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Are three inexpensive subs better than one expensive sub-Dr. Earl Geddes Approach - Page 3

post #61 of 2011
I wish I could still find it but about a year back I saw this post on Engadget I think, of this one guys house. When I have my own house and enough money (hah) I plan on doing something similar.


http://www.switched.com/2008/07/21/w...est-subwoofer/

I want that =(

And well, this is always fun to look at http://blog.audiovideointeriors.com/208great/

My vote goes for 3 expensive subs?
post #62 of 2011
Quote:
Originally Posted by penngray View Post

Im not trying to game the debate, your post on the first page using that amp/driver example suggests that its a solution for any of us but in reality from what I read is that it only works great in your room because your room and treatments improve it to the Nth degree.

Would it be fair to say that your room has a HUGE impact on the performance of your "cheap solution"?

No, I wouldn't agree to that. I've done several rooms and they all work well, some better than others. The use of multiple subs is universal, the number and power level depends on the room. The more damping that you have the easier it is to get a good response with fewer subs, but tends to require higher power. The smaller and better sealed the lower the power. There are a lot of variable, but the contention that it only works in my room because of the room is simply not true.
post #63 of 2011
Quote:
Originally Posted by TurboTalon View Post

And well, this is always fun to look at http://blog.audiovideointeriors.com/208great/

My vote goes for 3 expensive subs?

It isn't necessary to be rich to have a great system. I'd put mine up against any at any price and it was quite cost effective. Thats the point here. The major manufacturers would have you believe that price equates to quality - well it doesn't.
post #64 of 2011
Quote:
Originally Posted by gedlee View Post

I don't think that time alignment at LF has any significance. At 50 Hz. it takes almost 40-50 ms. for the brain to even register that a tone at this frequency is present. What kind of sensitivity could a hearing system have to a few ms time alignment at those frequencies.



Time alignment of all of the subwoofers makes all the difference in the world. If not time aligned (phase aligned) the bass from all of the bass drivers can be out of phase (or time).

For that matter if you use multiple & different subwoofers, there is no guarantee that they will be a good phase match either!
post #65 of 2011
Thread Starter 
Quote:
Originally Posted by J_Palmer_Cass View Post

Time alignment of all of the subwoofers makes all the difference in the world. If not time aligned (phase aligned) the bass from all of the bass drivers can be out of phase (or time).
!

time aligned and in phase-everywhere in the room-one seat, two, more?
post #66 of 2011
Quote:
Originally Posted by gedlee View Post

I addressed this already, but "meaningless" is a bit extreme. Lots of people have done multiple subs and as far as I know all have found it an improvement. Does the LF absorption in my room affect my results - absolutely - is this the dominate factor - absolutely not.


I have a feeling your room setup is a large factor in the quality of the sound. Maybe some buddys of your can come over and audition their subs in your room, to see just how much better their sub sounds there vs at their own house.

Setting up people rooms to be more friendly is where the big bang for the buck comes in once you have a decnet driver/drivers in the mix.

I'd love to hear 4 tuned DD-18s in your room all eq'd in with their software.
post #67 of 2011
For a specific example that probably applies to many people here:

If you had one PB13 ultra and wanted to add aditional subs that could be placed around the room, 1 PC13 Ultra -Or- 2 PC12 Plus's??
post #68 of 2011
Thread Starter 
Just FYI, here is a link to Earl's credentials (as well his wife's). Earl has his PHD in acoustics and his wife in Audiology.

http://www.gedlee.com/Principles.htm
post #69 of 2011
Quote:
Originally Posted by Randybes View Post

Just FYI, here is a link to Earl's credentials (as well his wife's). Earl has his PHD in acoustics and his wife in Audiology.

http://www.gedlee.com/Principles.htm

The in your face question has to be....how does someone emerse themselves in this field only to join avs forums 2 months ago??? So come on now...what is gedlee's previous name on the forum. You guys can't be serious that a "family" this involved in music would not be on this board for their phd journey. Something is up. Could we have some kind of history please? This would be the real credentials I would think.
post #70 of 2011
Quote:
Originally Posted by simplemath View Post

The in your face question has to be....how does someone emerse themselves in this field only to join avs forums 2 months ago??? So come on now...what is gedlee's previous name on the forum. You guys can't be serious that a "family" this involved in music would not be on this board for their phd journey. Something is up. Could we have some kind of history please? This would be the real credentials I would think.

