Several kW speaker inside an apartment - what would happen? - Page 1
Forum section: electronics / general

author: daqq
author_rank: Super Contributor
timestamp: June 23, 2017, 09:50:04 pm
content: Hi guys,While reading this thread (https://www.eevblog.com/forum/projects/bullshit-alarm/) I remembered a cheap "hi-fi" system a friend had, ofcourse it was labeled with a PMPO power of several kW. The non-bullshit power rating for that size of speakers would be around 8W or so.So, what would happen, if you actually turned on a, say, 10kW loud speaker inside of a small apartment, on full power and play something nasty?Aside from severely annoying the neighbors, would there be any noteworthy effect? Smashed windows perhaps? What about the health issues? After a few minutes, could someone get their hearing damaged?Thanks,David

author: WastelandTek
author_rank: Frequent Contributor
timestamp: June 23, 2017, 10:15:13 pm
content: I just love the "wattage" ratings on audio gear.My singer recently showed up with this "600 watt" (right on the box, big letters) powered monitor. I turn it over...2.5A fuse, 120V...But getting to your question, I have seen youtube vids of powerful car audio systems where the bass synced with the shutter speed, the deflection of the body panels and glass was astonishing

author: The Soulman
author_rank: Super Contributor
timestamp: June 23, 2017, 10:53:46 pm
content: Warning: High sound pressure levels can and will destroy hearing in an instant, even a collapsed lung is possible.Electrical power is less than half the story, it is acoustic energy that we want for that we also need efficient transducers (loudspeakers).High to mid-range frequency's are fairly easy to reproduce at high SPL's by horn-loaded compression drivers,they have a efficiency of up to 110dB measured at 1 meter for each Watt put in, so even 0,1 Watt can easily damage your hearing at 100dB.More fun and a lot harder are (really) low Frequency's, especially in a enclosed space (apartment) speaker placement becomes critical and frequency dependent to produce a good standing wave (normally avoided) with plenty of acousticalpower you can let windows shake and doors rattle. (I even cracked a wall once with about 100 Watts..)Regular subwoofers aren't very good for this because they usually don't work efficiently below 40 or even 50 Hertz (don't have to for normal music).For this we are talking sub-sonic: 5-20 Hertz so frequency generator and custom speakers.Actually with 30Kw of power and efficient speakers that can handle that and a room that supports a low enough standing wave frequencythat happens to match the resonant frequency of the brick walls, you can take down a house, maybe.

author: Electro Detective
author_rank: Super Contributor
timestamp: June 23, 2017, 11:22:13 pm
content: The Soulman is on the moneyThis gentleman may be of assistance too

author: Ampera
author_rank: Super Contributor
timestamp: June 23, 2017, 11:22:28 pm
content: I would appreciate it if someone came up with a demolition company that used loudspeakers to take down houses with terrible songs.NEVER GONNA GIVE YOU UP*CRASH*

author: station240
author_rank: Unknown
timestamp: June 24, 2017, 01:43:44 am
content: Original giant speaker (BTTF)And someone just had to make a real version.7kW big enough ?

author: cdev
author_rank: Super Contributor
timestamp: June 24, 2017, 03:28:36 am
content: Well, your body presents an impedance mismatch to the sound waves, so when they enter your body there must be some standing waves, reflections, etc. It likely matters how much water and fat there is in people. Everything has a resonant frequency.. If in fact it exists and is not an urban myth, I could see some frequencies perhaps causing enough oscillation and loss in heat to perhaps present a risk of.. SHC...

author: Brumby
author_rank: Unknown
timestamp: June 24, 2017, 03:58:21 am
content: Immediate issues: Hearing loss..... and expect the Police to kick down your door. You won't hear them knock.Potential issues include other physiological damage and structural stresses. Get some resonance happening and you never know what will happen.Speaking of resonance, I seem to remember hearing about some experiments with large structures using a comparatively small device. The device set a relatively small mass oscillating at the resonant frequency of the structure. It did not show any ill effects quickly, but over time, the structure(s) also exhibited oscillation at noticeable and then troubling intensities.So, as long as the input energy from a resonant source exceeded the losses from the resonant system, you could end up with some pretty dramatic results.

