Articles, Reviews and Measurements of Audio Products

This is a review, listening tests, equalization and detailed measurements of the ZMF Caldera planar magnetic headphone. It is on kind loan from a member and costs US $3,500.

The Caldera is absolutely gorgeous to look at. It is lightweight and with its large cup, very comfortable to wear. Will have to find out from the owner which set of pads it came with.
EDIT: owner let me know that it has stock lambskin perforated pads.

The large cups allowed almost instant fit on my GRAS 45CA headphone measurement rig. I am always happy when that happens.

ZMF Caldera Headphone Measurement
As usual we start with the headphone frequency response measurement and comparison with our target:

OK, I get the flattish bass response but what is up with the three troughs...

This is a review and detailed measurements of the Sound Devices MixPre-3 II multichannel recorder and audio interface with headphone output. It is on kind loan from a member and costs US $895.

It is a cute, compact and rigid recorder. Gain control for Channel 2 has a stiffer feel which I imagine is designed to let you find it in the dark by feel. The LCD on the right is bright and touch sensitive. It is a bit small for comfortable manipulation but can be done. The user interface is a bit odd in that there is no scrolling and you have to learn to click on "..." to go to the next page. There are a myriad of inputs and a few outputs:



I dread testing this class of device as it takes hours to figure out how to do even simple things. The MixPre-3 was no exception. I installed its ASIO driver but it would keep complaining that it was not seeing it. Windows wouldn't recognize it either. Eventually found a...

Klark Teknik Air Link DW20T/DW20R Quick Review and Measurements

This is a quick review of the Klark Teknik Airlink DW20T/DW20R. This was purchased by me for wireless subwoofer use although it is intended for full range use. The unique feature of this system is that it has XLR balanced in/outputs. The combo runs about $200.


The transmitter is rated at handling up to 10 dBU (2.45V rms) and the receiver is rated at producing up to 15 dBU (4.36V rms). However this is at an advertised performance of 0.1% THD+N (60 dB SINAD)!

Official Specifications
Frequency response 20 Hz to 20 kHz (±1 dB)
THD + N (distortion) 0.1% @ 1 kHz
Signal-to-noise ratio >90 dB
Transmission frequency 2.406 - 2.475...

This is a review and measurements of the ROLLS HV6 passive volume control. It was kindly sent to me by a member and is discontinued. It cost $65 when it was sold.

The box is quite solid and the volume has a nice, fluid feel to it. Note that the XLR input is stereo and not for balanced connections.

ROLLS HV6 Headphone Volume Control Measurements
Let's feed the HV6 4 volts and see what it outputs into high impedance at max volume:

While there is some loss, noise and performance are essentially as good as the source (the audio analyzer). I adjusted the volume down and performance remained proportional.

As noted, input impedance is constant at around 520 ohm. Output impedance changes from that value down to 5 ohm. That obviously interacts with the impedance of the headphone. And that...

This is a review and detailed measurements of the Aiyima A07 Max stereo class D amplifier. It was sent to me by the company and sells for (I think) $85 with the included power supply:

I like the little design touches and the much heavier enclosure (made out of steel?). I really appreciate the larger and staggered speaker binding terminals:


As you see, the power supply is rated at 36 volts @ 6 amps. It has no branding though so not sure about the safety marks. There are vent holes underneath and during the testing, the case stayed quite cool.

Let's see how it measures. If you are unfamiliar with what is about to follow, please watch my video tutorial:

Aiyima A07 Max Measurements
As usual we start with our dashboard:
[ATTACH type="full" alt="AIYIMA A07 MAX stereo amplifier...

The Genelec 1031A is a classic model, still frequently seen in professional studios.

Frequency Response


The speaker has a broad and subtle V-shaped sound character around the mid-range, dipping by about 1-2dB. In some cases, the high frequencies might feel slightly bright. The low-end limit is around 38.3Hz at -6dB, with a slope of -46dB/oct. Overall, it impresses with its very smooth frequency response.

Nearfield Measurements



Directivity



Compared to some of the best modern products, the 1031A's control of directivity around the crossover region is a bit lacking, yet it still boasts overall smooth directivity. Notably, around 15-16kHz, the speaker impressively compensates for the dip in the front with off-axis response. It's unclear if this is an intentional design aspect of...

This is a review and detailed measurements of the discontinued Neil Young PONO "high resolution" player. It is on kind loan from a member. Online prices today range from US $400 to $600 and more!

The player comes in an attractive wooden box with nice accessories such as a pouch to hold the triangular shape of this player. The LCD display is grainy. I did not like that it would time out to just a bland bar of what is playing instead of staying on "now playing" screen. To get that you need to press the "O" button again and then you see your controls to skip and such.

Music transfer was easy using USB connection.

In case you are not familiar with this player, Neil Young started to rant about poor quality of compressed music online and took out his music of the services of that era. And then partnered with Ayre to introduce this player and music service to go with. The key selling...

This is a review and detailed measurements of the SoundArtist clone of BBC LS3/5A 2-way speaker/monitor. It is on kind loan from a member. Sample is in Walnut and he paid $630 for it:

Fit and finish is quite good with no blemishes that I could see. Nice modern terminals are provided in the back:

I got a kick out of that "CE" mark. What exactly did they test?

For those of you who are not familiar with the "LS3/5A" these were monitor speakers designed by BBC in 1960s. Their reputation has spun multiple companies to keep producing them. Some are licensed. This Chinese version is not.

SoundArist LS3/5A Speaker Measurement
As usual we start with our anechoic frequency response measurements:
[ATTACH type="full" alt="SoundArtist LS3 5A BBC Speaker Monitor Clone Frequency...

This is a review, listening tests and detailed measurements of the JDS Labs Atom Amp 2 headphone amplifier. It was sent to me by the company and costs US $129.

The solid metal case makes an instant impression, erasing memories of the plastic case of the previous generation. A white LED surrounds the volume control giving it a nice touch. While 4.4 mm headphone output is provided, note that it is not "balanced" (differential). So it is for convenience, not more power. An input selector lets you choose between RCA and 3.5mm inputs:


Typical of other JDS products, it comes with the AC transformer which gets a bit warm.

JDS Atom Amp 2 Measurements
Let's feed the amp 2 volts and measure 2 volts out into 600 ohm load:
[ATTACH type="full" alt="JDS Labs Atmp Amp 2 Headphone...

This is a review, listening tests and detailed measurements of a vintage Rogers L3/5a monitor implementation licensed from BBC with the same name. It is on kind load from a member. New, it costs US $4895 a pair.

From the outside, there is nothing to distinguish this speaker from cheap bookshelves sold when it was manufactured. Back panel reveals no secrets either:


Owner kindly gave permission to leave the serial number on the picture for those of you who want to trace its lineage. Owner says it was manufactured between 1980 and 1987.

Searching for measurements, there are a few but are either old and crude, or have issues (e.g. stereophile measurements with incorrect bass response). So this test may be the first true measurement of this speaker.

Rogers LS3/5a Speaker Measurement
The grill...