Aside from a loss of hearing...

SDA1C

If you have two stereos (in the same room) one playing @ 100 decibels and the other @ 115 decibels what would be the combined level? There's no way its the sum of the two. But how does one calculate that sort of thing. I know it will depend on many factors in the room but as a rule of thumb???

VR3

I would think it would still be 115 as it is your loudest point

SDA1C

is that to say you can raise the spl with out raising the decibel level?

VR3

I dont think you will be able to hear the softer unit unless the louder unit is in a soft passage or is turned down...

Same thing as a flame - it will only be hot as the hottest source..

Now granted I could be totally wrong - but I dont see how 100 db could increase 115 because in order to get a change in volume you have to add 3db... you are about what 4-5 times softer than the loudest source

Tony M

115 dbs.

I've done similar with my 4 Kenwood Kd888's and 2 DJ speakers with 2-15"ers in each, all playing and turning the volume up a notch or so consecutively and it got to a point where there was no point in going any louder. It seemed to have a threshold of volume whether I turned any one set up any more or not. That output was 8-15" high impedence woofers in a 18x21 x16' ceiling room with 10' walls. It was a WOW moment for sure.

It was a once in a lifetime thing I just had to try. My hearing is still ok. It was hard to breath though. REALLY.

VR3

The most uncomfortable I have ever felt because of speakers was when we fired of my massive subwoofer I was building and it hit down into the 8-10hz range... the shear output and pressurization of the room at that moment was just so intense and uncomfortable I felt a little sick

SDA1C

It was definitely too loud with just the qsc12 lol. Just thought I'd ask cause it seems combining the qsc 12 on the 2 extra channels of my tg111 would be oh my god. I haven't put it all together yet but when I get a remote that will work from a hundred yards away I'll definitely be tempted to try.

schwarcw

You guys are crazy! But you already know that:cheesygrin:

Rock on!

quadzilla

Vr3MxStyler2k3 wrote: »

The most uncomfortable I have ever felt because of speakers was when we fired of my massive subwoofer I was building and it hit down into the 8-10hz range... the shear output and pressurization of the room at that moment was just so intense and uncomfortable I felt a little sick

Brown sound

Dennis Gardner

If I understand the theories........If both were identical signals, run from the same plane and separately capable of signals @ 115 dB, you should register 121 dB. This is based on the theory that you have doubled the power and doubled the surface area. Each doubling nets 3dB increase. This would be in a perfect open air setting. In a room, anything is possible due to reflections/cancelling.

I don't know how to figure the lower signal level into the equation, but I tend to think that the separately powered 5 dB lesser signal would add very little to the louder signal. Someone with a higher understanding of acoustics/electronics than myself, is welcome to add or correct me if I'm wrong.

decal

So what's the reason for doing this anyway? Just curious.

rromeo923

Vr3MxStyler2k3 wrote: »

The most uncomfortable I have ever felt because of speakers was when we fired of my massive subwoofer I was building and it hit down into the 8-10hz range... the shear output and pressurization of the room at that moment was just so intense and uncomfortable I felt a little sick

I was at a Jerry Garcia Band concert in a small auditorium and was dancing right next to a speaker. The band hit some major low note during his rendition of "Lucky Ole Sun" and I couldnt hear anything for about 30 seconds. I was pretty scared for a bit.

SDA1C

YUP! That stuff will make you mess your pants lol. Maybe that's why they call it "Brown" hehe

SDA1C

Dennis Gardner wrote: »

If I understand the theories........If both were identical signals, run from the same plane and separately capable of signals @ 115 dB, you should register 121 dB. This is based on the theory that you have doubled the power and doubled the surface area. Each doubling nets 3dB increase. This would be in a perfect open air setting. In a room, anything is possible due to reflections/cancelling.

I don't know how to figure the lower signal level into the equation, but I tend to think that the separately powered 5 dB lesser signal would add very little to the louder signal. Someone with a higher understanding of acoustics/electronics than myself, is welcome to add or correct me if I'm wrong.

