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Sound up close vs. on the dance floor

Discussion in 'Amps and Cabs [BG]' started by dwynsen, Dec 9, 2000.


  1. dwynsen

    dwynsen Guest

    Aug 31, 2000
    Ohio, USA
    I've recently returned to playing the bass after many years on the guitar. I have what might be a stupid question. In the absence of a soundman, are there any GENERAL rules of thumb regarding how I should set my volume and EQ so I don't rearrange all the furniture in any given club setting? It seems to me that if I set my volume and EQ to my liking (and the band's liking), I am overpowering 50 feet away. I'm in a blues band and we all like the bass to be low and rumbling. I play a 5-string thru a 1000 watt head, a 4x10 and a 1x18. Thanks for the help.
     
  2. MikeyD

    MikeyD

    Sep 9, 2000
    The other night I played a gig in a "shoebox" shaped room with low ceilings. My Carvin rig was in the corner, and I suspected the bass would be boomy out in the room. I was right. After the initial sound check, some people on the opposite short wall told me everything was shaking like crazy. I used the graphic EQ on my R1000 head to notch down the lowest bass a bit to fix the problem. I also turned down the volume a bit. What's important to note here is that the on-stage mix did NOT sound that great to me because of these adjustments - I was having some difficulty hearing myself. However, what's more important is how it sounds to the audience. That takes precedence. I got reports later that it sounded great out there, even though I wasn't thrilled with the on-stage sound. In my view, this was a successful set-up.

    I've heard many, many situations in difficult rooms where bass players' rigs sound awful because they haven't adjusted to the rooms' acoustics. It's either too dead out there - or more often - way too boomy, especially in "live" spaces.

    - Mike
     
  3. pkr2

    pkr2

    Apr 28, 2000
    coastal N.C.
    dwynsen:
    I haven't been able to come up with any "rule of thumb". There are so many variables with setting the sound level on the bass that it's mind boggling.

    We usually try to get the sound set up well before time to play. The problem being that the acoustics in the room change as the room fills up. What sounds perfect in an empty or not very crowded room can sound weak in a crowded room.

    I have had better luck by asking a couple of people in different parts of the room to give me feedback during performance with simple hand signals. I've found that asking someone who doesn't play to be more reliable than asking another musician. Guitar players want to hear lots of guitar in the mix, while bassists want to hear all bass. The average listener wants to hear a well balanced setup.

    I guess the best way to get the ideal level would be to listen from the audiences position, while using a wireless system.

    From what a lot of posters on this forum say, the proper setting is wide open anyway. It still amazes me how many otherwise good musicians have no idea how important balance is to the sound quality.

    One of my pet peeves is when a musician spends time setting all the channel levels and then before the first song is done he's cranking the volume control up and the whole mix goes down the drain. :)


    Pkr2
     
  4. thats a hard one, you could have someone play your bass to et an idea but the of course there attack won't be the same i used to play thru a laney with 2 15 inch speakers and one night i played a gig thru another bass players amp and thought i sounded like crap (a harke amp with 2 sets of 4 10's stacked) the tens highs on stage killed me but the people one the floor said it sounded great
     
  5. CS

    CS

    Dec 11, 1999
    UK
    I use the external listener thing as mentioned before.

    [Edited by CS on 12-12-2000 at 07:16 AM]
     
  6. Dave S...

    Dave S...

    Oct 13, 2000
    Hopefully I've got this right...

    If you look at your problem (bass sounds great on stage vs. the audience position) then maybe consider some physics...

    At 440hz standard tuning, the 'fundamental' frequency of and open 'E' is about 40hz (there are MANY overtones on top of that at varying freqs...the different freqs give each instrument it's own 'tone.')

    Assuming your amp could actually reproduce 40hz very well...sound travels approx. 1160 feet per second (well, at least at sea level, and with a particular humidity, barometric pressure, etc.) So, if you take 1160 f.p.s. and divide it by 40 cycles per second, you wind up with 29 feet (which, I think, should be the actual 'length' of the sound wave of 40hz!)

    SO, (I am certainly not a physics professor, just a frustrated bass player who has this same problem!) If I understand things right, technically you can't hear the 40hz tones UNLESS you're 29 feet away! (and your amp can move enough air to actually provide an audible tone that far away!)

    It makes sense to me, in that everybody's car with the huge stereo has rumbling bass 3 blocks from your house, but outside your window, you just feel the 'whap!' of the air moving!

