Articles, Reviews and Measurements of Audio Products (As an Amazon Associate I earn from qualifying purchases)

Revel C52 Speaker Review and Measurements

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This is a review and detailed measurements of the Revel C52 center, three-way speaker. I purchased it years ago for my theater. It comes in a gorgeous maple finish which Harman was discontinuing so I got them for a song. :) It costs US $2,499. It has been on the market for well over ten years, if not fifteen.

My photo booth is too small for the speaker. So here is a quick shot of it as it sits in the Klippel NFS measurement system in our messy garage:
Revel C52 Center Speaker 3-way Review.jpg

It is quite heavy for its size and took effort to lift it to put on the platform. This is a cell phone picture and is a shame you can't see the quality of the finish.

Here is the back side:

Revel C52 Center Speaker 3-way Back Panel Connectors Review.jpg

Those bus bars connecting the tweeter to woofer/mid-range section are so shiny and high quality you want to wear them as jewelry! I kid you not.

You can see the test conditions with "stand mounted" selected and tweeter level set to 0 dB...

Minidsp U-DIO8 USB to AES Converter Review

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This is a review and detailed measurements of the minidsp U-DIO8 8-channel USB to and from AES/EBU digital converter. It is kindly sent in by a member. The U-DIO8 costs US $325 from the company. It is a very cool device in that it lets you stream 8 channels of audio to multiple independent devices. Or capture data form them in reverse. There is also a S/PDIF version.

The box is small which is a bit of a drawback as they used a 25-pin DB connector with a thick dongle to get the inputs and outs:

Minidsp U-DIO8 USB to AES SPDIF Multichannel Converter Jitter Audio Reviews.jpg

The connectors feel a bit cheap and I had a hard time inserting and removing my XLR cables from them. Not a big deal though in operation.

You need a 5 volt input adapter which I did not get. So I tested it using my lab power supply.

Digital Audio Measurements
I have been struggling to get good template for measuring digital output devices and I think I have finally found it. I play the J-test signal (12 kHz @ 48 kHz sampling)...

March Audio P502 Stereo Amplifier Measurements

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This is the measurements of the March Audio P502 class D amplifier based on Hypex (?) modules. It was kindly send to me by a member for testing. The P502 costs US $1,075 from the company direct.

This is not a review because the @March Audio is a long time member of the forum and I like to avoid conflict of interest.

The unit comes in attractive aluminum packaging:
March Audio P502 Hypex Stereo Class D Amplifier  Review.jpg

On off control is a touch button which is unusual in power amplifiers.

Here is a shot of the back:

March Audio P502 Hypex Stereo Class D Amplifier  Back Panel Review.jpg

In hard use, the bottom plate gets quite warm. Make sure you have plenty of ventilation from below. A taller set of feet would help with this.

My heavy stress test of frequency versus power caused the unit to shut down momentarily. I did not retry it as I don't want to risk damaging the unit.

Warm Up Test
As is my standard practice now, I warm up and measure distortion and noise until the device...

Kali Audio IN-8 Studio Monitor Review

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This is a review and detailed measurements of the Kali Audio IN-8, 3-way powered studio monitor (speaker). It was kindly purchased new by a member and drop shipped to me. The IN-8 costs US $399 each.

Despite its rather low price, the IN-8 comes in a rather large enclosure and with good visual fit and finish:
KALI AUDIO IN-8 Studio Monitor Powered Speaker Review.jpg

The tweeter is located in the center of the midrange driver ("coaxial").

Here is the back panel connectivity and EQ settings:

KALI AUDIO IN-8 Studio Monitor Powered Speaker Back Panel Connectors Review.jpg

I tested the unit as shipped with all the dip switches low (EQ defeated). For listening tests, I used the RCA input so had to enable that using dip switch 8. Gain control was set to middle (0 dB) as you see. I think the drive level was 0.7 volts through XLR input. I used a microphone position that was a bit farther away from the speaker. To compensate, I had to boost the levels. They were somewhat uncomfortable to listen to from 6 to 7 feet away. I...

Sunfire HRSIW8 DSP Subwoofer Amplifier

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This is a review and detailed measurements of the Sunfire HRSIW8 DSP Subwoofer Class D amplifier. It is on kind loan from a member. The HRSIW8 seems to have come out back in 2012 with its companion in-wall subwoofer. As best as I can tell, the retail price is US $999 but I see it on ebay for much less.

HRSIW8 comes in a compact, 1-U configuration:

Sunfire HRSIW8 Subwoofer DSP Amplifier Audio Review.jpg

It is extremely heavy for its compact size. Hefty relays click on and off when you power the unit. A rotary control changes the volume. Press it and you get into a number of menus. Alas, there is no parametric EQ is available which would be highly useful to get rid of room modes. Instead you have a crossover and different modes for "music," etc. The crossover is fully programmable as far as frequency and roll off steepness. I set the crossover frequency to highest it would go (160 Hz) for testing.

