MrMcGoo Posted January 10, 2006 Share Posted January 10, 2006 While the forum was down, I purchased the Velodyne digital subwoofer control system, the SMS-1. It is the stand alone version of the brain box of the Digital Drive line of subwoofers. The only feature it lacks is servo control, because the SMS-1 is deisigned to work with any sub. It supports up to three subs. I have the Velodyne equalizing my RSW-15. The user's manual is the manual from hell. It is the most convoluted manual I have ever used. An independent reviewer's write up was far better than the manual. The Velodyne SMS-1 hardware is excellent. Once you learn how to use it, it is relatively easy to use, if you understand bass. You set this gem up by merely running the subwoofer out to the correct input on the rear of the brain box. You hook the subwoofer up to any one of three outputs. You attach a video cable (composite or S-video) and two RCA audio cables to your processor/receiver. The brain box has both XLR and RCA inputs. You are then ready to attach the Mic via a 20 ft. XLR cable. The mic appears to be of VERY high grade. Once you initiate automatic setup the system warbles a sign wave from 16 Hz up to 100 Hz for 25 iterations. The sound is output from the sub and mains at the same time to test the blending process. On each iteration, it tweaks the sub's equalization. You can watch the frequency response curve change on your TV. The auto setup does ok, but to get the best response you need to experiment with different phase settings and rerun the setup. Phase is adjustable in 15 degree increments. The bottom line is that my room response is flat +/- 3 db in less than 30 minutes once I started to tune the system. The system comes with an excellent remote with volume control, night mode that is adjustable and 6 adjustable presets, one of which is zero equzlization. No matter how good your sub is, your un-equalized room response will look like crud. A good equalizer will smooth it out for the primary listening position. The only "error" that requires a manual tweak is that the system will boost some frequencies too much. The maximum boost is 6 decibels while it can cut 12 decibels. In my case it tried to boost 20 Hz by the full 6 decibels, so I merely cut it back to +3. This rascal is available from OneCall.com for US$599. I p;an on keeping my RSW-15 and possibly adding another Klipsch sub like the RT-12d or RSW-15 or 12. TheEAR definitely needs at least one of these. He could EQ all three RSWs at one time. Bill Quote Link to comment Share on other sites More sharing options...
fabulousfrankie Posted January 10, 2006 Share Posted January 10, 2006 I just set mine up yesterday, this thing is really awesome. I didn't have much time, but in all of 5 min I'm at +/- 4dB. I still can't believe I ever used to use excel and my SPL meter while adjusting my BFD(it took forever!!!). Initially I was frustrated, but I later found I had a defective mic. By sheer luck I happen to own the Behringer ECM8000 mic which seems to be the exact same mic. I can now get rid of my BFD and my SVS black box now that I have the subsonic filter in the Velo piece. Besides the low bass sounding better, all other notes seems to carry just the right amount of weight. BTW, there is suppossed to be a software update that will allow adjustments down to 5Hz coming in February. Quote Link to comment Share on other sites More sharing options...
ToxicMule Posted January 11, 2006 Share Posted January 11, 2006 I have a RSW-15. What kind of rolloff did you notice below 30? Quote Link to comment Share on other sites More sharing options...
MrMcGoo Posted January 11, 2006 Author Share Posted January 11, 2006 The RSW-15 in a corner does not roll off much untill below 25 Hz. At 22 Hz and below it is down10 to 12 decibels. Human hearing is very poor that low unless the sound is extremely loud. Most subwoofers in commercial theaters roll off rapidly below 30 Hz. Bill Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 11, 2006 Share Posted January 11, 2006 Sounds like you've got some room issues around 22Hz because the RSW-15 really doesn't roll off that early. And btw, the fact that your sub is rolling off that fast and that human hearing is less sensitive in that region doubles the "badness" of your situation - in other words, our less sensitive hearing isn't an excuse that it isn't that audible. I would be curious to know what kind of EQ this processor is implementing. I have no doubt that it doesn't improve the sound, but it seems to me like it is the wrong tool for the job? I would really like to see some parametric EQ's that work in the time domain (perhaps that even do some signal processing with the phase to help tame room resonances)....you know, something like a reverb effect that is gated, delayed and out of phase. Quote Link to comment Share on other sites More sharing options...
