ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1]   Go Down

Author Topic: Another Spaced Sub Question - (Sorry)  (Read 2130 times)

Paul Knowler

  • Newbie
  • *
  • Offline Offline
  • Posts: 8
Another Spaced Sub Question - (Sorry)
« on: March 12, 2018, 09:37:28 pm »

Hi all,

Any help will be much appreciated.

I intend to use the option of 3 subs spaced at under 2/3 wavelength but wonder if this will cause some direction/steering issues (apologies if terminology is not quite correct).

Can I also ask is it ok if the subs are not all evenly spaced so long as we don't reach the 2/3WL tipping point?

Also I understand (from a Sound on Sound article) that if only using one sub then 2 full range cabs on poles can be treated as the 2 outside subs again eliminating cancellations, is this correct.

How important is level matching the sound sources?

Last question - if there is still bass above the crossover point of say 100hz at which point does it become less of a problem for cancellation (again I've read somewhere that the 2 separated sources of higher frequencies are less of a concern/less noticeable for cancellation.

I do understand that I am looking at this from an over simplified point of view and also I should probably explain that my interest in this configuration is from an aesthetics point of view, getting the best sound out of it once it looks good is a more personal mission.

Sorry for all of the questions - thanks in advance.   
Logged

Scott Holtzman

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 4958
  • Ghost AV - Avon Lake, OH
    • Ghost Audio Visual Systems, LLC
Re: Another Spaced Sub Question - (Sorry)
« Reply #1 on: March 13, 2018, 12:08:10 am »

Hi all,

Any help will be much appreciated.

I intend to use the option of 3 subs spaced at under 2/3 wavelength but wonder if this will cause some direction/steering issues (apologies if terminology is not quite correct).

Can I also ask is it ok if the subs are not all evenly spaced so long as we don't reach the 2/3WL tipping point?

Also I understand (from a Sound on Sound article) that if only using one sub then 2 full range cabs on poles can be treated as the 2 outside subs again eliminating cancellations, is this correct.

How important is level matching the sound sources?

Last question - if there is still bass above the crossover point of say 100hz at which point does it become less of a problem for cancellation (again I've read somewhere that the 2 separated sources of higher frequencies are less of a concern/less noticeable for cancellation.

I do understand that I am looking at this from an over simplified point of view and also I should probably explain that my interest in this configuration is from an aesthetics point of view, getting the best sound out of it once it looks good is a more personal mission.

Sorry for all of the questions - thanks in advance.

Are all three the same?  Why would you gain them different?  do two subs provide enough output?   The third really isn't getting you much.  You have to double the number of subs to get a noticeable difference.  I: 1 to 2, 2 to 4, 4 to 8

Logged
Scott AKA "Skyking" Holtzman
River Delta Audio is now:

Ghost Audio Visual Solutions, LLC
Cleveland OH
www.ghostav.rocks

Gordon Brinton

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 460
  • ID Verified
    • Raw Depth Sound, Harrisburg, PA
Re: Another Spaced Sub Question - (Sorry)
« Reply #2 on: March 13, 2018, 12:37:31 am »

I tend to ignore wavelength/spacing recommendations because every note of every song could conceivably end up being at different frequencies. Depending on what is being sent to my subs, (Bass guitar, kick drum, low notes from keys, synth, guitar, or vocals,) lower overtones can vary wildly. There is no simple way to calculate optimal distance based on 100 or more different frequencies in the sub range. You can only calculate it based on your most dominant frequency. If, for example, kick drum is the loudest thing playing in your subs, then figure out which frequency is most inportant to you and concentrate on that alone.

Going beyond that, all subs sound different from one another. Some bring out higher tones better while others do lower tones better. Depending on your brand and model, logical real-time experimentation is the only way to discover what your subs are better at. (Upgrade considerations are always an option.)

Then to really throw a monkey wrench into the mix, every venue causes your subs to behave differently. You may think that you have the best subs in the world, but you can't always space or locate your subs where you wish. Sometimes your hands are tied with poor location and you simply need to learn how to EQ things to maintain control or at least to avoid disaster.

Many of us old-school sound guys have learned to sound check our rooms using a well known CD or mp3 song. We tweak in our subs using our ears and learned judgement. (Often times, I start by muting my subs and bringing my tops up to expected volume levels. Then I turn up the subs until things sound relatively balanced...that is, the right amount of bass compared to the tops. When old faithful sounds decent, it may not be perfect, but at least it is a rational starting point.) When, during the show, most channels in the mixer sound right without heavy EQing, then I feel that I have it right.

