Desktop Dipole Monitors

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That was a fast build ;) looks sci-fi too !!

Is the total area of the holes larger than the driver Sd. Otherwise the holes will behave like ports tuned too high in a miniscule "cabinet":eek:
For the rear wave, only the low frequencies will be able to exit the holes and the mid-high would likely get attenuated too much , providing no dipole cancellation to the front wave.:confused:
 
Yeah, the whole point of the build was to attenuate the beaming high frequencies, the ones that don't make it around the driver.....this will stop them from reflecting off of the wall, while letting the frequencies that cause dipole cancellation to cancel the font wave, retaining the null to the sides.
I will test tomorrow to see if it works.

Thank for the compliment!
 
ok, they are up and running.
I haven't had time to measure, I just eq'ed by ear.
I will measure tomorrow. there is a huge null at the sides from what I can tell, even high frequencies! I think this experiment is working :)
They sound really great! (for stereo)
and yes, my desk is tiny....because it's not a desk. It's a piano bench!

20121217_205123_zpsda39a9bc.jpg
 
that is neat.
Like tamborines without the cymbals.

I wonder if the monitor messes things up.

race working well ?

truly inspiring.
You are a mover and a shaker here.
I'm sure I'm not the only one who looks forward to your projects.

Only 1,447 views.
That's not 1,447 different people is it ?

Norman
 
that is neat.
Like tamborines without the cymbals.

I wonder if the monitor messes things up.

race working well ?

truly inspiring.
You are a mover and a shaker here.
I'm sure I'm not the only one who looks forward to your projects.

Only 1,447 views.
That's not 1,447 different people is it ?

Norman

Thanx Jon!
Yeah, I think they have like a Nordic kind of a look. Like something you would find in a shop in Stockholm or something.
Yes, the monitor changes the sound a little, not too much its partly in the null.
I'm not using RACE on this one, but I sure do miss it ;)
I am surprised at the great clean bass, very balanced.
Of, course they have that exacting nearfield sound.....not my favorite.
I like reflections.
So, yeah....they sound like studio monitors. Mission accomplished!
:D
 
Hi Melo,
with the lower frequencies cancelled from the sides and nothing coming out of the back, these speakers would have a really narrow polar response. Even narrower than a monopole with large drivers. So no reflections at all from the sides or the rear...almost like listening in an anechoic chamber with only direct sound. Do they actually sound like a speaker in an anechoic chamber :eek:
 
Well, I've never listened in that environment.
I'm sure there is a little bouncing off the monitor and the desk and maybe some diffraction, but yeah...kinda boring sounding. Like lasers implanting information into your brain :)

THIS. iS. MU. SIC.
(that was said in robot voice)

I'm in the middle of testing right now, I'll post measurements soon.

The lower frequencies are coming out of the rear (and I'm not talking about that bean borrito I ate last night)
They are omni so they radiate all around but are cancelled on the sides. The high frequencies are also coming from the back, just not the beaming ones, so there wouldn't be a strong reflection coming off the wall. So, I guess it's like a horn or waveguide accept with the ability to cross over much lower to have a good vertical polar response.
 
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Ok, here is a 1/3 octave smoothed response.
The LF is raised by about 3db to compensate for the noise floor.
I applied a rising response to the HF because i'm about 5 degrees off axis.
This is all I had time for today, I have to go to work.
crossover - 300Hz 48db LR both high and lowpass. there is a 12db boost at 150Hz on the HF driver to keep it flat for the crossover.
Tuning by ear yesterday sounded good, but now it sounds insanely good.
:D
I will do unsmoothed and distortion measurements tomorrow along with off axis if I have time.

dipolemonitor3dbsmoothed_zps1cf283d1.png
 
well, it's a full range driver so the HF are beaming and not making it to 90 degrees,
so they won't cancel each other.
So, I have damping in the cabinet to attenuate the rear frequencies from around 4kHz and up. the lower ones (below 4kHz) are left to cancel the front frequencies...giving the dipole null without the beaming HF that would otherwise bounce back from the front wall without the cabinet and damping material.
 
Alright, after listening to these babies for a few days and many hours, I can tell you as far as stereophonics.....I've heard none better.
I can even get a pretty solid center image, I think this is due to the fact that the full range drivers have natural crosstalk avoidance down to where they stop beaming (around 4kHz) so there is no diffraction off the surroundings and a lot less diffraction off the head shadow. Of course it does not compare to ambiophonics but for stereo, very nice.

There is not much interaction with the video monitor and none with the room (in the near field)
I changed the crossover point to 450Hz 3rd order butterworth. I was getting phase issues with the LR 8th order, along with group delay.

I think open baffle monitors with full range drivers should be used on the mixing desk. They have the properties of horns or waveguides but with the ability to cross over very low for an outstanding vertical polar pattern.
These are 1/4rth wavelengh driver spacing at the crossover point.
Granted, the FR gets a little wonky at the top off axis but they don't hit the monitor because the monitor is in the null (not the dipole null but the beaming null) you can see from the previous graph that I posted....these frequencies are 15-20db down, also by the time those frequencies get back from the sidewalls, they are way down in amplitude.

I will be building another set completely out of baltic birch using these drivers.

Dayton Audio RS270-8 10" Reference Woofer 295-357

Tang Band W4-1337SDF 4" Titanium Full Range Speaker 264-916

I will be able to get the crossover point down to 300Hz with the TB.
They will also play 6db louder before linear max excursion. With a LR alignment at 40Hz......that will be 94db at 100Hz 1 meter (listening position) That's comparable to floorstanding reference amplitude (if sitting 3 meters away).
 
That's really cool, well done!
Given the SPL and directivity requirements, one could maybe built a similar 2 way with the Neo 10?
Melo, Ambio still does not work for me.. :( I tried again with my Watson run FR, no setting provided the effect and I tried everything. Surprisingly, the ambio test files on the Southampton university site works really well!

Virtual Acoustics and Audio Engineering: Download
 
That's really cool, well done!
Given the SPL and directivity requirements, one could maybe built a similar 2 way with the Neo 10?
Melo, Ambio still does not work for me.. :( I tried again with my Watson run FR, no setting provided the effect and I tried everything. Surprisingly, the ambio test files on the Southampton university site works really well!

Virtual Acoustics and Audio Engineering: Download

You really do not want to run the Neo10 as a fullrange, even with EQ. There is something nasty going on around 5KHz. I've heard it for years in mine if I let them run that high. Keep it as a mid and it's the best. Erin over at the TechTalk forum measured mine:

BG Neo10 Testing

Greg
 
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