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Ricci's Skram Subwoofer & Files


Ricci

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Is this an outdoor measurement? How far away is the nearest large object? Building, truck, etc?

Looks like about 8db down at 30Hz compared to 100Hz. The tuning seems to be a bit under 30Hz as well.  I'd expect about 4 or maybe 5dB down at tuning with those drivers. The HPF probably shaves another 1db off. Realistically this isn't too far off. Once all of the factors such as driver tolerances, construction methods, signal chain, measurement setup and atmospheric conditions are stacked up it can account for quite a bit of variation. I'd not worry about it too much if it's a little different from the model or other peoples measurements. 

Is the mic equidistant between the vents and the upper section or closer to one vs the other? That could account for another 1dB.

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2 hours ago, Ricci said:

Is this an outdoor measurement? How far away is the nearest large object? Building, truck, etc?

Looks like about 8db down at 30Hz compared to 100Hz. The tuning seems to be a bit under 30Hz as well.  I'd expect about 4 or maybe 5dB down at tuning with those drivers. The HPF probably shaves another 1db off. Realistically this isn't too far off. Once all of the factors such as driver tolerances, construction methods, signal chain, measurement setup and atmospheric conditions are stacked up it can account for quite a bit of variation. I'd not worry about it too much if it's a little different from the model or other peoples measurements. 

Is the mic equidistant between the vents and the upper section or closer to one vs the other? That could account for another 1dB.

Did you add baffle gain calculated in Edge to the hornresp prediction?
In my last project I got the predicted response to be within 1dB of the actual half-space response, but I had to double the baffle size in Edge (maybe that's the effect of the half-space loading: it mirrors the baffle on the ground basically), hence way more upper bass than hornresp predicted.
I'm not sure how this translates to larger cabs, but it was spot on with my single 21", a tad smaller than the Skram.
Hornresp was also fed with the set of complex inductance parameters. I used the specs for the 21ds115 you measured.
Same thing applied to my 1x12" sub. Model response was spot on with the measurement.

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On 7/13/2022 at 8:27 PM, Ricci said:

Is this an outdoor measurement? How far away is the nearest large object? Building, truck, etc?

Yes, this is outdoor ! There was a wall 10 meters on the left and a house 20 meters behind.

On 7/13/2022 at 8:27 PM, Ricci said:

Is the mic equidistant between the vents and the upper section or closer to one vs the other? That could account for another 1dB.

The mic was at 3 or 4 meters, on the ground, centered on the subs so probably closer to the upper section than the vents. 

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Has any fine folks on this thread had the chance to run impedence measurements on the skram? I thought about using the skhorn measurements as a close approximation if none were available but it would really help me for sizing up the right amplifier.

I am looking to run two Eminence NSW6021 (nominal 6 ohm) per amplifier and an considering two options:

1. operating a 2 channel amplifier in bridge mode with 2 drivers hung in parallel (net 3ohm). However, this would theoretically put a 1.5ohm load per channel (which is below the rated 2ohm minimum per channel) - that is unless the cabinet loading (acoustic impedance) raises the effective impedance to something more tolerable for the amplifier. 

2. Purchasing a 4 channel amplifier and also running it in (dual) bridge mode. Here I would hang one driver off each 'stereo bridged channel' and therefore only impose a 6 ohm load per bridged channel (ie: 3ohm spread across 4 channels which is more tolerable for the amplifier). +whatever cabinet effects may impart on the impedance the 'amplifier sees' 

First option is a bit more budget friendly so that would be my first pick. 

Amplifier is Wasi W15K or W15K4 respectively 

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