Last, but not least, every room attempts to ruin our mix with their unpredictable nodes and nulls. You're going to have hot spots and dead spots no matter where you stand or how you slice it. As soon as you have it sounding good at the mix position, walking the room deflates your ego and reveals the nasty that is reality.

Next, I believe that bass extends somewhat above my crossover point, (120Hz in my case). For example, I EQ an electric bass guitar to use more frequencies between 120 and 500 Hz than below 120. Thus, my top cabinets carry more bass guitar than do my subs. Albeit, my subs do provide some depth and fatness for the bass.

I guess what I am saying is, it all depends. There are so many variables that no one can give you solitary advice to make improvements. You simply have to learn to do that yourself through experience.

Good luck and don't give up. Running sound is delightful when you get things working right...or should I say, right enough.
Logged
Member since 2005.

Paul Knowler

  • Newbie
  • *
  • Offline Offline
  • Posts: 8
Re: Another Spaced Sub Question - (Sorry)
« Reply #3 on: March 13, 2018, 01:53:00 am »

Are all three the same?  Why would you gain them different?  do two subs provide enough output?   The third really isn't getting you much.  You have to double the number of subs to get a noticeable difference.  I: 1 to 2, 2 to 4, 4 to 8
Hi Scott,
Thanks for your reply.  Maybe if I worded the different gain question was just a bit of a random thing really. To put it another way if there was an inadvertent variation of gain in one of the subs, let's say the middle one how much variation can there be before we lose the effect of the that sub preventing cancellation, this would also answer the question of 'if there were 2 subs each side and only one in the middle would the lobing become present again' (I think I know the answer to that one already but it's always good to ask)?
The idea of 3 subs is just to provide even coverage without power alleys and valleys by keeping spacing under 240 degrees phase offset.
The subs would all be the same and there is no reason why it couldn't be 4 subs, the only thing I can't do is centre cluster, I don't want to go for just a sub stack each side because of those alleys and valleys.
Logged

Paul Knowler

  • Newbie
  • *
  • Offline Offline
  • Posts: 8
Re: Another Spaced Sub Question - (Sorry)
« Reply #4 on: March 13, 2018, 02:12:04 am »

I tend to ignore wavelength/spacing recommendations because every note of every song could conceivably end up being at different frequencies. Depending on what is being sent to my subs, (Bass guitar, kick drum, low notes from keys, synth, guitar, or vocals,) lower overtones can vary wildly. There is no simple way to calculate optimal distance based on 100 or more different frequencies in the sub range. You can only calculate it based on your most dominant frequency. If, for example, kick drum is the loudest thing playing in your subs, then figure out which frequency is most inportant to you and concentrate on that alone.

Going beyond that, all subs sound different from one another. Some bring out higher tones better while others do lower tones better. Depending on your brand and model, logical real-time experimentation is the only way to discover what your subs are better at. (Upgrade considerations are always an option.)

Then to really throw a monkey wrench into the mix, every venue causes your subs to behave differently. You may think that you have the best subs in the world, but you can't always space or locate your subs where you wish. Sometimes your hands are tied with poor location and you simply need to learn how to EQ things to maintain control or at least to avoid disaster.

Many of us old-school sound guys have learned to sound check our rooms using a well known CD or mp3 song. We tweak in our subs using our ears and learned judgement. (Often times, I start by muting my subs and bringing my tops up to expected volume levels. Then I turn up the subs until things sound relatively balanced...that is, the right amount of bass compared to the tops. When old faithful sounds decent, it may not be perfect, but at least it is a rational starting point.) When, during the show, most channels in the mixer sound right without heavy EQing, then I feel that I have it right.

Last, but not least, every room attempts to ruin our mix with their unpredictable nodes and nulls. You're going to have hot spots and dead spots no matter where you stand or how you slice it. As soon as you have it sounding good at the mix position, walking the room deflates your ego and reveals the nasty that is reality.

Next, I believe that bass extends somewhat above my crossover point, (120Hz in my case). For example, I EQ an electric bass guitar to use more frequencies between 120 and 500 Hz than below 120. Thus, my top cabinets carry more bass guitar than do my subs. Albeit, my subs do provide some depth and fatness for the bass.

I guess what I am saying is, it all depends. There are so many variables that no one can give you solitary advice to make improvements. You simply have to learn to do that yourself through experience.

Good luck and don't give up. Running sound is delightful when you get things working right...or should I say, right enough.

Hi Gordon,

Thanks for your reply too.