    Also, if I understand correctly, part of this is the reason that multiple 10" cabinets became so popular versus folded 18"s and such. The original SVT speakers didn't reproduce much below 125hz or so...which pretty much is the fundamental freq of the 'G' string (if I'm right...) So, the cabinets would reproduce mostly the overtones of the bass, and not exaggerate the fundamental of the G,D,and A strings, and run out of 'ooomph' on the E! So, you wouldn't wind up with "Boom!...Boom!...Boom!... plink!" Basses tended to sound more even through those cabs.

    Also, (by my own 'theory' WHICH SHOULD BE TREATED RATHER SKEPTICALLY! unless someone qualified can confirm it!) if your cabinet didn't reproduce below 125hz, 1160f.p.s. divided by 125hz = 9.28 feet to reproduce the 125hz wave.

    This would mean the full spectrum of your cabinet's sound would be heard at a much closer distance...(and would it also stay more uniform sounding at longer distances, I wonder?)

    Lastly, sound guys seem to hate 18"s and such, because the huge waves they produce tend to scatter and disrupt the air and hence, their vocal and PA mix. A guy explained it to me in these terms: If you took a still pond (air in the room) and sprinkled a bucket full of small pebbles (mid and high frequency waves) in it--and then had some guy come and throw a big boulder in the middle of it (which was supposed to represent the 18") then you can't very well see the ripples from the pebbles anymore...

    10"s are smaller speakers, and don't make as big a wave (which is why you need 4 or more of them!)

    Maybe in the meantime, you could roll off a little of the 40-80hz range, like the other guys said...it may sound funny on stage, but work better out front!

    Sorry this is SO long...reading back, this doesn't sound like the clearest explanation, so I'll apologize in advance...thanks for bearing with me.

    Also, if I'm absolutely wrong, flame away as necessary!

    Best Wishes
     
  7. MikeyD

    MikeyD

    Sep 9, 2000
    Hi, Dave S,
    No flames from me! There is a very well-developed and complicated science which explains this: acoustics. Yes, low E's wavelength is close to 30 feet; however, it can be quite audible at short distances. Ever listened to a pipe organ recording through headphones?? :) The problem I think we're trying to address here has to do with standing waves in a reverberant room. Standing waves result from the air in the room "resonating" at particular frequencies as a result of the shape, size, and reflectiveness of the room boundaries. The problem with bass frequencies (and back to your discussion of wavelength) is that the "nodes" and "anti-nodes" of the standing waves are widely spaced - because of the long wavelengths. What happens is, certain places in the room get the node (almost dead quiet) and other places get the anti-node (huge boom) at that frequency. Then, if you are a listener sitting in one place, you notice certain bass notes are almost inaudible while others practically rattle your teeth out. This problem is particularly difficult in very "live" (reverberant) rooms and rooms which have big parallel walls that are on the order of the bass wavelengths in distance from each other.

    Now, the near opposite of playing in a "live" room is playing outdoors in the middle of a big, grassy field. This is a near-anechoic (meaning: without echoes) environment. If you listen to bass in such surroundings, you often find the sound much smoother and more even. There is very little in the way of standing waves there, so all frequencies reach your ear without augmentation or interference from reflections.

    The challenge in a reverberant room is to get as smooth an overall bass response as possible - everywhere in the room. However, the physics of the situation is not stacked in our favor. My recommendation is to check out how the bass sounds in the parts of the room that are most likely to have listeners and adjust the best you can. It will be a compromise, any way you do it, unfortunately. The smoothest bass, room-wide, is best achieved in a really dead (anechoic) room.

    I hope this helps clarify some things.

    - Mike
     
  8. JimM

    JimM

    Jan 13, 2000
    Northern California
    Room acoustics get pretty strange,about 28 years ago,in a San Francisco museum there was a small dome shaped room with a waterbed on the floor and a light show on the ceiling.A bunch of us went inside together,I was near an outer edge.A girlfriend of mine whispered something eh,naughty in my ear and a guy sitting directly opposite from us heard it and laughed like crazy.I could hear him almost as well as I could her.there were about twenty people in the dome,we were all friends.I could barely hear the other people.Seems like the sound waves spread out as they went from one side of the dome toward the center,then came together on the other side.

