dlneubec

After a 5-6 hour round trip to Shawn's neck of the woods, Union City Indiana, I now have the hardwood I will be using and the veneer.
I visted Frank Miller Lumber, which is a hardwood lumber company that has a great selection of hardwood and also hardwood plywood, all at very reasonable prices.

I took three samples of veneer with me to see what matched best, Burl Maple, Curly Walnut and and unknown darke red veneer that looks to be a Pomelle, all wood backed. After talking to the guys there and comparing the veneers to the hardwoods, we determined the dark red one to be Makore Pomelle. To match up with that veneer, which will be used on the boxes, I purchsed some Makore and Hickory. Below is a picture of the three together. These boards will be ripped and laminated on edge, so you won't see this side, but the egdes when the baffle is glued up. The bass bin baffles will be laminated to 1-1/2" thick and the hardwood portion of the open baffle 3/4" thick, making it about 1-1/4" when you include the Lexan on the front. I was warned to absolutely wear a respirator (not a dust mask) when working with the Makore (or just about any exotic). I got 10bf or Hickory and 12bf of Makore for about $100. Try getting something common like walnut, cherry or maple at Lowe's or Menards, etc. for that price!

So, Hope to start on the hardwood baffles for the bass bins and the hardwood/Lexan open baffles soon, perhaps next weekend.

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Dan N.

dlneubec

I’ve been working on the laminated panels for the bass bins and MT section. I didn’t want to take the time and trouble to do a bazillion biscuit joints so I created a little base to allow me to do a simpler edge glue up, using a combination of bar clamps and c-clamps. The bass bins use a ¼” hdf backing and 1-1/4” ripped stock, edge glued and glued to the ¼” backer, for a total of 1.5” thick. The MT section is ¾” ripped stock, edge glued only. Here are a series of photos showing how I set it up and some of the bass bind baffles. I will follow this post with a step by step for the MT baffles.

Up first, I used a piece of ¾” mdf and clamped side pieces to use as stops to forming the laminated panels. Double sided tape was placed on the side boards so glue would not stick. The side pieces were ripped a little smaller than the laminate depths.


I started with the bass bin baffles. I decided to do them in 3 sections because I was concerned glue would start to set before I got all the pieces in place. Here is the first section glued and clamped. The jaws of the bar clamps are too deep, so spacers are used between the bottom of the bar clamps and the laminated pieces (w/double sided tape on the bottom of the spacers). The spacers allowed c-clamps to be used on each side of the bar clamp to press the laminated pieces flat and against the ¼” hdf backer.


Here is the first section dried, the clamps all removed and some of the excess glue removed.


I did not take photos of the other two sections being added, but the same procedure was used. Once they were glued up, I cut them to an oversized shape of the finished baffle and glued the two bottom pieces of the baffle on. You can see this in the final pic in the next post.

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Dan N.

dlneubec

Here is a more step by step for the MT baffle. In this case, there is not backer piece, so they are only edge glued. I added a stop block inside the side pieces to allow me to correctly space the varied sized pieces of the baffle correctly in relation to each other.


Next the baffle pieces are placed to allow me to determine the outline of the baffle and draw pencil lines around it.


The pencil lines were used as a guide to place double sided tape on the base so that the laminated pieces would not adhere to the mdf.


Here the laminated pieces have been edged glued.

Here the spacers were again added to allow the bar clamps to be clamped down on each end so the laminated pieces would glue up flat.


Here are the clamps all in place.


I decided to make it easy on myself and once everything was glued up and dried, I took them to a local hardwood mill and had them sand them down to smooth out any irregularities and remove any saw burn marks, etc. Here are the sanded results. The bass bin baffles were sanded on only one side, the MT baffles on both sides. I will mount the bass bin baffles to the box and probably trim them to size with a flush trim router bit.

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Dan N.

ThomasW

Nice!......

