Versions 4 and 5 of the AugerPort are in!
AugerPort 4 results:
AugerPort 5 results:
Comparing the AugerPort 5 versus the Harman contour it is based on shows the huge improvement in knocking down the pipe resonances:
The issue with all of these is much worse harmonic distortion. To add some data points I did a simple single tone spectrum analysis and you besides the harmonic distortion products, you can see broadband noise in from 500-5000hz that is not present in the Harman, and broadband noise in between the first 4 harmonics that only become an issue in the Harman at higher voltages. Making progress so I'll keep working the tap shape.
Really impressive, looking forward to what's coming next!
Fascinating video on acoustic metamaterials: Acoustic Metamaterials with Steve Cummer - YouTube
@augerpro since you are on a port kick you might be interested in this Polk Audio Reserve Series Loudspeakers Press Event - YouTube Polk's new speakers have a resonator tuned to the resonance of the port in the throat of the port. Looks extremely good on the response charts they showed. May be a lot easier to implement and design parametrically when compared to a soft material method. Don't know the patent number or have technical implementation details, but I would guess that the 2 resonators are tuned around the 1/4 wave frequency of the first resonance to broaden the filtering notch and lightly damped with polyfil.
Not sure what your intentions are with your ports, but from what I have been seeing the Harmen port is ideal for a sub and shouldn't need the resonance reduction. Looks like there is still some opportunity to find a lower distortion port that reduces the resonance for woofers/midwoofers.
It's resonators all the way down... ;)
Turtles all the way down - Wikipedia
That Polk port idea is interesting, but I would totally disagree with a "ETF not needed on subwoofer as the resonance is out of band" It's not out of band for the listener who is listening - far from that, so reducing a port resonance would still make sense. They should just say it saves them on cost and maybe the effect is a bit weaker so they skipped it.
It looks to me to simply be a closed end pipe, with taps in the center, which is also aligned with the center of the port, I'm guessing it's dampening the 1/2 wave. When he shows all the pieces together it doesn't look like there is anything inside the resonator to damp the energy, just hollow? Certainly if anyone can explain what is going on there and how that might inform dimensions I could easily print something similar.
I do wonder that how the harmonic distortion looks, though he does say it chuffed later, so that is promising. That is my main issue, I'm quite happy with the pipe resonance dampening in this last round of designs, but it seems unavoidably to come with worse HD and chuffing.
Yeah, my take away is that you get the strong port resonance reduction with possible low distortion. My assumption on the damping is that they mention "appropriately damped" a few times when talking about the port resonators and the cabinet column resonator.
Looking at your figures lets assume there is a strong resonance centered at ~1900 Hz. If we want resonators at 1800 and 2000 at 1/2 wave they will be 8.5 cm and 9.5 cm. Judging from the images of the cutaway this seems to be more in the ballpark for the floorstander dimensions than 1/4 wave. I wouldn't be able to say on the diameter of port and resonator, by my eye the resonator looks to be ~1/4 the diameter of the port throat. If I were to damp it I would try at the point of reflection and at the inlet. At the inlet it could help to smooth the filtering like for the meta material absorbers. Should be light and not stuffed so as to not affect the tuning.
A thought I am having is they mentioned that the reduction in resonance peak gave a reduction in distortion because of the distortion in that frequency band. But, that would be with a flared ended straight port. The Harmen port does not have significant distortion at the resonance peak, so you may not get the benefits of both concepts here. Hopefully it won't distort as much as the slotted and damped port though.
Given that for a port you could 3d print the mount and inlet you could try a lot of different resonator lengths out with some thin wall pvc.
It kind of looked like the resonators were the same length as the port? Like a parallel port sitting inside the main port with probably the same pipe resonances, but damped and open in the middle to capture some of the main ports energy too?
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