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Multi-Way Conventional loudspeakers with crossovers

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Old 2nd February 2013, 10:40 AM   #21
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Just put the parameters of the mid driver into winisd and model it with sealed of various sizes and see what you get. If you are going to cross it over high (say 500Hz) then provided you aren't getting peaking in that range you can make the volume quite small, and you should get better power handling to boot The 5L was just an example (and is probably bigger than most ever would be).

Graph shows my SB 4" driver modeled in the "ideal" 1.5L volume and a smaller 0.5L volume. You can see the effect of the smaller volume, but if you were crossing at 500 Hz it wouldn't be much of an issue.

The power handling is where it gets interesting. with 1.5L 5W is about the maximum without exceeding xmax. With 0.5L you can put 20W into it without exceeding xmax.

Also take into account that any enclosure you add for the mid is taking away volume in your 45L main cabinet

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Old 2nd February 2013, 10:48 AM   #22
tvrgeek is offline tvrgeek  United States
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A sealed mid compartment's job is isolation if you are crossing over several octaves higher than the resonance. (usually) Larger does not hurt performance, but it is a waste of space. So, if yo have a 4 inch mid and the T/S parameters say it has a resonance say 80, and the model says it could be tuned to an F3 of 110 Hz in 2 L, but you are going to cross it over at 500, then half a liter or 10 liters would make no difference. Go ahead. Model it. Add the filter WinISD lets you.

Yes those sealed back mid's from the 60's were crossed over pretty high. They were cheap. Yes many speakers did not isolate the midrange. They were cheap.

This not a complicated issue. Isolate your mid in a well stuffed chamber so you reduce any reflections back through the cone. That's about all there is to it.
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Old 2nd February 2013, 10:50 AM   #23
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Formulas give the result of the variables plugged in. The designer decides minimums and maximums.
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Old 3rd February 2013, 05:56 AM   #24
Stevenn is offline Stevenn  Australia
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With no disrespect intended to older Diyaudio members, would they really have cross overs designed for closed back mids in early 1980's?

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Old 3rd February 2013, 09:46 AM   #25
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Quote:
Originally Posted by Stevenn View Post
With no disrespect intended to older Diyaudio members, would they really have cross overs designed for closed back mids in early 1980's?

Cheers
Sure, it's usually a single cap in series, same as a closed back cone tweeter, at least two octaves above resonance, which ( I imagine ) is why all the component XOs from Tandy/RadioShack used 800and 1500Hz as the XO point
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Old 4th February 2013, 06:23 AM   #26
Stevenn is offline Stevenn  Australia
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Thanks
Definitely only two capacitors in cabinet
Looks likes I might have to look at the crossovers sooner rather than later then if they are crossing over at 800Hz rather than 500 which our WinISD design is based around.
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Old 5th February 2013, 05:35 AM   #27
Stevenn is offline Stevenn  Australia
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Proposing to use 8" SB23 as recommended by Wintermute with 4" Peerless 830992 as midwoofer which I already have with Peerless 1 " tweeter 812978 in my 40 litre box with 4 litres for mid woofer.
Assuming (!) 500-5000 Hz are best crossovers asper previous posts, I have struck a problem in that both WES Components and Speakerbits do not have 500HZ-5000HZ crossovers. Anyone know a source in Australia?

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Old 5th February 2013, 05:52 AM   #28
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Stevenn you are going to have to design and built the XO your self if you want to use 4 liters for the mid, it will more than likely need a second order.
That little peerless woofer could cross over much lower than 500 but every time you go down in frequency costs increase because the coils have a lot of copper in them.
May I suggest you download J.Bagbys program ( free ) and play with it.

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Old 5th February 2013, 08:46 AM   #29
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I'm with Moondog. Having cut my teeth on pre-built crossovers, it is not the way to go if you want real real quality. You might get lucky and have something that works ok, but chances are it won't.

At a bare minimum I would recommend looking at the manufacturers specs and seeing what the impedance is at your selected crossover frequencies, and working from there.

Ideally if you can get real impedance measurements you will be even further in front. It is not that hard if you have a sound card with line in, you can do it with a single resistor and a 3.5mm stereo cable cut in half.

Even better is if you have acoustic measurements of the drivers on the baffle, but even manufacturers curves traced with spltrace will give you a big head start.

If you don't feel like making any measurements, at least have a read of Allen's excellent sticky in this forum.

Also don't worry too much about whether 500 and 5000 are best. It will depend on the individual drivers. You need to look at what your 4" mid is doing up that high (it may well have breakup in this region. You might be better off crossing somewhere between 3 and 4K. I think a four inch driver will be well and truly beaming (becoming very directional) by 5K as well, which you don't necessarily want.

There are no hard and fast rules, the important thing is the end result, not necessarily how you got there

I'm assuming that moondogs reference was to Jeff's PCD (passive crossover designer) It's a great spreadsheet that really helps you get your head around how crossovers work and how various changes affect the result available here --> http://audio.claub.net/software/jbabgy/jbagby.html

Tony
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Old 5th February 2013, 09:40 AM   #30
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Yeah. Sorry I couldn't find the link at the time. I use his box program too.
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