You're hung up on the crossover. He's referring to the loudspeaker.Well that's Not passive, it's Active ! People reading what BertlSound wrote, who don't know, might be misled. So best to point it out
It's an established convention that loudspeaker cabinets that have no built-in amplification are called passive, and those that do are called active. This is regardless of the crossover used. One will have a Speakon jack in the back, the other will have power and xlr. An active loudspeaker can use a passive crossover, and a passive loudspeaker can use an active crossover.
Contextually, given that he was discussing his choice to attach a Pascal plate amp (active) vs his friend's choice to use an Powersoft rackmount unit (passive), the reference was to amplification and not crossover.
hi !
here's a measurement taken outside of two 18sw115 loaded th18s, feel free to comment and criticize! no spl calibration.
subs with kicks on top stacked vertical on concrete with 100 cm of concrete in front then the lawn and the mic is some 5 meters in front on axis at 170 cm height, on grass.
nearest buildings are 10 meters on the back of the stack, the other buildings are at least 15 -20 meters away; also 5 trees some ten meters away but i think they are to small to impact sub 100HZ wavelenghts.
mic is an Xref, looks like a behringer mic but is sold with individual calibration file and measurement.
measurements varying position seemed pretty consistent.
that's how we use them lately, no eq at all, a bw24 at 28hz and a lr24 at 80hz that flattens the high frequency bump and brings the acoustical crossover at 90hz.
looks pretty flat and beautiful to me! no smoothing applied.
soooo if i was marketing theese i should say +3/-3 31-100hz
in reality i look at it as -3 between 36 and 37 hz BUT from 31 to 35 hz it stays flat at -4,5/5 and -6 is at 30.5hz.
indoor in a 10x10 meters room it goes wild, in some positions the max peak is at 34 and -3 from that at 32...
i've got another two 18sw115-4 coming this week, planning on another two th18 for the warm season, and wondering this:
when doing events with music with strong 30hz could i eq it +3dbs from 32 (not influencing freqs under 30) and just limit the system lower?
doing some pessimistic math (hopefully right) starting from an hipotetic 99db average sensitivity - i gather this from the thread, please correct me on this - adding 12 dbs for 4 speakers stacked and 29 db gain from 1700 watts (32-3 power compression) gives me 140 db at 1meters at rms power.
i could feed the drivers with 600 watt providing 99db+12+26(with 1,5 power compression) to get 137 db max and the same stress to the drivers, right?
so i could choose between a configuration for max power, even rising the hi pass to 35 for safety, and an almost flat to 30 configuration with just 3 db less when really needed.
almost set on building another two of theese, but got this little itch about the bigger 30hz version, maybe this eq trick could be the solution, i really don't need flat to 30 and bigger boxes but you know... don't make me look at the othorn again
here's a measurement taken outside of two 18sw115 loaded th18s, feel free to comment and criticize! no spl calibration.
subs with kicks on top stacked vertical on concrete with 100 cm of concrete in front then the lawn and the mic is some 5 meters in front on axis at 170 cm height, on grass.
nearest buildings are 10 meters on the back of the stack, the other buildings are at least 15 -20 meters away; also 5 trees some ten meters away but i think they are to small to impact sub 100HZ wavelenghts.
mic is an Xref, looks like a behringer mic but is sold with individual calibration file and measurement.
measurements varying position seemed pretty consistent.
that's how we use them lately, no eq at all, a bw24 at 28hz and a lr24 at 80hz that flattens the high frequency bump and brings the acoustical crossover at 90hz.
looks pretty flat and beautiful to me! no smoothing applied.
soooo if i was marketing theese i should say +3/-3 31-100hz
in reality i look at it as -3 between 36 and 37 hz BUT from 31 to 35 hz it stays flat at -4,5/5 and -6 is at 30.5hz.
indoor in a 10x10 meters room it goes wild, in some positions the max peak is at 34 and -3 from that at 32...
i've got another two 18sw115-4 coming this week, planning on another two th18 for the warm season, and wondering this:
when doing events with music with strong 30hz could i eq it +3dbs from 32 (not influencing freqs under 30) and just limit the system lower?
doing some pessimistic math (hopefully right) starting from an hipotetic 99db average sensitivity - i gather this from the thread, please correct me on this - adding 12 dbs for 4 speakers stacked and 29 db gain from 1700 watts (32-3 power compression) gives me 140 db at 1meters at rms power.