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ttan98

Dan,

I have been searching for a new high SPL mid-range drivers(use in an open baffle configuration), 4 potential brands are B&C(the one you are using now), the PHL 1120(J. Bagby was using),the Audax PR170M0(a new model, PR170N0 has been released) and the AE 6.5" Lambda. In terms of prices in ascending order are, Audax($89), B&C($92), PHL($120),AE($150). A real outsider is a hempcone 8" driver(about $85) from Tone Tubby, I heard good reports on this driver as well.

You have tested the B&C and so far have you tried and tested the AE 6.5" yet if so what are your impressions of both units. I have yet to read any feedback from anyone about their impressions on the AE 6.5" unit.

Comments from anyone in terms of their suitability are welcomed.

Cheers.

dlneubec

I also have tested and own the Audax PR170M0 as well. I have a used pair of them (if you want to get a pair to try yourself, let me know and I'll make you a great deal, say $70/pair +shipping).

After I had picked up my TD12H's and Peerless HDS's I had to wait a month or so for the B&C's to come in so I did a temporary crossover using the Audax. The Audax tested quite flat on my open baffle and sounded pretty good, as long as the volume was kept reasonable. I discussed it with Jeff and he indicatd he had considered the Audax as well, but determined that it just would not work for his open baffle crossed in the 450-500 hz range, due to limited Xmax. I figured this is what I was hearing that was bothering me about it when I crnked it up. The B&C and PHL have 2x the xmax and have no problem handling a 450hz crossover. Jeff has written some software to simulate a drivers performance in an open baffle in terms of xmax limitations, given the other TS parameters. He found the Audax too limited, but the B&C and PHL simulated fine.

I'm very happy with the B&C mid. Jeff has not heard it, but felt it would be a drop in replacement for the PHL he used in his original design for Salk, based on specs and measurments I sent him.

Salk is not going to be using the PHL. They have just had way too much trouble getting them, as I understand it. They are probably going to go with a version of the Lamba TD6.5, but that still seems to be up in the air a bit. I believe John is still working on a driver design for them. The Lambda TD6.5 version I tested for Jeff had a sizeable on axis dip at around 1500hz that the B&C does not have. I tested the Lambda and the B&C on my baffle and on a baffle that is shaped like Salks speaker and they were consistent. The Lambda had the on axis dip at about 1500 with both baffles. The B&C also has a dip, but it is up around 2500hz and not nearly as deep. I also tested off axis and it is important to note that the dip in the Lambda seems to flatten out off axis (as does the B&C). This may mean that it will be fine for dipole use since the extra energy off axis and to the rear on a dipole often fills in the midrange and can even make the midrange hot, if designed flat on axis. We have all exchanged a number of emails and the conclusion seems to be that the dip in the Lambda is open baffle/dipole related, perhaps the baffle shape and/or rear reflections off its larger motor. It apparently measures flat infinite baffle. One other point, the Lambda measured about 5 db or so less sensitive than the B&C, IIRC.

I have to stress that I only did measurements of the Lambda and it was the first prototype model. I did not listen to it or do any listening comparison between it and the B&C. I did try and model a crossover for it using the measurements I took. I had trouble getting something that looked as good as what I had with the B&C. Given that I was thrilled with the sound of my speaker with the B&C and it was considerably cheaper, I decided to just stick with it rather than explore the Lambda further.

My understanding is that John may be working on a higher sensitivity model and doing some testing of his own on a Salk-like baffle to try and discover what the issue that showed up in my my testing with that dip. I believe he also has a higher xmax version in the works that he hopes to compete with the Scan Revelator line. I suspect he will work these issues out and Salk will be using a lambda TD6.5 version in his design.

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Dan N.

ttan98

Dan,

Many thanks for a detailed response.

Have you considered using midrange as MTM configuration similar to Undefintion open baffle? I understand he used the mid in series, if I use them in parallel(4 ohms), then I can increase the the SPL by 6db, I plan to drive them separately so x-over to tweeter isn't a problem with 4 ohm.

dlneubec

I did not consider an MTM arrangement for this design, for lots of reasons, the first of which was that this design was inpsired by the Bagby Salk Sound design.

