My speaker build...about time I showed you - Home Theater Forum and Systems -

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post #1 of 32 Old 06-19-09, 08:13 AM Thread Starter
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My speaker build...about time I showed you

Hi guys, been a while since I posted, and I keep getting a friendly reminder to get in and post! So I am! So there!

And also, I must acknowledge Sonnies enthusiasm and 'welcome back' the last time I posted, so this is a special one just for Sonnie. Don't we just love him??

I am 95-98% finished, so as good a time as any to show you all. I hope that there are a few ideas here that might help/inspire others with their builds. Including one or two that, although I ended up not using, could be valuable to others.

Have had this basic layout for years, in what was basically a 'test box' that, to put it mildly, does not look too flash hot.

So much so, that one wit christened them the 'frankenspeakers', and the name has stuck in a rather affectionate way. May as well introduce the franks now so we can see what we started with.

Ta da!!

Ok, when this pic was taken the driver complement was an 18 inch PHL (7030), 6.5 inch PHL (1660) and a cabbasse tweeter, DOM 40. Ha!! As the build basically started a year ago (yes, serious!) a few driver changes have been made.

I now run a morel tweeter...unsure what model it is, it has been laying around for years and there are no markings on it whatsover, and memory...well it has faded shall we say? I have also changed the mid to a PHL 1360. It too has been laying around for yonks. For a long time I did not bother trying it, as I figured 'one PHL for another PHL, can't be too different' yeah?

Boy, was I wrong! I decided to give it a try as a direct result of the build, ie 'I should finalise all the driver choices before I go too far' type of thing.

glad I did.

So to the build, first off my biggest problem went something like, 'just HOW do I get a hulkin 18 inch driver into a design that looks halfway decent??'

After a lot of doodling on bits of paper, I came up with an idea that looked pretty good, and one that I doubted could be bettered. To get a bit of a feel in the real world, I made a little model of it. That will help give you an idea of what it is starting to look like, but I also feel a bit of a 'story' could be fun. Ie, will take you through the whole process.

The model

and the front view (needed to understand the 'concept' behind it all)

So, from the front view we can see that there are basically three sections, the base, middle and top, with an increasingly steep angle on each. So far so good.

I then had to work out how to build it, and work out the plan view. The how to build was easy, three sections stacked upon each other. A bit of fiddling with a compass produced the following formula

Hope you can see that OK...on the right is the elevation, on the left the plan. What is important with the plan is that it is all based on compass swings, to a set ratio of the dimension (taken from the elevation) of the relevant part of the baffle. The pic might not be very clear, but as you can see from the front view the dimension changes as we rise up the baffle, and at each succeeding slice (tho the formula remains the same) the radius swings change in step.

Clear as mud right? (EDIT, can see the pic is clear enough, so everything hinges on the 'x' dimension (from the front view), and the radii at each slice has the formula '1.2x' or whatever etc etc)

So I rigged up a router on a swing arm, where I could vary both the swing radius, and the pivot point that it rotated about

There is a cut piece of MDF in that pic.

I won't go into too much detail of the intervening stages, but will show a pic of the early days construction, as it will explain the 'brainwave' I had that sped things up.

That was mucking about with the top section (turned out fine BTW), every third or so slice had it's own skeleton rib (progressively changing per the swing formula), which was then bogged to form the surface.

Lot of work ha!

Brainwave!! Forget how it came up, but concrete was mentioned, and I realised that if I made it out of concrete (yes it is!) then all I needed was the top and bottom of each section, and could form the concrete with a straight edge, using the mdf formers as a guide.

You can see in the background a finished box, and in front of it the seperate sections of the one still to be done. The number of skeleton ribs required is vastly less than the earlier method, and hopefully you can visualise using a straight edge against the top and bottom of those sections to form the concrete...?? (of course I had to nail a few backing pieces in to pack the concrete against)

Here is a middle section concreted

All I had to do was to make the slices at each change in profile of the front elevation, so with a few dowels they could stack on each other, yet track the changing front profile (boy, I hope I'm not confusing youse all!!)

A shot from the back of a finished box. well not glued together but the three sections stacked on each other

I need to backtrack a little now, to give something that others might find useful in any curved builds they do. And it might be a bit more digestable if I start a new post.

PS, sorry about the slight miscalculations with the image sizes, means you have to scroll slightly to get it all.
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post #2 of 32 Old 06-19-09, 08:32 AM Thread Starter
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Re: My speaker build...about time I showed you

Ok, when I first started I was doing 'every third layer' by cutting the relevant skeleton rib with the router. I then glued 'tons' of little blocks in between each layer to gradually fill in the body of the section.

may as well show you all for a bit of a giggle

As I say, since those early days I went to concrete, but back then I was stuck with trying to get a good finish. I needed that because at that stage I intended to veneer it all, so a good surface was required.

Bog got me a lot of the way there, but not good enough to veneer on. I then found a neat trick, and this is what may be of use to others here (even tho in the end I didn't use it as I went to concrete)

I basically skinned the the section with curved mdf, and it is the curving technique I want to outline.

