Articles, Reviews and Measurements of Audio Products
Drop + THX Panda Review (headphone)
This is a review and detailed measurements of the Drop + THX Panda wired and wireless headphone. It was kindly loaned to me by a member and costs US $399 from the company.
While the feel of the pads is nice, I am not sure I got any cuteness inferences from the name "Panda:"
The spring tension is extremely progressive going from little resistance to massive amounts. The soft pads help a lot but I did not like wearing them. They bothered me from start and stayed that way. The small cups and heavy weight of the unit despite its size do not help in this regard. We are at 380 grams with inside cup dimensions of 59x40x20 (Height x Width x Depth).
A removable 3.5 mm cable is provided for wired connectivity. Online measurements and reports indicate the same response wired and wireless so I did all of my testing wired (lossy codecs can change the frequency response).
The measurements you are about to see are made using a...
While the feel of the pads is nice, I am not sure I got any cuteness inferences from the name "Panda:"
The spring tension is extremely progressive going from little resistance to massive amounts. The soft pads help a lot but I did not like wearing them. They bothered me from start and stayed that way. The small cups and heavy weight of the unit despite its size do not help in this regard. We are at 380 grams with inside cup dimensions of 59x40x20 (Height x Width x Depth).
A removable 3.5 mm cable is provided for wired connectivity. Online measurements and reports indicate the same response wired and wireless so I did all of my testing wired (lossy codecs can change the frequency response).
The measurements you are about to see are made using a...
Dayton MK402X Review (Bookshelf Speaker)
This is a review and detailed measurements of the ultra-budget Dayton MK402X bookshelf speaker. It was kindly sent to me by a member and costs US $70 a pair plus $8 shipping on Amazon. Note that this is the revised version of MK402 (hence the letter "X" after its model number).
From the front, MK402X looks to be a more expensive speaker than it is with chamfered edges and such:
The back gives out the budget look though:
Still, not too bad at all for what you are paying here.
Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field")...
From the front, MK402X looks to be a more expensive speaker than it is with chamfered edges and such:
The back gives out the budget look though:
Still, not too bad at all for what you are paying here.
Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field")...
Sennheiser HD600 Review (Headphone)
This is a review and detailed measurements of the Sennheiser HD600 headphone. I purchased this sample new after I visited major labels around year 2000 and noticing this was a reference headphone they used. I handed it to my son Karman who has been using it for years and replacing the worn out pads. He was visiting us (we are all vaccinated) and brought it with him. I had shown him how to make measurements and what you see below are his.
Other than showing some wear, you can't tell the HD600 from HD650:
The measurements you are about to see are made using a standardized Gras 45C. I searched for any and all measurements I could find online. Alas while a number of them are close to mine, none are using the exact fixture...
Other than showing some wear, you can't tell the HD600 from HD650:
The measurements you are about to see are made using a standardized Gras 45C. I searched for any and all measurements I could find online. Alas while a number of them are close to mine, none are using the exact fixture...
Analytical Analysis - Room Gain
-Introduction-
The term 'room gain' is often seen used when the topic of subwoofers and the low frequency sound reproduction comes up. As I see many explanations that are lacking or incorrect, I thought I might try and clear up the topic once and for all.
In all rooms there are so-called modes. A mode consists of a function and a number; more specifically an eigenfunction and and a eigenvalue. The eigenfunction describes the shape of the mode, and the eigenvalue gives us the (angular) frequency for the mode. There are infinitely many modes in any room. They are finely distributed at higher frequencies and we rarely considered room acoustics from a modal perspective at high frequencies. However, at lower frequencies, they show up much more distinctly, and this is what we will investigate here. Rooms come in many shapes and sizes. Here, we will focus on the 'rectangular' room (cuboid, or rectangular prism, is probably more correct, but we all get the...
The term 'room gain' is often seen used when the topic of subwoofers and the low frequency sound reproduction comes up. As I see many explanations that are lacking or incorrect, I thought I might try and clear up the topic once and for all.
