Sub measurement with REW

[meek81]

So I have a little issue and need some help. I am trying to measure my sub by itself and I was told to do so I should set my mains to large temporarily and then unplug the main speaker amd then take sub measurements, but when I do this I get no sound from my sub when I do the sweep. But when I set my mains back to small and still unplugged then my sub makes sound again when I do the sweep.. any idea what the problem might be? Am I measuring the sub incorrectly? I am using Java as I also heard it is better than using Asio, but I am new to all this so what do I know lol.

 

[JStewart]

To measure the sub by itself, using java drivers for right front & left front only, then setting the speakers to small is correct. This way frequencies below the crossover frequency are routed to the sub.
To see as much of the sub’s range as possible using this method then set the crossover to its highest setting. Typically 200Hz or 250Hz.

 

[meek81]

Ok thank you for your response, now by crossover do you mean set the lpf for lfe to 250Hz or the speaker crossover? And also do I unplug my mains or can I keep them plugged in when measuring my sub by itself?

 

[JStewart]

Speaker crossover. That is what is re-routing the low frequencies to the sub when a signal is sent to speakers set to small. (The “Bass Management” system.)
The LPF (low pass filter) for LFE (low frequency effects) only cuts off higher frequencies sent to the sub out directly on the LFE channel, the .1 of a 5.1 channel system for example. It’s typically set at 120hz because the LFE on movie soundtracks doesn’t contain frequencies above that. It does not limit or affect the settings of the speaker crossovers.

 

[JStewart]

The speaker you’re sending the signal to should be disconnected when you want to measure the sub only.
Be careful not to remove or connect wires when the amp or AVR is on. Be careful not to let disconnected speaker wires short by touching. I will typically disconnect just one of the 2 leads from the back of the speaker and cover the bare wire with electrical tape for convenience. Safer is to disconnect the speaker wires from the amp or AVR.
When measuring the sub only send a signal to only the left or right speaker. It’s not necessary to do both.