sfogg Posted January 11, 2006 Share Posted January 11, 2006 " I would really like to see some parametric EQ's that work in the time domain" Do you mean the level of EQ varies with time or that the parametric EQs are based on time domain measurements? For EQ that varies with time Tact room EQ products do this. For conventional parametric EQs that are set based on time domain measurements Lexicon and Meridian's room EQ products do this. Shawn Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 11, 2006 Share Posted January 11, 2006 I'm talking about EQ's that take into account the time-domain / room interaction with the sub. For a simple example, if you have a problem due to a single reflection, then you don't want to compromise the direct sound with your correction of the reflection. People claim that changes in phase for a single sound aren't audible, so why not implement a correction factor that modulates the phase of the direct signal at that particular frequency in such a way as to minimize the reflection issue. I know these kind of solutions become more and more sensitive to the location of the listener, but moderate application to long wavelengths should yield rather decent results - at least I would suspect better than a conventional parametric EQ (which are subject to the same location restrictions). Quote Link to comment Share on other sites More sharing options...
sfogg Posted January 11, 2006 Share Posted January 11, 2006 "I'm talking about EQ's that take into account the time-domain / room interaction with the sub." Tact and Sigtech both do this. "so why not implement a correction factor that modulates the phase of the direct signal at that particular frequency in such a way as to minimize the reflection issue." Do you mean attempt to cancel out the reflection with an out of phase signal? If so that would be *very* position specific and what do you do about all the reflection to the 'correction signal.' Those will bounce around and alter the sound the listener ends up hearing in unintended ways. There is only so much that can be done electronically. Room treatments are far more effective for some things, electronic processing are far more effective for other problems. "to long wavelengths should yield rather decent results - at least I would suspect better than a conventional parametric EQ (which are subject to the same location restrictions). " No, they aren't for long wavelengths. Not when you consider the problem in the time domain and setup the EQ based on measurements in the time domain. Homework.... think about the problem and see if you can figure out that statement. Hint.... is a room amplitude mode (peak/null) the problem itself or a symptom of the problem? If it is a symptom of the problem then what is the underlying problem in the room? Shawn Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 11, 2006 Share Posted January 11, 2006 "Do you mean attempt to cancel out the reflection with an out of phase signal?" No. Let's consider a single reflection that causes a "problem" (doesn't matter what the problem is) at 80Hz and is delayed by 10ms. For all signals with 80Hz material that exist for under 10ms, we don't have to worry about the reflections interaction with the direct sound. But say we have some source material that lasts for 20ms. For the first 10ms the direct sound will be unaffected by the reflection (because the reflection hasn't arrived yet), but after 10ms the reflection can start interfering with the direct sound (depending on the relative phases). However, if we can shift the phase of the direct sound that arrives at the same time as the reflection by 90 degrees relative to the phase of the reflected sound, then we no longer have to worry about the reflection affecting the direct sound. Man that's hard to say...I should probably draw a picture. In essence, you will end up with a system that is continuously rotating it's phase at different rates for each target frequency. And it wouldn't have to be very position specific because the "phase" of low notes changes rather slowly (low frequency means low cycle rate...the sound pressure of the wave changes slowly). For example, room modes with the lower frequencies tend to be many feet apart - not inches like the higher frequencies. And this approach does not require a continuous sound for it to work either...though it gets a bit more complex when you take into account that there are many many different reflections (so it's not really a simple rotating of the phase anymore). I am only talking about the reflected sound interacting with the direct sound...I'm not talking about an electrical means to get rid of reflections - in fact, I would argue that even if it were possibly to get rid of these reflections that it would sound bad. Who knows, maybe an approach like this might be the cure for horn throat reflections too [] Quote Link to comment Share on other sites More sharing options...
