posted
I have a friend who has turned to me for help, and I have helped him out with the basic principals. However he is doing Physics and for some reason decided to go about designing the loudest (he also wants lowest, but I told him you cant have both from the same setup) bass enclosure possible. I have suggested to him that if you had to theoreticly design the ultimate system pehaps matching the Driver, Sub box and Cabin size would have a significant effect, also matching wave lengths etc..
Could some extra clever people (I know you are here )please give some of their ideas ont the loudest "theroetical" system.
posted
With lots of power, amplifiers, subwoofers and money you could have a very loud and low vehicle.
Posts: 760 | From: California | Registered: Jul 2001
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posted
Yeah I realise the basics, but he is talking "Ultimate" Navy sonic cannon type ultimate. I have told him he has started chasing the audio equvalent of the "Holy Grail" but he really wants to prove something with this paper. Money is not an issue as this is a theory based paper. Heck even if the perfect vehicle doesnt exist and you could never get an amp to produce enough power, he would like the technical information needed to to come up with a plan for the loudest vehicle. stretching right to the ends of the laws of physics as far as compression and max pressure can go. What would be needed to reach the ultimae goal?
I know its asking a lot but just some ideas and input would be nice
posted
The ultimate in sub box technology theory is the horn enclosure. As long as space is of no concern and he has money to burn on the box, this box will pump out some stomach wrenching bass.
a good backup would be a carefully designed bandpass, not for beginners. He can always build a ported box as a backup and play with tuning and box stuffing.
Posts: 768 | From: Ottawa, On, Canada | Registered: May 2000
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posted
There is no such thing as a physical limitation on sound pressure. 194 db is the limitation of sine wave modulation because you will reach a vacuum, however, one can make the pressure side of the equation even larger.. There is no limits.
ShadowStar
-------------------- You can't build a reputation for what you're GOING to do.. But you can build one for TALKING about it!
It's all about knowledge, love and respect.
Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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posted
You should probably worry more about hitting 180 or 190 then worrying about surpassing the so called barrier of 194 dB. Shadowstar is right though, there's a limit on how low the pressure can go, but not on how high it can go. Just seal up your car very well, fill it with water and hitting 200 dB shouldn't be all that hard. Water-proof amps are hard to come by, if possible.
Posts: 768 | From: Ottawa, On, Canada | Registered: May 2000
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posted
... the military has water-proof amps that can perform completely immersed in water ...
-------------------- (1) PPI AMP PCX-2200 (800 Watts @4ohms Bridged) PCX-480 for my highs (2) DD 3512a's in a 4.4cube box with 50sq. inches of port tuned to 33Hz Street 1-2 [TEAM DD] 147.7dB My Sound Domain page Posts: 1655 | From: Tucson, AZ | Registered: Jul 2001
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posted
waterproof amps, eh? Maybe I should consider building some subs for when I'm swimming in the pool. Now all I have to find is a waterproof sub. Maybe if I make a waterproof bandpass and make a port with lots of volume and firing down. That would be nuts, I wonder if bass is audible underwater.
Posts: 768 | From: Ottawa, On, Canada | Registered: May 2000
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posted
jon_audio - unfortionatly, the world is made of trade offs. You cant maximize everything.....
shadowstar, I dont think 194 is the limit anymore, but I do for speakers. In an explosion, you could have a huge pressure increase, say 100psi, then a drop to neat 0 psi and continual oscillations untill it levels out. that would count as very high spl,Right?
why is it Im always under the influence when on termpo? tonight I visisted long Island a bunch of times
Posts: 1259 | From: Fullerton. CA ,USA | Registered: Oct 1999
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posted
This is what you have to do: Get a completely flat (or almost) speaker. It can be home based. Put it in you trunk. With a spectrum analyser watch the resonance frequency of the car. Go to the shop and by a driver with that resonance frequency and Build a box tuned to that frequency. You're there.
