Curved Econo-wave Build Thread

Well, I decided to build a pair of Econo-wave speakers using JBL 2226 15" woofers for the low end and the Ewave top end from this thread. I also am using the high sensitivity crossover design. This should give 97db/watt sensitivity when finished.

http://audiokarma.org/forums/showthread.php?t=150939

The enclosures for these will be a curved enclosure made entirely from Baltic Birch. They will be about 4.5 cubic foot each tuned to 38 Hz. These will be 40" high overall and 18" wide in front and curved to 12" in the back. I plan to curve 1/4" Birch for the sides in 3 layers. I would post pics of the drawings for these but they were drawn up in AutoCAD. This will be similar to my Recession Buster speakers.



First I needed a form in order to make the tops, bottoms, and braces. This was made from MDF for smoother machining. The sides were all coated with a 50/50 mix of Titebond and water to strengthen the sides to reduce wear.




From this form I traced out all of the braces and tops/bottoms from Baltic Birch 3/4" ply. Initially I cut them out with a jigsaw to get the cuts close and then used a flush trim router bit to ensure that all the pieces were cut the same.



4 of these pieces will be used for braces so it was necessary to cut windows out of the braces. Again for these I cut 1 piece up as a template and flush router trimmed the rest of the pieces to match it.





All of the braces were then given a 1/4" roundover in the windows to clean them up.



Using a biscuit joiner the end pieces of the first enclosure were then assembled with only Titebond 2. I recently purchased a biscuit joiner and now use it for everything. It makes for a very strong joint and is very simple to use.





That is all for tonight. Please feel free to add any suggestions or recommendations. More pics will come tomorrow.

These pieces are actually for the entire enclosure. I plan on flush mounting the horn and woofer into the front of the enclosure. The woofer will have another layer of 3/4" Birch added behind it for strength.

Do you have access to any crossover design software? I do not have any software but I would absolutely be willing to take measurements using REW.

Great, thanks NoBS!! I will give a shot once these speakers are assembled. I currently have all of the components for the E-wave high sensitivity crossover. Perhaps I will use that as a "reference" of sorts and then do some measurements after that.

More progress was made today. The enclosures are assembled with the exception of the sides which I purchased today.

Here are the drivers and horn that will be used in these enclosures.


I cut pieces to use to double the baffle thickness behind the woofer. These I used biscuits to attach the baffle to both of the internal braces. Then these assemblies were glued and temporarily screwed to the enclosures.


Here you can see where the baffles are screwed to the front baffle. Keep in mind that the screw locations will be cut out when the woofer cutout is made.


I then used biscuits again to join each of the braces and the tops and bottoms of the enclosures to the back. I ended up using nearly all of my clamps in order to hold all of these pieces securely together. You can never have too many clamps!!


Here is the end result for the day. Both enclosures are ready for the sides to be attached. With any luck I should be able to get all of the sides on.



I began as well to prebend the 1/4" Birch plywood. Hopefully this will relieve some of the stress in the wood for tomorrow. I wish I had access to a steamer to add moisture to the backside to allow the wood to bend easier.



What do you guys recommend to line the internal walls with? Previously I have used egg crate foam for ported enclosures and polyfill for sealed ones. Is there something better to use at a reasonable cost?

I will probably be putting a slot port into the lower part of the back of the enclosure. This should make sure that the front of the enclosure stays clean looking.

Today I concentrated on cleaning up the enclosures somewhat and flush mounting the drivers. I kinda figured that the horn would be a PITA to flush mount.

The first task of the day was to clean up the edges of the enclosures. Using a flush trim router bit I cleaned up the ends of the cabinets and sanded the sides of the braces to prepare for attaching the sides. Looking much better.



Next I worked on flush mounting both the driver and the horn.
First the easy one, the woofer. I attached a board underneath the woofer cutout to hold the cutout in place once it is fully cut out.


Here is the woofer flush mounted. Note that it will sit ever so slightly higher once the gasket material is placed behind it.



