Phase shifts.
If omnifex is correct ,then it would make sense to follow the advice..but since i dont really see proof,,i just see speakers that are slightly out of phase,i dont buy it
Cheers!
If omnifex is correct ,then it would make sense to follow the advice..but since i dont really see proof,,i just see speakers that are slightly out of phase,i dont buy it
Cheers!
reply
One important thing to remember do NOT tune the port lower than the speaker resonance frequency as this will unload the driver and might distroy it.
So if the driver resonance frequency was 50hz and the enclosure was tuned to 30hz it would distroy the driver.
One important thing to remember do NOT tune the port lower than the speaker resonance frequency as this will unload the driver and might distroy it.
So if the driver resonance frequency was 50hz and the enclosure was tuned to 30hz it would distroy the driver.
Bull, yes the JBL 4518 cabinet that I just finshed up making looks like that one, the CV cabinets are the B36 that Omni was talking about, and then I believe the 15 inch cabinet that I have is the one shown on this link and listed as the "eliminator"
http://www.mcsoundlight.com/horn.htm
http://www.mcsoundlight.com/horn.htm
the problem is the following.
Horn unloads.
Port is tuned near the unloading part.
Below Horn and port tuning=extremely high Excursion.
Fs is independant,and normally it is ABOVE horn Fc and port Fb
Omnifex=what your graphs are showing=
red line=closer to 90*
green= nearer 180*
the interaction between differently tuned subs as far as i know,i assure you, is not as you say.
It would help if your graph didnt have so many +-180* markings.
Backloaded excursion ( no rear sealed chamber)
Attachments
mikee12345
I can asssure you the graph is correct!
My graph showed you a sealed cabinet verses a reflex cabinet.
We all know the sealed cabinet will always be in phase.
However, any reflex cab that gets frequencies below its
tuning frequency will be out of phase.
I do Sound Reinforcement, and, Phase problems, Time
delay, and, comb filters, can be a B.I.T.C.H, when you
are using multiple cabinets in an array.
This is Why you cannot mix and match different subs together.
Sealed Bass Horns, will never work with Bass Reflex Cabs.
However, Sealed Bass Horns, and, Sealed Bass Sub, will
work with no problems in the Phase Department.
But, you will have time delay issues.
Why do you think Concert Systems don't use two different
bass enclosures. It cause more harm than good.
I can asssure you the graph is correct!
My graph showed you a sealed cabinet verses a reflex cabinet.
We all know the sealed cabinet will always be in phase.
However, any reflex cab that gets frequencies below its
tuning frequency will be out of phase.
I do Sound Reinforcement, and, Phase problems, Time
delay, and, comb filters, can be a B.I.T.C.H, when you
are using multiple cabinets in an array.
This is Why you cannot mix and match different subs together.
Sealed Bass Horns, will never work with Bass Reflex Cabs.
However, Sealed Bass Horns, and, Sealed Bass Sub, will
work with no problems in the Phase Department.
But, you will have time delay issues.
Why do you think Concert Systems don't use two different
bass enclosures. It cause more harm than good.
Yeah, I've heard all kinds of different things can happen. I was talking to one of the guys at QSC about using a pair of JBL 2226H and JBL 2240H woofers for subs, and I told him how I planned to run them parallel off the same amp, and he said that it would cause a "honey comb" effect because one of the woofers has a 97dB sensitity, and the other has a 98dB sensitivity. He said I should run one set on one side of the amp, and the other set on the other side. But I wasn't about to go running another set of speaker wire over to the cabinets because they sounded fine, but I can see how it gets really compilcated.
So if I'm tuning all these W-Bin's ports to 40Hz, anything below 40Hz is going to be out of phase? What's the problem with this, is it that noticable?
So if I'm tuning all these W-Bin's ports to 40Hz, anything below 40Hz is going to be out of phase? What's the problem with this, is it that noticable?
gjeff80
You are tuning all cabinets, at 40 Hz. You wouldn't
have any problems.
The problem(s) only occur when you have one box
tuned at 60, one at 50, one at 40, and, one at 30Hz,
then feed a 30 Hz signal.
You are tuning all cabinets, at 40 Hz. You wouldn't
have any problems.
