# Looking at building a cheap 5.1 set - 3-way speakers - crossover help



## mvw2 (Oct 2, 2005)

Well, I'm looking at tossing together a very budget minded 5.1 setup. I'm currently running a 3/4" + 4" satellite but am looking at upgrading to something a little more capable. As it stands now, I'm looking at a 1/2" + 2" + 6.5" setup using very budget minded but easy to work with drivers.

The setup that I'm looking at is:
Tang Band 13-1264SE 1/2" tweeter
http://www.parts-express.com/pdf/264-840s.pdf
Peerless 830983 2" full range
830983 | Tymphany
Peerless 830657 6.5" woofer
830657 | Tymphany

The idea is simple. Pick drivers that are very affordable and that offer a broad, usable frequency response. I should have plenty of overlap, and the x-over networks should be simple to build for the most part.

Passive x-overs are things I really haven't looked much into, so it's kind of new territory. I would actually like to find some good software for setup, but there are also simple calculators out there that will give basic part values for a given setup. A couple things I will specifically address are the different ohm loads of the drivers and the different sensitivities of the drivers. Phase is something I'm unfamiliar with, but I'm aware that different x-over designs flip phase or something. A Linkwitz-Riley crossover is supposed to be equal.

So, is it as simple as picking a crossover point, doing say a generic LR2 x-over, integrate some L-pad adjustment, and say done?

I'll choose x-over points at 1kHz and 4kHz at the moment. The tweeter may be set higher then this actually, but I'll call that a starting point.

LR2 circuit:
Tweeter-Mid
HPF:
-3.32mF cap
-0.48mH inductor
LPF:
-5mF cap
-0.32mH inductor

Mid-Woofer
HPF:
-19.9mF cap
-1.27mH inductor
LPF:
-10mF cap
-2.55mH inductor

An L-pad would need to be integrated to fix offset sensitivities. The tweeter is 90dB, mid 85dB, and woofer 89dB.

L-Pad:
Tweeter:
-2.63ohm series
-7.71ohm parallel

Woofer:
-2.95ohm series
-13.68ohm parallel

I assume they can simply be installed as a "speaker" to the x-over network. I may look into finding a higher sensitivity midrange too, so I don't need to use the L-pads or need as significant a cut.

I mean, would something like this be appropriate?










I understand the parts values will not be that. This is just the "ideal" part values and I'd simply buy something appropriately close to those values.


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## MiniVanMan (Jun 28, 2005)

Have you accounted for baffle step, variations in impedance, and phase, break up nodes, and etc, etc, etc.

Here's a great tutorial to get you started. I guarantee if you follow the tutorial diligently, then you'll come up with values on your components that will be vastly different than what you posted.

http://www.rjbaudio.com/Audiofiles/FRDtools.html


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## ItalynStylion (May 3, 2008)

Thanks for the link Minivanman. Bookmarked!


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## mvw2 (Oct 2, 2005)

Except that I don't have full data on all the drivers.

I'll go through it and see if I hit any snags. I'm just not sure how I get things like phase or inductance if I don't actually have that data.

Update:
I don't have a Le plot for the tweeter, so there's not much I can do there other then say it's 6ohms everywhere.

The baffle diffraction thing is a mess. There really doesn't seem to be any logical location for any of the drivers. I'm not even sure what it's measuring. Is it external loading of the sound waves on the face? If it's external, wouldn't the room play a big roll in this? It seems more influential then anyone seems to care about it. I see minor driver placement changes to account for time alignment of the tweeter or something, but no one really does anything goofy with the enclosures. The baffle correction program shows vast swings in gain of 10dB or more. It doesn't really make sense.


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## ItalynStylion (May 3, 2008)

A 10db swing sounds like a lot. What frequencies did that cover?


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## MiniVanMan (Jun 28, 2005)

mvw2 said:


> Except that I don't have full data on all the drivers.
> 
> I'll go through it and see if I hit any snags. I'm just not sure how I get things like phase or inductance if I don't actually have that data.
> 
> ...


Welcome to loudspeaker design.


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## MiniVanMan (Jun 28, 2005)

Oh, and it does all make sense once you figure out what's actually happening. It's just not as simple as slapping some drivers on a flat piece of wood and adding some inductors and capacitors.

How the enclosure is built, the drivers are mounted, and placed, and taking into account all variations in frequency response and impedance are fundamental to good loudspeaker design. That's only basic. Wait till you start reading papers written by Sigfried Linkwitz, Earl Geddes, Vance Dickason, etc, etc. 

Not to deter you, but if you want to do it right, then understand that you know very little to actually make it happen.