The MTM is certainly one valid solution to get higher sensitivity. However, any time you cover the same frequency with more than one driver, you potenially introduce other issues that could negatively effect imaging, time of flight, vertical polar response, etc. One of the benefits of using a high sensitivity pro mid is that you don't have to go MTM and deal with these potential drawbacks. I think most folks will agree that the MT arrangement offers improved imaging and polar response when compared to an MTM so the speaker sounds more the same whether seated or standing, etc. It certainly makes it much easier to attempt driver time alignment in a sloped baffle WMT than a WMTM or WMTMW.

I believe one uses two drivers in an MTM in an open baffle primarily because you has chosen to cross the mids lower, which requires either more excursion capability or more drivers to share the load. It also introduces the need for wings and/or a much wider baffle or active attenuation of the dipole rolloff to achieve the lower crossover point. This is not needed when crossing the B&C at 450hz like I am in this case. Excursion is not an issue at that crossover point and the baffle can be narrower, reducing the dipole peak and dip after the peak. Then there is the issue of effective piston area or Sd. The B&C has an Sd of about 133cm2, while the RS125, for example has an SD of around 50cm2, IIRC, so two of them in an MTM is still about 75% of the radiating area of one 6.5" mid. Same thing goes for two woofers. Two 8" RS225's for example, have a combined Sd of 412cm2, about 78% of a single TD12H, which has an SD of 530cm2. So, Sd is an important consideration in these decisions.

Also, in my case, the B&C is already a good 3-4db more sensitive than the TD12H and The Peerless HDS, so it is considerably attenuated in the crossover to match the mid and tweeter. That should give it even more headroom than it normally would have. If I had wanted an even higher sensitivity design, I might have had to consider multiple drivers. However I would probably have started with 2 woofers and a more sensitive tweeter as starting points, rather than more midrange drivers.

Finally, I wanted a narrower baffle for the tweeter to improve its imaging and a tapered side baffle allows for that, plus the tapered baffle offers the benefit of diffraction reduction. It's quite hard to narow the baffle in the tweeter area in an MTM configuration.

All that said, you can do a fine design with a WMTM or WMTMW or WMT arrangement, but each are done with a different set of constraints and assumptions from the start. In all cases, further design decisions are a reflection of that basic driver configuration decision. This one was destined to be a WMT from the start and all my design decision reflect that.

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Dan N.

Dougie085

Those baffles look freaking awesome

---k---

Dan,
those are really starting to take shape.
And, that was a lot of good insight. thanks.

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-Ryan
The Sietecerocero Project! ND140/BC25SC06 MTM & TM
My CJD Khanspires - A Dayton RS28/RS150/RS225 WMTMW
My CJD Khancenter - A Dayton RS28/RS150/RS180 WTMW Center
My CJD In-Khan-Neatos - A Dayton RS180/RS150/RS28 In/On Wall MTW

dlneubec

I completed one woofer baffle today (except final sanding and finishing) and got a start on the open baffle hardwood/lexan combo. I should have one of the open baffle sections complete tomorrow, hopefully. I'll take some photo's if I do.

I may finish one speaker completely, including veneer, hardwood slot port, etc. (but not finish) before I start work on the second one. So far I couldn't be more pleased with how they are looking and I'm very anxious to see one completed speaker. This also allows me to troubleshoot my process on the first speaker and avoid repeating any mistakes on the second, though overall, it will probably take longer that way.

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Dan N.

dian1511

Looking forward to the pics and continued process description.

You are truly amazing! You have an amazing amount of energy and determination. And you do marvelously detailed work, both in the design and implementation process.

Is there a special pill for productivity and energy? If so, please order me lots of it!

Darren

dlneubec

Here are some updates photos. It's starting to come together nicely.

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Dan N.

Jed

Words can not describe the beauty of that one Dan... keep the pics coming.

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dlneubec

Thanks, Jed.

