Discussion in 'Speakers' started by newguy1, Apr 5, 2010.
More uniform bass response throughout the room.
Been in a room (ballroom at a trade show) with 6 (!) Contrabass subs. When someone came in with a 24/96 recording of a space shuttle launch it was hard to breathe.
Reduction of significant peaks and nulls in the modal region
Better integration with the mains
Less expensive method of reaching the best bass performance in a given room
You can avoid expensive processing
Distributing the bass serves to reduce the duty on each sub, generally resulting in lower distortion due to more linear operation.
The reduction in duty can lessen the requirements for superior performance. The need for exotic motor systems is reduced.
Subjective preferences may go against their use.
For best results, you'd need to have measuring equipment to pull off the best results. A mic, an FFT analyzer and a few hours to spend would be the minimum requirements.
In conjunction with the above, traditional placement methods may not result in the best performance.
At the risk of going slightly off topic...
I'll give some more thought to the drawbacks, at first glance, I was tempted to say there weren't any. But, I realize that not everybody has the time, patience, equipment or desire to learn how to properly implement an optimum bass solution. There are subjective preferences based on listening experiences that can significantly bias people against subwoofers as a whole, or various methods of implementing them. There are distinct biases for and against every type of cabinet, cone material, voice coil winding material, magnet material, etc. Misconceptions rule the roost.
Distributed bass systems are very well recognized to work well in most rooms.
My personal experience involves 4 rooms using distributed bass.
1.) My own system experimentations.
2.) Geddes' system
3.) Two systems of friends of mine I've convinced to try it.
In addition, I have convinced 7 other audio friends to attempt it but haven't heard their systems first hand. 3 live on continents I've never visited, the 4 others live in distant states.
Also, there are a number of threads on the internet where people have properly implemented distributed bass systems based on JBL/Harmans, Welti's, or Geddes' system and I have yet to find anyone who has attempted it that didn't prefer the results with at least 3 subwoofers.
For me, hearing the differences was an eye opening experience and a bit of a Eureka moment. I have always been a fan of subwoofers, but had a love hate relationship with them because of the room integration issues that are involved with them. I built my first home subwoofer using an Avatar Audio Shiva in a critically damped sealed box. At my listening position, I was able to dial it in nearly perfectly. There were no apparent weaknesses in the integration between satellites and subwoofers, nothing ever drew my attention away from the mains towards the subs. However, even a slight move from my listening position and all hell broke loose with the sound. The integration i struggled to achieve in one location was all but destroyed over the matter of inches. Having someone come over and sit anywhere but the sweetspot left people with the impression I didn't have a clue on how to integrate the sub.
I then moved up to stereo subs using another Shiva in the same critically damped alignment. I was a believer, stereo bass was the way to go. I was able to get signicantly better bass with a pair of stereo subs in addition to the mains than I was with just the mains.
When I started reading Geddes' recommendations for adding a third sub, I also found the other documents and started playing around with options. Having as many as 5 subwoofers installed in my system at times with the two mains and sometimes in 5.1 mode. It was then that I discovered that the reason stereo bass performed so well is because of the second sub, not because of the fact that they were "stereo".
Each additional sub added, up to the 4th, there was a noticeable improvement. The improvement wasn't a matter of output, it was an improvement in perceived imaging. Soundstage solidified, perceived dynamics increased, measured distortion dropped, musicality of the subwoofers increased significantly. Instead of hearing the limitations imposed by no subs, one sub, or stereo subs (which at one point, I didn't feel existed until I learned more and listened more).
The ultimate implementation of distributed bass I've heard was obviously Geddes' system. Within a few seconds of listening to his system, it's obvious that his system works and works absolute wonders. With surprisingly small investment, he has created a system that likely rivals the best in the world. there is no apparent weakness. Tonality, imaging, soundstage, etc remain constant while moving around the room. Bass depth and musicality is unparalled in any systems I've heard. The number of systems I've heard is vast, back prior to getting married, I regularly traveled around the Midwest to various audio get-togethers, shows, etc and got to hear some excellent systems. Since I've been married, that has obviously slowed, but over the course of the last 10 years, I've had the privilege of hearing some of the best systems I've heard. Over the course of 20 years in the hobby, I have had just about everyone of my misconceptions shattered with experience. The distributed bass methodology is probably the latest one in a long list.