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## mvw2 (Oct 2, 2005)

Sorry not 10dB, more like 1-2dB.

Is it just me or does the baffle compensator assume the lack of an enclosure? Is it just measuring the sound wave loading on the face? I ask because of the low frequency response roll off. Edge treatment also seems to play a huge roll, more so then actual driver placement.


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## MiniVanMan (Jun 28, 2005)

mvw2 said:


> Sorry not 10dB, more like 1-2dB.
> 
> Is it just me or does the baffle compensator assume the lack of an enclosure? Is it just measuring the sound wave loading on the face? I ask because of the low frequency response roll off. Edge treatment also seems to play a huge roll, more so then actual driver placement.


No, the baffle compensator just compensates for whatever frequency response you put in, whether it be an enclosure, IB, dipole, etc. 

Being a 3-way, you're only seeing a 1-2 db drop in the low end of your midbass. 2-ways are much more fun and the drop can be between 6-7 db from about 1khz sloping on down. 

Edge treatment is very important. The smoother the transition between the baffle to open space, the less induced artifacts you'll have in your baffle step response. 

Here's some homework for you. Follow the tutorial I linked and build a simple 2-way. Use my "Basic Guide to Crossover Part II tutorial as a guide of sorts. Pick a couple of drivers off of Zaph's site. Now, once you've done that, go to your local HiFi store and pick out a 2-way loudspeaker designed for a stand (not a bookshelf), then look at the sensitivity of the loudspeaker. If they claim between 86-90 db 1w/1m, AND a frequency response that extends down to 40-50 hz THEN ask them how they managed to defy the laws of physics.


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## Dr.Telepathy SQ (Nov 17, 2007)

MiniVanMan said:


> No, the baffle compensator just compensates for whatever frequency response you put in, whether it be an enclosure, IB, dipole, etc.
> 
> Being a 3-way, you're only seeing a 1-2 db drop in the low end of your midbass. 2-ways are much more fun and the drop can be between 6-7 db from about 1khz sloping on down.
> 
> ...


Was reading a loudspeaker cookbook on the plane Friday, and was wondering some of the same items you have listed Gary. My head started swimming.

Great post.


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## mvw2 (Oct 2, 2005)

MiniVanMan said:


> Edge treatment is very important. The smoother the transition between the baffle to open space, the less induced artifacts you'll have in your baffle step response.
> 
> If they claim between 86-90 db 1w/1m, AND a frequency response that extends down to 40-50 hz THEN ask them how they managed to defy the laws of physics.


The edge treatment thing is interesting.

Frequency response will depend on the driver. I guess I don't get the comment. Some woofer + ported enclosure? That should be able to do 40-50Hz depending on the woofer chosen.

The thing I don't get is that the driver is in the enclosure, so we don't have a rear wave issue. So, why does sensitivity roll off? Is this simply a matter of radiating energy? Sound radiates outwards in all directions. My assumption is that the baffle redirects a lot of of this, so the back hemisphere ends up getting pushed out with the front half. The enclosure face would then determine how low a frequency will remain only hemispherically radiated. Once the wavelength gets sufficiently long, it will start to radiate rearward again and sensitivity drops. I'm really just guessing here, just thinking about it in my head. It does make sense. However, the room then comes into play. It would seem appropriate to place a speaker right next to a wall to maintain low end response as long as we don't incur reflection problems I guess. However, most of the time, we seem to prefer to set the speakers away from the walls to delay reflections. It would almost seem ideal to actually recess speakers into the wall then would it not?


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## MiniVanMan (Jun 28, 2005)

Depends on your application. 

How wide of a baffle do you need to reproduce 100 hz with no diffraction? What about 50 hz? How wide would your wall need to be?

If you have a 12" deep loudspeaker, placed up against the wall, what frequency are you going to start experiencing diffraction? Then you have reflection back from the wall out of phase with the front of the baffle.

You can make your head hurt trying to make it all perfect. My point wasn't to dissuade you, but rather get you thinking about what you're actually trying to accomplish. So far, you're on the right track.

Zaph designs his loudspeakers to be placed 24" from the wall. He avoids muddying up his midrange by doing this which is one of his highest priorities. The frequency at which you start to get reflections is around 300-400 hz and below. 

There are complications with in wall designs as well. I'm not necessarily that well versed in them though, so I won't go into detail. I'll leave that to you.


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## mvw2 (Oct 2, 2005)

I'm curious what I can do with my build. My room is small, and my current setup has the 4 corner speakers, well, in the corners basically at the walls. I may be able to take advantage of this by building a triangle enclosure and sort of horn load those speakers. I don't have the space to pull them far from the wall, so I may have to incorporate the walls as part of the baffle. I'm not sure how to model that though. The center is just in front of and under the TV.

