Re: [SlimDevices: Audiophiles] Subwoofers from a high-end perspective?
FWIW, below roughly 300-500 Hz, your room dominates the frequency response of your sub. Imagine your room in 1 dimension -- it's like a guitar strings natural vibrational modes. No matter where you stick your stimulus, you *will* stimulate the fundamental and harmonics of the string, and depending on where your ear is, you'll hear very, very different levels of the fundamental and harmonics. At the center of the string, you'll hear very strong fundamental. Near the nut, you'll hear a bunch of stuff. Except a room is 3-dimensional, and you get these 'modes' in all 3 dimensions. With only 1 sub, it's quite impossible to get consistent frequency response through the whole room. You may notice that when you stand, or sit, or move around, the bass response changes dramatically. This has nothing to do with your sub. It does have something to do with the placement of the sub. Imagine the guitar string analogy: if you pluck the string at dead center, you get a nice pure tone. This is NOT what you want in a speaker -- you don't want to hear the room ring, you want to hear the 'pluck' (i.e. your speaker). Also, if you place it at 1/4 or 3/4, you hear a pretty pure mixture of the fundamental+2nd harmonic. When you pluck near either end of the string, you hear much less of the natural string tones, and more 'pluck'. Extend this idea a bit, and pluck in multiple places at the same time, you can get relatively consistent sound throughout the string. So, in order to get truly great bass response through a large listening area you *must* use multiple subs, and room EQ. If you only have 1 listening spot (or 2 very close together), you can use a single sub, but you still need EQ. How many subwoofers is enough? In principal you need quite a few. In reality, 3-4 tends to get the job done, if care is taken in the setup and EQ. Just as room EQ is mandatory below 300-500 Hz, it's utterly hopeless above 500 Hz. As the room goes from acting like a resonance chamber (below this critical band), to a transmission line/waveguide, it's totally hopeless to do room EQ. There is no possible way that I know of, with a stereo or 7.1 system, you can EQ a wide listening area at, say 1kHz -- 1 kHz is 1 foot wavelength, which means that you can at best EQ about a 1/2 foot diameter sphere. At 20 kHz this goes to a sphere less than 1/2 inch! As for the difference between IIR and FIR, a little background may be helpful. IIR filters are generally based on the analog prototype filters, like butterworth, chebychev, etc. They are always minimum phase filters, which means that the big impulse in the frequency response comes first. FIR filters are usually thought of as *symmetric* FIR filters, which are *linear* phase, constand delay. That means the waveform is minimally distorted, and it makes it easy to add filters together and manage the phase response. FIR filters can happily be truncated butterworth or chebychev minimum phase filters -- you just make them non-symmetrical. This is easy to do. However -- to do a proper EQ of a speaker, the speaker has a 2nd or 4th order rolloff -- and to EQ that properly for a crossover, you need to use an IIR prototype filter. If you do it with an FIR filter, you'll end up making a truncated IIR filter without even knowing it, because you need to compensate for the IIR-ness of the speaker itself. Another interesting tidbit: studies have been done determining the audiblility of minimum phase, vs. linear phase filters. IIRC, neither is minimal audibility. In order to make the minimally audible filter, you need something close to IIR, but not quite totally minimum phase. But I may be remembering this one wrong. I can't put my finger on the paper right now. For information on the subwoofer placement and EQ question, this is a great paper that describes the issues and runs simulations: http://www.aes.org/e-lib/browse.cfm?elib=11355. You can also check out Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms by floyd Toole, chapter 4.3 Domestic rooms and controls rooms. -Caleb -- ccrome2 Caleb Crome Sr. Hardware Engineer Logitech SMBU (i.e. the Squeezebox people) BThe future is here. It's just not widely distributed yet./B I-William Gibson/I ccrome2's Profile: http://forums.slimdevices.com/member.php?userid=18023 View this thread: http://forums.slimdevices.com/showthread.php?t=67022 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] SeeDeClip/TxtDeClip
