Review - Tangzu x HBB Xuan NV

About my reviews

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This page is aimed to serve as a reference as to how I review an item and to also clear up any questions that people may have about where the products come from and how I aim to keep my reviews unbiased.

How I get the items and products I review...

I want to get this part out of the way first, so everyone is clear on what I receive for free, whether I get paid for reviews etc.

I have absolutely no issue with disclosing how I receive my products and anyone who has seen (or read) any of my reviews will notice that I am very clear about where they come from.

Let me make it very clear, I have not received any form of cash payment for any of my reviews, written or on YouTube, nor have I ever been influenced by a supplier (brand or store) to write or say anything specific about a product. I have been offered products in exchange for positive reviews, which I have politely declined without reviewing that item, at least from that specific supplier.

But that does not mean I have not received things in exchange for my reviews. There are various companies (brands and stores) that have sent me items free of charge to review, some of these been without the need to return the item, something that I am very clear about in my videos and reviews.

So, basically, the ways I receive products for reviews are as follows...

Sent to me free of charge in exchange for a review: This is under the agreement with the provider that I will publish an honest review from my point of view, if not, don't send it me. I always mention in the reviews how I got the product in this case.

Loaned to me for review: Again, this is under the understanding that I will publish an honest review from my point of view, if not, don't send it me. I always mention in the reviews how I got the product in this case.

Purchased by me with a discount in exchange for a review: Once more, this is under the agreement with the provider that I will publish an honest review from my point of view, if not, forget the discount and I will pay full price. I always mention in the reviews that I received a discount in this case.

Purchased by me at full price: If I do not mention anything in the review about where the item came from, it is because I have purchased the item myself, without any discounts or other "perks". So, if I don't say where an item came from in my reviews, it is because I purchased it myself through a normal retail channel.

If there are any other cases which don't fall under these 4 circumstances, I will mention them in the review.

At the end of the day, if I can't be honest about where an item came from and do my best to be unbiased in my reviews, then I am not interested.
How I put together my reviews...

I try to be as consistent as possible in reviewing items even though is not always possible. I do not review items as a profession, I do this for fun, and therefore I do not have a laboratory and specific set ups that never change, I enjoy listening to music and I also enjoy testing and reviewing items. 
However, as I just said, I do try to be consistent in what I do, allowing my reviews of items to be compared against other items I have also reviewed.
Once I know I am going to review something, I do my best to avoid reading any detailed reviews or looking at measurements. Obviously I can't just forget what I had read before this point but by the time I get around to reviewing it, I have usually forgotten what I read 😁
As an example, here are the usual steps I take before reviewing headphones or IEMs.
1. Receive, open and quick listen
When I first receive a headphone or IEM, I will unpack it and have a quick listen, just to make sure it works as it should. These first listens are usually no more than 5 or 10 minutes.
2. Burn in
I am not going to get into the discussion of whether I agree with burn in or not, this is not the place nor time, but as it doesn't cost me anything, I connect the headphones or IEMs to a secondary system and play them for around 100 to 150 hours (with breaks every 4 hours or so).

3. General Listening
I like to spend at least 5 full days listening to the headphones or IEMs just in general. I usually spend 8 hours per day at my desk which involves me listening to a lot of music from lots of genres, so this is the perfect time to get a feeling for the item. If there is something that I don't like, this is when I change things like tips, pads, add EQ etc.

4. Detailed listening

After having spent time using them for my day to day, I like to take a day to go through my test list of songs and also do any comparisons that I feel are relevant.

During this detailed listening period, I make notes of things that stand out to me, which I reference later in my review. You can find the automatically updated list of my test tracks here: List of test tracks

5. Review

Usually I will sit down, hit record on the camera and talk about what I have found, with quick references to my notes. I will then re-watch the review and then put together the written version in English and Spanish for the blog and other sites.
In the written versions of my reviews, I make any tracks that I mention clickable links. Clicking on the track name gives you the option to open the referenced track in the streaming service of your choice. Please note that not all streaming services use the same copy of the track, therefore, there may be slight variations from one service to another.

NOTE: In the case of units that have been sent to me with a specific time frame I can spend with them, I reduce points 2 and 3 accordingly. Usually items on loan with a maximum time frame (within reason) are part of a tour and the burn in will already have been done by previous users.

Sincerity and personal bias...

Are my reviews sincere? Yes.
Are my reviews unbiased? No.