sfogg Posted January 11, 2006 Share Posted January 11, 2006 "Man that's hard to say...I should probably draw a picture." Nope, I know what you mean. You mean why apply a correction to the signal before the 'room effect' is kicking in. Say you have 10dB of room boom at 50hz but the room boom lags the direct signal by 10ms. If you just EQ 50hz -10dB then the initial 10ms of playback in the room is going to be -10dB.... but then the room boom kicks in and makes it flat. Again... Sigtech and Tact already do this. Have been doing it for years.... Sigtech has been doing it for at least a decade. That is what FIR filters are all about. In the above example the first 10ms of the 50hz signal would be reproduced without any EQ applied, then they apply -10dB of cut to the signal. The end result is that the direct sound at the listener changes at the same time as the reflection from the room hits you and the room boom is kicking in. One of the problems with that approach is it narrows the sweet spot. Locations out of the corrected area may, and often can, sound worse. And the higher in frequency your try to correct like this the narrower the sweet spot becomes. Shawn Quote Link to comment Share on other sites More sharing options...
MrMcGoo Posted January 11, 2006 Author Share Posted January 11, 2006 Sounds like you've got some room issues around 22Hz because the RSW-15 really doesn't roll off that early. And btw, the fact that your sub is rolling off that fast and that human hearing is less sensitive in that region doubles the "badness" of your situation - in other words, our less sensitive hearing isn't an excuse that it isn't that audible. I would be curious to know what kind of EQ this processor is implementing. I have no doubt that it doesn't improve the sound, but it seems to me like it is the wrong tool for the job? I would really like to see some parametric EQ's that work in the time domain (perhaps that even do some signal processing with the phase to help tame room resonances)....you know, something like a reverb effect that is gated, delayed and out of phase. I remeasured the output at 20 Hz on my RSW-15 in various positions including the corner with the sub. My RSW-15 is down 10-12 decibels in the 20-22 Hz region in all locations. It is rock solid down to 25 Hz. I do not get the fascination with sounds below 30 Hz. The sounds below 30 Hz frequently get drowned out by higher frequencies. Most movies sounds below 40 Hz are from explosions in one form or another. The sub 30 Hz component gets lost in the rest of the sound IMO. The equalization of the SMS-1 is adjustable for the eight frequency bands that the user chooses. The current lower limit is 15 Hz. There may be a firmware update this year that goes as low as 5 Hz. I have to wonder about the utility of equalization that goes below 20 Hz. I also wonder about the accuracy of the mic at frequencies below 20 Hz and suspect that many subs have subsonic filters for sounds below 16 Hz. Bill Bill Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 11, 2006 Share Posted January 11, 2006 I remeasured the output at 20 Hz on my RSW-15 in various positions including the corner with the sub. My RSW-15 is down 10-12 decibels in the 20-22 Hz region in all locations. It is rock solid down to 25 Hz. Still sounds like a room, or even measurement issue. The RSW-15 is 6dB down at 19Hz, corner loaded at 1m in an anechoic chamber. It should actually be louder in a home due to room gain (but this will vary from room to room). Quote Link to comment Share on other sites More sharing options...
MrMcGoo Posted January 11, 2006 Author Share Posted January 11, 2006 My RSW-15 is on heavy carpet with an extra thick pad. I suspect that it may be the culprit. The mic is supposed to be accurate at that frequency, but there will always be some variance from one unit to the next. Bill Quote Link to comment Share on other sites More sharing options...
ToxicMule Posted January 12, 2006 Share Posted January 12, 2006 I'm curious about what degree of rolloff everyone has found. When I bought mine about 3 years ago, I only remember a single review being out. That was on secrets and it showed significant rolloff at 30. In fact I just checked and its still there(subwoofers under the christmas tree), but I cant seem to post the link. When I bought mine, I had capeted floors and sheetrock. I also own RF speakers, and I never noticed any issues. In the last month I moved into a stucco house with hard tile floors. I know there are several other factors, such as room size and shape, yet now I cant get enought low end for movies. If I turn it up(only about half gain)which is about 6-8 db hot with a rat shack meter, then its way too much bass on most things. Just wondering if I got a para eq and turned up the bottom frequencies, would I burn out my amp? Also my speakers sound like garbage now, I really need to get a huge rug for starters. Quote Link to comment Share on other sites More sharing options...
