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Headamp Blue Hawaii Special Edition - Page 191

post #2851 of 5674
Quote:
Originally Posted by jcx View Post

well we can compare Tyll's measurements - presumably plotted with 1 kHz normalization - which is where Stax specs the sensitivity - with only 1 dB difference we hardly need to keep track of the offset of the graphs

 

http://www.innerfidelity.com/images/StaxSR007SZ31576.pdf

http://www.innerfidelity.com/images/StaxSR009.pdf

 

the 007 does look like it could sound a few more dB lower than the 009 - while nearly matching at 1 kHz (from Stax published specs) there are some few octave regions of the 007 frequency response that are 3-5 dB lower than the 009

 

while 3 dB is "clearly noticeable" it is often claimed -10 dB difference is required for a subjective "halving" of the loudness

 

also good to read both parts of the Repeatability article for Tyll's measurements http://www.innerfidelity.com/content/expert-tests-innerfidelitys-headphone-measurement-repeatability-and-reproducibility

 

 

Suppose headphone placement and equipment precision is already fully addressed.
 
You want to measure sensitivity. You have several ways to do that. For instance: a) 1khz sine wave load at 100Vrms; 2) white noise load at 100Vrms; 3) first you measure 100Hz sine wave load at 100Vrms, then 200Hz sine wave at 100Vrms and so on until 20.000Khz and then you normalize your 200 dots using the human hearing equal loudness curve (http://hyperphysics.phy-astr.gsu.edu/hbase/sound/eqloud.html#c1).
 
Similarly, you have several ways to measure frequency response. For instance: a) White noise load at an arbitrary power output (say 10Vrms); b) a sweep sine tone from 20Hz to 20.000Khz with 2 seconds length at an arbitrary volume level (I believe that when the amplifier plays the 20hz peak it may not output the same power when the sweep sine achieves the 20khz peak seconds later). Now imagine that you want those measures done with 100Vrms and then with 300Vrms (at this output power level we would probably start to clip the microphone event with phantom power).
What happens with both SR-007 and SR-009 with that several methods?
 
When you have a white noise load, you won’t have much free power. Then the amplifier is a significant variable. Since the SR-009 has a large driving area, a different diaphragm material and probably thin spacers, it won’t demand too much power from the amplifier at the extremes. But if you measure it at higher output levels, you could achieve a region where the SR-009 starts to misbehave (large diaphragm excursions reaching closer to the stators, perhaps phase problems also?). On the other hand, the SR-007 would demand more power from your amplifier (smaller driving area, although it has a not perforated outer section; different diaphragm material; perhaps thicker spacers). With SR-007 you can achieve a region where the amplifier starts to misbehave. If the amplifier have a 10% influence with SR-009, then the SR-007 would have say 20%. And white noise is not the same thing as a real load (music; that sometimes have more HF and other times have more LF content…)
 
When you have a sine sweep the amplifier is a negligible variable. You have all the power available to play a pure sine wave. But then need to be sure that your normalization is correct, which is not an easy task, at least to me (I am not good with mathematics). And that normalization might be the same as a real load (music; that sometimes have more HF and other times have more LF content…).
I am not an engineer, I have not done such measures and that is my limited mental model. I am sure I am failing seeing this sensitivity thing. But when you throw your ideas to scrutiny you want people to say “you are wrong here and you are wrong there”. Of course only people that made those measurements would have the real experience to reach the right conclusions…
So to me, for now, such sensitivity specifications seem not as extensive or precise as we would need.
 
Now imagine that the vast majority of your customers not only are concerned with volume safety levels, but also like classical. If you build an amplifier with huge power outputs you need to pay a lot for freight. Then what would be wiser for Stax to sell? (i) an SRM-T2 with an SR-007 or (ii) a headphone with more sensitivity and amplifiers with lower power output? I think the second option, since not only the total purchase price is lower but also more money spent by costumers stay at your link in the supply chain (less freight and you sell more companion amplifiers).
 
Can your costumers afford both SR-009 and SR-007 and a high power output amplifier? A minority can. Then imagine no SR-009 and a harder to drive multi-layer metal alloy stator with thicker spacers, the traditional diaphragm and the same transparency. Sure it would be better for rock and roll and bass corporeal impact, but then Stax would sell fewer headphones and fewer amplifiers.
 
Is this reasonable?
post #2852 of 5674
The sensitivity response at 1kHz is meaningless, both headphones lead different loudness at the same 1kHz SPL when fed with real music or white or pink noise because of their very different voicing (tonality). It's visible on Tyll's 1kHz normalized SPL plots, it's clearly audible too (I'd also say 3dB louder feel).

