockler online outlet. The TK806 is what I cut the marine ply with on Monday and it did a fantastic job--that blade on the ShopSmith was a Father's Day gift for my dad and I'll replace it with a new one when we're done cutting for this project. The first cut I made with it was crosscutting some oak for dad's panel cutting sled and it was a very smooth result. The end-grain wood looked almost ready to finish.

The basic carpentry is no problem for me, but things like this speaker project need a couple of different skill sets and I need to develop those broad skills. I used to hang out with my grandfather, Everett, back in the 1960s. Everett was a guy's guy that could do just about anything. He told me that "finish" carpentry was something special and then he showed me why. He and I watched the two other men that were on his 3-man crew building a house on the same block I lived on--I got to spend a lot of time helping and watching. And I mean building a home. Everything started out as a pile of stuff and then ended up being a house--they manufactured almost all of that house. Anyway his boss, Ervin Frierson, was a wizard with wood. Ervin was also into model airplane building and competition. I watched and learned much from him.

[liasom]

Just FYI, you can save yourself some effort and skip the hurricane nuts. Just use wood screw to hold the drivers in place.

Good idea! Also a plain chamfer, by not having the huge protrusions into the chamfered area for mounting the hurricane nuts, would likely mean far better airflow around the back-side of the small woofer. Douglas fir is a softer wood so I'd still like to leave something there to fully support a longish pan-head wood screw. All I'd need to do is modify my template to make a little bit of a bump-out for them instead of the larger one for the nuts. Maybe brush a little thinned epoxy into the hole with a pipe cleaner to harden the fir. Sounds like a winner! I love collaboration.

Uh oh, now I need to find a tapered drill bit for those wood screws...I wonder if dad has one?

[JonP]

When I did a few pairs of Zaph's B3S boxes I made little triangular blocks of Baltic Birch, (any hardwood would do) and epoxyed them to the 45 deg chamfer I put on the back side. The B3S's are even more of a case of small driver with little ventilation needing a big cut in the back of the baffle.

The little cut off corner blocks lay perfectly on the 45 deg angle, and provide a full baffle's thickness in a thin spot, just big enough for the wood screw. Much less space taken up than routing around some kind of insert, so it leaves a maximum of open area.

I've made the ZBM4's as well, in a 5/8" Baltic Birch box. I was comfortable with just wood screws in the chamfered baffle, the MCM 4's aren't THAT heavy, and BB is pretty tough. MDF, I might have added the blocks for extra security. Would also add toughness to the screw threads, would last a lot longer without stripping, too...

Cool idea with the printer toner transfer. What kind of paper did you use, exactly? Been meaning to try that to transfer a graphic to wood, to see how well it might look...

[liasom]

Cool idea with the printer toner transfer. What kind of paper did you use, exactly? Been meaning to try that to transfer a graphic to wood, to see how well it might look...

Paper is nekoosa, Coated Premium Digital, 80# Gloss Text, 60001.

[liasom]

Spent some of the weekend doing stuff with dad and wanted to update the thread.

But first let me introduce you to my dad, Jim. He really mugged it for this photo.


He's a retired Pharmacist. He used to train Pharmacy Techs from the local High School's training program. That award on the back wall is one he got from the school.

Friday

Friday evening dad and I got out our chisels and cleaned up the inside corners of the rabbet cuts in each top and bottom piece.

Saturday

I used a homemade sanding jig to clean up the cheek cut of each rabbet in the top and bottom pieces. They looked good before sanding--only light saw marks--so this was to insure parallelism for the geometry of the cut and the same depth to the original surface of the plywood. Not much wood was removed by the sanding. When I'm finished with the boxes I'll make a post for all the jigs in their final versions. Laid out all the parts to view the grain of each top and side piece and sorted them into sets for each enclosure. Didn't try to do any close matching, simply looked at the overall characteristic of the grain and matched that up as best as I could.