i could feed the drivers with 600 watt providing 99db+12+26(with 1,5 power compression) to get 137 db max and the same stress to the drivers, right?
so i could choose between a configuration for max power, even rising the hi pass to 35 for safety, and an almost flat to 30 configuration with just 3 db less when really needed.
almost set on building another two of theese, but got this little itch about the bigger 30hz version, maybe this eq trick could be the solution, i really don't need flat to 30 and bigger boxes but you know... don't make me look at the othorn again
Attachments
On US prosound forums, I'm noticing more and more that people are using the primary terms passive versus powered (or sometimes self-powered)......knowing that powered can be secondarily either passive or active.
The 28hz BW24db looks to be about right in theory maybe 29hz?
I make x-max to be an uncompressed 102 volts (1300w into 8 ohms) in a hornresp sim and efficiency of at least 100db for 2.83volts at the 58Hz dip, and 142.6db for 4 speakers at x-max at 40hz
Then again we know the B&C 18SW115 is capable of a lot more excursion than x-max!
Regards Xoc1
I make x-max to be an uncompressed 102 volts (1300w into 8 ohms) in a hornresp sim and efficiency of at least 100db for 2.83volts at the 58Hz dip, and 142.6db for 4 speakers at x-max at 40hz
Then again we know the B&C 18SW115 is capable of a lot more excursion than x-max!
Regards Xoc1
Attachments
I can share my latest experience regarding these subs. It is very important to be able to change the limitter settings based on the type of music you are putting though them. I use mine with a clone, for now each on a channel. At peak power I can give them 3300 watts and I didn't have issues with them like this with music with high enough crest factor. HPF at 27 hz But 24 and LPF depending on tops. No eq . On long term limit I use 0.5-1.5 sec attack and 4 seconds release 4:1 ratio and that's it.
But last weekend I put them on techno music and I had the voice coil heated so much it started to really smell. So I had to go down with the gain about 2-3 dB and I was wondering why it never happened before, even on heavy dubstep with very long notes. Then I realized that first, on this kind of music, most of the basa content is focused between 45 and 85 hz. There the sub is the least efficient and the impedance is very low so the total amount of heat is very high.
Second, the short powerful beats were long with overtones but not long enough to trigger the limiters so the amp was feeding the drivers at full power . Before this I used a Powersoft amp which had the trupower limiter that measured the effective power remained in the coil and it would limit it when necessary.
So an important fact when using them on dubstep music is that if notes are focused at 25-45 hz it's all safe but if the content is focused in the next band one has to be careful not to blow things up.
But last weekend I put them on techno music and I had the voice coil heated so much it started to really smell. So I had to go down with the gain about 2-3 dB and I was wondering why it never happened before, even on heavy dubstep with very long notes. Then I realized that first, on this kind of music, most of the basa content is focused between 45 and 85 hz. There the sub is the least efficient and the impedance is very low so the total amount of heat is very high.
Second, the short powerful beats were long with overtones but not long enough to trigger the limiters so the amp was feeding the drivers at full power . Before this I used a Powersoft amp which had the trupower limiter that measured the effective power remained in the coil and it would limit it when necessary.
So an important fact when using them on dubstep music is that if notes are focused at 25-45 hz it's all safe but if the content is focused in the next band one has to be careful not to blow things up.
I've had my 2x 18sw115 in my keystones smell funny on two occasions, playing very demanding techno through them without limiter engaged(when just finished to see how capable they were). Now I limit them at 87 volts(8 ohm models). 30-106 BW24
What I learned from the guys at b&c is that as long as you keep the magnet below 100°c long-term, you are safe(applicable to the th18 aswell) Good thing with tapped horn with access to magnet
My ir thermometer has not been reliable but my guess is my magnets are about 70-80°c using these settings
What I learned from the guys at b&c is that as long as you keep the magnet below 100°c long-term, you are safe(applicable to the th18 aswell) Good thing with tapped horn with access to magnet
My ir thermometer has not been reliable but my guess is my magnets are about 70-80°c using these settings
hi !
here's a measurement taken outside of two 18sw115 loaded th18s, feel free to comment and criticize! no spl calibration.
