TO TWEAK OR NOT TO TWEAK THE STAX 007A? THAT IS THE QUESTION

[spritzer]

I just tried it with the earpads backwards and I can't get the phones to seal so just got out of control bass and a messed up sound signature. The earpads are contoured to follow the shape of your head to I can't see why you could even make them fit without bending the two metal arcs so that you've changed the angle of the drivers.

 

[edstrelow]

It's real pain having to bend the headband just right to get a good seal. I did it when I first got the phones and then when I reveresed the pads and then again when I reset them. That's why at this point I don't want to repeat the tweaking adjustments with the pads reversed. If you can't get a good seal, the phones will sound like crap no matter what the orientation of the pads.

I sometimes wonder if some peoples' head and/or ears are so different that they will never hear phones the same as some other people. It's an issue with phones rather than speaker listening because ears take up the rather small space inside the typical ear cup. The way they fill that space can have a major impact on the various resonances/ standing waves and outer ear reflections.

My point is that there may be real individual differences here that are not just those of personal preference.

 

[Elephas]

Quote:

Originally Posted by edstrelow /img/forum/go_quote.gif The 007A ear pads have a "D" shaped opening. Stax says nothing about correct orientation in its manual, just to adjust to your preference.

Besides the O2Mk1 and O2Mk2, the SR-Omega earpads are also "D" shaped. They are fixed in place and not swivelable <- is that a word?

The thick part of the pad is also at the back, at the straight part of the D.

Quote:

I would agree with that except that the earpad presses on the back of my ears.

The earpads don't touch my ears. My ears are smallish and lie flat against my head, so none of the circumaural earpads touch them. They even fit in the smallish AT L3000 earpads without touching any part of the pad. I find that if my ears touch the earpad, they become sore and uncomfortable. I don't think that circumaural earpads are supposed to touch any part of the ear. Of course, this could be unavoidable with for those with giant elephant ears.

Both the O2Mk1 and O2Mk2 earpads are large and deep enough that I don't think many ears will touch them.

When shifting the housing forward or back, enough so that my ears touch the earpads, the sound is not as good as the centered position.

 

[jfrocke]

How tight are the SR-007A supposed to be on one's head? Is their a good post for beginners on how to properly fit the SR-007A?

 

[spritzer]

They do fit more snugly then the SR-007 Mk1 as the elastic used in the headband is much stronger. Your best bet is to bend the arcs so that the earpieces move a few millimeters outwards at the bottom.

 

[edstrelow]

I finally had my chance to compare the MkI and MkII 007's at the LA CANJAM

http://www.head-fi.org/forums/f113/p...te-art-427266/

both on my own set-up and with better amps and can say I am perfectly happy with the MkII with the spring mod and turning the ear pads. There is very little difference between the two other than a slightly brighter sound which some listeners may even prefer. To be sure, the MkI is a great phone, the unmodified MkII may be fine for many people, but if you do feel a need for some tweaking, look into what has been discussed here and elsewhere.

 

[rsbrsvp]

It seems like the eaarpads are problematic on the mk2. Why not just do the spring mod. and refit the springs into MK1 earpads? Would that not work perfect with less fiddeling with the headband?

In fact- I have a broken MK1. I think I could just take its springs with a MK1 earpad with no modification at all and replace them in the MK2? Shouldn't that work?

 

[spritzer]

That would work but you should expand the ring a bit so that the spring can clamp the sides of the new earpads better. I wouldn't use Mk1 earpads on the Mk2 since they are softer and the extra tension in the headband made them a bit uncomfortable for me.

 

[rsbrsvp]

Great. So sonic wise- is the consensus that with the spring mod- the MK2 sounds like a mix between the MK1 and SR-404 but quite a quite a bit closer to the MK1?

If that is so- it sounds graet for rock- maybe better than the mk1.

 

[spritzer]

Adjusting the spring will move the drivers closer to the ear and thus reduce/eliminate the midrange coloration Stax introduced. I've never done just the spring mod so it may partially seal off the port as well and thus reduce the bass boom and open up the bass a bit but I've never tired it. It's a lot cleaner to just plug the port first and see if you like that sound, then do the spring.

 

[jgazal]

I thought that totally open headphones (not only in the back of the diaphragm, which is called circumaural “open” headphones, but those that are open right in the front of the diaphragm, firing the outer ear) were better, because there is no enclosure to alter the sound waves (AKG K1000, Sony MDR-F1 etc.).

I thought that AKG K1000, Sony MDR-F1 etc. sound similar to open baffle designs, but that type of design tends to cancel bass waves (in phase from the front and the opposite phase coming from the back). I don’t know how AKG dealt with this problem, but Sony MDF-F1 made “acoustic lenses” that are some kind of extension in order to delay the back waves and avoid the wave annulment (more info here: SONY MDR-F1/CD2000/G74LS NATURAL SOUND HEADPHONES FOR SESSION MONITORING/MASTERING/REMOTE LOCATION SOUND CHECK REVIEW).

On the one hand, when I see Stax SR-007A, I wonder if they sound like a bass reflex design. The front diaphragm behaves like a ported/vented enclosure. It might increase bass in its resonance frequency. But that’s half of the story, because that port seems to have immediate access to the open back diaphragm, so it’s like you have a bass reflex design, but instead of hearing right in front the speaker, you are right inside the ported chamber... I don’t know how that should acoustically behave.

On the other hand, when I see SR-007 or SR-007A with the blue tack mod, I wonder if they sound like a sealed/infinite baffle design. That type of design tends to demand more watts from the amplifier because the diaphragm has to compact sealed air. But again that’s half of the story, instead of hearing like you were right in front of a sealed speaker, you are right inside the sealed chamber and aggravate the ear occlusion. I don’t know again how that should acoustically behave.

