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Multi-Way Conventional loudspeakers with crossovers

Modular active 3 way - work in progress
Modular active 3 way - work in progress
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Old 2nd September 2018, 07:42 PM   #1
DonVK is offline DonVK  Canada
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Default Modular active 3 way - work in progress

I've been wanting to try this for a while. I've been building the knowledge (generous help from DIYaudio members) and acquiring the pieces for it over the last year.

I call this a "work in progress" because I'll be changing drivers and configurations until I'm happy with it. A modular design should accomodate this. So no pretty packaging for now.

--------------------------------------------------------

- Donor boxes and the initial drivers : silk purse from sows ear contest?
- Active analog 3 way XO : Budget active 3 way crossover - buy, eval, mod
- Active analog subwoofer adj bandpass : Budget active subwoofer lowpass, buy, eval, mod
- Class D amps : OmniDirectional - work in progress
- RPI3B + Piano DAC : Raspberry Pi with Piano2.1 DAC DSP and Volumio2

Last edited by DonVK; 3rd September 2018 at 02:05 PM. Reason: typo
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Old 2nd September 2018, 07:53 PM   #2
DonVK is offline DonVK  Canada
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Default slice & dice

The enclosures and drivers are recycled. They're low cost and allow me to try things and set the starting bar.

The donors are the first pic and come from a budget project. I can make a box pretty fast using a pnuematic nailer and glue, I just don't like repeating the same built just to change one small part. The donors were sliced, holes filled and ends capped to make sections that stack neatly (last pic). I will be adding 3 alignment pins to prevent shift & topple.

Initial donor driver set [woofer=tc6028, midrange=pc83, tweeter=td20f]. They cost in total $30 US for the set.
Attached Images
File Type: jpg DSCN5474r.jpg (486.4 KB, 2032 views)
File Type: jpg DSCN5481r.jpg (643.2 KB, 1997 views)
File Type: jpg DSCN5482r.jpg (573.3 KB, 1908 views)
File Type: jpg DSCN5485rf.jpg (550.2 KB, 1889 views)
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Old 2nd September 2018, 08:19 PM   #3
DonVK is offline DonVK  Canada
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Default Initial measurements

A quick set of near field measurements (1/24 oct, no smoothing, no EQ) to see if its working properly. The drivers have different sensitivity that were compensated using the amps to level it out.

XO points were chosen to give each driver approx 2.5 octaves operating range.

sub(s) : 20-100Hz (2.3 oct)
woofer : 100-725Hz (2.86 oct)
midrange : 725-4.5Khz (2.65 oct)
tweeter : 4.5Khz-20Khz (2.1 oct)

Interesting to note. Each driver can manage -50dB THD in its operating range when connected directly to an amp. The driver's are also pretty flat considering their cost and restricted operating range. The tweeter has a a 2db dip from 9Khz-13Khz that could be EQ'd out.
Attached Images
File Type: jpg active 3way near field driver test FR.jpg (111.2 KB, 1890 views)
File Type: jpg active 3way near field driver test THD.jpg (127.0 KB, 377 views)

Last edited by DonVK; 2nd September 2018 at 08:24 PM. Reason: freq typo
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Old 5th September 2018, 02:47 PM   #4
DonVK is offline DonVK  Canada
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Default polars

I EQ'd out the tweeter dip and was curious about the polar response. It's pretty good out till 7Khz. I would prefer less dispersion till about 13Khz. So I'll be looking for a solution or a suggestion?

It seems about right for the driver sizes. This chart (pic#3) is from "Loudspeaker Design Cookbook, Vance Dickason, 7th Ed. Its a reprint from JBL but I couldn't find the original. One possible solution is to add a 1/2" tweeter or maybe get two and use a deflector.

The combined THD is still good (pic#2, -50dB ref) but starting to rise below 100Hz where a sub will take over anyways. It sounds very good.
Attached Images
File Type: jpg polar @r=30cm.jpg (105.8 KB, 334 views)
File Type: jpg On axis r=30cm THD.jpg (96.3 KB, 292 views)
File Type: jpg Loudspeaker Design VanceDickason 7th dispersion vs driver size.jpg (180.2 KB, 229 views)
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Old 6th September 2018, 12:11 AM   #5
Bigun is offline Bigun  Canada
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Modular active 3 way - work in progress
Don - I like your approach, had thought of something like this myself a couple of times but I don't have the knowledge you do so I'm rather pleased I can live this through your work !
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Old 6th September 2018, 12:28 AM   #6
CharlieLaub is offline CharlieLaub  United States
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Looks good! I like your measurement-based approach: no guessing required.

You might next try to do a far-field measurement on each driver. This will reveal the non-flatness...
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Last edited by CharlieLaub; 6th September 2018 at 12:30 AM.
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Old 6th September 2018, 04:47 AM   #7
DonVK is offline DonVK  Canada
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Quote:
Originally Posted by Bigun View Post
Don - I like your approach, had thought of something like this myself a couple of times but I don't have the knowledge you do so I'm rather pleased I can live this through your work !
Thanks, and not a problem to watch the show . Suggestions welcome as well.
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Old 6th September 2018, 04:53 AM   #8
DonVK is offline DonVK  Canada
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Quote:
Originally Posted by CharlieLaub View Post
Looks good! I like your measurement-based approach: no guessing required.

You might next try to do a far-field measurement on each driver. This will reveal the non-flatness...
The polar measurement was out at 30cm, slightly beyond the driver near field measurements, so I could focus on the speaker only. There will be more stepped distance measurements when I attempt to add room corrections. You can see the FR melting.
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Old 6th September 2018, 08:30 AM   #9
Juhazi is offline Juhazi  Finland
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30cm distance is a bit too near to show baffle diffraction right. 1m is ok and with 4-5ms IR gating reliable from around 300Hz up. You can set gating longer and check when you start seeing reflections from ground, walls etc. more and more.

Don, I'd like to see the bass LP slope a little softer below mid, you are attenuating cone beakup too much? WM xo could be lower too, around 400Hz? Distortion of mid alone tells more of our possibilities with it.
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Last edited by Juhazi; 6th September 2018 at 08:58 AM.
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Old 6th September 2018, 08:40 AM   #10
Boden is offline Boden  Netherlands
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Hello Don,


Those resuts are very good indeed, if not exceptional, for a textbook active filter without any delays or corrective building blocks.



Kindly requested: Could you attempt to create 4th order LR target slopes in XSim to overlay over your actual SPL slopes in order to check how close the actual SPL slopes/output matches the target?


Regards,
Eelco
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