justin_tx_16 Posted September 12, 2003 Share Posted September 12, 2003 My roommate and I got in an "argument" today on the follow. One speaker playing at 20 watts puts out say 90dB Two speakers playing at 20 watts each puts out xxdB One speaker playing at 20 watts puts out 90dB One speaker playing at 40 watts puts out xxdB Same idea, different wording: One speaker playing 90dB Two speakers playing 90dB each = xxdB Passive crossovers are the worst possible for audio and are rarely used. Foam surrounds always sound better but rubber surrounds always last longer. The components inside a speaker are far, FAR, less important than the design. Ported speakers are always the best way to go. 3dB increase is twice as loud 6dB increase is twice as loud Putting a subwoofer on top of a table, stand, shelf or desk is bad because... Playing one speaker at 60 watts putts out the same spl as playing two speakers at 30 watts. There is a maximum possible sound pressure level Auto-Off options on subwoofers are useless because they often turn off right in the middle of your movie. A home theater with "perfect" imaging rarely, if ever, has decent imaging for music. The Harry Potter series is stupid and for little kids. That is all We must assume in these situations that the same speaker is 0being used each and every time. If anyone wants to fill in the blanks here, please do. I cannot convince my roommate or one of our neighbors such things as doubling wattage increases volume 3dB (in most cases) and that a 6dB increase feels sounds like twice as loud. Thanks Quote Link to comment Share on other sites More sharing options...
cluless Posted September 12, 2003 Share Posted September 12, 2003 The Harry Potter series is stupid and for little kids. BAHHHH....I read adult books in my childhood and now I read child books in my adulthood. And I feel that I am now more enlightened. Quote Link to comment Share on other sites More sharing options...
MrMcGoo Posted September 12, 2003 Share Posted September 12, 2003 Justin, Let me answer the easy statements: Harry Potter is stupid and just for little kids.--There is a faculty member in my department with an IQ north of 150 that loves Harry Potter. The fact that J.K. Rowling's books teach children to read is also greatly appreciated. Your roomie should be careful; he may offend the faculty. Ported speakers are always the best.--NHT is an acoustic suspension speaker if I'm not mistaken and seems to be very highly regarded. Bill Quote Link to comment Share on other sites More sharing options...
justin_tx_16 Posted September 12, 2003 Author Share Posted September 12, 2003 I did not state which of these are my opinions, and which are his, or rather, our beliefs. I will state this one... Harry Potter is one of the greatest books I have ever read, and I have read many books. I feel a little guilty. In one month I read the entire series, at least 2500 pages. It took me an entire year to read the bible... Quote Link to comment Share on other sites More sharing options...
davmar Posted September 12, 2003 Share Posted September 12, 2003 Justin_tx_16: Have the doubters log on and drink of the fountain of knowledge here, some member take some LS and a tube amp and blow there spikes out! My neighbor just moved in and we were talking stereos and when he said my fifty watt amp will sound fecal (not many 12 year olds will know that word, gotta watch out for the kids) He came over and we played to him is the best song ever is In Memory of Elizabeth Reed, by the Allman Brothers Band. He was a little tipsy, and I cringed as he went for the volume knob on the Stingray. He cranks it up to almost 12 oclock, he listens, the song ends and he CRIES. I had to throw the drunk out! Is your roommate an electrical major like you? There are all the references to audio in these pages. If you can not find what you exactly want to know you can find lings to what it is. Speaking of reading, a 10 year old was reading Swiftly Tilting Planet; I bought it and read it and the following two, and would recommend it to any child! (big or small) Quote Link to comment Share on other sites More sharing options...
