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Multi-Way Conventional loudspeakers with crossovers

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Old 19th August 2004, 10:42 AM   #21
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Hi Jennie
It seems that you are overcomplicating things. Remember the golden rule is to keep things simple.

Here's my suggestion:
A 2-way system - 6.5" midbass and 1" tweeter, preferably similar to a commercial kit.

Base your design on poly or paper cones, which won't require crossover gymnastics.

I recommend buying LspCAD which is one of the most user friendly software packages. Playing with it will teach you so much.

Base your design on published specs and Thiele small parameters - they won't be that far out. I would measure the impedance though and don't forget baffle-step compensation.

Use, say, 1st order lowpass on the woofer, 2nd order highpass on the tweeter, around 3kHz. Try to buy a woofer with the copper shorting rings (which results in a very flat impedance, hence simplifying the crossover further). Parts are minimal, cost is cheap and it's hard to go wrong.
Note: No microphone measurements have been made, which some people will frown upon, but I think is fine as a starting point.
They won't be perfect but they will sound great. Satisfaction is guaranteed.

Listen to these for a while, and then play around with the crossover, stuffing etc, for a few months, until you get a feel for how the sound is affected. Learn to take measurements with mics/soundcard/PC and correlate them with what you hear.. Gradually your ear will become educated and you will learn more and more about design, measurement. and construction.

By the way, in case you're wondering, this is how I started

Remember, if you get stuck, DIYAudio is only a mouse-click away.

David Gatti
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Old 19th August 2004, 11:34 AM   #22
Jennice is offline Jennice  Denmark
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Default Who's making things complicated here now...?

I'm not trying to complicate things.
It more seems like most are out to chare me (and others) off from doing this...

I certainly like to keep things simple, but I am now aware of the following main issues:

1)
choose XO-frequency high enough for the tweeter to live with decent power.

2)
Try to get the X-over at least 2 octaves over tweeter resonance with a 12dB filter.

3)
Beware of the baffle step

4)
I might want to time-align (or try to) the drivers. (In case I'm not using the correct terms, I'm referring to a different mounting depth of the drivers for tweeter and woofer(s), respectively.
Best bet is to try having the voice coils alligned.)

5)
Preferrably use woofers with copper ring to linearize impedance/frequency-dependence

6)
Respect, that x-overs are an art as much as a science. All types have compromises, but for starters, keep it fairly simple.

7) Better, linear drivers might save some resources in the x-over. (making the overall design simpler).

---

I ning on using 2 woofers in parallel, as I have a fairly large room, and want to be able to move some air. As I do not have use for them, I would consider 1 tweeter/1woofer combo waste of time in my case. (with all due respect).

I was not (until the recent post) aware of the idea of this copper ring. I've heard about it, but was not aware of the purpose. Can anyone suggest a decent woofer with this feature, possibly from Vifa, ScanSpeak, or Peerless (which I know where I can purchase.)?


Thanks so far -
Jennice
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Old 20th August 2004, 12:44 AM   #23
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You're on the right track.
The copper rings (short circuiting ring) improve the linearity of the motor as the voice-coil moves away from the centre of the magnetic gap. It's not essential but will definitely reduce distortion levels.
Examples are:
Peerless 850108 or 850122
Scanspeak 18w8545 (expensive)
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Old 20th August 2004, 03:00 AM   #24
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Quote:
Originally posted by Jennice
... It seemed that people tried to tell me my ideas are deemed to fail.
More like outlining the pitfalls of getting a world class multi-way speaker to work.


Quote:
Originally posted by dvdwmth
Full range driver are, IMHO, an excellent way to jump in without getting overwhelmed with complex crossover issues. They're cheap (well some are anyway), well documented, and sound good. You can always add more drivers to fill out the extreme ends if you want to experiment with crossovers.
Having started out building multiways, my designs have evolved heavily towards "mostly" full range -- it allows me to pretty much avoid crossovers, and the ones i do need are pushed to the ends where you can be less picky. Find a FR you can live with. There are few that don't need help at one end or the other, but even without help you can live with them because they do the critical midrange really well ... add a super tweeter at the top if you are missing some air -- usually a single cap will do for an XO (w maybe an Lpad to sdjust levels)... then add a pair of active woofer/subwoofers -- the place that benefits the most from an active woofer is the midrange.