Altering the ear pads distance might be affecting the resonance frequency in the sealed chamber or bass reflex (depending on the model and mod) formed between the front diaphragm and your ear.

All the enclosures above mentioned have mathematical acoustic modeling, comprehending room interactions, using real time analyzers etc. Here I go with my question. Is there someone who can propose a mathematical model for headphones acoustic? That is no simple task because each outer ear is altering the frequency response in its individual way.

I see only one solution and that is Smyth Realiser. Not only you get right frequency response, but you still win your individual Head Related Transfer Function, which means real stage.

Am I thinking correctly? Is that correct?

Best regards,

Jose Luis

 

[rsbrsvp]

What do you plug the port with- playdoe?

 

[jgazal]

Blu-Tack® - The original re-usable adhesive

 

[spritzer]

I use blutac though it actually is white.

As for the other matter, all dipole transducers suffer from back wave cancellation so they try to make the baffle be as big as possible. With headphones you have the option to seal off the ear completely and thus create a true infinite baffle

 

[edstrelow]

Quote:

Originally Posted by jgazal /img/forum/go_quote.gif I thought that totally open headphones (not only in the back of the diaphragm, which is called circumaural “open” headphones, but those that are open right in the front of the diaphragm, firing the outer ear) were better, because there is no enclosure to alter the sound waves (AKG K1000, Sony MDR-F1 etc.). I thought that AKG K1000, Sony MDR-F1 etc. sound similar to open baffle designs, but that type of design tends to cancel bass waves (in phase from the front and the opposite phase coming from the back). I don’t know how AKG dealt with this problem, but Sony MDF-F1 made “acoustic lenses” that are some kind of extension in order to delay the back waves and avoid the wave annulment (more info here: SONY MDR-F1/CD2000/G74LS NATURAL SOUND HEADPHONES FOR SESSION MONITORING/MASTERING/REMOTE LOCATION SOUND CHECK REVIEW). On the one hand, when I see Stax SR-007A, I wonder if they sound like a bass reflex design. The front diaphragm behaves like a ported/vented enclosure. It might increase bass in its resonance frequency. But that’s half of the story, because that port seems to have immediate access to the open back diaphragm, so it’s like you have a bass reflex design, but instead of hearing right in front the speaker, you are right inside the ported chamber... I don’t know how that should acoustically behave. On the other hand, when I see SR-007 or SR-007A with the blue tack mod, I wonder if they sound like a sealed/infinite baffle design. That type of design tends to demand more watts from the amplifier because the diaphragm has to compact sealed air. But again that’s half of the story, instead of hearing like you were right in front of a sealed speaker, you are right inside the sealed chamber and aggravate the ear occlusion. I don’t know again how that should acoustically behave. Altering the ear pads distance might be affecting the resonance frequency in the sealed chamber or bass reflex (depending on the model and mod) formed between the front diaphragm and your ear. All the enclosures above mentioned have mathematical acoustic modeling, comprehending room interactions, using real time analyzers etc. Here I go with my question. Is there someone who can propose a mathematical model for headphones acoustic? That is no simple task because each outer ear is altering the frequency response in its individual way. I see only one solution and that is Smyth Realiser. Not only you get right frequency response, but you still win your individual Head Related Transfer Function, which means real stage. Am I thinking correctly? Is that correct? Best regards, Jose Luis

007 Mods

I think you are correct that plugging the SR007 port makes this a true infinite baffle. However I didn't notice an obviosu reduction in sound level but I did hear a large bass increase, and in my estimation an excessively large one.

The open port of the 007A does presumably allow some back wave to get into the cup thus affecting bass response.

Modelling

I am not certain that any modelling tells you much about what makes a good heaphone. Certainly a phone which measures a wide and flat frequency response when on the ear, should sound good, but any such measurements I have seem have been more roller coaster than flat. So I think the issue is mostly, what type of badness sounds best or worst?

HTRF's

In my understanding of transfer functions as applied to audio, the main interest is to see how the physical structures of the outer ear modify sound. There are complex reflections from the pinna which presumably change with the lateral and vertical direction if the sound source. So potentially you could establish the stimulus cues which give or assist vertical and lateral sound perception.

In spite of some claims that vertical perception is important in audio, when I was working around acoustics, I don't recall any experimental evidence that vertical sound direction could be perceived with any accuracy.

Even lateral direction is not wonderful, but still enough to give us the pleasures of stereo. I recall reports of front-back reversals, i.e. listeners believing that sources in the midline were sometimes erroneously identifed as being ahead when they were behind or vice versa.

Auditory Directional Cues

The prime sources of lateral location information are interaural amplitude differences, i.e. loudness differences between the ears and interaural time differences. In audio recording, the amplitude differences are the main cues, that's all your balance control does is differentially adjust amplitude.

The time differences are mostly messed up by the vagaries of microphone placement, i.e. the mikes are not placed in positions that correspond with the ears. Once you add in multi-miking and studio mixing, the time cues if they are still there, are certainly not what you woud hear naturally.

Of course there is "binaural recording" which places the mikes in the correct ear positions using either a real or a dummy head. These recordings sound much more realistic than most conventional recordings. Probably this is because the 2 mikes record more correctly matched interaural time and amplitude differences. Some aspect of the HTRF time differences may be more accurately recorded, but unless you had microphones exactly in the position of the ear canal they would not pick up the correct HTRF and the playback driver would also need to be in the same location.

This could not be done with regular phones but you could do something with a pair of mikes in the ear canals and IEM drivers in the same location. While I have made a number of binaural recordigs over the years, I have yet to hear
and IEM biaural recording. Of course there would be different HTRF's for different persons, but I would be more than happy to hear such a recording, in effect through another person's ears.