Sunday

In the late afternoon I took a second look at the sets sorted by grain layout and made a couple of changes, then labeled each piece and its orientation with a sharpie. Then we got out the table saw and the panel cutting sled and cut down the plywood sides, baffle pieces, and back flanges to final dimensions. I was able to increase the inside height of the ported version by .5 inches, so now there can be better clearance from the port to the bottom of the enclosure. All that is left to cut to size are the bolt-on backs. I'll do those during final assembly.


A box from Sunday night. Sealed version. Router work starts after this.

Monday

This morning I used a table mounted router to mill the plywood tops, bottoms, and sides. This was to make the .25 inch wide by .125 inch deep dado that the front and back pieces will fit in. Got all those done.

Next I'll mill a rabbet all around the edges of the baffle pieces and the back flanges that will fit in the dado. I needed to set up the adjustable fence for those cuts and ran out of time this morning.

[liasom]

This morning I set up the router table, with the adjustable fence, and used a 3/4-inch straight cut bit to mill rabbets all around the baffle and back flanges. The slight gaps are because the part of the plywood that goes into the dado stands a little-tiny-bit proud by design. Some 100 grit sandpaper during a dry fit of each enclosure prior to glue up should take care of that.

The tops and bottoms also stand proud of the sides. I'll trim those flush after glue up. I managed to cut a few divots and splinter a little bit of the face veneer on the plywood, but I wasn't using my best router blade on this. Didn't want to tear up a "best" bit cutting on the glue in the plywood. All of that fuzzy woodworking will be either inside the box or underneath another part of the enclosure anyway.

[Mazeroth]

Very cool toner transfer idea. It amazes me the capabilities and cool ideas of the people that post on this forum.

Also, I love the picture of your dad. Reminds me of mine! He has a Shop Smith as well, though, rarely uses it.

[liasom]

Solid Douglas Fir Baffles


Before Milling

I don't have a bandsaw, sander, or planer and definitely can't afford to buy ones as good as WoodWorld in Richardson, TX has. So I dropped off the piece of solid Douglas Fir there to have it resawn and sanded into four 1/2-inch boards. The final thickness dimension may be a little less then 1/2-inch, but I need four boards to book match each baffle down the center (see photoshopped example below). I'm in the production queue, but spoke with Mike, the expert doing the work, and told him I wasn't in a hurry, just wanted them as close to 1/2-inch as he could get. Should be able to adjust for that dimension being different from the drawings without too much trouble. That will mean changing the template for the woofer cutout in the plywood--it needs to be changed anyway because of swapping out hurricane nut fasteners in favor of wood screws to secure the MCM driver. So, taking a little break from that part of the project.



A Photoshopped Book Match

FYI here's stuff I found about Douglas Fir:
To me the most interesting was from Fine Woodworking. Scroll up for the beginning of the article. Looks like a good book to have, so it's in my Amazon cart now.
From an old Popular Mechanics.
From Western Wood Products Association.


Back To The Project
Dad and I made plans last night to get together this weekend and cut the wood for the woofer boxes. 100 degree temps and high humidity here in Dallas for that. So we'll be putting some more "sweat equity" into the project.

[liasom]

Book Matching the Solid Douglas Fir Baffles

This is the initial photoshop version of a book match plan for the baffles.



The four 1/2-inch slices of solid fir look great after resawing and sanding. I thought it best to visualize before we cut and reach a point of no turning back. I "reassembled" the 4 pieces into the order they were before milling and took some digital photos. Then used photoshop to slice and put them in a book match order. Color is a bit off and the contrast is pretty flat, but this gives at least an idea of what is going on in the wood. I really like the way the first two from the left look with the darker tone in the middle changing to a lighter tone on the outside. In reality the first on the left is almost as dark in the middle as the second from left, but the photo didn't get that. We can adjust the width of the darker tone to match better when cutting. Five of those will likely be the set for the 5.2 setup.

[liasom]

Project Report

Worked on the router templates today. Got two of them (crossover board and back flange) ready to paint with wood hardener. After that a final sanding and they'll be ready to go. Oh, yeah, the square corner on the crossover board is a stupid idea--like I'd need a reference to make sure all the crossovers were oriented the same. ops: I'm going to cut it like the other 4 corners next time I have the jigsaw out.



