Distributed Bass

[newguy1]

Benefits?

Drawbacks?

Personal Experiences?

[RayW]

Originally Posted by newguy1

Benefits?

More uniform bass response throughout the room.

Drawbacks?

Cost.

Personal Experiences?

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.

[dnewma04]

Benefits:

• 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.

Drawbacks:

• 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.

[TerryO]

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.

Best Regards,
TerryO

[Artie]

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.)

Thanks guys.

[newguy1]

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?

[Artie]

Originally Posted by newguy1

For me, I've never really been a bass enthusiast. I do enjoy nice, clean, even levels throughout the spectrum.

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.

[dnewma04]

Originally Posted by newguy1

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.

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.

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".

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.)

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?

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.

[newguy1]

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.

[dnewma04]

Nailed it, newguy1. Ideally, it would be a summed mono signal. A huge majority of recordings take care of this for us, luckily.

[dnewma04]

Originally Posted by Artie

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.

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.

[Artie]

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.

[newguy1]

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?

[Jon_Logan]

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

[TerryO]

Originally Posted by Jon_Logan

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

Jon,

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.

Best Regards,
TerryO