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Multi-Way Conventional loudspeakers with crossovers

Active MTM with 18W/8531G00 and some tweeter
Active MTM with 18W/8531G00 and some tweeter
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Old 16th August 2018, 12:30 AM   #11
eriksquires is offline eriksquires  United States
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I think the ring radiator + 18W/8531 is an excellent idea.

For a couple of reasons. I own the Peerless version of that tweeter, it is not exactly the same, but it's almost as good. It's a wonderful tweeter, but the dispersion is totally different to your original. The RR is pretty narrow. The dome you suggested is super-wide.

Also, the 18W/4531 and 8531 measure much better than spec, they can do 2kHz quite nicely. I have them crossed over to Mundorf AMT's around 1,800, but I could have pushed it.

The upper end of the frequency range is really a lost smoother and cleaner than you would think from the spec sheet. May have been an engineering change, because I don't think Zaph's specs show it, but Troels has written about this oddity of SS FR measurements too.

Best,

E
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Old 16th August 2018, 10:20 AM   #12
elagil is offline elagil
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Quote:
Also, the 18W/4531 and 8531 measure much better than spec, they can do 2kHz quite nicely.
Yes, I also noticed! I barely touched the individual driver responses. Also, the tweeter is very smooth. I will upload my measurements and DSP configuration later. A ring radiator would clearly have helped with the edge dispersion.

The speaker is actually no longer an MTM, due to the total height that would have been required. Find attached a (quite horrible, sorry) picture of the first speaker. Surfaces still need finishing and the back is not yet glued in. Also, I need to build a second one.

As you can see, it looks nothing like the proposed design. I built a test box of the design I showed in the first post, but I did not like it much. That is why it is now much simpler in construction.
Attached Images
File Type: jpg 20180816_120816.jpg (927.5 KB, 168 views)

Last edited by elagil; 16th August 2018 at 10:22 AM.
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Old 16th August 2018, 07:13 PM   #13
elagil is offline elagil
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Here is some more data that could be interesting. I did new measurements where I compensated the near field response for baffle step. I did filter simulation in VituixCAD which helps a lot.

Find attached the simulation files for reference. The archive includes the VituixCAD file and the .frd files of tweeter (D2608/913000) and woofer (18W/8531G00), measured at around 15. I included a drawing of the baffle, if someone is interested in rebuilding. There are 14 mm chamfers that are not really required, because they do not do much acoustically.

Below, you also find the final crossover as simulated with VituixCAD. It measures very close to the simulated version, so I am happy with that.

I do not include the vent response in the measurements at this point, but it should be OK. If you have suggestions or see room for improvement, I would be very happy to hear your remarks. Feel free to play around with the simulation file.
Attached Images
File Type: png box_Six-pack.png (79.1 KB, 152 views)
File Type: png front.PNG (22.0 KB, 137 views)
Attached Files
File Type: zip sim.zip (679.3 KB, 3 views)

Last edited by elagil; 16th August 2018 at 07:42 PM.
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Old 16th August 2018, 08:31 PM   #14
elagil is offline elagil
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Another simulation file, with compensation for the 100 Hz dip, since it is also reflected in measurements. I will listen to this setting and adjust by ear if required.
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File Type: png box_Six-pack.png (79.0 KB, 136 views)
Attached Files
File Type: zip sim.zip (679.4 KB, 3 views)
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Old 17th August 2018, 12:46 AM   #15
eriksquires is offline eriksquires  United States
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TRY FELT RINGS AROUND THE TWEETER TO SEE IF IT SMOOTHES out the low end.

Best,

E
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Old 17th August 2018, 10:19 AM   #16
elagil is offline elagil
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Ok, I will try that. However, I do not see myself keeping felt stuck to the speakers, I just don't like the look of it
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Old 17th August 2018, 09:22 PM   #17
eriksquires is offline eriksquires  United States
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elagil,

My speaker fronts are black, so the black felt disappears.
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Old 17th August 2018, 09:32 PM   #18
elagil is offline elagil
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That makes sense! If it sounds good enough, it may even stay. On the light brown surface, the felt layer will be a bit more obvious.
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Old 23rd August 2018, 05:11 PM   #19
elagil is offline elagil
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I made a few final measurements after some more tweaking. Especially the bass was slightly too low in level. Find attached measurements from different angles, as well as an isolated 30 measurement.

I will upload the final filter configuration, in case someone is interested.
Attached Images
File Type: png meas.png (58.7 KB, 66 views)
File Type: png meas_30.png (28.1 KB, 33 views)
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Old 25th August 2018, 04:53 PM   #20
elagil is offline elagil
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It turns out, I forgot to include microphone calibration during my work My microphone reads 4 dB high towards higher frequencies, so I had to change some things.

I moved the crossover frequency up to 2200 Hz, because directivity looked a bit more even. When repeating the measurements, I noticed that both of my D2608 tweeters drop significantly in amplitude from 10 kHz onward.

Is that normal or is my measurement incorrect? I have not seen this behaviour anywhere else.

Find the new simulation results, showing 30 measurements, as well as raw tweeter measurements (0-60, gated at 1m) attached. The 0 simulation is attached separately.

The new crossover is also attached. I added some bass boost for reaching a lower frequency limit of 34 Hz (-3dB), 28 Hz(-6 dB).
Attached Images
File Type: png tweeter_angles.png (58.0 KB, 14 views)
File Type: png box_30_Six-pack.png (126.5 KB, 16 views)
File Type: png XO.png (23.6 KB, 18 views)
File Type: png 0.png (27.6 KB, 17 views)

Last edited by elagil; 25th August 2018 at 05:05 PM.
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