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Deep End DIY - My first speaker project

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So, something turned up the other day.  Whatever could it be for?  A Christmas project perhaps...

 

 

12 sheets of 32mm MDF 1200mm x 2400mm

 

 

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That might explain why I have been preparing Cut Sheets in AutoCAD...making a circle cutting jig for the routers...profile jigs for lathes and grinders...sharpening cutting tools.

 

 

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I am probably mad to consider building this behemoth...its weight will not be insignificant.  You can see the individual 32mm slices in green.

 

 

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Below is my first draft of the assembled horns.  Depending on what I find when messing with crossovers and time alignment in particular, I would like to get rid of the frame and anchor the upper components to the big Upperbass horn and make it look pretty.  

 

Those that have an eye for horns will notice the similarities with a famous feline system.  This is not by mistake.  I figure I can mess with this stuff for a decade before I get it right or I can blatantly copy someone that has by all accounts got it very right and massage it to my preferences and save about 8 years out of that decade.  Fingers crossed!!

 

Then there will be the mid and lower bass to sort out...but that will be done when I move into the new room upstairs.

 

 

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Hi Anthony that's a really brave project! Have you got someone in Brisbane to CNC it for you, If not I can recommend someone. Hope all goes well.

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Will all be cut by hand John...a labour of love in front of the Boxing Day Test match.  If all works out as planned (ha...like that will happen!) I will show a cheap and groovy method of building these things that anyone can use without need of a gargantuan lathe.  The profile templates will be CNC cut but no-one I have contacted so far can do it before Christmas...so maybe I will be cutting them by hand also.

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come on Anthony, you can do it mate :)

Alan

 

You are at least partially to blame for this escapade Alan...helping me find all these vintage drivers from around the globe...the project might still be a daydream without your input mate.

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I saw a need and yearning on your part, and you have the guts and desire to back yourself and work out all you dont have answers for right now. Those S2's and Fanes were details of the plan that emerged from the fog of the desire....You are firmly at the start line so good on you for that. Go well. It will all work out with a bit of persistence and seeking answers from those who have had the specific experience. Daydream might be....well....a bit premature? Lets call it a nightmare and then there wont be any disappointments or I told you's :) 

 

Keep us all posted. I would like a bit more details on those back chambers when you get to them-the volume bit. Cheers

Alan

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Hi Anthony, I see you got your MDF from DMK. We could have supplied and Cnced it for you! ( Sorry shameless plug!)

However I gotta hand it to you, cutting circles in 32 mdf wouldn't be my choice, but it seems you have a computer design, so it will be easy for someone to follow your tracks the Easy way!

looking forward to your results. Ps, I have a mate who is developing a lathe for jobs this size and bigger

! Sorry help after the event is No help! 

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If you don't mind me asking Anthony, how much did you pay for each slab of the 32mm MDF or was it cheaper for the pallet?

 

Thanks,

Brett

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If you don't mind me asking Anthony, how much did you pay for each slab of the 32mm MDF or was it cheaper for the pallet?

 

Thanks,

Brett

 

$88 per sheet delivered.  I got three quotes and DMK were the cheapest by a fair margin.  Didn't think I was going to save too much more on that price.  Good service from those guys.

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Hi Anthony, I see you got your MDF from DMK. We could have supplied and Cnced it for you! ( Sorry shameless plug!)

However I gotta hand it to you, cutting circles in 32 mdf wouldn't be my choice, but it seems you have a computer design, so it will be easy for someone to follow your tracks the Easy way!

looking forward to your results. Ps, I have a mate who is developing a lathe for jobs this size and bigger

! Sorry help after the event is No help! 

 

I got some CNC quotes and as you can imagine the prices varied substantially.  The cheapest price for CNC'ing once I took out the price of the MDF was about $500 (highest add $1k to that) but, and a big but, the cheap guys did not want to cut more than 25mm MDF and that would have meant about a quarter more glued joints which would make more work for me anyway.

 

So the plan is to use the circle jig for the initial cuts with one router and then use a simple follower in a second router to finish off the cuts.  Shouldn't take too long, and I don't mind a day or so of extra work if I can put that $500 into some other part of the speaker.  Every sheet of MDF has its own cut sheet already calculated so setting out the circles should be relatively straight forward and I should not have to think too much about it.  It took some wriggling in AutoCAD to get it all to fit on 12 sheets.

 

I thought of making a big lathe for turning the big horns (fairly straight forward to do) but my woodworking mate pointed out that the wood warps when it is spun and you don't necessarily end up with a perfectly round horn.  So we will use a slow spinning system that should be MUCH faster than a lathe and should give us a round horn.

