• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Drop + THX Panda Review (headphone)

staticV3

Master Contributor
Joined
Aug 29, 2019
Messages
7,539
Likes
12,005
I think this is the easier way to look at this mathematical problem. Say, Amir measured XYZ mVrms/94 dB SPL. So, how many dB is XYZ mV below 1 V? Answer is 20*log10(1000/XYZ). Add 94 to that and we have our dB SPL/Vrms sensitivity.

I tried your method (first step), doesn't seem correct (or may be I've missed something).

View attachment 129452
2^x=1000/68 gives me x=3.878321.
that times 6 equals 23.269926.
plus 94 makes 117.269926 [dBSPL/Vrms].

Your method gives nearly the same result, but in a more elegant way.
Thanks!
 

solderdude

Grand Contributor
Joined
Jul 21, 2018
Messages
15,891
Likes
35,912
Location
The Neitherlands
I calculate the following way.

(1/the measured voltage in Volts) then Log that number, multiply by 20 and add 94 (the measured SPL)

example the Panda with 68mV.

1/0.068 = is 14.7 (the measured voltage thus is 14.7x lower than 1V which is what we want to know)
Log(10) result = 1.1675 and as we want to know the difference in dB and it is voltage it is 20xlog(10) so 23.3 dB.
94dB is measured at 68mV. The difference between 0.068V and 1V is 23.3dB so is 117.3dB/V

To calculate the dB/mW from the found dB/V I use this calculator
Just fill in the dB/V, select 'dB/V SPL' and fill in the measured impedance (400 to 500hz is fine or at 1kHz) from Amir's plot.
Click on 'calculate' and you get the dB/mW number.
 

warpdrive

Active Member
Joined
Jan 21, 2021
Messages
174
Likes
187
I have these headphones and put them aside as the sound was indeed a bit dull. I don't want to write them off because there is a DSP in there and they are taking steps to keep improving them. If we could upload a base Harman EQ curve, then they could be brilliant because all the fundamentals are there in terms of the hardware.

I liked the original PM3 but something got lost when they shoved the electronics in there. Since passive mode bypasses the DSP, that means the fundamentals from the PM3 have changed maybe unintentionally? There is still a lot of untapped potential in the headphones
 

danweast

Member
Joined
Jun 17, 2020
Messages
13
Likes
33
I have these headphones and put them aside as the sound was indeed a bit dull. I don't want to write them off because there is a DSP in there and they are taking steps to keep improving them. If we could upload a base Harman EQ curve, then they could be brilliant because all the fundamentals are there in terms of the hardware.

I liked the original PM3 but something got lost when they shoved the electronics in there. Since passive mode bypasses the DSP, that means the fundamentals from the PM3 have changed maybe unintentionally? There is still a lot of untapped potential in the headphones
Will from drop has said they did change the tuning on the original design to resolve complains about too dark of sound on the PM3, specifically the damping (https://www.head-fi.org/threads/drop-thx-panda-announcement.921062/).

Point being though, their marketing claims that the DSP is disabled by default--it's a straight signal through both passive and active, unless you EQ.
 

Brianc

Active Member
Joined
May 22, 2019
Messages
137
Likes
125
I have a good friend who buys headphones often, usually based on YouTube hype reviews. I tried these Pandas at his place and guessed they cost less than a $100. Couldn't believe it when he told me what they cost. Tried to convert him to ASR but he doesn't like the focus on measurements over "features".
 

Weebster

Member
Joined
Feb 26, 2021
Messages
27
Likes
26
@Amir Thanks for this review. Also thanks to all for the supporting comments. I have hemmed and hawed about getting these for a year now and I'm glad I held off.:)
 

swarley

Member
Joined
Jan 3, 2021
Messages
10
Likes
7
I have a good friend who buys headphones often, usually based on YouTube hype reviews. I tried these Pandas at his place and guessed they cost less than a $100. Couldn't believe it when he told me what they cost. Tried to convert him to ASR but he doesn't like the focus on measurements over "features".
Some folks like to drink the kool-aid.
 

JohnYang1997

Master Contributor
Technical Expert
Audio Company
Joined
Dec 28, 2018
Messages
7,175
Likes
18,292
Location
China

Remlab

Member
Forum Donor
Joined
May 22, 2021
Messages
74
Likes
186
Location
Oceanside California
I was one of the "Tuning" beta testers for the PM-3. The tuning came after the basic design was complete, so when it came to hitting the Harman target(Our wish), we were very limited with how much we could achieve compared to starting with a blank slate. One thing I wished we could have spent a little more time on was bringing down the mid-bass bump a little more. The deepest bass needed a little more cup volume, so that we couldn't change, and the dip at around 5khz was due to a reflection off the back of the cup that couldn't be eliminated completely with rear damping. It's amazing how tuning headphones is a little like playing whack a mole. Fix one problem and it will have a tendency to create another in the process. In the end, it's all about creating balance. Tons of variables that need to be controlled for in a holistic manner.
 
Last edited:

warpdrive

Active Member
Joined
Jan 21, 2021
Messages
174
Likes
187
While I like the goal of making the active sound quality the same as the passive mode, it seems like using the DSP to tweak the sound could bring this headphone into another level. It has all the parts but they aren't being utilized to the full potential. Or just ship it with a Harman Mode EQ which you can turn on or off, it would sell like hotcakes.
 

Remlab

Member
Forum Donor
Joined
May 22, 2021
Messages
74
Likes
186
Location
Oceanside California
While I like the goal of making the active sound quality the same as the passive mode, it seems like using the DSP to tweak the sound could bring this headphone into another level. It has all the parts but they aren't being utilized to the full potential. Or just ship it with a Harman Mode EQ which you can turn on or off, it would sell like hotcakes.