In all rooms there are so-called modes. A mode consists of a function and a number; more specifically an eigenfunction and and a eigenvalue. The eigenfunction describes the shape of the mode, and the eigenvalue gives us the (angular) frequency for the mode. There are infinitely many modes in any room. They are finely distributed at higher frequencies and we rarely considered room acoustics from a modal perspective at high frequencies. However, at lower frequencies, they show up much more distinctly, and this is what we will investigate here. Rooms come in many shapes and sizes. Here, we will focus on the 'rectangular' room (cuboid, or rectangular prism, is probably more correct, but we all get the...
Shanling UP4 Review (DAC & BT Headphone Adapter)
This is a review and detailed measurements of the Shanling UP4 DAC and Bluetooth Headphone Amplifier. It is on kind loan from a member and costs US $105 on Amazon including Prime shipping.
This is a very compact unit even though it has battery built-in:
There are two outputs: standard 3.5mm and "balanced" 2.5mm.
There is a nicely implemented volume control which has very fine graduations unlike the stock ones in the operating system.
A single mode button on top is heavily "overloaded" as far as functionality serving as both gain control and filter settings. I had no luck changing the gain when I used the unit on Windows. Switching them made no difference. Could be operator error although there is a firmware upgrade that deals with this on Android.
Some really nice specs are provided by the company (e.g. SNR of 120 dB or something like it) so let's see how it measures.
Shanling UP4 Measurements
As is common with many dongles, I could...
This is a very compact unit even though it has battery built-in:
There are two outputs: standard 3.5mm and "balanced" 2.5mm.
There is a nicely implemented volume control which has very fine graduations unlike the stock ones in the operating system.
A single mode button on top is heavily "overloaded" as far as functionality serving as both gain control and filter settings. I had no luck changing the gain when I used the unit on Windows. Switching them made no difference. Could be operator error although there is a firmware upgrade that deals with this on Android.
Some really nice specs are provided by the company (e.g. SNR of 120 dB or something like it) so let's see how it measures.
Shanling UP4 Measurements
As is common with many dongles, I could...
Tascam TH-07 Review (Headphone)
This is a review and detailed measurements of the Tascam TH-07 closed back headphone. It is on kind loan from a member and costs US $75 from Amazon including Prime shipping.
The TH-07 looks very fancy but feels very plasticky and cheap once you hear it:
Comfort was good though. The headphone weighs 300 grams and has a round cup with inside dimensions of 59 mm. The cup depth is 18mm.
The measurements you are about to see are made using a standardized Gras 45C. I searched for any and all measurements I could find online. Alas while a number of them are close to mine, none are using the exact fixture down to coupler and pinna. As you will see, I have confirmed the approximate accuracy of the measurements using Equalization and listening tests. Ultimately headphone measurements are less exact than speakers above a few kilohertz so...
The TH-07 looks very fancy but feels very plasticky and cheap once you hear it:
Comfort was good though. The headphone weighs 300 grams and has a round cup with inside dimensions of 59 mm. The cup depth is 18mm.
The measurements you are about to see are made using a standardized Gras 45C. I searched for any and all measurements I could find online. Alas while a number of them are close to mine, none are using the exact fixture down to coupler and pinna. As you will see, I have confirmed the approximate accuracy of the measurements using Equalization and listening tests. Ultimately headphone measurements are less exact than speakers above a few kilohertz so...
Massdrop x Meze 99 Noir Review (Headphone)
This is a review and detailed measurements of the Massdrop x Meze 99 Noir closed back headphone. It is on kind loan from a member and costs US $200. I understand it is identical to Meze 99 Classic which the company sells for a lot more money.
The 99 Noir has a quirky look that is unique and for me, comfortable:
Dual mono 3.5 mm removable plugs are provided which fit very tightly. They are long and narrow so if you need to replace them, you have to get something that is the same.
The 99 Noir is pretty light headphone at 270 grams. Inside cup dimensions are 65x50x19 (height x weight x depth).
The measurements you are about to see are made using a standardized Gras 45C. I searched for any and all measurements I could find online. Alas while a number of them are close to mine, none are using the exact fixture down to coupler and...
The 99 Noir has a quirky look that is unique and for me, comfortable:
Dual mono 3.5 mm removable plugs are provided which fit very tightly. They are long and narrow so if you need to replace them, you have to get something that is the same.
The 99 Noir is pretty light headphone at 270 grams. Inside cup dimensions are 65x50x19 (height x weight x depth).
