Fact or fiction speaker size question

[Undertoad]

I think I understand why a bunch of smaller speakers can produce the same or better bass as a massive speaker. An audio friend of mine says that although you can get as much bass from a smaller speaker, a 15" is better for really large rooms or outdoors.

 

I asked him why and he muttered something about how sound waves are produced and that 15" speakers took a larger space to get a wave going because of how they moved the air, or something like that. I say he "muttered", to cover the fact that he said a bunch of tech-sounding audio things that I didn't really understand.

 

So, fact or fiction, larger speakers are somehow better for larger spaces?

[burdizzos]

I think it's bunk, but I lack the funds and motivation to prove it.

 

 

SPL is SPL.

[Texas Noise Factory]

I've never been able to test it really, and I'm sure there will be a more scientific response to this eventually, but think of it like this. I used to be into car audio, and I liked having a booming system in my car. I tried 12's, 10's, 8's... I found that if I used two 8" speakers in my car, I would get sufficient bass. However it wasn't going low enough for me. You could not hear it outside the car with it cranked. So I replaced it with a 12" speaker. Same amp. I then got lower response, just as sufficient bass, but I noticed that I could get a few car lengths away from my car and still hear it clearly. It's because like your friend said, It takes a larger speaker longer respond to a lower note, and since it is (usually) less efficient than a smaller one, it takes it more time to stop responding. also, a larger speaker is more capable of producing lower sounds than a smaller one (for the most part) and because of the larger surface area of the speaker, it takes a longer distance (in distance ft.) for it to be heard. I know that this isn't a perfectly correct explanation, but that's the gist of it.. Read up on how pipe organs produce the sounds that they make. The same rules apply...

 

to address your question of outdoor gigs, remember that the large venues have larger speakers, and much more amplification than smaller ones. You will still be heard if your stuff is mic'd correctly and run through the PA.

[Xanadu-PyRo]

Size definately matters;)

[Zeromus-X]

Would this have anything to do with the fundamental developing properly? i.e., whereas a 10" speaker hitting the fundamental E might... no, wait, that makes no sense.

 

I can't think of any logical reason to say that a bigger speaker will work better outdoors, except that typically bigger speakers are rated for more power, which equates to more noise in most cases.

[Apendecto]

Tell that to my SWR 8x8.

 

Yo.

[L. Ron Hoover]

Bunk.

 

It's just easier to get low bass with larger drivers. You'd need a lot of 10s and a big cab to produce the same SPL at 40Hz as a double-18 subwoofer. An 18 is going to be a lot more efficient at that frequency than a 10 is.

 

The notion that low freqencies somehow take space to develop properly is {censored}ing nonsense. People who believe this are getting boundary loading and standing waves confused with propagation. In a typical room you're going to get more bass at the back wall because of boundary effects. Lots of rooms build standing waves at some low frequencies which causes variable SPL in different locations, not to mention phase issues from multiple cabinets.

 

But, if you take any speaker cabinet outside, say into a grassy field, where boundary effects are effectively nil, the SPL will always be maximum right at the cabinet and it will decrease at a very predictable 6dB per doubling of distance irrespective of frequency.

 

Don't believe me? Try it for yourself.

[Emprov]

 

Originally posted by L. Ron Hoover Bunk. It's just easier to get low bass with larger drivers.

 

 

True dat but what about the throw? I've noticed in a lot of smaller speaker configs that what you get from 5' away is pretty much what you're going to get from 25' away. My old Aggie GS112 on the other hand was much different from a distance than it was up close -- total shotgun affect. I really haven't seen that happen with smaller speakers.

[Texas Noise Factory]

Originally posted by L. Ron Hoover Bunk. It's just easier to get low bass with larger drivers. You'd need a lot of 10s and a big cab to produce the same SPL at 40Hz as a double-18 subwoofer. An 18 is going to be a lot more efficient at that frequency than a 10 is. The notion that low freqencies somehow take space to develop properly is {censored}ing nonsense. People who believe this are getting boundary loading and standing waves confused with propagation. In a typical room you're going to get more bass at the back wall because of boundary effects. Lots of rooms build standing waves at some low frequencies which causes variable SPL in different locations, not to mention phase issues from multiple cabinets. But, if you take any speaker cabinet outside, say into a grassy field, where boundary effects are effectively nil, the SPL will always be maximum right at the cabinet and it will decrease at a very predictable 6dB per doubling of distance irrespective of frequency . Don't believe me? Try it for yourself.