    [Edited by JimM on 12-11-2000 at 11:02 PM]
     
  9. MikeyD

    MikeyD

    Sep 9, 2000
    Yes - they are really strange. My guess is that you and the other person were in/near alternate foci (focus points), and the dome acted like a parabolic reflector - which is extremely good at gathering "rays" of sound (which higher frequencies, such as whispers, can approximate) and focussing them. If you see someone pointing a parabolic dish at you in the distance, he/she may be listening to your conversation!

    - Mike
     
  10. Matthias

    Matthias

    May 30, 2000
    Vienna, Austria
    Great explanation, thanks!
    Things are much clearer for me now!!!

    Matthias
     
  11. Thomas Jefferson actually designed the rotunda of Monticello just for this reason. He was able to listen in on the private conversations of others (to great political advantage, I'm sure).
     
  12. MikeyD

    MikeyD

    Sep 9, 2000
    ...Another Way To Visualize Standing Waves...
    Standing waves in a room are similar in many ways to the standing waves in strings. When you create a "false" harmonic with your bass strings (lightly holding your finger on the string at certain places and plucking with the other hand), you are inducing a "node" at that point. If you do it at the 12th fret, you induce one node which bisects the string, so each half vibrates as if the string were half as long. When you do it at the 7th fret, the string effectively is 1/3 as long, and so on. The string flexes and makes a "bow" shape around these nodes, or dead spots. Where the string is moving with greatest displacement is called an anti-node.

    The analogy to room acoustics is this: picture the air in a room as your bass string. Picture one wall as the bridge and the opposite wall as the nut. You speakers are your plucking hand. When a frequency that corresponds to a wavelength equal to the distance between the walls emanates from the speaker, it excites a "room mode" - which is like a string resonating. If the frequency is doubled, the room mode and standing wave take on a different shape, with an additional node (or dead spot) in the middle.

    If the room is really dead or anechoic, it's like having a bridge and nut made of soft foam. There are no reflections, so the "string" does not have a resonant frequency. The only way to get it to vibrate is to drive it with continuous energy at a particular frequency. When this is done, it's possible to eliminate most of the standing waves.

    To my previous post on this subject, I should add that speaker placement can have a major effect on the location of standing waves in a reverberant room. Placing the speaker in a corner tends to excite more standing waves. I've sometimes wondered what it would be like to distribute several bass speakers around the room (at a significant distance from each other) to help minimize the standing wave problem. Of course - one might have some phase anomalies to deal with then.

    - Mike
     
  13. dwynsen

    dwynsen Guest

    Aug 31, 2000
    Ohio, USA
    Dear Bassers:

    I asked the original question. I have received wonderful information, and I thank you!

    I have a couple of comments as I thought about my question and your insightful responses:

    The problem is, indeed, due to standing waves. As someone mentioned these are produced (usually) between parallel walls when a long wave is reflected back. If the reflection is such that it is in phase with the original, then the two waves become additive. Hence BOOM! If they're nearly perfectly out-of-phase, then they cancel each other, and silence (it's how noise cancelation devices work). In my home I have two powerful subwoofers in my surround system. They're in a 30' x 26' family room with a 22' vaulted ceiling. I've had to really work to get the right placement for these boomers because of standing waves. In several areas in the room the bass is so overpowering that it will quite literally (and visibly!) shake the pictures on the wall (22Hz fundamental on a pipe organ pedal -- Bach). Even with this experience, I wondered if youse guys had some little "secret". I know now that the only reliable fix is to listen at various locations -- just like in my family room. Duh! I feel stupid.

    As for 4x10's moving less air than an 18", I think that's false, at least in part. Here's why: To roughly compare "air moving capability" one needs to look at total cone surface area in any given cabinet. Using (Pi)(R^2) as the formula to calculate the area of a circle, it's easy to figure out the actual area of the speaker cone. But it's not necessary to fuss with Pi to get a RELATIVE comparison between 4x10 and 1x18. Just use the R^2 (R-squared). A 10" has a radius of 5". Squaring it results in 5x5=25 for each speaker. Since there are 4 of them, then the relative number is 100. Doing the same with an 18" (9x9=81), one would conclude that 4x10" has more speaker cone area than a 1x18" (by nearly 25%). If the cab is properly tuned, there's no reason a 4x10 can't go lower and louder than a 1x18" (assuming the drivers are designed to do that). But that's usually not the case in real life since the 4x10's tend to be spec'd more for higher frequencies to satisfy slappers and growlers. You can't have it all from a single driver. In practical terms, the cone of a subwoofer is usually pretty stiff and heavy, and is capable of a long throw (excursion). For those reasons they aren't much good at reproducing frequencies much above 2000Hz (if that). The 10" cones are lighter and are specifically designed to reproduce higher frequencies. To do that, though, they give up some capabilities in the lower registers -- by design. That's why the 18" usually goes lower; it's designed to go lower.