One question I'm still considering is whether to leave the cut and/or routered edges and roundovers on the Lexan rough or try and smooth them out. Right now they are unsanded. I'm sure they could be smoothed out if sanded and perhaps there is a way to polish the edges.

I've experimented with heating some scrap edges with a propane torch and it essentially melts it slightly and makes it smooth and clear, but it is very easy to overheat and make it bubble.

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Dan N.

John_E_Janowitz

there are lots of compounds for buffing out acrylic or lexan. one of the keys is to use a large buffing wheel on fairly slow speed to prevent any burning.

John

matt12v

WOW, was staring at the pics for like 10 minutes.... Totally Unique and some serious speaker porn too! I bet it sounds just as good as it looks. Looking forward to seeing more pics. Keep it up Dan!

dian1511

Just Wow! Simply beautiful and elegant. Thanks for sharing the journey.

I checked out Lexan at the local hardware store and they only had thin stuff and it was expensive for the thin stuff. I'm curious how much the thick piece cost you? Supplier?

Also, is there an issue with wood movement regarding the hardwood laminated bass bin baffle onto hdf? I had laminated a circular piece of edge glued oak strips, the kind you find at the hardware store, onto mdf. I noticed the edge glued pieces started to come apart after about 6 months. Perhpas it was a poor edge glue job. I used it as the top for a sonotube sub.

Darren

dlneubec

Thanks Darren. When I do the other speaker I will documnet the process, since there are steps that have to be taken in a certain order or you can make it very hard on yourself. I found a few of those steps the hard way this weekend.

The Lexan I got was a 24"x24" piece, nominally 1/2" thick, though actually closer to 7/16" deep. I just checked and the price has dropped to $66 for a 24"x24"x1/2" sheet or for a 12"x48"x1/2" sheet. Here is where I got mine:
Polycarbonate sheet

I don't there there will be a wood movement problem. The Lexan and the wood are sandwiched together between the drivers, not glued. I made enlarged bolt holes in the hardwood and the driver openings are also slightly larger which allows for some movement. Of course, the hardwood will be sealed all around. The way I built it, it all comes apart, so if there is a problem, I can always take it apart and repair or rebuild with some other material.

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Dan N.

EdL

http://www.novuspolish.com/

I found the above in my search for a solution for my scratched turntable cover

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Ed

dlneubec

Hi Ed,

What are you creating these days (besides wood panels for Paul)?

I kind of like the baffle edges being defined by the rough edges, but it would be nice to be able to sand/buff the roundovers around the drivers smooth, so all the wood behind is visible.

BTW, did you try that polish out? I have a car-type buffer that I got from Sears that may work, if I can come up with the proper material to use for the buffing.

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Dan N.

cjd

Dan,

There are a whole pile of buff compounds and wheels available specifically for working with plastics that I had access to back when I was at school - all sourced from Rio Grande - that'd be a jewelry/metalworkin supply house. I don't recommend you even attempt any way other than the right tools.

Looking superb as they are, but I agree - it would be nice to polish up the roundover at the drivers.

dlneubec

I just read this online in some googling in regards to polishing polycarbonate:

"Polished edges may be achieved by solvent polishing. After sanding to remove all the tool marks, dip a cloth in a solvent such as methylene chloride and carefully wipe the sheet’s edges. Do not allow the solvent to drip on the sheet face as discoloration will occur."

I don't know under what name methylene chloride sells, but it might be worth testing on a sample piece to see what it does do, if ne can find it locally. I might even try a wipe down of acetone on a sample piece.

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Dan N.

Dennis H

Methylene chloride (aka dichloromethane) -- wear a respirator and keep it off your skin. POISON.

EdL

I had a second project this weekend along with Paul's. Scott Lindgren (aka Scottmoose) worked up a back-loaded horn enclosure using the Dayton DVC 8" sub. I got it assembled for some Sunday night listening and I'm very pleased. Thanks go to Scott for indulging me.
I'll gather up some supportive info for a thread.