Now, before you jump to conclusions, I am not purposefully giving opinions that are false, influenced by manufacturers or in exchange for anything, that is not what I mean. My reviews are 100% sincere and honest, as far as my brain lets me be. 

Let me explain. The human brain is a very powerful tool that is capable of making us hear, see, taste, smell and feel things that are really not there. In the case of audio, we are full of expectations that can totally influence our decisions and feelings. For example, something as simple as a headphone looking great can make us automatically expect to like it and our brain will possibly (probably?) search for the positive things more than the negatives. 

I honestly do my best to ignore any possible biases, trying to focus on the good and the bad, but they only way I could be certain would be if I heard something without knowing what it was. If someone unpacked a headphone, placed it on my head and played music without me knowing what headphone it was, then maybe I could aim to be completely unbiased, but even then things like comfort would come into play.

It is absolutely not possible to be 100% free of bias, nor is any reviewer completely free of bias, unless that person is not actually human.

Comparing my reviews against other reviews...

This is something that can not be done, or at least it isn't useful. There are reviewers that hear things differently, reviewers that like different things and there are even reviewers that get paid to like things (yes, what a shock!).

I have certain reviewers that I agree with most of what they say and have similar tastes, but even then, we do not agree 100% of the time. Treat each reviewer as an individual and create your own opinions.
How to interpret my reviews...
My reviews should be interpreted as what they are... an opinion. All I do in my reviews is give you my own opinion of an item.

You may coincide with my opinion, you may not, but you should never take my opinion as an exact reference as to what you are going to experience personally.

My advice to anyone who is looking for guidance is to find reviewers that have reviewed something you know and have a similar opinion to your own. The more you can find things that you have in common with a reviewer (sound preferences, experiences etc.), the more useful that reviewer will be to your quest. Once you think you are interested in a product, watch and/or read as many reviews as possible of the item and get a general feel for it across the board.

Unfortunately, the only person who can guarantee you like or dislike an item is yourself and even then we sometime struggle to decide whether we actually do like it or not.

Equipment I use for reviews...

When testing and reviewing an item, I will use all kinds of combinations of DACs, Amplifiers, Headphones and IEMs to compare. However, in order to try and keep things as constant as possible, I will use the following equipment during the detailed listening tests:

Music Sources

Foobar 2000 - Playing my test tracks in FLAC.
UAPP - Playing my test tracks in FLAC
Tidal - Playing my test tracks in Hifi Quality (not MQA)

(Note: I have updated my test track list in order to provide links to the songs on all available platforms, see List of test tracks.)

Audio System

As I mentioned above, I use all kinds of combinations for general listening, however, using the above files, I do my detailed listening and comparisons of headphones and IEMs on the following systems:

iFi Audio Gryphon - This is what I mainly use for daily and detailed listening of IEMs.

SMSL SU-8 or Hifiman EF400 > Schiit Asgard 3, Feliks Audio Echo MK2 or THX789 - This is what I mainly use for listening to headphones. 

*iFi Audio Gryphon or Earmen Tradutto > Earmen CH-AMP or Hifiman EF400 - This is what I use for detailed listening.

Note: Any other combinations that I use and feel they make a noticeable input on the headphones or IEMs I am testing will be noted in the review.

*Updated as from September 2023


Other Relevant Items

New Bee Foam Tips - These are my tips of choice for IEMs, unless I find them to detract from the sound quality of the IEM or to be uncomfortable with specific IEMs. If I do not mention other tips in the review, these are the tips that have been used.

Sedna Xelastec Tips - These are my tips of choice for IEMs, unless I find them to detract from the sound quality of the IEM or to be uncomfortable with specific IEMs. If I do not mention other tips in the review, these are the tips that have been used.

*I have started to review IEMs based on the tips included with the IEMs. If, for any reason, I find that I need to swap for non stock tips, I will mention it in the review. If I do not mention anything, then stock tips have been used for the review and impressions.

 *Updated as from January 2022.


I publish frequency response and isolation measurements of the IEMs I review. All frequency response measurements of IEMs can be found and compared on: and all isolation measurements can be found and compared on

They can also be found in video format on the Solo Spec YouTube channel, although this channel is constantly falling behind on content due to my lack of time.

More information on how the measurements are taken etc. can be found here:

Final Word...

I hope that this page has given some in depth information into my reviews and how I go about them. As things change in my set up or system, I will update this page accordingly with the date that said changes have been implemented.

Thank you for all your support and I hope that Acho Reviews is a useful tool for those looking for information regarding the products that I am lucky enough to test and review.

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