• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

MRR Mini Monitor Ribbon - The perfect directivity?

Joined
Dec 8, 2020
Messages
62
Likes
146
Location
Austria (South-West of Styria)
#1
Hello Forum,

a few yeras ago i have build this speaker heree, a very special design and is in use for my "Home-Theater", that means this system is responsiblbe for the perfect sound from the Flat-TV.
The system is called "Mini Monitor Ribbon" from the german DIY-Magazine "Hobby HiFi". This speaker is equiped with the famos ribbon tweater from bulgaria, the Expolinear NDRL 81mkII and the Italian Bass Hypergraph 130K.
The Housing is self made, body in a luxury furniture and front covered with the finest leather quality you can get. A lot of work to do that in that way.

Hera are the finished housings.
MRR1.jpg

The furniture is mirrored for both systems. That was horrible to do. All angles are 45° chamferd and glued togeher exactly.

MRR2.jpg

BR-Port goes to the rear side. Termial is form Mundorf.

MRR5.jpg

Crossover with the finest components from Mundorf and Inter Technik. The Bass Coil is a relikt from my first DIY-Speaker, the Dynaudio Gemini (Long time ago...)
This is the bass-section.
MRR6.jpg


And this one for the tweeter: Sliver glimmer bypass condensator.
MRR8.jpg


In comparison to the chassis, the crossover is realy huge. The left platine is for impedance linearisation. Useful for tub amp operation.
MRR10.jpg

The build in crossover for the tweeter in the cabinet.
MRR11.jpg


And here, the build in crossover for the bass system. Horribel to fix th screws on the back side.

MRR12.jpg


The hole for the Mundorf M-Connect.

MRR13.jpg


And the finished speaker looks like this:

MRR14.jpg
MRR15.jpg
 

Attachments

OP
EXIF68
Joined
Dec 8, 2020
Messages
62
Likes
146
Location
Austria (South-West of Styria)
Thread Starter #2
So and here are some measurements of this system:
Mic position between tweeter and bass, 1m distance. Measured with "Fuzzmeasure Pro"

Frequency Response:
MRR_15_Degree.png

Step Response:
MRR_Step_Response.png


And here the Frequency Response
Light blue: On axis
Yellow: 15 Degrees
Dark blue: 30 Degrees
Orange: 45 Degrees
The system shows a nearby identical response from 0 to 30 degrees. 45° shows a little fall of. In the area between 1,5kHz and 2,5kHz the influence of the bass is visible. Cross-Over frequency is somewhere about 3kHz.
For my opinion the only weakness is visible in the area about 1-3kHz. But the differences are not very huge.
MRR_0_15_30_45_Degrees.png


One weakness: Harmonic distortion in the treble is a little bit high: This comes from the ribbon tweater.

MRR_Harmonic_Distortion.png


And finaly the waterfall diagramm. No resonances outside of the 90Hz room resonance.

MRR_Waterfall.png
 
Last edited:
OP
EXIF68
Joined
Dec 8, 2020
Messages
62
Likes
146
Location
Austria (South-West of Styria)
Thread Starter #3
And additionally the nearfield measurements:
Nearfield measurement from bass system, port on the rear side, tweeter. Mic distance e.g. 0,5cm from the membranes.
As you can see, the port resonance at 850Hz is strong, but not relevant due to back side mount of the bass reflex port. A little bit confusing for me is the tweeter responce in nearfield. thas doesn´t correlate with the 1m measurements.

MRR_Nearfield.png
 

thewas

Major Contributor
Forum Donor
Joined
Jan 15, 2020
Messages
2,323
Likes
5,010
#4
Very nice built and as all HH magazine loudspeaker nicely flat on axis, although it should be also said that for perfect directivity more horizontal and also vertical angles are needed and there such designs usually are less optimal.
 

bigjacko

Senior Member
Joined
Sep 18, 2019
Messages
389
Likes
176
#5
Wow the directivity is good, if you can address the diffraction a bit more the 2.5k to 5k region will be even better. Do you have measurement after 45 degree?
 
OP
EXIF68
Joined
Dec 8, 2020
Messages
62
Likes
146
Location
Austria (South-West of Styria)
Thread Starter #7
So, here are some measurements.
Graph no1: Horizontal directivity:
dark blue: 0°
green: 15°
orange: 30°
yellow-green: 45°
pink: 60°
orange: 75°
violet: 90°

MRR_Horizontal_15Deg_Steps.png


And here the vertical directivity on axis:
green: 0°
orange: +15°
türkis: +30°
pink: +45°

MRR_Vertikal_Positiv.png

And here in the opposite direction (to the floor.
Also measured on axis:
green: 0°
blue: -15°
orange: -30° (problematic, floor is very near! speaker stand not high enough)

MRR_Vertikal_Negativ.png
 

bigjacko

Senior Member
Joined
Sep 18, 2019
Messages
389
Likes
176
#8
The directivity is good. What is the crossover frequency? Around 3k Hz? There is a bit sudden change in directivity at 3k Hz.
 

thewas

Major Contributor
Forum Donor
Joined
Jan 15, 2020
Messages
2,323
Likes
5,010
#9
So, here are some measurements.
Thank you, where was the rotation axis as the level below 300 Hz shouldn't differ as much?
(But this can be also easily fixed with a numerical offset afterwards).
 
OP
EXIF68
Joined
Dec 8, 2020
Messages
62
Likes
146
Location
Austria (South-West of Styria)
Thread Starter #10
My measurements are not 100% professional standards. I don’t have a speaker rotation plate. I’m rotating the speaker on its stand and measuring the angle by a shool triangle with angle indicating. Why the level below 300Hz is reduced with increasing angle...I don’t know, the measuring conditions are all the same. A few cm difference to the acoustic center of the speaker is also possible.
for my opinion the speaker is really ok. Is sounding very neutral and with a very precise bass reproduction (Speaker placement on the Sideboard, 15cm distance to the wall on backside) Perfect for movie sound effects. And also voice reproduction is very good. and due to the fine horizontal dispersion you don’t need to sit in the middle of the speaker triangle for perfect room information. (Digital output from the flatscreen, benchmark DAC1, HiFiAkademie Poweramp P6 class D 2x250W)
crossover frequency is 3200 Hz.
 

bigjacko

Senior Member
Joined
Sep 18, 2019
Messages
389
Likes
176
#12
Maybe because at 3k the woofer's directivity is low but tweeter's directivity is high, so +15 degree will not be the same as -15 degree. But why does that make this difference?
 

thewas

Major Contributor
Forum Donor
Joined
Jan 15, 2020
Messages
2,323
Likes
5,010
#16
Ahh, thank you, make sense. But how do you solve the phase now? Change polarity? I think there is no way to change the phase or timing of driver except some all pass filters.
Would need a complete crossover redesign to change the relative phases of the drivers which is always a compromise on passive or active IIR crossovers as it depends also on the xover frequency and slopes.
 
Top Bottom