# My First 3 Way build



## beachedwahle (Feb 25, 2011)

Hello all, 
I am a new member to both Home Theater Shack and diy world and would like some input and suggestions on my first build. 
The components on this build are not the highest quality, and I do not expect the end product to equal those of thousands of times more expensive, however, it's my first build and any help would be appreciated.

I am going to model it after the ATC SCM25A Pro. However mine will be passive
I am working with the following drivers Per side:
Vifa DQ25SC16-04
Silver Flute W14RC25-04
and this is where I run into my issues
Woofer from Behringer B2031P (4ohm 8.75" long throw poly woofer - that's all I know about it)

Because I do not know much about the Behringer woofer and am working on a budget. I am unsure of how to create the cabinet to configure my drivers like the ATC SCM25A Pro.

Some of my initial concerns are, 
Box dimensions, 
Separate internal enclosures for each woofer, 
Size, length, area, etc, of ports.

Any help would be appreciated.
:dontknow:


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## Zeitgeist (Apr 4, 2009)

When you talk about the ATC SCM25A Pro, is your intention to configure the driver arrangement like it?

Or mimic the performance of it? Or the dimensions?

From the sounds of it, you have some good drivers, but they really need to be matched well, if you're going to come out with a good speaker - especially if you're going with a passive crossover.


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## beachedwahle (Feb 25, 2011)

My intentions I suppose are to mimic all three, dimensions, configuration, and similar performance. I would like to be able to use them both near-field stereo and in a surround mixing or HT setup.
I am actually going to use an active crossover, because I have a stereo 3 way crossover already and I would rather use what I have than spend even more money that I don't have
I will be powering the pair with Carver amplifiers and an NAD preamp if that helps any as well. 
Thanks


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## robbo266317 (Sep 22, 2008)

Welcome to HTS. I look forward to pics of your build.

Cheers,
Bill


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## beachedwahle (Feb 25, 2011)

Anyone? Bueller, Bueller? 
:huh:


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## Zeitgeist (Apr 4, 2009)

Well, I think it would be helpful if you gave a little more information on what advice/help you're looking for.

You'll be able to get rough dimensions from googling the speaker you are "cloning"... I'm not sure what to say about the Behr driver, I know those monitors are very good, but re-using a driver from another speaker gives you a somewhat "unknown" driver to work with.

I imagine that damping is probably very important to do correctly, since it's my understanding thats double important in near-field monitors (which I think the ATC is?)

Regarding tuning, do you know what the speaker is tuned to? It's easy enough to come up with a port dimension, if you have a frequency in mind.

My guess regarding chambers, would be that the woofer is chambered separately from the other drivers.


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## 1Michael (Nov 2, 2006)

So you have 3 drivers that you picked at random...a 3 way crossover that is already built...and you want it to sound like another speaker system...and now you want help after the fact...
You might want to do a little more reading because that is exactly the way to go about creating a failed project.
Oh and you want to do a 3 way as your first project.


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## GranteedEV (Aug 8, 2010)

Hi, I mean this in a totally polite way, but I think you're attempting something which is not likely to have a good end result. 1michael is on the dot about just how many things have _already_ gone wrong with your build.

my advice is to start with measurements measurements measurements.

You need to measure driver impedance, driver sensitivity, driver on-axis freqency response, driver off-axis frequency response, phase response - all in the baffle and preferably outdoors. You can't use any old crossover - it's like trying to build a toyota camry with random parts and a 1960s engine design schematic. Here is a page you really need to read:

http://www.troelsgravesen.dk/crossovers.htm

And read it over twice.

If it's not too late, your best bet would be to start with drivers that will work well together both on AND off axis. The Dayton RS52 is a good dome midrange which might have good off axis response and stored energy to work with. If going passive3 way without much knowledge of speaker design, an existing design is VERY MUCH the way you almost NEED to go if you want things to sound coherent and lifelike. The Zaph ZDT3.5 might be a place to start.

Going active is a very worthwhile venture as well, especially for the unexperienced. I wish you luck, but you may need a miracle. :T


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## beachedwahle (Feb 25, 2011)

Thank you,
Let's start over then. I have obviously overlooked far too many things here and that is my error. 