There are MANY audio professionals with credentials such as Dr. Geddes that are not members of these forums.
post #71 of 2011
Too bad some people like to talk too much and don't know how to listen.
post #72 of 2011
Quote:
Originally Posted by simplemath View Post

The in your face question has to be....how does someone emerse themselves in this field only to join avs forums 2 months ago??? So come on now...what is gedlee's previous name on the forum. You guys can't be serious that a "family" this involved in music would not be on this board for their phd journey. Something is up. Could we have some kind of history please? This would be the real credentials I would think.

Being an AVS Forum Member is *not* a prerequisite for a PhD.
post #73 of 2011
To take my comments about tripping over avs after a massive carer studying this stuff is silly. I suppose no one else is thinking the same thing? or maybe they are...it is a simple question. And to add. with 10k and 11k posts you 2 do a lot of talking i'd say.

If it is rude to question the words that is being written by someone doing that much talking...well who do you expect to listen to you?

Dance around the question all you want....you are not telling me anything I did not allready know. SO go roll eyes with some content.
post #74 of 2011
Dr. Geddes,

Could you please explain the technique you use to set up your subs, especially the gains and phases? There was a thread awhile back about different setup techniques in which another member described yours. I would just like to verify that he got it correct. I'll look for and post the previous thread.

Craig
post #75 of 2011
Quote:
Originally Posted by simplemath View Post

To take my comments about tripping over avs after a massive carer studying this stuff is silly. I suppose no one else is thinking the same thing? or maybe they are...it is a simple question. And to add. with 10k and 11k posts you 2 do a lot of talking i'd say.

If it is rude to question the words that is being written by someone doing that much talking...well who do you expect to listen to you?

Dance around the question all you want....you are not telling me anything I did not allready know. SO go roll eyes with some content.

Why do you give so much import to these forums? And my comment was not directed at you.
post #76 of 2011
Quote:
Originally Posted by simplemath View Post

The in your face question has to be....how does someone emerse themselves in this field only to join avs forums 2 months ago??? So come on now...what is gedlee's previous name on the forum. You guys can't be serious that a "family" this involved in music would not be on this board for their phd journey. Something is up. Could we have some kind of history please? This would be the real credentials I would think.



post #77 of 2011
Quote:
Originally Posted by craig john View Post

Dr. Geddes,

Could you please explain the technique you use to set up your subs, especially the gains and phases? There was a thread awhile back about different setup techniques in which another member described yours. I would just like to verify that he got it correct. I'll look for and post the previous thread.

It was DS-21 who posited and elaborated upon Dr. Geddes's method(s). HERE is the thread. It was a very good discussion.
post #78 of 2011
Here's the other thread:
http://www.avsforum.com/avs-vb/showt...1068195&page=2

Post #42 by DS-21 is the one I was referring to.
post #79 of 2011
Quote:
Originally Posted by craig john View Post

Here's the other thread:
http://www.avsforum.com/avs-vb/showt...1068195&page=2

Post #42 by DS-21 is the one I was referring to.

Yes, that one, too. And maybe more so than the other thread I linked. This thread is what prompted me to start the "other" thread. Both threads were eye(ear)-openers for me.
post #80 of 2011
Maybe some people think AVS is more prominent and important in the world of home theater than it really is? Is Floyd Toole a regular contributor or member here? What about Thom Holman? I believe both Henry Kloss and Wilbur Klipsch were alive and active during the existence of AVS, I don't recall them being contributors?

While there seems to be a great deal of focus on the quality of Dr. Geddes room as impacting the response, you have to understand that one of the major benefits of the multiple subs around the room is that it corrects for the problems caused by the room. Even those of us without good dedicated rooms will benefit from this, probably more so. Then again, there isn't any other way to skin this cat (Smoothness spatially and amplitude).

We should differentiate time alignment and phase here. While technically the phase adjustment is making a time adjustment, What Dr. Geddes advocates is adjusting the phase. A wave could be in phase but not in time if the time difference was large enough, many many ms's for instance. So keep in mind that when doing this, phase adjustment of the subs is very important to achieving smooth response. However, if somehow you managed to get the subs a full 10ms off, the phase adjustment wouldn't correct for this, but you could still phase align the soundwave enough for a smooth response. While it will have an impact on the smoothness of the response, I think Dr. Geddes was trying to say that you wouldn't hear it as a delay until the delay exceeds 40-50ms.

