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Give Me The Science To Back It Up!!!

Discussion in 'Amps and Cabs [BG]' started by Modern Growl, Aug 25, 2005.


  1. So we have had debates on 10" speakers vs. 15" speakers here back a little bit. But out of all the threads I've read, everyone went on opinion mostly. Any science to back it up?

    10"s are punchier... scientifically why?
    15" are USUALLY deeper in freq... scientifically why?


    I have a feeling people are going to bring in 12's and 18's but lets try to stick to the most popular speakers in debate at TB, 10"s and 15"s.

    And why not.. due to my obsession w/ growl, for me.. which do you think is 'growlier' ? (Just a little side project)
     
  2. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    There seems to be no physical necessity for 10's and 15's to sound different. True, the 15" cone has more mass, but you can supply more force to push the mass.

    Instead, I think the difference is the result of what is possible with a bigger driver. You can extend the low frequency response without a huge sacrifice in efficiency. Thus, if you are a speaker company and want to offer the option of more boom or more punch, then it makes sense to design punchy 10's and boomy 15's. This is also what the market has come to expect.

    In other words, even if a punchy 15" cabinet is possible in theory, you might not be able to buy one. For the DIY'er, it is complicated by the choice of available drivers, but I have had success with a carefully chosen 15" in a very small box. It is quite efficient, yet quite responsive and punchy.
     
  3. Aenema

    Aenema

    Apr 18, 2001
    Michigan
    my answer isnt exactly science... but why do bass drums have a deeper sound then toms? and why do bigger toms sound deeper then smaller ones? even with the same force applied you will still hear a deeper sound on the bigger drums. i believe the same basic concept applies to bass drivers. sure you can tune a box to make a 15 punchier then most 15's but i still believe it will never be as punchy as a 10 simply because of its size. id like to hear a speaker ologist speak though.
     
  4. basseuphoria

    basseuphoria

    May 19, 2005
    even w/ a very large magnet (which is kinda like extra horsepower) a 15" will still not be as fast as a well built 10". lets put it this way; it is easier to start and stop a 10" cone than it is to do the same w/ a 15" cone. e.i. 15" IMHO have always been a little blurry compared to 10" :)
     
  5. Bruce Lindfield

    Bruce Lindfield Unprofessional TalkBass Contributor Gold Supporting Member

    Tone is subjective!

    One person might say a particular setup sounds warm and bassy - whereas I might say that same sound is muddy and unfocused...:meh:
     
  6. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    If you want a scientific explanation 10's vs 15's as regards 'punchy' and 'growl' you will need to define those terms. I never use them because I think they are very vague.

    I think by punchy you mean 'fast transient response'. I have no idea what 'growl' means.
     
  7. Aenema

    Aenema

    Apr 18, 2001
    Michigan
    sorry to hi jack this thread but what does a heavier magnet do for the sound of a speaker? ive always wondered.
     
  8. Inertia. 10's will more faithfully follow the twists, turns, and wiggles required by the musical waveform than the heavier 15's would.

    10's are the running backs of speaker cones, vs 15's being the offensive linemen of speaker cones.

    That explains the punch, they can more faithfully reproduce the midrange, where the 15's can no longer respond fast enough.

    As for the deeper freq, reproducing a large wavelength requires a large piston, moving lots of air. Piston size vs cone excursion. Want to move a big pile of dirt? Bigger shovel lets you do it with less motion. However, lots of little shovels can move as much dirt as one large one. Hence some 4x10's can put out more bottom than a 1x15, but still retain the punch because the individual cones can respond quicker.

    That's it in a nutshell.

    Cab design/tuning has a lot to do with it too, so you can get 2x10's like the EA's putting out more bottom end in a low B than my old bag end 18".

    Randy
     
  9. True, if you boost the midrange and highs enough you can extend the range of a 15, sure. But then again, the question wasn't how to make up for the differences between 10's and 15's. It was what are the differences between 10's and 15's.

    The force (watts) required is proportional to the mass x acceleration. Higher freqs require more acceleration. Thus its not just adding more watts (say 300w amp driving a 15 vs 200 watt amp driving a 10) to make up for the extra mass, the extra power needed keeps growing as the frequency increases. The higher in freq you go, the more power you need to add to compensate.

    You could theoretically reproduce ultrasonics with a 15 if you nail it with enough power and the VC doesn't melt down.