That's the line of thinking I was leaning towards. It seems logical that even though the 2nd source isn't as loud it is adding to the pressure and thus adding to the ease in which the 1st can run. By proximity it should add to the db as long as its not reversed phase. The calc's on the lower register are certainly notable with a separate system but the measurements are foggy to me as well. I do have 2 free channels on my pre so I might just try it. Earplugs and muffs applied of course.

SDA1C

decal wrote: »

So what's the reason for doing this anyway? Just curious.

Simple curiosity. Nothing more....ok Maybe I want to throw a block party with out exposing my gear to the snow:twisted:

unc2701

I'm sure there's a formula for it, but my guess is ~115.

So, two sources playing at the same level add 3db; 115 and 115 combined would be 118. So, 114.9 and 115 is not just going to be 115; it's not a cliff. However, the difference between 115 and 100 is sufficient on a log scale that the 100 isn't going to add much, so it'd be like 115.01. Whisper on a scream, so to speak.

If I get a minute, I'll figure out the math.

SDA1C

unc2701 wrote: »

I'm sure there's a formula for it, but my guess is ~115.

So, two sources playing at the same level add 3db; 115 and 115 combined would be 118. So, 114.9 and 115 is not just going to be 115; it's not a cliff. However, the difference between 115 and 100 is sufficient on a log scale that the 100 isn't going to add much, so it'd be like 115.01. Whisper on a scream, so to speak.

If I get a minute, I'll figure out the math.

AWESOME! Please do me the favor of figuring it with 99.7 and 115.4. Also, If you might post the formula so I can jot it down would be great!

Thanks, 1C

After we (you lol) do all the math I'll hook it up and see if its real world

nwohlford

You need to convert back to sound intensities to add, so divide by 10 and the raise 10 to each power. Then add the two. Now convert back to decibels by taking base 10 log an then multiplying by 10.

= 10 * log (10 ^ 11.5 + 10 ^10) = 115 db

adding a sound of 5 db less will increase the total by about 1 db (110 db + 115 db = 116 db).

SDA1C

OK so roughly 115.45? Sounds to me like the biggest difference will be heard in the supplemental frequencies. Meaning the powered cabs wont handle the low sub that the HT can provide so it might sound stronger but in reality it's not any louder on the register.

Pretty much what your saying is point the things out the window and turn it down ? lol

unc2701

SDA1C wrote: »

AWESOME! Please do me the favor of figuring it with 99.7 and 115.4.

Generalizing nwohlford:
= 10 * log (10 ^ [db1/10] + 10 ^ [db2/10])

so 99.7 and 115.4 would be 115.55

So, really not perceptible. However, in an actual room, you'd get all kinds of hot spots and low spots depending on the standing waves and phase cancellation.

SDA1C

No more than an exercise in window replacement then lol. Would you be so kind as to compare db to spl for me? I'm not sure I understand the difference.

unc2701

this:
http://www.sengpielaudio.com/calculator-soundlevel.htm

SDA1C

Thanks unc. I just read that lol. The whole spl measured in db but bd not measured in spl thing still throws me a bit but I get the jist for the most part.

Joe08867

Only time I ever tried anything like this was testing out my Yamaha 18" Pro audio subs in my HT. I had 500 watts going to each along with 2 pairs of SDA2's getting about 250-300 a piece. The SPL in the room was high but not to my ears as much as my body. It was like being front row at a concert, but the music sounded clean and clear.

SDA1C

My curiosity started running when I had the live rig set up in the basement and the ht going up stairs. I got out my spl meter and it sort of went from there. Actually the whole ordeal has sort of turned my direction a bit to a bada$$ (and I mean Bad ..A$$) sub woofer. I have one and its ok but I came across a thread about IB and am very intrigued by this whole thing. I am certainly in the crowd of quality over quantity but at this point I want to explore more feel than hear.

I found this fellow http://www.decware.com/newsite/contacts.html and spoke to his wife this morning. It's high time I feel a folded horn.

1C