If One Sub is Good, Are Two Better? - Page 4 - AVS Forum
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post #91 of 129 Old 04-17-2011, 06:37 PM
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sometimes a second sub is for a different portion of the frequency response.
other times a second sub is to fill a different area of the listening room.
and if you are on a budget, two weaker subs can reinforce eachother (and that was the pleasure i was talking about)

Let's cut this boulderfarb out. This is plain nonsense.

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post #92 of 129 Old 04-17-2011, 07:37 PM
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Where's the "Euthanize this thread" button?

I feel a genuine sorrow for anyone that came to this thread seeking knowledge or advice. If you have, I emplore you to begin with the documents Dennis provided, and ignore pretty much this entire thread.
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post #93 of 129 Old 04-18-2011, 12:08 AM
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Originally Posted by 4DHD View Post

There has been mention of running all speakers full range. Years ago I did just that. Having 5 identical speakers and 6 subs. The AVR had all channels set to large, with each channel having its own sub. Each of those subs were placed below their respective 3-way tower (24" tall). The sixth sub was connected to the sub out, via coax, and set to LFE only.

The sound was amazing, to say the least.

This sounds like a really good idea, would it be ideal for only certain environments?

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post #94 of 129 Old 04-18-2011, 04:14 AM
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Running all your speakers at full range (assuming they really are full range), will either work wonderfully or fail horribly. The interaction between the LCR speakers and the room boundaries, the physical characteristics of those speakers, and your seating distance(s) are going to dictate the placement of the LCR in order to create the best in room response and provide your soundstage. Your low frequency drivers; however, have their own positioning needs in order to achieve the most consistent bass response at the seating locations. It is very, very rare you find a room where the location of the LCR speakers for the best sound stage and the location of the low frequency drivers to provide the smoothest bass response are the same.

Additionally, there is another issue. I'll use 80Hz as the example for the crossover frequency. At 80Hz, the wave length is 14' ... the 1/4 wave length is 3.5' feet. At 80Hz then, if the speaker is 3.5' from a wall, you'll have a phase cancellation, or notch, at 80Hz (3.5' + 3.5' = 7', or 1/2 wavelength, or 180 degrees out of phase). As a speaker moves closer to a wall, the notch frequency increases. So, with an 80Hz crossover, you move your subs closer than 3.5' from the wall, no notch ... the notch frequency is higher than the sub's highest frequency. As you move your LCR's further away from the wall, the notch frequency decreases ... thus, if your mains are more than 3.5' from a wall, you notch frequency is lower than the lowest frequency being produced by the main speakers.

One point that is missed and messes people up is that at the crossover frequency (80Hz, for example) you sub and main speaker must be in phase. The cross over frequency is the only frequency which is produced by the mains and the subs at the same time and same intensity. Getting that wrong is why many feel something isn't right. As demonstrated in our HAA classes, when it is right, you cannot tell if the sub is on or off.

Here's a teaser .... when you have two subs in a room, they do not behave as two independent speakers ... they behave as if there was only one sub located 1/2 way between the two actual subs.

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post #95 of 129 Old 04-18-2011, 04:49 AM
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Quote:
Originally Posted by Dennis Erskine View Post

Running all your speakers at full range (assuming they really are full range), will either work wonderfully or fail horribly. The interaction between the LCR speakers and the room boundaries, the physical characteristics of those speakers, and your seating distance(s) are going to dictate the placement of the LCR in order to create the best in room response and provide your soundstage. Your low frequency drivers; however, have their own positioning needs in order to achieve the most consistent bass response at the seating locations. It is very, very rare you find a room where the location of the LCR speakers for the best sound stage and the location of the low frequency drivers to provide the smoothest bass response are the same.