The horn was much, much more indepth. I thought about how to make a template to cut out the horn pattern consistently and accurately.

This is what I came up with.


This template is used with a Jasper 100 circle jig to cut the outside of the horn recess for the JBL 338800. This Jasper jig was used as a "standard" just in case I want to use these horns in the future I will be able to flush mount them with any router just by using the Jasper jig.

It took several hours of sanding and "fine tuning" to get it to fit the horn just right.


Here is the final result.




What I wouldn't give for a CNC router table. That would have made life so much easier. Making up and cutting the horn recess ended up taking about 6-7 hours to get them just right by hand. But......the beauty is in the details. I will be better off taking my time and doing it right instead of rushing it and messing something up.

Maybe this weekend I will be able to get some sides on the cabinets. I think that I will use the fiberglass to line the walls since I already have plenty stored away in my garage and I will try to find some plastic washers or perhaps use staples to secure it to the walls.

Before the sides go on I would like to finalize the port design. Using WinISD to model the response at 400 watts input power in this 4.6 cubic foot enclosure the air velocity stays under 50 ft/sec with either a 5"X8" slot port 10.93" in length or 3 4" ID round ports 12.31" long for a 38Hz tune. I don't plan on using this much power with these speakers but I would like to be prepared just in case I do from time to time. Either way I would like to put the port(s) in the back to keep the front clean. What would you guys recommend to port them with?

Progress has been a bit slow going as I have gotten a bit busier at home. Anyways we have pushed ahead anyways.
I decided on a 4.5" tall by 9.5" port. This has been constructed again out of Birch ply. All of the edges have been rounded to smooth airflow and improve the aesthetics.


The rear of the enclosures have been rough cut open to get close to the size of the port.


The ports were then glued into the enclosures using Titebond 2.




The rear ports were then flush trimmed to the size of the ports.


The edges of the port were then rounded over and sanded smooth.



I then began to attach the 1/4" Birch ply to the sides of the enclosures.
This was accomplished by constructing jigs to spread out the clamping load. The jig was also made with curved cross braces to match the internal braces. These were built as a mirrored pair. This ensures that when the sides are attached the jig will apply adequate pressure where required.



This was after the first of 3 layers of 1/4" ply was glued on.



In order to attach the 2nd layer of ply I used Titebond 3 in order to ensure plenty of strength and a bit longer assembly time.
Here I am applying the first of 2 layers of Titebond to the ply.


This glue was evenly spread with a roller.




Here you can see how tight the ply is held together.


This is after 2 layers of ply. Next up is the 3rd layer and then finishing work on the cabs.



I am currently out of town for work. Hopefully I will be getting back this Sunday and will be able to finish up the speakers by the end of this week or maybe next weekend.

I was trying to follow the design layed out over at AK. I didn't want to have to redesign a new crossover and I was trying to build these somewhat on the cheap. So far I only have $500 into these speakers. Also I have never designed a crossover from scratch before, only modified existing ones slightly. That is also why I did not use an AE woofer. I found these woofers on Fleabay for less than $300 used. I would have liked to have used a woofer such as the TD15M for high sensitivity but that would have added significantly to the cost of the speakers. I may also in the future modify these to the 4Pi design from Pi speakers and use a DE250 CD and the TD15M. First I will need to hear these though. This way I always have an upgrade path in the future.

Hey Tack, thanks for the compliments. I explored that link you provided and ended up dropping $100. I started looking at the rabbet bits and then thought about what else I could use. You know how it goes.

With any luck I should have these speakers finished up by next weekend. I still need to decide on a stain color. I was thinking of staining them a cherry-ish hue. After a bit more experimenting with colors I should have it nailed down.

I would like to keep this speaker au natural of sorts. I want to leave all of the Birch exposed and just stain or possibly shellac it. Do you have any experience with this shellac on Birch itself?


Thanks Kanaris. I checked at all of my local Menards, Home Depot's, and Lowes and could not find any bendable ply. I did not check with any local lumber yards however. I decided at that point that I would use the 1/4" Birch and simply stain it when finished.