Usually PA woofs are high effciency, BUT when you take a look on freqency responce you see that if driver has 93 db/m eff. it will be only in mid 80 in the 40-50hz region...
I know that hi-fi woofs cant push bass throuhg the croud no matter how much power they have, I suppose that relates to efficiancy.
What to do ?
I think I should go horns. Big horns.
Disscuss
I know that hi-fi woofs cant push bass throuhg the croud no matter how much power they have, I suppose that relates to efficiancy.
What to do ?
I think I should go horns. Big horns.
Disscuss
VEC7OR said:
LABhorns.
http://www.prosoundweb.com/lsp/
An externally hosted image should be here but it was not working when we last tested it.
PA drivers don't play low on purpose--usually, in a dance situation, the room is very echoey, like a hall or stadium or cathedral, or rotunda. Anything below 40hz automatically sounds like mud. The rolloff there is to prevent things from sounding too loud.
You want people's hearts to beat in time with the music, you want their chests to rattle with every kickdrum. You don't want them to think to themselves, "by heisenberg's uncertainty principle, the bottom of that kickdrum leaves me wondering if I'm dancing out of time by +/- 20ms!"
You want people's hearts to beat in time with the music, you want their chests to rattle with every kickdrum. You don't want them to think to themselves, "by heisenberg's uncertainty principle, the bottom of that kickdrum leaves me wondering if I'm dancing out of time by +/- 20ms!"
Konnichiwa,
Actually, most measured responses for Pro Drivers are done under "infinite baffle" conditions, which means with no acoustic rear load. As most Pro Audio drivers have a low to very low Qt (for good reasons too) it means that the measured responses are showing a very low efficiency at low frequencies.
Now here you must realise that Pro Drivers are often operated at VERY HIGH power levels. Such levels raise the Voice Coil Temperature easily up to a few 100 degrees. This means their voice coil resistance will increase and thus the Drivers Qe will rise increasing the Qt and reducing the output in the midrange and boosting the LF output.
Further, the Driver will be placed into an enclosure (these days usually vented or bandpass) which will increase the system Q further. So while the system may SEEM on paper unusable, when actually operated at high SPL things even out notably.
It is not just efficency. Lets take a well known LF System, the EV MTL1x.
EV MTL1X Datasheet
This uses a pair of EV 18" Pro woofers, the EVX180B. The datasheet for this woofer is here:
EVX180B
Nominal sensitivity of the Driver is 98db/W/m (note that this WATT/m NOT 2.83V/m!!!). Two produce the 101db/W/m EV cliams for the MTL1X.
The MTL1X datasheet illustrates a response for ONE unit that is 95db/W/m @ 50Hz and 105db/W/m @ 200Hz. Now, if you operate the driver near rated thermal power (600W RMS which may be composed out of short term peaks up 2400W but a THERMAL averaged power of no more than 600W) the Voicecoil will heat up and the 105db/W/m @ 200Hz will reduce and the 50Hz bottom end will come up slightly, somewhat flattening out the response.
At rated thermal Power I'd expect at least 3 - 4db thermal compression, so the 101db rated sensitivity drops to maybe 97-98db/W/m sensitivity with the LF boosted slightly due to higher and also some db taken off - looks basically flat as a result with 50Hz maybe at 95db/W/m when the speaker is at operating temperature.
So, with that in mind and 4800W equivalent Peaks applied the LF system will produce peaks 37db higher than the 1W/1m figure, or short terms peaks of > 130db/1m @ 50Hz.
If you can handle the Transportation issues etc, sure. One of the best Sound Reinforcement Systems I used on Touring was based around a bunch of Community RS880 (sadly long gone) a passive 3-Way Top unit featuring a pair of massive 15" front hornloaded woofers, a 4" Throat (8" Diaphragm) Midrange Compression Driver and special Piezo Tweeters. The speakers where quite compact and clearly limited in LF output but above 120Hz or so they managed 108db/W/m sensitivity, very low compression and 800W RMS rating. As subwoofers BTW we used the Servodrive BassTech 7's and a few Community 4 X 10" 'subwoofer' as midbass fill in.
In terms of output capability these things where as loud and louder in operation as twice to trice the amount of Drivers in the conventional systems from EV or JBL at the time. We where able to get away with 4-6 Bass Tech 7's per side and 3 - 4 RS880 per side in even fairly substantial venues and smaller open air gigs. The kind of walls of MTL4 or JBL concert systems we would have had to stack to match the kind of sound and output we where getting would have been a sight indeed.
They key to getting these failry sills SPL's in a compact package where specially designed, very high performance drivers mated to intelligent enclosures.
These days I would look VERY HARD at Tom Danleys "Unity" Horns as compact, high SPL upper bass and onwards system and his Labhorn(s) as the matching woofers.
A Unity with a 2" compression driver, 4 X 5" Cone midrange and 8 X 6.5"- 8" upper bass driver can fit into a 24" Cube and produce serious SPL's above 100Hz. The Labhorn with a few stacked per side should go low and VERY loud, all this is DIY'able.
