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Multi-Way Conventional loudspeakers with crossovers

Corner speakers
Corner speakers
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Old 17th February 2009, 09:01 AM   #1
GK is offline GK  Australia
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Default Corner speakers

I知 planning a pair of simple 2-way speakers for my study, to replace the ancient PYE record player speakers I知 currently using.

Space is at a premium and the speakers will have to stand in opposite corners at one end of the (small) room to have any kind of stereo separation. So I figured why not make a pair of boxes with a triangular cross section?

The speakers need to be reasonably sensitive as I知 using flea-power amplifiers in my study (~10W).

What kind of issues would I be up against (room modes, etc) and what kind of driver / crossover freq / etc selection would work best (or the least badly?) in such an arrangement?


Cheers,
Glen
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Old 17th February 2009, 10:42 AM   #2
sreten is offline sreten  United Kingdom
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Hi,

If you imagine the two walls as mirrors you can see the sort of thing
you are up against, essentially the interference of horizontal arrays.

So possibly a directional (waveguide?) tweeter and careful choice
of the c/o point. No baffle step but you will not get the low bass
boost available to free space mounted speakers (the further
from the walls / floor the lower this comes in. So possibly a
somewhat "fat" (as opposed to "lean") bass alignment.

Balanced against that is the dominance of the room modes
in the bass that would be near inevitable from such siting.

Sensitivity wise you could go for a tall floor stander in the corner
and apply some of the popular full range techniques, e.g. an
expanding folded TQWT like the BIB or a MLTQWT (straight ?).

Is your room so narrow only corner mounting appeals ?
An option for a long thin room is side wall mounted open baffles,
or possibly near side wall placement but away from the back wall.

/sreten.
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Old 17th February 2009, 12:01 PM   #3
GK is offline GK  Australia
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The room is pretty much square. I presume a "fat" bass alignment is one not overly damped?

Cheers,
Glen
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Old 17th February 2009, 12:58 PM   #4
Bill F. is offline Bill F.  United States
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I second Sreten's waveguide suggestion.

Another thing that might work well is a quality coaxial, where the cone profile tends to control the treble dispersion. Coaxials also sidestep some potential integration issues that can come with a quasi-nearfield setup like this. Since directivity is an advantage in this case (along with efficiency), choose the largest diameter cone you can fit on your chosen baffle width.
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Old 17th February 2009, 02:48 PM   #5
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by G.Kleinschmidt
The room is pretty much square.
I presume a "fat" bass alignment is one not overly damped?

Cheers,
Glen
Hi,

Corner mounting is a square room is asking for trouble,
A notch filter somewhere set at 57hz might be an idea.
(Or possibly rolling off before 57Hz, but no real low bass).

Yes by "fat" I mean not overdamped at near cutoff.

What is known as the critical distance might be an issue,
whether you prefer farfield or more nearfield conditions,
see 5-14 in http://www.pispeakers.com/ssdm_99.pdf

For more farfield you need a wide dispersion miniature,
with more normal placement, but this goes against the
senstivity requirements, which are low for a small room.

/sreten.
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Old 17th February 2009, 05:12 PM   #6
a_tewinkel is offline a_tewinkel  Netherlands
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How about building something like the designs by Earl Geddes? They have very good controlled directionality and have very good sensitivity. Or is the goal to completely design a speaker from scratch?
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Old 17th February 2009, 05:27 PM   #7
dwk123 is offline dwk123
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My main system actually has the speakers placed directly in the corners. IMHO if you handle it properly it is a great idea for small rooms. It's not easy, though.

My speakers are the Yorkville U15's, which use a conical horn/waveguide coupled to a 15" midbass @~300hz. The dispersion is even narrower than in Geddes designs at 60 degrees, but this is a huge part of why it works - the directivity is nominally narrower than the corner angle, so the severity of reflections is greatly reduced. The other aspect is that as pro cabinets they dont' have any baffle-step compensation built in - this avoids the 'corner boom' you get if you put a typical fully-compensated audiophile speaker into a corner.

IMHO one of the reasons this works so well is the uniform power response - my setup starts at 60x60 at HF and gently broadens to 90x90 at LF which isn't too bad. Compare to a typical setup that goes from maybe 60x60 at the extreme HF where the tweeter is narrowing all the way to 360x180 below the baffle step and then to something like 90x90 down deep where room gain / quarter-space loading takes effect.

You still need some degree of acoustic treatment right around the speaker for optimal results to deal with reflections, but no more than with conventional speakers in a similarly sized room.
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Old 18th February 2009, 12:04 AM   #8
GK is offline GK  Australia
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Hmmm....... A fair bit to chew on here. A full range speaker is looking like an option, however:

As far as directionality goes would I be right in assuming that a narrow horizontal dispersion more important?

Would a 2-way with quality ribbon tweeter (rotated 90 degrees) crossed as low as possible be a workable alternative to a dome tweeter with a waveguide?


Cheers,
Glen
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Old 18th February 2009, 12:14 AM   #9
CLS is offline CLS  Taiwan
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Oh no! square room! Corner speakers in such room would often yield very big booms. Acoording to the dimensions, they are probably at 57Hz, 115Hz, 230Hz.... I've experienced this with much more than 10dB resonant peaks (concrete borders all around). Never again.

How about using the room as a diamond shape instead of a square? (turning 45 degree) Then you may place the speakers somewhere away the corners.
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Old 18th February 2009, 12:44 AM   #10
GK is offline GK  Australia
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Quote:
Originally posted by CLS
How about using the room as a diamond shape instead of a square? (turning 45 degree) Then you may place the speakers somewhere away the corners.

Not really practical. My only other real option would be to place the speakers maybe a foot from the rear wall at the edges of the window.

They would still be pretty close to the corners though.

Cheers,
Glen
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