How to Measure Magnepan LRS

[amirm]

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???

 

[RayDunzl]

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

I use "mid panel" for the on-axis of my 'stats.

That point is above my ear level when seated so they lean forward slightly.

The Bosch laser device measures 87.6 degrees. You may ask how I decided on that angle.

I don't know what is inside the Magnepan.

 

[MZKM]

https://www.magnepan.com/pdfs/manual/LRS.pdf

Your speakers come in matched pairs and are mirror-imaged. The serial number for each speaker in the pair is the same except a "1" or "2" follows each serial number. Place speaker "1" on the left and "2" on the right. This places the tweeters to the outside. Whether the tweeter is on the inside or outside, the tweeter should not be closer to the listener than the bass section. Measuring from your seated position, if the bass panel is 10 feet, 6 inches, the tweeter should be at least 10 feet, 7 inches (think in distance, not angles).

Tweeter attenuation-- The tweeter attenuator jumper provides maximum tweeter volume for heavily-damped rooms. Your room may require tweeter level reduction by inserting a resistor in place of the jumper.

When sitting in a low chair or when seated more than 10 or 12 feet from the speakers, the speakers should be tilted forward for best frequency balance. To tilt the speakers forward, pull the top of the speaker forward to allow the flippers on the ends of the feet to drop down. To disengage the flippers simply pull the speaker forward or reach down and rotate the flipper over the top of the foot.

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I’m not sure what to make of that last paragraph, I assume the speaker is tilted back to time-align the drivers, so no clue why sitting far away would require you change this. I’ve also only seen it tilted back or upright, so not sure if “tilted forward” means upright or actually tilted in the other direction, the part in the first paragraph stating the tweeter should never be closer makes he think the former.

Please do the max SPL in the bass measurement, these have low sensitivity so I wonder how much wattage they can actually take.

I am interested to see if the PIR graph will actually come close to how this measures in room.

____

Stereophile measured it:
https://www.stereophile.com/content/magnepan-lrs-loudspeaker-measurements

J.A. got a dip at 3kHz for the listening window, but further off-axis horizontal and vertically off-axis all shows a peak at 3kHz. He measured at mid-panel height.

 

[Koloth]

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

I say pick the height of the ear level of a seated listener. Even though the speakers might measure better at some other height, nobody's going to adjust to that (by elevating their seating position or putting the speakers on pedestals) either way. A seated listeners ear level is the height that' of interest to users.

 

[RayDunzl]

At what distance will the Klippel measure?

Is its measurement movement spherical?

 

[ribosradagast]

Woo boy, this one is going to be a doozy. Maggies are going to be exceptionally difficult to measure since they 0) are bipolar, 1) rely on the back wall for bass reinforcement, 2) have Left and Right matching-pair speakers (or rather, have the "tweeter" on one side), 3) have incredibly narrow vertical and horizontal dispersion - they are the classic "head in a vice" speaker exemplified

I'd use "ear height while sitting" as a measure of where the mic should be placed on the vertical axis. The amount of lean-back can also be changed with included washers, and as you note, so can the attenuation of the tweeter, with supplied resistor. They also need to be time-aligned by angling the speaker so that the tweeter is further from the listener than the bass section...

EDIT: @MZKM beat me to it - the user manual should be studied intently, as every word on it is loaded with meaning

 

[amirm]

At what distance will the Klippel measure?

It is less than 1/3 meter.

 

[mlee]

This might be tricky. I'm not an expert but I think getting reasonable larger membrane speaker measurements is difficult due to size. A combination of nearfield and further away measurements might be needed; however, this might only apply to measuring 1 driver. No help here, might be off topic. Stereophile went slightly above tweeter mid point I think.

 

[amirm]

Is its measurement movement spherical?

It is cylindrical but also measures on top. I am crossing fingers that I have enough height for it to get to the top!

 

[Blumlein 88]

I'd pick ear height for the reference point and in line with the tweeter. 40 inches off the bottom? As mentioned you'd normally toe them so the bass panel and tweeter are in some time alignment more or less with a distant listening spot.

 

[RayDunzl]

Expect chaotic measurements.

https://www.stereophile.com/content/magnepan-lrs-loudspeaker-measurements

 

[RayDunzl]

If you have a pair, send them here when you're done and I'll measure them too...

Just don't tell the owner.

Or, "UPS lost them but they think they know where they might be..."

 

[sfdoddsy]

It's going to be tricky.

All well-designed dipoles have a built-in boost to account for the 6dB octave dipole loss which occurs below a certain frequency depending on baffle width.

Hence the big bass boost seen in the Stereophile measurements.

To get an accurate feel for the true response, you need to measure from the listening position.

AFter years measuring my Linkwitz Orions, and also Maggies and Apogees, I just gave up and did in-room measurements.

 

[wje]

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

Yes, the Magnepans come with both 1 Ohm and 2 Ohm sandcast 10W resistors in the package. If one wants to reduce the treble response, they simply insert the ends of the resistor into the tweeter attenuator jumpers after removing the "U" shaped rod that is currently in place at the moment. After the rod is removed, insert one end of the resistor into one of the plugs, then tighten it down with an allen wrench. Then, perform the same action for the other end of the resistor.

Disclaimer: Sand cast resistors are not Danny Richie approved.

 

[Vini darko]

I wish you the best of luck with this endevor @amirm

 

[richard12511]

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???

Really looking forward to this review.

 

[raindance]

I doubt you'll need to attenuate the tweeters. Centerline of the speaker vertically will be ok, but typically the drive units need 6-8 feet listening distance to "integrate". They don't need a back wall for bass reinforcement. They behave like classic line arrays. They don't have limited horizontal dispersion, that's ancient history since they changed to using foil.

 

[ribosradagast]

They don't have limited horizontal dispersion, that's ancient history since they changed to using foil.

When did they switch to foil? My 1.7i definitely change sound immensely if you move a foot to the left or the right of the main listening position

 

[DonH56]

They changed from typical wires glued to panels to foil traces -- that is their "quasi-ribbon" design (not a true ribbon driver -- different physics).

Limited horizontal dispersion has nothing to do with the panel change from wires to foil; it is all about the size and shape of the radiating area relative to wavelength. They still have the classic dipole pattern over most of the frequency range, changing gradually to a point source at lower frequency and line source (more so for the true ribbon models) at very high frequency.

 

[RayDunzl]

When did they switch to foil? My 1.7i definitely change sound immensely if you move a foot to the left or the right of the main listening position

Opinion (substantiated by measurements):

That's a sign of an extra sweet sweet spot.

You hear the comb filtering of the difference in arrival time (it does't have to be much) of the direct sound from the two speakers.

Some folks prefer a blur, I think.