planet10 said:
It is rougher looking as Jim noted. Some areas are pretty severe looking. Even with a smooth response on one axis or several axes, taste comes into play. As drivers get more ragged, it's harder to make any judgements as to perception from measurements such as those, so taste becomes even more significant, at least as I see it.
The upstream electronics are going to enter the picture as well. I would hesitate to do that tweak, but it comes down to preferences. If you like those changes, I say what's there to argue? People like what they like. A DIY tweaker just needs to have an idea of what may occur. It's pretty evident in that graph.
As far as the enabl treatment, I don't care to get into that.
Dave
Yes, it is rougher - but how significant? If +/- 3dB is generally accepted as the limit of audible swings in an FR chart (I read that somewhere), then the +/- 5 or 6 that we see on-axis here may not be dramatically audible.dlr said:
Also cone acceleration will be slightly improved: less mass / less air resistance / same force. Which just might improve (a little) the speaker's ability to follow complex waveforms accurately. In fact, you are sort of creating a slightly smaller driver.
I also notice that all the Lowther images I see have phase plugs - including some incredible mushroom-shaped things. Presumably these are designed-in, but also must be thought to have some improved function over a simple dust cap.
And my gut feeling is that the fe206e dust cap simply must be sonic poison - it has a hole about 1cm across with some fine mesh in it. The edges of that hole must surely produce nasties at high frequencies.
Time to get some FR software methinks - I do have a reasonable condenser mic to hand.
Alan Hope said:
Those are significant. What's considered Just Noticeable Difference (JND) depends on the a number of factors, frequency range, Q, peak magnitude, etc. JND is varies.
I believe that some current test methodologies require tolerances of +/- 0.25db for settings.
Cone acceleration alone change has nothing to do with following a waveform. The ability to follow a signal is directly related to the frequency response. In fact, the increased swings shown in the FR are a direct indicator that the driver will not be able to reproduce the input signal as well as before the mod. You may like the sound better, but it's not as accurate in comparing the before/after curves.
The lower mass will, however, alter the T/S parameters and the driver sensitivity, but I don't see much difference in sensitivity in comparing the two sets of measurements. The system tuning of the box/driver will also change as a result. That alone could account for some of the perceived difference.
You're making a judgement based on looks. A driver designer doesn't put a hole in the dustcap at random. I would not presume at all what you have. I would presume little or nothing based on that characteristic. Don't fall into that trap.
Dave
dlr said:
Dave - You dismiss my comments a bit too lightly - I am well aware that I am not an expert in this field, but neither am I completely ignorant. Found one of my sources - is this all just rubbish then?
http://forum.ecoustics.com/bbs/messages/34579/131062.html
0.25dB! Either peak or trough, now that represents an extraordinarily subtle change in timbre / position in soundstage. Might be required for some sensitive lab tests, not for my living room!
My understanding is that cone acceleration is the physical mechanism that actually produces the sound wave. The cone responds to the varying current in the voice coil by producing a corresponding varying acceleration.
Ok it is OBVIOUSLY frequency dependent to the extent that for a given volume high frequencies require more acceleration and less absolute displacement than lower ones ... and yes HF is produced by a complex shiver rather than a piston effect.
However these concepts are surely part of the whole FR driver concept (and trade-off): big strong magnets + wafer thin light cones = superb cone acceleration = high dB per watt and a delightful subjective clarity of sound. Downsides being a lumpy FR plot, mechanical breakup distortion with loud complex sounds, cabinet effects, etc.
And read my post again - I'm just thinking aloud here - not taking sides. Relax man!
Alan Hope said:
I'm not dismissing the comments lightly, I'm trying to address them directly. In particular, I take strong exception to this suggestion of yours:
First, +/- 3db is not generally accepted as the limit, not at all. +/- 5-6 db is in almost any situation significant, whether of high or low Q. That's not acceptable to me in any form. I'm not a full-range fan, but that's just me.
Much depends on the Q of the peak/dip. If that change is from, say 1-3KHz, it very might make the system sound subtly more forward, just 0.25db. Make it a small peak at 1K, maybe you'll hear it, maybe not. Make it a dip and it may be benign enough that you don't notice. Peaks are more noticeable than dips, so it depends on the specifics. The changes noted in the driver modified are pretty significant in many ways. I've found that for final adjustments I make by ear (yes, I do that by ear to some degree), generally in setting the tweeter level, a change in that range, but very broad (as in the tweeter sensitivity) makes the difference between good and excellent.
It's not the acceleration per se, it's the volume velocity creating a pressure wave. A music signal is a set of periodic waves under continuous acceleration/deceleration. What matters is the pressure of the wave produced. The driver is actually undergoing its peak acceleration at the points where the velocity is zero (magnitude maximum/minimum) for a sine wave. A microphone diaphragm and the ear drum do not move much differently from low to high volume, it's the pressure change that is sensed.