Dad and I cut the panels to size for the woofer boxes on Saturday a week ago and then this last Saturday worked to cut the rabbets for the top/bottom pieces and the baffles. The baffles didn't turn out as expected. In hindsight I wish I'd used the router table like I did on the ZBM4s, but we thought it would be OK to use dad's stacked dado cutter. Got quite a bit of tearout in the third layer of plywood when running it across the grain.



Had planned to leave some of the the edge exposed and chamfer the edges of the baffle all around (like on the top/bottom to sides interface). But, in light of how bad the glue joint would be looking now--and it really isn't a good surface for glue--I'm rethinking how to put the woofer box baffles right. No problem changing the plan because the face of the rabbet cut fits right on the inside of the box. I may make them flush and do some trim all around out of solid fir. I think that would look OK. Maybe better than the original plan.

Also, there is a problem with the table on the ShopSmith. Discovered it when doing some horizontal boring for another project. Seems to be cupped a little in the center or may just be out of level. Anyway we're going to check that setup next time we have it out.

Been making up sample boards for various finishes on the plywood. Tomorrow morning dad and I are going to cut and join the solid fir for the book matched baffles for the 9 ZBM4s. Need concentration on the details for that. No turning back once that cutting starts. Then I'll have some scraps to make up sample boards for finishing the baffles.

More to come...

[liasom]

Rant

The surfaces of the ShopSmith jointer my dad has are not parallel and there is absolutely no way to make an adjustment. The part of the infeed side of the table closest to the cutter head is lower than the back part. Double and triple checked it with a good straightedge, even dad could see the variance. So every time you make a pass you're cutting a taper. We tried one board and over the 36-inch length of the board we cut off about 1/4-inch of the end we were feeding first before getting close to having a nice straight side. That is a problem since I'm trying to book match the boards. I didn't have my router table and fence with me or I could have used it as a jointer. So we have to wait until next week when I can take my router and table over to his house to continue with making the baffles.



The ShopSmith jointer seems to be a good simple design with few parts. The thing has obviously gone through several machining steps during production. It's a shame that whoever machined this one got it wrong. :rant:

[benchtester]

Rant

The surfaces of the ShopSmith jointer my dad has are not parallel and there is absolutely no way to make an adjustment. The part of the infeed side of the table closest to the cutter head is lower than the back part.

Yes you are correct about the step, however this is how it is designed. One holds the board flush with the infeed table. Then feed it past the cutter. The cutter should remove a thickness of wood equal to the step height of the outfeed table. So now the board can feed parallel to the outfeed. Without the step there would be some rocking and the board wouldn't be straight along it's length.

Nice work on the speakers and the build thread. :T

[liasom]

Yes you are correct about the step, however this is how it is designed. One holds the board flush with the infeed table. Then feed it past the cutter. The cutter should remove a thickness of wood equal to the step height of the outfeed table. So now the board can feed parallel to the outfeed. Without the step there would be some rocking and the board wouldn't be straight along it's length.

Dad and I discussed it and were fairly certain we were using it correctly and it wasn't our error. We'd each tried making the pass through the jointer and made sure we were feeding using the outfeed as reference surface. Then we examined the tool to see what was going on.

I should have been more detailed in my description of the problem and illustration. The infeed table is not parallel along its length to the outfeed along its length no matter if it is stepped down 1/8 inch or almost flush.

Or to say it another way, the steps aren't parallel.

The part of the infeed that is nearest the cutter head needs to be slightly higher or the part farthest away slightly lower to make the infeed and outfeed tables parallel to each other. We put a straightedge along the length of the outfeed table and using the bright Texas sunlight shining through the gap raised the infeed until part of it touched the straightedge and the light disappeared. There was still light shining through near the cutter. Did it twice to verifiy that it isn't aligned properly. So that's our problem. Say we set up the jointer to make a hair width cut on a board that was already perfectly straight. When you feed along the infeed and past the cutter head the end of the board that goes over the cutter last would not even get cut until you made your second or third (or more) cut. All the thing can do like it is now is make successive tapered cuts until you get far enough along to make the whole edge straight (if you even get to that point before you make a curved edge).

