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Multi-Way Conventional loudspeakers with crossovers

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Old 19th December 2012, 03:13 AM   #341
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Hi Greg, I am still in the early stages of learning how to measure. My plans at the moment are to just see if one design or another lends itself to producing better results, as you can see from the two graphs even with the lumpy looking response the mid bass improved when put on the baffle whereas the mid and tweeter not so much.

I have been using the 12MUs anywhere between about 1300Hz – 1600Hz and 3500Hz, you think I still need to go even lower to around 500Hz? That wouldn’t leave a great deal for the mid woofers then would it?

Yep had already looked at a modification of the top end to something more like this.

Want to experiment with measuring in different spots and distances before I start to chop.
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File Type: jpg IMAG1190-2.jpg (172.3 KB, 129 views)

Last edited by Silent Screamer; 19th December 2012 at 03:18 AM.
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Old 19th December 2012, 03:28 AM   #342
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Well, 1.5-3.5Khz is not a mid. It's more like a filler driver for a two way. Leave just the "impact and weight" region to the midbass and get all of the primary vocal region in the mids. You will probably have to EQ their low end response to bring it up as well, but ought to be a much more accurate way to go.

Greg
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Old 19th December 2012, 03:38 AM   #343
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ok I will give that a go, I was crossing over the mid woofer much higher before 2000Hz+ and letting the mid woofer do the bulk of the grunt work. But I will drop the mid right down and let it pick up the bulk of the vocal work and see how that sounds.
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Old 19th December 2012, 04:01 AM   #344
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mid crossover point is also a trade off for power handling too isn't it?

I haven't read this article in a while but Rod Elliot has some discussion on crossover point selection in his bi-amping article. BiAmp (Bi-Amplification - Not Quite Magic, But Close) - Part 2
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Old 19th December 2012, 05:38 AM   #345
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Quote:
Originally Posted by hochopeper View Post
mid crossover point is also a trade off for power handling too isn't it?

I haven't read this article in a while but Rod Elliot has some discussion on crossover point selection in his bi-amping article. BiAmp (Bi-Amplification - Not Quite Magic, But Close) - Part 2
Well, sure. Rod's site has lots of good info, but even he says that design is all about compromises. In section 2.0 just above where you linked, he mentions his preference for keeping the 300-3000Hz range intact and not using a crossover there. With Silent running two mids in parallel, I anticipate no problem running as low as 300Hz. Will it sound best? Who knows, but I'd start there and work up if necessary.
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Old 19th December 2012, 11:05 AM   #346
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I set up two copies of the software one with the old crossover and one with the new. A very different sould but crossing over low and high does make is sound much crisper.

I also notice that I am not maintaining a high enough SNR. Its ok on the tweeter but by the time I get to the mid woofer it is too low cauasing all sorts of lumpy graphs.

3 out of the 4 were in the green for these measurements with only the woofer below acceptable. Notice how much more level it looks.

Also tweeked the crossover to start a bit flatter.
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File Type: jpg Raw - Individual Measurements 3-1.jpg (337.7 KB, 92 views)
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Old 19th December 2012, 08:28 PM   #347
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I'm using the same software. And found out that instead of using smoothing. Try "Multiwin". I shows 3 red lines. One at 0 mm seconds, one to adjust gating and the third you just leave alle the way out where it is.
So - number two red line is the one to focus on. The first pulse, is when the first direct sound hits the microphone. So the trick is to find out how far the sound has to travel from the speakerunit - down to the floor, and up to the microphone(this is your first reflection). and if you find this distance in mm-seconds, and place the second red line at this point. Then you are actually canceling out the "room"

The 300hz dip. Might just be the room acoustics. Measuring low in frequency is hard. Because you have to remove reflecting surfaces. putting the speaker on a tabel, helps a little. You can also try to lay the speaker on its back and hang the microphone from above. The lower the frequency, the longer the waves. Therefore you have to move reflecting surfaces farther away
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Old 19th December 2012, 10:12 PM   #348
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There's too much info shown on those measurement plots. It is very difficult to tell what each line represents. Can you download Room Eq Wizard and use that with your mic and soundcard? It's very simple to use and very powerful as well. Or at least find a way to only show a non-gated nearfield or a lightly gated 1 meter response of the whole system rather than driver by driver? There's got to be a choice in the software to turn off some of the traces.

Greg
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Old 19th December 2012, 10:12 PM   #349
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Thanks Tordenguden, at the moment I am just trying to get the get the basic speaker design as good as I can get it without any correction. I am using smooth simply to get a line that can be viewed (the non-smooth is impossible to view properly) not trying to get it as good as I can.
By using just the smooth I can do a much more “fair” comparison of each reading, as using MultiWin does alter each curve quite differently based on the amount of time spent refining it.

Robert has already given me a few clues on how to use the MultiWin, and I have experimented with varying degrees of success. You mention that you leave the first line at the far left (0ms) and move the second red line to the floor bounce (start of first bump). I was under the impression that you put the first red line at the point of floor bounce and the second and third red lines to the right of that. I might give what you’re doing a go and see how that goes.

I have been giving it some thought as to how to measure, and really are we just kidding ourselves if we measure to get optimal results when we would get a different result from our listening position. Which has led me to think perhaps the truest way of measuring the speakers is to place the mic at ear height in the seated position, as that is where your ears are going to be placed while listening to the speakers. Should we really be adjusting the speakers to get the best results there?
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Old 19th December 2012, 10:18 PM   #350
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No, do not begin at the listening position. There is to much room interaction to see clearly the native response of the system. Or you'd have to gate it so much that all low frequency resolution will be lost. Start nearfield, get it well balanced close to flat or with a gradual downward tilt towards the highs and THEN see what you're getting at the listening position.
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