The best sounding HF driver you have ever met |
Post Reply | Page <1 23456 8> |
Author | |
Teunos
Old Croc Joined: 23 November 2008 Location: The Netherlands Status: Offline Points: 1799 |
Post Options
Thanks(0)
|
4w/cm^2 is a lot of noise. Actually you would be deaf at 166db of noise
|
|
Best regards,
Teun. |
|
Ray666
Registered User Joined: 12 July 2005 Location: Estonia Status: Offline Points: 81 |
Post Options
Thanks(0)
|
Beyma is good, but there is no way to line these. they will sum up only up to 7 khz. Then single cab all the way - x @ 1.1 khz beyma in the middle and two pd 122-s on the side. thanks for helping out. |
|
Steve_B
Old Croc Joined: 29 September 2007 Status: Offline Points: 1587 |
Post Options
Thanks(0)
|
Some rough calculations. I’ll assume a flat surface area rather
than spherical cap that the sound is radiating into. The area of a 1” compression driver throat is: Πr2 --- π x 0.01272 = 0.0005 m2 The actual area of the openings in the phase plug could be
less. Say the driver is fitted to a round 60˚ horn. At 1m out (from the throat) the radius of the cone is Tan30
=0.577 So the area is π x 0.5772 = 1.04 m2 That is a difference of 1.04/0.0005 = 2094. According to this thread, some 1” compression drivers are
capable of keeping up with three 12” drive units. Winisd calculates three 12”
PD drivers (mentioned in the first post) will produce 132dB @ 1 m. 132dB-sil works out at 16W/m2 divide by 10,000 to
get to W/cm2 then multiply by 2094 to calculate the intensity at
throat and it comes out at about 3.5 W/cm2 Some manufacturers are claiming up to 140dB peak levels
which means the intensity at the throat is 20W/cm2. The graph on page 276
of Acoustics by Beranek, which shows the amount of 2nd harmonic
distortion for a given power density and frequency relative to cut off, tops
out at 10W/cm2 even at that level, using the same frequencies I used
previously gives 40% 2nd harmonic distortion. |
|
Tony Wilkes
Old Croc Joined: 02 August 2004 Location: West Midlands Status: Offline Points: 4840 |
Post Options
Thanks(0)
|
The only thing that I will add is that the audibility of 2nd Harmonic Distortion in Compression Drivers has been under discussion for a while now and I suspect that IM distortion is the real culprit in bad sounding drivers.
Tony |
|
www.forteaudio.eu - BMS - db-Mark Processors - Lexon (SAE)
|
|
Steve_B
Old Croc Joined: 29 September 2007 Status: Offline Points: 1587 |
Post Options
Thanks(0)
|
Tony, I'm not actually on about the driver. This is distortion produced by the non linear compression of the air in the horn. The more rapidly the horn flares out the less distortion there is, hence the ratio of frequency to cutoff frequency. Conical flares will have less distortion while hyperbolic horns will have more.
By default the exit of the driver is an extension of the horn, but to a large extent the make of the drive unit is irrelevant. Whether it is BMS, JBL, etc, etc the sound wave is still being squeezed through a small hole. I brought a similar topic up years ago on a well known pro-sound forum, but ended up getting harassed because I disagreed with the then designer of a large loudspeaker manufacturer. Basically he said the problem was one for drive unit manufacturers rather than cabinet designers. I felt he was being pedantic. As materials and drive units improve I think that we are running into the physical limitations of what the air can do. One advantage of line arrays is that the ratio of cones to compression drivers has reversed, so the power density at the throat is reduced. I know that many here try and wring the last upper KHz out of their systems which means using 1" drivers, but a 2" offers four times the throat area which means lower power densities. I'd be very interested to hear what some of the compression driver designers think about this topic.
|
|
snafu
Registered User Joined: 17 November 2008 Location: wales uk Status: Offline Points: 352 |
Post Options
Thanks(0)
|
A 2" comp taking it easy sounds better than a 1" being driven hard, you get a lot of sound for your money.
And when the going gets heavy you can always turn a 2" up.
About 10 years ago when looking for hf drivers for my concert system I investigated the stage accompany ribbon drivers, I was very impressed but at a grand apiece they were out of my reach. They gave pro sound output flat from 500hz to 20khz. |
|
Tony Wilkes
Old Croc Joined: 02 August 2004 Location: West Midlands Status: Offline Points: 4840 |
Post Options
Thanks(0)
|
@ Steve_B Sorry mate mis-read you :)
Tony |
|
www.forteaudio.eu - BMS - db-Mark Processors - Lexon (SAE)
|
|
Marko
Registered User Joined: 28 January 2009 Location: Croatia Status: Offline Points: 274 |
Post Options
Thanks(0)
|
well, I have totally different experience
after reading, mostly on this forum, how good bms drivers are I decided to give them a go and buy 2 x 4544 for a 12"+1" box. Horn was B&C ME 20 and I wanted to cross them at 2K but there was a lot of distortion in sound below 4K. That was with active 4th order high pass filter and with passive 2nd order the situation was a lot worse. Then I got the RCF HF 101 horns, which are bigger, and better load the driver at lower freq. but with them I lost a little bit of top end, gain a lot of pattern control but distortion below 3,5K - 4K was still there. Then I got Faital pro HF 140 with horns from Martin F 15 cabs (1,4") and when crossed at 2K 4th order they sound good. But lower than 2K not anymore. So, what I doing wrong? Which horns you guys recomend with 4544? I even start to doubt that my BMS comps are original since I read somewhere that there are some copies from China are around. |
|
MarjanM
Old Croc Joined: 10 February 2005 Location: Macedonia Status: Offline Points: 7810 |
Post Options
Thanks(0)
|
Marko, BMS drivers have a big bump at 3-4Khz in its frequency response and you need to have a very good passive crossover to tame that bump. Once they get flat they sound extremely good even down to 800Hz.
|
|
Marjan Milosevic
MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
|
TENSiON
Registered User Joined: 02 September 2012 Status: Offline Points: 279 |
Post Options
Thanks(0)
|
4W/cm2 for a 1" exit comp on a 60/40 horn equates to about 133dB@1m. Anyone expecting or running their 1" comps at such levels does well deserve all the distortion they can get
On another note, 3rd harmonic distortion is a lot more defining in terms of how good (or bad) it will sound, as the 2nd is less perceivable due to being more "harmonic". |
|
_djk_
Old Croc Joined: 23 November 2004 Location: United States Status: Offline Points: 6002 |
Post Options
Thanks(0)
|
The size of the driver exit is not the throat of the driver.
The throat of the driver is the slots in the phase plug. Most drivers have a 10:1 ratio between the diaphragm area and the area of the slots in the phase plug. |
|
djk
|
|
thepersonunknown
Old Croc Joined: 25 November 2009 Location: Madrid Status: Offline Points: 1628 |
Post Options
Thanks(0)
|
sorry to bring this up again, but what do we think of using some of the newer 'linearay' waveguides in a pointsource box.
my idea is to use two comps to keep up to a particularily loud midrange horn in the upper high range 4k+, but withought thrashing the hell out of a single driver, and coupling as best a posible, much like a line array cab, but using just 2 waveguides mated to a flare which allows around 90horizontal by 30 vertical (20down 10up) dispersion. |
|
They keep telling me life is short, but its the longest thing ive ever done!!!
|
|
Post Reply | Page <1 23456 8> |
Tweet |
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |