Thanks
So distortion is why to use a slot? I read that she go low but not very wide bandwith,
I will try them one day I go first read about it more, I am a OB man, the H frames are very nicely, A dipole is maybe better, I did saw here a PPSL with two round pipes who are open, it did look like a open system that way. I do use push pull in the H frames, I have also test a resistance box, Wel dat klonk niet verkeert maar heeft correctie nodig.
Sometimes I think making boxes is more interesting then amps, but fortunaly I have to learn more first, schoenmaker blijf bij je leest.
Oke, slaap ze want ik ga ook.
vrg regards.
So distortion is why to use a slot? I read that she go low but not very wide bandwith,
I will try them one day I go first read about it more, I am a OB man, the H frames are very nicely, A dipole is maybe better, I did saw here a PPSL with two round pipes who are open, it did look like a open system that way. I do use push pull in the H frames, I have also test a resistance box, Wel dat klonk niet verkeert maar heeft correctie nodig.
Sometimes I think making boxes is more interesting then amps, but fortunaly I have to learn more first, schoenmaker blijf bij je leest.
Oke, slaap ze want ik ga ook.
vrg regards.
Yes, the plenum insures the drivers are aligned by their (acoustic) centre which insures the highest suppression of distortion. Indeed, by using them in a plenum (cavity) they will have less bandwidth.
You can use Push-Pull in Tapped horns (that looks like two open pipes on both sides of the cone). But that still means both sides are driven by the same ¼ wavelength system and not two different systems.
Loudspeaker systems are like antennas more or less and with some electronic knowledge you can explain speakers with passive component circuits. So it shouldn't be that difficult (voor een schoenmaker uit t land van leer)
Sleeplekker
You can use Push-Pull in Tapped horns (that looks like two open pipes on both sides of the cone). But that still means both sides are driven by the same ¼ wavelength system and not two different systems.
Loudspeaker systems are like antennas more or less and with some electronic knowledge you can explain speakers with passive component circuits. So it shouldn't be that difficult (voor een schoenmaker uit t land van leer)
Sleeplekker
The 1 magnet out, 1 magnet in is why the distortion is reduced.
Think of the older m&k subwoofers.
The slot puts the drivers closer, thusly making it easier for them to reduce distortion to a higher frequency (because they are 1/4 wavelength away at the harmonic added distortion an octave above say an 80hz tone). So if you want to go up to 300hz, you need to have the drivers 1/4 wavelength of 600hz (to catch the fake 600hz tone that shouldn't be there but created when you play 300hz tone), so 1/4 of 6", that's an inch and a half.
Norman
Think of the older m&k subwoofers.
The slot puts the drivers closer, thusly making it easier for them to reduce distortion to a higher frequency (because they are 1/4 wavelength away at the harmonic added distortion an octave above say an 80hz tone). So if you want to go up to 300hz, you need to have the drivers 1/4 wavelength of 600hz (to catch the fake 600hz tone that shouldn't be there but created when you play 300hz tone), so 1/4 of 6", that's an inch and a half.
Norman
Although I agree with the explanation, I don't agree with your calculation
. 1/4 wavelength of 600Hz is:(344m/s : 600Hz) / 4 = 14,3cm = 5.64 inch
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You guys are off the mark.
The cancellation is only for the 2nd harmonic distortion. This is caused by an asymmetry when the cone goes inward vs outward.
The plenum acts as a cavity which itself can act as a low pass filter. Depending on the frequency region it might be lowering some odd harmoic (eg 3rd) distortion
The cancellation is only for the 2nd harmonic distortion. This is caused by an asymmetry when the cone goes inward vs outward.
The plenum acts as a cavity which itself can act as a low pass filter. Depending on the frequency region it might be lowering some odd harmoic (eg 3rd) distortion
"you say a vented box but there is more these box go low with a high efficienty as i did read because horns are involved as mid high."
The 6th order vented alignment I generally use gives good output for PA with only two cabinets per side. The individual drivers are about No=4%, so the stacked pair should be about 16% (104dB/W/1M in 2Pi). My original design is 8Ω per cabinet, so they appear to be 107dB/2.83V/1M. The stacked horn mids I use are 110dB/2.83V/1M, the HF horn is 113dB/2.83V/1M.
There may be some gain beyond a simple reflex because of the large frontal area (48H x 36W) driven from the narrow plenum exit. Nelson Pass measured a gain of about 2.78dB on his slot-loaded (not push-pull) six 8" open baffle project. I see this more as a transition from 2Pi to 4Pi, but only above 100hz or so.
