rear sub

[Guest]

<font color='#000000'><table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE">The reason I was propagating the use of rear sub is because of compensating for using a small bookshelf speaker to preserve logistical sanity. &nbsp;</td></tr></table>

To be utterly simplistic, a rear sub is not necessary in this example, and provides no specific benefit (detrimental in most cases), except that you seem to want to &quot;propagate&quot; it's importance.

If you like the way it sounds that's fine, I just want other forum members to be aware of all the issues with regards to your opinion.</font>

 

[Yamahaluver]

<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>

Bruce : <font color='#000000'><table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE">The reason I was propagating the use of rear sub is because of compensating for using a small bookshelf speaker to preserve logistical sanity.  

To be utterly simplistic, a rear sub is not necessary in this example, and provides no specific benefit (detrimental in most cases), except that you seem to want to &quot;propagate&quot; it's importance.

If you like the way it sounds that's fine, I just want other forum members to be aware of all the issues with regards to your opinion.</font></td></tr></table>
<font color='#0000FF'>Let the others be free to experiment as I have and come to their own conclusions. Why prevent them from doing so if they have the means?</font>

 

[gene]

<font color='#000000'>Guys, normally I don't interject on our forums as I feel people contributing on our forums don't need constant babysitters to moderate like some other audio forums. &nbsp;However, when personal attacks take over the actual discussion, I feel it is appropriate to interject as the debate has outlived its usefulness and usually only degrades to further insults and offense to both parties, as well as the readers. &nbsp;At this time, I would ask for both parties to limit this debate to the topic at hand and refrain from further insults.

For the record, I am not a degreed Physicist and have only my EE background as well as my hobby reading on this topic to voice my perspective. &nbsp;From my experience, implementing multiple subs in a home theater system can be very challenging. &nbsp;I have usually discovered better results by placing the multiple subs at a common location. &nbsp;Based on my subjective DBT listening tests, I believe I can localize a bass source if it is located behind the listening position and crossed over above 60Hz (24dB/Octave filter). &nbsp;This is why I have my sub located at the front of my room and crossed over at 60Hz. &nbsp;Also, there is something to be said about using multiple bass sources to average out room response. &nbsp;That being said, I have found that when using large main tower bass capable speakers, coupled with a very musical and capable sub, crossed over below 80Hz, I can usually average out room response better than setting the main speakers small, or not using a sub at all. &nbsp;

I still cannot get rid of all the nulls in my room, since I am limited to placement and room treatment options. &nbsp;This doesn't however deter me from enjoying my equipment, it just leaves the door open for improvement and it has convinced me to build a dedicated home theater room in my next home.

RBH Sound has a pretty interesting solution that I may review in the future. &nbsp;It's their new T3 speaker system that sandwiches two active subs between each main speaker. &nbsp;They claim this will help average room response and eliminate most nulls. &nbsp;I will have to hear it to believe it. &nbsp;

RBH Sound T3

Bruce, you seem quite knowledgeable about the physics of sound, perhaps one day, time permitting, I will share with you my measured room response and you could offer suggestions. &nbsp;

Yamahaluver, you seem to have a good knowledge base that like me, helps me to configure a system as best as possible given the constraints I previously mentioned.

Bottom Line:
I am not a big fan of multi sub systems, and feel they usually perform best, and are easiest to set up, when placed at a common point. &nbsp;I am more than satisfied with setting my rear speakers to small and letting my sub handle the rest.

I hope we can all continue this discussion with more civility. &nbsp;What do you say guys? &nbsp;I don't want to loose either of you as members as a result of this disagreement.

</font>

 

[Guest]

<font color='#000000'>Gene,

You're on, I only want to help people find and discover information that helps them decide for themselves what sounds best.  For those who are new to audio/HT it can be confusing, and we should try to make it easy for them to understand.

There are generally accepted guidelines we can all follow, but in the end you do what makes you feel good. &nbsp;It's best if you have as much information as possible to make an informed decision.</font>

 

[Yamahaluver]

<font color='#0000FF'>No hard feelings then, I too appreciate Bruce's knowledge in Physics but have learned to go by my gut instinct rather than theory when it comes to sound. Being a researcher myself, I have learnt that nothing can be considered the absolute truth and in life that is even more applicable.

I have got a lot to learn from you Bruce so as Gene suggests, lets call a truce if you are willing.

My point in this is why then do manufacturers insist on option of rear Large and high power for rear?</font>

 

[Guest]

<font color='#000000'>A truce sounds good to me.

