Another ER18 Build, #2, #3, #4 ??

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David LR

Junior Audioholic
Hello-

I'm posting my build thread of the Murphy/Kittinger ER18MTM speaker. This is my first build thread so be kind guys. As far as I can tell there's at least 3 ER18 builds & one other potential one on this forum, interesting they're all happening at roughly the same time.

I purchased my materials from Meniscus a couple of months ago, I'm building the RS28F dome version, thought I was all set on the ribbon tweeter but my contact at Meniscus seemed to favor the RS28F so that's what I got. Either way it'll be OK, in the original ER18 thread, Richard Swerdlow said there wasn't a significant difference between the two tweeters. By the way, this will be the 5th or 6th speaker I've built, so, not a rank beginner, but not a pro either. This is most certainly the largest speaker I've built, all the others have been bookshelf size.

My son's roommate is a woodworker, rents space in a shop in town, he did the cutting for a small fee, also did initial glue up of the top, side, and shelf braces. That part wasn't my original plan, I just wanted the cutting done, but he seemed to want to do it, so fine. It may have worked better if I had done the gluing, I don't know. He assembled everything all at once, multiple pieces, multiple clamps, many things to get aligned, and in the end, somethings were a little out of alignment. I would have glued one shelf brace at a time, I have neither enough clamps, skill or experience to attempt what he did.

erclamps.jpg,

Here's a picture of the clamping setup at the shop, I think I count fourteen or fifteen clamps :eek:

Image00005.jpg

Some of the shelf braces were not lined up flush with the edges of the side pieces, hard to explain, but here's a pic: I could have left it alone I suppose, but then the back piece/front baffle would not have had full contact with the bracing piece. As you can see, I just cut a 3/4" piece of leftover veneer to fill the gap, not perfect, but it allowed solid contact all the way across the brace. Think I had four of the braces I had fix this way. The braces actually sloped from one side to the other so I had to use a block plane the slope the fill pieces.


ER00004.jpg

So, I've got the backs glued on both speakers, here's my clamping assembly. Quite the odd collection of clamps, I know, I was surprised I had that many, only had to borrow two (not including the sand bag :)) I over-sized the back by 1/8 of an inch all the way around, then flush trimmed with a router

ER00007.jpg

And, here's the assembled speakers to date--, next step is to rout the holes for the vents , layout & rout holes for speakers on the front piece. If I get that much done this weekend, I'll be doing great ! Fun project, it's fun just to build something, even if it isn't perfect every step of the way. Thanks for looking. I will be asking for advice in the future posts

Dave
 

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mattsk8

mattsk8

Full Audioholic
Nice shop!! I have that same rigid belt/spindle sander. Actually a pretty nice machine for the money!!

(edit) Just saw it was your son's friends shop. Good connection!

As far as the braces not lining up, I have that to a degree as well. When they're all assembled w/out the front baffle the braces are a light 1/32" shy of coming to the top of the side panels. Not a big deal mainly because it'll clamp and the woodglue will generally fill that void. It's tough to do because (I'm sure yours is the same) my MDF isn't a true 3/4", it's a heavy 3/4". That messes things up a bit. Plus, it's better to make the brace dados a teeny, tiny bit deeper than the rabbets around the sides. That way, you don't run the risk of your braces holding any of the sides or baffles out.

I think your speakers are looking great!! Glad you posted. I only said this ^ so you wouldn't be worried is all.

BTW, how wide did you make your braces? What I mean is, when you cut the centers of the bracing out, what was left? I was going to leave 1"; which, because I dado'd everything will translate to 3/4"- know what I mean??
 
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David LR

Junior Audioholic
Matt-

Thanks for the reply. Yeah, I don't think I mentioned earlier but we went the dado route also. We made the braces 1" wide where they go into the dado, the cross piece was also 1" wide, only the rear that rests on the back was 3/4" wide. We were worried about strength because the dados were a really right fit. I do have measurements somewhere on the actual blank areas, have to find them. I don't think the shelf brace drawings were to scale, didn't work that way for me anyway, so I came up with something the looked fairly proportional to the drawings.

It is a nice shop. The outfeed table on for the saw is just about as big as my whole working space in my "shop", ie, one car garage.
 
mattsk8

mattsk8

Full Audioholic
Matt-

Thanks for the reply. Yeah, I don't think I mentioned earlier but we went the dado route also. We made the braces 1" wide where they go into the dado, the cross piece was also 1" wide, only the rear that rests on the back was 3/4" wide. We were worried about strength because the dados were a really right fit. I do have measurements somewhere on the actual blank areas, have to find them. I don't think the shelf brace drawings were to scale, didn't work that way for me anyway, so I came up with something the looked fairly proportional to the drawings.

