[lambdastorm]

Hello everyone!

Thank you for the attention you're giving to our headphones!

I see that we weren't quick enough with publishing the specs in detail, so naturally, a lot of guessing is going on. Sorry about that.

Here's an excerpt from the white paper we're preparing right now, that will be published at our new website in a few days;
I hope this will explain a lot of things and why some decisions are made:

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Unique Demands Of True Ribbons as Headphone Drivers

1) True ribbons have very low resistance. Typically from 0.015 to 0.08 Ohms. SR1a ribbon is 0.018 ohms, or practically, a short-circuit.

Impedance matching transformers can be used to transform the ribbon impedance to a higher value, say, 32 Ohms for use with conventional amplifiers. But...

2) Transformers are big and heavy, in other words, you can't wear them on your head. They would have to be on the table, with a 10-foot cable going to the headphones.

3) A cable that would not be too heavy, and acceptably flexible, would not have less than 0.15 Ohms per channel at 10 feet. That means the cable would have at least 10 times the resistance of the ribbon driver itself!

4) While the transformer will convert 0.15 Ohms + 0.018 Ohms into 32 Ohms, and the headphone output will work just fine, there wouldn’t be enough power to compensate for the resistive loss of 10dB or tenfold of power! Only 1/10th of your headphone amp power will be developed at the ribbon, 9/10ths will just heat up the cable.

5) That is a 10dB loss of volume, so we can forget using the headphone outputs on CD and DVD players, computers, iPods...whatever! Simply, not enough juice!

6) If we try to compensate by increasing the ribbon efficiency, it would require 3 times stronger magnetic induction at the ribbon, which is about tenfold in weight increase to about a pound on each ear!

7) So, do you prefer wearing 2 pounds of transformers or 2 pounds magnets on your head? Well, neither, preferably! Or, how about using 2 pounds of cabling that will have no significant resistive loss? That, especially, is out of the question!

8) Just the 3uH inductance of a normal 10-foot cable will destroy the highs completely when terminated by 0.018 Ohms. Decreasing cable resistance to 0.018 would render all cabling useless, as far as HF response is concerned, as the physically possible inductance is not low enough. Simply, for cabling not to become a problem, cables must be terminated with loads that are greater than 2-3 Ohms.

The best way to drive True-Ribbon Earfield™ Monitor

Clearly, there are no good ways to solve a true-ribbon drive problem with headphone outputs or even dedicated, and more powerful, headphone amplifiers. Current requirement and low resistance demand different approach.

We could have gone with a solution to introduce a very specific amplifier that will drive the headphones, similarly to how electrostatic headphones need their own dedicated amplifiers, but we wanted much more popular and cost-effective solution.

Fortunately, the solution offers itself. Since there’s already a 10:1 (or higher) ratio of cable to ribbon resistance, this means that the ribbon will not be controlled by amplifier damping. That was clear from the beginning of designing our headphones, so the ribbon excursion and damping control was done by passive means, using the aforementioned small amounts of acoustical resistance.

So, since the amplifier damping factor plays no role and if the cables need to be terminated with more than 2 Ohms, then we can use a resistor of any convenient value that is connected in series to the headphones and their cable. As far as the ribbon is concerned, this will become a current-source operation mode.

This type of drive will greatly attenuate the power that is developed across the ribbon. Let's see what the specs say:

Ribbon resistance: 0.018 Ohms

Sensitivity: 85 dB / 1 mW

Power handling with bass-heavy tracks: 450 mW RMS

Max SPL at 450 mW RMS(limited by ribbon excursion at LF): 111 dB


To develop 450 mW of power at 0.018 Ohms load, we need 5 Amps RMS.

Loudspeaker amplifiers can easily deliver 5 AmpsRMS current.

A good example is a 100W / 8 Ohm (200 W / 4 Ohms) amp that is loaded by 5.6 Ohms. At that load, it will deliver 140W RMS and the Current will be 5 Amps RMS. There are many amplifiers like that out there.