Ditto on Dennis' caution, get the rubber gloves and all the personal protective gear out.

I haven't polished the dust cover as of yet.

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Ed

dlneubec

I tried some acetone and also some tripolene paint thinner and they didn't appear to do anything to the polycarbonate. I'm not sure where Methylene chloride can be purchased, even if I wanted to try it out.

I also tried a synthetic abrasive flap wheel in my drill and it actualy did a pretty nice job on smoothing out the roundover I made in a test piece. Before I'd use it on the finished baffle roundovers, I would want to mask the adjacent flat surface, just in case of a slip. It might work to smooth out the roundovers and make them more translucent. It has too much grit to actually get it to transparent, though I think it might be an acceptable solution.

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Dan N.

Paul Ebert

Dan, you might find that using heat to melt it to a polish works easier once it is at the translucent phase. I used heat polishing on my DIY turntable plinth and, with some practice, it worked out well. I found that the less the heat had to do, the easier it was to avoid overheating.

YMMV, of course.

dlneubec

Paul,

What kind of heat did you use?

I used a propane torch, but I wonder if a heat gun or maybe a pencil flame butane torch might be more appropriate. I don't believe the pencil flame butane gets as hot propane and you can really make a fine flame so as to be precise in what you heat. The heat gun would not be as precise in its delivery, but you could dial in the heat and use a consistent temperature, once you figured out what the heat setting was.

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Dan N.

Dennis H

I was wondering if you could use micro mesh and liquid polish on polycarbonate like you can on acrylic -- it's how they take scratches out of aircraft windows. This place sells the materials ($$) but they caution it doesn't work as well on polycarbonate because it's so soft. Clicking around the site is somewhat informative.

http://www.sisweb.com/micromesh/acr...lastic_kits.htm

dlneubec

I've got some synthetic abrasize flap wheels (180grit) as well as felt and cotton polishing wheels that all fit in a 1/4" drill coming from MSC to try out. We will see if they are of much help.

The one flap wheel I do have and mentioned above is quite worn out. It is from 3M, bu is around $35 for one, so I'm looking for a cheaper alternative. It could be that if I can get the roundovers to a more translucent stage with abrasives, a little applied heat will finish the job, as Paul suggests.

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Dan N.

cjd

Using the right buff compound is the key. That and keeping the heat away.

Paul Ebert

I used a propane torch. I was polishing 1 inch thick sides, so a wide flame was good, actually. I would try a heat gun on some scrap to see if it gets hot enough. I would think it can.

The nice things about using heat is that once you get the hang of it, it is very quick and the result is perfectly clear. But, before you get the hang of it, it is easy to overheat and get bubbles. Also, it is possible to set the acrylic on fire . That happened to me a few times. The flame is not very intense so it's easy to blow out, but where there's flame, there's bubbles.

Dennis H

Dan's using polycarbonate (I'm sure you knew that.)

dlneubec

I wanted to post a step by step process to show how I did the baffles for this project, both the bass bin and open baffle mid baffles. This post will cover the bass bin baffles. Sorry it is so long!

Bass Bin baffles:

After glue up of the baffles, I cut the baffles down so that they were within about ½” of the final width, making sure the center stripe stayed centered in the baffle. I used a portable circular saw with clamped guide piece. The bottom of the baffle was cut at an 8º angle on the table saw so that it would match the angle of the bottom of the box.

After clamping the baffle to the box, making sure the center stripe was vertical and centered; the edges of the box were marked from the back side of the baffle. I used these marks as guidelines for cutting the baffles, which was cut about 1/16” wider all around to make up for the veneer depth. I cut the baffle on the table saw, using an angle guide along the rip fence. This could also be done by hand with a circular saw and clamped guide piece. I might have used a flush trim bit in my router, but I had none that were deep enough to trim the 1-1/2” depth.




After the baffle had been cut to fit the box, I marked, counterbored and drilled the locations for the cap head screws that would go through the baffle to hold it to the box and also marked and drilled the location of the center of the woofer. I used a forstner bit for the counterbores and a drill bit larger than the cap head screw shaft so there is room for wood movement and a less than perfect match with the threaded inserts.

