What's possible with a modern 3" Midrange ... 3way Prototype

I don’t agree……the rear firing woofer if within 2-3” of the wall behind would couple quite nicely……Dutch and Dutch pull this off with aplomb.
You know how a baffle wall for home cinema is built? Drivers on the back are not possible. And not needed in this configuration. (cause absorbtion around the speakers, no SBIR etc).
With 3 of my speakers you automatical get a singel bass array on your front. The higher sitting 12" has a reason.
 
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Thats close to my plan, I have the 6640, m74a and a couple of 26w8867 for each speaker. How did you like them? 🙂
I use the 8" version of the ScanSpeaks - incredible dirvers! You have all the components for a top notch speaker.
But be aware - M74A is not for pleasure listening! You get every detail of your source material, if there is a hint of distortion in the recording you will hear it. But the natural reproduction in my listening session compared to MD60N is really special. You can be SURE that what you hear is the source and not some behaviour of the speaker.
 
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As people where interested into the measurement speaker I designed - here the pic in the full featured version. The absorption on front reduces influence between drivers and I could not measure corner cancellations/reflections at horizontal angles. 2 of the midrange drivers ... THD is crazy low at 1kHz (important measurement frequency). Passive crossover with speaker protection.

REF100k V1 (FHD).JPG


JF_00012 (FHD).JPG


This speaker will never play a single note of music ... only sweeps and sines. :oops:

p.s.: This is a customer project for industrial use. I only built 2 pieces. When it's against the rules to show here please write me a message, it's probably not DIY any more.
 
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This speaker will never play a single note of music ... only sweeps and sines
What a shame... These speaker needs to play some Beethoven, some Oscar Peterson, some Pearl Jam, some Pink Floyd... As long as you are sharing data about the project, and are not fishing for customers... I can't see how you would violate the rules.

Honestly, an active version of this speaker would be ideal for a soffit mounted studio monitor.
 
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I have HiVi DM7500-6 3" dome measured recently to find out if it makes sense to use in current-drive mode. For that, I attached 6,12 and 24 Ohms load in series (adjusting amp gain to get the same SPL output). Here are the harmonics at 80dB SPL @1m
80-2nd.png
80-3rd.png
80-4th.png
80-5th.png
80-6th.png

The levels of harmonics vary non-trivially with SPL, here on 700Hz and 2000Hz (solid line for 0 Ohm, dash-dotted for 6, dotted for 12 and dashed for 24 Ohm)
tone-700.png
tone-2000.png
 
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I have HiVi DM7500-6 3" dome measured recently to find out if it makes sense to use in current-drive mode. For that, I attached 6,12 and 24 Ohms load in series (adjusting amp gain to get the same SPL output). Here are the harmonics at 80dB SPL @1m
Would you mind to do that with higher level, maybe starting from 100Hz or 200Hz? The THD you measured is in the -10dBSpl to 20dBSpl area - are you sure it is valid? Very likely there is some noise involved.

The level >1kHz without resistor is higher, that's for sure part of the higher THD. It's not easy to get levels matched cause frequency response changes with a pre resistor. It would need some EQing to have precise data.

But the dome seem to behave very well at low frequencies!

@camplo It's not REW, it's an Audio Precision measurement system. https://www.ap.com/
 
Yes I know, is the FR Raw? Meaning no smoothing/averaging? I take it there's no group delay recorded?
I totally missread, sorry! :geek:
It's with 1/24th smoothing to get rid of the FFT "hair", no gating. There are no strong/narrow band room influences as you would normally get with these measurements, it's a special room.
Phase measurements are a bit wonky with Audio Precision (cause as always with acoustic phase you need to get the reference right!) but they seem to just calculate group delay with the acoustical delay, you would need to subtract 2,6ms.
Studio1 close wall - Group Delay.png


Edit - found limits for the group delay and draw them in. With 4th order active filters you get some group delay but it should be not audible?
 

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Would you mind to do that with higher level, maybe starting from 100Hz or 200Hz? The THD you measured is in the -10dBSpl to 20dBSpl area - are you sure it is valid? Very likely there is some noise involved.

The DM7500 has fs=350Hz.
The DM7500 has fs=350Hz, so 100 | 200 Hz would be too low.
I can't do higher levels with Rload=24Ohm - the amp is already at the rail-to-rail.
The harmonics are mostly valid when they are above the noise floor, see the spectrogram and unaligned harmonics' plot below. There is a lot of averaging involved.
80-24-residual-spectrum.png
80-24-unaligned.png
 
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No.
Cause it's a prototype and already gone to the customer. :cool: (with 2 midranges and passive crossover as you see above).

And I will always do at least 1/24th smoothing on frequency responses cause it makes SENSE - even when you don't understand that now... This is not 1/3 or 1/6 advertisment smoothing. But in this case you are lucky, I also did an unsmoothed graph.
That's in 1m distance in my listening room, speaker close to the wall (which it will be in a real installation too - Home Cinema or Studio use). No smoothing. No gating.

Studio1 - 96dBSpl - raw - Level and Distortion.png


That's not your average living room - it's a non environment reference room which also doubles as my measurement room. A LOT of absorption.
 
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