How to Measure Magnepan LRS

[Vini darko]

Any tips for placement? I'm still struggling with my spatials

This video may be of help...prehaps.

 

[Wes]

...
The smaller models are more like line sources over a wider range than the larger models.
...

why is this?

 

[DonH56]

why is this?

The size of the panel changes the frequency at which dispersion changes. An infinitely large panel would generate a wavefront essentially straight ahead (and back) for all frequencies; an infinitesimally thin line would be a pure line source (but hard to get bass out of it).

 

[helom]

These panels are so sensitive to placement, the room, and ancillaries that any measurements are effectively useless to potential buyers. They’re going to post terrible measurements by any objective standard, but people who own and enjoy them buy with their ears.

 

[Newman]

I already explained in my previous post.

What you said was, "every measurement is performed at one point." So I showed a video of the Klippel taking measurements from many different points. So I ask again: where did you get that idea?

You seem flummoxed by the basic physics of this.

Hmm, pot/kettle/black?

The microphone is way inside the nearfield of a longish transducer.

Duh. See post #33 in the Klippel thread, which "Mr Flummoxed" wrote all by his flummoxed self.

It would be impossible for a single measurement 'not' to exhibit some form of comb-filtering. If you can't grasp that I'm not sure what to say.

If you can't grasp that the Klippel NFS is not a single measurement, after the video I've shown you, then I'm the one who is not sure what to say.

I have already noticed several comments in this thread, from people who seem to be Maggie fanboys who don't want to hear potential, possible bad news from the measurements that Amir is about to conduct, making preemptive strikes to invalidate the measurement before it even starts.

The near-field vs far-field issue being the weapon of choice.

Well, at risk of repeating myself but not seeing any real option, please read posts 31-38 in the Klippel thread, which I keep linking to. And note that it is I who raised the question there, weeks ago, so please don't scoff at me as though I don't understand the line-source nearfield/farfield issue.

And, now that I understand Klippel NFS slightly better, I realize that the nearfield/farfield issue does not apply to it. Because once we measure and model a soundfield, instead of just taking a bunch of SPL readings, then we can predictively model all soundfields that the DUT will generate. At all distances.

It doesn't matter if the DUT is a point, a line, a sonic laser beam, or a pulsating sphere. Or anything else. Once the 3D soundfield is modelled, then its response can be derived at any distance, at any angle. If the DUT is a perfect line source, and its response behaves as per the predicted near-to-far transformation theory for line sources, then Klippel will model that.

cheers

 

[richard12511]

 

[Thomas savage]

Post deleted , let's not lose our minds and be rude towards one another please

 

[Juhazi]

I'm curious to see how Klippel NFS works with a dipole source. At long wavelengths dipole cancellation/summation takes some distance to happen.

 

[LTig]

I'm curious to see how Klippel NFS works with a dipole source. At long wavelengths dipole cancellation/summation takes some distance to happen.

Yep. Maybe @amirm can show FR for several listening distances.

 

[Newman]

I hope so too

 

[amirm]

As you say, you have measured tall speakers and the results look great. In (some of) those there is a rise or flat response near 20Hz region at very low level. Is this perhaps related to noise level or could the port be the cause if very low and possibly inside the measurement shell (I was talking about)?

Yes, it is usually due to noise floor and too little output from the speaker at those frequencies.

 

[amirm]

Can I read somewhere about the scanning distance and the accuracy in very low frequencies?

There is no documentation for it. But the system during field identification complains if distance is too small relative to order being asked in low frequencies. Usually the sound field is quite omni directional but if for some reason it isn't, then measurement distance needs to increase since far field is quite a bit farther in low frequencies.

 

[amirm]

Yep. Maybe @amirm can show FR for several listening distances.

What distances do you want to see?

 

[Newman]

What distances do you want to see?

From my earlier request,
"In that case, I will be interested to see Amir's NFS measurement of the Magnepan LRS (quasi-line, open-baffle, dipole) shown as Spinorama and beamwidth plots modelled at 2m and at 6m distances, which are realistic ranges for home listening, and which the graph I shared above predicts will differ in more than just SPL. "

 

[amirm]

The spinorama is already at 2 meter (but reported at 1 meter).

 

[Newman]

I'm just interested in seeing how much 'quasi-line-source-y' response change we get across the typical range of listening distances. As a line source, it's pretty badly truncated, so I don't expect true line source behaviour, but hopefully being in-between point and line is not too bad.

 

[Ville]

There is no documentation for it. But the system during field identification complains if distance is too small relative to order being asked in low frequencies. Usually the sound field is quite omni directional but if for some reason it isn't, then measurement distance needs to increase since far field is quite a bit farther in low frequencies.

Hmm... That is kind of counter intuitive given the attenuation of higher order components with distance. This means my intuition is lacking and I need to study. The system needs and makes measurements at different distances to solve the radial components. Which distance exactly needs to increase, the inner or the outer radius, or maybe both?

Edit: Actually it makes sense thinking about a dipole source, for example: The lower the frequency the larger the source has to be and the further away the source-free region is. Maybe the system does not use all the sampling points for the lower frequencies. I think it does not need to.

 

[raindance]

High frequencies do not follow the inverse square law for a line source, but 6m as a typical listening distance? Why would you want to hear that much of your room? 8-10' max for these little guys.

 

[LTig]

What distances do you want to see?

2m, 4m, 6m should cover most applications.
Edit: for a first panel speaker it makes sense to see also 3m and 5m, to get a feeling how a panel works.

 

[Jimbob54]

Hello everyone. I am getting close to measuring the Magnepan LRS and wanted to get some feedback on how to stand it up for testing. It normally tilts back:

It is easiest to measure it as picked as the legs can be horizontal on measurement stand.

Second question is what the "tweeter axis/point" should be.

I also heard it has resistors to change tweeter response???

Im more interested in how you play music from a fireplace?