In the end, in musical peaks, we are burning 140 Watts at the resistor, just to properly load the amplifier, while developing only 0.45 Watts at the headphones. That is not an unfortunate circumstance. As the old adage goes: “all systems approach perfection when their efficiency approaches zero”. In reality, there truly is a benefit to this; resistive loading will bring the best out of the amplifier's sound capabilities and SR1a will allow it to be easily heard.

With this approach, all we need now is a 100W loudspeaker amp that is connected to a 5.6 Ohms resistor, that is connected to the true-ribbon headphones...

Amplifier Interface unit

Supplied with SR1a headphones is an Amplifier Interface unit.

It contains an array of small, large value resistors, which are paralleled in enough numbers to achieve 5.6 ohms of combined resistance and 140W of power dissipation with moderate temperature increase.

Also, it contains a passive de-emphasize circuit that corrects for line-source/open baffle rising response.

Together with the cable and headphones, the amplifier load will be ~6 Ohms.

The amplifier connects to binding posts / banana plugs at the back, and at the front, the SR1a cable plugs in to a male 4-pin XLR connector. The connector gender is chosen to prevent the possibility of plugging SR1a into a conventional headphones amplifier and effectively short it, causing damage to both the amp and the headphones.

The Amplifier Interface unit is air-cooled, so it should be kept on top and not covered.
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All the best,

Alex
RAAL-requisite

Thanks a lot for the explanation Alex. A few questions:

1. 85db/mw is with the impedance box attached right? From what Danny told me, for the same power the headphone should get at least 20dB louder with without the impedance box.

2. What's the F0 of these drivers? And since they don't need any enclosure, what's the lowest register they can go in an open air environment under +/-3dB threshold?

 

[Aleksandar R.]

You’re most welcome, Lambdastorm!

1) The driver itself has 85dB/mW. That’s “raw” sensitivity and it holds true for with or without the box attached, but...

...In practice, only the specs with the Amp Interface box actually matter, as we can’t drive this thing directly as it wants to kill amps.
It turns out that the raw sensitivity of the driver is just a fun-fact, a curiosity, that has no usable value.

Anyhow, after we connect the cables and the resistor (Amp Interface box) that loads the amp, we get this:

Amplifier loading: 6 Ohms
Sensitivity: 91dB / 1W
Max SPL: 111 dB (excursion limited, reached with 100W/8ohms amp)

Basically, the usual rating for headphones that uses dB/mW, goes out of the window. Now, with the kind of power we’re using, we’re in speakers realm and it is practical to use dB/W.

2) The resonant frequency is ~36 Hz. Initialy, we set it to 40 Hz, but it settles at ~36 after a little use. The response goes lower than that, so the frequency range is 33 Hz – 30 kHz.

 

[lambdastorm]

You’re most welcome, Lambdastorm!

1) The driver itself has 85dB/mW. That’s “raw” sensitivity and it holds true for with or without the box attached, but...

...In practice, only the specs with the Amp Interface box actually matter, as we can’t drive this thing directly as it wants to kill amps.
It turns out that the raw sensitivity of the driver is just a fun-fact, a curiosity, that has no usable value.

Anyhow, after we connect the cables and the resistor (Amp Interface box) that loads the amp, we get this:

Amplifier loading: 6 Ohms
Sensitivity: 91dB / 1W
Max SPL: 111 dB (excursion limited, reached with 100W/8ohms amp)

Basically, the usual rating for headphones that uses dB/mW, goes out of the window. Now, with the kind of power we’re using, we’re in speakers realm and it is practical to use dB/W.

2) The resonant frequency is ~36 Hz. Initialy, we set it to 40 Hz, but it settles at ~36 after a little use. The response goes lower than that, so the frequency range is 33 Hz – 30 kHz.