I really don't expect amazing thing. It's a cheap build in a ghetto rig type of install. The receiver cost $10, there are no ideal sitting positions, and I don't expect stellar results. I want to end up with a decently flat frequency response and a little broader response then what I currently have with my 4" + 3/4" setup. Right now I just overuse the 4" midrange and tend to get a bit of distortion from it under louder use during movies or playing music. I want to step a little bigger and fix that.


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## MiniVanMan (Jun 28, 2005)

Let's define your actual design goals now.

Do you want a floor standing loudspeaker, or do you want a bookshelf?

That SDS woofer is a very nice woofer for the money, and would work well in a nice 2-way bookshelf with the right tweeter. 

Save the money on the full range and go with possibly a tweeter like the Dayton DC28 with the truncated frame. With the mid and tweeter both having truncated frames, you can get away with a bit higher crossover point before lobing sets in. You could get away with a 3 khz crossover point, though your polar response will suffer. Sounds like a small room though, and that might be a worthy sacrifice. Keep the crossover point around 2.5 khz, and you'll be golden. 

http://www.parts-express.com/pdf/275-076.pdf

That would be a nice beginner project. You can guesstimate the amount of baffle step compensation you'll need depending on how close to the wall you'll be placing the speakers. Think in the realm of 1-5 db of compensation. Rarely do you ever compensate the full 6-7 db anyway. 

Make sure to recess the drivers into the baffle.

Other than that, with those two drivers, you could easily use the tutorial and come up with a suitable design.

If you have any questions feel free to PM me.

Keep it simple on your first go around. The above should be an excellent budget setup.


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## mvw2 (Oct 2, 2005)

I'm content with the 3-way setup. So far I have the crossover worked up in Speaker Workshop and have it set up pretty good using real part values from Parts Express. I'm basically at 70Hz to 20kHz +/- 2dB.

With the SDS woofer, the enclosure size will be 0.5 cu.ft. sealed for a final Q of 0.707. I'm looking at doing a thin floorstanding enclosure with the drivers sitting around 3' up from the floor. I can basically build a 8"x"5"x40" tower and mechanically get what I want.

I still need to fiddle with the baffle thing, but I think it is somewhat pointless in my case. I have 5 separate satellites and a large variety of listening positions. Each satellite will be in a different location and will be heard differently. I think the best I can do is simply start off with a speaker that outputs a relatively flat response. Because this is not an ideal room, I don't think I can look at this critically enough to care about baffle compensation.

I was playing with Speaker Workshop with the enclosure. For some reason it gives me a EQ bump around 100Hz for the correct enclosure size that would normally yield a flat response. I've used other software for enclosure design, so I don't really care much about Speaker Workshop for that.

The crossover design worked dandy. For some reason I needed to invert the polarity of the midrange driver. I thought a Linkwitz-Riley configuration always had matching phase.  Maybe it's a 3-way thing. I don't know.

I may look into shrinking it down to a 2-way setup. One issue I'm running into now is crossover cost. 2/3 of my cost right now is in crossover parts. Stepping to a 2-way would cut it in half. Maybe I'll just do the woofer plus the wideband. It'll still cover up to 12kHz or so, just simply becomes an off-axis thing. It's pretty easy to make a crossover for that +/- 1dB between 70Hz - 11kHz. I was mainly using the tweeter to aid on the top end and have no concerns about axis angle. It really isn't heavily needed though. In a 2-way configuration, I'm looking at a total of about $280 for hardware for a 5 speaker 2-way setup, $56 a speaker.


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## MiniVanMan (Jun 28, 2005)

Excellent!

My whole point of this exercise was to get you thinking a bit more critically, and understand where you'd need to compromise. It was also to get you to use a real crossover modeling program instead of a calculator. Makes a huge difference.

If you're doing a 12 db crossover, then yeah, you need to reverse the polarity.

Also, make sure your midbass and midrange (or fullrange) DO NOT share the same space.

Also, by building the full range it's own enclosure, you can cut the cost of another inductor and can just use a cap in series. Use the volume of the enclosure to shape the low end response, then steepen it with the cap. Very simple, and cost effective.


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## mvw2 (Oct 2, 2005)

that's a useful idea with using the enclosure as a crossover aid, but that gives me minimal control over the roll-off point. As well, I don't want to run into the issue of making the full range run into excursion problems. I may be sacrificing cleanliness and output capability with that kind of configuration. I'm doing about the same thing with the woofer, but I think this system is more limited by the 2" mid first. It's almost asking for trouble.


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