The prototype PPSL had a port resonance at about 800hz, but it proved not to be an issue in actual use. I have used one up to 250hz, but all my others have been crossed at 150hz (or lower). Les Hudson was able to get good sounding response to 400hz from a dual 12 PPSL with a minimum sized plenum, I don't know what drivers he was using though.
A thank you to Djm for his drawings. I would not show the arrows for the ports, it will confuse some people (as the phase is inverted at the tuning frequency so that the pressure adds to the driver output).
The 6th order vented alignment I generally use gives good output for PA with only two cabinets per side. The individual drivers are about No=4%, so the stacked pair should be about 16% (104dB/W/1M in 2Pi). My original design is 8Ω per cabinet, so they appear to be 107dB/2.83V/1M. The stacked horn mids I use are 110dB/2.83V/1M, the HF horn is 113dB/2.83V/1M.
There may be some gain beyond a simple reflex because of the large frontal area (48H x 36W) driven from the narrow plenum exit. Nelson Pass measured a gain of about 2.78dB on his slot-loaded (not push-pull) six 8" open baffle project. I see this more as a transition from 2Pi to 4Pi, but only above 100hz or so.
The prototype PPSL had a port resonance at about 800hz, but it proved not to be an issue in actual use. I have used one up to 250hz, but all my others have been crossed at 150hz (or lower). Les Hudson was able to get good sounding response to 400hz from a dual 12 PPSL with a minimum sized plenum, I don't know what drivers he was using though.
A thank you to Djm for his drawings. I would not show the arrows for the ports, it will confuse some people (as the phase is inverted at the tuning frequency so that the pressure adds to the driver output).
The resonance looked to be from the very long ports (I like big ports), not the plenum.
I have tried filling the rear corners of the plenum with resin-coated fiberglass (DOW 703) and it seemed to help with the upper bandwidth of the cabinet. My next project will likely be a 4x 12 PPSL open-baffle unit with some inexpensive drivers from MCM that had a much higher Qts than advertised. It will probably look like an Apogee or Carver Amazing in the profile of the baffle, and use either a co-ax or full-range around 95dB~98dB above 200hz~300hz.
I have tried filling the rear corners of the plenum with resin-coated fiberglass (DOW 703) and it seemed to help with the upper bandwidth of the cabinet. My next project will likely be a 4x 12 PPSL open-baffle unit with some inexpensive drivers from MCM that had a much higher Qts than advertised. It will probably look like an Apogee or Carver Amazing in the profile of the baffle, and use either a co-ax or full-range around 95dB~98dB above 200hz~300hz.
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Djk, if you are up for some experimentation you could try passive drivers/membranes and a basreflex port in one system (aka Philips Woox system). Very efficient in even smaller packages. It can be used in a PPDPSL (Push-Pull-Dual-Passive-Slot Loaded). Another advantage is that the ports become significant shorter...
(Push-Pull-Dual-Passive-Slot Loaded). Another advantage is that the ports become significant shorter...
"wOOx technology (rendered wOOx) is a brand created by Royal Philips Electronics to identify loudspeaker systems that employ passive radiator technology and active equalization to maximize the output of the passive diaphragm. wOOx technology is primarily concerned with low frequency reproduction, in which resonant systems are commonly employed to augment the output of bass drivers to improve the overall efficiency of the loudspeaker system through the bass frequency range. wOOx Technology involves the synergistic optimization of three components of the loudspeaker system: the bass radiator, the active bass driver, and active equalization."
Using a PR and a port in the same box makes no sense to me, and the Philips system does not do such.
I have used a PR with the PPSL it's fine, but not suitable for transport.
Using a PR and a port in the same box makes no sense to me, and the Philips system does not do such.
I have used a PR with the PPSL it's fine, but not suitable for transport.
"the Philips system does not do such."
Lol, I can assure they do (Philips SW945 and Philips SW8000SA for instance)
Actually, there is also a Danish company (SA) that calls it "Hybrid-reflex".
"I have used a PR with the PPSL it's fine, but not suitable for transport"
Not sure what you have build but they become smaller than the usual PPSL's.
Lol, I can assure they do
(Philips SW945 and Philips SW8000SA for instance)Actually, there is also a Danish company (SA) that calls it "Hybrid-reflex".
"I have used a PR with the PPSL it's fine, but not suitable for transport"
Not sure what you have build but they become smaller than the usual PPSL's.