CarAudiolover
PS: Ops'... There are no speaker's with perfect flat responce.
-------------------- No more LOUD!!!
Posts: 1 | From: Portugal | Registered: Aug 2001
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posted
I know a lot about Physics. I have been studying accoustics for about a year now. I can tell you exactly what the resonant frequency of your car is, once I get a LOT of info. I am going to try to explain some things before we get started on any kind of physics, to make sure that you know what you are getting into.
1. You (yourself and/or him) have to be good at Algebra, and you must be able to UNDERSTAND what is going on. You cannot just learn some formulas, if you do only learn formulas you will be lost. I will tell you what is happening and why, but you MUST tell me if you don't fully understand any aspect of what I am typing. Knowledge and understanding go hand-in-hand.
2. You may have to have a scientific calculator. You can work it all out by hand, but I would recommend a TI 34 II Plus (about 15 or 20 dollars), or greater... much faster than hands.
3. You must be willing to calculate before every event, or any other system test. This gets monotonous, but is necessary to assure accuracy and maximum SPL.
4. I will break down everything into seperate sections, I will post conversions if need be.
If you feel comfortable with the above tell me, then we will begin.
posted
by the time that you reach 194 dBs (the limit itself is 193.x, I just rounded it up), you will have distortion. Do You know what this type of distortion looks like, you all know what it sounds like. It is very similar to the distortion of a cheap amp turned up too high. This is how it would look like (Theoretically): (top is the first half wavelength, the positive SPL, in relation to atmospheric pressure (AP), bottom is the second half wavelength) @approximately 196.x dBs
.................*..*.....=29.x PSI above AP ............*............* .........*..................* ......*........................* ....*............................* ..*................................* *-------------------------*-------
*-------------------------*------- ..*................................* ....*............................* ......*........................* .........************=14.xPSIbelow AP
The percent THD taken by the second half wavelength per cycle due to the limit of vacuum will increase as SPL does, but may never reach or become greater than 50%. If you do not understand this, ask someone about "Fractal Goemetry". It will take too long for me to explain on a post.
The . is used as a physical spacer, due to this forum's lack of recognising spaces in access of 2.
Could you explain these? Is this where you'd have one chamber firing into the next? Also, how do you calculate the proper tuning for spl and sq? Steve
Steve, I've had a lesson for more than an hour in designing thse, and that's only the SQ side of things. They shouldn't really look like most people think they should which makes explaining the design rather difficult. Also it's different for all subs.
What box modelling program do you use?
As far as what it is, one type is a ported box firing into a ported box, one is a sub with a ported box on either side of it.
As a general rule tunings of about 30 and 100Hz are reasonable places to start, but it depends very much on the sub and application. You also need to know how to interpret the group delay for it to suit different musical tastes.
Perhaps I should get Erskine to make a video on advanced box design and construction?
-------------------- *hmm need to think of a new sig*
posted
Well I talked to a sound curvature engineer a while back... don't ask I have no clue what he did but he had a degree in it... I asked him how to make sound louder and he said that bending sound waves makes things louder. For this reason hatchbacks firing off the glass are so freakin loud. He did tell me however that curving a sound wave instead of bending it makes it louder yet. So theoretically if you were to put you sub in a loooong tube and just make the tube make a series of loops it would be the loudest. Now whether you put a ported or bandpass or just a sealed box at the beginning of all this I don't know what that would do.
-------------------- 97' Dakota 4x4 higher every day Sony CDX-C910 Sony mkII eq MbQuart 8's, 2 sets of 3-ways Picassos 9515 1 Tarantula 4 SVR 80-12's Sony SVP-DC1 Sony 10-disc changer Sony PS2 N64 2 monitors soon to have: 300 alts
Beginners Luck? Mobile Audio team DD Posts: 2106 | From: Whispering Pines, NC | Registered: Dec 2000
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Mouser (Colin's ) series tuned bandpass would reach a maximum of efficiency vs. box volume, however, said maximum of efficiency could (COULD) be surpassed with large volume ported chamber as volume goes to "very large" the efficiency gains of both ports in the series tune bandpass become smaller vs. the unloading effects of the larger box.
