its definately not measure at 1m... its actually further away than that
Most of the time the microphone is placed on the A pillar (the ones on the either side of the windshield). Depending on which class your in, the box can be as close as the B pillar (next on back from the A pillar) or in the boot.
Cabin gain plays a huge part in the final figure. My friends 800W rms system involing two 15's in a sealed box was measured at 137 dB.
Most of the high power systems use plain old vented boxs calculated in winISD. Some have tried bandpass but I havn't seen great results from them.
Hadn't someone already built a 120dB horn on this board using only 30w rms?
Most of the time the microphone is placed on the A pillar (the ones on the either side of the windshield). Depending on which class your in, the box can be as close as the B pillar (next on back from the A pillar) or in the boot.
Cabin gain plays a huge part in the final figure. My friends 800W rms system involing two 15's in a sealed box was measured at 137 dB.
Most of the high power systems use plain old vented boxs calculated in winISD. Some have tried bandpass but I havn't seen great results from them.
Hadn't someone already built a 120dB horn on this board using only 30w rms?
If you mean 130dB/1watt/1meter half-space anechoic, such an animal would be almost impossible to build. The maximum sensitivity achievable with current driver technology is about 116dB, and that with a perfect horn of very large dimensions. It would require 30 watts to achieve 130dB. Average horn sensitivities run about 10dB lower, which means the 130dB goal requires 300 watts.
Hey bill, what driver gets 116db @ 1w/1m?
It seems quite impossible to me for a woofer. The electrical to mechanical conversion would have to be near perfectly efficient. What would perfect efficiency be? I used to have this idea in my head that 120db @ 1w/1m was perfectly efficient, but it seems alot more complicated to me now that I actually know a bit about the physics of sound. I think it would probably vary alot for different speakers, especially high frequency ones, but how do manufatures even measure sensitivity. Its it done without a baffle, in an infinite baffle, in a sealed enclosure at some particular Q or a ported enclosure of some magic size tuned to some magic frequency....
It seems quite impossible to me for a woofer. The electrical to mechanical conversion would have to be near perfectly efficient. What would perfect efficiency be? I used to have this idea in my head that 120db @ 1w/1m was perfectly efficient, but it seems alot more complicated to me now that I actually know a bit about the physics of sound. I think it would probably vary alot for different speakers, especially high frequency ones, but how do manufatures even measure sensitivity. Its it done without a baffle, in an infinite baffle, in a sealed enclosure at some particular Q or a ported enclosure of some magic size tuned to some magic frequency....
With my 10$ driver and basshorn in a hatch i got 126db with 20watt RMS.
At 1cm distance I had 126db. At the dash i had ~126db also. Note that it was a ratshack meter which can only measure this much,and wouldve been working nonlinearly
TO the original thread starter-if your REALLY keen on a horn,its gona be HUGE,its not gona be a little 'horn port' or any silly thing that isnt actualy a horn.
many many cubic ft,how many can you fit?
Really theres no point in having a uselessly loud car,its fun having physical vibrations though-but cars are useless for sound quality,the output of the horn is so pure(stick your head near it) but the car buzzed real bad,and thats only at high 120db!
At 1cm distance I had 126db. At the dash i had ~126db also. Note that it was a ratshack meter which can only measure this much,and wouldve been working nonlinearly
TO the original thread starter-if your REALLY keen on a horn,its gona be HUGE,its not gona be a little 'horn port' or any silly thing that isnt actualy a horn.
many many cubic ft,how many can you fit?
Really theres no point in having a uselessly loud car,its fun having physical vibrations though-but cars are useless for sound quality,the output of the horn is so pure(stick your head near it) but the car buzzed real bad,and thats only at high 120db!
BassAwdyO said:
Increase the Q factor (decrease its coverage)
Make it really resonant
use it in a resonant space with lots of cabin gain(well sealed car)
100% efficiency is about 109db i think.. you can work it out with an equation i have in excel on my home PC.
However they choose to;-) normally on a baffle of specified size that hopefully is the same size as the other manufacturers use
😀
Check out the 'sensitivity guide' on eminence.com it talks about this in abit more detail-their methods.
A good manufacturer will state the details of their tests.
fr0st said:
126db+ if you trust the ratshack meter to give true results near its limit. It was 20w rms driver,with20w input,it DIDNT have a vented pole piece,and it had 3.5mm xmax
Yes thats me- I got rid of that annoying Name !
Am hornloading my jbl 2226 to 35hz soon
www.geocities.com/xobt
Cheers!
mike.e
I really dont think their is a single perfect sensitivity rating @ 1w/1m for every speaker, it depends. I think a better sensitivity test could be done using an accelerometer on the cone to measure cone motion and use that with cone area to calculate the efficiency. This would not apply for speakers in enclosures, but the efficency rating of speakers alone. I suppose that number typically becomes useless when you consider effects of power compression and the non linearities of the driver. Thats why I got XBL^2 🙂 I was wondering, you have a horn sub in your car, why if you took the time to design and build a horn did you use a $10 dollar driver and only 20 watts! How does it do with the windows open in the front of the car? I was thinking that might turn the entire car into a horn in some way.
no,there is, its 112db = 100% efficiency.
$$$$$$ I assure you,i wouldve used a tumult with 2kw if i couldve!