Man, I get a sense that burn-in might be real with these headphones. If loosening up the drivers can make them go a few octaves lower, I'll probably have them on 24/7

 

[Zhanming057]

I just pulled the trigger on a Spectral DMA150s2 and a DMC30SS that's going to be used mostly for driving the SR1A. General synergy on Spectral amps is actually better with the Mysphere 3.2, but the Raal's are an absolute blast when paired with Spectral setups for electronic music. If you are heavily into electronic music and looking at TOTL cans you need to experience this pairing. I thought the Spectral was fast with the Susvara and faster with the 1266 phi's, and the Raal just takes the response speed and dynamics into a completely different realm. It's too fast for anything other than synthesized music on these cheaper Spectral setups, though. Something like the DMA240 or DMA400 in monoblocks, the presentation is more composed and the midrange deficiencies mostly go away.

One thing about the SR1A is that it's extremely source revealing. The reward for good recordings and good files is high but if you put poor files through them, both in terms of bitrate and processing, you will be punished. In this regard, the Mysphere 3.2's do a great job of being tolerant toward defects in the production chain while not taking away from the resolution, everything is kind of good but the "wow" factor is a bit diminished. The SR1A's make you marvel at good recordings and irritated by bad ones.

Technical accomplishments not withstanding, the heightened clarity is a real issue if you listen to stuff produced by small-time bands (e.g. my friends) or remixes that have questionable production value. Something to keep in mind if you want to use the SR1A without a second, less discerning pair of cans.

 

[wuwhere]

I just pulled the trigger on a Spectral DMA150s2 and a DMC30SS that's going to be used mostly for driving the SR1A. General synergy on Spectral amps is actually better with the Mysphere 3.2, but the Raal's are an absolute blast when paired with Spectral setups for electronic music. If you are heavily into electronic music and looking at TOTL cans you need to experience this pairing. I thought the Spectral was fast with the Susvara and faster with the 1266 phi's, and the Raal just takes the response speed and dynamics into a completely different realm. It's too fast for anything other than synthesized music on these cheaper Spectral setups, though. Something like the DMA240 or DMA400 in monoblocks, the presentation is more composed and the midrange deficiencies mostly go away.

One thing about the SR1A is that it's extremely source revealing. The reward for good recordings and good files is high but if you put poor files through them, both in terms of bitrate and processing, you will be punished. In this regard, the Mysphere 3.2's do a great job of being tolerant toward defects in the production chain while not taking away from the resolution, everything is kind of good but the "wow" factor is a bit diminished. The SR1A's make you marvel at good recordings and irritated by bad ones.

Technical accomplishments not withstanding, the heightened clarity is a real issue if you listen to stuff produced by small-time bands (e.g. my friends) or remixes that have questionable production value. Something to keep in mind if you want to use the SR1A without a second, less discerning pair of cans.

Congrats, Spectral amps are nice.

 

[Lord Rexter]

I just pulled the trigger on a Spectral DMA150s2 and a DMC30SS that's going to be used mostly for driving the SR1A. General synergy on Spectral amps is actually better with the Mysphere 3.2, but the Raal's are an absolute blast when paired with Spectral setups for electronic music. If you are heavily into electronic music and looking at TOTL cans you need to experience this pairing. I thought the Spectral was fast with the Susvara and faster with the 1266 phi's, and the Raal just takes the response speed and dynamics into a completely different realm. It's too fast for anything other than synthesized music on these cheaper Spectral setups, though. Something like the DMA240 or DMA400 in monoblocks, the presentation is more composed and the midrange deficiencies mostly go away.

One thing about the SR1A is that it's extremely source revealing. The reward for good recordings and good files is high but if you put poor files through them, both in terms of bitrate and processing, you will be punished. In this regard, the Mysphere 3.2's do a great job of being tolerant toward defects in the production chain while not taking away from the resolution, everything is kind of good but the "wow" factor is a bit diminished. The SR1A's make you marvel at good recordings and irritated by bad ones.