The phase between the port and the driver could then be maximized (a bit harder with both ports in the series tuned design) with the ported box to yield pretty close to maximum efficiency.. The only real way to increase the efficiency would be to further load the driver (what your engineer friend was getting at, I believe, boundary loading) which is the phoenomenom that the harder the surrounding air pushes on the driver, the more energy the driver can theoretically impart on the system (hence horn loading gives you lots of efficiency..)
Perhaps horn loading both sides of a driver and aligning the phase of the two horn outputs....?? Cha-CHING
ShadowStar
-------------------- You can't build a reputation for what you're GOING to do.. But you can build one for TALKING about it!
It's all about knowledge, love and respect.
Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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posted
Shadowstar, are you sure you've not been looking at my box? You are describing some parts of it rather well.
All will be revealed on Don's forum after finals. but for the moment stop thinking will you, making some of us nervous
I haven't really tried it for a normal application yet, but I've done some testing very much along those lines. proved my horn box had the horn loaded effect down to around 60hzish before.
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[ 09-20-2001: Message edited by: Mouser ]
-------------------- *hmm need to think of a new sig*
posted
i don't know much about horn load boxes but i do know they kick some major butt i have a pair of cv 18's(L-36) in a horn loaded box a really big box i have read alot of info about them and on the cv site it says that mine need 6 feet for the wave to form. I have tried this out in my back yard a few weeks ago and with in those 6 feet the sub didn't sound deep but after those 6 feet the sub sounds sweet the 1w/1m on the sub by itself is 101 but with in the box its 130 but my cv subs are not car audio subs i use them for djing(8ohms) but as soon as i get money for a max power 4ohm mono 12v amp im gonna put them in a astro van and see wut it does
posted
The loudest possible configuration would be where the mic position was triangulated by each sub... where each sub was timed in some way to position the same antinode of the same frequency at the same time at the mic... where all of the subs peak at the resonant frequency of the cab... where the box peaks at the resonant frequency of the cab... and when all that occurs at as close to 80 Hz as possible.
I have yet to see anybody reach anywhere close to meeting all of the above criteria. I assume hat that is so because of the fact that there are many atmospheric variables, like the main one temperature. People use lower frequencies because of their longer usable antinodinal length, which lowers max SPL but rises the chances that you will hit the mic with a significant portion of an antinode.
posted
the 2 sided horn idea sounds very nice. Aligning the phases would be damn tricky though. Also consider the benefits of flush mounting the cone of the speaker (or port or mouth of horn!) with the corner of a box will give you up to 18dB's of gain over free air. Also remember that the speaker cone stops moving at the helmholtz frequency of the port, so lengthening the port so that it is in phase with the cone will only be noticed for a few hertz above and below fb and even then, may not provide any additional gain.
Also, instead of being happy with the "stock" resonance frequency of your vehicle, you can always change it, by changing the temperature, pressure, volume, or density.
IMO, the loudest car would be a wall of horn loaded tweeters all constructively interfering at the same point (mic) at very high frequency. This would be really impossible to achieve though since the changes in pressure and vibrations would throw everything out of wack.
A hemispherical dome would be the best way to get the most woofers targeted at a single point. You would have to have quite a speaker though to take a 75hz square wave at full power without badly distorting and causing more harm than good. Would a square wave have a higher or lower maximum threshold? It seems to me it would be lower, but I have no idea. For the average guy though, big boxes tuned high are going to provide the best results. Take any subwoofer in winISD and use a vented box with a tuning frequency of 75hz and a volume of 5 cu. ft and you will see why. Then realize that the port length is so small you'd have to build an adamantium box(sorry, Xmen was on twice today!)
jt
Posts: 56 | From: atlanta | Registered: Nov 2000
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