Note that this is a single channel of amplification.

Subwoofer Amplifier Audio...

NHT Pro M-00 Powered Monitor Review

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This is a review and detailed measurements of my NHT Pro M-00 powered studio monitor (speaker). I purchased it probably 15 years ago upon a hugely positive review from stereophile(?). It said some famous recording engineer used to mix a ton of popular albums. I bought the package with the S-00 subwoofer. Each speaker cost $249 and the sub was $500 for a total of $1,000.

Years later, NHT hit hard times and closed shop for a while. Then went online direct. I have not kept track of what they do now. These speakers are no longer available but as part of our effort to build up some "speaker measuring muscle," I thought it would make for a good second review. Be sure to read my first review of JBL 305P Mark ii to understand this data better.

The M-00 is a small but weighs like it is filled with rocks:

NHT M-00 Powered Studio Monitor Speaker Review.jpg

The case is...

Mark Levinson No 360S DAC Review

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This is a review and detailed measurements of my Mark Levinson No. 360S DAC. I purchased it sometime around 1999 when the new high resolution formats had come out (DVD-A and SACD). It has been a solid foundation of countless audio evaluations I have performed near two decades now. The 360S was the hand tuned version of 360. I think that made it cost $2000 more? I forget how much it cost but probably around $7,000. In today's dollars, that would be well over $10,000. So not cheap. Used ones seem to go for as much as US $3,000.

This thing weighs a ton for a DAC and that is the reason I hate you all for asking me to rip it out of my cabinet to test it!

Mark Levinson No 360S DAC Audio Review.jpg

Lots of connectivity was provided but alas, no USB, HDMI, etc.:

Mark Levinson No 360S DAC Back Panel Audio Review.jpg

The brochure talked at length about modular architecture that would allow addition of new input types. Well, no. Nothing of the kind ever arrived. As such, to use it in...

HIDIZS S8 USB-C Headphone Adapter Review

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This is a review and detailed measurements of the HIDIZS S8 USB-C DAC and Headphone Amplifier. It was kindly sent to me by the company. It is a new product and I don't see it broadly advertised. I only found one site selling it for US $129. So quite high for a dongle.

The box is much larger than the unit itself which weighs next to nothing:
Hidizs S8 USB-C DAC and Headphone Amplifier Audio Review.jpg

Three different adapter cables are provided to mate it to USB-C, Apple Lightning and straight-through so should work with any phone.

The up down buttons work well.

I tested the S8 on Windows 10 which recognized it properly (you have to plug-in the headphone first). Alas, the ASIO4ALL interface I use to test audio products with my analyzer truncated 24 bit samples to 16 bit as it sometimes does. For this reason, I had to run a number of tests manually and a few I had to leave out. But I think you will get a good picture of its performance as is.

FYI, the company contacted me after I reviewed...

JBL 305P MKii and Control 1 Pro Monitors Review

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This is a review and detailed measurements of the JBL 305P Mark ii powered studio monitor and Control 1 Pro budget passive monitor. I purchased the 305P Pro Mark ii when it first came out and it currently sells for US $147.50 from Amazon including Prime shipping. This is the price for one so you need to double that for stereo setup. The Control 1 Pro came with my Klippel NFS speaker measurement system. It is only sold through Pro channel and costs US $164 for a pair.

The 305P Mark ii has good heft and feel to it for a budget priced monitor:

JBL 305p MKii Speaker Powered Monitor Review.jpg
Back panel shows the connectivity and configuration:
JBL 305p MKii Speaker Powered Monitor Back Panel Connectors Review.jpg

The Control 1 Pro doesn't feel like junk but not anywhere close to 305P:

JBL Control 1 Pro Monitor Review.jpg

Introduction
This being the first...

Travagans DC Filter Review

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This is a review and detailed measurements of the "travagans tài píng tiān guó DC Filter." It is from a company in Taiwan and the only mention of it is in a couple of facebook posts. A member kindly sent it to me for review. I have no idea how much it costs.

The Travagans filter comes in a poorly made Baltic Birch plywood:

Topping D50s with travagans tài píng tiān guó DC Filter Audio review.jpg

Oddly, there is a voltmeter inside it which shines through the top if you squint enough:


It shows the voltage to two decimal places. I am sure there are people at Apple who are having a heart attack that someone has mastered industrial design and usability better than them! :)

Anyway, the...

ifi DC iPurifier Power Filter Review

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This is a review and detailed measurements of the ifi DC iPurifier DC (power) filter. It is on kind loan from a member. The iPurifier costs US $99. Looks like there is an updated, iPurifier2 now.