<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE"> . . . why then do manufacturers insist on option of rear Large and high power for rear?</td></tr></table>

I'm not sure I follow which manufacturers you mean.  If you are referring to SACD/DVD-A, the problem is basically we're forced to use analog outs from the players with poor to no bass management in the signal path (from either the player or the HT processor).  So, the manufacturers take the easy way out and specify full-range for all channels with SACD/DVD-A, pretty lame in my book.  I think they should get their act together and finish a digital link - protected if necessary.

If instead you are just referring to manufacturers allowing you to set rears to Large, well then that is just an option like everything else.

Since I prefer 2-channel for my music consumption, I tend to ignore the multichannel music setups anyway.

IMO, most of 5.1/7.1 systems are designed to accomodate the normal-sized HT rooms found in many homes (&lt;4000ft3), with 90% not able to really fit large floorstanders all around.  This is why smaller monitors are popular for HT systems and the reason bass management (with re-directed bass) is necessary.

Not many speakers are truly full-range anyway. &nbsp;To be called full range they would need to hit 105dB down to 20Hz at the listening position (not many if any truly fit this bill). &nbsp;The multiple sources of bass would be very difficult to balance-out without wide peaks and dips in bass response, unless you had unlimited funds to acoustically treat the room.</font>

 

[Yamahaluver]

<font color='#0000FF'>Bruce,

Majority of HT receivers have LARGE settings for their rear speakers and some in their manuals advice to use full range towers for rears.

The point is that if the rule of non directional bass is so rigid, why even incorporate the option and also, why the need for higher wattage.

For stereo, I have a Accuphase CDP connected directly to my Yamaha MX-1000U power amp and listen them through a pair of NS-1000x speakers. There are no pre-amps in this equation and no tone controls either. Just pure sound from the components in the chain.

</font>

 

[Guest]

<font color='#000000'><table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE"> Majority of HT receivers have LARGE settings for their rear speakers and some in their manuals advice to use full range towers for rears.</td></tr></table>

I agree, most (All?) HT processors (receivers and prepros) offer the Large settings.  

In all the manuals I've read, Meridian, Theta, Outlaw, Rotel, and Fosgate, among others, none have ever advised using Large rears in typical HT rooms.  They offer the setting because in a &gt;10,000ft3 room you are much less likely to experience bass standing wave problems (or space problems either) and you could actually take advantage of large speakers all around.


<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE"> The point is that if the rule of non directional bass is so rigid, why even incorporate the option and also, why the need for higher wattage.
</td></tr></table>

They incorporate the option because some users may actually have &gt;10,000ft3 rooms.  

Bass frequency reproduction always draws more power from the amplifier than higher frequencies.  That big and heavy bass driver motor assembly takes more power to drive than a tweeter or mid-range driver.  So if the speaker can reproduce low bass frequencies it will draw more power. &nbsp;Which means it needs an amp with higher power ratings to keep from clipping.</font>

 

[Yamahaluver]

<font color='#0000FF'>Bruce,

One of the reasons I put the subs in the back was for the exact resons you describe above, to prevent the amp from being used up for bass signals. Also, my bookshelf were sounding taxed even when they were set to Small as there is lot of high &gt;90Hz mid bass component. When using DSP with music mode, there was quite a few times, the woofer seem to be bottoming out. Now all those problems are gone. One question for you, even though there is a general consensus that bass below 90Hz is non directional, would you prefer situation in the movie where a gun is fired in the back to come from the front.

Also in the Yamaha receivers and amps, there is BOTH setting for speakers and this effectively puts all the bass component to the sub and the main speakers simetaneously. Yamaha recommends this in case one has good floor standers and a high powered main amp. I keep my settings at that and get massive amount of SPL which after all is the WOW! factor in a typical HT. HT and DSP never stood for pure accurate sound so if novelty is what we want, we have to divert a bit from accuracy, it is a trade off of some sorts but one that sure makes you feel good. Yamaha's advice is to use same type of speakers for main and surround, only the front surround are recommended to be smaller. Since I have their full size front speakers and centers, it is near impossible for me to puit the same in the back, thus I decided to add the subs in addition to the subs I have in the front. My sub volumes are set pretty low to avoid the dreaded clash with the one in the back.

I do have fair amount of sound proofing done near the three subs I have and there is a good amount of standing wave breakers like heavy sofas and draperies all over the room and the room has no back wall.The ceilling too is peaked. One of the reasons I guess, I havent had bad audible results with three subs.</font>

 

[Guest]

<font color='#000000'>Yamahaluver,

Every room is different, so it's hard for me to comment on your specific setup without actually being there.

