Lambda Dipole 15 meaurements

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Measurements on my prototype baffle shown below. Taken at 6 and then 12 inches. 0 - 60 degrees in 10 degree increments.

I wonder why the SPLs don't fall off progressively with increasing angle. The distance between the 45° and 60° lines should be at least twice the distance between 45° and 30°.

Your measurements show clearly how the baffle ceases to support constant directivity above 600 Hz. Not the best prospects for the midrange drivers. :(

Rudolf
 

twest820

Member
2009-06-24 10:49 pm
I wonder why the SPLs don't fall off progressively with increasing angle.
I guess that what we see below 100Hz is room gain?
Pretty sure the answer to both these questions is the mic's in the near field, or at least these sorts of things are what I've seen in near field measurements. I've found near field data can be useful for checking details, but design's best done with measurements taken farther out---I generally check the extent of the near field by moving the mic out until the SPL structure converges to that of the far field. I would guess with that baffle the transition to far field happens around a meter.
 
Is it me or it seems you get a lot of bass from such a small baffle? I guess that what we see below 100Hz is room gain?

Up close, these are so flat because of the parameters are specifically tailored so that you only have to overcome the dipole rolloff and NOT the natural rolloff of the woofer as well. High Qts of .94 and low Fs makes for very low bass capability.

Obviously, these closer measurements are not reflecting the inroom response, but I just wanted to show the inherent capabilities of the woofer. I will get listening position measurements for you all later.

I can tell you at the moment though, that I am only using a 6dB/oct shelf @ 80 Hz boosted by about 6dB and am getting listening position response flat down to about 25Hz.

Greg
 
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I wonder why the SPLs don't fall off progressively with increasing angle. The distance between the 45° and 60° lines should be at least twice the distance between 45° and 30°.

Your measurements show clearly how the baffle ceases to support constant directivity above 600 Hz. Not the best prospects for the midrange drivers. :(

Rudolf

Can you be sure that rolloff you see on this measurement is baffle affected this closer, rather than just the natural dispertion of the woofer itself?

I will get off axis measurements of the mids later. I am not 100% set in this exact shape and size baffle, so it could get narrower by the mids if needed, but we always have a tradeoff somewhere. I do not want to go with the Stigerik solution of no bafflews at all.

Greg
 
Have you had the time to measure the BG Neo 10 response?

I attached the graph from the BG documentation.

I'm sure you have seen Zaphs measurements, but if not, head over there first, then compare my measurements to his.

HTGuide Forum - more Neo10 measurements

I don't have my own off axis yet, but I did do some distortion sweeps to compare to his. Look close enough that I feel confident with my methodology.

Greg
 
Can you be sure that rolloff you see on this measurement is baffle affected this closer, rather than just the natural dispertion of the woofer itself?
Well, I reckoned it should show at least in the 12" measurement. Probably twest820 is right here.
I will get off axis measurements of the mids later. I am not 100% set in this exact shape and size baffle, so it could get narrower by the mids if needed, but we always have a tradeoff somewhere. I do not want to go with the Stigerik solution of no bafflews at all.
I see, you got that covered ... :D

Rudolf