How to Measure Magnepan LRS

[DonH56]

Complex numbers can be expressed as real and imaginary parts (vector) or as magnitude and phase (polar).

 

[mac]

If anyone here is concerned that the LRS will be shown to be lacking "measurement-wise", I'd suggest worrying more about the distortion results we'll see below 200-300 hz....even at 86db....I'm betting it won't be pretty...

Right.

 

[cistercian]

Where did you get that idea?

What an epic piece of test equipment. Bravo!

 

[bunkbail]

I personally never had any experience with dipole/open baffle/omnidirectional speakers like these but reading from other's experiences from many forums elsewhere it seems like these kinds of speakers are benefiting the most from full-range digital room correction. Would you consider to do the test with Dirac on these LRS speakers, @amirm?

 

[abhijitnath]

The problem is that if they're difficult to measure for knippel, they're hard to measure for dirac. And if your measurement is inaccurate, so is the correction. I don't know the theoretical answer, I'm just trying to think about it logically.

 

[amirm]

Would you consider to do the test with Dirac on these LRS speakers, @amirm?

I don't think I will have enough time for such extensive testing but if so, yes.

 

[amirm]

The problem is that if they're difficult to measure for knippel, they're hard to measure for dirac. And if your measurement is inaccurate, so is the correction. I don't know the theoretical answer, I'm just trying to think about it logically.

It is not the same issue for Dirac as it is not trying to compute the soundfield like NFS is.

 

[tjf]

It is not the same issue for Dirac as it is not trying to compute the soundfield like NFS is.

And do you think correction for the near + far field responses for the LRS, or indeed any dipole speaker, might be a tough task for Dirac, ARC, etc., etc., ?

 

[amirm]

And do you think correction for the near + far field responses for the LRS, or indeed any dipole speaker, might be a tough task for Dirac, ARC, etc., etc., ?

It certainly presents a different response to it. How well it handles that, I don't know until I try it.

 

[DonH56]

Because of the back wave any far-field response is hugely dependent upon the room placement and treatment. Not sure trying to correct for measurements is worth the effort.

The biggest problem room correction programs seem to have IME is the reflected wave can be fairly large and introduces comb filtering room correction programs will try to correct. Sometimes they go overboard; another reason to restrict correction to the bass region.

 

[RayDunzl]

And do you think correction for the near + far field responses for the LRS, or indeed any dipole speaker, might be a tough task for Dirac, ARC, etc., etc., ?

I don't try to correct nearfield. That's not where I listen.

It wouldn't seem to present much of a problem at the listening position here at Neverland East...

JBL LSR 308 vs MartinLogan reQuest using AcourateDRC and a miniDSP OpenDRC-DI

 

[RayDunzl]

Because of the back wave any far-field response is hugely dependent upon the room placement and treatment. Not sure trying to correct for measurements is worth the effort.

The biggest problem room correction programs seem to have IME is the reflected wave can be fairly large and introduces comb filtering room correction programs will try to correct. Sometimes they go overboard; another reason to restrict correction to the bass region.

I see a dip at 215Hz in the Martin Logan response that I attribute to the wall behind the speakers: The speakers are about 46" from the wall behind.

The dip is very narrow and falls between a G# and A with 440Hz tuning, so...

---

It surprised me to see a similar dip (Red) in the measure of the JBL LSR 308 (located next to the ML)

 

[LTig]

I see a dip at 215Hz in the Martin Logan response that I attribute to the wall behind the speakers:

View attachment 81815

It surprised me to see a similar dip (Red) in the measure of the JBL LSR 308 (located next to the ML)

View attachment 81819

At 215 Hz the LSR308 still radiates omnidirectional. If it's at the same location you should expect a similar dip.

 

[tjf]

Yeah, my bad on the nearfield thing...I should have just been dubious of Dirac, etc., doing correction for the far field response for dipoles....

"The biggest problem room correction programs seem to have IME is the reflected wave can be fairly large and introduces comb filtering room correction programs will try to correct. Sometimes they go overboard; another reason to restrict correction to the bass region."

I wonder about the Steinway/Lyngdorf approach of using their own boundary loaded/dependent speakers + "room perfect" correction DSP to deal the reflected (low freq.) wave to clear up boundary comb-filtering effects, to sim "RFZ" (reflection-free-zone) in-room performance??? (Steinway system concept posted previously on ASR back in March)

 

[MZKM]

I see a dip at 215Hz in the Martin Logan response that I attribute to the wall behind the speakers: The speakers are about 46" from the wall behind.

Maybe its different because it’s a dipole, but for monopole speakers the SBIR from the front wall will occur at 1/4 the wavelength (measured at the baffle), so 46” would be ~70Hz.

My speaker baffles are ~2ft from the front wall and I indeed have a dip ~140Hz.

 

[RayDunzl]

Maybe its different because it’s a dipole, but for monopole speakers the SBIR from the front wall will occur at 1/4 the wavelength, so 46” would be ~70Hz.

Hmm...

http://tripp.com.au/sbir.htm

 

[DonH56]

Maybe its different because it’s a dipole, but for monopole speakers the SBIR from the front wall will occur at 1/4 the wavelength (measured at the baffle), so 46” would be ~70Hz.

My speaker baffles are ~2ft from the front wall and I indeed have a dip ~140Hz.

The back wave of a dipole is launched inverted with respect to the front wave, moving to the half-wave point for cancellation.