The location for the center bottom protrusion on the baffle was marked and using a 45º chamfer bit, I routered a ¾” chamfer up to those points. This was done using a router table, but could be done by hand. I recommend doing it in stages to build up to the ¾” depth, rather than ¾” all at once. I then routered sides in the same manner. I also cut (on the table saw) a small chamfer on the bottom of the protruding section so it was not a sharp corner. I also cut the chamfer on the top of the baffle (shown below). This cut was at 30º and was done in on the table saw, against the rip fence. A vertical support piece was placed along the rip fence to provide a larger vertical surface for the baffle to run along. The support piece was temporarily held to the rip fence using double sided tape and removed after the cut as made. This cut need to also be ¾” deep to match the chamfer on the sides and is used to locate the front of the OB section when positioning it. This was very difficult to hold steady with such a large piece and perhaps a little dangerous. It did not turn out as well as I would have liked. If I had to do it over, I would make a sled jig of sorts that I could clamp the baffle to and slide the whole thing along the rip fence in one piece. This is what I would recommend for anyone trying to make a cut steeper than 45º. It would be much more effective and safer. You could also just do a 45º cut here also with the table saw or chamfer bit.

Next I clamped the baffle to the box and using the holes I had already drilled as a guide, drilled pilot holes for the threaded insets into the box braces. Removing the baffle, I now was able to drill the appropriate sized holes for the threaded inserts and install them.


The next step was to create the driver rebate and rear mount opening. The driver rebate was routered from the rear of the baffle. From the rear of the baffle, I routered just a one bit width slot, at the appropriate depth (leaving ½” between the rebate and the front of the baffle) that defined the outside of the rebate. Then I routered out the through hole. Using a ¾” roundover bit in a router table, the roundover for the front of the woofer hole was completed next. I recommend doing it in several passes of increasing depth. The round over had to be done before the rebate was completed so there was material left for the bearing to ride on. Once the roundover is complete, I went back and set the router depth to a depth of about 3/16” less than the depth of the ring I cut from the rear and routered out the excess of the baffle to make the rear driver rebate. The 3/16” difference provides a lip for the driver frame to set into the rebate and the shoulder provides a place for gasket to seal the driver. BTW, I removed the outer rubber mounting ring that comes with the TD12H for my application, hence the protruding lip and need for gasket.




I also had to drill the holes for the threaded bolts that hold the driver in place. To do this, I positioned driver in the rebate, making sure the hole positions lined up vertically and horizontally and the driver was centered. I used the driver frame holes themselves to start a shallow pilot hole with a hand drill, but finished them in the drill press to be sure they were 90º. I used a 1/8” bit for the pilot holes through to the front of the baffle. Shallow counterbores were drilled for the cap head screws so they were close to flush when installed, using the 1/8” pilot holes to center the forstner bit. This left about 3/8” material between the bottom of the counterbores and the driver. Larger through holes were drilled, again a little larger than the diameter of the cap head screw shaft, to allow for a little wood movement, etc.


The final step was to add the contrasting ¼” hickory strip along the back edge of the baffle. I used a dado blade in my table saw to cut ¾” wide, ¼” deep rabbet out of the hdf to act as a shelf for a shelf for the hickory strips. I stopped short of hickory base pieces along the bottom of the baffle. That leaves about 1” of HDF that has to be chiseled out so the ¼” deep hickory trim pieces intersect the full depth base hickory pieces. Then I cut the trim pieces (I had previously ripped) to fit, with mitered corners. The strips are then glued and clamped in place and were later sanded to ensure a flush match with the surrounding wood.




Some sanding of the baffle sides, bottom and top edges may be necessary for a more perfect flush fit with the box once the veneer has been added to the box. Other than final sanding and finishing, the bass bin baffles are basically complete at this point.

I'll add a step by step on the open baffle later.

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Dan N.