[Fibre101]

Im using the GL850 one with some changes.

 

[Chastity]

Im using the GL850 one with some changes.

As am I but I have a Left shelf of +7.5dB, where you have a -1.5dB

 

[Fibre101]

Yeah, I've lowered the gain on the Low shelf and compensated it for the 32hz pk filter with 0.71Q, Makes for a better low end IMO.

 

[Fibre101]

My personal mod is here:
resonant chamber of non direct reflection, then filled... so sound is more natural than ever. Always punch, detailed, dynamic.
.

has anyone else tried this mod before? if so what were your results?

 

[Chastity]

has anyone else tried this mod before? if so what were your results?

You neglected to link the pic of the chamber filled with polyfill

 

[Fibre101]

You neglected to link the pic of the chamber filled with polyfill

Yeah that one

 

[Metal-Fi]

has anyone else tried this mod before? if so what were your results?

I have tried this mod out of curiosity. The changes described by the user are indeed real; you lose the extra "dullness" and "boominess" that the AMT may show due to internal reflections/resonances, getting a more natural sound. However, I reverted to stock configuration shortly after because when I tried the polyfill mod the drivers had roughly 20hrs of use and, as it seems that AMT's generally take quite long to break in, I preferred to wait and see what's the progression of their tonal signature and balance over time. This is actually evolving and improving (currently around the 100hrs mark, but I have read users suggesting to wait until a 500hr-period of break-in is completed - whether this is realistic or just placebo, I don't know); there is still some extra boom and dullness according to my taste, in particular with heavy and dynamic music, so if this won't change with time, I may apply again the polyfill mod.

 

[Fibre101]

I have tried this mod out of curiosity. The changes described by the user are indeed real; you lose the extra "dullness" and "boominess" that the AMT may show due to internal reflections/resonances, getting a more natural sound. However, I reverted to stock configuration shortly after because when I tried the polyfill mod the drivers had roughly 20hrs of use and, as it seems that AMT's generally take quite long to break in, I preferred to wait and see what's the progression of their tonal signature and balance over time. This is actually evolving and improving (currently around the 100hrs mark, but I have read users suggesting to wait until a 500hr-period of break-in is completed - whether this is realistic or just placebo, I don't know); there is still some extra boom and dullness according to my taste, in particular with heavy and dynamic music, so if this won't change with time, I may apply again the polyfill mod.

Thank you for this! I was thinking the same for burn in time as well! I have around 35-40 hours, so I'm guessing I need a bit more. At first they felt a bit veiled but there were some slight improvements after some time with it. Again, not sure if its just placebo as you mentioned. The polyfill mod is definitely something I will be trying.

 

[Fibre101]

Thank you for this! I was thinking the same for burn in time as well! I have around 35-40 hours, so I'm guessing I need a bit more. At first they felt a bit veiled but there were some slight improvements after some time with it. Again, not sure if its just placebo as you mentioned. The polyfill mod is definitely something I will be trying.

Just tried the mod. I'm pleasantly surprised. Tighter bass response, much airier treble. I wonder if other material would work better.

 

[Metal-Fi]

Just tried the mod. I'm pleasantly surprised. Tighter bass response, much airier treble. I wonder if other material would work better.

Yes, that's essentially what I noticed. What about the soundstage? I do not remember relevant changes, but I could be wrong...

 

[Fibre101]

Yes, that's essentially what I noticed. What about the soundstage? I do not remember relevant changes, but I could be wrong...

Yeah I forgot to mention that too. Sound stage seems to be almost the same but the imaging improved significantly. The placements of instruments are better.

 

[dmagnan]

My personal mod is here:
resonant chamber of non direct reflection, then filled... so sound is more natural than ever. Always punch, detailed, dynamic.
.

I am somewhat interested in your mod. Could you explain the process of getting at the resonant spaces surrounding the drive unit, and the exact material you used to fill these spaces? It looks like glass wool insulation, which might have the disadsvantage of shedding a lot of particles that would affect the driver surfaces. I would assume it should be some sort of organic wool speaker stuffing material.

