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In Reply to: RE: Great example of thoughtful well written review posted by ruxtonvet on October 21, 2014 at 19:48:38
JA admits it was "hard to get a handle" on this speaker's measured performance. The open-backed midrange driver has such a different radiation pattern (180 degrees out-of-phase at 180 degrees off-axis, deep cancellation at 90 degrees off-axis) from conventional monopole mounting that quasi-anechoic FR measurements cannot begin to describe how it will behave in a real-world listening room. The in-room-from-the-listening-seat FR curves look a lot better than the quasi-anechoic, but this is with optimized positioning in one particular room. Move the speakers around in the room, or set them up in a different room, and the curves will vary significantly.
This is always an issue with dipoles, and perhaps one of the reasons Magnepan refuses to submit review samples to Stereophile for measurements.
Follow Ups:
There are measurements of magnepans in stereophile as well as other dipole speakers so I am not quite sure what you mean by your comments.
and does not send samples for review to Stereophile. Perhaps not everyone is reminded at each review what JA has observed before:
" As I have written before in these pages, measuring physically large speakers with in-room quasi-anechoic techniques is in some ways a fruitless task. The usual assumption , that the measuring microphone is very much farther away than the largest dimension of the speaker being measured, is clearly wrong . Yet without access to a large anechoic chamber costing many hundreds of thousands of dollars, in-room measurement techniques are all we have to rely on. "
That summarized the 3.6 review conducted back in 2000 - which I believe was the most recent example.
That on-axis FR is HORRID! Though probably it would change drastically with even slight changes in the mic position (as JA noted with the Nola Metro Grands), or with changes in the size or damping of the room, or the position of the speakers therein. And may be totally irrelevant to what YOU would hear in YOUR room.
Dipolar speakers are difficult to set up for optimum performance, and more so to measure, but that's just the nature of the beast. I've heard a few over the years (Maggies, Acoustats, Martin Logans, Carver Amazings), and while all were impressive in some ways, I suspect all would have benefited from having about an acre of mattresses behind them.
> That on-axis FR is HORRID! Though probably it would change drastically
> with even slight changes in the mic position (as JA noted with the Nola
> Metro Grands), or with changes in the size or damping of the room, or the
> position of the speakers therein.
Indeed. And other than in very large room, with a physically large speaker
the listener is sitting in the nearfield, which will exaggerate the bass.
I experienced this listening in 1985 to HP's Infinity IRS V speakers in his
relatively small room. The low frequencies were simply too good to be true!
John Atkinson
Editor, Stereophile
Just drag it out in the middle of a really big field, with no nearby roads or airports (noise sources) or buildings (reflectors), on a nice day, and set up your test rig. All you need is a pallet, a forklift, and a crew of burly movers. Easy peasy!
We'll also need a generator go provide the power and an inverter so we can plug the amp and preamp in.
When they discover the center of the universe, a lot of people will be disappointed to discover they are not it. ~ Bernard Bailey
And may be totally irrelevant to what YOU would hear in YOUR room.
Exactly. I don't listen with an o-scope.
but that's just the nature of the beast.
And the naturalness of the presentation.
I suspect all would have benefited from having about an acre of mattresses behind them.
I find that a small forest of bass traps and diffusers work measurably and audibly very well. :)
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