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-   -   Small Thor -Reloaded -First build (http://www.diyaudio.com/forums/multi-way/223549-small-thor-reloaded-first-build.html)

8ntractor 14th November 2012 05:15 AM

Small Thor -Reloaded -First build
 
Hello
I am a very recent member, after reading about the Ariel on Lynn Olsens site and gaining an appreciation of the work and deep level of thought involved in speaker building in the "Beyond the Ariel" and "Clarity on the Seas Thor kit" threads. Then getting a xmas present of preowned Thor drivers and crossovers. I would like to build the small Thors. This will be my first speaker build. To start with I would like to Thank Scottmoose, and planet10 for the design work, jimangie and the community for the cross over work and speaker testing, Renron, KarlXII and all the others for the inspiration. I know and appreciate the work the whole community did to improve this speaker.

It was recommended that I start a new thread for this build.

Starter Questions, to get cabinet material. while the drivers and crossovers are camped out in customs. I have had trouble finding the answer to these questions on the site. I know the answers are here but I cannot figure out the search terms.

I have read that it is important to maintain the baffle width. when the baffle width is used to calculate the baffle step compensation does it include the chamfer or radius. If I have a 9" baffle with a 1" chamfer on all sides is it a 9" baffle or a 7" baffle?

Because the largest birch ply I can get is 5/8" can I add 3/4 mdf to the inside at of the baffle to reduce resonances? (can I glue mdf to plywood?)

If I add material to the sides the speaker will no longer be 9" wide does that mean the crossover will need to be changed.

or

Because we are at a stage in our lives where downsizing is becoming important the smaller I can keep the speakers the better. Can I get most of the benefit of added thickness through using additional braces?

As a first build I do not want to change much from the good work that has already been done. I know I have to maintain inside dimensions of the cabinet. I know the baffle width is important, I know the edge should be chamfered or have a large radius. I know that the thicker the walls the better. I am not sure how important the outside dimensions are.
I do know that I cannot have the same inside and outside dimension as the drawing and have thicker panels:D

The holy braces - Did'nt get it till I did it. - Started the holy brace with Mdf and a hole saw. Smoked the saw and the drill!!! only have a small portion done so can the holes be rectangles? Is plywood a better brace? the mdf seems weak. I dont mind remaking in ply.

thanks
Ben

planet10 14th November 2012 05:29 AM

Quote:

Originally Posted by 8ntractor (Post 3240852)
If I have a 9" baffle with a 1" chamfer on all sides is it a 9" baffle or a 7" baffle?

9"

Quote:

Because the largest birch ply I can get is 5/8" can I add 3/4 mdf to the inside at of the baffle to reduce resonances? (can I glue mdf to plywood?)
It is probably 15mm called 5/8", but a piece of ply is rarely the advertised thickness, work from an actual measurement (and don't trust that the wholw aheer is the same. 15mm is usually the hard thickness to come by, 18mm then 12mm being more easily available.

Quote:

If I add material to the sides the speaker will no longer be 9" wide does that mean the crossover will need to be changed.
If you laminate 2 x 15mm it won't make all that much difference.

Quote:

Can I get most of the benefit of added thickness through using additional braces?
Yes, but if you use lots of braces you need to compensate some to keep the cross-sections the same.

Quote:

The holy braces... Is plywood a better brace? the mdf seems weak.
The holey braces (braces with holes, not something from the bible), can be more work than the box itself. Holes can be any shape, you just want to hit 30-40% holes without creating any weak spots (round holes usually make that last easier) and keep a direct path from the back of the driver to the next panel.

dave

8ntractor 14th November 2012 07:20 AM

Thank you Dave

Renron 14th November 2012 03:09 PM

Ben,
A few more answers to your questions and a few tips.
No way could I ever know as much about speakers as Dave does. He is the MAN.
I do know wood working though. :) Some tips for drilling those pesky "Holly Braces".
Use a slow speed drill, a Milwaukee right angle drill has the perfect speed. Borrow one from a carpenter/plumber friend. 1/2" chuck and a heavy drill.
Don't try to plunge cut the holes all at once, cut a few mm deep and then clean the teeth of the hole saw, MDF is such a fine powder and the glue clogs the teeth. This will also prevent the Bit from burning/over heating and dulling.

Rectangles are fine, use a file or rough sandpaper to round over the interior corners of the "holes". MDF or ply for braces, either is fine. If the MDF splits just reglue the parts back together.

Buy a gallon of Titebond II glue, as long as it doesn't freeze it will last a very long time. Mine is >4 years old and still good. Get a small bottle of glue and refill it from the gallon jug. It will be cheaper in the long run than buying small bottles.

This won't be your last speaker build project, it may be one of the best, and you may keep it for a long time.............so, do it correctly the first time and don't be in a rush to finish them. Your going to look at them in your home for a long time. Plan ahead on how you want to finish them, a glossy black sounds nice but it is a lot of work. (understatement)
Paint or Veneer? Don't use the stick on vinyl crap.

Xovers, which version are they? If you do not know, then take a look at the component values to check against the old/new versions.
Consider building the Xovers outside the speakers. My first build I built them inside, the new ones live outside. Lesson learned. :)

You should calculate the volume of internal bracing, additional plywood on sides and baffle interior and then adjust the depth of the cabinets accordingly. Make them deeper. The speakers sound better with more volume inside the cabinet.
Speaker wire/ hook up wire wise. Good quality but not crazy $$$ multistrand wire is fine. I like a grade or two better than lamp cord, but others find lamp cord just fine.