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"Using a PR and a port in the same box makes no sense to me"
Maybe I should give you a hint, bassdrums. The skin you hit is your active membrane, the front skin is the passive membrane. In order to tune it lower and give it an extra boost they start to cut a whole in the front skin, years later they even put a basreflex port in…;
Maybe I should give you a hint, bassdrums. The skin you hit is your active membrane, the front skin is the passive membrane. In order to tune it lower and give it an extra boost they start to cut a whole in the front skin, years later they even put a basreflex port in…;
"Not sure what you have build but they become smaller than the usual PPSL's. "
They are already 6th order with 6dB of boost. The only way they could be smaller and go as low would be with more boost.
Not suitable for transport refers to the fact that a PR tuned low in a small box will have very high mass. Without a mechanical stop on the PR for transport it will damage the woofer cones. I had this happen with some 6th order EV that the seller forgot to take the weight off the passive before transporting. The original version had a board screwed across the front of the cabinet and into the front of the PR, you had to remove to use, and replace for transit.
I have some Beyma 12LX60 to make a very small PPSL with a huge and heavy PR. I'm still thinking about some of the details on this (securing the PR for transit).
"The skin you hit is your active membrane, the front skin is the passive membrane. "
I think we are comparing apples and kiwi fruit here. I am not trying to make a one note ringing device. Drums can be hard to get mic'd up for good sound through a PA. I can usually get it to sound better than it does on stage, but it can be a challenge. Most drummers kit is sadly out-of-tune and they don't even have a clue.
My friend Steve carries a complete backline when he does a large job, that way he has some good instruments, amps and drums available if needed (five different snare drums).
http://i56.photobucket.com/albums/g196/dkleitsch/COE08-3.jpg
(Steve with 1/3 of his PA, although you would have a hard time recognizing him today after he cut his hair and lost 50 lbs. The JBL 2380s have been replaced with EV HP640s and he has six Crest amplifiers in two racks now)
They are already 6th order with 6dB of boost. The only way they could be smaller and go as low would be with more boost.
Not suitable for transport refers to the fact that a PR tuned low in a small box will have very high mass. Without a mechanical stop on the PR for transport it will damage the woofer cones. I had this happen with some 6th order EV that the seller forgot to take the weight off the passive before transporting. The original version had a board screwed across the front of the cabinet and into the front of the PR, you had to remove to use, and replace for transit.
I have some Beyma 12LX60 to make a very small PPSL with a huge and heavy PR. I'm still thinking about some of the details on this (securing the PR for transit).
"The skin you hit is your active membrane, the front skin is the passive membrane. "
I think we are comparing apples and kiwi fruit here. I am not trying to make a one note ringing device. Drums can be hard to get mic'd up for good sound through a PA. I can usually get it to sound better than it does on stage, but it can be a challenge. Most drummers kit is sadly out-of-tune and they don't even have a clue.
My friend Steve carries a complete backline when he does a large job, that way he has some good instruments, amps and drums available if needed (five different snare drums).
http://i56.photobucket.com/albums/g196/dkleitsch/COE08-3.jpg
(Steve with 1/3 of his PA, although you would have a hard time recognizing him today after he cut his hair and lost 50 lbs. The JBL 2380s have been replaced with EV HP640s and he has six Crest amplifiers in two racks now)
"The plenum acts as a cavity which itself can act as a low pass filter. Depending on the frequency region it might be lowering some odd harmoic (eg 3rd) distortion "
Yes, the low-pass of the plenum cavity does roll off the higher odd harmonics, at about a 12dB/oct rate above the depth of plenum cavity corner. The 'gargle' is also reduced as the cones are moving sideways rather than-towards-and-away from you (think of how it sounds to talk through a fan).
Yes, the low-pass of the plenum cavity does roll off the higher odd harmonics, at about a 12dB/oct rate above the depth of plenum cavity corner. The 'gargle' is also reduced as the cones are moving sideways rather than-towards-and-away from you (think of how it sounds to talk through a fan).
"Not suitable for transport refers to the fact that a PR tuned low in a small box will have very high mass. Without a mechanical stop on the PR for transport it will damage the woofer cones. I had this happen with some 6th order EV that the seller forgot to take the weight off the passive before transporting. The original version had a board screwed across the front of the cabinet and into the front of the PR, you had to remove to use, and replace for transit."
Ah, I see the difference now. We experimented with larger PR’s instead of same diameters and in 4th order to obtain a less steep roll-off from smaller cabinets at costs of gain of course. The PR’s were tuned above the ports, which allows them to be lighter. Our problem was/is to get enough excursion from them, since we used modified PR's made from standard drivers. I wish some Italian PA brand would jump into this because I still see some benefits for this application. The PR's should also benefit from your slot loaded push-pull idea, although we haven't tried that.