author: amirm
author_rank: Regular Contributor
timestamp: June 24, 2017, 04:17:39 am
content: Here is a system from a guy that used to hang out on our forum. He goes by the alias, "basspig" for obvious reasons:

author: amirm
author_rank: Regular Contributor
timestamp: June 24, 2017, 04:25:34 am
content: Quote from: Brumby on June 24, 2017, 03:58:21 amReminds me of the collapse of the tacoma bridge near us:

author: james_s
author_rank: Super Contributor
timestamp: June 24, 2017, 05:03:35 am
content: When we were about 15 my friend and I built a subwoofer in the corner of his room with an old 12" driver in a big tuned box, I think the amplifier was only about 50W but we managed to knock a painting off the wall in the livingroom downstairs. It's all about the frequency, in that case I suspect we hit the resonant frequency of the wall on which the painting hung. I don't think you'd actually do serious damage in most cases, you'd just piss everyone off and possibly damage your hearing depending on the frequency involved. Beyond a point I don't think adding more power makes it any louder, there's only just so much air in a room to move around. 10kW is probably only going to sound modestly louder than 200W.

author: amirm
author_rank: Regular Contributor
timestamp: June 24, 2017, 05:40:46 am
content: Well, if you want to knock things off, there is always this:

author: cdev
author_rank: Super Contributor
timestamp: June 24, 2017, 06:03:07 am
content: James, you stumbled on the magic formula for bass nirvana..I have an old corner Klipschorn with a 15 inch woofer and metal horn - multicelled horn, it looks like a microwave antenna..Between the two it can attain extreme levels of undistorted sound. It goes through you.Somebody would have to be dead not to want to dance.Quote from: james_s onTodayat 23:03:35

author: ruairi
author_rank: Frequent Contributor
timestamp: June 24, 2017, 06:06:12 am
content: My day job is as a mastering engineer but I work part time setting and tuning up high end studio speaker systems for artists and producers that you would all be familiar with, these systems run anywhere from $20k to $175k.The largest system I've set up is in the private studio of a well known producer here in L.A. It has somewhere around 11,000 watts of available amplifier power per channel in a room that's somewhere around 600 - 700 sq ft. The effect of listening to that system turned up is profound, a very physiological fight or flight response. I started sweating and the hair literally stands up on your body.

author: Brumby
author_rank: Unknown
timestamp: June 24, 2017, 06:51:33 am
content: Quote from: ruairi on June 24, 2017, 06:06:12 amFrom your anxiety - or the sound pressure?

author: ruairi
author_rank: Frequent Contributor
timestamp: June 24, 2017, 07:05:46 am
content: I've only experienced sound levels like that a few times, and for brief periods. The extreme low frequency content seems to trigger a response in my body that is involuntary. I'm the one controlling the level so panic is not the issue!

author: BradC
author_rank: Super Contributor
timestamp: June 24, 2017, 07:16:29 am
content: Quote from: ruairi on June 24, 2017, 07:05:46 amThe brown note?Years ago we had a small set up in a ballroom for a drum 'n bass gig. Not a lot of power. The subs were about 2400W RMS per side (3 tuned 800W cabinets and class AB amps). With the aid of the right music at sound check we took out a couple of windows and destroyed a couple of hundred glasses in the bar (as they vibrated out of their racks).I used to use good 3M earplugs and then a decent set of ear muffs over those. I've run 1600W RMS in my living room with a small and relatively inefficient driver. Aside from upsetting the neighbours there were no major issues, but I had everything remove/tied down first.

author: WastelandTek
author_rank: Frequent Contributor
timestamp: June 24, 2017, 07:24:20 am
content: Quote from: ruairi on June 24, 2017, 06:06:12 amnice post, I have to ask if you have any experience with the JBL 4350 monitors?I have often wondered what it would have been like to be present at The Who's mastering sessions.

author: ruairi
author_rank: Frequent Contributor
timestamp: June 24, 2017, 08:02:07 am
content: Quote from: WastelandTek on June 24, 2017, 07:24:20 amI haven't heard the JBL 4350 and have never seen them in a recording or mastering studio, sorry!