subs with kicks on top stacked vertical on concrete with 100 cm of concrete in front then the lawn and the mic is some 5 meters in front on axis at 170 cm height, on grass.
nearest buildings are 10 meters on the back of the stack, the other buildings are at least 15 -20 meters away; also 5 trees some ten meters away but i think they are to small to impact sub 100HZ wavelenghts.
mic is an Xref, looks like a behringer mic but is sold with individual calibration file and measurement.
measurements varying position seemed pretty consistent.
that's how we use them lately, no eq at all, a bw24 at 28hz and a lr24 at 80hz that flattens the high frequency bump and brings the acoustical crossover at 90hz.
looks pretty flat and beautiful to me! no smoothing applied.
soooo if i was marketing theese i should say +3/-3 31-100hz
in reality i look at it as -3 between 36 and 37 hz BUT from 31 to 35 hz it stays flat at -4,5/5 and -6 is at 30.5hz.
indoor in a 10x10 meters room it goes wild, in some positions the max peak is at 34 and -3 from that at 32...
i've got another two 18sw115-4 coming this week, planning on another two th18 for the warm season, and wondering this:
when doing events with music with strong 30hz could i eq it +3dbs from 32 (not influencing freqs under 30) and just limit the system lower?
doing some pessimistic math (hopefully right) starting from an hipotetic 99db average sensitivity - i gather this from the thread, please correct me on this - adding 12 dbs for 4 speakers stacked and 29 db gain from 1700 watts (32-3 power compression) gives me 140 db at 1meters at rms power.
i could feed the drivers with 600 watt providing 99db+12+26(with 1,5 power compression) to get 137 db max and the same stress to the drivers, right?
so i could choose between a configuration for max power, even rising the hi pass to 35 for safety, and an almost flat to 30 configuration with just 3 db less when really needed.
almost set on building another two of theese, but got this little itch about the bigger 30hz version, maybe this eq trick could be the solution, i really don't need flat to 30 and bigger boxes but you know... don't make me look at the othorn again
Cone excursion below fb is a good way to save your drivers. If you rise the x-over to closer to fb and a bassline comes along at fb without the venting from lower-than-fb excursion you could possibly fry the drivers
Personally I would not try to get much 30 hz from my keystones(tho the th18 seem to have more shallow tilt), it will come at too much of an expense due to the system not being designed for it. Yes it's present but not much compared to 40 hz
Many speakers will smell at very modest temperatures when you're first breaking them in and then stop when the residual volatiles have outgassed. I've had a lot of speakers (especially Eminence) smell pretty good with the magnets just over room temp on their first few running hours - and after that it takes an overload to do it. 70 or 80C will burn your hand if you touch it. Never had a big B&C that hot, even at SPLs that make well broken in Eminence stink up a storm.
Thanks for the enlightenment on smelly drivers, I felt like a serial killer when they started to smell but it has not happened since!
I might def. be wrong in my approximation. It does not burn my hand at all but it's considerably warm so probably cooler than the 70-80 in that case.
For what it's worth, they way I've always thought about it is that the kind of smells the voice coil gives off occur whenever the coil get heated to a temperature it hasn't yet been at before. I imagine the various volatiles used in the glues have different temperatures at which they start to off-gas. So, even if you get the driver a bit toasty (but within its designed operating range) you'll get a bit of smell, but the subsequent times you reach the same temperatures you'll get less or no smell.
Just a hypothesis of mine. Point being that a funky smell could be a normal part of "breaking in" the coil, even at safe temperatures.
Just a hypothesis of mine. Point being that a funky smell could be a normal part of "breaking in" the coil, even at safe temperatures.
Since nobody mentioned... AFAIK the voice coil is (also) cooled a great deal by air moving past it as the cone&coil move; just feel the (hot) air coming out of the back side vent hole(s). If you're playing 45-85 Hz cone excursion will be (a lot) less than if you're playing 30-50 Hz (assuming you apply the same power), hence less cooling... This could also have played a role I think.
Yes, there are two types of cooling important - colling through convection (air flow) and radiation. Radiation is dependant on the types of materials used, the surface, the colour etc... (look up Stephan Boltzmann, Black body and related topics in wikipedia). Convection Colling also is dependat on the surface amount and of course the amount of air moved around (and swapped) and delta T (difference of temperature of the air heated and the air cooling) give the "cooling capacity"..