It is a nice shop. The outfeed table on for the saw is just about as big as my whole working space in my "shop", ie, one car garage.
The brace drawings weren't to scale. The woofer brace shows it being 2 13/16" long in the drawing (supposed to be 12"). That breaks down to 45/16" so it should be 3.75/16"= 1". But, if that were the case the 2" deep cutout for the woofer should be 7.5/16"; but it isn't, it's 9/16" deep in the drawing. That was my confusion as well so I just winged it and made them 1".
 
Swerd

Swerd

Audioholic Warlord
The brace drawings weren't to scale. The woofer brace shows it being 2 13/16" long in the drawing (supposed to be 12"). That breaks down to 45/16" so it should be 3.75/16"= 1". But, if that were the case the 2" deep cutout for the woofer should be 7.5/16"; but it isn't, it's 9/16" deep in the drawing. That was my confusion as well so I just winged it and made them 1".
Thanks for being so gentle :eek:.

No the brace drawings were not drawn to scale. All of my drawings for the ER18 MTM design were done free hand in MS Word. I always tried to include dimensions that were critical. I was also doing the writeup and drawings by imagining the build without the benefit of having built a set. So I could be only so precise. All of your experiences with building this speaker are therefore valuable, because you have been able to identify the weak spots in the write up.

David - very nice job so far. Thanks for the photos. I've seen enough small differences the various builds of the ER18 MTM so far to realize most don't matter. Don't sweat the small stuff. As long as your cabinet is the right dimensions, ±10%, and the box is rigid and well braced, you'll be fine.

I really think if you take the same design plans and have 5 different people build it, you come up with 5 different sets of small variations in the build. Most of them will work fine. They only way we could find out which differences don't work so well would be to get together and directly compare the speakers – a national ER18 MTM get-together. Yeah, that's the ticket. Let's ask AH and Meniscus audio to pay for the hotel :rolleyes: ;).
 
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David LR

Junior Audioholic
Thanks Swerd, appreciate the input.

I've got a forum usage question for you or anyone who knows. Am I really limited to only 5 photos per thread ?? I see I can reference outside sources via html, so I maybe I've answered my own question, don't know. What do people use as outside sources, Photobucket or something like that ?? Just need to some photo education !!

Thanks-

Dave
 
Swerd

Swerd

Audioholic Warlord
Am I really limited to only 5 photos per thread ?? I see I can reference outside sources via html, so I maybe I've answered my own question, don't know. What do people use as outside sources, Photobucket or something like that ??
Dave

That's just what people do. They post their photos to Photobucket or any similar photo storage site, and they create a link here using the Insert Image button. Click on the yellow icon that looks like a postcard, and insert the URL address of the photo image in the resulting dialog box.
 
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David LR

Junior Audioholic
OK, got it, thank you. I'll have to get set up somewhere.
 
mattsk8

mattsk8

Full Audioholic
Swerd, hope that didn't sound harsh at all!! I can't tell you how much I appreciate you taking the time to do the write up!! Also how excited I am and it's all because you took the time to do it all in the first place :cool:! Because of you guys here at AH I feel like a kid that just got a bunch of new toys!! I'm having soooooo much fun w/ the speaker building and I owe most of it to you guys; started w/ that fateful Yamaha receiver question and led me down here! Thanks again!!

David, as far as the photos go, if you look at my first couple threads you'll see that anywhere there should be a photo it says "edited". I deleted all my old images because I reached my limit through the "manage attachments" area as well. Then I learned about the little "insert image" box at the top of the screen that's up while typing a new post (little box w/ a mountain on it).

It was a little tricky for me to figure out at first, I'm definitely no computer guru :confused:! I had to open a Picasa account and put all my photos there. Here's a link http://picasaweb.com/ You can do a LOT more w/ Picasa than just post images here though. It's really a nice tool.

It was pretty easy once I got there because Picasa is part of Gmail and I already had gmail for my email; so if you have gmail just go to that picasa link and put in you email address and password and you'll be at Picasa's homepage. The other thing I like about Picasa is that I have an app on my Android phone that I can automatically upload my photos to Picasa that I take w/ my phone. It makes posting new pics of a speaker build pretty simple because I take pics throughout the day w/ my phone, select the ones I want to upload to Picasa then upload them. Then when I'm on this site I just open a new tab w/ Picasa and I can copy and paste away to my heart's content!

I know that's a lot of info but if you have any questions I'll be glad to answer. Just a matter of when, I check in here periodically throughout the day at work.
 
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David LR

Junior Audioholic
OK, well, that's cool. I'm an G-mail also, so I'll take that approach. I'm not a real fan of Picasa as an image organizer, not terribly intuitive to me, but perhaps I've just not taken the time. I like using Fast Stone Image Viewer, it seems to think like I do. (Don't know what that says about Fast Stone !:eek: )

I will check out PicasaWeb then, thanks for the info. Good tip on the Android, my phone is Android based as well.