Do you own or have access to:
Clamps (lots of big ones)
Router and bits
Sander
Paint equipment
Non smoked drill :eek:

Keep us informed of your progress.
We like pictures, and you'll get a better response if we are entertained.

Ron

8ntractor 15th November 2012 06:41 AM

1 Attachment(s)
thank you Ron

After doing some research I can see why there is a ply vs mdf debate. My original intention was to use MDF for the front panel and ply for the rest of the speaker to gain strength. I am not sure how to finish the ply edge where the chamfer or radius is. I saw P10 ariel example and it looks great but will not really fit our decor. My original thought was to use some air ried oak I have and glue it to the mdf or plywood aka Troels Quattro. but after reading about solid wood horror stories I dont think I want to risk it. It looks like ply has some advantages in mounting the speakers and chamfering behind the speakers.

Would 3/4 construction ply make a better brace than MDF? I have some on hand. I can add oak braces to the mdf

Because I have to have thicker sides I am thinking of basically wrapping the whole speaker in 3/8 hardwood ply if I can find it. That will make the baffle 1 1/2" and the rest of the speaker 1"

I want to maintain the smallest footprint possible. This project started because my speakers were too big and I thought I could get by with less.

Does damping material like Bitumen make sense? on some sites it seems to have fairly dramatic impact. would it sub for thicker cabinet walls? do you have to buy it at electronics store or can you find it at lumber yards?

right now the sides are 11 7/8 vs 11 1/4 but I was going to use that space with the thicker front baffle.

I only have a pic of the crossover (see attached)and I spent quite a bit of time trying to figure out which crossover it is and I dont think it matches any of the crossovers its not the original or Jims or Jeroen on the dutch site. but the components look expensive. There looks like foam dots on the tweeter so I will assume it is some version of the original.

I have most of the tools I will need router bits and a way to cut circles I thought I would make a circle jig.

What gauge wire do you recommend? Solen uses 16 gauge in the kit at 1.30 a foot I figure about 40 ft?

thanks again for your advise and help

Ben

8ntractor 15th November 2012 07:07 AM

hobby hi fi has an article on coatings braces they recommend ceramic tile???? has anyone tried that? or bitumen and felt ?

8ntractor 15th November 2012 07:29 PM

I found a place that carries furniture grade plywood and has 3/4" baltic birch. I guess my next question is am I better off with 3/4" birch and bituman and felt per this article http://http://www.hifi-highend-selbs...ersteifen.html or should I buy 1/2" plywood and double it up. Another alternative is to add 1/4" of ceramic tile? Either way I would like to maintain the 9" width and add depth to maintain volume. I see that Troels uses the bitumen/felt combo. The other interesting article is this use of tar paper in a 1977 document from the bbc.( to big to upload) To Rons great point I want these to be done well as I may be with them for a long time.

So here is a summary of what I feel my options are the original volume without holey braces = 4050

1) front 5/8+1/2 birch ply- 1/2"+1/2" side 3/4 MDF Back
od=9 X 49 1/2 x 13 5/8

ID 7 X 48 X 12 = volume =4032

2) front 5/8 ply + 3/4 mdf 3/4" birch ply sides 3/4 mdf back intermittent tarpaper and felt.

ID 7.5 X48X 12.5 =4500 less 1/4" per side for tar and felt volume = 4032

3) same a 2 but with intermittent bracing and ceramic tile to hold close to 4050 volume.

4) same a 2 but ceramic tile the outside of the speaker sides and top?

thoughts?

planet10 15th November 2012 09:05 PM

I cannot get excited about the bitumen & felt. Build it from 18mm quality ply (they may call it 3/4" but it is VERY unlikely to be that, particularily if it is a 5x5 sheet.

If you find that you\'d still like more on the side panels, laminate some 1/2" solid wood
"decorative" panelson the side like Revel & Usher do.

Keep in mind that Joe thot it fine to use unbraced 3/4" MDF on the original, 18mm ply is akin to 1 1/4" of MDF. Don\'t overthink it.

dave

8ntractor 15th November 2012 11:02 PM

Thanks Dave

I have been thinking hard about it and trying to do as much homework as possible I like the idea of laminating ribs on the outside of the speaker. the speaker would maintain a smaller look yet be structually stonger. I found a place called commonwealth plywood that is advertising a wide variety of furniture grade ply and baltic birch. Only about 65km away too. Using 18mm plywood will simplify my life for sure. should the braces be ply also? I would like to use vendors that support this site for the extras that I need wire, polyfill, possibly a new crossover who would you recommend? thanks
Ben

planet10 15th November 2012 11:36 PM

We use plywood for braces. Hardwoods could be a bit better, but we\'d rather save that for the outside.

Bob at CSS is a big supporter... he is also the best conduit into Canada from Parts-Express. Both him & i can get stuff from Madisound. Solen isn\'t a big supporter but their caps & chokes are defacto items. There is also Q0Components/McBride in Ontario.

If people start poking some of the non-supporting vendors about diyA they will realize it is worth their while to have a larger precence.

dave

dave


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