Any driver's radiation pattern up to ~100 Hz would be fairly omni-directional, which is why subwoofer
orientation doesn't really matter. [Subwoofer placement always does.] Else, e.g., a down-firing design would generally be faulty.
Above ~100 Hz sound power becomes more and more directional, which is why driver orientation starts to matter. You can see this on
amirm's L12 measurements. Thankfully, all Rythmik Audio subwoofers do behave similarly on purpose; mainly differing in THD and max. SPL; so this can be used as a guide. // I tried to find some visualized 3D radiation patterns of loudspeakers emitting different frequencies - but I didn't find any satisfactory information on the fly.
I knew about subs becoming more directional at higher frequencies, I just wasn't sure why orientation would make a huge difference given that they're still coming from two sources that are probably just inches apart (the two sub drivers, I mean). Seems strange Rythmik would say the subs can work up to 200Hz if they aren't really meant to be used above 100Hz.
I guess it would be possible with
Audiolense XO. (I'm sure
@mitchco would know how.)
Maybe treat each "subwoofer stand" with its bookshelf-loudspeaker on top as a single (near) full-range loudspeaker; crossed-over according to the driver(s) arrangement but at a possibly high frequency and of course, properly time-aligned to each other. Have this combination play down to, probably, around 60 Hz or 40 Hz.
Below this, for the last octave or two, do a usual crossover to the remaining "free" subwoofers. + dedicate these also to the LFE-channel.
That's an insane idea - but a fascinating one.
It is a fascinating idea but seems really complicated.
You could assign one output from your crossover to multiple (identical) subs. How you do this will depend on the subwoofers and the set-up, and may require extra hardware (e.g. a distribution amplifier). But one example would be the four identical subs, one in the centre of each wall, all fed the same signal from the same output, via either a daisy-chain or a distribution amplifier. And then the other 5 subs from the other output via the same type of chain.
The main thing I don't like about that is assigning all my big subs to the same output, which would mean setting the distances/crossovers on the back pairs manually to match the fronts and having Dirac do any bass correction on all of them at once rather than each individually. I doubt I'd go with that option, but if I did I'd probably have to run the speaker outs from my AVR into some kind of DSP device that I could then use to set crossovers and run multiple outs to the subs and to the power amp for the monitors. That would mean I'd need 5 inputs and 10 outputs and probably a lot of learning/trial-and-error on how to operate the DSP. Probably way too much trouble than it's worth, but the idea does intrigue the tinkerer in me.
Yeh, the severe distortion at the SPLs Amir measured at are obviously below the port tuning, but depending on desired SPLs, I don't think looking at the region of the graph I've put a box around is necessarily a waste of time:
View attachment 86784
Yeah, it's that distortion in the 100Hz-200Hz range that bothers me. I know human ears are less sensitive to distortion in the bass, but doing a little research I found
THIS, which suggests distortion in that range becomes audible at about 14dB down, which is about 20% IIRC. That measurement at 96dB already shows that area hitting 5% at its highest. If I figure that this is a range that's probably going to contribute a lot the total SPL, it's not hard to imagine it reaching levels well over 100dB with distortion multiplying exponentially.
Even if localisation isn't a problem, successfully crossing over subs at 200Hz when they are not directly below/beside the speakers is not going to be easy (or a good idea IMHO). The wavelength of 200Hz is only around 170cm, and the crossover won't be a brick wall filter, so the overlap between mains and subs is going to extend to even higher frequencies (shorter wavelengths). So we're talking about short wavelengths in relation to the distances between subs, speakers, and listener, which is going to mean issues with coherent summation of the output from the subs and speakers.
To get an idea of the Sierra's bass capabilities, have a look at the distortion measurements of the
Horizon.
Between this and Olli's post I did have another idea: couldn't I use the F18's as a speaker stand for front monitors and run them to 200Hz? I know the common objection to doing this is that speaker location is rarely ideal for subwoofer location, but if I'm going to have 4 subs I could just position the other two subs optimally to help with whatever issues come from running the front two subs underneath the monitors. Besides taking the 5.25" drivers out of the equation, this would have the added benefit of saving me money of only purchasing monitors rather than towers. At that point my issue would be rather the mid/tweeter on, say, the Sierra 2EX is as good as that on the towers, or perhaps whether I should look into other monitors.
I'm running 4 x HDI 3600s and 1 HDI 4500 center along with 2 older HSU subwoofers. Just going to add I don't believe you'd ever be disappointed in choosing your choice of the HDI line for either music or movies.. Had mine for about 4 months now and they continue to impress me with their ablity to reveal fine detail while at the same time deliver dynamic impact when the source calls for it.
I've considered upgrading my subs sometime in the future but I've been running these HSU for about 5 years now and they've never let me down in my small listening space.
Good luck, Sal
Thanks for the mini-review!
Four 18 inch subs make your house rattle to high heaven. A rattling house is just plain unpleasant during a music listening experience.
My room is larger (18ft by 24ft) and two F12G subs have been just fine really. There are differences between theorycrafting and reality.
My old system had a 21" sub. I de-rattled everything in my room and the adjacent rooms when I got it. Only thing that rattles when I put on organ music with huge 16Hz tones is my brain.