David
 
mattsk8

mattsk8

Full Audioholic
OK, well, that's cool. I'm an G-mail also, so I'll take that approach. I'm not a real fan of Picasa as an image organizer, not terribly intuitive to me, but perhaps I've just not taken the time. I like using Fast Stone Image Viewer, it seems to think like I do. (Don't know what that says about Fast Stone !:eek: )

I will check out PicasaWeb then, thanks for the info. Good tip on the Android, my phone is Android based as well.

David
Whatever works for you. I only picked Picasa cuz it was one that was recommended to me, I found out later it was part of Gmail. Originally I liked it because you could edit your photos w/ arrows and text and what not, but I think they got rid of that for whatever reason. As far as the other photo places, I have no idea what's better because Picasa's the only one I've ever used.
 
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capricious

Junior Audioholic
I use photobucket for this purpose. Its reasonably user friendly and free.
 
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David LR

Junior Audioholic
Well, I'ts been a month since I've posted. Just wanted to update & say I'm still moving forward on the project although not nearly as fast as I wanted. Got some good things, got some bad things, first the good things--

I decided I was not going to do any more routing until I figured out a dust collection system, way, way to much foggy dust floating around the garage, in my lungs, on the floor, hugh mess.
So, read the manual, deciphered how to hook up the hose connection piece that came with my router, realized the missing link was a hose & adapter piece to link up with the shop vac. After searching at Home Depot, ect for a while, not finding any suitable hose, I got the bright idea to check a vacuum cleaner supply place & found the perfect hose - just the right size, strong, flexible, found the adapter piece at Home Depot, used duct tape to make secure connections- works quite well-not 100% but probably 95% of the MDF dust goes to the vac & not on the floor. Here's a pic:
 
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David LR

Junior Audioholic
More good stuff, got all the inside joints caulked, probably not absolutely necessary but cheap insurance none the less, also got the woofer/tweeter holes routed on the front piece without too much problem-

 
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David LR

Junior Audioholic
Now the bad stuff - I'm having a heckuva time getting the baffles cut properly. I've tried three times, screwed up every time, one way or another. Mainly, it's related to the depth of the cut. I'm following good procedures I think, I measure the cutting depth very carefully, make test cuts in scrap MDF, but for some reason, the depth of cut increases over the test cut.

In the pic below, you can see attempts 1-3, pictured left to right Attempt 1 - depth of cut was way, way too deep, almost twice what I was aiming for. All I can think of is I had the router upside down when setting the depth, something must have shifted when put in cutting position.

Attempt #2 - First circle, OK, second circle- slightly deeper, between 1/16 & 1/8 deeper than first cut. Did not verify depth between circles.

Attempt #3 - First circle, OK- verified depth of cut before proceeding, second circle OK also. Success ??? No, of course not ! Take a close look at baffle #3 ! What's that you say ? There's no room for the tweeter between the two woofer holes ??
Durn right there ain't !!! That's because the router operator put the guide pin of his Router Buddy jig into the pilot intended for the baffle arc and NOT into the carefully measured pilot hole for the lower woofer !!! I tell you what, careful layout, accurate measuring & testing are no match for basic stupidity !



But, never mind, will cut out two more baffle blanks & press on.
I'm learning from my mistakes, I think.

Two questions- 1) How are you guys cutting the notches for the tweeter hookup terminals ?
2) Anybody have any idea why my router depth
cut keeps changing ??

This is my router depth setting mechanism if that helps






Thanks for your answers.

Dave
 
mattsk8

mattsk8

Full Audioholic
First off, the depth issue would have to be related to the router. I've never used that Milwaukee, but on my Dewalt (DW-621), I set the depth for the speaker indentations at 3/16" for both woofers and tweeter. To do that on my Dewalt plunge router, I use a brass 3/16" depth gauge w/ the router upside down, set my depth using a dial on the side of the router and once I'm happy w/ my depth I turn this thumb screw that basically locks my depth adjuster. Doing this makes it so I can't plunge deeper than 3/16". Once this is done, I'm ready to start routing. I put the router on the workpiece, start the router and plunge down to my maximum 3/16" depth. Once I'm there, I can turn one of the handles on the side of the router to lock it at that 3/16" depth so I'm not constantly forcing it down, it stays at that depth. Then I route out my circles. Just FYI, I also use the Jasper circle jig.

Maybe that was way too much info, but if your depth is changing mid route then something's definitely wrong. Either you're missing a screw to tighten somewhere to lock the depth in or there's something wrong w/ the router. Hope that helps.

