Influence of loudspeaker frequency response

[sergioTOOL]

Hi

What is the influence of the loudspeaker frequency response in the measured/calculated results? I imagine a deconvolution (or DSP method is used to combine the signals) between the reproduced and the measured signal is done to obtain the resulting impulse. Are these two signals taken from the microphone? or the reproduced internally and the measured from the mic. If it´s the latter then the loudspeaker freq response should definitely influence the results (so as the soundcard´s response). If so, what do you suggest I do to diminish it?.

As always thanks for your help.

Sergio

[brucek]

he loudspeaker freq response should definitely influence the results (so as the soundcard´s response)

The soundcard and mic are part of the test equipment, and so these two items are rendered flat with calibration files.

The loudspeaker is part of the sound equipment. We don't want to remove its influence from the response received at the mic, which is a combination of the room and the sound equipment (processor+amplifier+speaker).

brucek

[sergioTOOL]

brucek wrote:

The loudspeaker is part of the sound equipment. We don't want to remove its influence from the response received at the mic, which is a combination of the room and the sound equipment (processor+amplifier+speaker).

brucek

Brucek I´m going to measure RT60 in classrooms of around 9m x 6m x 3m. Im only interested in the room´s impulse response not the room + sound equipment impulse response. Subsequently I will calculate the required absorption to reduce the rev time in the classrooms. Hence my previous enquiry and concern regarding the loudspeaker´s response (I will get a different impulse response with different loudspeakers).

I also read in your help files about adjusting filter and target level settings, will these apply to my RT60 measurements considering I´m mainly interested on the 250-2KHz band. Sorry I didn´t grasp this bit too well.

As always thanks for your help.

[brucek]

Subsequently I will calculate the required absorption to reduce the rev time in the classrooms.

With what goal in mind? Let's presume you were able to eliminate the sound equipment from the results, and subsequently were able to treat the room to render it perfect. What equipment would you be able to use in the room to take benefit from the treatment? The answer is - only perfect equipment - which doesn't exist. If a room is treated with nulled test equipment and nulled system equipment, then nothing short of perfect equipment could take benefit.

Be realistic. Most equipment in the 250-2KHz range won't have enough effect for you to make attempts at trying to eliminate speaker imperfections from the responses. Simply null your test equipment and do your measurements and install the treatment.

I also read in your help files about adjusting filter and target level settings, will these apply to my RT60 measurements considering I´m mainly interested on the 250-2KHz band.

All plots are derived from the impulse response, so you must take a standard measurement over the bandwidth of interest with a 75dBSPL target. Filters are not a concern for you, as you're above the modal range where equalizers are used, and your intent is one of treatment.

Actually, the classrooms are a bit small to consider RT60 useful. It is intended for larger rooms (think gym or church). Generally ETC would be used for a smaller room.

brucek

[sergioTOOL]

Thanks!
what do you mean by ETC.

[DrWho]

sergioTOOL wrote:

Brucek I´m going to measure RT60 in classrooms of around 9m x 6m x 3m. Im only interested in the room´s impulse response not the room + sound equipment impulse response.

Just to save you some frustration later on....the RT60 is meaningless in a room of that size (except at the very highest of frequencies).

As far as measuring just the room...you're gonna want an omni-directional speaker source that has a flat power response.

[sergioTOOL]

Mike Bentz

...hence reverberation time is meaningless in a room of this size? You meant the type of measurement carried out by ROOMEQW or in general rev times are meaningless in rooms this size.
Why do you say this? Then, how can I approach reducing reverberation in such a room with calcs and measurements?

Thanks for your help