While we all are very proud of our very expensive high excursion subwoofers, keep in mind that "max spl" is a somewhat relative term, and most of these subwoofers are very inefficient, Dr. Geddes are actually quite efficient (The ulf probably isn't). An 18" or 15" B&C LF driver is capable of well in excess of 120db's from 50hz on up. If you have 2 of these, they will match or exceed plenty of systems using a similar number of TC Sounds or Whatever brand 30mm xmax subs, in that range. Where things would change I suspect is below that 50hz point. Displacement becomes pretty important at those frequencies, and I would suspect that where the high xmax subs would begin to outdo Dr. Geddes subs is in that range. But then, does it matter? With regard to the majority of the bass range (say 40-150hz), we have plenty of output and a very smooth response, and this is likely to be the most audible area to get right. How loud your "sub" bass is will probably be a matter of choice, and you can buy as many ULF's subs or build as many High xmax subs for this range as your heart desires. While I'm sure you can still have improvements from multiple ULF subs (of whatever design you choose), I don't suspect that it's as important (though shear output might).

Ok back to the quality of the sub question. If a company other than Dr. Geddes was to produce the subs using identical woofers, cabinets, and even amplifiers, they would cost a lot more than 300 dollars. They maybe don't need to (Even he will be selling them for 4-500), but they would. The cost of the drivers he uses would be in excess of 200-400 dollars for us (The 18" I think retails for 450), so these are not cheap drivers. The reason for the amps is because the high sensitivity and lower xmax means the driver will hit it's mechanical limits with a lot less power, but that doesn't mean less output. I can only guess at the particulars of Dr. Geddes alignment, but my models suggest that the 15" B&C driver in a bandpass box would produce 120db's from 50-150hz with just a few hundred watts, but would exceed xmax with any more than 300 watts. By comparison my TC driver needs 1500 watts to do the same thing. Since Reference levels dictate 115db's from 30hz to 80hz (the assumption is that it's smooth and even there), I would say that Dr. Geddes approach is a much simpler and more economical way to actually achieve those levels than one or two large very high powered subs. The only area where I would concede that a traditional large x-max low sensitivity driver makes more sense is in trying to achieve 115db's below 30hz, where box size will largely not allow a high sensitivity version.
post #81 of 2011
Quote:
Originally Posted by craig john View Post

Dr. Geddes,

Could you please explain the technique you use to set up your subs, especially the gains and phases? There was a thread awhile back about different setup techniques in which another member described yours. I would just like to verify that he got it correct. I'll look for and post the previous thread.

Craig

I second it. If i read one of his post correct phase (timing) is not important when running multiple subs.
Thx pjpoes for the phase explanation.
post #82 of 2011
Quote:
Originally Posted by pjpoes View Post

While there seems to be a great deal of focus on the quality of Dr. Geddes room as impacting the response, you have to understand that one of the major benefits of the multiple subs around the room is that it corrects for the problems caused by the room.

Yep. That is one of the main points if not THE main point.
post #83 of 2011
Thread Starter 
Quote:
Originally Posted by simplemath View Post

The in your face question has to be....how does someone emerse themselves in this field only to join avs forums 2 months ago??? So come on now...what is gedlee's previous name on the forum. You guys can't be serious that a "family" this involved in music would not be on this board for their phd journey. Something is up. Could we have some kind of history please? This would be the real credentials I would think.

I made him aware of this forum (and hope I don't have to regret that) and invited him to participate after I picked up the speakers I bought from him and listened to his room. He knows many in the industry. He was most recently on a panel discussion with Floyd Toole, Sean Olive, at an Alma seminar. Something is not up other than a little too much value placed on a come one come all forum with some good stuff, but a lot of "noise" as well.


http://www.almainternational.org/membershipcat.php
post #84 of 2011
Quote:
Originally Posted by archer101 View Post

I second it. If i read one of his post correct phase (timing) is not important when running multiple subs.
Thx pjpoes for the phase explanation.