author: Electro Detective
author_rank: Super Contributor
timestamp: June 24, 2017, 08:39:46 am
content: No one needs hearing loss, subtle brain damage,or p!ssed off neighbourswho may not gas if one day your house is burning down due to a gross electrical/electronic mishap/blunder,with YOU in it BBQing away...i.e. "no more loud @sshole next door, and no more cig butts and dog turds thrown over every time we complain"Big loud sloppy bass frequencies are boring and usually pumped out by amateurs with small peckersThat's what their ex-girlfriends tell me

author: MosherIV
author_rank: Super Contributor
timestamp: June 24, 2017, 08:45:57 am
content: I remember Mythbusters did a prgram about this. They tried to reproduce 'the brown note' - failThey also tried 1KWatt with a 4 foot woofer in a car to try and blow the windows out - do not remember the out come.

author: cdev
author_rank: Super Contributor
timestamp: June 24, 2017, 02:38:17 pm
content: Pro quality Mackie active studio monitors with built in amplifiers are extremely flexible. Look at the extremely rugged and powerful systems pro studio rental companies offer to rent.They come with tripods to get them up and have active feedback systems too so they can produce a very tight, balanced sound both indoors and out.

author: SeanB
author_rank: Super Contributor
timestamp: June 24, 2017, 08:23:10 pm
content: Interesting bit in here about the satellite shake and bake testing that ESA does to the commercial sattelite s they manufacture.http://omegataupodcast.net/242-satellite-testing-at-estec/Pics also there of the facility and the equipment, plus some very interesting discussion as well. Yes an hour and a half of audio to listen to, but well worth it in conjunction with the photos from there.

author: james_s
author_rank: Super Contributor
timestamp: June 25, 2017, 12:45:07 am
content: I vaguely remember seeing that mythbusters. I think they went about it in the wrong way, I have little doubt that it's possible to knock a window out of a vehicle but it's going to depend greatly on the design of the vehicle, the method of attaching the window and the frequency of the sound. I don't think you'd do it by raw power, it's going to take resonance. I've certainly had various parts repeatedly vibrate apart in cars, and I've had a windshield nearly fall out after the bond gradually deteriorated with age, baking in the sun and exacerbated by body flex once the joint started to fail.I should add that this was all due to normal mechanical vibrations in the car, no crazy audio systems involved.

author: Red Squirrel
author_rank: Super Contributor
timestamp: June 25, 2017, 02:10:50 am
content: We were tuning the equalizer at my church since we got a new sound system so we used a sine wave generator to try to find the resonant frequency of the room. Once we hit it, very interesting things happened. Stuff like wood strips on the walls started to vibrate and depending on where you walked you could feel it in your head, like some places were more intense than others. I imagine if we had actual kw worth of speakers pumping that for a long time things would start to break and it would probably be dangerous to the ears. The speaker we have is "rated" at 1000w (a fairly standard size for large PA systems) and the amp is higher, though we did not have it anywhere near it's max, and we all know those ratings are mostly BS anyway. But if you were to actually do that with several kw I'm pretty sure it could start to cause things to break, loosen up etc, maybe even take out windows.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: June 25, 2017, 02:48:14 am
content: Quote from: SeanB on June 24, 2017, 08:23:10 pmI once got to participate in a publicity tour of a similar facility. They had a 100 kW tRMS amplifier driving an electromagnetic shaker. The amp was huge, perhaps 3 meters wide, 2 meters tall and a couple of meters deep. We walked onto the driven platform while they drove it with the audio from a local radio station. That had to be one of the least efficient speakers ever used. even at max power it wasn't rock concert level. I later worked at a facility that had another copy of that 100 kW amplifier driving a shaker. It was seldom used because maintenance and calibration were such a PITA.So the two keys are efficiency in converting input power to acoustic power and resonance for coupling with the target. Since resonance is often key to efficiency in acoustic power conversion there could be interesting problems in getting the whole thing to work.