I think one of the reasons they don't implement the DSP is that it will not only drain the batteries quickly, but it will also push the internal amplifiers into overload. That's the Achilles heel of this type of design. They could have gotten away with DSP if they used a super efficient driver, but the PM-3 driver, which is efficient for a Planar magnetic, is not efficient enough to pull that off effectively.
 
Last edited:

Remlab

Member
Forum Donor
Joined
May 22, 2021
Messages
74
Likes
186
Location
Oceanside California
I was told that a "PM-4" driver is being developed, which is about 2db more efficient, with a much larger diaphragm/ voice coil and added concentric magnets on the outside diameter to control it. Who ends up getting to use it remains to be seen.
 

danweast

Member
Joined
Jun 17, 2020
Messages
13
Likes
33
I think one of the reasons they don't implement the DSP is that it will not only drain the batteries quickly, but it will also push the internal amplifiers into overload. That's the Achilles heel of this type of design. They could have gotten away with DSP if they used a super efficient driver, but the PM-3 driver, which is efficient for a Planar magnetic, is not efficient enough to pull that off effectively.
Not sure if it's an internal amp issue, I think they avoided DSP because of the market they were aiming for. I've tried some heavy PEQs on my pair and that THX amp can certainly handle it, at least audibly as well as my topping stack. Plus the battery life is already so good as is, I can't tell a difference.

I was told that a "PM-4" driver is being developed, which is about 2db more efficient, with a much larger diaphragm/ voice coil and added concentric magnets on the outside diameter to control it. Who ends up getting to use it remains to be seen.
Probably Drop developing it at this point, they bought the designs. That said, a Panda 2 NEEDS to be lighter. That's the downside of planar on the go. These are just simply too heavy, and that's with an entirely plastic body.
 

Remlab

Member
Forum Donor
Joined
May 22, 2021
Messages
74
Likes
186
Location
Oceanside California
Not sure if it's an internal amp issue, I think they avoided DSP because of the market they were aiming for. I've tried some heavy PEQs on my pair and that THX amp can certainly handle it, at least audibly as well as my topping stack. Plus the battery life is already so good as is, I can't tell a difference.


Probably Drop developing it at this point, they bought the designs. That said, a Panda 2 NEEDS to be lighter. That's the downside of planar on the go. These are just simply too heavy, and that's with an entirely plastic body.
According to the engineer who's developing it, no, but that doesn't mean that Drop won't end up getting it.
 

H1a8

New Member
Joined
Jul 1, 2021
Messages
3
Likes
0
I think the reviewer here has a defective pair.
I have the pandas and no way in hell they sound like that frequency graph shows. They even sound a little better than my airpods max. I been testing headphones (even expensive ones) for a long time now.

Anyway. I did research on different frequency graphs measured from different sites. All of them is completely different from his (not even close).
The frequency graph (against the Harmon curve) has from 200Hz to 1KHz flat (some graphs up to 3kHz).

They absolutely do not sound lifeless. If they do then every headphone I've heard sounds lifeless (and I heard a shit load of them).

Defective pair I say.
 

H1a8

New Member
Joined
Jul 1, 2021
Messages
3
Likes
0
i was thinking to buy this headphone a few months ago due to hype on how good these sound, since it is online shop and cant get a listen, decided against it. dodged a few hundred loss. thanks Amir.
They sound great. Don't listen to this review. His graph is drastically different than everyone else's.
They do not sound like that at all.

They sound slightly better than the airpods max. But I prefer the airpods max because they are more comfortable and have ambient mode.
 

danweast

Member
Joined
Jun 17, 2020
Messages
13
Likes
33
Anyway. I did research on different frequency graphs measured from different sites. All of them is completely different from his (not even close).
The frequency graph (against the Harmon curve) has from 200Hz to 1KHz flat (some graphs up to 3kHz).
1625124897442.png

Trust me, after four pairs of these, I wish they sounded better too...
 

staticV3

Master Contributor
Joined
Aug 29, 2019
Messages
7,539
Likes
12,005
I think the reviewer here has a defective pair.
I have the pandas and no way in hell they sound like that frequency graph shows. They even sound a little better than my airpods max. I been testing headphones (even expensive ones) for a long time now.

Anyway. I did research on different frequency graphs measured from different sites. All of them is completely different from his (not even close).
The frequency graph (against the Harmon curve) has from 200Hz to 1KHz flat (some graphs up to 3kHz).

They absolutely do not sound lifeless. If they do then every headphone I've heard sounds lifeless (and I heard a shit load of them).

Defective pair I say.
Here's a comparison of five frequency response measurements from credible sources, all using GRAS systems:
Drop Panda FR Comparison.png

Sources:
I've also included all measurements as .csv and as .mdat, so you can compare them yourself using REW.

With all five you're looking at errors of 5dB at most. Exclude 0dB and it's more like 3dB.
What's more, those sources that publish L/R measurements all show the same channel imbalance between 200 and 2000Hz.

Edit:
Measurements by Resolve on a GRAS 43AG are right in line as well: https://forum.headphones.com/t/the-...tooth-closed-back-headphone/4400/34?u=resolve
 

Attachments

  • Panda.zip
    1 MB · Views: 70
Last edited:

solderdude

Grand Contributor
Joined
Jul 21, 2018
Messages
15,891
Likes
35,912
Location
The Neitherlands
Good catch on the L-R imbalance.

The 'free space' inside the cups will differ between L and R side. This most likely causes this.
One side will (most likely) house the battery while the other side has electronics inside which takes up less 'space'.
 
Top Bottom