A horn has to be the prescribed shape in order to work properly,ie exponential,hyperbolic or conical. You can make a horn a car ,but not a car a horn
😀
$$$$$$ I assure you,i wouldve used a tumult with 2kw if i couldve!
Almost the same SPL ie so tiny i cant remember it- less than 3db
A car isnt a horn-it cant be,its a resonant chamber with its own tuning frequency determined by its volume and ports(holes)
A horn has to be the prescribed shape in order to work properly,ie exponential,hyperbolic or conical. You can make a horn a car ,but not a car a horn
😀
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None. That's not what he said. He said that a horn loaded speaker can get 116dB/watt and what limits it to that is the specs of the driver inside. Theoretically a 100% conversion from electric to acoustic watts will give about 119dB, the best horns are about 50% efficient so they can give about 116dB. My AutoTuba, one of Bills designs, gets on average 100dB/watt and uses the cabin gain in a car to get 90dB/watt at 20Hz. That's about 10dB more than you can get without horn loading.
When you open up the windows of your car it should have some significant effect on the horn's response. I would imagine it acts somewhat as a poorly designed horn due to the fact that the car's enterior will extend the horn's length to some degree (if the horn is at the back of the car and the windows are open in the front. You could probably calculate the response outside the car with the windows open if you modeled on hornresp the extended horn using the dimensions of the interior of the car...
You can get very good results with 4'th order bandpass, though the enclosures get very large, very quickly, the most recent one I did was with an Audiopipe 15'' (budget spl oriented sub) in a 250L enclosure (50L rear, 200L front) the "port" was a hole 150mm X 300mm (60hz tuning frequency)
Interestingly enough the "happy" frequency in the car is 47hz, but if I bring the tuning frequency of the enclosure down to that I actually loose 4db, interesting things going on in the car...
At a recent competition it got 145db with ~800w rms, compare that with the modeled spl of 127db and you have 18db of cabin gain
in theory with 25w it would get 130db
Interestingly enough the "happy" frequency in the car is 47hz, but if I bring the tuning frequency of the enclosure down to that I actually loose 4db, interesting things going on in the car...
At a recent competition it got 145db with ~800w rms, compare that with the modeled spl of 127db and you have 18db of cabin gain
in theory with 25w it would get 130db
i didnt measure outside extensively.
Your too optimistic - the interior of a car is NOT an expansion! its irregular,and if anything is more like a uselessly shaped box with holes in it.
Try it and find out
A car with the windows down is a lossy bandpass enclosure with a really high tuning frequency, this is also why they sound louder with a window down.
example;
The orange trace is a standard sealed enclosure (alpine type R 12'' in 45L)
Yellow trace is the above enclosure in a car (low frequency roll off not modeled)
red trace is what happens when you roll your window down(4th order bandpass, 45l rear, 800L+ front (cabin space) 500mm x 800mm hole (window opening)
You can also hear the high group delay from the bandpass effect when you wind down the window.
The orange trace is a standard sealed enclosure (alpine type R 12'' in 45L)
Yellow trace is the above enclosure in a car (low frequency roll off not modeled)
red trace is what happens when you roll your window down(4th order bandpass, 45l rear, 800L+ front (cabin space) 500mm x 800mm hole (window opening)
You can also hear the high group delay from the bandpass effect when you wind down the window.
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Volenti-now you should measure your outside response of the car to see how it matches to your simulation😎
as i can say from my experiences horn subs do not function very well above a certain amount of SPL in cars. the most is going back into the box i suggest.
best thing is to get the bass outout to a single point and then optimise the modes in the car that
you have a pressure mode on the mic position.
the longest way is most times the best for bass in general in cars i think.
for high spl apl i always use BR or bandpass and put the ports into corners. (shorten them a little due to fb going down) and then use woofers with very stiff cones and a lot of B.
be aware that you build a box into a box. cars volume is often not more the 4-8 times enclosure volume.
best thing is to get the bass outout to a single point and then optimise the modes in the car that
you have a pressure mode on the mic position.
the longest way is most times the best for bass in general in cars i think.
for high spl apl i always use BR or bandpass and put the ports into corners. (shorten them a little due to fb going down) and then use woofers with very stiff cones and a lot of B.
be aware that you build a box into a box. cars volume is often not more the 4-8 times enclosure volume.
To clarify, the interior of a car generally will not contribute to the expansion of a horn, barring one with well defined corners that the horn might fire into, such as a van. Calculating cabin gain is a fairly easy affair: measure the longest dimension in the vehicle, cabin gain at 12dB/octave begins where that dimension is a half-wavelength. Opening the window may make the bass sound subjectively louder but only since cabin gain is lost because of the lack of pressurization and the effective system f shifts higher to frequencies that the ear is more sensitive to (see: Fletcher-Munson curves).
mike.e said:
I'm currently in the process of getting exact measurements of cabin gain from various cars and the effect of different enclosure location/configuration within those cars.
Early data suggests that the typical 12db/oct rise from 50hz applied by many box programs is ******* hopeless, the cars with subs in the boot get +15db at 100hz! and +24db at 50hz! (compared to the same enclosure measured on a ground plane)
if anything a shelving response will proove to be more accurate but I'll have to wait untill I can test more (different) cars.
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