    Randy
     
  10. The way it has been explained to me is it's all a matter of moving the air. Correct me if I'm wrong;

    A 15" speaker has farther to go to move than a 10", and thus takes more push to get the sound out. It also can't vibrate as fast, and as quickly, as a 10" by shear physics of size, so it doesn't give out the "highs" as easily as a 10". In reverse, the 10" doesn't move as much air when vibrating slower for the low frequencys and will not have the resonance that a 15" has. This is why you have cabs with 2x or 4x10's, so that put together, the 4 10" speakers will all move more air, but still have the individual "highs" at the same time, which might explain the "punch". I'm sure that there's a heckofalot more to it than that, but that's a layman's version, IMHO.
     
  11. I had a superb amp tech describe it to me in terms of "slew rate". But, as best as I can tell "slew rate" refers to the rate at which an electrical device can discharge and recharge. So that would refer to the electrical components of an amp and not the mechanical ones like a speaker cone. I'm not sure about that; my wife is the engineer, not me. But the basic principle is similar to Steve's description of inertia and my amp tech friend may have gotten the terms confused.

    I have two suggestions for a scientific explanation. First, ask the question on the webervst bulletin board. Ted Weber often responds and he could tell you, if anybody could. Second, use a search engine for audio engineering. You will find lots of university professor websites discussing these issues.
     
  12. +1. Or go to the source. (...one of them, at least; take your pick.) Try going to the Schroeder cabinet site and emailing Jorg Schroeder who says, (and I quote:), "Have a look around and feel free to email me with any questions."

    http://www.schroedercabinets.com/

    IF you do, post his reply; ya' never know what you might come up with if you just ask the question... ;)
     
  13. I think the "acoustic coupling" people refer to is similar to an array antenna. A bunch of smaller antennas hooked together can simulate a much larger antenna. NASA does stuff like that I "think" for the deep space network. You've all seen the pictures of a whole field of smaller antennas in the desert all pointing the same way? Same, or similar principle.

    That's partly how the multiple smaller drivers can simulate a larger single driver.

    Randy
     
  14. Higher frequencies (shorter wavelenghts) disperse better with smaller cones. This has a big effect on how the rig sounds depending on where you are in relation to the cone. A 15 will reproduce some pretty high frequencies but you need to be right on axis to hear it. So for perception's sake, getting some smaller drivers involved will help everyone hear the harmonic content of your tone.
     
  15. great stuff guys, thanks for the input!
     
  16. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    First... acoustic power is "volume velocity"... how much air you move how far.

    At any frequency, the "speed of movement" (the velocity) is fixed in one sense, since a cycle is "x" seconds long, and you know the speaker takes that long to complete a cycle. (we are NOT talking about the speed of sound......) So the actual speed of cone motion is related to the distance of movement.

    OK, so at 40 Hz, you are moving fairly slowly.... maybe a given speaker has to move 1 CM (10mm)....for round numbers.

    now go to 400Hz... the speaker now is moving 10 times faster, 10 times the number of cycles per second... Now the speaker can move 1/10 the distance, (1mm not 10) OR it can have 1/10 the cone area and still move 10mm, or some balance between, and produce the same power.

    At 4kHz, same deal, now 100 times the frequency. The speaker could be BOTH 1/10 the area AND move 1/10 the distance (1/10 of 1/10 is 1/100) or any balance that calculates right. So if you started with a 15" moving 1cm, you could use a 5" moving 1mm for equal power at 4kHz.

    Same thing works at lower frequencies. You need more movement OR more cone area, or some of each, to produce equal power.

    So a 15 starts out with an advantage at low frequencies, since the larger cone needs to move less far for a given power.

    Because speaker cones can only move a certain amount as a practical matter, at lows you can get more power from a 15 than a 10, if both have the same limits of movement. Actually, though, the 15 often can be made to move farther than a 10" as well.....

    Now, the 15 is a bigger cone than a 10. In order to make it all move together as one piece, and not flex, etc, it needs to be stiffer, which generally means heavier. That's on top of just having more material due to more area. So it may be considerably heavier than a 10. It will take more force to make it follow the same waveform as a lighter 10"

    Force on the voice coil is proportional to "B" x "L" x "i", where "B" is the strength of the magnetic field, "L" is the length of wire in the field, and "i" is the current flowing.

    A bigger magnet tends to increase "B", but there is only so much you can get thru a smaller coil diameter and gap. You need to increase "L" also.

    But a bigger coil with bigger "L" increases the area of the gap, and reduces "B". Now you need a bigger magnet again. The bigger coil is heavier, so you get a hit at highs, needing even MORE "B".

    If you increase "i", that means a bigger amp. But a small coil will burn up if "i" is too big.... so you have to make the coil bigger, as above....... Then it gets heavier, and loses highs.

