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Old 20th March 2014, 01:32 AM   #1
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Default The beginning of a tower speaker and center channel build

The towers I am building will measure 49"H x 7.75"W x 12"D, with the front baffle being 49" x 7.75". I want to create an MTMWW design, sectioning off the woofers into their own ported space. The space for the woofers will be 1.16 cu ft, leaving .55 cu ft for the midranges and tweeter.

The drivers:

Tweeter - Dayton Audio PT2C-8

Midrange - Dayton Audio ND105-4

Woofer - Dayton Audio DA175-8

I'll add some additional bracing, but the interior of the box will consist of 2 chambers, the bottom one for the woofers, which will be ported, and the top chamber for the midranges and tweeter, which will be sealed. Would someone be able to use some modeling software to help create a crossover system? I'm fairly open to different driver suggestions if these don't pair well. The amp needs to see between a 6 - 8 ohm load. At this point, the only reason of the mention of the center channel, is because I would like to use the same midrange, tweeter, and crossover (minus the woofer) in an MMTMM design, and would also like some input on that idea.

I'm extremely new to speaker building so any and all advice/criticism is welcome.

Last edited by username8611; 20th March 2014 at 05:47 PM. Reason: condensed and simplified
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Old 20th March 2014, 08:52 AM   #2
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Looks good so far. What are your plans for a finish on the main cabs?, bracing inside?
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Old 20th March 2014, 02:24 PM   #3
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Unfortunately my lack of woodworking skills and tools means they won't be changing a whole lot from start to finish... I found some nicely rated veneer on parts express that I want to try. I can prep the wood and everything, but I don't have anything for forming shapes; I might buy a router to round off the front baffle, but that'd be it. I need to edit and reword my main post since I think its a bit too scatter brained and asking for too much at once, but I think I have my drivers picked out. I need to measure inside to find the exact volume, but I want to section off the 7" woofers into their own compartment and tune it with a port, while the leaving the mid ranges and tweeter in a separate sealed compartment. Wherever I add the plank for the woofers, I'll count that as a brace, and maybe add a few at the top, with some holes in them so they won't seal off any other areas.

Any and all advice is welcome, I think I'm becoming pretty dead set on using (from top to bottom) MTMWW for the main speakers. I keep reading that MTM designs have good lateral dispersion and limited vertical dispersion, which would be perfect for our rather small basement with standard 8ft ceilings. I'm far from an audio engineer, but that plus ribbon or planar tweeters should help me achieve a pretty wide sound stage, wouldn't it?
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Old 20th March 2014, 09:17 PM   #4
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Could I use this, except wire the woofers and midranges in parallel with each other? It has a 2db bandpass gain which will help the midranges spl match the woofer's, and then I could use an l-pad for the tweeter. Assuming I would wire the other 2 speakers in my MTMWW in parallel with their match, using 8 ohm speakers would result in each driver circuit (mid or woofer) seeing a 4 ohm load, is that right? Then wire the woofers to the mids in series, to bring the load back to 8 ohms, then the tweeter in... series with the mids?

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Old 20th March 2014, 10:24 PM   #5
system7 is offline system7  United Kingdom
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My friend, I think this is WAY too ambitious for a first project. You don't even have a crossover, and I suspect 4 ohm midrange will take impedance far too low. Even conventional 3-ways often hover around 4 ohms impedance.

3-Way Classic

You COULD take any good conventional 2-way design, and double up the woofers wired in series for the same SPL or loudness. The bass crossover gets coils and resistors doubled up in value, and the capacitors halved in value, by one of those neat quirks of the maths. The treble filter is unaffected. That gets you your MTM with a highish impedance. Come to think of it, you could do something similar with a 3-way.

The parallel wired MTM, by contrast, takes impedance lower and drives the tweeter harder.

I don't think anyone here has the time to nurse you through this, so I'd suggest you build an established design within your capabilities.
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Old 21st March 2014, 04:32 PM   #6
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Thanks for the link, do you have any resources for me to learn how to build this speaker? I have no deadline, so I can learn but I don't know where to find info regarding how to use any modeling software.
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Old 22nd March 2014, 12:53 PM   #7
system7 is offline system7  United Kingdom
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I didn't want to sound too discouraging, but I do think you're taking on a huge project there. At least, for someone new to this.

I can suggest you look at some similar projects, like this Visaton Experience V20:
EXPERIENCE V 20

Visaton provide a free Sim program called Boxsim:
Downloads

They also give away the BPJ project files which you can copy to the projekte folder in Boxsim, and it has done all the work for you including cabinet:
Boxsim Projektdatenbank Experience V20

Maybe not exactly what you are looking for, but you could then try Visaton's own ribbon tweeter in the sim and see how it all looks. Boxsim is incredibly versatile when you get to know it. You can fiddle with cabinets and optimise to your hearts content. I got the hang of it in a couple of hours. Probably best to learn your way round with a simple 2-way at first.

BTW, your idea of wiring the drivers in series with an MTM to raise the traditionally low impedance is quite feasable. You can do that in the sim too.
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Last edited by system7; 22nd March 2014 at 01:02 PM.
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Old 22nd March 2014, 01:09 PM   #8
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Hi, I'm not a wood pro, but I can work a jigsaw and a router. I would ENCOURAGE you to start with the recommended project. Nothing worse than disappointment at your first try. Having built several 2- 3 way small speakers and now working on a big (2 cabinet 51 inches high) system, the hardest hart isn't the wood, it's the crossover !!
Again, a first attempt pre designed kit will really encourage you to do something more to what you like as your next attempt. Be warned, there will be many.
The DIY audio community will assist you as you go. They've helped me a lot.
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Old 22nd March 2014, 01:50 PM   #9
system7 is offline system7  United Kingdom
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As it goes, I believe the drivers for Visaton are available in the US, Jvsantosmd.

There IS a way of making your own MTTM easily enough out of two-ways. You'd probably want to get the tweeters as close as possible to each other, but there is a school of thought that MTTM works even better than MTM because it matches the drivers for a cylindrical response.

Not as daft as it looks.
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File Type: jpg Poor_Man's_MTTM.jpg (112.8 KB, 118 views)
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Old 22nd March 2014, 04:20 PM   #10
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Thanks for the posts guys. System7, I checked out those links in your first reply, there are some really good designs. I have some questions about PCD if anyone is familiar with it. I admittedly havent read the manual yet so ignore these if they are super easy questions, but I did search and skim the manual, (search isn't the most friendly in excel).

If I'm trying to build a speaker for an 8 ohm receiver, what is the minimum recommended system impedance that should show? I get dips down to 3 ohms, I have a feeling it would throw my receiver into autoprotect almost right away.

Phase - I know phase is vital when talking about left and right phase of stereo speakers, so I bet it's just as important with crossovers. How far off can phase be before I would be able to hear it in the speakers? Do all the vertical phase lines need to be lined up, dead accurate?

System response vs power response. System response is what I'll actually hear, and power response is what the drivers are actually playing, is that correct?

How do I get PCD to display a wiring schematic?
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