BTW, Tom D designed the Bass Tech 7's we where using back then, I still think them among the most awesome LF systems I ever worked with.
As for many of the very large classic horn designs (Shearer, W-Bin etc) they usually do not offer as much efficiency as the more modern heavily optimised designs such as the Labhorn and Unity but usually use fewer and cheaper drivers, so if size is NOT much of an issue I think these can work well.
One of the better "classic" style systems I worked with used Turbosound 10" Midrange Horn copies with EVM10M-PL (2 per upper range cabinet), 2" throat compression Drivers (usually JBL) on JBL copy 40X60 Degree Horns and a bunch of Bullet Tweeters (usually Celestion HF100 but also others that where more or less compatible).
We tended to stack these upper range cabs in sets of 4 so that the tweeter arrays where closest together. LF Stack was based around 18" W-Bins with EVM18B-PL. Usually it was at least 6 - 8 18" W Bins to a 4-Pack of upper range cabinets.
Sayonara
VEC7OR said:
Actually, most measured responses for Pro Drivers are done under "infinite baffle" conditions, which means with no acoustic rear load. As most Pro Audio drivers have a low to very low Qt (for good reasons too) it means that the measured responses are showing a very low efficiency at low frequencies.
Now here you must realise that Pro Drivers are often operated at VERY HIGH power levels. Such levels raise the Voice Coil Temperature easily up to a few 100 degrees. This means their voice coil resistance will increase and thus the Drivers Qe will rise increasing the Qt and reducing the output in the midrange and boosting the LF output.
Further, the Driver will be placed into an enclosure (these days usually vented or bandpass) which will increase the system Q further. So while the system may SEEM on paper unusable, when actually operated at high SPL things even out notably.
VEC7OR said:
It is not just efficency. Lets take a well known LF System, the EV MTL1x.
EV MTL1X Datasheet
This uses a pair of EV 18" Pro woofers, the EVX180B. The datasheet for this woofer is here:
EVX180B
Nominal sensitivity of the Driver is 98db/W/m (note that this WATT/m NOT 2.83V/m!!!). Two produce the 101db/W/m EV cliams for the MTL1X.
The MTL1X datasheet illustrates a response for ONE unit that is 95db/W/m @ 50Hz and 105db/W/m @ 200Hz. Now, if you operate the driver near rated thermal power (600W RMS which may be composed out of short term peaks up 2400W but a THERMAL averaged power of no more than 600W) the Voicecoil will heat up and the 105db/W/m @ 200Hz will reduce and the 50Hz bottom end will come up slightly, somewhat flattening out the response.
At rated thermal Power I'd expect at least 3 - 4db thermal compression, so the 101db rated sensitivity drops to maybe 97-98db/W/m sensitivity with the LF boosted slightly due to higher and also some db taken off - looks basically flat as a result with 50Hz maybe at 95db/W/m when the speaker is at operating temperature.
So, with that in mind and 4800W equivalent Peaks applied the LF system will produce peaks 37db higher than the 1W/1m figure, or short terms peaks of > 130db/1m @ 50Hz.
VEC7OR said:
If you can handle the Transportation issues etc, sure. One of the best Sound Reinforcement Systems I used on Touring was based around a bunch of Community RS880 (sadly long gone) a passive 3-Way Top unit featuring a pair of massive 15" front hornloaded woofers, a 4" Throat (8" Diaphragm) Midrange Compression Driver and special Piezo Tweeters. The speakers where quite compact and clearly limited in LF output but above 120Hz or so they managed 108db/W/m sensitivity, very low compression and 800W RMS rating. As subwoofers BTW we used the Servodrive BassTech 7's and a few Community 4 X 10" 'subwoofer' as midbass fill in.
In terms of output capability these things where as loud and louder in operation as twice to trice the amount of Drivers in the conventional systems from EV or JBL at the time. We where able to get away with 4-6 Bass Tech 7's per side and 3 - 4 RS880 per side in even fairly substantial venues and smaller open air gigs. The kind of walls of MTL4 or JBL concert systems we would have had to stack to match the kind of sound and output we where getting would have been a sight indeed.
They key to getting these failry sills SPL's in a compact package where specially designed, very high performance drivers mated to intelligent enclosures.
These days I would look VERY HARD at Tom Danleys "Unity" Horns as compact, high SPL upper bass and onwards system and his Labhorn(s) as the matching woofers.
A Unity with a 2" compression driver, 4 X 5" Cone midrange and 8 X 6.5"- 8" upper bass driver can fit into a 24" Cube and produce serious SPL's above 100Hz. The Labhorn with a few stacked per side should go low and VERY loud, all this is DIY'able.
BTW, Tom D designed the Bass Tech 7's we where using back then, I still think them among the most awesome LF systems I ever worked with.
As for many of the very large classic horn designs (Shearer, W-Bin etc) they usually do not offer as much efficiency as the more modern heavily optimised designs such as the Labhorn and Unity but usually use fewer and cheaper drivers, so if size is NOT much of an issue I think these can work well.