To answer the tweeter question, I used a 1/4" router bit and just routed out the area for the heat sinks on the ribbons when I did it on the Statements. Prob w/ these baffles is they're 1 1/2" thick, Statement baffles were 1 1/4" and 1 1/4" is as deep as my 1/4" router bit will cut. I haven't done that yet, but I'm either going to route as deep as I can in mine (1 1/4") and finish it out w/ either my jigsaw or use a 1/4" laminate cutting router bit in my router to finish out the rest of it.
 
Swerd

Swerd

Audioholic Warlord
With the RS28F dome tweeter, the terminals require cutouts that go beyond the diameter of a cutout for the rear chamber.



PE says the rear chamber diameter is 3¼" and the front mounting plate or flange is 4⅛". I can't find on the web page what the distance between the terminals is, but it will be between 3¼" and 4⅛". Measure the distance on your tweeter between the terminals and add another ¼" just to be sure.

When I cut a recessed hole for a tweeter, I first cut the recess for the tweeter flange. I use a 1¼" mortise bit (it has cutting edges on the sides and the bottom of the bit) to make a cut 4⅛" in outer diameter, and as deep as needed to flush mount the tweeter. Remember to include the depth for the compressible foam that makes a seal behind the tweeter flange.

After that, I use a ¼" bit to start cutting the rear chamber cutout with an outer diameter of 3¼". My router can cut about ¼" depth of MDF on a pass, so ¾" will require at least three passes.

After the first or second pass, but before you cut all the way through the board, stop and use a larger diameter pivot point on the circle jig to make 2 cuts for the terminals. Put them on opposite sides of the circle for the rear chamber. These cuts don't have to be in a full circle. Make each cut about ½" to ¾" along the circle, enough to allow the terminals to pass through and allow access for the wires that will attach. Cut them all the way through the baffle

Then finish cutting the hole through the baffle for the rear chamber of the tweeter.

I hope that is clear.
 
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David LR

Junior Audioholic
Swerd;889544 When I cut a recessed hole for a tweeter said:
First, thanks for your reply. Sorry I didn't respond sooner. Regarding the 1 1/4" mortise bit, that sounds interesting. So, you're making a cut 1 1/4" wide in one pass ? Sure beats my bit, I'm using a 3/8" wide straight cut, which will require at least 3 passes, maybe 4, to get the proper width for the woofer flange.

Your tip on cutting notches helps, a little hard for me to follow, I'll look at it more closely when I'm at that point. Part of my problem is I"m using the Router Buddy jig & not the Jasper jig. I've never used the Jasper jig, but it looks like all the holes are fixed in 1/16" increments (?) , whereas with the
Router Buddy you can measure as small a radius as needed, however, it's sort of tricky to use, making repeated cuts of the same radius is difficult after you've changed the original setting.
 
Swerd

Swerd

Audioholic Warlord
First, thanks for your reply. Sorry I didn't respond sooner. Regarding the 1 1/4" mortise bit, that sounds interesting. So, you're making a cut 1 1/4" wide in one pass ? Sure beats my bit, I'm using a 3/8" wide straight cut, which will require at least 3 passes, maybe 4, to get the proper width for the woofer flange.
Yes, you do understand what I tried to say. Each pivot hole in the Jasper Jig is already measured to give you a circular hole of the indicated diameter. They are in increments of 1/16".

For example, if you use the 3" pivot point, and a ¼" diameter bit, you will get hole 3" in diameter. The circular piece of wood that comes out will be 2¾" in diameter. You can use other size router bits, but you will have to do a little arithmetic to predict the diameter of the hole.

I chose a mortise bit because it has sharp cutting edges on the side and on the bottom so I can start by plunging in. I chose the 1¼" size because its 1" more than ¼", making the mental arithmetic easy - just subtract by 1. If I want a flange recess 3" in diameter, I use the 2" pivot point on the jig.



I find its easier if I cut the recess for the flange first and then cut out the hole for the tweeter body. The other way is to cut the tweeter body hole first and then use a bearing mounted rabbit bit to cut the recess for the flange. The rabbit bits I have cut a rabbit no larger than about ½". I can get a much wider recess with the mortise bit.

Your tip on cutting notches helps, a little hard for me to follow, I'll look at it more closely when I'm at that point. Part of my problem is I"m using the Router Buddy jig & not the Jasper jig. I've never used the Jasper jig, but it looks like all the holes are fixed in 1/16" increments (?) , whereas with the Router Buddy you can measure as small a radius as needed, however, it's sort of tricky to use, making repeated cuts of the same radius is difficult after you've changed the original setting.
Yes, it can be hard to put this in words.

I described what I do with a Jasper Jig, where it's easy to change diameters, and then return to an earlier setting. If you use a different jig, like the Router Buddy, the details may differ, but the general approach will be the same. What is necessary is to know what diameter circle will make a cut out big enough for the tweeter terminals. It just may be that a full circle cut out of that diameter will leave you with enough flange mounting surface. That would be simpler to do.
 
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