Dave and Ray,
I completely agree with your comprehensive analysis of the pros and cons of Distributed Bass. The first inkling of what DB was capable of, that I'm aware of, was when Dan Wiggins started advocating (on the old Bass List) staggered positioning of subs to quell the modes that are present in any room. Subsequently, Earl Geddes devoted a fair amount of time, effort and thought to actually bring the theory and practical application a lot further along, as well as coining the term: "Distributed Bass."
One thing that people should be aware of is that with multiple subs, each sub driver has less demands being made upon it, IOW: less power handling. It's also entirely possible, through series/parallel wiring, to use a minimum number of sub amplifiers. For the same (or less) amount of money of a TOTL commercial subwoofer, a person could construct an entire DB system which would deliver far superior results.
There's still one question about D-bass that I haven't seen the answer to: Do all the subs get the same signal, (mono, I presume), or would you do a left/center/right arrangement? (Assuming 3 subs.)
For me, I've never really been a bass enthusiast. I do enjoy nice, clean, even levels throughout the spectrum.
I have probably never heard a well implemented DB system, which is probably why I lean to a single sub system. Each system that I have heard that has multiple low end drivers (these were not as nice as what dnewma04 has heard...) has always sounded fat and uncontrolled to me.
My understanding that was that the bass wasn't necessarily better with multiples, only that it was better distributed. Also, I remember reading that the subs should be different, for example, a 10", 12", and 15".
So what are different crossover methods to the multiples? Is it best to run a single crossover to all subs? To crossover each one by itself? What order works best?
More or less, me too. I like a nice tight, punchy bass. I hate "boom". My main interest in the D-bass system is that its something new to try. Could be fun to experiment with.
I suspect you are right, it would be easy without a mic and an established measurement methodology to get a serious boombox factor going. When setup properly, the front sub in one of the corners will be providing a majority of the output, the second sub will be producing a significant portion and the third sub should be difficult to hear, it's output will be well down from the other two.
I have found that a significant amount of the "better" portion of better bass is implementation. DB systems with their more evenly distributed bass makes the task of integration easier to optimize. As far as the use of multiple sizes, it's not something I've seen referenced in any of the white papers, threads, etc that I've run across. That doesn't mean that someone out there doesn't prescribe your method, I'd have to give some thought as to the reasoning. Off the top of my head, I suppose you could justify something of the sort in the Gedlee method where the three subs have different output requirements. The largest sub being used for the front corner loaded, the 12" for the side sub with lower output and 10" for the rear with the least strain put on it.
It could save some money in certain circumstances (where output requirements were high enough that the Gedlee prescribed 10" sealed/ported sub would be strained and at the same time, there was a premium being placed on space and budget.)
I think the crossover options are largely open to interpretation. In Geddes system, he feels it's important to ensure that the mains and subs are overlapping or you aren't getting the full effect. He uses bandpass subwoofers and might even tune them differently to deal with specific room modes. I'd have to ask for sure on his setup. I believe the use of bandpass subwoofers is to acoustically filter out any high frequency artifacts that might be caused by resonances in the cone, harmonic issues, or the like.
Just missed Artie's post. Good question, and I think that the answer would be a summed signal. (someone please correct me if I am wrong)
When the higher harmonic frequencies are being transmitted from the appropriate location (L/C/R), your brain automatically will place the matching frequencies at the location of the higher. Most of the time, I believe that what is coming out of the sub woofer is the lower harmonics of a note anyway, so the bulk of the sound is coming from the main speaker(s).
An easy way to describe this is a bass gutiar playing a low E (41.2hz). A good portion of the signal will be transmitted to the mains because of harmonics of that frequency. I believe that that note has a potential for harmonics up to 1 or 2khz depending on the style of bass played. For that note, the sound will contain 41, 82, 123.6 (the main note) and harmonics of 165 and 206hz.
Your brain will still associate the bass to the speaker it was mixed in because of these secondary frequencies.
Nailed it, newguy1. Ideally, it would be a summed mono signal. A huge majority of recordings take care of this for us, luckily.
In the end, this is what it's all about for most of us. When you set your sites on something like a 2k-5k subwoofer (or significantly more), DB systems become difficult to justify. It's when you hear three $500.00 subs walk all over something like a JL Audio Fathom or a giant horn subwoofer that you start to realize that everything you've learned might not be enough. In some ideal world where money will eventually be no object for me, I'll be using IB subs to create my DB system. 4 15" woofers per subwoofer location, three locations, one in the ceiling, two in the floor. Prior to hearing DB systems, my dream was always a massive IB setup after installing one with 8 15" woofers in a friends ceiling (roof of boom) and then later installing 4 15" woofers in a HT stadium seating riser.