What Geddes said specifically was "I don't think that time alignment at LF has any significance." Time alignment and phase though related, are not interchangeable. I've never heard him or anybody say correct phase was not important.
post #85 of 2011
Quote:
Originally Posted by Randybes View Post

I made him aware of this forum and invited him to participate after I picked up the speakers I bought from him and listened to his room. He knows many in the industry. He was most recently on a panel discussion with Floyd Toole, Sean Olive, at an Alma seminar. Something is not up other than a little too much value placed on a come one come all forum with some good stuff, but a lot of "noise" as well.


http://www.almainternational.org/membershipcat.php

Thanks man
post #86 of 2011
Quote:
Originally Posted by gedlee View Post

Lets consider "best" here to be quantitative to get away from the subjective. The sound field in a room at LF is highly variable in space and in frequency. "Best" then means the smoothest in both of those aspects. I don't think that anyone could effectively argue that a highly resonant spatially variable bass is what we want, and if they did then this is not the place to be since the underlying assumption in all that's said here is that smoothness is king.

I think it is very important to note that Dr. Geddes's (and DS-21's) highest priority is smoothness of response. I assume his primary usage is musical reproduction. If this is also *your* priority, then Dr. Geddes's approach of 3 lesser subs and his setup techniques may be the "best". However, if high output and deep ULF response, (down to and below 20 Hz), is *your* priority, especially for Home Theater applications, then other setup techniques will optimize those capabilities better.

For example, due to the fact that the gains are set differently, Dr. Geddes's approach will limit the max output capabilities of the higher-set sub and/or under-utilize the capability of the lower-set sub(s). In a music-oriented system, 105 dB from 25 Hz up may well be sufficient, and should be easily do-able with 3 lesser subs, even with their gains set differently. However, in an HT system where Reference Level of 115 dB from below 20 Hz is desired, the full dynamic output capability of all the subs in the system will be required, and better subwoofers will always be beneficial.
_______________________________________________

Dr. Geddes, have you ever used an Audyssey-enabled receiver or pre-pro? I would be interested in your thoughts on the frequency and time-based EQ capabilities of Audyssey MultEQ XT.

Craig
post #87 of 2011
Quote:
Originally Posted by mojomike View Post

What Geddes said specifically was "I don't think that time alignment at LF has any significance." Time alignment and phase though related, are not interchangeable. I've never heard him or anybody say correct phase was not important.

right on. So if the time is close enough that the ear can not perceive it, it will not muddy the sound. Yet the phase must be spot on or the waves will create unwanted audible "I'll call it warbles"

Can the phase be adjusted by ear, or does Geddes rely on instruments? I know from work, it is astounding what the ear can do when it comes to phase matching/tuning with electricity.
post #88 of 2011
Thread Starter 
One thing I wanted to comment on and it is subjective, but the wow thing with Dr. Geddes room was the integration of the bass with the mains. It was seamless. Typically, what I hear in a room is some transition between the mains and the subs. Even with full range speakers, I find that they seldom are seamless in any but a few spots in the room.
post #89 of 2011
Thread Starter 
Quote:
Originally Posted by craig john View Post

In a music-oriented system, 105 dB from 25 Hz up may well be sufficient, and should be easily do-able with 3 lesser subs, even with their gains set differently. However, in an HT system where Reference Level of 115 dB from below 20 Hz is desired, the full dynamic output capability of all the subs in the system will be required, and better subwoofers will always be beneficial.
_______________________________________________


Craig

You may have a point (on below 20Hz-I am not sure that is super important to him)... but we listened (and watched) the recent Cream DVD at very loud levels. Jack Bruce was pretty much there in the room as far as I could tell. I also have to say that Earl and his wife watch as many movies as I do which is about 10-12 a week. It was gratifying for me to see someone who actually uses their system. I know people who obsess over their system but never even use it that much except to critique it. Kind of sad really.

My priority is working toward the smooth transition mentioned above with less seat to seat variation. I have heard the rotary sub twice and while it is interesting, I am not going for detecting structural weakness in my home. Others may differ and I know there is content in the very low range in some movies; however, it just does not seem all that prevalent to me (and I have 2 JF113's as well as SVS Utra cylninder sub, Salk Songsub and a couple of others) and what is perceived as bass generally is higher up in the spectrum than most think. Yes, I know you can feel it and your pants legs and all that stuff.
post #90 of 2011
Quote:
Originally Posted by goonstopher View Post

For a specific example that probably applies to many people here:

If you had one PB13 ultra and wanted to add aditional subs that could be placed around the room, 1 PC13 Ultra -Or- 2 PC12 Plus's??

He would very most likely say neither.
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