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In ear monitoring headphones & amps

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In ear monitoring headphones & amps

Postby Schultz9927t » Sat Sep 12, 2020 2:01 am

My church is using Shure SE-215CL in ear monitor headphones with presonus hp2 amplifiers. The sound has been distorted at higher volumes and I have checked the gain staging. I am thinking that the headphones and amp are not a good combo. I’ve been trying to figure out how to match headphones to an amp but it’s so confusing. Please tell me simply how to match headphones to an amp. Also tell me if the headphones and amp we have should work together. If not tell me what amp or what headphones to get to fix this. Thanks
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Re: In ear monitoring headphones & amps

Postby Schultz9927t » Sat Sep 12, 2020 9:15 am

The Shure SE-215cl’s are rated an impedance of 17 ohms thus leading me to think that amplification is not need to drive them. But if that is true I’m not sure how I would route the signal from our mixers aux outputs straight into the headphones without a headphone amp. And I’m pretty sure that is not possible due to impedance and level mismatches.
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Re: In ear monitoring headphones & amps

Postby Hugh Robjohns » Sat Sep 12, 2020 11:28 am

Schultz9927t wrote:The Shure SE-215cl’s are rated an impedance of 17 ohms thus leading me to think that amplification is not need to drive them.

I have no idea why you're led to think that... but you're completely wrong! A headphone amplifier is most definitely required.

The specs for the HP2 are a little odd...

They quote a max input level of +4dBV which is only +6dBu... although the input actually limits at +5dBu (see below), so getting the gain structuring right from your console will be important as it will be very easy to overload the amp inputs if you're not careful.

Oddly... having defined the max input level in terms of dBV, Presonsus bizarrely choose to describe the input limit level in terms of dBm. However, dBm is only a relevant term in this context if the input impedance is 600 Ohms, but it's actually 15kOhms... so someone has got themselves in quite a muddle somewhere.

Moving on, the output power is quoted as 50mW per channel with a 20 Ohm load, and that's fine as your Shures are close to that at 17 Ohms -- which is also comfortably above the 12 Ohm minimum impedance* for the amp. So there's no impedance issue to worry about.... *except that I see in the user manual they state the minimum impedance is 16 Ohms and it is possible that the Shures dip below that at some frequencies. I'd be surprised if that is the cause of any problems, though.

The sensitivity of the Shure SE-215CL is pretty high at 107dB/mW, which means with the HP2 amp running flat out you should be able to generate around 123dB SPL into the performers' ears which ought to be more than loud enough... That is the notional threshold of pain, after all!

So I suspect any distortion you're getting is most probably due to over-driving the headphone amp inputs, rather than mismatching between earphone and amp.

If users are complaining that it's not going loud enough, check their earpieces for wax blockages and that they're fitting the earpieces correctly.
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Re: In ear monitoring headphones & amps

Postby shufflebeat » Sat Sep 12, 2020 11:30 am

How many h/p amps are you using?
What are they connected to on the mixer?
How loud is your stage?
What are you putting through the headphones?

Distortion is unpleasant to listen to but if it's caused by too much signal in the headphones then you have a much bigger problem on your hands - hearing damage.

If everything is connected as it should be and you're still having problems it's worth looking at the whole system/environment for ways to improve.

Is anyone using the headphone with "one ear in, one ear out"?
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Re: In ear monitoring headphones & amps

Postby Schultz9927t » Thu Sep 17, 2020 6:56 pm

Okay. I’m going to try keeping the output high and the input lower to avoid overloading the input.

People using the in ears have both in their ears.

I think it’s most likely too much input.

But, I have another question.

I’m trying to choose a pair of headphones to go good with my mixing console.

It’s a yamaha tf5

In the specs it states for the phones section that it has an output impedance of 100 ohms and a phones load impedance of 40 ohms. So which do I use to pick headphones? 40 ohms or 100 ohms?

I was looking at the Sennheiser HD280PROs and the Beyerdynamic dt770 pros. The dt770s have a 32 ohm option. Would that be better to get it closer to 40 ohms? Or am I looking for 100 ohm headphones?

These specs are just confusing.

Thanks
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Re: In ear monitoring headphones & amps

Postby Hugh Robjohns » Thu Sep 17, 2020 7:12 pm

Schultz9927t wrote:I think it’s most likely too much input.

Me too. You need to keep the level at the Omni Outs of the TF5 driving the HP2 amps to below -20dBFS. Any more than that and you'll overload the IEM amplifiers.

In the specs it states for the phones section that it has an output impedance of 100 ohms and a phones load impedance of 40 ohms. So which do I use to pick headphones? 40 ohms or 100 ohms?

The specs suggest the headphone amp is optimised for headphones of 40 Ohms -- that's probably the impedance that allows the amp to develop its maximum power... But anything between about 32 and 100 Ohms will be fine. The headphone amp in the TF5 is quite pokey!

I was looking at the Sennheiser HD280PROs and the Beyerdynamic dt770 pros. The dt770s have a 32 ohm option.

Either will be fine. Buy the ones that are most comfortable for you, and give the best isolation of external sound. I'd probably pick the DT770s, but the HD280s are good value too.
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Re: In ear monitoring headphones & amps

Postby Schultz9927t » Thu Sep 17, 2020 7:50 pm

Okay got it.

Do you think the 32 ohm or 80 ohm version of the dt770’s would be better?
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Re: In ear monitoring headphones & amps

Postby Hugh Robjohns » Thu Sep 17, 2020 8:02 pm

I doubt you'd notice a difference... But the 32 Ohms model is closest to the console's nominal spec.
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