The ifPurifier is an inline DC filter. Power goes in, power goes out. I received a set of adapters with it, not sure if these come with it or not. If not, you definitely need it as these barrel connectors come in a few sizes of outside diameter and inside.

The unit itself is a bit chunky so may not mate with some devices:

ifi dc iPurifier DAC Audio Filter Review.jpg

The challenge with these devices is not that they don't do anything. They do. The issue is if that change materializes in sound you hear.

Audio Measurements
For testing I thought we rely on USB power. "Everyone knows" that USB power is "dirty" so surely this is a perfect input to iPurifier to clean up. I used my Topping D50s as the target DAC since it has independent power that can be provided from USB...

Mola Mola Tambaqui DAC and Streamer Review

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This is a review and detailed measurements of the Mola Mola Tambaqui USB DAC and Ethernet streamer. It is on kind loan from a member which is quite special when you consider it costing US $11,500 (£8,999).

As it should be the Tambaqui weights a lot relative to its size with generous use of free-form thick metal enclosure:
Mola Mola Tambaqui USB DAC Streamer Headphone Amplifier Audio Review.jpg

You really feel like you have a high-end audio product until you touch it. The corners and edges are all extremely sharp. Not that you are going to handle it by hand but I always like to see the edges burnished at least, if not rounded.

There is a lot of connectivity as there should be in this price range:
Mola Mola Tambaqui USB DAC Streamer Headphone Amplifier Audio Back Panel Review.jpg

Of special interest is standard Ethernet network streaming with certified Roon endpoint. Shame they don't emphasize this more.

The user interface is unique. Four buttons to select each input with a default volume setting. I must be dumb because I could not find...

Mytek Liberty DAC & Headphone Amp Review

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This is a review and detailed measurements of the Mytek Liberty USB DAC and Headphone Amplifier. It is on kind loan from a member. The Liberty costs US $995.

While the departure from typical aluminum enclosures was nice, I did not care for the very sharp edges of the front bezel:

Mytek Liberty USB Professional DAC Audio Review.jpg

The LED lights dance in ways I could not always figure out. Otherwise you push click to select inputs.

The back panel is what you expect:
Mytek Liberty USB Professional DAC Back Panel Connector Audio Review.jpg

I was disappointed that the RC inputs were not color coded and one could not see the Right or Left writing looking from front above.

I am sure someone will tell me what the external DC jack is doing there when the unit has AC input. I used that for all of my testing.

I installed the drivers for the unit while it was plugged it. It was happy, told me to reboot, only to not have it be recognized by Windows. I disconnected it and then installed again and it worked this...

Announcement: ASR Will Be Measuring Speakers!

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Yes it is true. Audio Science Review will start measuring speakers soon. This category of products is by far the most requested when it comes to future work. Alas, measuring speakers is not the same as electronics. The high-end standard is to use a multimillion dollar anechoic chamber so that the results are room independent. Space can be rented from such a facility but it all adds up and is tedious to shuttle speakers back and forth to the chamber.

Alternatives have been around forever that both reviewers and DIY speaker builders use. These can approximate the speaker performance. Doing so however is quite a lot of work, often requiring measuring speakers outdoors and on tall polls and such. If one were to produce a handful of measurements a year, and could find someone who will do such manual work for little money, it could be done. I am neither. :) There are thousands of models and brands of speakers. No way can we remotely characterize a useful subset of speakers...

SMSL Q5 Pro DAC And Stereo Amplifier Review

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This is a review and detailed measurements of the SMSL Q5 Pro DAC and stereo integrated amplifier. It is on kind loan from a member. The Q5 Pro costs US $140 from Amazon with Prime shipping.

The sample sent to me is "well used:"
SMSL Q5 Pro USB DAC and Stereo Amplifier Review.jpg

If you were a real audiophile, you would think those scratches change the cabinet resonances leading to less black backgrounds, micro detail and PRAT. But since you are not, let's read on. Here is the back panel:

SMSL Q5 Pro USB DAC and Stereo Amplifier Back Panel Connectors Power Supply Review.jpg

The owner sent me two power supplies. The other one outputs 24 volts but since it says on the back the limit is 19, I went with this one. Heaven knows if I blew it up, I could not buy another one and scratch it up the same way this one is! Strangely if I squint, the fuzzy picture on SMSL website shows the other power supply.

As you see, you have both digital and analog inputs. I tested both as you see below.

Amplifier Audio Measurements...

Audio Research 100.2 Power Amplifier Review

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This is a review and detailed measurements of the Audio Research Corporation (ARC) 100.2 stereo power amplifier. It is on kind loan from a member. The 100.2 came out in year 1998 at a cost of US $2,995. It was later raised to US $3,495. If I remember correctly, the owner told me this the last solid state amplifier ARC produces before going to all tube route.

