High Efficiency Speaker Asylum

RE: First in-room Edgarhorn response measurements.

24.13.243.18

In Reply to: RE: First in-room Edgarhorn response measurements. posted by Dan_ed on August 29, 2007 at 10:11:00

Hi

I would also be in the group that says its not bad for in a room.
Keep in mind that even the best measurement systems cannot reject reflected energy below a few hundred Hz in a living room. If you want to see what the speaker itself does, you can measure outdoors keeping in mind the next explanation.

A sharp notch as your graph shows around 70Hz, is nearly always caused by two signals adding out of phase. In that particular case, it is not likely to be the woofer / mid being out of phase but rather the reflected signal from a floor / ceiling bounce.
Here one has the speaker radiation and delayed reflection adding out of phase and canceling out. A “pointy” bottom feature like that CAN’T be fixed with equalization as raising the center F increases both the source and reflected signal.
In this case, the EQ also alters the phase while altering the amplitude, however this problem is NOT minimum phase and so the EQ screws up the phase.
On an RTA, it can appear that EQ fixes this, but that is because of extremely poor resolution and a lack of any phase information.
On the other hand, generally, broad mound features can be perfectly fixed with EQ and an RTA is an ok way to tune this.

The up side is that if you had a typical normal cone / dome speaker and one use a high resolution measuring system like this one *, one would find that because of so much less directivity, that the response is more like + - 20 dB or more variation.
It is humorous that so many are hung up on what a speaker does at one meter when most listen further away. Further away, unless you’re outside or in an anechoic chamber, the more directivity you have, the more similar the responses will be (one meter vs listening position) and the further into the room the direct field extends.
Without directivity, the best one can hope for is an acceptable cascade of reflected sound, which at best sounds ok but ALWAYS competes with the direct signal producing the stereo image and is not part of the recording. In other words, so far as conveying information from the recording, reflected sound is more like “noise” that sounds like the music. With music that fact is not obvious but when you listen to a voice, intelligibility is easy to measure and is harmed by reflected sound.
Best,

Tom Danley

*Here is a TDS based system, most FFT and impulse based systems do not accurately measure acoustic phase but TDS does.

http://www.gold-line.com/tef/t-tefpre.htm

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