The measurements you are about to see are made using a standardized Gras 45C. I searched for any and all measurements I could find online. Alas while a number of them are close to mine, none are using the exact fixture down to coupler and...
AudioQuest Dragonfly Cobalt Review (Portable Headphone Adapter)
This is a review and detailed measurements of the AudioQuest Dragonfly Cobalt portable DAC and headphone amplifier ("dongle"). It is on kind loan from a member and costs US $300.
The Dragonfly Cobalt dates way back to when these dongles came in the form of USB flash Thumb drives:
This makes it easy to connect to desktop and laptop computers (assuming yours has such USB connection) but needs a chunky adapter to connect to USB-C on phones and tablets. While I did not have it, a custom one comes with Cobalt which makes a secure connection.
The dragonfly series comes in a few colors, each with a different performance level. The Cobalt is the top of the line as indicated by sky high price for such a product. An ESS ES9038Q2M DAC chip is used internally as to indicate high performance. We will check for this.
AudioQuest Dragonfly Cobalt Measurements
I was pleased that the Cobalt introduces itself to Windows in a way that I could use my...
The Dragonfly Cobalt dates way back to when these dongles came in the form of USB flash Thumb drives:
This makes it easy to connect to desktop and laptop computers (assuming yours has such USB connection) but needs a chunky adapter to connect to USB-C on phones and tablets. While I did not have it, a custom one comes with Cobalt which makes a secure connection.
The dragonfly series comes in a few colors, each with a different performance level. The Cobalt is the top of the line as indicated by sky high price for such a product. An ESS ES9038Q2M DAC chip is used internally as to indicate high performance. We will check for this.
AudioQuest Dragonfly Cobalt Measurements
I was pleased that the Cobalt introduces itself to Windows in a way that I could use my...
Simulation Analysis - Screws in Waveguide
- Introduction -
Erin (of Erin's Audio Corner) has expressed an interest in knowing the influence of screws in waveguides; if they protude from the waveguide, can the sound be affected? I have investigated this issue using a numerical simulation software. This is not an exhaustive analysis, but more of a fun weekend project.
- Simulation setup -
Software: COMSOL Multiphysics
Method: Finite Element
Geometry: Realistic 1" tweeter geometry, arbitrary waveguide (5 cm radius, 2 cm depth), 4 screws (0.67 cm diameter, protuding 1.2 mm), in baffle
Mesh: Quadratic Lagrangian elements (6 elements per wavelength @20 kHz)
DOFs: ≈ 262,000
Other: The exact same mesh was used for both cases; with and without screws. Calculation time on laptop around 1 hour per case. This is pure acoustics case, so there is no explicit solid mechanics; instead an acceleration is put on the tweeter surface. Exploited quarter symmetry.
- Observations -
The sound pressure level was...
Erin (of Erin's Audio Corner) has expressed an interest in knowing the influence of screws in waveguides; if they protude from the waveguide, can the sound be affected? I have investigated this issue using a numerical simulation software. This is not an exhaustive analysis, but more of a fun weekend project.
- Simulation setup -
Software: COMSOL Multiphysics
Method: Finite Element
Geometry: Realistic 1" tweeter geometry, arbitrary waveguide (5 cm radius, 2 cm depth), 4 screws (0.67 cm diameter, protuding 1.2 mm), in baffle
Mesh: Quadratic Lagrangian elements (6 elements per wavelength @20 kHz)
DOFs: ≈ 262,000
Other: The exact same mesh was used for both cases; with and without screws. Calculation time on laptop around 1 hour per case. This is pure acoustics case, so there is no explicit solid mechanics; instead an acceleration is put on the tweeter surface. Exploited quarter symmetry.
- Observations -
The sound pressure level was...
Bagby Mandolin DIY Speaker Review
This is a review and technical measurements of the (late) Jeff Bagby Mandolin DIY kit as built by our member, @Rick Sykora. Looks like the drivers and crossover for a pair cost US $316.42. Rick will have to advise as to the rest of the cost.
As usual, Rick has built this speaker as a tank, weighing far more than commercial speakers its size:
As expected, there is a port in the back:
Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors...
