[baskingshark]

I am considering buying a Bluetooth dongle with my T800. But I am a bit concerned of the MMCX connectors becoming loose after swapping many times. I am wondering if anyone has some experience in this regard. Thanks in advance.

T800 has a very low impedance of 9ish ohms, and pairs best with sources with as lowest output impedance as possible, ideally < 1 ohm, as per @Ace Bee 's above post. Do make sure your BT dongle meets the < 1 ohm output impedance, otherwise the FR will be skewed and the T800 won't sound as good.

How did this < 1 ohm output impedance come about for the T800?

Do read this article about the "rules of eights" here: https://www.headphonesty.com/2019/04/headphone-impedance-demystified/#:~:text=Pairing a headphone with an,driver control (damping factor). The article has a "conclusions" segment that is pretty useful, if it is too long to read, that should suffice.

So based on this "rules of eights", for source and headphone/IEM matching, they advise that the headphone/IEM impedance be divided by 8, and that is the maximum source output impedance that should be paired. Ie if you have a 32 ohm IEM, if this is divided by 8, then ideally a maximum 4 ohm output impedance for the source is the highest that you should be accepting for output impedance, so as not to affect sound quality. This is just a guide of course, exceptions exist and as usual YMMV.

For the T800, the advertised impedance is 9.2 ohms, so 9.2 divided by 8 means a 1.15 ohm (let's round this down to 1 ohm) is the max source output impedance you should accept.

So this article states: " “…if an amplifier's output impedance is significantly more than an eighth of the headphone’s impedance, the frequency response and sound of the headphone can change. This results in bigger mismatches and creates more variation from the headphone’s default sound signature. The way that a headphone responds to an amplifier with output impedance higher than one eighth of the headphone can be entirely erratic – different headphones will respond in different ways, but generally the results will be negative.” – RHA Audio "





About swapping MMCX on the T800. I've owned the T800 for almost 2 years already, and I've also owned 5 other Audiosense IEMs, none have failed in the MMCX even after frequent cable changing. I think Audiosense really uses premium MMCX connectors, so no worries with that aspect.

This is in contrast to some other budget CHIFI with quite bad MMCX QC that I've experience, cough cough Urbanfun, Tin HIFI to name a few. They were spinning like helicopters out of the box!!

 

[edb]

Please make sure of the output impedance of those dongles. If not paired properly T800 sound may drastically change. Usually around 1 ohm output impedance suits it well. I'd say rather buy some usb dac-amp, like shanling up4, fiio btr5, etc.

I am looking for something for mobile listening, like casual listening to audible.com, or using the mic on the bluetooth dongle for zoom meeting. So sound quality is not a concern. It seems Audiosense discontinued its own bluetooth dongle.

 

[Ace Bee]

T800 has a very low impedance of 9ish ohms, and pairs best with sources with as lowest output impedance as possible, ideally < 1 ohm, as per @Ace Bee 's above post. Do make sure your BT dongle meets the < 1 ohm output impedance, otherwise the FR will be skewed and the T800 won't sound as good.

How did this < 1 ohm output impedance come about for the T800?

Do read this article about the "rules of eights" here: https://www.headphonesty.com/2019/04/headphone-impedance-demystified/#:~:text=Pairing a headphone with an,driver control (damping factor). The article has a "conclusions" segment that is pretty useful, if it is too long to read, that should suffice.

So based on this "rules of eights", for source and headphone/IEM matching, they advise that the headphone/IEM impedance be divided by 8, and that is the maximum source output impedance that should be paired. Ie if you have a 32 ohm IEM, if this is divided by 8, then ideally a maximum 4 ohm output impedance for the source is the highest that you should be accepting for output impedance, so as not to affect sound quality. This is just a guide of course, exceptions exist and as usual YMMV.

For the T800, the advertised impedance is 9.2 ohms, so 9.2 divided by 8 means a 1.15 ohm (let's round this down to 1 ohm) is the max source output impedance you should accept.

So this article states: " “…if an amplifier's output impedance is significantly more than an eighth of the headphone’s impedance, the frequency response and sound of the headphone can change. This results in bigger mismatches and creates more variation from the headphone’s default sound signature. The way that a headphone responds to an amplifier with output impedance higher than one eighth of the headphone can be entirely erratic – different headphones will respond in different ways, but generally the results will be negative.” – RHA Audio "





About swapping MMCX on the T800. I've owned the T800 for almost 2 years already, and I've also owned 5 other Audiosense IEMs, none have failed in the MMCX even after frequent cable changing. I think Audiosense really uses premium MMCX connectors, so no worries with that aspect.

This is in contrast to some other budget CHIFI with quite bad MMCX QC that I've experience, cough cough Urbanfun, Tin HIFI to name a few. They were spinning like helicopters out of the box!!

Not just higher, significantly lower impedance than 1 ohm affected T800 negatively as well. WHen I paired it with Shanling M0 (O.I. 0.4 ohm), the sound was significantly more bassy, veiling the midrange even a bit. Out of my phone (no idea of its O.I., it's a Samsung Galaxy J6) it was quite sharp and piercing and harsh...but when I paired it with Fiio Q5 (modded), it was perfect!

 

[wayofthedawn]

I am considering buying a Bluetooth dongle with my T800. But I am a bit concerned of the MMCX connectors becoming loose after swapping many times. I am wondering if anyone has some experience in this regard. Thanks in advance.