Additionally, there is another issue. I'll use 80Hz as the example for the crossover frequency. At 80Hz, the wave length is 14' ... the 1/4 wave length is 3.5' feet. At 80Hz then, if the speaker is 3.5' from a wall, you'll have a phase cancellation, or notch, at 80Hz (3.5' + 3.5' = 7', or 1/2 wavelength, or 180 degrees out of phase). As a speaker moves closer to a wall, the notch frequency increases. So, with an 80Hz crossover, you move your subs closer than 3.5' from the wall, no notch ... the notch frequency is higher than the sub's highest frequency. As you move your LCR's further away from the wall, the notch frequency decreases ... thus, if your mains are more than 3.5' from a wall, you notch frequency is lower than the lowest frequency being produced by the main speakers.

One point that is missed and messes people up is that at the crossover frequency (80Hz, for example) you sub and main speaker must be in phase. The cross over frequency is the only frequency which is produced by the mains and the subs at the same time and same intensity. Getting that wrong is why many feel something isn't right. As demonstrated in our HAA classes, when it is right, you cannot tell if the sub is on or off.

Here's a teaser .... when you have two subs in a room, they do not behave as two independent speakers ... they behave as if there was only one sub located 1/2 way between the two actual subs.

Your second to last paragraph, (I'm on my phone and I don't know how to highlight it), seems like it would be different from what your average person would think. Would it be best to have all bass at the same level coming from all 5 channels plus bass channel? That's what it sounds like, then you wouldn't be able to tell. Most people think of 5 channels with minimal bass(compared to sub) and then the bass channel, much louder. Isn't the bass Chanel mastered in movies in a 5.1 setup suppose to be louder, certain parts of the movie hit louder on that one channel?

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post #96 of 129 Old 04-18-2011, 04:57 AM
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Originally Posted by joeydrunk View Post

This sounds like a really good idea, would it be ideal for only certain environments?

Well, I had a large room, over 3100 cuft, if I had the sliding doors to the dining room closed. If they were open, then over 6400 cuft.
My main L/R were 5 feet from the side walls and 4.5 ft from the end wall. The surrounds were wall mounted, with their subs below.
After about a year, I got tired of looking at 6 subs scattered around the room, so I reduced them to three, leaving the two 15" subs in place with the L/R mains mounted to them.

The soundstage was huge, depending on the recording, sometimes it seemed as if it was wider than the room (17.5 ft) and there was quite a bit of depth to the stage as well.

Here is a pic, when I only had 2 subs, as you can see, the main/sub stacks are well away from the walls.
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post #97 of 129 Old 04-18-2011, 05:03 AM
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Originally Posted by 4DHD View Post


Well, I had a large room, over 3100 cuft, if I had the sliding doors to the dining room closed. If they were open, then over 6400 cuft.
My main L/R were 5 feet from the side walls and 4.5 ft from the end wall. The surrounds were wall mounted, with their subs below.
After about a year, I got tired of looking at 6 subs scattered around the room, so I reduced them to three, leaving the two 15" subs in place with the L/R mains mounted to them.

Do all 6 subs hit the same or do the 5 with there speaker counter parts hit by themselves and then the .1 sub by itself. Or if there was say a bass explosion in the left rear would you just hear it on the left rear sub and the .1 sub, or how does that work.

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post #98 of 129 Old 04-18-2011, 05:16 AM
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Originally Posted by joeydrunk View Post

Do all 6 subs hit the same or do the 5 with there speaker counter parts hit by themselves and then the .1 sub by itself. Or if there was say a bass explosion in the left rear would you just hear it on the left rear sub and the .1 sub, or how does that work.

The 5 channel subs were connected with speaker wires from the AVR and then connected to the PT800s to provide a fullrange combo for each channel.
The sixth sub was doing only LFE duty, connected by coax. So whatever channels had LF that is where you heard it, more/less, bass is omni directional. But any sound effect that was in the .1 channel only came from that one sub, in the front of the room.
I also experimented with subs @ the mid-points of the walls, with very good results.