    Then again, low frequency tuning means a low resonance frequency and softer suspension, which normally means a heavier cone..... and worse highs..... and lower efficiency.

    But the 15 will fit a bigger magnet and coil, so may be able to offset part of the efficiency issues, IF the performance you need allows you to adjust the BL product.

    Since a 15 is normally heavier, it is a little easier to get low resonance with it than a 10, as you needn't add much cone weight. added weight doesn't help efficiency, and a 10 vs a 15 at same resonance etc will probably be less effcient... advantage to the 15 yet again for lows.

    Tying it all up.....

    A 10" is lighter, so it follows a complex waveform (including harmonics) better, but has limits on the distance the cone can move, and thus the power it can handle, because of smaller area. There are limits to the size of magnet and coil that fit on a 10, also. So there are limits to the amount of low frequency power a 10" can produce. It tends to be best at upper bass and low mids, which means "punch".

    The 15 is heavier, so it is not as good at highs. But it has room for the bigger magnet and coil to make up somewhat for efficiency hits, so it can do well at lows and retain some highs. It is also capable of more power output at low frequencies on an area basis, with less cone movement and so fewer compromises. But overall, a 15 tends to be better at lows and not as good at highs, making it better at "boom", and not as good at "punch"

    Because a 10" is smaller and lighter, it is better at higher frequencies also, meaning it will be somewhat brighter.

    There are ways to adjust that, by letting the cone flex so that the area (and weight) moved decreases as frequency goes up, or putting on a whizzer, etc.

    But ultimately, it is hard to make a 15 that does lows AND highs that match a 10". It can be almost done, but it tends to be rather expensive, and you never quite get there.

    I have used 15" speakers that worked well covering the range from about 50 Hz to 5kHz with reasonably flat response. They are good bass speakers, and are in some older Ampeg products. They weren't cheap.............. and even then compromises meant they didn't go super-low.

    Not only that, but the power response isn't totally even, since the speakers were more directive at higher frequencies, the sound pressure in front was "flat" over frequency but the power response was not flat. if it had been, the SPL response would have had an up-tilt due to directivity.
     
  17. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Wavelength, wavelength, wavelength. Different size speakers sound different because their ability to produce sound is dependant on the ratio of the wavelength being produced to the size of the cone.
    Absolutely not true. A cone moves back and forth at the exact frequency (speed) of the tone it is reproducing. If not you might play a B note and have an A come out of the speaker. If you alter the speed of the cone you change the frequency and thus change the note. The two are inseparable.
    No. The 15 doesn't work as well because the cone is too large compared to the wavelength of the frequency being produced.
    In the simplest terms it allows the speaker to work more efficiently over all but with a loss of bass response.
    True, but it would have the dispersion of a laser beam. Cone drivers lose dispersion rapidly once the diameter of the cone exceeds a wavelength. For the average 15 that occurs around 1kHz.

    Yes, but to perfectly do so with cone drivers their acoustic centers must be no more than a wavelength apart. Very easy to do in the bass frequencies, not so in the mids or higher.

    Absolutely true. Very few drivers operate effectively over more than a four octave range. The range of the electric bass is on the order of eight octaves. Do the math. No single driver is capable of properly covering the entire range of the electric bass.
     
  18. Brad Barker

    Brad Barker Supporting Member

    Apr 13, 2001
    berkeley, ca
    umm...

    solve the wave equation in cylindrical coordinates with the appropriate boundary conditions.

    :confused:

    :ninja:

    (hey, you asked for the science! :spit: )
     
  19. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Sort-of......

    Actually, the speed IS important.... because the speed affects the movement distance.

    If you move at 40 Hz over 1 cm, that is a different speed than if you move at 40 Hz over 1 mm, and it affects the power output.

    if the combination of conditions causes the system to not have the force available to move the cone as far at a given frequency, its power response is less than a speaker which CAN produce the required volume velocity. Audible output will be lower.

    Try shaking a cardboard box, then try shaking your car. Which one takes more force? Which one can you shake 5" back and forth faster? THAT is a high frequency response difference!
     
  20. Yeah, I'll was going to post that, have to agree with Jerrold, but it gets complicated. Freq matters, as well as distance to determine speed.

    You may drive the same speed making round trips from Detroit to Chicago every 10 hours as you would making 50 round trips in 10 hours to a closer destination.

    Higher freqs= more round trips, but less distance travelled, low freqs = less trips requiring more excursion to reproduce the longer waveform.

    So they "tend" to partially cancel each other out, at least.

    If this "I was gonna post that" thing works out, I'm going to expand, keep using it even when someone smart says something I wouldn't have thought of in a million years!

    Randy