WMcD Posted September 12, 2003 Share Posted September 12, 2003 Maybe I can help a little bit. But in writing the below, I see that I may have injected some issues which are difficult to follow. Doubling electrical power to a single speaker increased output by 3 dB on the RS meter. There is a problem of analysis when using two speakers. I've read from D'Apallito, that if both are fed by random noise not corrleated to each other, then you have the expected 3 dB increase. This is to say, noise is like raindrops falling. The never pile up on top of each other, but there are twice of them in the overall area, assuming two different souces of rain drops. However, if they, the speakers, are fed by the identical signal (noise or otherwise), and they are closely spaced, then there is a 6 dB gain. I've not really grocked this entirely. It does have to do with mutual coupling. How much air can be pushed. And the condition of pushing it. In this latter case, the first speaker output increases the pressure in front of its neighboor by whatever. Call it 3 dB of pressure. Then the second speaker, acting in phase (with a sine wave or identical rain drops in time), pushes the pressure up another 3 dB, to make it 6 dB. Of course this also must take into account that the second speaker is pushing up the local pressure in front of the first one, too. Hence it is called mutual coupling. This has some intuitive sense in that we realize that the moving diaphagms are pushing against ambiant pressure and making it more positive when the diaphargm moves forward. This comes into play in a few situations which we can appreciate without math. If a first woofer has twice the area of a second smaller one, then it is like two small woofers, side by side and mutually coupled. So, size of one diaphragm does matter in efficency. There is a sort of mutual coupling in one, single, diaphragm unit. Also, you may have seen PWK's illustration of why corner loading works. In a visual illustration, the corner is optical mirrors and we see the multiple reflections of the image of the K-Horn and especially its mouths against its corner background. This is to put up a visual illustration that the pressure created by one bass unit in a corner and it creates an image of it, via the hard walls, in terms of pressure. And sound is sound PRESSURE level (SPL). We really want to increase energy transfer by having pressure trapped, so we can work against it. This assumes that the reflection is in phase with what comes out of the speaker. At low frequecies (long time to change) it is. This is all the same sort of logic. A pressure wave hits a wall and then the pressure is contained. Gee, the walls don't push back like a another diaphragm (with two diaphragms, but they are not like ambiant space either). In this situation it comes from having a hard surface trapping it, rather than a another driver. Lets go back to the original situation of two speakers with random noise pulses. Just to make a point. If the rain drops of noise are random as output from two adjacent speakers, then they are unlikely to occur at the same time and therefore do not create a situation where there is a pulse from one being present in front of the diaphagm of the other to increase the local pressure. On the other hand, there are twice the number of them. The other issue is "what is loud" according to our ears. Does the reading of another 3 dB on the meter "sound" twice as loud? No. Though it is subjective. My understanding is that 10 decibels on the meter increase is necessary to make it sound "twice" as loud to our hearing. And we know that a decibel is a 1/10 of a "Bell". My understanding is that Dr. Alexander Graham Bell found this relation in subjective loudness perceived by us humans. So the "Bell" or 10 deci (1/10th) of a Bell should lead to a perceived "twice as loud". Of course maybe we should check this out with our systems. We have RS meters, speakers, sources of random noise (though maybe not un correlated in left and right channels.) However, do crank up the RS meter with your friend. I think you'll find that 3 dB does not sound like much of an increase to your ears even though it is twice the electrical power. Best Gil Quote Link to comment Share on other sites More sharing options...
davmar Posted September 12, 2003 Share Posted September 12, 2003 oops Quote Link to comment Share on other sites More sharing options...
kenratboy Posted September 13, 2003 Share Posted September 13, 2003 Hey, don't talk smack about Harry Potter. I read Clancey, Cussler, Crichton (sp? and all those), etc. and I need something different now and then. Quote Link to comment Share on other sites More sharing options...