In some motors, the air is only pushed from one side to the other, there is not much exchange with the cooler air. Others are optimized so the hot air really is swapped to a great amount with cooler air from the surrounding. In a very small closed back chamber of a Front loaded horn, the air in the back chamber heats up quite a bit - so delta T is small. Look up Pi Horns with LAB 12 drivers with a coller heat pipe attached to a aluminium plate to see effects on this.
In a Tapped horn with the driver mounted near the mouth, having the magnet "in free air", there is a way better chance of "fresh air" getting near the motor.
This exchange of air is dependand on the translation of hot air flowing upwards (heat up a romm, measure temp - it´s always warmer on the cealing than the floor, except you mix up the air with a fan a lot, so temp. is distributed eavenly)... And the other factor is the air being pushed out if the motor by the movement. So cone excursion is important. If EQ or HP Settings are too conservative, the cone moves not enough to rellay exchange air. At resonance points, excursion is very small and this is the point Thijs is talking about.. Some posts ago, someone pointed out a technique where he simulates excusrion within hornresp and checks, if the HP Filter is set the way that excursion around the resonance point is the same above and below the Resonance...
I´ve seen drivers blown to smoke which should be able to handle kW of power and others having no problem, despite being much less capable - most of the times, the circumstances above contributed quite a bit to the failure-cause.
Hope my rusty english was understandable, I am happy if you leave comments or point out mistakes in my language
In some motors, the air is only pushed from one side to the other, there is not much exchange with the cooler air. Others are optimized so the hot air really is swapped to a great amount with cooler air from the surrounding. In a very small closed back chamber of a Front loaded horn, the air in the back chamber heats up quite a bit - so delta T is small. Look up Pi Horns with LAB 12 drivers with a coller heat pipe attached to a aluminium plate to see effects on this.
In a Tapped horn with the driver mounted near the mouth, having the magnet "in free air", there is a way better chance of "fresh air" getting near the motor.
This exchange of air is dependand on the translation of hot air flowing upwards (heat up a romm, measure temp - it´s always warmer on the cealing than the floor, except you mix up the air with a fan a lot, so temp. is distributed eavenly)... And the other factor is the air being pushed out if the motor by the movement. So cone excursion is important. If EQ or HP Settings are too conservative, the cone moves not enough to rellay exchange air. At resonance points, excursion is very small and this is the point Thijs is talking about.. Some posts ago, someone pointed out a technique where he simulates excusrion within hornresp and checks, if the HP Filter is set the way that excursion around the resonance point is the same above and below the Resonance...
I´ve seen drivers blown to smoke which should be able to handle kW of power and others having no problem, despite being much less capable - most of the times, the circumstances above contributed quite a bit to the failure-cause.
Hope my rusty english was understandable, I am happy if you leave comments or point out mistakes in my language
You are absolutely right, black (or dark colored) materials absorb and emit more electromagnetic radiation then 'white' objects but do not add much more heat (1%) to the total. Interesting read on Stefan Boltzmann and the Kirchhoff's Radiation Law.
Watch it, somebody will ban you for racist remarks if you keep this up ;^).
This is slightly off topic since for a loudspeaker driver the convective and conductive cooling is by far the biggest contributor, but what's interesting is that for a lot of situations the way the surface radiates energy (emissivity) is very important as well.
The common wisdom that black surfaces get hot in the sun is true to a certain extent because black surfaces tend to reflect little energy, but the interesting thing is that they tend to be also good at radiating energy.
A polished chrome surface (like, for example, the buckle on your car's seatbelt) reflects quite a bit of energy, but it's often even worse at re-radiating it. Given enough time it can reach equilibrium at an even higher temperature. That's why on a hot summer day those metal surfaces can sometimes get hot enough to give burns (that and they're good at conducting that energy right into your skin).
One cool thing that is being worked on is materials that are specialized to be highly reflective of radiant energy AND with very high emissivity in the specific IR bands that the atmosphere is largely transparent to. The result is a thermal barrier of sorts that keeps heat out and also uses space itself as a heat sink. Neat stuff.
https://news.slashdot.org/story/17/...passive-cooling-breakthrough-via-plastic-film
Too bad this "breakthrough" gets rid of 93 watts per square meter, while good old Sol delivers 1000 watts per square meter.
Like Gus Welter said: "The only problem with free energy is it costs so much".
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