The 100.2 is as solid as a rock:

Audio Research Corporation ARC 100-2 Stereo Power Amplifier Audio Review.jpg

The back panel is as you expect with the exception of (custom?) speaker binding posts:

Audio Research Corporation ARC 100-2 Stereo Power Amplifier Back Panel Audio Review.jpg

In use the 100.2 cooked and cooked good. I measured 45 to 47 degrees C on the heatsinks. The internal temps are likely much higher. I read that it uses unobtanium output MOSFET transistors so if they go, you likely have a giant door stop. :) In use though the 100.2 did not complain one bit and ran through all of my tests.

Strangely when you power the unit down, it takes it a while to do that. What it is...

Audient iD4 Audio Interface Review

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This is a review and detailed measurements of the Audient iD4 Audio Interface (USB DAC and ADC) plus headphone output. It was kindly sent to me by a member. The iD4 costs US $199 including Prime shipping.

The build quality is quite solid:

Audient iD4 Audio Interface USB DAC Headphone Amp Audio Review.jpg

The shell is close to what Schiit uses but thicker gauge. There is a lot of weight in this little package so should be able to stay on the desk without moving due to weight of cabling.

Here is the top view:

Audient iD4 Audio Interface USB DAC Headphone Amp Top View Controls Audio Review.jpg

The rotary encoder/volume control feels good although the adjustments are a bit coarse for my taste. The smaller controls also feel nice.

Back panel shows the paucity of inputs and outputs:
Audient iD4 Audio Interface USB DAC Headphone Amp Back Panel Inputs and Outputs Connectors Aud...jpg

You only have USB for input and Mic for input.

Line out is in the form of 1/4 inch TRS jacks. I have lost my adapters for these mono connections so I was only able to test one channel. These are common on...

M-Audio Air Hub USB DAC & Headphone Amp Review

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This is a review and detailed measurements of the M-Audio Air Hub USB DAC and Headphone amplifier plus a USB hub (and hence the name). It was kindly purchased by a member and drop shipped to me. The Air Hub costs just US $69. So the question is, do we have a bargain jewel on our hand? Let's find out.

From controls point of view, the Aid Hub has a lovely, large volume control on top with excellent feel:

M-Audio Air Hub USB DAC Headphone Amp Audio Review.jpg

Sadly the large knob only controls line out. It has no impact on headphone out which has its own little volume control in the front.

I did not test the USB hub. You have see one, you have seen them all.

Here is the back panel connectivity:
Best Pro Audio Interface 2020 Back panel outputs inputs Review.jpg

There is a beefy 3 amp 5 volt adapter that powers the unit. Sadly, as the measurements showed later, it has nothing to do with the audio subsystem of the Air Hub! It is only there to power the USB-hub. The unit work without the power supply...

Crown XLS2502 Stereo Amplifier Review

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This is a review and detailed measurements of the Crown XLS2502 DriveCore (switching) 2-channel amplifier. It is on kind loan from a member. The XLS 2502 cost US $645 including free shipping from Amazon. It has DSP functionality which I did not test. And is specified to drive 2 ohm load.

From the outside, the XLS2502 is built like a tank:

Crown XLS2502 Drivecore Stereo Pro Amplifier Audio Review.jpg

It is very light of course due to switching topology for the amplifier and power supply. But also very sturdy with plenty of steel to keep its shape.

The two gain controls are notched which gives them a nice feeling but the gain is not matched and is hard to get there using those notches.

Here is the back connectivity:
Crown XLS2502 Drivecore Stereo Pro Amplifier Back Panel Connectors Audio Review.jpg


There is a fan as you see but in normal testing it never came up. During stress testing, it did come on but was pretty quiet compared to what I expected. Mind you, I don't think you want it close to you if it is going to be running.

Alas, the fan...

WM8740+DIR9001 DAC Board Review

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This is a review and detailed measurement of one of the myriad of boards on ebay sporting the WM8740 DAC chip. It was kindly purchased and drop shipped to me. The listing has expired but it seems that it cost US $48.

What you get is well, a bare board:

WM8740+DIR9001 DAC Board ebay Audio Review.jpg

And not a clean one. The PCM 2704 on the bottom right was either reworked on this board or lifted from another product in the past. Other ICs are also dirty which could be indication of used parts or grungy assembly.

Speaking of PCM 2704 that is an all-in-one USB DAC! It is used here only to generate S/PDIF output from USB, leaving its DAC functionality behind. Sad as that alone would have done the job probably as good or better than stringing it to WM8740 DAC chip.

On first try, I could not get the board working. It comes with no manual, instructions or even vendor name/address. I fed it 9 volts, it did not work. I fed it 12 volts, it did not work. Then I realized it says...
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