formica Posted January 12, 2006 Share Posted January 12, 2006 The equalization of the SMS-1 is adjustable for the eight frequency bands that the user chooses. The current lower limit is 15 Hz. There may be a firmware update this year that goes as low as 5 Hz. I have to wonder about the utility of equalization that goes below 20 Hz. It actually has a subsonic filter fixed at 15Hz and it filters out everything below that. There has been some talk of this unit on the IB forums, but that fixed filter discourages most of those potential customers. Making it variable can only help sales... BTW, there is a tactile value to the "subsonic" octave... so IMHO a 10Hz filter would have been more appropriate for those with DIY subs... ROb Quote Link to comment Share on other sites More sharing options...
sfogg Posted January 12, 2006 Share Posted January 12, 2006 "It actually has a subsonic filter fixed at 15Hz" Do you know if it is hardware or software? If it is in the DSP they could easily change that if they wanted to. "BTW, there is a tactile value to the "subsonic" octave... so IMHO a 10Hz filter would have been more appropriate for those with DIY subs..." Have you read any of the experiments with infrasound as they relate to haunting? Some interesting theories there in how people react to deep bass. I know I react to infrasound. One time when I was down in the theater I was doing some low frequency sweeps between 10-20hz for testing. When I was finished and had left the theater I realized I was totally wired. It seems the infrasound triggered the 'fight or flee' response in me and I was totally hopped up on adrenaline. That cracked me up once I realized what had happened. Shawn Quote Link to comment Share on other sites More sharing options...
MrMcGoo Posted January 12, 2006 Author Share Posted January 12, 2006 The SMS-1 digitizes the signal so all equalization is run through a microprocessor. Hence it should be easy to implement the lower subsonic filter through a firmware update via the RS-232 serial port. The slope of the subsonic filter is adjustable. It has a range of 6 db per octave to 48 db per octave. Bill Quote Link to comment Share on other sites More sharing options...
formica Posted January 12, 2006 Share Posted January 12, 2006 "It actually has a subsonic filter fixed at 15Hz" Do you know if it is hardware or software? If it is in the DSP they could easily change that if they wanted to It is software... and it's my understanding that it will be updated to "user selectable" down to 5Hz. I guess it's good news for those who were scared away by it. Although I think the SMS is an interesting tool... "ease of use" seems to be it's only advantage over a BFD setup with energy-time measurement. Or did I miss something? Have you read any of the experiments with infrasound as they relate to haunting? Some interesting theories there in how people react to deep bass. Interesting, i can see how a movie could use this to it's advantage... and bring new meaning to a haunting tale. ROb Quote Link to comment Share on other sites More sharing options...
sfogg Posted January 12, 2006 Share Posted January 12, 2006 " "ease of use" seems to be it's only advantage over a BFD setup with energy-time measurement. Or did I miss something?" Ease of use looks like it for now. The upcoming multiple mic setup for it could be interesting but if it ends up just averaging the mics that isn't the best way to do that. As far as ease of use for BFD have you seen this yet? http://homepage.ntlworld.com/john.mulcahy/roomeq/ And it can automatically configure the BFD if you have a midi interface on your computer. I haven't played with the software much yet but want to look into it more. Using decay times (3D) for deciding where to place filters is a better approach then just targetting flat response (2D) IME. I think the SMS is just doing 2D measurements. Shawn Quote Link to comment Share on other sites More sharing options...
formica Posted January 13, 2006 Share Posted January 13, 2006 As far as ease of use for BFD have you seen this yet? http://homepage.ntlworld.com/john.mulcahy/roomeq/ And it can automatically configure the BFD if you have a midi interface on your computer. Yeah, I've been wondering about it as well, as it looks very promising. With my HT construction and part of my existing system disassembled, I haven't had any time to play around with it (or much else). The last time I tried it, it didn't have any energy time measurement capabilities... just single tones. It was mostly useful to allow you to import ETF measurements and calculate BFD filters based on them. I didn't / don't have a midi cable either, but if this does what it claims to... it might be worth getting one. I wonder how it compares to ETF? John, the author, mentioned that he originally used to interface it with ETF, so I'm figuring someone has made the comparison. That little program's capabilities seem to have grown very quickly... looking forward to experimenting with it. Please let me know if you do get around to it yourself, I'd be interested in your impressions. ROb Quote Link to comment Share on other sites More sharing options...
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