It is all in this pic. I used cloudy ammonia, just painted it on the mdf (it goes kinda green) and then the mdf goes pretty flexible. Simply affix it to the former you want the mdf to bend to, and wait for the ammonia to evaporate. The mdf is then formed to shape.

You can see in the pic a piece of formed mdf, and the little gas bottle I used to demonstrate the trick with. The broken piece of mdf next to it shows what happens when you bend a non treated piece around the same gas bottle, in short you can't.

Not limited to three mm mdf either, here is a 16mm piece of mdf that I treated with ammonia and bent around (a larger of course) former

So, curved speaker builders, off you go!!

Hmm, maybe I didn't need to outline it in a seperate post after all!!

Anyway, here is a top that was skinned by curved mdf

that went into the bin heh heh, as I started after that on the concrete model.

Hope that ammonia trick can be of use to some others.
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post #3 of 32 Old 06-19-09, 08:55 AM
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Re: My speaker build...about time I showed you

Terry... what in the world are you doing man... that is wildly cool!

You gonna have to quit waiting so long in between posting.

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PremierHomeAudio: Denon, Marantz, Onkyo, Yamaha, Sony, Pioneer, Def Tech and more. Shoot me a PM!
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post #4 of 32 Old 06-19-09, 09:14 AM Thread Starter
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Re: My speaker build...about time I showed you

Ok then, all the planning, calculating and building the router jig etc took a while. As did the first way of building with blocks then onto the concrete method.

Funny how once you get an idea in your head that it can tend to block new ideas from coming.

As I said, I always had the idea of vennering the back, and tossed around heaps of ideas about what to do with the baffle, special paint effects, whatever. I leaned towards using vinyl on the front baffle, but wondered whether or not I could get it to stretch over it.

BUT, how to veneer the box?? I mean not a lot of leeway for mistakes right?? I seemed to have a pretty good match between each section, but even little things like getting a perfect veneer joint at each the project basically sat at two concreted boxes for a few months as I pondered how to do the veneering.

Then....the inspiration.

(please have a look at it, to me at least they are stunning)

See what I mean about the first idea stopping new ones?? All that time I pondered how to veneer the box and put vinyl on the front, NOW all I had to do was swap them around! duhh. Simple, vinyl on the box and veneer on the front!!!

Next day went out and bought some vinyl to try, success!! (tho to be honest, for a while there I didn't think I'd manage to get all the wrinkles out)

Raw box, not even glued together yet (can just make out the tape holding the sections together under the vinyl for the trial)

Excellent, and even if I say so myself it looks pretty promising.

So for the finished version, the only change (apart from actually gluing the sections together that is ha ha) was that I put firm foam under the vinyl. Gives a real nice feel to it.


(ok, that pic is a bit out of order, as it has come after working out the baffle and top, but still a shot of the vinyl and maybe an indication of the foam underneath? ie it has a 'spongy' quality to it)

So the boxes were sorted, now had to work out the baffle. (note the fully planned procedure in play here!)

Won't go into ecrutiatingly boring detail, but in the end decided on a roundover, with gently sloping sides

I also stained the veneer quite dark, and you can see that as well as the roundover.

Here is a veneered baffle, not yet stained, on the box

Have to take a few more shots, but they have been stained and almost done.

A hiccup was found tonight, basically the baffle (made up of mdf glued together) is warped!!! How did that happen? I mean, if it was solid wood that had a face removed I could maybe understand how it could warp or cup, but mdf????

Anyway, think I have found a solution, and should know for sure tomorrow. NO WAY am I building the baffles again! Still, I have not got recent pics but soon will.

Pretty sure I can work around the problem, and if so then within a week I will have the drivers in the box and start measuring and calibrating. Oh, forgot to mention before now that it is a fully active tri amped system, run by a deqx unit.

So even tho the basic system has been running for years, new boxes etc means I redo all the measurements and calibrations again.

So soon more up to date (and hopefully completed) pics, and measurements..we all love measurements yeah??

I may start a new thread on one aspect of those measurements, think I have found something useful that may help others.

And would be my little contribution to HTS in (part) exchange for the wonderful gift of REW given freely and without conditions by the wonderful people here. (I take a liberty here) by thanking John and Sonnie and Bruce and Wayne et al on behalf of all HTS members. (arrogant are'nt I for assuming that role??)

Anyway, more on that use of REW when I start the new thread.

For my system, what comes next (with a vengeance) is room treatment, which will be another huge saga, mainly due to the aesthetic considerations imposed by my room and historic house we live in. So that too will be chronicled.

But hey, maybe I should just finish these first??
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post #5 of 32 Old 06-19-09, 09:22 AM Thread Starter
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Re: My speaker build...about time I showed you

Sonnie wrote: View Post

Terry... what in the world are you doing man... that is wildly cool!

You gonna have to quit waiting so long in between posting.
hey sonnie, thanks man. been busy kapiche? besides, you can see how slow I am in posting yeah? fixing all those hamfisted spelling mistakes (a few beers don't help either)

was gonna ask whatcha doing up so late...then realised it was me that was up late ha ha

anyway, more in a few days I'd say. thanks for your interest
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post #6 of 32 Old 06-19-09, 01:18 PM
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Re: My speaker build...about time I showed you

It's good to see something different... Nice Job.