I hear what you are saying when you say 'right enough' and so many times I have read lately how sound is a big compromise, more than I have ever realised.  Having said that I have worked with average kit and had it sound great and great kit but been defeated by the environment. 
In reply to your feelings on not going with the wavelength separation option, I was of the understanding that if separated below 240 degrees phase offset of the highest frequency below the crossover point then bass would be more likely to behave itself and not gather for a party in the alley. 
It sound like you would not agree with that statement?
I guess what I'm looking for is a toolbox of different options that I can use, this is the first one I want to get my head around and best to be forearmed with a bit knowledge before I try to put it into operation.
Logged

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 8661
  • Atlanta GA
Re: Another Spaced Sub Question - (Sorry)
« Reply #5 on: March 13, 2018, 07:34:17 am »

Hi all,

Any help will be much appreciated.

I intend to use the option of 3 subs spaced at under 2/3 wavelength but wonder if this will cause some direction/steering issues (apologies if terminology is not quite correct).


Generally 1/4 wavelength (or less) of the highest freq of interest is the goal to avoid interactions.

If you have larger spacing than that, you will start to have interactions.

How much depends on a number of factors: the actual spacing vs freq, the number of cabinets, any response differences etc.

Sound systems are the fine art of compromise.

You cannot get everything correct, so you try to understand the compromises, decide what is best for a particular situation and live with it.
Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Steve Garris

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1152
Re: Another Spaced Sub Question - (Sorry)
« Reply #6 on: March 13, 2018, 03:10:22 pm »

Generally 1/4 wavelength (or less) of the highest freq of interest is the goal to avoid interactions.

If you have larger spacing than that, you will start to have interactions.

How much depends on a number of factors: the actual spacing vs freq, the number of cabinets, any response differences etc.

Sound systems are the fine art of compromise.

You cannot get everything correct, so you try to understand the compromises, decide what is best for a particular situation and live with it.

Just so that I understand this, let's say we want 63 Hz to be free of cancellations. The wavelength is 17.86 ft, divided by 4, giving me about 4-1/2 ft. Is that the spacing between the centers of the sub cabinets? I know for this purpose we are ignoring boundaries.

What is meant by "the highest freq of interest"?

Logged

Paul Knowler

  • Newbie
  • *
  • Offline Offline
  • Posts: 8
Re: Another Spaced Sub Question - (Sorry)
« Reply #7 on: March 13, 2018, 04:08:54 pm »

Generally 1/4 wavelength (or less) of the highest freq of interest is the goal to avoid interactions.

If you have larger spacing than that, you will start to have interactions.

How much depends on a number of factors: the actual spacing vs freq, the number of cabinets, any response differences etc.

Sound systems are the fine art of compromise.

You cannot get everything correct, so you try to understand the compromises, decide what is best for a particular situation and live with it.
Thanks Ivan, I have read everywhere that 1/4 wavelength is the limit.  My confusion I think comes on an earlier post where Merlijn stated

"Coupling occurs up until 120 or 1/3 wavelength of phase offset. This is the milestone of no gain / no loss (illustration 3). Beyond this point losses will occur.  The first lateral spurious side-lobe occurs when the physical spacing exceeds 240 or 2/3 wavelength of phase offset with a (far-field) magnitude equal to those of the individual sources (illustration 4).  To avoid one ore more spurious side-lobes, which make up for the alternating pattern of power-alleys and power-valleys, keep the physical displacement between the subwoofers equal to or less than 2/3 wavelength of the upper frequency limit of the intended operational bandwidth."

However looking at the plot Merlijn posted I'm guessing my misunderstanding is more in the terminology than the science as to me it looks like anything over 90 degrees starts to show a narrowing in the coverage and anything above 120 degrees seems to narrow the coverage enough to be undesirable (unless that's what you are aiming for I guess).
http://forums.prosoundweb.com/index.php?action=dlattach;topic=157886.0;attach=15954;image
« Last Edit: March 13, 2018, 05:07:21 pm by Paul Knowler »
Logged

Paul Knowler

  • Newbie
  • *
  • Offline Offline
  • Posts: 8
Re: Another Spaced Sub Question - (Sorry)
« Reply #8 on: March 13, 2018, 04:10:30 pm »

Just so that I understand this, let's say we want 63 Hz to be free of cancellations. The wavelength is 17.86 ft, divided by 4, giving me about 4-1/2 ft. Is that the spacing between the centers of the sub cabinets? I know for this purpose we are ignoring boundaries.

What is meant by "the highest freq of interest"?
Highest freq of interest is that at the crossover point, I read another article where they based calculations just slightly above the crossover point just
to be sure.
Logged
Pages: [1]   Go Up
 


Page created in 0.042 seconds with 19 queries.