I can only offer a few thoughts.

One of the reasons for using prepros and external amps (or receivers and external amps) is to get away from the fundamental limiting factor of a receiver, smaller amps/channel.  Personally, I like at least a 1.6 kVA Toroid power transformer and at least 100,000 µF of power supply filter capacitance which won't fit in a receiver chassis.


<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE">One question for you, even though there is a general consensus that bass below 90Hz is non directional, would you prefer situation in the movie where a gun is fired in the back to come from the front.</td></tr></table>
If you were to use an acoustic analyzer to detect the frequency of a gunshot, I think you would be surprised to find out that it's mostly composed of non-bass frequencies, probably higher than 200Hz.

<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE">Also in the Yamaha receivers and amps, there is BOTH setting for speakers and this effectively puts all the bass component to the sub and the main speakers simetaneously </td></tr></table>
Yes, many receivers have this setting, but unfortunately this setting really exacerbates the standing wave problems (multiple sources of the same bass frequencies) tending to become the dreaded  &quot;boomy&quot; (modal peak) one note bass.

<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE">. . .HT and DSP never stood for pure accurate sound . . .</td></tr></table>
You are quite correct, as DD and DTS are lossy-based  formats that compress the source signal by actually taking away original signal content.

<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE"> My sub volumes are set pretty low to avoid the dreaded clash with the one in the back.</td></tr></table>
If they clash, then that is probably a good example of bass modal peak constructive interference.  Do you set the rear sub's phase switch to an opposite 180 degree phase setting from the sub in the front?  

<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE"> I do have fair amount of sound proofing done near the three subs I have and there is a good amount of standing wave breakers like heavy sofas and draperies all over the room </td></tr></table>
To be even minimally effective in the bass frequency region (&lt;150Hz), sound proofing needs to be a minimum of 6 inches thick.  So heavy sofas qualify here, but not drapes.

<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE">. . .  I havent had bad audible results with three subs.</td></tr></table>
I can't argue with your satisfaction of your current system setup, but I think you would be quite surprised at a bass frequency response graph of your system from your listening position.  It would clearly identify the modal peaks and dips in your multiple sub setup.</font>

 

[Yamahaluver]

<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>

Bruce : <font color='#000000'>One of the reasons for using prepros and external amps (or receivers and external amps) is to get away from the fundamental limiting factor of a receiver, smaller amps/channel.  Personally, I like at least a 1.6 kVA Toroid power transformer and at least 100,000 µF of power supply filter capacitance which won't fit in a receiver chassis.

My MX-1 and MX-1000U Yamaha amps qualify in that criteria pretty well. Both of them have two 750VA transformers and 100000 pico farads of capacitance.





Yes, many receivers have this setting, but unfortunately this setting really exacerbates the standing wave problems (multiple sources of the same bass frequencies) tending to become the dreaded  &quot;boomy&quot; (modal peak) one note bass.


I can't argue with your satisfaction of your current system setup, but I think you would be quite surprised at a bass frequency response graph of your system from your listening position.  It would clearly identify the modal peaks and dips in your multiple sub setup.

As I have no back walls in my room, the reflection part is solved to a great extent. My rooms is constructed of solid bricks with marble flooring.

In the end, my experiment works out for me. When I get some time, I will do an in depth frequency analyisis and post the results.</font>

<font color='#0000FF'>

</font>

 

[Guest]

<font color='#000000'><table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE"> As I have no back walls in my room, the reflection part is solved to a great extent. </td></tr></table>

I say this in gest,  

  you mean your room is open to the outside?  

Actually, all openings in your room that lead to other parts of your house have an influence on the size of the room that bass frequencies work in.  

I mean that if you don't actually have an acoustically sealed room, then the bass frequencies will reflect off the parallel surfaces and out those openings --helping to eliminate some of the standing wave problems.

Think of standing waves like waves you can cause with your hand in a bathtub.  The bathtub is small and the waves easily bounce off the sides of the tub and collide with each other.  Those waves exactly in-phase double their size, those exactly out-of-phase cancel each other out.  If it was an outdoor pool instead (like a much larger room), it's likely the wave you make with your hand would never get back to you at all.</font>

 

[Khellandros66]

<font color='#000000'>I beleive a rear sub sounds like a nice idea, but what about colliding wave patterns? &nbsp;if you want two subs use them in the front of the room, this creates a more open soundstage in the sub 100Hz range. &nbsp;Plus it is far less directional.</font>

 

[Guest]

<font color='#000000'>

When I said no back walls, I meant that there are no walls behind the rear speakers or sub like the tradational HT setup where the rears are mounted on the wall. One of the reasons the rears get a bass boost which is not available to me.