Discussed in the stax thread a couple of days back: people need to deliver sensible sensitivity / curve normalization which must include broadband imput signal (pink noise) and some form of loudness estimation or at least human ear sensitivity compensation (A or B-weigthed SPL).
post #2853 of 5674

I did mean to say pink noise. I do not know why I said white noise... And thank you for the input!

post #2854 of 5674

Having a variety of stax at my disposal and using the DA11 as the source and the pre-amp (volume control disabled on the 727), I've noticed that I play the 009 about 3-4 db lower than the 007. Note that this is averaged over the long term of listening that hit the comfort sweet spot. Part of it is the sensitivity but another part is the tonality, as discussed above.

post #2855 of 5674
Quote:Originally Posted by jgazal View Post

 

 

Suppose headphone placement and equipment precision is already fully addressed.
 
<snip>
 
WWSD?
post #2856 of 5674
Quote:
Originally Posted by arnaud View Post

The sensitivity response at 1kHz is meaningless, both headphones lead different loudness at the same 1kHz SPL when fed with real music or white or pink noise because of their very different voicing (tonality). It's visible on Tyll's 1kHz normalized SPL plots, it's clearly audible too (I'd also say 3dB louder feel).

Discussed in the stax thread a couple of days back: people need to deliver sensible sensitivity / curve normalization which must include broadband input signal (pink noise) and some form of loudness estimation or at least human ear sensitivity compensation (A or B-weigthed SPL).

not meaningless - just not conclusive - no "audiophile headphone" can have 10s of dB peaks, notches, much less broad frequency response features within a few octaves of (more importantly below acutally) 1 kHz -- it wasn't chosen as the default sensitivity measurement frequency for no reason at all

 

the refs on loudness measurement in the stax thread are welcome - I missed that discussion - you might notice I did post the full frequency response curves and offer some interpretation rather soon after my 1st post

 

my posts were in response to what looked to me like the unfortunately typically exaggerated claims seen with uncontrolled subjective commentary - of loudness difference between 007 and 009 making it impossible to listen to them with the same drive level amp - 3 dB is not that big


Edited by jcx - 1/9/13 at 10:50pm
post #2857 of 5674
Quote:
Originally Posted by jcx View Post

 

my posts were in response to what looked to me like the unfortunately typically exaggerated claims seen with uncontrolled subjective commentary - of loudness difference between 007 and 009 making it impossible to listen to them with the same drive level amp - 3 dB is not that big

Here we are. Thank you! wink.gif

post #2858 of 5674

I don't know anything about the technical side of audio, so when I see graphs I haven't a clue what I'm looking at or for. However my source has 0dB and +6dB settings [ using XLR only ] which can be switched from one to the other in seconds. Because of that I decided to listen to my 009's driven by my BHSE with the volume knob at 11 o'clock, and to what I can recall, when I heard my 009's along with headfier IanG's 007's with the BHSE and not changing the volume knob, the difference between the 009's and 007's sounded a lot more than 6dB. This makes me feel that while graphs and specs might be a good thing, the only true way to know is to listen.

post #2859 of 5674
Quote:
This makes me feel that while graphs and specs might be a good thing, the only true way to know is to listen.

Well said.

 

In the end, we can only live with our opinions based on what our ears tell us.

This does not mean that we do not need to train our ears - train our ears, not delude out brains.

 

 

 

This post has been edited in response to the next post #2860.


Edited by wink - 1/11/13 at 3:08am
post #2860 of 5674
Quote:
Originally Posted by wink View Post

 

Looks like another facetious post, and then some wonder why some would sooner not visit certain head-fi forums.

post #2861 of 5674

May I know what is lead time for this amp at the moment ? Is a 240V (as opposeed to 230V) model offered ?
 

Regards,

Joe Ling

post #2862 of 5674
Quote:
Originally Posted by joeling View Post

May I know what is lead time for this amp at the moment ? Is a 240V (as opposeed to 230V) model offered ?
 

Regards,

Joe Ling

I placed my order late November early December (I am not sure) and the list for the current batch was about 80% full. So I suppose (Justin will probably make a post here soon and confirm or infirm this) that you would be on a waiting list now in case there are a few cancellations. The current batch is expected sometime this spring.  With regard to you second question, I have not idea! 


Edited by satorarepotenet - 1/10/13 at 2:58pm
post #2863 of 5674
Quote:
Originally Posted by livewire View Post
 
<snip>
 
WWSD?

 

 

You are right. It does not seem easily achievable. I should have written that phrase using other word: "pretend headphone placement...". Or "if headphone placement and equipment precision were fully addressed, we still would have other problems..."


Edited by jgazal - 1/10/13 at 5:34pm
post #2864 of 5674

The back right mullard has started to go so I have 2 matched pairs on standby which I intend to switch out.

Have a dumb question, not very good at phrasing it so hopefully someone can understand what I'm asking..

 

How are the tubes arranged for 2 matched pairs?

A matched pair in front and a matched pair at the back?

Or, matched pairs on either side of the amp; ie, one pair on the left and another on the right?

 

Thanks in advance.

post #2865 of 5674
On either side option. Been doing this with my tube rolling.
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