Distorted Bass in IEMs

[netcarlos]

I am a bassist, and since our band switched to IEMs, I have been struggling to achieve a clean sound at a high enough volume in my headphones.

The signal chain is as follows: Passive Jazz Bass -> Jad Freer Capo DI -> Presonus SL 24R -> Millenium HPA In Ear -> MEE Audio M6 Pro 2nd Gen.

Upon initial setup, I noticed that I am unable to properly adjust the gain on the input of the Presonus or on the aux output without experiencing distorted bass guitar sound in my IEMs. I have to keep both levels in the "green" zone and avoid the "yellow" entirely. This forces me to maximize the gain on my headphone amp. However, this leaves me with no additional volume reserve for potential stage use, and the sound is still not loud enough (especially considering the presence of a loud drummer nearby).

For comparison, I connected my headphones directly to the headphone monitor output on the Presonus main channel, and the sound was clean and sufficiently loud (probably because of on-board headphone amp). This leads me to believe that either the output from the Presonus rack mix is too hot or my headphone amp is unable to handle the bass frequencies.

I have also attempted using a Behringer PM1 instead of the Millenium HPA, but encountered the same issue.

I acknowledge that this setup is relatively budget-friendly, and I am willing to invest more. The initial goal was to transition the entire band to IEMs and then upgrade equipment once we are all comfortable with the system.

 

Rather boring technical specs follow:

Spoiler

Parameters stated in the manuals and technical sheets are as follows:

# Mee M6 Pro
https://www.meeaudio.com/EP-M6PROG2/

| **impedance** | 16 Ohms at 1K  | 
| **sensitivity** | 100±3 dB (1mW at 1KHZ)  | 
| **maximum power input** | 30mW |

# Presonus flexmix output

Maximum Output Level +24 dBu, ±0.5 dBu
Output Impedance 100Ω

# Millenium Hpa in ear headphone amp

Technical specifications

Audio inputs 2 × XLR / 1/4" TRS jacks (balanced)

Input impedance: 15 kΩ

Nom. Input level (balanced): 0 dBV

Max. input level (balanced): +4 dBV

Input level limit (balanced): +5 dB

Headphones output 1 × 3.5 mm phone jack (stereo)

Min. load impedance: 16 Ω per channel

Frequency range

30 Hz … 20 kHz (± 2 dB)

Output power 50 mW per channel max. (@ 20 Ω load)

 

Edited September 27, 2023 by netcarlos

[Bigguy2017]

Are you using an HPF on the Studio Live ? Put lots of cut below 35Hz - 50-Hz ish...

Could be lots of low frequency mush overloading the input.

[Richard R]

Let me check I understand this:

If the input signal level to the desk is in the green, and the aux output to the IEM headphone amp is green, then the sound is clear, but the volume in the phones isn't high enough and there's no headroom.

If the output from the aux is up in the yellow (-6db?), then there's headroom, but the sound you hear is distorted. 

Monitoring the aux output straight from the desk, the sound is clear.

 

That's odd. It does suggest the HPA doesn't like the bass, definitely worth a serious cut below 40Hz.

 

Are you using an XLR to XLR for the IEM feed? XLR to TRS may be wired balanced, or unbalanced, and the wrong one will sound odd.

 

We use mainly Behringer P2s at church,  from an Allen & Heath desk, and the youth band have the same from I think a Presonus rack. Never had any problems with the output level from either, they are industry standard.  ( I can't remember the conversation from dBu which is what the desk spec is and dBV on the monitor, which is annoying!)  I find I run the P2 at about ¼ of the way up the volume level and its loud enough into my cheap headphones.

[jazzyvee]

For the past  year since the band got an IEM system, BehringerX32 i think). 

I have tried various headphones from ACS moulded earplugs, sony domestic headphones, behringer,sennhieser and Shure body packs and i still get edgy distortion through whatever headphones I use. 

My thoughts are that it has something to do with Gain staging, but i don't really understand fully what that is or how to address it. 

For DI I have used the DI on my bass rack preamp which is a transforrmer isolated one, or a Stanley Clarke Acoustic preamp pedal. 

All my basses are active but in order to use the IEM i have to set the volume on my bass to just barely open, my preamp gain to 1.5 and the sound is still edgy.

 

What I don't understand is this, i have a Tascam GB10 headphone practice unit which I can plug the same bass in, set a sensible volume and that does not distort. I can use my SC acoustic preamp and do the same thing and plug an external sound source in and whack the volume up and there is no distortion and normal playing volumes with whatever headphones i'm using also.

Then when using my same bass rig for gigging and give the sound guy the same DI out from the preamp, i don't have any complaints about distortion from my setup.

 

Now considering the OP has a passive bass with similar issues i don't think having an active bass is the issue here. 

 

So how come this new rack IEM system is having problems with what ever of my basses i use through our IEM system? Is there a setting that i can suggest to the guys? 

 

 

[Dood]

The Behringer PM1 is passive and thus it won't distort in the same way that the HPA, so, if you are still getting horrible distortion with the PM1, it's not the headphone amp at issue. So, it will either be the gain stage at the output you are connecting HPA to or the "IEM"s. Can you tell if it's source distortion or the earphone distorting? It's a very different sound. 

[Dood]

1 minute ago, Dood said:

The Behringer PM1 is passive and thus it won't distort in the same way that the HPA, so, if you are still getting horrible distortion with the PM1, it's not the headphone amp at issue. So, it will either be the gain stage at the output you are connecting HPA to or the "IEM"s. Can you tell if it's source distortion or the earphone distorting? It's a very different sound. 

 

Also, have you tried (naturally) a different set of earphones in the same fault finding scenarios? That would have been my next move.