I really like the vinyl covering. I almost tried this on a baffle once.
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post #7 of 32 Old 06-20-09, 03:49 AM
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Re: My speaker build...about time I showed you


I have got to try the MDF Ammonia Trick THAT could come in handy making some pretty sweet custom speaker cabinets. I'm happy to hear that it works on 16mm (1/2") as well. I'm planning some computer speakers and will likely use this method in the box design.

Thanks for the awesome ideas. Keep the posts coming!


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post #8 of 32 Old 06-22-09, 01:13 AM
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Re: My speaker build...about time I showed you

That curving trick is way cool. If I ever build curved mains, I'll have to consider that. Thanks for sharing!
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post #9 of 32 Old 06-29-09, 07:21 AM Thread Starter
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Re: My speaker build...about time I showed you

keelay wrote: View Post

I have got to try the MDF Ammonia Trick THAT could come in handy making some pretty sweet custom speaker cabinets. I'm happy to hear that it works on 16mm (1/2") as well. I'm planning some computer speakers and will likely use this method in the box design.

Thanks for the awesome ideas. Keep the posts coming!


ironglen wrote: View Post
That curving trick is way cool. If I ever build curved mains, I'll have to consider that. Thanks for sharing!
cheers guys, hope it gives you enough to experiment with for your own builds.

A few quick notes, 16mm is more like 5/8, 12.5 mm is half inch.

You must bear in mind that the thicker the mdf is, and the smaller the radius the more force required to bend it and hold it. 3mm (1/8) is very easy indeed, as would 6mm (1/4) be. If you wanted quite thick walls, then I'd suggest laminations of some sort.

In any case, experiment and good luck!!

A cut and paste from the original build thread on diy (so if some things don't quite make sense, it's prob because this thread was a synopsis)

*************************************************************************** ***

Did I ever tell anyone I hate hi fi? that I hate speakers? that most of all I hate building them??!!

You saw earlier that the stain was too dark so I stripped it back and started again.

Still could not quite get the colour of my sample, but kept going. Dunno why, but the finish with the tung oil just would not come no matter how many coats!

Got sick of it, and rang a mate and asked him if he could spray them for me, sure no probs. Set up a time with him, and-yep-stripped it all back yet again to bare wood.

Drove two hours to him on a late sunday, and when I get there he has no stain after all!! I HAD asked him if he wanted me to stain it before I arrived....5.30 or so on a sunday afternoon, nearest bunnings is thirty km away, give me a break!

There was an 'old timer' there doing some stuff, had a lot more experience than my mate with spraying etc, assures us that with not the slightest shadow of a doubt, not matter how well I had stripped them, there would still be oil on the pores and that the lacquer simply would not take.

load them back into the car, and drove home again.

Geez I hate building speakers!!

BUT, re-stain them for the third time..hey!! getting the colour I wanted, apply the oil again and blow me down if the shine etc is now appearing!!

go figure. Guess they needed that round trip?

Sooo, did I ever show you my base plate and spikes??

Ha ha, the spikes are made from 16mm threaded rod! Be strong enough ya reckon??

It was just the nature of the beast, mainly due to the vinyl, but as the baffles could not be glued (due to the vinyl, and how do you ensure an airtight seal, a bit hard to apply weights on the baffle with this shape), the entire thing is bolted together.

I am such a sloppy worker, that turned out to be a good thing. I had to re-vinyl the two boxes...I managed to gouge a hole in one tripping over stuff laying around, and the other got bog on it that I could not get off.

Having all the pieces bolt together means I can always pull it apart in the future and do things like that.

Hmm, what if I decided on pink vinyl for example? easy peasy!

So that was the base plate on one, with the other sitting nest to it with a spike in place and a spike sitting loose. Just turned up the holders on the lathe.

So screw the bottom on, bolt the baffle on then the top plate, then bolt the midrange chamber in. Bit of a pain, but watcha gonna do?

Hmm, all these potential leaks, the next step is to put it together, cross my fingers and hope like crazy that the thing is airtight.

A quick shot on the way inside, basically wasting time and putting off the big test.

and another

A shot of the old (RH) one from the LP

and a shot of the new (LH) from the LP

They are pretty dark (as can be seen from the outdoor shots) and my room is dark, so I had to slightly lighten that shot of the speaker.

Well, good news, no leaks! phew. Tonight the second was hauled in a fitted up, again no leaks and I am now listening to them as I type.

I can tell you, a bit of a relief!

If I had thought about it, I probably would have put a hard piece of wood to mount the speakons on (still under the vinyl tho), rather than on the foam under the vinyl. It compresses slightly, not too big a deal and nothing important enough to feel I have to fix.

I will probably put another couple of coats of oil on the top plates later, but I'll just let it all harden up for a couple of weeks. then a good wax, and it is finally finished.

It is very close to, if not actually, a year since I decided on the design and built the little model to see if it had legs.

And it feels it!
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post #10 of 32 Old 07-01-09, 11:29 AM
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Re: My speaker build...about time I showed you

Those look awesome.

That's all I can say.

Just awesome.
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