Dad has rarely used the jointer on boards of any length over maybe 12-14 inches and wasn't trying to book match the grain so he never really paid any attention to how it was working.

[benchtester]

Sounds like you have a problem. Both tables should be parallel. Any way to unbolt one and shim one end?

[liasom]

Found some photos of a ShopSmith jointer for sale and and pasted them together to show the main parts of the jointer table assembly.



There doesn't appear to be any way to add a shim and keep the assembly operating like it should. The jointer is made up of two main pieces - infeed table and outfeed table/cutter head assembly. The infeed slides up and down a "ramp" that changes the height with a screw mechanism. The surfaces that mate to form the sliding mechanism are machined on both pieces.

We examined the owners manual and confirmed that there are no adjustable parts to change the geometry of either table. I suggested dad take it to a machine shop and have them measure parallelism of the tables and then mill the top of the infeed table to make it level with the outfeed. That looks like the only good solution to me and I've offered to split the cost, but I really have no idea what that cost would be. We may be able to purchase a used one locally (after close inspection) and get it cheaper than doing any work on this one.

Dad wasn't convinced* and he's going to call ShopSmith on Monday. They may have a solution. In the meantime I'll just use my router table to do the work on the baffles.

One thought occurred to me as I was doing this post. I wonder if the surfaces of the "ramp" just need a good cleaning? Dad recently replaced the bearings in the cutter head and maybe he tore it down that far. I'll ask.

*OT - Dad may be a graduate of the "Red Green School of Engineering". Although his professors would have been teaching methods that predated the widespread use of duct tape.

[liasom]

Aura NT1 Tweeter Protection, An Update to Posts 6 and 9

Not tooting any horn, but if you need protection for the tweeters here's what I did:

http://www.htguide.com/forum/showthr...t=bargain+mini

Thanks to BretH for his original idea.

Protecting the dome on the NT1 yet having the least impact on sound is definitely a goal for my project. When I saw your original post a while back I put your idea on the list and it is a very good one. I have some silver grill cloth that I'm going to try using your method.

Another material I've found that I want to try is an ultra fine synthetic mesh that I salvaged from a bow on a gift basket. The stuff I have is very bright red. If it works and I choose it, I'd need to try to find a different color.

I went to the fabric store last Friday with the bright red sample and found what I was hoping for. Here is a macro closeup photo of nylon tulle in matte black. They had both matte and shiny. I purchased a yard of the fabric for like $1.20. Silly. That's enough to do about 87 of the ZBM4s. It's very strong and fairly rigid once you get it pulled tight. I've pulled, stretched, and punched at it with my finger. As long as I can get, and keep, it stretched tight across the NT1 tweeter after mounting I'm confident it will work to protect the dome from accidental or moderate finger intrusion.



Looks pretty good on top of the NT1 in this next photo. In person it is almost invisible depending on how the light shines on it. Because it is so finely spun and woven I don't expect any significant change in the performance of the tweeter.

[liasom]

Glue! (At Last)

Worked through and around the jointer problem and was able to get a joint that had about a 1/32 to 1/16 inch gap in the middle with the ends tight against each other. Dad and I adjusted the cutter head to raise the blades a bit and that solved 80% of the problem. He also cleaned and tightened the infeed table. The jointer isn't operating perfectly, but is way better than before. I still think the parallelism is a bit wonky. But given the slight flexibility of Douglas Fir at 1/2 inch thickness it's good enough to get this done.


Made these blocks to use for clamping so that glue doesn't get smashed into the face side of the baffle during glue up.


Used a doweling jig to insert dowels into the joint at each end and at the places where the woofer cutouts will be. This was only to aid in aligning the joint. The clamps are what really flatten it out.


Used a large scrap of pine scavenged from the side of the road to hold the bar clamps in place with some cable ties. I think the scrap was from a demolished kitchen cabinet. A fortunate find. This was so I could easily transfer the whole thing inside to dry for at least 12 hours before unclamping.


Top view of the assembly ready to dry.