It's not the absolute displacement, it's the volume velocity. For two drivers having different effective diameters ( thus areas) to produce the same SPL (pressure wave) they must produce the same volume velocity. That is, the smaller one must undergo a higher total linear displacement to produce the same volume displacement. It's easier to think in terms of woofers for this. You need a driver with more displacement capability to get the same amount of bass in comparison to a larger woofer. But if you look at acceleration, the smaller driver has a higher acceleration at any given point in the cycle if the SPL is to remain the same as that of the larger driver.
If you believe in that. I don't. High sensitivity drivers don't sound better to me in any meaningful way. That is not high on my list of requirements for a driver nor for a system. As some folks say, "watts are cheap". Now if you want something for a SET amp setup, sure, you need high sensitivity. I don't.
And read my post again - I'm just thinking aloud here - not taking sides. Relax man!
I am relaxed. I answered in a straight-forward and, I thought, fairly unemotional way. And in this post, just clarifying things as well. I think you're over-reacting just a wee bit.
Dave
dlr said:
No worries. I am fine with most of what you say. Volume-velocity is a new concept to me ... however
Volume-velocity
True. ... Hey, I'm learning. Thanks.
And there's that personal aspect. I have a pair of IPL S4s (commercial kit transmission-lines) in the same room as my FRs. They have an exemplary FR trace, but I prefer the FRs on virtually ALL types of music - FR lumps and all. And I listen to a wide range of stuff.
Cheers, Alan
Alan Hope said:
No worries. I am fine with most of what you say. Volume-velocity is a new concept to me ... however
Volume-velocity
Cheers, Alan
However what?
From that page:
"The volume velocity may also be described as the surface area of the source multiplied by the normal surface velocity."
Surface area times velocity. Two drivers of different surface areas require different normal surface velocities to produce equivalent volume velocities, hence (roughly) equivalent sound pressure levels. I add roughly to the description because the two drivers will not radiate precisely the same 4-pi response.
Dave
soongsc said:
Boy, this thread is full of conjecture and sweeping generalizations.
Who is "we" in the above statement. " I" understand (and have used) that there are exceedingly crappy SET amps, very good mega 100's watt amps, lousy valve amps, really good low power designs, etc. ad nauseum.
Some are easy to design, some are more difficult. Not much of a point to this rather self-serving post... seems to be a "preaching" sort of thing, as in "if you don't realize the infamous "first watt" is what counts, and "the devil is in the (low level) details " you must have a tin ear implication... presumptious that "we" should all need to be educated in such things in an attempt to discredit high power amps and "watt's are cheap", which they are when it comes to amplification.
John L.
dlr said:
At least you seem to agree amplifiers can sound different. (and if we can't completely quantize the sound of an amplifier, how can we quantize a speaker?)
George pretty much nailed it. Anytime you have to parallel output devices you are making a necesary sonic compromize. And even using 2 in PP has some issues (but so does the single output device). And then pushing PP into class AB further compromises sonics. It is certainly possible to engineer around much of this, but the bigger the amp the more work it is.
dave
planet10 said:
At least? What's the implication behind that?
That implies that you actually reject objectivity, so at least we know where you stand. We can't quantize amps, therefore we can't quantize speakers. Let's just throw away all measurement systems, they don't provide complete and absolute data. Why try to be objective when measurements don't tell us everything? Subjectivity and conjecture is all that is left to us, right?
Sorry, but I use a tool for what it does provide, work to understand its capabilities as well as its limitations, then attempt to extract what useful information it can provide, rather than work in the dark. I don't allow lack of perfection to act as a hindrance. Progress stops otherwise.
Or did I take the intent of your post wrong? Was there something constructive buried in it that I missed?
Dave
FYI. Copied from a paper from a University in Hong Kong.
Change in Sound Pressure Level / Apparent Change in Loudness
3 dB / Just noticeable
5 dB / Clearly noticeable
10 dB / Twice or half as loud
20 dB / 4 times or 1/4 as loud
Curiosity drives me here. Although it obviously changes with age, I am going to seek out what data is available for the FR for the human ear. Also - given room effects on sound I am interested to see just how critical a ruler-flat FR is. Watch this space.
Change in Sound Pressure Level / Apparent Change in Loudness
3 dB / Just noticeable
5 dB / Clearly noticeable
10 dB / Twice or half as loud
20 dB / 4 times or 1/4 as loud
Curiosity drives me here. Although it obviously changes with age, I am going to seek out what data is available for the FR for the human ear. Also - given room effects on sound I am interested to see just how critical a ruler-flat FR is. Watch this space.
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