 

[Metal-Fi]

Yeah I forgot to mention that too. Sound stage seems to be almost the same but the imaging improved significantly. The placements of instruments are better.

Good to hear, that somehow confirms my memories - unaltered soundstage but sharper and more precise imaging. This may help in taking my future decision on the mod.

 

[EmTone]

Has anyone tried to recreate the Soundguys' EQ suggestions for the Monolith AMT? There were no parametric EQ values so I tried to recreate the EQ curve, but it's quite difficult.

https://www.soundguys.com/monolith-by-monoprice-amt-review-65005/

SoundGuys' Monolith AMT B&K 5128 FR measurement:

Here's what they recommended - Soundguys' total EQ Curve:

My end result trying to match their total EQ curve:

Updated EQ: 10/05/2024. Removed the unnecessary extra bass filters that weren't part of the Soundguys EQ & slightly lowered treble (filter 14), + more pictures.

EQ settings:

Preamp: -6.2 dB
Filter 1: ON LSC Fc 30 Hz Gain 5.5 dB Q 0.900
Filter 2: ON PK Fc 30 Hz Gain 2.0 dB Q 3.000
Filter 3: ON HSC Fc 40 Hz Gain -5.0 dB Q 0.800
Filter 4: ON PK Fc 180 Hz Gain -2.4 dB Q 1.100
Filter 5: ON PK Fc 510 Hz Gain -2.8 dB Q 1.900
Filter 6: ON PK Fc 950 Hz Gain -1.0 dB Q 1.100
Filter 7: ON PK Fc 1100 Hz Gain -2.5 dB Q 3.800
Filter 8: ON HSC Fc 1400 Hz Gain 14.6 dB Q 1.100
Filter 9: ON PK Fc 1850 Hz Gain -13.0 dB Q 2.300
Filter 10: ON PK Fc 3200 Hz Gain -3.8 dB Q 4.500
Filter 11: ON HSC Fc 4650 Hz Gain -13.0 dB Q 1.000
Filter 12: ON PK Fc 5300 Hz Gain -4.0 dB Q 4.000
Filter 13: ON PK Fc 8000 Hz Gain -5.8 dB Q 1.300
Filter 14: ON PK Fc 13000 Hz Gain -3.0 dB Q 2.000

They also say "We recommend setting your preamp to -6dB... [and] anything below 100Hz and above 12.5kHz can be ignored" So yeah, I'll probably try adjusting those areas & more to preference at some point. I think the frequency response after their EQ would resemble their SoundGuys Studio Curve v1.1 target, not Harman.

I used WebPlotDigitizer to extract data from SoundGuys B&K 5128 measurement of the AMT and uploaded it to Listener's B&K 5128 database. I can't vouch for how accurate this is when uploaded to a different rig, but we're here anyway.

Monolith AMT original FR & Monolith AMT w/ EQ:

AMT w/ EQ requires -6db preamp.

Sennheiser HD650 & Monolith AMT w/ EQ:

SoundGuys' EQ graphs similiar to HD650. I don't have a HD650 to confirm whether they sound similiar though.

Overall, I think the Soundguys EQ is very, very good.

I like to add for brighter sound:
7800hz, +3.5db Q2
10500hz, -3.5db Q4

---
I've attached the frequency response data of the AMT that I pulled from their measurement using WebPlotDigitizer (.csv file), and the EQ code (.txt file) above in a .zip file case anyone wants to import and edit the OG or EQ'd FR to something else.

- I used Listener's measurement database to import .csv file FR.
- When imported, the FR from the WPD data seemed to be off by +1db when compared to SoundGuys' graph. To adjust, the entire FR was moved down by setting -1db preamp. (or lowshelf filter at 20khz Q0.7 -1db so it doesn't disappear with every EQ edit)
- The AMT w/ EQ's frequency response required around +7db preamp to position at 60db @1000hz. (or lowshelf filter at 20khz Q0.7 +7db so it doesn't disappear with every EQ edit)

 

[Thomasr]

The price swings on these things (on amazon.ca) are insane. They literally double - and then halve - in price from month to month.