    If anyone's interested there are a number of sites that go into speaker cab design. It's pretty complicated (way over my head) and deals with a number of parameters including specific characteristics of the driver(s), size of the box, size, shape and location of the ports (if any), etc. Some of the sites even offer an on-line "fill-in-the-blank" form to help folks design there own cabs. The program does the calculations for cab and port size dependent upon driver specs. Supposedly, you can build a killer cab for little more than the cost of the drivers and plywood.

    Anyway, thanks to you all for answering my stupid question. I understand it better now. I really appreciate the time you took.

    Have a Merry Xmas!

    TDBear
     
  14. dwynsen

    dwynsen Guest

    Aug 31, 2000
    Ohio, USA
    I spend time on other sites (usually guitar-related, not bass). One of the truly wonderful things about this site is that people spend their time being helpful -- not insulting. Some of the other sites are so full of name-calling morons that I avoid them now. Again, thank you.
     
  15. JimM

    JimM

    Jan 13, 2000
    Northern California
    Okay,I'll say it...

    Dwynsen,

    We bassists are used to being in the supportive role.
    (well,someone should brag about our humility!) ;)
     
  16. Dave S...

    Dave S...

    Oct 13, 2000
    Mikey D and all,

    Thanks so much for the great clarification on this topic! Reading it makes a whole bunch of sense. I agree that this site is a great place to find some truly helpful advice! Plus, it's nice to hear that I was SORT OF in the right hemisphere with my 'thoughts.' I also enjoy the opportunity to learn...(and I've got lots to learn about LOTS of things!)

    Back to the board!

    Best Wishes

     
  17. MikeyD

    MikeyD

    Sep 9, 2000
    Thanks for your reply, Dave! The day someone says he/she *doesn't* have lots to learn is the day that person becomes close-minded, and the day before he/she becomes stupid! I've studied lots of things in my life, but I still feel like it hardly scratches the surface - even in the areas in which I could be considered an "expert". I hang out with university professors quite often, and those I respect the most - and those who are actually the most knowledgeable - are the ones who feel like they hardly know anything! Anyway, I'm glad you're getting something out of this, as I am. Best wishes to you, too!
    - Mike
     
  18. MikeyD

    MikeyD

    Sep 9, 2000
    Nice comment. I have to agree. I've been reading Usenet newsgroups now for several months, and I have to say without hesitation, that the "bass" newsgroups are by far the most civilized and respectful I've seen. I think other forums have lots of angry, frustrated people who are looking for someone to disrespect. It's nice that we bass players seem to have some deep-rooted respect for each other.
    - Mike
     
  19. MikeyD

    MikeyD

    Sep 9, 2000
    Hi - yes, your experience with standing waves in your home stereo is an excellent example of this problem. I've had to deal with a similar situation in my house, too. No real secret - one just needs to understand about reflections and standing waves and how to minimize them as much as possible. There are sound absorbers one can buy to place in corners to help mitigate the problem, as well as other solutions. However, the live bass-playing problem can be tougher, because we often don't have control over the acoustic environment in which we're asked to play.

    I basically agree with your comment about 4x10 vs. 1x18 cabinets. One must also factor radiated power from ports/vents, if any. Your comment about 10s being designed for higher range is right on. The moving mass of the driver is lower to enable this, whereas the 18" is almost never conceived as an upper-range speaker, so its moving mass can be higher. Another point you touch on is the cone excursion. I'm thinking at this point that a true subwoofer which handles only the lowest frequencies can get away with huge excursions, whereas a speaker intended to handle higher stuff should not be allowed to move as much. Such gross excursions can cause distortion (e.g., Doppler shift or IM, I think) of the higher frequencies. So... while the 4x10 is likely to have the larger total cone area, perhaps the typical 1x18 can still move more air when one looks at the overall "swept volume" (area times excursion). Anyone have some thoughts on this?

    Yes - if you have some URL's for these sites, I'd appreciate your posting them!

    You're welcome. This has been a fun thread, and your question was not stupid. In fact, this issue is probably one of the tougher ones we bassists have to deal with. Merry Christmas to you, too!
    - Mike
     
  20.