ntom;462237 Wrote: Interesting thread Have you reached any further conclusion Phil? I'd be interested in knowing whether you are now putting everything through DeClip? Actually...no. What happened was it started me on a quest to hunt down down better masterings of my favourite albums. I now have nearly 100 DVD-A or Dualdisc rips and over 250 better than normal CD rips from remasters of various vintages, including XRCD, SBM, SHM, DCC etc etc. Have you heard the SHM-CD Japanese remasters of Little Queen or Dreamboat Annie by Heart... 16/44.1 - sheer brilliance. Sorry, I digress. I think the software is clever and it works. But it doesn't turn rubbish into gold. -- Phil Leigh You want to see the signal path BEFORE it gets onto a CD/vinyl...it ain't what you'd call minimal... SB Touch Beta (wired) - TACT 2.2X (Linear PSU) + Good Vibrations S/W - MF Triplethreat(Audiocom full mods) - Linn 5103 - Aktiv 5.1 system (6x LK140's, ESPEK/TRIKAN/KATAN/SEIZMIK 10.5), Townsend Supertweeters, Blue Jeans Digital,Kimber Speaker Chord Interconnect cables Kitchen Boom, Outdoors: SB Radio Phil Leigh's Profile: http://forums.slimdevices.com/member.php?userid=85 View this thread: http://forums.slimdevices.com/showthread.php?t=57872 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] SeeDeClip/TxtDeClip
Phil Leigh;462635 Wrote: I think the software is clever and it works. But it doesn't turn rubbish into gold. Good point. I guess it also means that applying such a process to Squeezebox could be good, with improvements ... but don't expect a miracle. -- cfuttrup cfuttrup's Profile: http://forums.slimdevices.com/member.php?userid=32784 View this thread: http://forums.slimdevices.com/showthread.php?t=57872 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Subwoofers from a high-end perspective?
Caleb -- Thanks for the interesting post. I put Floyd Toole's book on my amazon wish list. From a implementation standpoint, I took away two things: 1) At least two subs 2) That, at a minimum, the subs be equalized ( ~100Hz, though 500Hz would be better). Now, if I understand correctly, you are suggesting that IIR filters are better than FIR filters. I know of three options for doing the sub EQ, the built-in PEQ in a Velodyne DD-10, or a Behringer DEQ2496, or Inguz. I assume that the PEQ of the Velodyne EQ the DEQ2496 are IIR-based? (I guess I plug the DEQ2496 into the 'digital loop' of my Transporter?) With Inguz, aren't there two ways of doing this? One is to build a filter from a sweep using DRC (wish I could figure out which DRC parameter would only apply this to 500Hz). But this would be a FIR filter. The other way is using the EQ function in Inguz. I'm not quite sure if this method is FIR or IIR. Inguz describes it as: The InguzDSP EQ filters arent like that. Theyre semi-parametric linear-phase shelving filters. By semi-parametric I mean that you only have two adjustable parameters: frequency and amplitude. And shelving means that the frequency response in between two adjacent bands is a gentle (cosine-based) slope. (See: http://inguzaudio.com/blog/2007/09/27/eq-filters-shelving-and-parametric/) The other question I have is about the pros/cons of active vs passive crossovers for subs? Thanks, muski -- muski Transporter via XLR-Bryston BP26DA-Bryston 4B SST-Wilson Watt Puppy 7s Transporter via XLR-Headroom Max Balanced Headphone Amp-Balanced AKG701s muski's Profile: http://forums.slimdevices.com/member.php?userid=3670 View this thread: http://forums.slimdevices.com/showthread.php?t=67022 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Subwoofers from a high-end perspective?
On a side note I use an MeridianG68J as processor preamp it has a digital filter for subwoofer (of some kind) and DRC below 300Hz and a measurment program to use with it :) So sub works well with stereo to. My own slant on this i don't really believe in satellite speakers so I use sub in conjunction with large floorstanders, then i can have a low xo frequency and the bass will blend well as the speakers have good extension on their own. The bumpines in response with one sub is less severe if you use a low xo as you in practice have 3 sources at some rather low frequency (sub + large floorstanders ). On widh list more subwoofers :) -- Mnyb No it can NOT be controlled with iTunes Mnyb's Profile: http://forums.slimdevices.com/member.php?userid=4143 View this thread: http://forums.slimdevices.com/showthread.php?t=67022 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