Two down and two to go. It isn't a perfect book match. But that was almost impossible to do because of outsourcing the resawing and sanding to make the 1/2 inch thick boards. I was able to adjust the match at the center some during the cuts for joining. I had to focus on the overall symmetry though. Also, when these are cut down to individual baffles the center glue line will be the center line of the baffle. That way the symmetry of the grain will be OK. Well, as OK as it gets.

OT :sn

It is disgustingly hot and humid here in Dallas. But no rain. My garden is cooked. :M The only time of the day to get any work done outside is from sunrise to about 10 a.m. Today will be our 18th day in a row with a high temperature above 100 degrees F. At night the lows are hovering around 80 degrees F. The heat index yesterday was 113 degrees F at 3 p.m. NASTY!

[liasom]

Slowly There's More

I need to create more time for this. Opera season began in August and continues through April 2011. I've been able to get a few things done but not finding extra time to post. Beginning today and lasting through Saturday (with a few hours possible on Sunday afternoon) is the first time I've had a decent run of days to work on this.

Happy Thanksgiving! Go Cowboys! HAA Haa haaaaaaaaaa ha haaaa ha ha! Jerry, I only have one thought, but I'll keep it to myself since you already have the problem solved. Meh!

A thank you to Ryan in post #7 and JonP in post 13 for the advice about mounting the woofers. I have drawn and printed a new template to chamfer the plywood layer of the baffle around the woofer cutout. This is a change from the original template because I've dropped the idea of using hurricane nuts and bolts for the woofers. I got some black flat top washer head sheet metal screws for that so only need a bumpout in the chamfer to give them more plywood to bite.



ZBM4 enclosure braces are cut to final dimension. Also got the bracket to mount the tweeter completed and cut to final dimensions. That means the plywood parts are cut to final dimensions now for the 7 ZBM4 enclosures except for the removable back sides. I will fit them to each box after assembly and applying the edge trim to the plywood on the back. Now on to machining the parts with the router and drill press and then assembly.



This is the LCR baffle set. All the Douglas Fir baffles are cut to rough size and ready for preassembly to the box and machining the driver and port cutouts with the router and drill press. I have the word out to my friends that I need to find a drill press to get some time on. Tried and then determined Dad's ShopSmith has too much runout as a drill press to do the tweeter hole. I may finish the baffles separately from the box. That depends on how I end up finishing the plywood boxes. In the future is assembly to the boxes and final dimensioning.


Surrounds L and R


Dad's L and R


Ported L and R

Things to do:

• Create time to work on this project. Yeah, right.
• Assemble my new cyclonic dust collector for router.
• Locate a drill press.
• Solve the woofer box final design.

[707kevin]

that's a crazy pile of cut ply

looking good!

[liasom]

Weekend Update


Dust Deputy collector is completed except for a finish (spray or brush depends on the winter wind) and some closed cell foam tape for the seal. Thank you! to Dad for the extra set of hands and a few tools. Made a box out of found lumber, hardware, and plywood to hold an old cat litter pail I salvaged from a friends recycling. Lift out and dump. No leaks.



Here's a sample finish for the plywood parts of the ZBM4 boxes--tops, sides, backs, bottoms. Wanted to see what something would look like. I dunno, but hey it is an idea. This is dyed using soy printers ink (black or blue) that stays pretty wet, so I left it soak in for a long while and then rubbed it dry with some paper towels and a little mineral spirits then left to dry well. Coated with several coats of very pale shellac with some light sanding in between some of the coats. The blue seems a bit darker in person. I think the ink is stable under the shellac, Not sure about UV fading or color shift though. I have red ink, but it's a brutal red. I have gold ink, but on a large surface it's the color of something found in a diaper. Yech!

I also have a sample without the dye, it's the same pale shellac with tung oil under half of it, but forgot to photo that one. Looks pretty good.



OT. Some of Dallas' fall color from right after sunset on Tuesday 11/23. That yellow tree is a majestic and healthy Elm that lives in my neighbors' (across the alley) back yard. It's got to be over 100 feet tall and it spreads out to cover some of both yards beside it. Leaves are mostly gone now with the Thanksgiving Day and weekend winds.


