Pros: Astounding Sound Quality, Comfortable, Can be had for cheap, Durable
Cons: Condition varies with such an old headphone, Not portable, Design won't win any fashion awards
Getting Your Stuff
This headphone is the true giant killer if it is obtained with an SRD-6/7 transformer box. Keep in mind that you will need at least 10 watts of power (>15 recommended) from a speaker amp to adequately power these things. Vintage amps are wonderful. If you don't have one, consider getting a TA2021 class-T amplifier which can be had for as little as $40 on Ebay. Amazingly, that combo sounds glorious and doesn't leave one wanting. If you can get the complete setup for under or around $400, you are partaking in one of greatest values that exists in the audio world. It is also a stellar first visit to the world of electrostatic technology.
This review is mostly a value proposition, but it wouldn't be appropriate to leave without at least one subjective account of these headphones with some objective data of course.
They sound magnificent. If you are used to dynamics, these will sound more linear, open, airy, and non-fatiguing than probably anything you have heard. They are not bright headphones, being the least bright out of all Lambdas. They are not dark in the slightest. They are extremely neutral and are fantastic all-rounders that sound great from rock to pop to classical. I would have to say that these sound particularly gorgeous with good classical recordings.
They have a bit of very low bass roll-off, but I hardly ever notice it or find it bothersome. If you listen to dubstep 24-7, these may not be for you, but I don't think you would be looking for Stax anyway. They have a great mid-bass punch that is fun, but mild enough to not muck up the sound. They have a gentle emphasis on the mids that I find beautiful and tends to bring out voices very nicely.
The air on these is amazing. They are very full sounding headphones that are also the last headphones that I would call "congested". I thought the K501 was the champion of an airy sound stage until I heard these. This amount of air and effortlessness can only be created on electrostats.
There are of course other options to be had if you are looking into budget electrostatics. I picked the three that I believe are the most common alternatives. I will try to briefly discuss what I find better and what I find worse about them vs the original SR-Lambda SB (standard bias).
Stax SR-Lambda Professional: This would be the most common alternative. After all, it is the direct successor to the original Lambda. It would follow that it would do some things better.
The Good: It can often be found for the same price or even slightly cheaper than the SB. Availability is usually quite a bit higher. The bass extension is a little better. The professional bias amp or transformer box that is needed with these can be used with any later Stax headphones that you may decide to purchase.
The Bad: The frequency response is a bit more wonky and less linear. You lose that small mid emphasis that is very appealing. The headphone is brighter with an upward tilt that is not existent in the SB version.
Overall: This is a great headphone that can be an even better value than the version that I am reviewing. The improvement in bass extension aside, I found the frequency response to be mostly inferior while adding a brightness that was not previously present. If you intend to keep these for a very long time, I think that waiting for a good value on an SB version would be preferred overall.
Koss ESP-950: This is a more expensive alternative that may be more appealing depending on your musical tastes.
The Good: This headphone is very linear, although not as much as the Lambda SB. It is a bit more laid back and less bright than any Lambdas. There is an emphasis on the lower mids that is more intense than the one on the SB and creates a very full and seductive tone on voices. Transparency is probably a little higher than on the vintage Lambdas, likely because of a much newer design. AMP IS INCLUDED, NO SPENDING MONEY ON AMPLIFICATION!!! Lifetime warranty, no questions asked. Parts replacements are cheap.
The Bad: It is hard to find a good deal. They will sell for $1000 normally, but they can be gotten for $500-$600 on amazon if you are diligent in checking and commit quickly. Not everyone wants to deal with that. Drivers have been known to squeak and drivers have malfunctioned and needed to be sent in for replacement. Amplification upgrades can be difficult.
Overall: It is a phenomenal headphone that is definitely worth it for $500-$600. The sound signature is more full and less airy than any Stax, which may be enough for consideration for some people. It is certainly not the most neutral electrostat, but it is one of the least fatiguing and is great for long listening sessions. The build quality is not quite up to the Stax level, but that lifetime warranty should keep your worries away.
Stax SR-207: This is the brand new "budget" Lambda, if the thought of buying used is distasteful to you. It can be a great value. Buying with a new amp will push these to a more expensive price range, so these are not really that good of a value compared to others. They are around $400 new for just the headphones.
The Good: Basically, they are more technically proficient than the older Lambdas. They are a little more detailed and have better extension. This is because of the newer technology. They also can be gotten brand new. Buying used would save you even more money, though it is difficult to find these used.
The Bad: They are a bit bright. They follow the ongoing trend of Lambdas having an upward tilt in their sound signature, and being susceptible to excessive brightness. The tuning is certainly not as neutral or natural sounding as the Lambda SB. Can be quite expensive with amp.
Overall: I cannot honestly recommend these from a value perspective. If you want a new headphone, I would wait for a deal on a Koss ESP-950 which is a better headphone IMHO. Bought as a system with amp, the cost is around $800. Paired with an SRD-7 Pro, the Koss ESP-950 competes with and beats out this system.
Here I will attempt to explain my reasoning behind the star ratings that I have given the SR-Lambda SB with SRD6/7 combo.
Value: I obtained my combo for $350. No dynamic headphone except perhaps the HD800 can hope to challenge the sound quality and that is more than 4x the cost. Enough said.
Audio Quality: The only real weakness is a slightly lacking bass extension. The tuning however, is near perfect. IMO, this is one of the top two best tuned Lambdas made, and leaves nothing to be desired. Neutrality, musicality, transparency, openness and air. No brightness. This is a sound that you can be content with for a lifetime.
Design: The build is very minimalist and sturdy. It is about 30 years old, and looks and behaves good as new. These older Lambdas supposedly are built even better than the new ones. I will ding it a star for just looking odd. You would not go out with these and your friends may make fun of you, but the less superficial will know that the joke is truly on them when they walk outside with their rapper phones.
Comfort: Quite frankly, these are some of the most comfortable headphones that I have worn. They have very low clamping pressure, but the cloth headband does a stellar job of stabilizing these on my head. Since these are so open, my ears are free to breathe easily. I dinged a half-star because the pleather may cause some skin to sweat if these are worn on a hot summer day. Not a problem to me, but others may differ.
Overall: I find it fitting to end this value review on the overall rating. I heavily contemplated giving this a full five stars. In a perfect world, I would have without hesitation. My half-star ding has nothing to do with the presence or lack of merit within this headphone. Rather, it is the fact that you will be investing on a 30-year old product. No matter how well built that product is, a lot can happen in 30 years. There will always be a little risk when buying a vintage product such as this.
As such, make sure that you ask plenty of questions about the product before you commit to bidding on it. Make sure that there is no room for the seller to short-sell you. Once you bid and win, you are obligated to pay. With enough questions, you make sure that you don't bid on a faulty or under-performing product. Even better if you can buy from someone you know or an enthusiast community such as this. For some reason, Stax vintage headphones seem to be somewhat under the radar on this site (hopefully will change), and the risk is usually much smaller than buying from other bidding sites.
In conclusion, this is a phenomenal value headphone that may finally cure that itch to continue spending on upgrades. At least until you decide to go to the top of the electrostatic world.