I have these components already. 
Vifa tweets
Silver Flute woofers
behringer woofers (for what they're worth)
Rane AC 23 active crossover. 
Amplifiers to power each section.

Can I incorporate all these into a design with a small footprint and have a successful build? I have limited funds and am new to this world of diy. I welcome any and all suggestions to turn this build around with what I have, if at all possible.


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## GranteedEV (Aug 8, 2010)

If you have limited funds, designing your own speaker is probably going to be out of the question, because at the very least you would need to purchase a measurement microphone, mic preamp.

Luckily since it's an active crossover, you can probably skip getting a woofer tester, and maybe it can be salvaged. Active is a good bit easier to work with than passive, at least.

Where abouts are you located? Perhaps you can meet up with someone to help measure your gear for you.

What you need to start with is a baffle. The ATC unit you're looking to recreate is likely not the ideal design for a baffle layout for starters. You also want to round edges, offset small drivers, 

Next, in that baffle, you need to measure each individual driver. You need to measure not only frequency response and off axis frequency response, but also determine where any cone breakups might be so they can be placed well out of the driver passband and notched accordingly.

Your goal is hopefully to be able to get crossover frequencies where the off axis response as far out as 60 degrees is matching between the individual drivers (directivity index matching) and remember that using a 2nd order electrical filter may in fact implement a total 3rd or 4th order acoustic rolloff on a driver... that's where on axis frequency response comes into play.

Also remember that crossing over too low or too high for a given driver will introduce distortion. You may in fact find that some of your drivers simply can NOT work with each other effectively.

You may also need to apply equalization to on-axis frequency response to smooth it out via the crossover. I don't know how functional your Rane unit is in this regard. A parametric EQ can also be used ahead of the signal. Don't bother trying to equalize below the shroeder frequency in-room, and don't overzealously equalize either. Hopefully you can get +/- 2db on axis tolerance from around 200hz to 8khz or so, and a smooth off axis rolloff as you get higher in frequency. 

Phase is also a factor you need to consider... Just try to match phase between drivers at the crossover frequencies. Sometimes inverting the leads is all you need to do.


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## beachedwahle (Feb 25, 2011)

Have the measurement mic and preamp. No worries there. It's not an earthworks measurement mic (wish it was something nice), but it's a measurement mic that I know and have never had an issue with. So I got that front covered.

And I'm near Bloomington, IL if anyone wants to help with the project. 

Plan was to flush mount everything and round corners and edges already. But always good to hear I had something right. 

As for measuring, 
Where would you recommend measuring at and from. (location and distance) and should I just push pink noise? or do you have something else you would test with?
Could you explain what you mean by cone breakup? Just for clarification

Does anyone have a Configuration they might recommend for a smaller footprint 3 way build?


Thank You for all your help. This is going to be a learning experience, and hopefully I can build something decent with all of this.


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## GranteedEV (Aug 8, 2010)

beachedwahle said:


> Where would you recommend measuring at and from. (location and distance) and should I just push pink noise? or do you have something else you would test with?
> 
> 
> Location - outdoors
> ...


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## Ed H (Mar 5, 2011)

Wow. A $7500 speaker? 

http://www.vintageking.com/ATC-Loudspeakers-SCM25A-Pro-Pair

_The SCM25A Pro incorporates ATC's proprietary short coil seven-inch carbon-paper woofer, a three-inch soft dome midrange driver and a one-inch silk dome tweeter in a ported enclosure that measures 10.4 inches (264 mm) (H) x 16.9 inches (430 mm) (W) x 16 inches (408 mm) (D). The integrated tri-amplifier generates 150 W RMS for the woofer, 50 W RMS for the midrange and 25 W RMS for the tweeter. The passively cooled amp pack also features FET limiting. The crossovers are all 4th order, critically damped with phase compensation._

Did you want to use this for home theater, music, both? What size room? It is going to take a TON of work to DIY something like this. Have you reviewed the hundreds, possibly thousands of well documented DIY speakers designs here and on other sites that would likely exceed your needs with no guessing required? Only tools, patience, XO parts, and different drivers?


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