Figured out the woofer box. Doing drawing tonight for some jigs I'll need for assembly. I know I'll need several 90-45-45 degree triangular clamping jigs. May need something else for the ZBM4 boxes.


Looking for that drill press.

[liasom]

Question on Crossover Coil Placement

I'm planning the layout for the crossovers. I plan build both the normal crossover and the reduced BSC crossover on the same board. This requires two coils for the woofer section of the crossover, 1.0 mH and 1.5 mH. I looked at the tests done by Troels Gravesen and used that as a basis to test my layout, but using only one coil under test, since only one coil at a time will be in use for my woofer crossover circuit. When I tested no change resulted in the inductance or resistance value of the coil under test no matter where I placed the other coil.

So, my question is about the placement of those two coils. I want to place them close together, maybe even with one stacked on the other, like Figure 7 and 8 in Troels' test. What I don't know is if the two coils will interact, when placed like this, under dynamic conditions and result in either a change in the inductance or resistance values. Will they interact or not?

[1Michael]

The whole point of that website is to tell you to never do 7 or 8...
Never stack, separate my 20 centimeters is ideal, turn one on end.

[liasom]

The whole point of that website is to tell you to never do 7 or 8...
Never stack, separate my 20 centimeters is ideal, turn one on end.

I can definitely do the layout to separate the coils and I understand why it's needed, however it would be extremely simple if I could stack. Only reason I am asking is that for a single air core coil under test there is a change in inductance when I place a metal mass of any size near the coil in any configuration, like above, to the side, through the center...aluminum, brass, copper, steel...all change the value as I would expect and I assume the change in value varies with where the metal interacts with the magnetic field.

But there isn't a change in the value when I put another air core coil in proximity or even right on top. I'm curious about this so that's why I asked. I'm looking for a reason there is a different result for the test using a coil instead of a metal mass. I've tested both the 1 mH and the 1.5 mH coil placing one under test and the other to move around in the magnetic field and neither test results in a change in the value of the inductor under test.

[TacoD]

Toner Transfer From Paper to Template

Earlier this morning I lightly sanded the surface of a piece of 1/2-inch MDF with 220-grit, stretched the paper as tight as I could, and stapled it above and below. Then set an iron on max heat and ironed it until the paper toasted in some places to a very light caramel color. That was mainly toward the middle of the template, I imagine the heat gets concentrated there. I think I made about five moderate speed passes over the paper with the iron from top to bottom and side to side. The heel of my iron covered about 1/2 of the surface for each pass and overlapped in the middle. After the whole thing cooled a bit I sliced off the paper with a utility knife. The paper released immediately, so I didn't need to use acetone like I was prepared to do. Glad for that because then this is pretty simple to do.


The MDF template with the remnants of the paper.


Detail of the toner transfer. It is more sharply focused than I can represent here. Not razor sharp, but close.

BTW the template in this post is to be used for flush mounting the woofer with a 3/4-inch OD template guide on the router and a 1/2-inch downcut spiral or a 1/2-inch straight cutting bit, whichever bit works best on my test piece of the baffle's solid wood layer. It's a group of 4 circular segments. The two "outlines" of the woofer frame are the path the guide will follow and the inner line represents the cut, there being a .125-inch allowance for the guide/bit combo. Note the center lines that appear above the dimension numbers. Those represent the center of each of the 4 circular segments that make up the path the guide will follow. One center mark each for the four. I'm hoping the 1/4-inch radius that will result at each corner works well for the actual woofer frame. I can always use a chisel to dress the corners if they need to be different. If the arcs look off when I eyeball my test baffle piece--having a woofer temporarily mounted on it--I'll need to make another template using a newly calculated radius for the 4 circular segments.

Note: These factory woofers may not have a high degree of symmetry when it comes to the frames. Since it is a cast frame I do suspect though that they are all 9 identical in their "offness" instead of being individually "off". I'll test fit a couple before doing the real baffles and then during the running of the 9-speaker assembly line I can rotate the orientation of each woofer to best match the rabbet and the holes.

Now, among all the other things to do..., I need to do the transfer process for the other 4 templates. For the others I have a buddy with a scroll saw or dad may want to work on these to machine the MDF into the real templates. Probably will be able to do them with a jigsaw, his collection of files, and all the other tools he has that are known and unknown to me.