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: June 29, 2017, 11:57:35 am
content: Bear in mind that, depending on the design of the building, you can remove a wall with a surprisingly low pressure - as little as 2.5psi. Removing a wall from half way up a tower block is not good!https://en.wikipedia.org/wiki/Ronan_Point

author: james_s
author_rank: Super Contributor
timestamp: June 29, 2017, 05:00:57 pm
content: That's actually not very surprising, I mean if you think of how many square inches of area the wall in even a small bedroom is, multiply that by 2.5 pounds and you've got quite a lot of force.

author: SeanB
author_rank: Super Contributor
timestamp: June 29, 2017, 05:55:39 pm
content: Quote from: CatalinaWOW on June 25, 2017, 02:48:14 amNothing compares in fuel to noise efficiency than a jet engine at full afterburner on a ground test bed. 150dB 100m away, and we were behind the sound baffles, the collection of scraggly trees and the entire complex as well. might be partly responsible for some of my hearing loss that, plus just the regular noise from the non afterburner jet engines as well.

author: Simon
author_rank: Unknown
timestamp: June 29, 2017, 08:09:52 pm
content: Quote from: Brumby on June 24, 2017, 03:58:21 amNot so much in the UK, if the source of noise in in the house the police are powerlessI do remember tell of someone doing low frequency experiments in a building and the sounds ending up in the ventilation system and causing problems. Not sure if this is an urban myth though. Of course we have walls of Jerico

author: schmitt trigger
author_rank: Super Contributor
timestamp: June 29, 2017, 08:26:01 pm
content: Quote from: SeanB on June 29, 2017, 05:55:39 pmIndeed! a jet engine on afterburner is beyond loud.Similarly....The loudest continuous man made sound (A-bombs are far louder, but they are not continuous) is the one made by a Saturn V rocket during liftoff.

author: james_s
author_rank: Super Contributor
timestamp: June 29, 2017, 09:54:51 pm
content: Quote from: SeanB on June 29, 2017, 05:55:39 pmIt is indeed extremely loud, but I'm not sure how it compares in terms of fuel to noise efficiency. Something like the LM1500 which is an industrial turboshaft version of the J79 without afterburner produces 10,000 HP which is about 7.5MW and that's extracting about 30% of the energy from the fuel into mechanical energy. That means around 22MW of fuel energy being fed into the machine, and I'll conservatively estimate that an afterburner is going to more than double that. How loud is a 50 Megawatt amplifier driving an enormous array of speakers? That's starting to sound like a Spinal Tap concert.I really can't think of any practical devices that produce more sustained noise than an old fashioned turbojet engine though.

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: June 30, 2017, 10:20:52 am
content: ... unless you take advantage of the inverse square law and just stand a bit closer. Long story but I had the opportunity to help out ringing an extremely large bell a few moths ago. The regular folks I went with who are keen bell-ringers say they've measured it at 145dB and it's rung by two people swinging it back and forth by hand...I was sceptical about the 145dB claim because I understand how logarithmic scales work but I was there wearing -35dB earplugs and it still felt about as loud as using an angle grinder without ear protection so I can believe it. My ears were distorting the sound and were ringing for quite some time after. I'm used to being vibrated to bits by bass-bins at music events but it's a very strange feeling getting the same physical effect in the high 100s of Hz...Edit: you don't get a sense of just how loud it is on the video but it's surprising how little energy you have to put in to it. It weighs nearly 10 tonnes.https://youtu.be/Y8gHziy278Q?t=2m40s

author: WastelandTek
author_rank: Frequent Contributor
timestamp: June 30, 2017, 05:25:34 pm
content: Quote from: DenzilPenberthy on June 30, 2017, 10:20:52 amegad! that one lass is jumping off the ground to grab and pull...wow

author: babysitter
author_rank: Frequent Contributor
timestamp: June 30, 2017, 06:18:05 pm
content: sound level causes a pissing contest often...Just recently I had a wannabee stage techie bragging about "Company XYZ sells a 180 dB system yadda yadda yadda"I was short before pointing to the ESA ESTEC/LEAF facility, able to test at around 156 dB levels, and Project Pluto which was expected to kill not just with its nukes and radionuclide-spewing emissions of the drive, but also with its 162 dB noise.