# 2-way x-over design, non-traditional x-over, works?



## mvw2 (Oct 2, 2005)

Well, I'm building a 5 channel home theater setup to replace an old ghetto setup.

I'm building a decent setup but am also gearing at a relatively affordable price point, i.e. tons of bang for the buck.

I settled on what I consider very good and well priced drivers:
Tang Band W6-789E 6.5" woofer - $40
Tang Band 25-1719S 1" tweeter - $22

These aren't uber cheap but they are very well priced for what they do. The broad frequency response of both also make them pretty easy to work with.

I used Passive Crossover Designer v6.2 made by Jeff Bagby, a widely functional Excel spreadsheet that makes use of a speaker's FRD and ZMA files (made with SPLTracer).

I ended up with a little hybrid x-over. It uses a first order lowpass filter for the woofer and a second order high pass filter for the tweeter. I have parallel resistors on both to aid in shaping the response.

The goal of the x-over was a smooth frequency response across the spectrum, a flat inductance and zero phase across the spectrum, well at close as possible at least.

I ended up with 
first order lowpass for the woofer like
L = 0.18mH (R = 0.18ohms)
Rparallel = 2.5ohms

second order high pass filter for tweeter, reverse polarity
C = 27uF
L = 1mH (R = 0.48ohms)
Rparallel = 4ohms

I've gotten into the habit with this stuff of adding an inline resistor into the circuit. It seems to do a couple things. One, it seems to address inductance variation, and two, it gives me more freedom with the shape of response. However, it does lessen the roll off rate of the design.

I'm curious if this is actually a functional setup. I haven't actually built a setup using this type of design. Does it actually work like it looks like it will? I end up with a decently flat response, flat inductance, and pretty close to zero phase angle throughout on paper. I get an inductance from 20Hz to 20kHz that doesn't vary by more then 0.4ohms. I get a total phase across the spectrum that doesn't vary by more then a few degrees.

I tossed it in Speaker Workshop as well just to verify what the Excel program shows, and I'm sitting at a relatively similar result.

I uploaded the FRD and ZMA files for the two drivers I'm using so you don't have to go through the trouble of tracing them out yourself.

Anybody want to comment on and/or verify what I'm doing here?


No, I haven't fiddled with baffle diffraction, but I intend to round the enclosures quite a bit.

As well, I will address low end response with the enclosure design and will be a ported enclosure.


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## MiniVanMan (Jun 28, 2005)

You have no baffle step compensation in your circuit. Bad idea unless you plan on putting these flat against a wall.

Even then you should allow for a 1-2 db of BSC.


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## mvw2 (Oct 2, 2005)

True. I am ignoring that. My current speaker positions do place the speakers near the wall and in corners. I am figuring to not have all that much of a drop really. About the only real concern I have with the baffle is top end, so my main worry is just rounding the corners for the top end. The problem about worrying about the baffle step is the room is not idea and neither are listening positions. Because the environment is far from ideal, I just don't care about the littler details. Baffle step is important, but I'm not going to fret over a dB or two with this setup. The crossovers could always be adjusted in the future anyways. All I'm looking for now is decent hardware and a decently smooth response.


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## MiniVanMan (Jun 28, 2005)

If that's the case, then cheapen it up a bit and go for one of the cheap Peerless buyouts on Parts Express.

For example, Parts-Express.comeerless/Tymphany TPY06W04S0063 6-1/2" Woofer 6 Ohm | Tymphany TPY06W04S0063 6-1/2" Woofer 6 Ohm woofer peerless vifa bass mid midbass mtm coated cone 2-way npa00453

Just a thought. If you're looking to just slap something together, then go cheap. You won't get the extra performance benefits of the more expensive drivers.

I'm currently in the same situation as you. I'm going to use some $10.00 Vifa OEM drivers I have lying around for a corner placed loudspeaker.


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## mvw2 (Oct 2, 2005)

Well, it's only half a matter of staying cheap. For example, I can step to the 5.25" Tang Band and cut the woofer cost in half too. I can step to a little Dayton tweeter and cut the tweeter cost in one third. I kinda want the decent drivers just to have the decent drivers. Then I can simply change other aspects later on. The total system as of now will only run me around $600 when finished including wood. I just don't need to go terribly fancy given the crap environment that they're in. I don't want to account for things that won't matter anyways. That's all.

My curiosity of this thread is a little more in the idea of attempting to flatten the inductance and zero out the phase. This doesn't seem to be something really discussed, but I would think it'd be important. With the crossover setup I listed, I end up with a flat frequency response, a flat inductance, and a relatively zeroed phase over the entire operating range. It's not something I've seem commonly done, so I'm curious about it.


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## MiniVanMan (Jun 28, 2005)

mvw2 said:


> My curiosity of this thread is a little more in the idea of attempting to flatten the inductance and zero out the phase. This doesn't seem to be something really discussed, but I would think it'd be important. With the crossover setup I listed, I end up with a flat frequency response, a flat inductance, and a relatively zeroed phase over the entire operating range. It's not something I've seem commonly done, so I'm curious about it.


It's done quite often actually. First off, with a flat baffle, your tweeter sits a couple of inches forward (the voice coil that is) of the woofer. This automatically induces a phase shift. Not much of one, but definitely not a 180, or 360 degree shift. So, an odd order slope can help a bit. 

There's also nothing wrong with using the driver's natural roll off to help shape your response. Now, you're not talking about inductance, you're talking impedance when you say "flat". You don't need Zobel networks to achieve a flat system impedance response. You need logical crossover design. Zobels are used to get a bit more top end response out of your woofer. Pointless to me, because that extra top end response is usually well into the point of beaming for the driver anyway. Just get a better tweeter.

You didn't do anything groundbreaking, you looked to simplify. That's what crossover design should be. The idea that higher order slopes are "better" is plain bull ****. Use the shallowest electrical slope you can get away with. You'll ultimately end up with better polar and power response. 

Always remember, electrical response is only theoretical. Your target response is acoustic. That's a coupling of the driver's natural frequency response, baffle response, room response, and finally crossover response. So, the crossover is only a small portion of it.


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## mvw2 (Oct 2, 2005)

Yep.

Is there specific concern for non-flat impedence? I know it is a source of distortion if the variation is great and that an impedence spike can bump up the frequency response in that area. I'm not sure how much is acceptable though or how beneficial it is to attempt to flatten it.

As well, how big of an issue is phase angle. For example, different x-over designs will change the phase angle of the setup throughout the frequency response range. I would assume zero is ideal, but it's almost never achieved. There always seems to be some variation in phase. I would think this would throw off the coherence some. But again the idea of it being discernible is in question.


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