formica Posted September 13, 2003 Share Posted September 13, 2003 ---------------- One speaker playing at 20 watts puts out say 90dB Two speakers playing at 20 watts each puts out xxdB ---------------- 90db? I don't think that is what you/he meant... but they each put out 90db. Put then together and you get either 93db or 96db (as per Gil's description). For full coupling to occur, they must be very close (such as two subs, one on top of another)... but my understanding is stereo speakers are far enough to have both additions and cancellations, never giving you the 6db ---------------- One speaker playing at 20 watts puts out 90dB One speaker playing at 40 watts puts out xxdB ---------------- 93db ---------------- Same idea, different wording: One speaker playing 90dB Two speakers playing 90dB each = xxdB ---------------- 93db to 96db as it will vary with frequency due to their interaction as well as the room interaction. ---------------- Passive crossovers are the worst possible for audio and are rarely used. ---------------- Almost every speaker made includes one... And both passive and active x-overs can be well or poorly designed. ---------------- Foam surrounds always sound better but rubber surrounds always last longer. ---------------- Foam isn't always better but rubber does last longer. ---------------- The components inside a speaker are far, FAR, less important than the design. ---------------- Depends on the persons priority, BO$E sells millions on only design... A good speaker requires both (eg: put a Tempest driver in a 1ft3 box and it'll sound pretty boomy) ---------------- Ported speakers are always the best way to go. ---------------- Again, depends what you are after... both can be great. ---------------- 3dB increase is twice as loud 6dB increase is twice as loud ---------------- And I'm twice as sexy as my brother... who's to argue a subjective term? ---------------- Putting a subwoofer on top of a table, stand, shelf or desk is bad because... ---------------- It may fall off? Aerial SW12 comes with a mini stand. A bass unit (like the computer speaker ones) isn't actually a subwoofer as it's x-over is pretty high... this makes it easy to locate... so placement will be more critical than a subwoofer. ---------------- Playing one speaker at 60 watts putts out the same spl as playing two speakers at 30 watts. ---------------- Wow, you guys argued this a long time? Depends on how close they are to each other... ---------------- There is a maximum possible sound pressure level ---------------- Yes... but it may not be what you're thinking. (warning: this is a personal theory, opinions may vary) This is more of one of those "if a tree falls in the forest" questions... If an air pressure can no longer be converted into a nerve impulse by the ear (human or animal) is it still a sound, and it's level still SPL? In other words, a sufficiently high SPL will cause permanent hearing damage, but there still is a pressure... is this still called sound? I'm guessing this wasn't your original question... but rather you were wondering if there is a physical limit to the actual pressure? Well given that sound requires air, the limit pressure would be that required for the solidification of air. ---------------- Auto-Off options on subwoofers are useless because they often turn off right in the middle of your movie. ---------------- Has never happened to me... I'm guessing a defective sub with to low a signal sensitivity. ---------------- A home theater with "perfect" imaging rarely, if ever, has decent imaging for music. ---------------- Are we talking stereo playback, multichannel playback, or one of those "Hall" modes? I'm from the school of imaging is imaging... recordings vary greatly... and hall modes definitely to be avoided. ---------------- The Harry Potter series is stupid and for little kids. ---------------- Yes... as it lacks the essential ingredient for a great adult flick... explicit $ex (you were talking xxx?) on the other hand Harry's a light enjoyable tale... later... Rob Quote Link to comment Share on other sites More sharing options...
dodger Posted September 13, 2003 Share Posted September 13, 2003 Greetings: In checking my books and memory, two (2) - three (3) decibels is the point at which a human being can note a change in volume level. In order to gain a three (3) decibel change, a doubling of the amplifier power output is needed. It is logarithmic. Example: one (1) watt = 100 db to effect a perceptible increase to the average person you should increase db to 103. To effect the three (3) db gain, you would go to two (2) watts. Then the following for each 3 db gain: 1 2 4 8 16 32 64 128 256 512 1024, etc.. You can try what is perceived as an increase with a good sound level meter and a steady tone. As far as I remember, and I believe may also be noted in one of the Dope from Hope treatises, that is the way of effecting increase in sound level. Also a speaker putting out 100 db with one (1) watt at one meter will have asignificant drop off as you move each meter away from the speaker, thus you will need more than the one (1) watt to produce 100 db if you are 3 meters away from the speaker. Furnishings, wall reflection, wall surface and composition and type of speaker will add to variables. Win dodger Quote Link to comment Share on other sites More sharing options...