Thanks for this instruction! I was already wondering, I first checked the pictures, how you did that .

[liasom]

Thanks for this instruction! I was already wondering, I first checked the pictures, how you did that .

Other methods may work, but here's how I did the reverse printed templates. I used DeltaCad (cheap, works for me) to do the drawing. Set up DeltaCad and CutePDF (free!) to print the drawing at actual size/scale on tabloid paper (11x17) at 300dpi then printed to the CutePDF printer to create a PDF. Then I opened and rasterized the PDF at 300dpi in Photoshop. Using Photoshop I "flipped" the image horizontal. That resulted in an actual size image in reverse (negative) to iron on. Tweaked the image a bit to get the lines heavier. Think I had to change the image resolution to 150dpi to get it to print since my HP LaserJet 4 printer is like 15 years old and doesn't have a lot of juice for graphics processing.

I think some printer drivers will do a reverse/negative print by selecting that option in the printer setup. Mine doesn't, or at least I can't find that option.

[liasom]

Back at work now on the project. There was exceptionally brutal heat in Dallas this past summer. That made work in the afternoons and evenings impossible and unfortunately for me that was the only free time available. SO after clearing up my to do list of most all the homeowner things I was behind on...

Dad and I repaired his drill press so that issue is checked off my list. So, now everything left to do is up to having free time to work on this -- good news for me, looks like having time is OK for the next few months.

Testing Router Templates for Fit
I have all the router templates made and yesterday I used them to finish the construction of a couple of MDF baffles so I could check the fit of everything. Only one problem was revealed and it has to do with the mounting flange on the MCM 55-3853 woofers. The flanges are not all the same or at least on my woofers they aren't. Discovered that after I cut the rabbet on the first baffle and tried to fit several woofers. The irregularity is pronounced and there's no way I'm making a template for each driver. Pity because they would look really good as flush mounted. Thought about it while I was at work this morning and I've decided to just surface mount them and accept any diffraction issues that arise and the downgraded "look". :rant:


Here's the front of the test baffle with the now superfluous rabbet with one of the woofers sitting a little less than flush, but the driver has an integrated gasket so that was intentional.



Here's the test baffle rear with the rough cut chamfer. for the final versions all the hard edges will be smoothed out and the two blended together using a wood rasp and some sanding.


Crossover Prototype Layouts
Crossover board prototype layouts are done. I had to go through several versions before I got to these which seem to me to be OK. The sealed version is on a single board and the ported version on three -- needed to get the coils aligned properly.


Sealed crossover board prototype. This will mount on the rear of the enclosure.



Ported crossover boards prototype. Tweeter on left and woofer on right. Tweeter board will mount on the top of the enclosure and woofer board on the bottom. The coil that appears on the rightmost side is actually on the opposite side of where it will be in the final version - only needed to determine how far away from the other two coils it would be when mounted in the enclosure.

[joeybutts]

I think the issue with the flush mount is one of those, "man it really bugs the sht out of me, but who else notices" kinds of things. I think it will still look real good and barely affect performance as you have them. Maybe the angle I am looking at it isn't enough to deter me from flushing them like you have it.....

And great build. Wish I had enough desire to work at the skill you are....

[liasom]

"man it really bugs the sht out of me, but who else notices"

Yep. It's probably one of those things...

I've examined the test baffle when mated with all of the woofers and it seems to me there are two more or less distinct versions of the woofer frames. One is a bit smaller and curved a bit flatter on the bottom, so I'm going to take one of the larger frame versions and make a new router template by copying that. I had planned to paint the inside of the rabbet black before mounting the woofers and I imagine that the black paint will hide any imperfection in the fit of individual woofers. They are, after all, budget speakers. No need to go completely over the edge into total OCD, I think I can hold back from that! Hope to get to that this afternoon or over the next few days so I can finish up the test enclosures this weekend.

When I make the copy I'll likely use the method described in this diyAudio forum thread Flush mounting speakers: the whole story beginning at post #7.