 

yup. I agree with what you say for the most part looks like I need to do more reading..

 

I guess comparing it to a pipe organ in that sense is wrong because the pipe organ's pipes are the length they are in order to tune the instrument. Dur.

[Zeromus-X]

Originally posted by L. Ron Hoover But, if you take any speaker cabinet outside, say into a grassy field, where boundary effects are effectively nil, the SPL will always be maximum right at the cabinet and it will decrease at a very predictable 6dB per doubling of distance irrespective of frequency . Don't believe me? Try it for yourself.

 

While I agree with that, from my experiments (on paper at least), up next to the cabinet you shouldn't be hearing the fundamental if it hasn't developed. Since all frequencies are going to be travelling the same speed, the fundamental shouldn't be developing until it hits a certain distance. That is, in a completely anechoic chamber, playing, say, a 256 Hz fundamental note with a wave speed of 405 m/s shouldn't be heard until you're ~1.5m away. If you're hearing it, it should mean you're hearing it reflected off another surface. Since by definition an anechoic chamber doesn't have anything to reflect off of, you should only be able to hear the subsequent harmonic intervals of whatever note you're playing at whatever position you're at.

 

I'd test this but I'm one anechoic chamber short. I assume you could test it in an open field, but your brain is going to be busy trying to "fill in" the missing parts. I bet if you were to take a frequency analyzer and stick the mic right in front of the cabinet, though, you'd notice a huge boost at 256 Hz once you moved the mic ~1.5m away as opposed to having it closer.

 

This is all theoretical, feel free to shoot it down.

[L. Ron Hoover]

 

Originally posted by Emprov True dat but what about the throw? I've noticed in a lot of smaller speaker configs that what you get from 5' away is pretty much what you're going to get from 25' away. My old Aggie GS112 on the other hand was much different from a distance than it was up close -- total shotgun affect. I really haven't seen that happen with smaller speakers.

 

 

There are a lot of factors at play. In order to get any kind of meaningful result you'd need two cabs that had exactly the same frequency response, for starters. Then you have to consider that arrays of speakers tend to have narrower coverage patterns than single drivers, which can affect how they interact with the space, boundary loading and standing waves, etc.

 

Again, you won't see any cabinets displaying actual increasing SPL with distance in an anechoic or close to free-air environment.

[Emprov]

 

Originally posted by L. Ron Hoover Again, you won't see any cabinets displaying actual increasing SPL with distance in an anechoic or close to free-air environment.

 

 

It's not an increase in SPL, it's more like a maturation of certain freq's.

[L. Ron Hoover]

Originally posted by Zeromus-X While I agree with that, from my experiments (on paper at least), up next to the cabinet you shouldn't be hearing the fundamental if it hasn't developed. Since all frequencies are going to be travelling the same speed, the fundamental shouldn't be developing until it hits a certain distance. That is, in a completely anechoic chamber, playing, say, a 256 Hz fundamental note with a wave speed of 405 m/s shouldn't be heard until you're ~1.5m away. If you're hearing it, it should mean you're hearing it reflected off another surface. Since by definition an anechoic chamber doesn't have anything to reflect off of, you should only be able to hear the subsequent harmonic intervals of whatever note you're playing at whatever position you're at. I'd test this but I'm one anechoic chamber short. I assume you could test it in an open field, but your brain is going to be busy trying to "fill in" the missing parts. I bet if you were to take a frequency analyzer and stick the mic right in front of the cabinet, though, you'd notice a huge boost at 256 Hz once you moved the mic ~1.5m away as opposed to having it closer. This is all theoretical, feel free to shoot it down.

 

Well, your original premise is wrong here....

 

Waves don't propagate like that. Think about ocean waves. While they oscillate, they also travel, they don't just oscillate in place. So any point the wave passes will see both the crest and the trough during each cycle. Sound waves behave essentially the same way except that they are longitudinal as opposed to transverse. The air is compressed and rarefacted by the driver and the pressure waves radiate outward at approx 340m/s.

 

So If you're standing 1 meter from the cab and I'm 20 meters back (assuming anechoic), every compression (maximum level) that passes you passes me 60mS later, except that it's been attenuated some. This is not frequency dependent.

 

What you're saying is true for a standing wave, though because it has nodes and peaks, like a bass string. In an environment where there is no boundary loading, there won't be any standing waves.

