Tux, are you using gating or response smoothing? If gating, then what is the gate time? It looks like the gate time is too short to see any meaningful data in the 200-1000 Hz range.
On this last set of measurements for the BSC, it was quick and dirty, the gate was about 3ms.
For my first set I was 1.2m from the first reflection and my gate was about 4ms iirc. Data is good to 500hz at least. On the first batch more like 300hz. It's partly why I crop my graph so people don't read to low.
You can see a dip in the response around 750hz, that is real.
Edit, just checked my OP. I had the IR in units of distance. It was about 1.3m which corresponds to about 3.8ms. 1/0.0038s = 263hz. I wouldn't read them below 300hz and even then they're a little glossy. I don't have plans to take these outside.
For my first set I was 1.2m from the first reflection and my gate was about 4ms iirc. Data is good to 500hz at least. On the first batch more like 300hz. It's partly why I crop my graph so people don't read to low.
You can see a dip in the response around 750hz, that is real.
Edit, just checked my OP. I had the IR in units of distance. It was about 1.3m which corresponds to about 3.8ms. 1/0.0038s = 263hz. I wouldn't read them below 300hz and even then they're a little glossy. I don't have plans to take these outside.
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At 300 Hz resolution, your next point is going to be 600 Hz. Not very accurate for veiwing the baffle step. I would instead use response smoothing, set it to 1/3 octave smoothing. I think this is a better way to look at the overall trend, especially for baffle step correction.
How did you arrive at 7 Hz? I just checked my reference, the gating you choose determines your resolution.
Also, there is no hard transition frequency in small rooms. If you assume 300 Hz as the transition to the modal region, the room can and does contributes above 300 Hz. So, gating at 300 Hz does not ensure room-free measurements.
If you use response smoothing, you involve the room, but 1/3 smoothing really lets you see the trend and essentially that is what you are hearing. You don't really hear the deep nulls from floor bounce which the measurements report.
Oh, and in Arta, you can apply smoothing to gated measurements. IIRC, you cannot do that in Holm.
Also, there is no hard transition frequency in small rooms. If you assume 300 Hz as the transition to the modal region, the room can and does contributes above 300 Hz. So, gating at 300 Hz does not ensure room-free measurements.
If you use response smoothing, you involve the room, but 1/3 smoothing really lets you see the trend and essentially that is what you are hearing. You don't really hear the deep nulls from floor bounce which the measurements report.
Oh, and in Arta, you can apply smoothing to gated measurements. IIRC, you cannot do that in Holm.
If you are going to measure in your bedroom/basement/garage, you are going to have to gate at the first reflection. That's going to be the floor bounce and depending on how far the treble driver is off of the floor, that's going to be 3-4ms. The type of acoustic treatment that is necessary to get even close to anechoic is way beyond what most DIY'ers have in funds or space.
The first reflection is easy to spot in the impulse plot. You have to set the gate before the leading edge of the reflection. Once the plot is properly gate, all of that high frequency trash goes away and the plot looks a lot like a 1/6th octave smoothed plot. This is a hint to those who insist on seeing the raw data.
Bob
The first reflection is easy to spot in the impulse plot. You have to set the gate before the leading edge of the reflection. Once the plot is properly gate, all of that high frequency trash goes away and the plot looks a lot like a 1/6th octave smoothed plot. This is a hint to those who insist on seeing the raw data.
Bob
I'm on my phone away from my computer, but 7hz was just an estimate from experiernce. I think the confusion is the term "resolution". The resolution could be 1hz, or the resolution of my monitor. But what is the accuracy. The accuracy goes down as you get close to the gate. That's why I said around 300hz and even than is glossed over.
If you look at the IR in my original post, you can see the gate. It swoops from 2.5 or 3ms down to 4.5ms or so. So really, the gate is letting a little bit of the reflection at 4ms through. That's why the response has 0.5db ripples all the way through. So you're right, the gate isn't a hard cut off.
The best I can do is go outside, put it on a 12' ladder and measure. For this, 24db/oct smoothing is very accurate and for all intents and purposes, anechoic. I don't plan to do that with these though. I do plan to do it with a Fostex FE83en though 😀 Crossing at 450hz, so would like better info than this.
If you look at the IR in my original post, you can see the gate. It swoops from 2.5 or 3ms down to 4.5ms or so. So really, the gate is letting a little bit of the reflection at 4ms through. That's why the response has 0.5db ripples all the way through. So you're right, the gate isn't a hard cut off.
The best I can do is go outside, put it on a 12' ladder and measure. For this, 24db/oct smoothing is very accurate and for all intents and purposes, anechoic. I don't plan to do that with these though. I do plan to do it with a Fostex FE83en though 😀 Crossing at 450hz, so would like better info than this.
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