This tool is super helpful:
MMCX Tool

How to use:

 

[edb]

I take a quick look at the MMCX Wikipedia page, and found the following.
It refers to the spec of one particular brand. When I check a few other brands' specification, I found similar numbers, 500 pairing cycle and 50Ohms impedance. It is probably an industry stand.

Micro-miniature coaxial (MMCX) connectors are coaxial RF connectors similar to MCX but smaller. They conform to the European CECC 22000 specification. MMCX connectors are rated to 500 pairing cycles.[1]

The connectors have a lock-snap mechanism allowing 360-degree rotation and usually have a 50 Ω impedance. They offer broadband capability from DC to 6 GHz.[2]

 

[Rush87]

I take a quick look at the MMCX Wikipedia page, and found the following.
It refers to the spec of one particular brand. When I check a few other brands' specification, I found similar numbers, 500 pairing cycle and 50Ohms impedance. It is probably an industry stand.

The 50 Ohm impedance is for RF signals, to match 50 Ohm impedance cables and other circuitry. When we talk about audio, impedance really means resistance in many instances, like in the case of output impedance or cable resistance. When we talk about dynamic or other drivers, impedance is the correct term as they have inductance, which, is a kind of resistance for AC signals (at certain frequencies), which may be different from it's DC resistance. A solid state amp's output impedance should be roughly equivalent to a resistor and not have significant inductance.

All that to say: ignore this 50 Ohm impedance spec for analog audio stuff.

 

[peter123]

Not just higher, significantly lower impedance than 1 ohm affected T800 negatively as well. WHen I paired it with Shanling M0 (O.I. 0.4 ohm), the sound was significantly more bassy, veiling the midrange even a bit. Out of my phone (no idea of its O.I., it's a Samsung Galaxy J6) it was quite sharp and piercing and harsh...but when I paired it with Fiio Q5 (modded), it was perfect!

I'm pretty sure it's the sound signature of the M0 causing this. There's absolutely no logic in that a lower oi should make the sound more bassy.

 

[Vasarely]

Not just higher, significantly lower impedance than 1 ohm affected T800 negatively as well. WHen I paired it with Shanling M0 (O.I. 0.4 ohm), the sound was significantly more bassy, veiling the midrange even a bit. Out of my phone (no idea of its O.I., it's a Samsung Galaxy J6) it was quite sharp and piercing and harsh...but when I paired it with Fiio Q5 (modded), it was perfect!

I use the AudioSense T800 with my FiiO Q5 (AM3A module) and sometimes with FiiO Q1 MKii balanced output both. It sounds very good, I haven't any problem.

 

[RikudouGoku]

I'm pretty sure it's the sound signature of the M0 causing this. There's absolutely no logic in that a lower oi should make the sound more bassy.

It is possible, as seen on this iem:

https://www.audiodiscourse.com/2019/06/campfire-andromeda-mini-review.html

 

[edb]

It is possible, as seen on this iem:

https://www.audiodiscourse.com/2019/06/campfire-andromeda-mini-review.html

As an experimental physicist, I always have doubtful thoughts on those FR curves. What were the error bars of those curves? How large was the sample size? What were the conditions under which those curves were obtained? Those are just a few of many questions I always have in my find.

 

[Ace Bee]

I'm pretty sure it's the sound signature of the M0 causing this. There's absolutely no logic in that a lower oi should make the sound more bassy.

No, it isn't. I have checked with my other iems - UM 3DT, UM MIRAGE, Penon Orb, Little Dot Cu-KIS. None had such a drastic increment of bass while switching between my phone, m0, up4. Only the Andromeda and T800 showed such a similar radical increment of bass.

 

[Rush87]

An amp's output impedance (resistance) can mess with an IEM's passive crossover, resulting in altered filter responses and therefore frequency response. It has nothing to do with an amp's "signature" (a hifi amp should not have an FR signature, it should be flat). Plug in some high impedance cans and the "signature" will be gone.

 

[peter123]

An amp's output impedance (resistance) can mess with an IEM's passive crossover, resulting in altered filter responses and therefore frequency response. It has nothing to do with an amp's "signature" (a hifi amp should not have an FR signature, it should be flat). Plug in some high impedance cans and the "signature" will be gone.

A) All amps don't sound the same.
B) I've never seen any documentation that a lower oi should alter the sound, only higher. Can you please link to some information about how and why lower oi will alter the frequency response.

 

[Rush87]

A) All amps don't sound the same.
B) I've never seen any documentation that a lower oi should alter the sound, only higher. Can you please link to some information about how and why lower oi will alter the frequency response.

A) An amp's FR response should be flat.
B) High OI can mess things up. OI close to 0 Ohm will not alter the sound as the "perfect" OI is 0 Ohm.

C) You quote me, but I have not said what you imply.

 

[peter123]

A) An amp's FR response should be flat.
B) High OI can mess things up. OI close to 0 Ohm will not alter the sound as the "perfect" OI is 0 Ohm.

C) You quote me, but I have not said what you imply.

I suggested that the amps signature could be the explanation to the change of frequency response as low oi is very unlikely to be the issue. You than say that an amp should not have an signature, I assumed that was a reaction to my post but never mind.

As you live in a world where all amps should sound the same and I live in one where in reality they don't I don't think this discussion is going to be fruitful so instead of continuing it I wish you a happy weekend