[Apendecto]

Seems to me if there is no concrete answer and people are throwing physics around, then it doesn't matter. I've heard very deep 8's {censored}ty low end comming from an 18.

 

Yo.

[L. Ron Hoover]

Originally posted by Emprov It's not an increase in SPL, it's more like a maturation of certain freq's.

 

It doesn't work that way.

 

 

Again, there are so many things at play that it's hard to get a handle on what exactly is going on. I will say that different cab topologies will interact with spaces differently, but until you can do a controlled experiment you can't really say anything conclusive about it.

[L. Ron Hoover]

 

Originally posted by Apendecto Seems to me if there is no concrete answer and people are throwing physics around, then it doesn't matter. I've heard very deep 8's {censored}ty low end comming from an 18. Yo.

 

 

No-one's saying that you can't get good bottom end out of small speakers. It's just easier with bigger ones. I've heard frightening bottom end from very small drivers in smartly designed boxes.

[L. Ron Hoover]

Originally posted by L. Ron Hoover It doesn't work that way. Again, there are so many things at play that it's hard to get a handle on what exactly is going on. I will say that different cab topologies will interact with spaces differently, but until you can do a controlled experiment you can't really say anything conclusive about it.

 

 

...And yes, it is possible that a cab could interact with a room in a way that SPL will increase with distance but it's from boundary loading/standing waves and not from primary propagation. Of course, for this to be the case there must also be places in the room where there is more attenuation than normal for that distance. For every spot where the waves reinforce each other, there's another where they cancel.... Standing waves are bad.

[Emprov]

Originally posted by L. Ron Hoover It doesn't work that way.

 

Ever designed a speaker system for hall or church? It's pretty cool to play around with long and short throw technologies and speakers. I've never really researched the in's and out's of it but it's a very real thing. And it's also very real with single speaker units. I've owned a ton of cabs and have noticed it on more than one.

[Apendecto]

 

Originally posted by L. Ron Hoover No-one's saying that you can't get good bottom end out of small speakers. It's just easier with bigger ones. I've heard frightening bottom end from very small drivers in smartly designed boxes.

 

 

Gotcha.

 

Yo.

[L. Ron Hoover]

Originally posted by Emprov Ever designed a speaker system for hall or church? It's pretty cool to play around with long and short throw technologies and speakers. I've never really researched the in's and out's of it but it's a very real thing. And it's also very real with single speaker units. I've owned a ton of cabs and have noticed it on more than one.

 

You need to read what I've posted a bit more carefully.. I'm not saying that there isn't an effect, just that it isn't primary propagation. Especially for low frequencies, because you can't control directivity.

 

 

I've designed systems for any kind of event and venue imaginable, from tiny clubs to events with 100000 people at them.

 

Long and short throw as you are referring to here are applied to mid/high cabinets where you can actually control directivity. Cabinets with tighter directivity patterns 'throw' longer than wider ones because a narrower pattern == more on-axis SPL.

But long throw boxes also obey they laws of physics. They will invariably have the most SPL right at the box and it will drop off at distance accordingly. Ever used long throw boxes in a small venue? They'll tear your head off.

 

You can get a properly designed line array to drop in level at -3dB per doubling of distance (in the nearfield) as opposed to -6dB per doubling because the propagation pattern from a line array is roughly cylindrical rather than spherical, but you can't get it to increase in SPL with distance unless the acoustics of the space are helping you.

 

It's really difficult to control directivity at low frequencies. You need very large arrays (ie on the scale of the lowest wavelengths) to get directivty down low.

[boseengineer]

 

Originally posted by Zeromus-X While I agree with that, from my experiments (on paper at least), up next to the cabinet you shouldn't be hearing the fundamental if it hasn't developed. Since all frequencies are going to be travelling the same speed, the fundamental shouldn't be developing until it hits a certain distance. That is, in a completely anechoic chamber, playing, say, a 256 Hz fundamental note with a wave speed of 405 m/s shouldn't be heard until you're ~1.5m away. If you're hearing it, it should mean you're hearing it reflected off another surface. Since by definition an anechoic chamber doesn't have anything to reflect off of, you should only be able to hear the subsequent harmonic intervals of whatever note you're playing at whatever position you're at. I'd test this but I'm one anechoic chamber short. I assume you could test it in an open field, but your brain is going to be busy trying to "fill in" the missing parts. I bet if you were to take a frequency analyzer and stick the mic right in front of the cabinet, though, you'd notice a huge boost at 256 Hz once you moved the mic ~1.5m away as opposed to having it closer. This is all theoretical, feel free to shoot it down.