As usual, Rick has built this speaker as a tank, weighing far more than commercial speakers its size:
As expected, there is a port in the back:
Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors...
Audirect/Hilidac Beam 2SE Review (Portable Headphone Adapter)
This is a review and detailed measurements of the Audirect (or Hilidac) Beam 2SE headphone DAC and amplifier. It was sent to me by the company and costs US $89. It doesn't seem to be available on Amazon.
The enclosure for the Beam 2SE seems to be made out of metal and shiny plastic, giving it a rather high-end look:
There is a USB-C terminal at one end, and 3.5 mm "unbalanced" headphone jack on the other side:
Nice shiny little cables are provided which is a good thing as I could not get any of my other USB-C cables to work reliably. Theirs fits securely and worked fine.
Typical of these dongles, my ASIO interface layer that I need for any audio analyzer to control them truncates to 16 bits causing errors. So for most of the tests I played the test files through my Roon player in exclusive mode which doesn't have this issue. So please pardon fewer than normal tests.
Audirect Beam 2SE Measurements
As usual...
The enclosure for the Beam 2SE seems to be made out of metal and shiny plastic, giving it a rather high-end look:
There is a USB-C terminal at one end, and 3.5 mm "unbalanced" headphone jack on the other side:
Nice shiny little cables are provided which is a good thing as I could not get any of my other USB-C cables to work reliably. Theirs fits securely and worked fine.
Typical of these dongles, my ASIO interface layer that I need for any audio analyzer to control them truncates to 16 bits causing errors. So for most of the tests I played the test files through my Roon player in exclusive mode which doesn't have this issue. So please pardon fewer than normal tests.
Audirect Beam 2SE Measurements
As usual...
Allo Boss2 Review (Stereo Streamer)
This is a review and detailed measurements of the Allo Boss2 Ethernet (and wifi) streamer/player. It was sent to me by the company for testing and costs US $149 by itself. My tested configuration included the Nirvana power supply which brings the cost up to US $209.
I must say, I am very pleased to see Allo upgrade from clear cases of the past to rather attractive aluminum enclosure:
The menus are a bit slow but are worlds better than not having them. A remote control is provided which I did not have to use:
As you can see, a stereo DAC is preinstalled so this is not just a digital streamer but a complete playback device. Combined with the remote, all you need are powered speakers or an amp and passive speakers and you are in business.
An image of DietPi was kindly preinstalled on the unit for me so I was able to instantly recognize and use the Boss2 with...
I must say, I am very pleased to see Allo upgrade from clear cases of the past to rather attractive aluminum enclosure:
The menus are a bit slow but are worlds better than not having them. A remote control is provided which I did not have to use:
As you can see, a stereo DAC is preinstalled so this is not just a digital streamer but a complete playback device. Combined with the remote, all you need are powered speakers or an amp and passive speakers and you are in business.
An image of DietPi was kindly preinstalled on the unit for me so I was able to instantly recognize and use the Boss2 with...
Sivga Phoenix Review (headphone)
This is a review and detailed measurements of the Sivga Phoenix open-back headphone. It was sent to me by the company and costs US $255 on Amazon including Prime shipping.
I must say, this is one attractive looking headphone!
The padding and soft surfaces feel luxurious as well. Reminds me of the inside of an Audi automobile!
I absolutely love the fact that they indicate the channel designation both in large letters inside and on the sides:
On some headphones it literally takes me a minute or two to find the darn designation.
The headphone is also fairly light at just 300 grams. Cups are round as you see with a diameter of 58 mm. The depth is variable and at the shallowest end is 17 mm which is not a lot. If you have your ears poking out, it may touch dust cover.
The measurements you are about to see are made using a...
I must say, this is one attractive looking headphone!
The padding and soft surfaces feel luxurious as well. Reminds me of the inside of an Audi automobile!
I absolutely love the fact that they indicate the channel designation both in large letters inside and on the sides:
On some headphones it literally takes me a minute or two to find the darn designation.
The headphone is also fairly light at just 300 grams. Cups are round as you see with a diameter of 58 mm. The depth is variable and at the shallowest end is 17 mm which is not a lot. If you have your ears poking out, it may touch dust cover.
The measurements you are about to see are made using a...