Exactly right . My excuse is I was only thinking qualitatively in that the out of phase source would cancel its equivalent from the stronger source. I stand corrected for having implied the resulting power would be 10 db. You certainly can't do the computation by adding/subtracting dbs which is tantamount to multiplication as dbs are logs and as you point out 10 db doesn't make sense.
Exactly wrong. Example, you have two closely spaced sources. To make it simple assume two sources separated by much, much less than a wave length at the frequency where you want to compute the combined result. I.e. both sources are in phase everywhere. Let both radiate at 90dB. So the power of each sources is 10^9. Power = 10 x Log (I) where I is intensity = (P/Pref)^2. If you assume two sources and sum the two powers you get 2 x 10^9. 10 log (2x10^9) = 93 db, a 3 db increase. But what actually happens is that the pressure fields sum. So the pressure P doubles and the new intensity, I' = (2xP/Pref)^2 increases by a factor of 4, I' = 4 x (P/Pref) = 4 I. Thus the power increases to 10 log (4x10^9) = 96 dB, a 6 db increase and the correct and well known result for the power for two closely spaced sources which radiate individually at the same level.
Me too.
Good to see the 8c being discussed on my good ol' diyaudio.com! I'm one of the guys of Dutch & Dutch and I did most of the acoustic design work on the 8c's.
It's used to be like that, but with pure trial & error I never achieved very good performance over much more than one octave. You need to match both amplitude and phase to get really good cancellation and getting that across the entire working range is not so easy. I developed a optimization method that enables me to do this and thus I now achieve up to -20 dB. Wish I could share the method, but we decided to keep it a trade secret.
I'm not giving away all details, but have a look at the images in this review to get an idea of the internal construction. The location of the back-panel in the cardioid enclosure is of great importance. In the 8c it is very close after where the side slots stop.
Almost. The bass is a closed box, drivers in the back of the enclosure. The 8c is designed to be placed close to the front wall, so there's no wall reflection. The wall becomes part of the design and you get a hemispherical wave-front. I was inspired by the work of the late Roy Allison.
Sounds like a plan! I actually thought along those lines for our pro line of speakers. But our focus is currently on the domestic/studio 8c. For the 8c I don't think it would be an improvement, because I think higher directivity is not desirable in must situations. Besides that, I do think a flat and very smooth response is something to strive for. There's probably no better way to do this than with a waveguided tweeter. With a Synergy style horn you get too much diffraction.
Forgot to actually post the link to the review with the images: 6moons: audioreviews Dutch & Dutch 8c
I definitely enjoyed reading the review, keyser!
Congrats on that well deserved success! Smart engineering and a very cute concept, a bundling of solid concepts in a seemingly relative compact size.
I think Patrick will have a lot of fun reverse engineering it
Out of sheer interest, could you, or rather, would you be willing to share an impulse/STEP response?
Congrats on that well deserved success! Smart engineering and a very cute concept, a bundling of solid concepts in a seemingly relative compact size.
I think Patrick will have a lot of fun reverse engineering it
Out of sheer interest, could you, or rather, would you be willing to share an impulse/STEP response?
Yep. Same delay works also for LR4 acoustic slopes. I prefer LR2, it gives prettier sound, perhaps because transition from monopole-cardioid-dipole is smoother.
These comments apply to my AINOgradient speaker with minidsp. The speaker has downfire bass, xo LR2 around 170Hz to dipole midrange, 800Hz LR2 to dipole upper mid and 4000Hz LR2 or LR4 to dipole tweeter.
Forgot to actually post the link to the review with the images: 6moons: audioreviews Dutch & Dutch 8c
Hi Keyser, I'm mightily mightily impressed by these speakers! (I could easily have thrown in one more "mightily" there). I hope to audition them as soon as I get the chance.
I have only one question about the design, and hope it's ok that I post it here: What user functionality is there actually in the DSP engine? How does it work? That is the thing which is least explained in your material.
I assume the global frequency curve can be adjusted. But can one for example load filters for room correction in the modal region? If so, is there a custom room correction algorithm built-in in the software, or can one load filters from programs such as Acourate and Audiolense?
And would it be possible to somehow program in the use of multiple subwoofers to even out room modes, or would this necessitate external DSP solutions?
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