HDBRbuilder Posted September 14, 2003 Share Posted September 14, 2003 Justin, Face it...you are now in an environment at college where you will encounter many people who espouse knowledge that, in fact, is REALLY their aquisition of "facts" that are erroneous, at best. In other words, they are full of BS...but they DON'T REALIZE IT...and, even worse, they actually BELIEVE it...and you will have a difficult time, at best, trying to convince them otherwise! My advice is to let your H/K 430, with its meager 25 WPC, and your Heresys, with their unported cabinets and corrugated paper woofer surrounds, do the talking for you once you get them up there...pretty simple! Hearing is believing! As for surrounds, foam deteriorates more rapidly than rubber...but BOTH of them deteriorate MORE rapidly if exposed to ozone or direct sunlight. You failed to mention accordioned paper surrounds, though...like those on your Heresys. Just suffice it to say, that paper surrounds outlast either foam OR rubber ones, provided the woofers are not overdriven, and provided the woofers remain in a home environment instead of a vehicle environment(prone to much more UV and ozone damage). The simple way to prove this point is to note the age of your Heresys as opposed to the age of speakers originally supplied with foam or rubber surrounds(anything else NOT having corrugated paper surrounds that you find as old as your Heresys will have damaged surrounds by now)...simple, huh? Quote Link to comment Share on other sites More sharing options...
justin_tx_16 Posted September 14, 2003 Author Share Posted September 14, 2003 Well HDBR, the speakers I bought for college I was not able to bring to college. That is heresy! Next semester, more likely next year, they will be joining me up here. I created this excel sheet with data from someone on this bulletin board.... Anyways, it is a dB/watt/SPL chart. http://soundwise.org/klipschubb/spl-watt-dB.xls I showed that to my roommate, who has been staying at his girlfriends the past two days, and he did not say anything, just said yeah, 3dB with doubling the power, contradicting himself, not sure if he knew he was contradicting himself though haha. I started playing the sound track to Chicago when i was doing laundry last night and realized that my iPod and its headphones would just not do. I pretty much only ever played Chicago on my Heresy's, I am really missing those guys! Can't wait for thanksgiving... looking forward more to seeing my babies than my family LOL! Quote Link to comment Share on other sites More sharing options...
IB Slammin Posted September 14, 2003 Share Posted September 14, 2003 Andy, I can't believe that you could resist....... Hay Justin....HOW 'BOUT THEM HOGS!!!!!!!!!! Terry Quote Link to comment Share on other sites More sharing options...
justin_tx_16 Posted September 14, 2003 Author Share Posted September 14, 2003 tell me now, is a car sub capabile of hitting 172dB at any frequency?... right.... Quote Link to comment Share on other sites More sharing options...
jtkinney Posted September 15, 2003 Share Posted September 15, 2003 Not at any frequency. The car sub depends on overpressurization to hit that max SPL and at higher freq's it can't do it. Max SPL depends on the air pressure in the listening room. Find a Physics book for specifics, but as I remember it, the higher the pressure, the higher the max SPL. Out in the open at sea level, I don't think it's possible to hit 172 dB. Quote Link to comment Share on other sites More sharing options...
Frzninvt Posted September 16, 2003 Share Posted September 16, 2003 Yes it is possible and has been done in SPL contests. The record is actually higher than 172db, I believe closer to 175db. I have a friend that has a Car Audio shop and he can regularly hit 155-160 in his Dodge Caravan with only 2 15" DVC MMats Juggernaut Subwoofers, huge sums of MMats digital amplification, and lots of spare batteries, and most importantly a hell of a sound deadening job. My 1994 Camaro was capable of 140db with 2 10" Atomic Pro drivers in a bandpass enclosure in the rear well, with a slotted port aimed at the rear window. Quote Link to comment Share on other sites More sharing options...
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