Thanks guys. You've really covered all my questions well. I think I can make an informed decision now. For the moment, I'm thinking of including two of the woofers into the main speakers, (more or less, like a conventional stereo pair), then perhaps, add a "floating" third. Could be cool.
Sounds like a nice roof of boom!
Once I start completing my theatre, I am thinking to incorporate a riser with subs in it. Did that work well in that application?
I concur with what has been said. more med quality is better than one supreme quality etc. Unfortunately, bass properly implemented has a generally super low WAF, unless your wife is an acustics engineer. Sometimes you have to con(vince) her before placing one sub. To add more boxes later is sketchy.. I'd love to have multiples of some specialized motor foofers though....ie Aura 1808's:drool:
It might be advisable to buy a plane ticket for your wife to visit someone she hasn't seen for awhile (Mom, sister, brother). Then install your DB system using ceiling and floor IBs with the appropriate grills or other methods to hide the subs while she's gone. Most women (OK, at least one that I know) don't like the mess of construction projects or the "clutter" of several subwoofer cabinets in "their" house.
I know that I like to use brackets often, but Jon's "con(vince)" is the best use of them that I've seen in a long while!
I run one cheap KHL HT sub for a long time and assumbed it to be good. Then on of the SMAC guys brought his DIY sub to my house for a SMAC meeting. That really opened my eyes. Just going from one crappy sub to one good one made a huge diff. Then, after conversations with Dnewman, I built two subs and put them in the corners behind my main speakers. WOW! when before with just the one good sub, I would sit in my listening chair (I got luck here) and the signal was good....detailed to every note, great integration.... and all the other good stuff. But if I sat in the chair to the right of me, there was virtually note sub signal and if I sat in the chair to the left, the signal was overwhelming. When I put the two subs in, the signal really flattened out throughout the room. I used the standared issue bio-audio measuring system and knew there was still highs and lows, but not as bad. Then I put two cheap HT subs in the back corners and it was flat anywhere I walked about the room. I am a big fan of DB.
If I might chime in, having a distrubuted bass system is not hard to accomplish as I have installed hundreds of distrubuted audio systems before. Most all of them have been in commercial applications but it is not any difference than what would be done in a home application except you probably wouldn't need near the number of bass drivers. You can do it using that approach that a previous member posted, the series parrallel method, but that is really not nessasary. The most easy way the the most common way would be to use a distrubution amp using a 70 or 100 volt output and a stepdown transformer on each driver. Those tranformers have multiple tap ratings which you can choose from which gives you a choice of wattages that will allow you to either increase some areas spl levels or lessen them in other areas. You can use as many drivers on the line as you wish as long as your total wattage on the line doesn't exceed your amps output. So say you want bass drivers distrubuted thoughout the room, and you use a 800 watt amp per channel you can each channel would allow you to tap the drivers at 200 watts each. Which trust me is very high. Most of the applications we might tap the bass drver at 50 watts and than tap the mid-hi drivers at say 10 watts per driver using a seperate amp for them so you can set the levels on the amps to get your balance and then you use your processor (preamp) to control the audio volume. Using an active crossover with a time delay you they control the phase alignment so that you get a good balanced sound where all the audio fequency's arrive together. The best method is to try and have the bass drivers as close to or near the mid-hi drivers. If you want your bass in 2 channel you use the two channels of the bass amp, which is fed by the active crossover in your audio processor, or some of the amps themselves have programmable modules which you can set the range of frequency that they amplify. So say you feed that amp the output signal from a preamp and you have set your amplifier to only amplify the range from 10 to 200 hz that is all the amp will send out to the bass drivers, left channel to the drivers on the left of the room, and right channel to the right of the room. Or you can just do it in mono which to be honest is what the majority of applications use. So in the ceiling or walls what ever you wish you would mount your recessed bass drivers and then a recessed or if you prefer surface mount drivers in clusters near each other all fed by two amps how ever many channels you want as some of the amps might have 8 channels of output at 70 or 100 volts, and each channel has attenuators which you can control the output levels to get everything balanced and then you control the whole system off the master volume output. It really is very easy. JBL, EAW, Bose, all make contractor versions of speakers, which already have the transformer with multi tap settings just for Distrubuted audio systems. Or like I said you can make your own using your existing speakers all you have to do is buy a tranformer and put it right before the speaker
Bump for visibility purposes on a very important subject.
Only if people actually read and understand.
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