 

@@Sparkle are you open next week?  Want to cut the profile templates from aluminium or ply? 

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mmmmmmmm 32mm  mdf drool. 

 

Was unloading it on Wednesday and the guy told me they do 44mm as well, but they aren't permitted to unload it by hand as we were doing it at the time.  Did some quick maths on the spot and I did not think I would be able to cut 44mm in the way I was planning so 32mm was still the right choice.

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Awesome project, I remember the days of cutting countless circles of MDF for horns :)

Care to share driver details and what you are thinking for under 100 Hz?

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You have the horn bug bad

And it's definitely in the deep end

I can't talk much as I'm kinda the same ;)

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Awesome project, I remember the days of cutting countless circles of MDF for horns :)

Care to share driver details and what you are thinking for under 100 Hz?

 

Drivers:

     Tweeter:       RAAL Ribbon

     Midrange:     Vitavox S2 (15R)

     Lower Mids:  Vitavox S2 (15R)

     Upperbass:   Fane Studio 8M (16R - original Fane production, not from the group buy - lucky me)

 

I will also play with an "Injection Channel" (ala Romy) using a vintage Goodmans fullrange driver (201c - 15R) as sort of a cohesive force to bring the big speaker system together.  Not sure how that one will turn out but it will be fun trying.

 

So as you can see, apart from the RAAL these are all hard to find drivers on similar impedance particularly suited for valve amplification.

 

Bass is the big question for me.  I would love to build a big bass horn but I just do not have the room so this limits me to direct radiators or tapped horns.  I would also like to have the flexibility to be able to physically time align the drivers and not rely on DSP to do that for me, so that rules out tapped horns and limits me to direct radiators.  Then I would like to run valve amplification for the 20Hz-100Hz region so I need to be really careful of back-EMF from the drivers, so smaller drivers with lighter cones and softer suspension are probably better here (in larger numbers).  So I have not made up my mind for the bass, but one thing is for sure, it will not be a half-arsed attempt because that large scale soft and realistic bass is just so vitally important in the context of the entire system.  I plan to first renovate the room, take some measurements and try to figure out the best solution from there. 

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Anthony, you are following feline fetishes (not unwise either), so why not go the multiple Scanspeak 25W/8565's. It would be very doable and compact. Chris told you what he thought of Romys bass.....

Alan

Edited by aertex

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I am probably mad to consider building this behemoth...its weight will not be insignificant.  You can see the individual 32mm slices in green.

 

Seems we have a similar xmas project.    I'm using a completely different construction technique though  (EDIT - cos mine is a bass horn) .....    (Lathes and grinders are a bit beyond my capabilities).

 

 

Good luck!   :D

Edited by davewantsmoore

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Anthony, you are following feline fetishes (not unwise either), so why not go the multiple Scanspeak 25W/8565's. It would be very doable and compact. Chris told you what he thought of Romys bass.....

Alan

 

Yes he did, and Chris is not the only one either that I have talked to that calls the feline bass as "best I've heard".  I have investigated just how cheaply I can get those drivers (or being Scanspeak just how much it would hurt!) and it is doable and it is my preferred option at this stage but I want to get some idea about room gain first.  Those bass line array's interact with both the ceiling and floor which is great if you have a flat ceiling, but my room has cathedral ceilings so they may well perform a little differently.

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Seems we have a similar xmas project.   

 

 

But I have a thread going...hint hint Dave (again).

 

 

I'm using a completely different construction technique though  (EDIT - cos mine is a bass horn) .....    (Lathes and grinders are a bit beyond my capabilities).

 

 

Good luck!   :D

 

I would like to read about your Christmas project and look at pretty pictures too.  Especially to see what sort of design you have settled upon.

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I would like to read about your Christmas project and look at pretty pictures too. Especially to see what sort of design you have settled upon.

Maybe I should send @@davewantsmoore a camera for Christmas? :D

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Especially to see what sort of design you have settled upon.

 

Rectangular mouth hyperbolic of about 60hz (exact dimensions to be finalised) ....  made of plywood.

 

Driver fires down, so a 90 degree bend.

15" driver.   Fs = 35hz  Qes = 0.35

Lowpass filtered for LR8@250hz

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So, got my profile templates cut in 3mm acrylic today.  Have a look at the photo below to see how the inner and outer profile templates crudely fit together (blank spaces is MDF) for the three horn channels.  For scale I have placed a 30cm steel rule on the inner profile template of the Upperbass Horn.  

 

All excitedly I laid these out and explained to my darling wife what they meant and all she could say is "that's too big".  I smiled, gave her a kiss and retorted "that's too late".  Hehehe.

 

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