Khellandro 66, I do have two similar subs in the front apart from the rear.</font>

 

[Guest]

<font color='#000000'>Just as a matter of interest, with the Linn Classik Movie system, when using the Classik HT speakers (Uniks + Afekt sub), Linn recommend setting the rears to 'Large' because they are considered to be 'full range' at 80Hz-20KHz +-3dB. Obviously they can't reproduce the lower bass effectively, hence the Afekt sub fill-in, but presumably it is thought that the Uniks' performance will not be significantly impaired by handling full range input. Conversely, there will be little low bass interference distortion from the single sub (recommended to be placed near a front speaker). The amp outputs and the sub can support pass-through from sub to rears, but it isn't recommended, and in my experience the relatively limited low bass performance of the Uniks is still sufficient to be superior in the recommended configuration without severe standing wave problems. However, I am using Katans as a front pair, which do contribute more bass than the Uniks... Even so, I find that room configuration (doors open/shut, curtains open/closed, etc) has far more audible effects in the low bass than switching from the 'Large' rear configuration to the 'Small' one...</font>

 

[Yamahaluver]

<font color='#0000FF'>Just wanted to add that the past week I have gone through ten movies with a mix of Pro Logic and DTS and can tell you that they put significant amount of bass on the rear channels. However when there is bass component in the rear, there is usualy nothing in the front or at least there is a delay of sorts. In my case, the results have been more than satisfactory and I for one have had no bass wave collison problems. Now I can hear the thunder or gunshot in the rear or in the front. The directionality has improved greatly when the rear sub is enabled and the rear speakers are set to LARGE.

Sorry for bringing the ghost back but had to post my observations.</font>

 

[Guest]

<font color='#000000'><table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE"> I for one have had no bass wave collison problems</td></tr></table>

Just an observation:

The only true way to verify this would be to perform a frequency analysis.  The ear simply isn't going to be able to accuractly tell you which frequencies are getting constructive reinforcement and which frequencies are getting destructive reinforcemnt.

It may sound OK to you, but that still doesn't mean standing waves aren't causing bass wave collisons which are heard as bass peaks and dips at very specific frequencies at specific locations in the listening room.</font>

 

[Guest]

<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>

Bruce : <font color='#000000'>.

It may sound OK to you, but that still doesn't mean standing waves aren't causing bass wave collisons which are heard as bass peaks and dips at very specific frequencies at specific locations in the listening room.</font>

<font color='#000000'>Hi Bruce,

As I mentioned, standing waves are broken up by carefuly placed wave breakers and I dont think that DTS/Pro Logic gives bass to both front and rear channels at the same time.</font>

 

[Guest]

<font color='#000000'><table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE">As I mentioned, standing waves are broken up by carefuly placed wave breakers  </td></tr></table>
Could you tell me a little more about &quot;wave breakers&quot;, as I'm unfamiliar with them?  Are these what are commercially referred to as bass traps? &nbsp;Do you use more than 4, one in each corner?

<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE">. . . I dont think that DTS/Pro Logic gives bass to both front and rear channels at the same time.  </td></tr></table>
By definition, DTS (and DD5.1) are full range in all 5 speakers plus a 0.1 LFE channel.

Are you speaking about Dolby PrologicI or Dolby PrologicII?
Essentially both are forms of matrix decoding used on 2-channel sources to simulate 5.1, but I thought the surrounds in PrologicI were bandwidth limited.</font>

 

[Guest]

<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>

Bruce : <font color='#000000'>Could you tell me a little more about &quot;wave breakers&quot;, as I'm unfamiliar with them? &nbsp;Are these what are commercially referred to as bass traps? &nbsp;Do you use more than 4, one in each corner?


By definition, DTS (and DD5.1) are full range in all 5 speakers plus a 0.1 LFE channel.

Are you speaking about Dolby PrologicI or Dolby PrologicII?
Essentially both are forms of matrix decoding used on 2-channel sources to simulate 5.1, but I thought the surrounds in PrologicI were bandwidth limited.</font>

<font color='#000000'>Bruce,

As I mentioned before, I am using heavy sofas as my home made wave breakers or bass traps, whichever way you would call them.

I mentioned DTS as well as Dolby Pro Logic, my observation is that at no time do the recoding engineers feed simeltaneous bass signals in all the five channels so the delay helps offset the bass collison.</font>