 

 

I actually happen to have an anechoic at my disposal. Unfortunatley you are way off the mark here. The 256 Hz will be loudest right a the speaker, remain fairly constant for a foot or so and than start falling off with a slope of 6dB per distance doubling.

 

Speaker size has very little to do with how a speaker radiates. Sound is after all moving air and bigger speakers move more of that than smaller ones (all other things being equal). The techical term for "moving air" is "volume velocity".

 

In this regard, two 10"s are about the same as one 15" and two 12"s are about the about the same as one 18". On the other hand bigger cones are harder to control and develop undesired motion easier than smaller ones. The bigger ones are also heavier and take a little longer to get into gear.

 

How deep a speaker goes is determined by the resonance frequency of the drivers, the sharpness of the resonance, and the size and design type of the box. It's much more a matter of proper tuning than of size.

 

The most noticable difference between smaller and bigger drivers is the high end (if not just used as a subwoofer) and directivity. The geometric arrangement of the drivers determines the directivity and smaller drivers offer more flexibility. I used to stack my two 2x10s sideway to prevent them from getting horizintally to narrow and also from beaming too much towards the ceiling.

[Zeromus-X]

Thanks for clearing that up, guys. Like I said, I've never actually applied any of the stuff I've written down, it's all just conceptual ramblings from audio-related physics classes that I took a few years ago.

[Emprov]

 

Originally posted by L. Ron Hoover Long and short throw as you are referring to here are applied to mid/high cabinets where you can actually control directivity. Cabinets with tighter directivity patterns 'throw' longer than wider ones because a narrower pattern == more on-axis SPL.

 

 

Ya, I'm messing around right now with some HT speakers that I designed. They're absolutely amazing if your ears are at the right height (at tweeter level or slightly below) and you're pretty much right in front of them. Off axis performance is not the greatest though. To make matters worse, I shave my head so I can't even pull my hair out over this one!

 

I totally get what you're saying and I understand the *basics* of throw, you can probably school me on the rest. But, I have had several cabs that exhibit much different tonal charictaristics at 5' than they do at 25'. 'splain that one to me!

[L. Ron Hoover]

 

Originally posted by Emprov Ya, I'm messing around right now with some HT speakers that I designed. They're absolutely amazing if your ears are at the right height (at tweeter level or slightly below) and you're pretty much right in front of them. Off axis performance is not the greatest though. To make matters worse, I shave my head so I can't even pull my hair out over this one! I totally get what you're saying and I understand the *basics* of throw, you can probably school me on the rest. But, I have had several cabs that exhibit much different tonal charictaristics at 5' than they do at 25'. 'splain that one to me!

 

 

Well, I can't go into specifics (obviously:D) but there are lots of possibilities. How the cab interacts with the floor or other boundaries is one factor, especially for low end.

 

In cabs with multiple drivers reproducing the same frequencies there's mutual coupling at low frequencies and the the dreaded comb filtering at higher ones. Constructive interference in one location, destructive in another, etc.

 

I'm sure that there are perfectly logical, measureable reasons......

 

 

It's all fun. We're just starting prodcution of an active speaker system and we've been experimenting with different crossover filters and whatnot. It amazes me that changing a resistor value by 2% can make such a sonic difference. Getting off-axis response to be good takes time and a large amount of trial and error, I'm finding.

 

I come from a backgtound of designing arrays from speakers with known parameters so this has all been a learning experience for me.

[Emprov]

 

Originally posted by L. Ron Hoover It's all fun. We're just starting prodcution of an active speaker system and we've been experimenting with different crossover filters and whatnot. It amazes me that changing a resistor value by 2% can make such a sonic difference. Getting off-axis response to be good takes time and a large amount of trial and error, I'm finding. I come from a backgtound of designing arrays from speakers with known parameters so this has all been a learning experience for me.

 

 

Totally cool! I'm just a home junkie and really digging into passive crossovers right now, I'm just starting to get familiar with this stuff. And ya, I'm amazed at how small changes in values in some places can display such hugely different results and huge changes in other areas result in very small perceived changes. Suffice to say that I'm still in the confusion stage. The on/off axis performance thing is a total mystery to me though. On the speakers that I'm currently designing I'm going to try two different cabs: one with surface mounted tweeter and one that has a recessed tweeter. Hopefully I'll notice some sort of a difference with that? *shrugs shoulders*