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Multi-Way Conventional loudspeakers with crossovers

role of crossover
role of crossover
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Old 24th March 2005, 05:23 PM   #1
aarono is offline aarono  Canada
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Join Date: Mar 2005
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Default role of crossover

Hi guys.
absolutley LOVING this forum!!!!
still a newbie to diy speakers, but I think i will attempt some rear surrounds as a starter project.

I have a couple questions:

do places like solen.com typically sell the binding posts and plastic mounts for the posts?

again, would solen sell the "tube" that provides porting/venting or what is typically used, just a round hole in the wood?

and lastly, as the thread title suggests... I know that a crossover provides some type of high or low pass filtering. but why woudl one do this? is it just when you have more then 1 driver in a cabinet and you want to separate certain frequencies from the drivers?
are crossovers absolutely necessary and how do you go about incorportaing them? how do you know your capacitor values?(i assume all you reall need in s crossover is a few caps)
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Old 24th March 2005, 07:48 PM   #2
jpg is offline jpg  Germany
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Location: Germany
Hi aarono,

first of all, I strongly recommend that you build an existing, proven design as your first project (there are hundreds of them, if not more - name your demands and people will probably shower you with recommendations).


Quote:
I know that a crossover provides some type of high or low pass filtering.
That's correct, but crossovers can do more than that.


Quote:
but why woudl one do this? is it just when you have more then 1 driver in a cabinet and you want to separate certain frequencies from the drivers?
That's correct, but crossovers can do more than that and thus are often used with a single driver, too.


Quote:
are crossovers absolutely necessary
Depends (on your understanding of high fidelity music reproduction and the electrical and mechanical capabilities of your driver). In general, the answer to your question is a clear yes. There are only very few (if any) full range drivers that will play to their potential without any sort of electrical filtering. If you intend to use more than one driver per speaker, it's practically impossible to get along without a crossover, anyway.


Quote:
I assume all you reall need in s crossover is a few caps)
That's incorrect. Actually, it's true only for the simplest of all electrical filters, the first order (6dB/oct) high pass filter which is indeed one single bi-polar capacitor. For very few full range speakers or certain subwoofer designs that's all you'll need, but in case of a two way speaker system, you'll almost always want to add at least a first order low pass which is an inductivity (wire-wound coil). But it's in very rare cases only that you'll get along with only two parts per crossover.

Resistors are also very common in filters.

The above is applicable to passive crossovers which is what you're most likely to want to deal with. Active crossovers are a different kind of thing.


Quote:
how do you know your capacitor values?
Common sense, experience, but mainly calculation, simulation, measurements.


Quote:
and how do you go about incorportaing (the crossover)?
Passive crossovers belong between the power amplifier and the speaker.


There's a whole lot more to crossover design than even the most helpful person could ever cover in a single thread in an online forum. I recommend that you use Google to find ressources that explain at least the basics of the topic.

Whether a text book (by Dickason or D'Appolito, for instance) is the right thing for you depends on how deep you're interested in diving into the subject. If you intend to build just one pair of speakers and then move on to other fields of interest, there's probably no point in investing lots of time and effort in learning about (electro/psycho)acoustics, (electro)mechanics, (electric/acoustic/mechanic) filter theory, measurement techniques and stuff like that, since, in general, I don't see a point in trying to design a speaker system on ones own instead of building a proven design, unless having profound knowledge on the whole not so trivial subject or unless being able to enjoy spending time and money for random trial-and-error.

On the other hand, if your expectations aren't high and your materials inexpensive, you might well be able, with some help from a forum like this, to get acceptable results. (I'm adding this remark because I'm aware that many beginners already have drivers at their hands with which they don't know what to do.)

jpg
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Old 24th March 2005, 08:02 PM   #3
audio-kraut is offline audio-kraut  Canada
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Location: 12km off the alaska highway in northern BC
Hi,
The previous posting explains it well enough for the start.
Solen - where I source my drivers and x over parts from - also have designs and diagrams on their webpages for some proven diy speakers. Check it out.
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