Interpretation of measurements

[dominique-tanguy]

Good morning to all,

I am not a sound engineer and I need some help to interpret measurements. I obtain reliable results when I place my microphone close to the loudspeaker (blue curve), but when I place it about 1 meter from the cabinet, in order to measure a full range curve for the 3 speakers, I get a severe dip close to 50 Hz (green curve), which is exactly matching the frequency of the second bump of the impedance measurement.

Is there any relation, like phase issue ?

Thank you for your help

Dominique

[Panomaniac]

It is interesting that it comes right at the same place as the higher peak. I don't remember seeing that any any measurement I've done.
Maybe it's a phase cancellation with the port. What happens if you mask the port or move the mic a little bit?

BTW, is that your new impedance plot with the current port? I see that the second peak is higher than the first.

[dominique-tanguy]

I am doing some testing with an extended (deeper port). The higher peak to the right is not conventional but the FR measurement and the listening are a bit better. See the incredible low resonance value for a 515-8G... (normally 37 Hz free air).

Moving the microphone doesn't help and I had the same problem with previous port. I will try tomorrow masking the port.

We are invited by friends this evening...

[RonSSS]

Room response? Or are you measuring this outdoors?

Ron

[dominique-tanguy]

i Ron,

This is room response, 3 ft in front of the loudspeaker cabinet (VOT) for the green curve and just at the end of the front horn for the blue curve.

[GM]

How tall is your ceiling? It looks higher than average, so could be the floor/ceiling eigenmode that would require significant ceiling modification to decay it away. Most rooms [~ 8 ft high] have this notch around 80 Hz where you have a smaller one, so is the exposed beam ~8 ft up?

GM