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Old 15th May 2008, 09:14 PM   #1
graaf is offline graaf  Poland
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Default positioning of omnidirectional fullrange speaker

Hi to all!

perhaps You might find this thread interesting:

http://www.diyaudio.com/forums/show...threadid=121385

I propose new method of positioning of omnidirectional speakers,
works with fullrange
no diffusers needed

explanation of attached image taken from the other thread:
Quote:
I have very unusual loudspeakers which I have built some time ago with those room-speaker interface things in mind. These are very short omnidirectional loudspeakers. They are just 20 cm high and have 8 inches wide range driver on top and firing upwards.
The loudspeakers are to work on the floor – the driver is only 20 cm above the floor – and against the wall.

In this positioning they happen to be quite similar to the late Stig Carlsson designs (carlssonplanet.com, but the Carlssons are two-way and much more complicated because of that) but were not inspired by them.
I didn’t know the Carlssons when I was building these and my first and main aim was to eliminate the detrimental effect of early floor and ceiling reflections without resorting to unavailable true linesource (like Beveridge)
The second aim was to build loudspeaker least visually obtrusive, loudspeaker that would be practically invisible in the listening room (which in may case at the time was also a living room). Perhaps it was even equally important goal.

But frankly speaking I wasn’t thinking a lot and I think now that I really didn’t know what I was doing and still I don’t – I have no technical background – and it was and it is all mostly intuitive.

But the outcome appeared to be quite satisfying. This is still work in progress. Achilles heel of the loudspeakers are 8 inches Fostex wide range drivers which have major resonant problems in the break-up area. Out of the box they were literally howling at me. After some driver-mutilating (i.e. tweaking) I can say that these problems are only partially solved for the time being and I am looking for a different driver

Soon I will have a new listening room that is 350 cm wide and 550 cm long. Not too big and not the best proportions but I can arrange it specifically for audio purposes.
I am considering positioning the speakers against the opposite longer walls (scheme attached). Stereo basis would be 330 cm. The listener is to be located 200 cm from stereo basis, 250 cm from both speakers

All this with the questions of minimizing early reflections in mind and particularly with what Dr. Geddes has written on this forum.

A big thanks goes to Dr Geddes!

To my not very big surprise the resulting set up happens to be very much like Beveridge positioning of his line source electrostatics.
best,
graaf
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File Type: jpg room.jpg (10.3 KB, 1285 views)
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Old 16th May 2008, 08:14 AM   #2
graaf is offline graaf  Poland
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the above is not a joke

the setup has been tested and is currently used by myself with Fostex 206E driver based loudspeakers and also by another forum user Ettienne88 with Fostex 167E

best,
graaf
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Old 16th May 2008, 02:37 PM   #3
hm is offline hm  Europe
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Hello,
do you make any measurements to compair it?

my experience with DDD driver and the
TROMBONE .. has shown min. distance to a wall ~65 cm.

Click the image to open in full size.
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Old 16th May 2008, 03:08 PM   #4
graaf is offline graaf  Poland
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Quote:
Originally posted by hm
Hello,
do you make any measurements to compair it?
unfortunately I am not able to make any measurements
I am not a technical person
just a music lover
although I did simple calculations of reflections showing much better (than typical) reflection delay pattern
it is all discussed in the other thread

in case of Your speakers an absorber on the adjacent wall can be required because of their particularly low directivity, Fostex drivers we use are progressively beaming in the high frequencies of course
and also the problem of the ceiling reflection will not be eliminated (I am not sure what is vertical directivity of Your speakers)

Quote:
Originally posted by hm

my experience with DDD driver and the
TROMBONE .. has shown min. distance to a wall ~65 cm.
yes, I am not surprised and I perfectly understand that
this requirement of min. 65 cm distance in case of Your speakers is supported by the same theory that supports positioning right next to opposite walls in my proposal

but, well, instead of discussing theories and measurements why not just give it a try?

the proof of the pudding is in the eating

happy experimenting!

best,
graaf
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Old 16th May 2008, 04:27 PM   #5
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Here is the link to Harold Beveridge's white paper on the subject from 1976.

More info in his patents at bevaudio.com

http://bevaudio.com/White_Paper.htm
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Old 16th May 2008, 04:36 PM   #6
graaf is offline graaf  Poland
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Quote:
Originally posted by Don Bunce
Here is the link to Harold Beveridge's white paper on the subject from 1976.

More info in his patents at bevaudio.com

http://bevaudio.com/White_Paper.htm
yes, that is correct
The idea was inspired mainly by Beveridge and also by Stig Carlsson (both given credits in my first post in the original thread at "Loudspeakers", link above)
I sort of combined their approaches with the results of my own experiments

it appears that true line source is not needed for it to work
an omni speaker, especially a short one (Carlsson-like) and based on a appropriate fullrange driver will do the job

best,
graaf
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Old 16th May 2008, 04:38 PM   #7
graaf is offline graaf  Poland
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oops, the link to orginal thread is invalid
no problem, the link to the original thread once again, now valid: The Advantages of Floor Coupled Up-Firing Speakers

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Old 16th May 2008, 05:28 PM   #8
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by graaf
oops, the link to orginal thread is invalid
no problem, the link to the original thread once again, now valid: The Advantages of Floor Coupled Up-Firing Speakers


Hi, And the point of restarting the same thread is ? /sreten.
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Old 16th May 2008, 06:03 PM   #9
graaf is offline graaf  Poland
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Quote:
Originally posted by sreten

Hi, And the point of restarting the same thread is ? /sreten.
well, do I have to explain myself?
ok
actually two points:
1) the original thread turned into complicated and occasionally hot discussion between us (Etienne88 and me) and Dr Geddes on this specific setup, which was not my intention, I wanted more general discussion on "room-speaker interface"
2) the topic of this specific setup is particularly interesting for omnidirectional and/or full range drivers users and the original thread may be just overlooked (because the title of it is to general)

therefore I also posted a link in "DIY omni directional speakers" thread

ok? am I excused?

best,
graaf
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Old 16th May 2008, 08:35 PM   #10
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Now that your link to the other thread is working,I went back and read through it. I see you have linked the white paper several times already. Oh,well,maybe it will be of some use to others who haven't read the original thread...

A friend of mine has a pair of the Beveridge speakers,he is still waiting for Rick to refurbish the panels,so I haven't heard them properly set up yet.

On my ever increasing list of things to do is build some full range(omni-directional) speakers,will have to try this placement.
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