Technical accomplishments not withstanding, the heightened clarity is a real issue if you listen to stuff produced by small-time bands (e.g. my friends) or remixes that have questionable production value. Something to keep in mind if you want to use the SR1A without a second, less discerning pair of cans.

Congrats, happy for you. Looks like you are living the dream.

 

[Zhanming057]

Congrats, happy for you. Looks like you are living the dream.

Thanks A quick plug for Goodwin's High End, who was kind enough to set up Spectral systems a couple times for me to demo and worked out a deal with me for the preamp. They have lots of cool stuff and if you're passing through the greater Boston area, I would highly recommend a visit to their showroom.

 

[Lord Rexter]

Thanks A quick plug for Goodwin's High End, who was kind enough to set up Spectral systems a couple times for me to demo and worked out a deal with me for the preamp. They have lots of cool stuff and if you're passing through the greater Boston area, I would highly recommend a visit to their showroom.

Thank you so much for the details as always, will plan on it.
Someday I'll get the chance to visit Goodwin's store fingers crossed

 

[Zhanming057]

Another day, another system for the SR1A Waiting on my production version for the big group photo.

On the trip to pick up the preamp I had a chance to try the SR1A with a few "cheap" systems. The cheapest 100w+ integrated at the store is the NAD C368 (MSRP $900, street price $700-ish). The build-in DAC on the C368 is awful and borderline unusable (or it could have been broken, it was seriously that bad). However, moving to a Berkeley Alpha DAC series 2 resulted in a surprisingly listenable system. The pairing compared not unfavorably in resolution and has superior dynamics to driving the Abyss 1266 phi's through a WA7 or nx03 with a similarly strong DAC. A sample size of one is not quite representative but I would expect the SR1A to be very listenable on most power amps in this price range.

The Hegel H190 is a much more expensive unit, but incorporates a DAC that seems to punch at or above its weight with a light, clean and smooth signature, if a tiny bit lean and indecisive compared to stronger stand-alone power amps. The headphone jack is actually driven by the same circuitry as the taps and does fairly well with both the Ether C Flow and LCD3. The SR1A is pretty good on this amp - transparent, clean, with pretty good resolution for the price of the system. If you're looking for a simple, no-fuss solution for the SR1A that also works with normal headphones, the H190 seems like a solid value proposition.

The Hegel Rost shares the H190's signature but has less grunt. On only 75 watts of output at 8 ohms you can feel that the SR1A is struggling a little with bass extension, although loudness was not an issue for me. For the price difference I think that the H190 is clearly the better option, but I wouldn't mind using the Rost with the SR1A's on a day-to-day basis.

Having spent time with the SR1A's on the Spectral setup, my views on the SR1A's midrange have become a bit more nuanced. Conventional wisdom on headphone midrange performance values clarity of imaging and "lushness" which is associated with slightly warmer tuning. Even if midrange frequencies are not emphasized, the slower response speed of dynamic and planar drivers is what we are generally comfortable with as headphone enthusiasts. And the fact that response speed slows with lower frequencies helps with perceived clarity of vocals relative to bass outside the vocal range.

The SR1A's are not part of that comfort zone. Is a neutral, accurate, hyper-fast, and almost too revealing midrange worse than a slower, thicker, lush, more "emotional" midrange? If you're someone who likes to pair headphones with 300b amps and enjoy that kind of euphoric, darker vocal signature, the SR1A on a strong solid state amp is the absolute opposite of that signature, and you probably won't find the pairing pleasing. For someone more receptive toward a neutral signature and leaner imaging, I do think that the SR1A's have the capacity to be a vocal powerhouse, especially with extraordinary well-mastered files.

