Corentin Thiercelin

I'm using the great HISS Tools to measure impulse response. I'd like to be able to make measurement when a long distance separates the microphone from the computer (or the speakers from the computer).

In the first case (mic far from computer), I thought about buying a long XLR cable (I need 100m at least) and a DI to amplify the signal. But I guess I'm going to face quality problems, noise, etc...

So, I thought it could be better to put the computer near the mic and to find a way of wiring the computer to the speakers. The way I found is Airplay (using ethernet cable between my computer and a box receiving sound through airplay).

The issue I get in this case is that the latency induced by airplay totally cheats irmeasure~ and the curve I get is far from the one I get when connected directly to the speakers.

My question is, is there a way of telling irmeasure~ that we have a certain delay between the output of irmeasure~ and what we get from the microphone.

As an instance here is two raw curves of IRs measured in the same conditions, one directly wired to the speakers (green), one through airplay (red).

So, I thought it could be better to put the computer near the mic and to find a way of wiring the computer to the speakers. The way I found is Airplay (using ethernet cable between my computer and a box receiving sound through airplay).
The issue I get in this case is that the latency induced by airplay totally cheats irmeasure~ and the curve I get is far from the one I get when connected directly to the speakers.
My question is, is there a way of telling irmeasure~ that we have a certain delay between the output of irmeasure~ and what we get from the microphone.

use-of-hiss-tools-when-long-distance-separates-mic-and-computer

As it may help someone one day, I found a solution. Here is my setup :

The microphone is connected to the computer with an XLR cable (10m long) through an external sound card. I selected "Airplay" as audio output of Max (7.0.5) and connected an ethernet cable (for now it's 2m long but I'll try with the 100m long in the next days) to the Airplay receiver box that's connected to the speakers.

To get rid of the latency issues, I recorded the sweep sequence I want to use for my measure (the one created by irmeasure~). Then I start playing it exactly 2 seconds before starting the measurement process with irmeasure~. (NB: The output of irmeasure~ is no longer connected to the dac~, it's my sfplay~ instead. I only send the adc~ to irmeasure, as I'd do it normally)

I now get the same results when directly connected to the speakers and when using airplay. I hope it'll still work when using a longer ethernet cable.

Hi there, i realise this is an old post, but how did you manage to work out the latency difference?

I am trying a similar idea where I want to capture an impulse response from my Iphone (to emulate the frequency response on my monitors). As i cant send the signal wired to my iphone to play back the sweep into my microphone (then back into adc) Ive had to think of using apps such as airplay and pocket audio. The latency is too much for irmeasure as you have previously stated. If theres a certain way you worked out the latecny I would love to hear it. Thanks in advance :)

I am trying a similar idea where I want to capture an impulse response from my Iphone (to emulate the frequency response on my monitors). As i cant send the signal wired to my iphone to play back the sweep into my microphone (then back into adc) Ive had to think of using apps such as airplay and pocket audio. The latency is too much for irmeasure as you have  previously stated. If theres a certain way you worked out the latecny I would love to hear it. Thanks in advance :)


As I said, I recorded the signal that is used by irmeasure~, then start playing it, then (exactly 2 second after playing has started) I start the irmeasure~ process. The output of irmeasure~ is not connected to the speakers but instead It's the sfplay~ playing the signal.

In your case I don't know if the iphone can act as airplay receiver but if yes, you could apply the same protocol.

Sorry to view your question so late.
As I said, I recorded the signal that is used by irmeasure~, then start playing it, then (exactly 2 second after playing has started) I start the irmeasure~ process. The output of irmeasure~ is not connected to the speakers but instead It's the sfplay~ playing the signal.

In your case I don't know if the iphone can act as airplay receiver but if yes, you could apply the same protocol.
Here is a short example of how I do.

Use of HISS Tools when long distance separates mic and computer