One of the better "classic" style systems I worked with used Turbosound 10" Midrange Horn copies with EVM10M-PL (2 per upper range cabinet), 2" throat compression Drivers (usually JBL) on JBL copy 40X60 Degree Horns and a bunch of Bullet Tweeters (usually Celestion HF100 but also others that where more or less compatible).
We tended to stack these upper range cabs in sets of 4 so that the tweeter arrays where closest together. LF Stack was based around 18" W-Bins with EVM18B-PL. Usually it was at least 6 - 8 18" W Bins to a 4-Pack of upper range cabinets.
Sayonara
Wow, nice post there. Just to add a thought, if you diy a unity horn, you would probably want to stick with a 1" compression driver - the spacing of the mids and the CD usually won't allow for a 2" throat, and as you're usually looking at a 1.2-1.6khz crossover from the midranges to the CD, you don't really need the extra volume displacment of the 2" and the extra HF extension of the 1" could be an advantage. However, another interesting way to go with a 2" CD could be one of the BMS coaxial drivers and then 2 or 4 10" or 12" woofers loaded in further down the horn.
John
John
Re: Re: What shoul I use if I want low bass at high SPL (PA audio disscussion)
You seem very knowledgeable about PA drivers, enclosures etc I tryed to explore audio in all aspects (home, PA and car) and for my PA system that I run in the house. I have a modest setup (2 EV Eliminator tops, 2 SB180 subs [with the aforementioned evx-180B drivers] tops driven by an AB international amp, the bottom end with a Crown Macro tech 5000vz amp) - but way more then enough power for a "residential" setup.
The 18" PA woofers, while on paper dont look like they play very low they can play very low in person. They dont use a conventional ported design (I was gonna buy a JBL SRX4719x double 18" but then realized that I'd probbly rather have 2 single 18 bins then 1 double 18 bin for the sake of moving, placement flexability), they're the EV "subscoop" design. For those who dont know the woofer is reverse mounted at an angle in the enclosure, which is also slot loaded, which is supposed to be a quasi horn loaded/vented design. It seems like a very deilicate design, as if one little thing is wrong it'll start cancelling. I also notice with this design that theres a significant rise in output above 100 hz or so. This is great for the chest kicking sensation and punchiness and the (cutting through the crowd), but set the crossover too high and you get alot of muddiness.
But no thanks to car audio, it seems even my 2 18s with 1200 or so watts behind each one, Im still expecting more bass out of the system. A local night club I frequent uses parts of a MTL4 manifold tech system. I'd love to have just a pair of bass packs and a high packs as well as a labhorn and servo drive to play around with, that seems like a serious system.
You seem very knowledgeable about PA drivers, enclosures etc I tryed to explore audio in all aspects (home, PA and car) and for my PA system that I run in the house. I have a modest setup (2 EV Eliminator tops, 2 SB180 subs [with the aforementioned evx-180B drivers] tops driven by an AB international amp, the bottom end with a Crown Macro tech 5000vz amp) - but way more then enough power for a "residential" setup.
The 18" PA woofers, while on paper dont look like they play very low they can play very low in person. They dont use a conventional ported design (I was gonna buy a JBL SRX4719x double 18" but then realized that I'd probbly rather have 2 single 18 bins then 1 double 18 bin for the sake of moving, placement flexability), they're the EV "subscoop" design. For those who dont know the woofer is reverse mounted at an angle in the enclosure, which is also slot loaded, which is supposed to be a quasi horn loaded/vented design. It seems like a very deilicate design, as if one little thing is wrong it'll start cancelling. I also notice with this design that theres a significant rise in output above 100 hz or so. This is great for the chest kicking sensation and punchiness and the (cutting through the crowd), but set the crossover too high and you get alot of muddiness.
But no thanks to car audio, it seems even my 2 18s with 1200 or so watts behind each one, Im still expecting more bass out of the system. A local night club I frequent uses parts of a MTL4 manifold tech system. I'd love to have just a pair of bass packs and a high packs as well as a labhorn and servo drive to play around with, that seems like a serious system.
Kuei Yang Wang said:
eric=
so its kinda a waveguide -it reminds me of the altec short horns (like 50cm long) and also the Decware strange X shaped box..
2 Active 15"
2 Passive 18"
http://www.servodrive.com/contrabass.html
-3db at 15hz =
so its kinda a waveguide -it reminds me of the altec short horns (like 50cm long) and also the Decware strange X shaped box..
2 Active 15"
2 Passive 18"
http://www.servodrive.com/contrabass.html
-3db at 15hz =
Hi Brett,
I would start by reading the patent. I have a link to it on my webpage. It gives some general guide lines but doesn't really go into a lot of details. Beyond that, you can either cut and try and plan on using eq or write a simulator for it to do design work with. I've done both, and the eq'd versions can sound good provided nothing too extreme is required to get flat response. Of course it's nice to just have flat response to start with.
John
I would start by reading the patent. I have a link to it on my webpage. It gives some general guide lines but doesn't really go into a lot of details. Beyond that, you can either cut and try and plan on using eq or write a simulator for it to do design work with. I've done both, and the eq'd versions can sound good provided nothing too extreme is required to get flat response. Of course it's nice to just have flat response to start with.
John
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