The problem(s) only occur when you have one box
tuned at 60, one at 50, one at 40, and, one at 30Hz,
then feed a 30 Hz signal.
about different tunings and sealed/ported boxes in same setup-
if its such a big deal,then why doesnt JBL mention it in any tech papers,nor Adireaudio...because it isnt true.
backup your statements with references omnifex,not your own experience,or else we are into religion of audio not science
Cheers!
if its such a big deal,then why doesnt JBL mention it in any tech papers,nor Adireaudio...because it isnt true.
backup your statements with references omnifex,not your own experience,or else we are into religion of audio not science
Cheers!
BS lies,and proof.
in a word, no.
2 subs at a distance apart,when one isnt exactly between them will get comb filtering effects.
www.prosoundweb.com talks alot about this.
the different efficiencies,are very similar, and the efficiency different itself DOES NOT cause any strange effects.
+-3db is close (perceived by the ear)
Read tech papers such as -jbl system design paper.
Cheers guys!
in a word, no.
2 subs at a distance apart,when one isnt exactly between them will get comb filtering effects.
www.prosoundweb.com talks alot about this.
the different efficiencies,are very similar, and the efficiency different itself DOES NOT cause any strange effects.
+-3db is close (perceived by the ear)
Read tech papers such as -jbl system design paper.
Cheers guys!
Hi Omnifex
You havn't got the idea about phase relations between multiple subwoofers.
The graph you posted shows exactly that. But the comparison to the sealed box is incorrect.
It's true that below Fb the woofer and port are working towards an out of phase conditon until Fl, where the port and diaphragm are completely 180o out of phase and acoustic output is zero.
The issue at hand is how the ported box unloads below Fb and completely at Fl. A bass reflex cabinet should not be used below Fl at any time. That's because there's no coupling between the cone and vent - the cone moves out while the vent takes air in and vice versa, so acoustic output is nil and excursion is high.
Onto your other point:
The same reasoning applies here. It's the woofer and port that work towards an out of phase condition below Fb and down to Fl where they are completely 180o apart and theres no acoustic output. Sometimes the system has usable output to a certain point below Fb - this is output you can take advantage of and use.
The issue at hand here is the port and diaphpram are moving towards an out-of-phpase condition below Fb, and they are moving completely out of phase at Fl. Thats why acoustic output drops rapidly below Fl. The issue is NOT a phasing problem causing cancellations between the two enclosures at all, so having a box tuned at 30Hz and one tuned at 40Hz do not combine destructively.
Unless your sitting a mile away from two subwoofers, then they arn't causing any interferance between each other. At low frequencies, wavelengths are very long meaning that any path length differences simply won't happen inside a typical 4meter long room. Complete cancellation happens when two sound sources are 180o apart. Phase is also destructive +/-45degrees from this point, so phase is destructive when there is a distance differential between drivers which is between 135degrees and 225degrees and complete cancellation occurs when there is a distance differential of 180degrees between two sound sources. For a path length difference to cause two seperate sound sources which are playing subwoofer frequencies to become 180o apart or between 135o and 225o, distances involved are very large. Path length differences between two sound sources when presented a signal of 20Hz are between 21ft and 35ft for them to combine destuctively. Wavelength distances are smaller as frequency rises but at even 80Hz the wavelength is ~14ft. Exact critical distances can be calculated to find which vectors combine constructively and those that combine destructively if we know the exact phase response of the loudspeaker and crossover network.
At mid and high frequencies the room walls and objects within the room become reflectors, causing infinite phase angles so vectors where cancellations occur become impossible to calculate when these reflecting boundries are in place.
So unless your sitting extremely far away which would mean a stadium install where listeners can be far away - inside a home living room, low frequencies will combine without interferance. On the other hand, interferance patterns between two sound sources will emerge once you get to mid and high frequencies. What there can be at low frequencies is a fixed delay between sound sources, but multiple low frequency subwoofer enclosures regardless of weather they are vented or sealed, will not create phase cancellations between each other unless the environment is very large, but in a home, it is not.
Adrian
You havn't got the idea about phase relations between multiple subwoofers.
The graph you posted shows exactly that. But the comparison to the sealed box is incorrect.
It's true that below Fb the woofer and port are working towards an out of phase conditon until Fl, where the port and diaphragm are completely 180o out of phase and acoustic output is zero.
The issue at hand is how the ported box unloads below Fb and completely at Fl. A bass reflex cabinet should not be used below Fl at any time. That's because there's no coupling between the cone and vent - the cone moves out while the vent takes air in and vice versa, so acoustic output is nil and excursion is high.
