Beginner information on crossovers - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #1 of 9 Old 03-13-08, 06:54 AM
coffee412
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Beginner information on crossovers

Im really new here and have been searching around for online resources to explain crossovers and how they function. I figure that there might be others like me that want to know. I realize from reading alot of the post here that Iam in a crowd of EXTREMELY smart people however, I just wanted to post this link for anyone learning like me. If its out of place here I appologize.


http://www.termpro.com/articles/xover2.html

I found it a good source for getting the basics down for crossovers.

Thanks from a newbie,

coffee
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post #2 of 9 Old 03-13-08, 07:35 AM
thomas2717
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Re: Beginner information on crossovers

Thank You ^_^
post #3 of 9 Old 03-13-08, 07:44 AM
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Re: Beginner information on crossovers

http://www.bcae1.com/xovrslop.htm

www.lalena.com has some good stuff (calculators)

http://sound.westhost.com/lr-passive.htm

www.zaphaudio.com has some stuff (although most of it is driver testing)

All have some good information. The two most important things to know about crossover design are: 1) one size does not fit all (i.e. pre-made crossovers) 2) you will have to test and tweak to get the design right -- even if you use a good simulator and optimizer program first.

So patience and research will get you a long way. , my current speaker project is almost a year running now. I really want to get it right
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post #4 of 9 Old 03-13-08, 07:53 AM
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Re: Beginner information on crossovers

Thank you very much for your reply and links. Its always rough to be new in the neighborhood and learning almost from scratch. Im looking to build 2 main HT 3 way floor speakers, 1 center speaker, 2 smaller rear speakers for my HT project in the basement.

Im going to go to the local book stores today and check and see if I cannot find the "Loudspeaker Design Cookbook". If not I will grab it online. Should be a very valuable read for any beginner.

coffee
post #5 of 9 Old 03-13-08, 08:04 AM
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Re: Beginner information on crossovers

If you can't find it online, also check PartsExpress or Madisound -- they both carry it. It's a boring read, but lots of good info there.
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post #6 of 9 Old 03-13-08, 04:42 PM
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Re: Beginner information on crossovers

The link you posted, although good for beginners, leaves out several very important points you need to consider in crossover design.

First, it assumes that all the drivers are equally efficient. That will almost never be the case. Not only must you direct the correct range of frequencies to each driver, you must adjust the level sent to each driver so they all are heard at the same sound pressure level. Tweeters are almost always more efficient than midrange, and midrange more efficient than woofers. If you do not add padding resistors to adjust the relative levels of the tweeter and midrange drivers, the resulting speaker will sound very shrill.

Next, you must be concerned with the "phase" of the signal sent to a driver. The goal would be to have all the driver cones moving in the same direction at the same time. .. this is especially important at the crossover frequencies as both drivers will be active. (both the driver above and below the crossover frequency are active when sent a sound anywhere near the crossover frequency. ) Remember, you are basically trying to create a given SPL ("Sound PRESSURE Level"). You cannot pressurize the air in the room very well if the cones are working against each other as one moves inward when the other moves outward.

The driver "phase" will depend upon the number of "poles" in each crossover section. If you get this right, the frequency response will be smooth across the crossover points. If you get it backwards, there will be a deep notch in the frequency response since one cone will be moving forward while the other moving backward. The net effect will be very little pressurization of the air in the room.

Last, the efficiency of the woofer will change at a frequency dependent upon the width of the front baffle of the speaker. A compensation network can be added to make this efficiency difference have less impact on the resulting sound. This is called "Baffle Step Compensation"

If you get through all this, you still need to deal with on-axis response vs off-axis, and impedance presented to the amplifier. An impedance compensation network might be needed to even out the resulting response.

All this means that there is almost no chance that any pre-built crossover will work with a random set of drivers and provide the best sound from those drivers. Yes, they'll make sound, but not great sound, and in the worst case, horrible sound.

You can really appreciate the work and effort needed to create a good crossover for a set of drivers. It is a really complicated task. Done right, good drivers will sound wonderful. Done wrong, even excellent drivers will sound terrible.

Joe L.
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post #7 of 9 Old 03-14-08, 05:20 AM
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Re: Beginner information on crossovers

Thank you, All is well noted. I am learning more and more all the time.


Thanks!

coffee
post #8 of 9 Old 03-14-08, 10:38 AM
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Re: Beginner information on crossovers

Just to complicate your learning curve, you can take apart almost any inexpensive two-way speaker and I'd bet 90% or possibly more have only a single capacitor in series with their tweeter and the "midrange" fed with the full signal. That's it, the whole crossover is one component.

Those speakers were designed with "cost" as the primary objective, not sound quality.
The manufacturer has the advantage to at least match the sensitivity of the two drivers. (maybe)

The crossovers described in the initial link are probably an order of magnitude better than the single capacitor in series with the tweeter. And a correctly designed crossover is probably not much more complicated than those described in the link.... but often way better engineered.

Keep reading and learning... there are a ton of people with knowledge to share... many really know their stuff.
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post #9 of 9 Old 03-30-09, 04:34 PM
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Re: Beginner information on crossovers

I suggest you start with the stereo pair. It took me six months to dial in my speakers with an active digital crossover but the sound is better than my previous 40k sound system. It just takes a while to get right. It also takes a long time to do all the research. I settled on the active crossover after doing many searches and seeing what others had to say about them. Almost none of the experiences with active are negative as opposed to passive. From personal experience passive is not even in the same class as active. You would have to spend 100k (retail) on passive to get the sound possible for less than 5k active (assuming you do all the work and 5k is spent on parts). Just my 2cents worth.
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