Assuming that everything is being driven exceedingly well, the Mysphere 3.2 is still my choice for the strongest midrange imaging and doesn't trade off much resolution against the SR1A's on any system. The Abyss 1266's midrange is arguably a tiny bit better in imaging, thicker and more full-bodied but isn't quite as revealing as the SR1A. And while the LCD4 is the least resolving, thickest and most "lush" of the bunch, I don't think that resolution or imaging is a substantive concern with any of these headphones, if you can drive them to their full potential.

 

[anach]

Thanks for sharing your impressions! Is SR1A your preference for electronic music?

 

[Zhanming057]

Thanks for sharing your impressions! Is SR1A your preference for electronic music?

They do perform particular well for electronic music because of the superior speed and bass quality. The fast and punchy Spectral amps works particularly well for the genre, but you will notice how fast the ribbon drivers are with just about any amp.

 

[Thaudiophile]

How does it fair in technicalities compared to Utopia and Stax 007/009?

 

[Zhanming057]

How does it fair in technicalities compared to Utopia and Stax 007/009?

I have owned the Utopia and it's not quite as good in terms of speed, soundstage, resolution or dynamics as the SR1A, if you can afford a sufficiently good power amp. As I see it the Utopia as a design that allows for some drivability at the cost of not being at the very cutting edge of performance. They sound fine out of strong portable amps (e.g. Woo WA8) which can't quite be said for something like the LCD4. In terms of the whole system I like the Utopia's on the Leben CS600 and the Woo WA5, but neither pairing could compete on technical performance with the SR1A out of something like the Octave V110SE. The big difference is that the Utopia is very intimate and has a higher level of density, while the SR1A is completely open with lower density throughout the frequency range.

I did a side-by-side with the SR1A and a few 009 setups. The 009+ Mjolnir Audio KGHSSV Carbon has exceedingly good upper-midrange imaging and lot of detail. However, the SR1A holds its own on detail and treble speed and absolutely pounds the 009 system into the dirt on bass extension and bass quality. I have not tried the HE1 but I have listened to both versions of the Shangri-La and the HE90, and I am mostly convinced that it's not possible to achieve the SR1A and Abyss 1266 phi's level of bass extension in an electrostatic system: the drivers can't deliver enough energy or deliver it fast enough at those frequencies. I can see someone preferring the 009's if they are extremely bass-sensitive or want something more intimate and "closed-in", though.

 

[Articnoise]

Interesting headphone. Is there a place where I can listen to it in Sweden, Rom or Brussels?

 

[PeteSTRADAMUS]

Hello everyone!

Thank you for the attention you're giving to our headphones!

I see that we weren't quick enough with publishing the specs in detail, so naturally, a lot of guessing is going on. Sorry about that.

Here's an excerpt from the white paper we're preparing right now, that will be published at our new website in a few days;
I hope this will explain a lot of things and why some decisions are made:

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Unique Demands Of True Ribbons as Headphone Drivers

1) True ribbons have very low resistance. Typically from 0.015 to 0.08 Ohms. SR1a ribbon is 0.018 ohms, or practically, a short-circuit.

Impedance matching transformers can be used to transform the ribbon impedance to a higher value, say, 32 Ohms for use with conventional amplifiers. But...

2) Transformers are big and heavy, in other words, you can't wear them on your head. They would have to be on the table, with a 10-foot cable going to the headphones.

3) A cable that would not be too heavy, and acceptably flexible, would not have less than 0.15 Ohms per channel at 10 feet. That means the cable would have at least 10 times the resistance of the ribbon driver itself!

4) While the transformer will convert 0.15 Ohms + 0.018 Ohms into 32 Ohms, and the headphone output will work just fine, there wouldn’t be enough power to compensate for the resistive loss of 10dB or tenfold of power! Only 1/10th of your headphone amp power will be developed at the ribbon, 9/10ths will just heat up the cable.

5) That is a 10dB loss of volume, so we can forget using the headphone outputs on CD and DVD players, computers, iPods...whatever! Simply, not enough juice!