But like I said, and the pic I show, it was a very large room.
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post #99 of 129 Old 04-18-2011, 07:26 PM
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Originally Posted by stepyourgameup View Post

Dual subs is a must in a typical 20x14x8 room IMO.

That is the size of my room and I own two subs and it is nice, but I did use only one 10" before adding a 2nd and really is a nice add on, but I could live w/o going duals.

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post #100 of 129 Old 04-19-2011, 06:31 AM
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there is zero science to audio.. stating anything other than that is a clear and direct indication of a problem with math.
no different than the forums implied king of respect 'dennis' who gives me an article with headlines that state 'audio science' blah blah blah dont use sound absoprtion (something i already said numerous times).

That is a false statement right there!! Pure and simple.

I'll give you a perfect example of science of audio. Having capacitors in an audio circuit will produce a certain amount of distortion, it is inherent of the component. The reason is that with an audio signal the frequency and voltage is constantly changing. This constant change tightens and loosens the capacitors.

To eliminate that distortion by keeping the caps tight requires adding a small, constant DC bias voltage to the caps. That is done by changing the circuit from single caps, to pairs of caps, in series (cap values then need to be twice the size of that single cap to retain the needed value). The common point of all series pairs are then connected to high ohm resistors (2~6 megohm) with the other ends of those resistors connected to the positive side of a 9v battery, with the negative side to ground.
JBL, and maybe others, have used this science on their high end speakers for 2 decades. I've used it myself on a pair of custom speakers I built in '03.
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post #101 of 129 Old 04-19-2011, 10:26 AM
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I chased balanced, low bass in my listening room for a decade, and, frankly, it was a lot of the pseudoscience and techno-babble evident in this thread that lengthened and frustrated that journey. Do yourself a favor, listen to respected professionals, they'll steer you in the right direction.

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post #102 of 129 Old 04-19-2011, 12:59 PM
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post #103 of 129 Old 04-19-2011, 01:45 PM
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Am I the only one that can't follow this thread anymore? all I hear is yada, yada, yada...

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post #104 of 129 Old 04-19-2011, 05:19 PM
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^They worked when he published them though, that day. At least I'm pretty sure I was able to read the AES ones because I remember thinking when breifly sampling one ( I didn't examine all though), "Wow, how am I able to read this since I'm not a member and don't have clearance?"

In A/V reproduction accuracy, there is no concept of "accounting for taste". We don't "pick" the level of bass any more than we get to pick the ending of a play. High fidelity is an unbiased, neutral, exact copy (or "reproduction") of the original source's tonal balance, timing, dynamics, etc..

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post #105 of 129 Old 04-20-2011, 03:48 AM
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Members are acting as if they learned something. Trouble is 5 of the 7 links don't work! The author is too lazy to see if they work. Any amateur can see the tmpFiles in the path and know they won't work. Obviously this is a setup to drum-up business. AES documents are not free either.
These tactics are heartbreaking.

That really sucks. They worked fine when I posted them.

You should be able to get to the articles by going to www.harman.com. Put your pointer on "Company". On the drop down menu, select "technology leadership". The menu on the left will have Scientific Papers which will link you to the AES papers. The menu item "White Papers" will list some of the other documents.

The copyright issue is outside my control. Even the standards documents and recommended practices documents I've worked on (with others) have copyrights owned by the sponsoring organizations (like CEA, ITU) ... and even I have to pay to get my own additional copies beyond the original.

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The author is too lazy to see if they work.

----Actually I did test them. You're making assumptions which support your vitriol. It would have been just as easy to post "hey...these don't work". The lazy part is an accurate observation since the links were "cut and paste". I was indeed too lazy to type them in one character at a time.
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Obviously this is a setup to drum-up business.

I have no clue how this would, or would not drum up business; but, there are people who are much smarter in marketing than I am and may see this as a great marketing tool. Marketing is not my expertise. It may be obvious to you and isn't to me; but, then I'm not the sharpest knife in the drawer.