Vifa has some nice full ranges (they call them midranges for some reason), and the Fostex FE103 has to be one of the best bang for the buck drivers made (the 40-1197 mentioned is a budget version of this driver). For more money there is the Vifa made Jordan JX92. The Visaton B200 is also a stand-out (it doesn't really need a lot of help at either end and i could happily live with these -- if i could fit the open baffles in my room). In Europe there are some others purported to be very good that i haven't heard, Ciare, Visaton B20 (?), even some Russian sleepers.

That said, a hard to beat "convential system" is 1 or 2 Vifa P13s XOed with a single cap to an appropriate tweeter.

dave
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Old 20th August 2004, 03:07 AM   #25
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Default Re: Who's making things complicated here now...?

Quote:
Originally posted by Jennice
3)
Beware of the baffle step....
using 2 woofers in parallel
if 2 woofers are used in a bipole (an opportunity to load them push-push, to gain the advantages of that) you don't have baffle-step to worry about. if your room can't live with the bipole, the back driver can be rolled off in a 2.5 way config... getting the choke on the back driver just right is much less critical here since the roll-off is all hapening in the shadow of the box.

Quote:
I was not (until the recent post) aware of the idea of this copper ring. I've heard about it, but was not aware of the purpose. Can anyone suggest a decent woofer with this feature, possibly from Vifa, ScanSpeak, or Peerless (which I know where I can purchase.)?
Drivers with motors like this are usually the more expensive ones, and IIRC your budget, probably lie on the wrong side of your max dollars.

dave
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Old 20th August 2004, 05:29 AM   #26
Jennice is offline Jennice  Denmark
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Default Re: Re: Who's making things complicated here now...?

Quote:
Originally posted by planet10


if 2 woofers are used in a bipole (an opportunity to load them push-push, to gain the advantages of that) you don't have baffle-step to worry about. if your room can't live with the bipole, the back driver can be rolled off in a 2.5 way config... getting the choke on the back driver just right is much less critical here since the roll-off is all hapening in the shadow of the box.

dave
Please confirm if I understand this right (when looking on google for bipole, it asked if I wanted to look for dipole, which again leads to surrpond speakers):

A dipole or bipole is a speaker enclosure, where an extra woofer is placed at the rear of the enclosure, in electrical phase with the front woofer. This should then compensate for the loss due to the baffle step. Correct?

As I see it, a potential problem with this back-facing woofer, is that it might cause accoustic problems if the speaker is placed too close to a wall, as this will then over-compensate for the baffle step losses (having both a reflecting wall, and the added woofer). Correct?

Jennice
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Old 20th August 2004, 06:22 AM   #27
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Default Re: Re: Re: Who's making things complicated here now...?

Quote:
Originally posted by Jennice
an extra woofer is placed at the rear of the enclosure, in electrical phase with the front woofer. This should then compensate for the loss due to the baffle step. Correct?
Yes

Quote:
As I see it, a potential problem with this back-facing woofer, is that it might cause accoustic problems if the speaker is placed too close to a wall, as this will then over-compensate for the baffle step losses (having both a reflecting wall, and the added woofer). Correct?
Yes ...

but i don't know many speakers that like to be crowded into the wall... you did say you had a fairly big room?

dave
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Old 20th August 2004, 06:29 AM   #28
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Some bipole/push-push links....

http://p10hifi.net/tlinespeakers/TLS...s-TL-pipes.jpg
http://www.t-linespeakers.org/FALL/bipolar/index.html
http://www.t-linespeakers.org/FALL/push-push.html
http://www.t-linespeakers.org/FALL/dipole.html
http://www.t-linespeakers.org/FALL/rtls/tline.html

dave
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Old 20th August 2004, 06:58 AM   #29
Jay is offline Jay  Indonesia
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Quote:

1) choose XO-frequency high enough for the tweeter to live with decent power.
Ok, tweeters prefer high cross points. But then the woofer must be crossed at high point too. Woofers usually have problems in the higher frequency regions.

I think I prefer to hear tweeter problem than woofer problem in x-over point. By bringing the tweeter to the low region we may be able to compensate the problem with high order crossover, padding resistor, or lower power handling capacity, and get the best out of the woofer. (But every drivers have their own properties...)

If XT25 is used, crossing too high may not be a good idea. I don't think I want an XT25 if smooth higher ends is what I'm looking for.
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Old 20th August 2004, 07:07 AM   #30
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Quote:
Originally posted by Jay
tweeters prefer high cross points. But then the woofer must be crossed at high point too. Woofers usually have problems in the higher frequency regions.
If you use a full-range not a problem.

dave
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