B139, B110,T27, was the "classic" trio, I have a set knocking about if anyone can tell me what to do with them....fnar fnar
Right, I had a set that someone slathered with bituminous felt to "damp" out badness and gave it away years ago.
If you all think I'm nuts with this dynamics talk then consider this. Every time you double the number of drivers you get a +3db increase in efficiency (to a point). This is not electrical but purely physical. Its not from an increase in surface area either as evidenced by the fact that it only full occurs at frequencies within 1/4 wavelength distance.
Now this "magic" increase is purely from the drivers kinetic motion being better transmitted into the air, probably because the sound wave emerges from multiple points and forms a larger front as well.
If you listen to strum @*s James Taylor stuff dynamics doesn't matter as much, but its there.
Now this "magic" increase is purely from the drivers kinetic motion being better transmitted into the air, probably because the sound wave emerges from multiple points and forms a larger front as well.
If you listen to strum @*s James Taylor stuff dynamics doesn't matter as much, but its there.
I have a pair of B139 still in their box, only tested the BL curves which were not exciting to look at, otherwise still new. I guess I could sell them at high price vintage...
You are in the near field of the transducer where the sound does not fall off as -6 dB / dd.
Its +6 dB for coherent sources < 1/4 lambda apart and it comes from the mutual radiation impedance of one source on the other. Each source loads the other source making it more efficient. This is not "dynamics" but simple physics. "Dynamics" is perceptual, and as I say, nothing that I have heard sheds any light on its physical reasons. Toole/Olive pretty much discount it altogether. I am not so certain, I think I can perceive it, but I don't know what it is.
I'm pretty sure its +3 physically which is double in terms of power, then there is an additional +3 from increased current draw if they are in parallel (half the impedance).
I think that saying the different drivers or points in space "load" each other is the same as a multi point wavefront. Dynamics is of course subjective, but this relates to dynamics in that there is a better coupling and more effortless interaction with the air.
If you ignore the speaker for a moment and just think of a soundwave then what makes one wave dynamic or another not? This is partly why there is no scientific definition. It may have something to do with the wave coherency or lack of compression. Maybe the wave is more "clean" in that the compression and rarefaction are more symmetrical and aligned in time.
Might be that Dr. Geddes knows more than you on this topic.
I believe Tom Danley would agree with Dr. Geddes regarding the interaction between the drivers.
Dr Geddes knows more than me on acoustics, thank you Sherlock Holmes. There actually isn't much of a disagreement, the +6 includes electrical coupling.
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Are you saying that you understand that there is a +3 dB due to acoustic coupling or that you believe it is "electrical coupling" instead?
+ 1 to the last post regarding the origin of the 6dB increase !
Something else:
What Earl said regarding the basket and magnet acting as as resonator makes sense and I am conviced that there is a resonance caused that way. Some people who are quite picky fix their magnets against the back panel of their enclosures. There are even some who say the the magnet should be mounted firmly to the enclosure and that the monting rim should be free and just some sealing used in this area but no screwing of the rim agains the baffle.
It would be interesting to make a nuckle test against the magnet (laying face down or mounted) of one of the drivers that Earl measured and see whether it is the same frequency as where the SPL dip happened.
And again something different:
What I always wondered is whether there are no negative effects of the cone breakup between 1 and 2 kHz of these 15NBX100 with the crossover frequency less than an octave from it (I am talking about the Summas).
Kind regards
Charles
Something else:
What Earl said regarding the basket and magnet acting as as resonator makes sense and I am conviced that there is a resonance caused that way. Some people who are quite picky fix their magnets against the back panel of their enclosures. There are even some who say the the magnet should be mounted firmly to the enclosure and that the monting rim should be free and just some sealing used in this area but no screwing of the rim agains the baffle.
It would be interesting to make a nuckle test against the magnet (laying face down or mounted) of one of the drivers that Earl measured and see whether it is the same frequency as where the SPL dip happened.
And again something different:
What I always wondered is whether there are no negative effects of the cone breakup between 1 and 2 kHz of these 15NBX100 with the crossover frequency less than an octave from it (I am talking about the Summas).
Kind regards
Charles
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I imagine that the math model of the radiated energy gradient pattern from the membrane of a real loudspeaker to the infinite will be complex (and not perfectly accurate).
For me it is the ability of a loudspeaker to reproduce a complex audio signal, when there is a huge spike in the aperiodic sinusoidal signal, i really like to see it on the mic measurements (real complex audio signal, not an artificial meaningless impulse sound)
PS : the basket and magnet are acting as as resonator, as the assembly grow in rigidity the fundamental resonant frequency grow up, at which frequency the assembly is resonant ?
Pretty high, no ?
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It's all about displacement. Small cones with large excursions can move as much air as the reverse, with as much control of motion. So it is not dynamics that are at play here. It is just that distortion and excursion are strongly correlated, so that at a given SPL, large woofers may be expected to distort less than smaller ones. However, design trumps all, and there are some remarkable woofers out there that have large excursions with low distortion.
I don't understand the difference you make between physical and electrical efficiency.
Yes, it made it play very low in a small enclosure, but the large mass also limited efficiency and hence the sound pressure the driver was able to produce.
Don't forget you are also doubling BL every time you double the number of drivers! So the basis is purely electrical, in combination with a doubling of the radiating area.
I am quite curious, when fixing the magnet agains the enclosure, seems that it is stiffening, damping, of changing enclosure wall resonances more than the driver magnet and basket to me, just looking at the stiffness of these. Has anyone really done an investigation?
Tannoy used a blob of putty type substance between the back of the driver and the bracing. In the Royd minstrel and large rubber block with the consistency of raw jelly (if you dropped it on the floor, it wouldn't bounce) was wedged in-between the back of the driver and the back wall of the cabinet.