Apology accepted.

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post #106 of 129 Old 04-20-2011, 04:48 AM
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Dennis, some on this forum, and other forums, think they have all the answers, when in fact they know next to nothing. Just because some people have strong convictions about a subject doesn't make their thought process right. My GF is like that, at times, and I have to then point out the error of her thinking.

I for one appreciate your input, keep it up.
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post #107 of 129 Old 04-20-2011, 04:51 AM
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Quote:
Originally Posted by 4DHD View Post

Dennis, some on this forum, and other forums, think they have all the answers, when in fact they know next to nothing. Just because some people have strong convictions about a subject doesn't make their thought process right. My GF is like that, at times, and I have to then point out the error of her thinking.

I for one appreciate your input, keep it up.

I agree 100%.

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post #108 of 129 Old 04-20-2011, 05:19 AM
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thread cleanup

I asked a couple of members to leave the thread

If you see a problematic post, please just report
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post #109 of 129 Old 04-20-2011, 07:50 AM
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For those arriving late, several posts were deleted between posts #103 & #104, which explains why the M. Zillch #104 post is confusing, seemingly responding to voices in his own head. You can see some remnants of the deleted posting quoted by Dennis in post #105.

Mourning the disappearing usage of the -ly suffix. Words being cut-off before they've had a chance to fully form, left incomplete, with their shoelaces untied and their zippers undone. If I quote your post (or post in your thread) without comment, please check your zipper.
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post #110 of 129 Old 04-21-2011, 07:43 AM
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Quote:
Originally Posted by 4DHD View Post

My GF is like that, at times, and I have to then point out the error of her thinking.

While I agree with your post in general, I question the effectiveness of this last point! My experience with pointing out the "error in her thinking" has been that it usually reflects back and results destructively as a peak on my head (as opposed to sound where peaks arise from constructive interference?)! And empirical evidence suggests that the peak tends to be more acute the closer I am to her when I vocalize that observation ... really odd ...
So I've resorted to containing these "reflections" within me and not letting them seep out of my mouth - sort of like room treatments to control acoustic interference!! Seems to be working ...

This thread is awesome! Subscribed for the comic relief!
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post #111 of 129 Old 04-21-2011, 11:05 AM
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Originally Posted by Sankar View Post

While I agree with your post in general, I question the effectiveness of this last point! My experience with pointing out the "error in her thinking" has been that it usually reflects back and results destructively as a peak on my head
This thread is awesome! Subscribed for the comic relief!

I knew that would get at least one comment.
Despite the fact my GF has been known to punch out a guy or two, and breaking a tooth while doing it, she has never even thought, much less tried it with me. She will fight with anyone, except me. She starts any ****, I just give it back to her, that shuts her up.
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post #112 of 129 Old 04-22-2011, 07:47 AM
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How about: if one GREAT sub is good, are two GOOD subs better??

I'm deciding whether I should get 1 nice sub that fits my budget or two "medium" subs that fit the same budget. Thoughts?

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post #113 of 129 Old 04-22-2011, 08:32 AM
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Originally Posted by SteroMAdMAn View Post

How about: if one GREAT sub is good, are two GOOD subs better??

I'm deciding whether I should get 1 nice sub that fits my budget or two "medium" subs that fit the same budget. Thoughts?

Short answer, YES.
Using a pair of subs produces a flatter FR across the entire seating area. As opposed to a single sub, that you can locate for a flat FR for a single seat, as for a music only system.
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post #114 of 129 Old 04-22-2011, 08:49 AM
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I'd say it depends on what one's idea of a good/great sub is?

A pair of 8 or 10" subs would be giving up bass extension over single 12 or 15" subwoofer.

I went for a great sub, and later added a second. Not that I needed bass extension or SPL. The second was for smoother response and coupling for better placement options.
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post #115 of 129 Old 04-22-2011, 09:22 AM
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Quote:
Originally Posted by Tedd View Post

I'd say it depends on what one's idea of a good/great sub is?