What kind of PR’s did you use?
Ah, I see the difference now. We experimented with larger PR’s instead of same diameters and in 4th order to obtain a less steep roll-off from smaller cabinets at costs of gain of course. The PR’s were tuned above the ports, which allows them to be lighter. Our problem was/is to get enough excursion from them, since we used modified PR's made from standard drivers. I wish some Italian PA brand would jump into this because I still see some benefits for this application. The PR's should also benefit from your slot loaded push-pull idea, although we haven't tried that.
What kind of PR’s did you use?
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Errata:
#366 should read "I see this more as a transition from 2Pi to 1Pi," not "I see this more as a transition from 2Pi to 4Pi, "
" but a ppsl has a lot more muscles in the low end?."
Read #366 please.
A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB).
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB).
The theoretical limit to efficiency from coupling is 25%, plus the increase in the Di (Directivity index) from the large front baffle surface (transition from 2Pi to 1Pi).
With four cabinets a side the stacked pair of 12s mid-bass/mid-range horns have a hard time keeping up, as does the HF compression driver.
People unfamiliar with the performance of these cabinets may have problems from feedback from their use of compression on drum mics and bass boost at the port tuning frequency (around 30hz for these).
I had to come to the rescue of a FOH engineer for a national act that was using an eight bass cabinet system indoors and was making people run for the door in a club that held about 1300 people. He got it into feedback at 30hz and because these have such low distortion he couldn't tell what was causing it. I stepped in, turned the EQ back to flat on his drum mics, and backed-off the drum mic compressors from 15dB~20dB over threshold to about 6dB and adjusted the mix for him. The amount of 'punch' and 'slam' on the drums was unreal!
Another time on an outdoor stage a mic got disconnected and then plugged back in (without muting the channel) with the system gain at full volume! It felt like the cannon shots in the 1812 overture (the system being time-aligned), and had people running for cover. The system owner (Steve) got this sick look on his face and timidly started checking out the system. The 6th order filter (built into the crossover) protected the bass cabinets and an ultrasonic filter (also built into the crossover) protected the HF drivers.
#366 should read "I see this more as a transition from 2Pi to 1Pi," not "I see this more as a transition from 2Pi to 4Pi, "
" but a ppsl has a lot more muscles in the low end?."
Read #366 please.
A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB).
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB).
The theoretical limit to efficiency from coupling is 25%, plus the increase in the Di (Directivity index) from the large front baffle surface (transition from 2Pi to 1Pi).
With four cabinets a side the stacked pair of 12s mid-bass/mid-range horns have a hard time keeping up, as does the HF compression driver.
People unfamiliar with the performance of these cabinets may have problems from feedback from their use of compression on drum mics and bass boost at the port tuning frequency (around 30hz for these).
I had to come to the rescue of a FOH engineer for a national act that was using an eight bass cabinet system indoors and was making people run for the door in a club that held about 1300 people. He got it into feedback at 30hz and because these have such low distortion he couldn't tell what was causing it. I stepped in, turned the EQ back to flat on his drum mics, and backed-off the drum mic compressors from 15dB~20dB over threshold to about 6dB and adjusted the mix for him. The amount of 'punch' and 'slam' on the drums was unreal!
Another time on an outdoor stage a mic got disconnected and then plugged back in (without muting the channel) with the system gain at full volume! It felt like the cannon shots in the 1812 overture (the system being time-aligned), and had people running for cover. The system owner (Steve) got this sick look on his face and timidly started checking out the system. The 6th order filter (built into the crossover) protected the bass cabinets and an ultrasonic filter (also built into the crossover) protected the HF drivers.
I have a couple of question to ask.
Is there a upper limit for compression ratio for the plenum? I am working out the compression ratio by dividing the combined SD of the drivers by the front area of the plenum. I am working on a design using two RCF 15p200AK and could easily get a very high compression ratio of 5:1 now building it with a compression ratio of 2.7:1. I would imagine like horns the comp ratio depends on the size of the driver and how strong the cone is.
Next question, does the air mass in the plenum lower the cone resonance? I think it does. Can this lowering of resonance be calculated or only measured?
Is there a upper limit for compression ratio for the plenum? I am working out the compression ratio by dividing the combined SD of the drivers by the front area of the plenum. I am working on a design using two RCF 15p200AK and could easily get a very high compression ratio of 5:1 now building it with a compression ratio of 2.7:1. I would imagine like horns the comp ratio depends on the size of the driver and how strong the cone is.
Next question, does the air mass in the plenum lower the cone resonance? I think it does. Can this lowering of resonance be calculated or only measured?
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