Attenuating a 'too high' headset mic level

[JohnMac]

Hi Folks,

 

I'm running in to 'overload' problems for a radiomic. With the gain turned down to mimimum on the belt-pack,

the headset is producing too large a signal and the transmitter is clipping.

 

Can any one help with suggestions as to how to attenuate the signal. Can I simply fit a series resistor in the connector? or build a potental divider with two across the transmitter input?

 

Any ideas greatly appreciated :)

 

Regards

 

John Mac.

[Jivemaster]

An L, T or Pi network of resistors may help and could with skill keep the impedance roughly what it should be. HOWEVER watch for possible bias voltages on the cable. -electret capsules may use 2 - 12v for bias and preamp.

[Sound Man]

What is the make of the radio mic system you are using? Check that you are actually turning the gain to minimum as I've seen belt packs with the lowest gain fully to the right.

 

David

[Stuart91]

I've seen people caught out by Sennheiser packs, which have the sensitivity expressed as 0dB, -10dB, -20dB etc. We've have several people who have either missed the -ve sign, or just don't understand the concept of negative numbers, and have assumed that 0dB was the lowest setting, and wondered why everything distorts.

[mackerr]

I've seen people caught out by Sennheiser packs, which have the sensitivity expressed as 0dB, -10dB, -20dB etc. We've have several people who have either missed the -ve sign, or just don't understand the concept of negative numbers, and have assumed that 0dB was the lowest setting, and wondered why everything distorts.

 

Hopefully Sennheiser doesn't call the setting "sensitivity" as that would imply that 0dB is the least amount of gain. If it is called gain it would be more understandable, even pad would be pretty clear to most users.

 

Generally "sensitivity" is the signal level needed to achieve full output.

 

Mac

[JohnMac]

Thanks for your help,

 

System is a Trantec S5.5, transmitter gain is digitally controlled (set via toggling two push buttons) 0 = lowest gain, 9 = max gain.

If possible I would want to fit pad into connector, so a L pad I think is most suited. I'll try and find input impedance of transmitter input and play with Ohms law and a create a potential divider.

 

Once again thanks for your contributions. :)

Regards

 

John Mac.

[Brian]

...so a L pad I think is most suited. I'll try and find input impedance of transmitter input and play with Ohms law and a create a potential divider.

As Jivemaster said, if this is a mic that needs bias (phantom power) then your attenuator will also attenuate this. You might need a capacitor in there as well to stop the DC being attenuated.

[paulears]

There's also a chance that the mic itself (assuming it's a condenser) is clipping, because the Trantecs have a sensible sensitivity range, so tailored for the belters, maybe the mic is just bottoming out?

[Oldradiohand]

There's also a chance that the mic itself (assuming it's a condenser) is clipping, because the Trantecs have a sensible sensitivity range, so tailored for the belters, maybe the mic is just bottoming out?

 

Which then begs the question "where is the mic"? If it's on a boom right next to the mouth it may well be clipping or blasting. Have you tried a different mic, perhaps with a remote capsule and acoustic tube?

[Stuart91]

[Hopefully Sennheiser doesn't call the setting "sensitivity" as that would imply that 0dB is the least amount of gain. If it is called gain it would be more understandable, even pad would be pretty clear to most users.

 

On Evolution systems, it's certainly called "Sensitivity" in the menu.

 

Generally "sensitivity" is the signal level needed to achieve full output.

 

Sennheiser's definition seems to be the opposite way around. With the "sensitivity" on the pack set to -10dB, you'd need a +10dB signal to achieve full output.

 

What we typically find is that headset mics tend to have a higher level coming into the packs and need set at -30dB to avoid distortion occurring. Occasionally this setting has been misinterpreted by the hirer, and they have set the packs to 0dB with unpleasant sounding results.

[nothingatall666]

[Hopefully Sennheiser doesn't call the setting "sensitivity" as that would imply that 0dB is the least amount of gain. If it is called gain it would be more understandable, even pad would be pretty clear to most users.

What we typically find is that headset mics tend to have a higher level coming into the packs and need set at -30dB to avoid distortion occurring. Occasionally this setting has been misinterpreted by the hirer, and they have set the packs to 0dB with unpleasant sounding results.

 

The manufacturer of one certain brand admitted to me the other day that they deliberately turn the gain and sensitivity up so that users HAVE to create a good gain structure on the pre amp (mic pack) rather than boosting the signal after it has been transmitted.

[Jon Wiles]

Hi JohnMac

 

We have the same issue with the 'cheaper' end of the headmic options (CPC Pulse type). (Using the 5.5 system) They are fine normally, but get a person that can actually sing, and it distorts. Using the same singer on a Countryman B3 sorts this out. So I think it's more of an overloading the mic at source issue, rather than the pack

 

 

 

Thanks for your help,

 

System is a Trantec S5.5, transmitter gain is digitally controlled (set via toggling two push buttons) 0 = lowest gain, 9 = max gain.

If possible I would want to fit pad into connector, so a L pad I think is most suited. I'll try and find input impedance of transmitter input and play with Ohms law and a create a potential divider.

 

Once again thanks for your contributions. :)

Regards

 

John Mac.

[TonyMitchell]

 

System is a Trantec S5.5, transmitter

 

Really simple but, have you checked the RX output is set to 'Mic' and not 'Line'

 

Had similar conditions on S5.5 last week and this was the cause.

[stagemanagement]

This!

 

What is the max SPL on the headset you are using?

CPC/ Pulse and even the Proel headsets have a pretty low max SPL (around 125db SPL IIRC?), which any half-decent vocalist is going to plough past when they open up for the big numbers.

 

A higher end headset is going to have a max SPL significantly above that, the Countryman/DPA mic's are up around 136db SPL.

 

Your options are to move the boom well back towards the ear and encourage the wearer to really project their dialogue, or get a different mic!

 

 

 

Hi JohnMac

 

We have the same issue with the 'cheaper' end of the headmic options (CPC Pulse type). (Using the 5.5 system) They are fine normally, but get a person that can actually sing, and it distorts. Using the same singer on a Countryman B3 sorts this out. So I think it's more of an overloading the mic at source issue, rather than the pack

 

 

 

Thanks for your help,

 

System is a Trantec S5.5, transmitter gain is digitally controlled (set via toggling two push buttons) 0 = lowest gain, 9 = max gain.

If possible I would want to fit pad into connector, so a L pad I think is most suited. I'll try and find input impedance of transmitter input and play with Ohms law and a create a potential divider.

 

Once again thanks for your contributions. :)

Regards

 

John Mac.

[JohnMac]

Thank you all for your contributions, sorry in not being active sooner, but a Schools Production of Miss Saigon being my focus last week.

 

My original problem was cured by locking the push buttons on the transmitter preventing the gain from being stepped up over the course of the night.

 

I was trying the Dap Audio EH-2 Miniature Lavalier headset on the principles. Although advertised for use on their Eclipse range, I cut the plug off and rewired to suite my Trantec S5.5 systems.

 

I've got tired of the Pulse headsets failing after a couple shows, and in my opinion they are not as durable as they used to be, with the flex failing at the headset.

The EH-2 states a maximum SPL of 130dB, which once correctly set up with the transmitter coped well, and appears to be a little more rhobust so hopefully will last longer.

 

Regards

 

John Macgregor.