A pair of 8 or 10" subs would be giving up bass extension over single 12 or 15" subwoofer.

I went for a great sub, and later added a second. Not that I needed bass extension or SPL. The second was for smoother response and coupling for better placement options.

One needs to compare apples to apples, as in the same size drivers. Also, as was mentioned days ago, if a sub bottoms out at 25 htz, adding 3 more is still only going to give you 25 htz. But you will get better FR over the entire seating area, as you say.
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post #116 of 129 Old 04-23-2011, 04:12 PM
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This room is 25 x 25. Two subs do a pretty good job.

Sub 1: Velodyne SPL-1000 Series 1
Sub 2: SVS PB13-Ultra.

The 65" Pany looks small.

Scroll your window horizontally.



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post #117 of 129 Old 04-23-2011, 05:44 PM
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Originally Posted by xavier311 View Post
I use two subs for the same reasons listed above.
I have a relatively large living room with a tall ceiling.
One sub is located front right of the room while the other sits right behind the main couch.
One added benefit to this set ups is that I can "feel" explosions, gun shots, etc. making movie watching way more fun.. and all with zero distortion
I am really inspired........ Thanks for the post

Wide LCD or Projector
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post #118 of 129 Old 05-02-2011, 06:03 PM
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Quote:
Originally Posted by Dennis Erskine View Post

Here's a teaser .... when you have two subs in a room, they do not behave as two independent speakers ... they behave as if there was only one sub located 1/2 way between the two actual subs.

I have two subwoofers, located symmetrically on the left and right sides. After running a sweep and find my room modes on a waterfall, I ran sine waves, walking around with the SPL meter to "map" the modes in my room. I have no appreciable lateral modes to deal with (but plenty fore-aft!), presumably due to exactly this phenomenon that Dennis mentions.

I'm not sure why I have none, because I think theoretically one sub in the middle should excite even-order modes, but I have read on an acoustics forum before that symmetrically located subwoofers eliminate all modes in the direction between the subwoofers. It could be that those people were wrong, more likely I'm guessing that Dennis' assertion is only a portion of the story. I have admittedly not read into the links that Dennis provided, but I do have my experience to relate.

Logically, I think it is reasonable to make the extension that eight subwoofers placed symmetrically would eliminate all or most modal issues (if the assertion of "all modes" falls through and it really only deals with the odd order modes) in a rectangular room. I'll definitely keep that concept in mind if I ever build my dream / mega theatre. Though I suppose one giant sub with its acoustical center in the center of the room (in all three dimensions!) would achieve the same thing at lower cost.

On to the links!
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post #119 of 129 Old 05-02-2011, 06:25 PM
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Quote:
Originally Posted by Dennis Erskine View Post

So, for you, here's your reading assignments, and then, once your homework is done, we can start.

You _can_ find them via the second method Dennis mentioned, but for convenience here are working links for the numbered papers:
http://www.aes.org/e-lib/download.cf...86&name=harman
http://www.aes.org/e-lib/download.cf...06&name=harman
http://www.aes.org/e-lib/download.cf...79&name=harman
http://www.aes.org/e-lib/download.cf...04&name=harman
http://www.aes.org/e-lib/download.cf...80&name=harman

These are to the URLs where the Harman website points.
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post #120 of 129 Old 05-02-2011, 09:33 PM
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Three subs placed assymetrically, (staggered unequally in the room) are best to reduce standing waves and provide "bass imaging" and increase headroom and bass you can feel. In a tri-sub system, the LFE is more dedicated to the munition fire, space shuttle, 50cal bass. The the left and rights provide bass AND bass imaging.

Pls.visit my good fren Steve Bruzensky's home theater and see his three subs placed right:

http://www.avsforum.com/avs-vb/showthread.php?t=1158431

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