6) If we try to compensate by increasing the ribbon efficiency, it would require 3 times stronger magnetic induction at the ribbon, which is about tenfold in weight increase to about a pound on each ear!

7) So, do you prefer wearing 2 pounds of transformers or 2 pounds magnets on your head? Well, neither, preferably! Or, how about using 2 pounds of cabling that will have no significant resistive loss? That, especially, is out of the question!

8) Just the 3uH inductance of a normal 10-foot cable will destroy the highs completely when terminated by 0.018 Ohms. Decreasing cable resistance to 0.018 would render all cabling useless, as far as HF response is concerned, as the physically possible inductance is not low enough. Simply, for cabling not to become a problem, cables must be terminated with loads that are greater than 2-3 Ohms.

The best way to drive True-Ribbon Earfield™ Monitor

Clearly, there are no good ways to solve a true-ribbon drive problem with headphone outputs or even dedicated, and more powerful, headphone amplifiers. Current requirement and low resistance demand different approach.

We could have gone with a solution to introduce a very specific amplifier that will drive the headphones, similarly to how electrostatic headphones need their own dedicated amplifiers, but we wanted much more popular and cost-effective solution.

Fortunately, the solution offers itself. Since there’s already a 10:1 (or higher) ratio of cable to ribbon resistance, this means that the ribbon will not be controlled by amplifier damping. That was clear from the beginning of designing our headphones, so the ribbon excursion and damping control was done by passive means, using the aforementioned small amounts of acoustical resistance.

So, since the amplifier damping factor plays no role and if the cables need to be terminated with more than 2 Ohms, then we can use a resistor of any convenient value that is connected in series to the headphones and their cable. As far as the ribbon is concerned, this will become a current-source operation mode.

This type of drive will greatly attenuate the power that is developed across the ribbon. Let's see what the specs say:

Ribbon resistance: 0.018 Ohms

Sensitivity: 85 dB / 1 mW

Power handling with bass-heavy tracks: 450 mW RMS

Max SPL at 450 mW RMS(limited by ribbon excursion at LF): 111 dB


To develop 450 mW of power at 0.018 Ohms load, we need 5 Amps RMS.

Loudspeaker amplifiers can easily deliver 5 AmpsRMS current.

A good example is a 100W / 8 Ohm (200 W / 4 Ohms) amp that is loaded by 5.6 Ohms. At that load, it will deliver 140W RMS and the Current will be 5 Amps RMS. There are many amplifiers like that out there.

In the end, in musical peaks, we are burning 140 Watts at the resistor, just to properly load the amplifier, while developing only 0.45 Watts at the headphones. That is not an unfortunate circumstance. As the old adage goes: “all systems approach perfection when their efficiency approaches zero”. In reality, there truly is a benefit to this; resistive loading will bring the best out of the amplifier's sound capabilities and SR1a will allow it to be easily heard.

With this approach, all we need now is a 100W loudspeaker amp that is connected to a 5.6 Ohms resistor, that is connected to the true-ribbon headphones...

Amplifier Interface unit

Supplied with SR1a headphones is an Amplifier Interface unit.

It contains an array of small, large value resistors, which are paralleled in enough numbers to achieve 5.6 ohms of combined resistance and 140W of power dissipation with moderate temperature increase.

Also, it contains a passive de-emphasize circuit that corrects for line-source/open baffle rising response.

Together with the cable and headphones, the amplifier load will be ~6 Ohms.

The amplifier connects to binding posts / banana plugs at the back, and at the front, the SR1a cable plugs in to a male 4-pin XLR connector. The connector gender is chosen to prevent the possibility of plugging SR1a into a conventional headphones amplifier and effectively short it, causing damage to both the amp and the headphones.

The Amplifier Interface unit is air-cooled, so it should be kept on top and not covered.
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All the best,

Alex
RAAL-requisite

Will this headphone make it to CANJAM NYC next month?