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Multi-Way Conventional loudspeakers with crossovers

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Old 9th January 2005, 09:27 PM   #1
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Unhappy corssover first time builder.

Hi, i was just wondering how easy it is to build a crossover curcuit? It is a two way x-over with a 3000Hz crossover point, with 12db/octave and has to be able to handle 80watts o'power. Does anyone have a design i could maybe follow and show me in the right direction as to what parts to get. Also can it be done cheaply?


I have never made a circuit yet but intend to learn how, is a x-over curcuit a good place to start?
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Old 9th January 2005, 11:47 PM   #2
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Crossover calculator

Would be a good place to start. You can hot glue the components down to a piece of thin material and solder 'em up. No brainer.

20 ga. coils would be plenty and most of the audio caps should be rated in the range of 200VDC anyway so that's not a problem. They will be "non-polarized".
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Old 10th January 2005, 12:10 AM   #3
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the ccokbook formula crossovers like the link above will work reasonably well only if your drivers have flat response well outside their respectice passbands. You also need to compensate for the sensitivity differences of the drivers (usually the tweeter is more sensitive) There should be an lpad calculator on the site linked to above.

If you want to do it "right" you should measure the response and impedance of the drivers in the final cabinet and then design the crossover to match. Speakerworkshop is a powerful tool, and it's free. The downside is that it takes some work to understand and you'll need to make a jig and measurement mike. Your results will be much better this way with most driver combinations. Nt to say that you won't get acceptable results with cookbook crossovers, if you choose your drivers carefully.
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Old 10th January 2005, 01:08 PM   #4
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This is the low end i will be using:

http://www.bkelec.com/Hi-Fi/Alcone%2065he.htm#525he

High end:

http://www.bkelec.com/Hi-Fi/Alcone%20ac1hat.htm

Am i right in saying the x-over frequency should be 3000hz?

Click the image to open in full size.

Sorry if this is a bit of a "noob" question but how do i make this circuit up so that there is just the one input? Also i downloaded speakerworkshop and yes it is hard to understand but i'll try and get the hang of it somehow.
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Old 10th January 2005, 01:35 PM   #5
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The tweeter will have a lot more sound coming out of it than the woofer. That's because of it's greater sensitivity ~ 92 Vs. 87. SO much so, that it would be a problem. Strongly consider a MTM configuration by adding a second 5".

The tweeter has to be attenuated with either a fixed or variable L-pad. Basically a small resistive crcuit in series an parallel with the tweeter.

l-pad

These are also available in a variable style.



l-pad
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Old 10th January 2005, 02:00 PM   #6
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And yes, the "+" and the "-" are connected together at the terminals. They can also be connected at the crossover following the diagram you have posted.
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Old 10th January 2005, 07:34 PM   #7
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I only want to have to buy a bass/mid driver and tweeter as i already have a pritty decent sub and i am building the speakers on a budget. What top end frequency would be acceptable for a bass/mid range driver? Also what is attenuation?
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Old 11th January 2005, 08:47 AM   #8
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Quote:
Originally posted by Dannyball
Also what is attenuation?
(relative to audio) to lessen in output of the speaker.

attenuate volume = lower/lessen volume
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Old 11th January 2005, 03:16 PM   #9
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Thanks

What top end frequency would be acceptable for a bass/mid range driver if i am going to be using a tweeter as well?

What should be the atenuation i should set the tweeter to?
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Old 11th January 2005, 03:36 PM   #10
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Quote:
Originally posted by Dannyball
Thanks

What top end frequency would be acceptable for a bass/mid range driver if i am going to be using a tweeter as well?
rule of thumb is at least one octave of overlap, preferably two if you want to use cookbook crossovers. eg. - crossover at 3K, woofer should be smooth to at least 6 K if not 12, tweeter should be smooth to 1500 if not 750. Look for drivers that meet this requirement and you'll understand why the measure and design a crossover to match method works so much better

Quote:

What should be the atenuation i should set the tweeter to?
Whatever it needs to be to match levels. If your woofer is 89 db/2.83V and the tweeter is 95 you'll need to pad the tweeter down roughly 6 db. Roughly because there will be some loss in the crossover network and 2.83 volts at the input terminals will be something less at the speaker terminals where it matters. Usually the woofer section will lose more and you'll have to attenuate a little more than the efficiency difference might suggest. The best way to determine the attenuation required is to measure.

The biggest thing that you can do to help out your standard crossover after careful driver selection is add a zoebel (R-C across the woofer) to control the impdance rise of the woofer.
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