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Multi-Way Conventional loudspeakers with crossovers

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Old 29th June 2012, 04:16 PM   #11
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Been tweaking the filters the last couple of months, tried different slopes and frequencies. EQ-ing the drivers flat before filtering, time alignment, and a lot of other stuff. I really like the DSP in this sytem now The "sientific" aproach rather then trusting my ears. Only when I was finished measuring and setting filters I really took the time to listen.

I ended up with a LR8 @ 3.1KHz, a notch on the tweeter @16.5KHz (Q2.9, G-2.2dB) a notch on the woofers @ 5KHz (Q2.9, G-3.0dB)and a baffle step compensation of 5.5dB.
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Old 29th June 2012, 05:13 PM   #12
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Because I have a lot of freedom in EQ-ing these speakers with the DSP I wanted to know if high order filters are really audiable. So I did some googling and came across this thesis paper. http://lib.tkk.fi/Dipl/2008/urn011933.pdf Excellent piece of work.
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Old 29th June 2012, 10:14 PM   #13
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nice build! I briefly looked at the hypex kits, the modules your using seem like a nice simple entry into active filtering amplification. I might have to have a look again, in more detail.
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Old 1st July 2012, 05:00 AM   #14
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Quote:
Originally Posted by Mark.Clappers View Post
The drivers are 2 Seas W15LY001 midwoofers and a Fountek NeoCD2.0 ribbon tweeter in a MTM. The crossover is LR8 @ 3.5KHz time aligned..
Hi Mark,

Excellent work with top level drivers and the latest amp_DSP technology.

You could contribute to the great "ribbon tweeters in MTM" design debate! Do you plan any off-axis measurements?

1) side one: only very short ribbons crossed at low'ish frequencies to very small diameter midranges can meet the M-T and M-M spacing math for good lobing control.
2) side two: the ribbon M-T spacing should not be measured from the center of the ribbon, but rather near the edges. Adequate lobing control can be achieved with long'ish ribbons and small diameter midranges.

The math behind reducing lobing in a MTM topology requires very close M-M and M-T spacing. Crossover_wavelength/4 is the ideal for M-T spacing and Crossover_wavelength/2 is the limit for M-T and M-M spacing.

If you believe the math, even for ribbon tweeters, then only very short ribbons like the RAAL 70-20, crossed at low'ish frequencies like 1.4-1.6Khz to small 4"-5" midbass can maintain adequate lobing control.


One decent reference:
Vertically Symmetric Two-Way Loudspeaker Arrays Reconsidered
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Old 1st July 2012, 11:07 AM   #15
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Hi LineSource,

Thank you!

Yes I know vertical lobing is a problem with such a setup. Did a lot of sims with WinISD, Boxsim, Edge, Xdir and AADA before starting this build. In the end I just wanted to try a big ribbon to see what they can do with good amps and DSP filtering.

With these drivers you need a 3KHz minimum XO to avoid distorsion problems with the tweeter. (hence the Nextel woofers in stead of Magnesium) Which of course translates to vertical lobing problems and comb filtering effects. I am playing with the idea of a NTM type crossover to push the XO frequency a bit lower.

In my setup I don't really care about the vertical lobing because I just sit down in 1 place to listen. Heck I even use a modded DEQ2496 for some room correction... attached an early Boxsim sim (no DSP data included), it gives a rough idea of the polar response and comb filtering effects.

Edit: because of the vertical response pattern of this tweeter you will always have lobing, no matter what type of driver arrangement you build!
Attached Images
File Type: jpg vertical horizontal response.JPG (266.7 KB, 315 views)
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Last edited by Mark.Clappers; 1st July 2012 at 11:24 AM.
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Old 1st July 2012, 11:14 AM   #16
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And the response plots of the planned system when completely done (active 3 way with 2X Dayton Audio RSS265HF-4 per side added)
Attached Images
File Type: jpg 2pi response.JPG (199.1 KB, 308 views)
File Type: jpg vertical horizontal response full.JPG (268.4 KB, 301 views)
File Type: jpg Filter response.JPG (192.1 KB, 288 views)
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Last edited by Mark.Clappers; 1st July 2012 at 11:25 AM.
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Old 1st July 2012, 12:53 PM   #17
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And a first sim of a NTM like type XO, been playing around with it today and it looks like I can push the XO frequency down to ~ 2.4KHz. Interesting!
Attached Images
File Type: jpg XO NTM.JPG (197.7 KB, 280 views)
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Old 1st July 2012, 12:58 PM   #18
AllenB is offline AllenB  Australia
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I like the overall response in the 200-600Hz region for reducing floor and ceiling reflections down where they're harder to deal with.

But looking at the horizontal response I notice also that between 200-2k, the zero degree axis is higher than the overall response. So this might benefit from the right toe-in.
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Old 17th July 2012, 07:07 PM   #19
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Ended up pushing the XO frequency between the mid and tweeter a little higher. It's now at 2.7KHz. The tweeter likes this a lot better, distorsion wise.

The 4 notches stayed, 1 on the woofer to compensate for the rising response and 1 one the tweeter to tame a resonance around 1200Hz. The other 2 notches on the tweeter are there to flatten the response up to 22KHz.

The XO itself is a LR8, and the baffle step compensation is 5.5dB. The (sub)woofer section is still a sim only but it looks like that when I take into account the room gain I get a frequency response that covers ~ 20Hz - 22KHz.
Attached Images
File Type: jpg Trinium filter 17-07-2012.JPG (214.0 KB, 40 views)
File Type: jpg Trinium filter response 17-07-2012.JPG (207.0 KB, 40 views)
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Last edited by Mark.Clappers; 17th July 2012 at 07:26 PM.
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