Onto your other point:
The same reasoning applies here. It's the woofer and port that work towards an out of phase condition below Fb and down to Fl where they are completely 180o apart and theres no acoustic output. Sometimes the system has usable output to a certain point below Fb - this is output you can take advantage of and use.
The issue at hand here is the port and diaphpram are moving towards an out-of-phpase condition below Fb, and they are moving completely out of phase at Fl. Thats why acoustic output drops rapidly below Fl. The issue is NOT a phasing problem causing cancellations between the two enclosures at all, so having a box tuned at 30Hz and one tuned at 40Hz do not combine destructively.
Unless your sitting a mile away from two subwoofers, then they arn't causing any interferance between each other. At low frequencies, wavelengths are very long meaning that any path length differences simply won't happen inside a typical 4meter long room. Complete cancellation happens when two sound sources are 180o apart. Phase is also destructive +/-45degrees from this point, so phase is destructive when there is a distance differential between drivers which is between 135degrees and 225degrees and complete cancellation occurs when there is a distance differential of 180degrees between two sound sources. For a path length difference to cause two seperate sound sources which are playing subwoofer frequencies to become 180o apart or between 135o and 225o, distances involved are very large. Path length differences between two sound sources when presented a signal of 20Hz are between 21ft and 35ft for them to combine destuctively. Wavelength distances are smaller as frequency rises but at even 80Hz the wavelength is ~14ft. Exact critical distances can be calculated to find which vectors combine constructively and those that combine destructively if we know the exact phase response of the loudspeaker and crossover network.
At mid and high frequencies the room walls and objects within the room become reflectors, causing infinite phase angles so vectors where cancellations occur become impossible to calculate when these reflecting boundries are in place.
So unless your sitting extremely far away which would mean a stadium install where listeners can be far away - inside a home living room, low frequencies will combine without interferance. On the other hand, interferance patterns between two sound sources will emerge once you get to mid and high frequencies. What there can be at low frequencies is a fixed delay between sound sources, but multiple low frequency subwoofer enclosures regardless of weather they are vented or sealed, will not create phase cancellations between each other unless the environment is very large, but in a home, it is not.
Adrian
macky888 said:
I agree on what you say, for this is what I was explaining in
the first place. However, how many people know this? Very
few. Actually, you may find one of the reasons Pro Amplifier
Companies introduced 50, and, 30Hz cut off filters is
for this same reason.
You're talking about a living room. We are talking about a
W Bin used for Live Applications, in various venues.
Apples To Oranges
As you can see, this gentleman posted numerous questions
regarding the use of W Bins in regards, of live applications.
Not a living room. Using Multiples, various drivers, with
different TS specs.
Frankly, I can't see how/why someone would use a W Bin
in their homes, when they, like horns at high volumes will
throw the sound further than their "Sweet Spot".
I can't simulate how a sealed horn will react with a reflex
on a program. But, I can show how a sealed cabinet will
work with a Reflex cabinet. Which is what I've done.
And, once the phase chart says negative on one sub,
and neutral on the other sub, somethings not going to
sound right.
Best Regards,
Phase Relations
Hi Omnifex
I think that's the reason too. Most subwoofers used in pro sound applications are tuned around this area, so it makes sense to protect the driver at low frequencies by using a highpass filter where the driver unloads.
OK - must not have picked that up when I was skimming through the replies. But in any case, the same theory applies. Complete cancellation happens when two sound sources are 180o apart. Phase is also destructive +/-45o from this point, so phase is destructive when there is a distance differential between the sound sources and listener which is between 135o and 225o and complete cancellation occurs when there is a distance differential of 180o between two sound sources and the listener. I had originally thought this may have been for a home setup, but I see it isn't. In any case - the only thing different is that in your large stadium or other large venue, you'll run into vectors where two subwoofers will combine constructively, and area's where they interfere destructively. In the home, you won't. But when there's a path length difference causing two sound sources to be between 135o and 225o apart from the listener, then they'll cancel. The same theory applies.
You can use a sealed subwoofer in conjunction with a bass reflex subwoofer. The graph you posted simply shows the individual phase response of each subwoofer - i.e: sealed and vented, but that is it. It doesn't show cancellations between the two systems. You can calculate vectors where the distance between listener and each subwoofer causes a path length difference differential between 135o and 225o, which will determine which vectors or positions in 3D space will combine destructively. Likewise, you can calculate which vectors will combine constructively as well. A simple graph like the one you posted cannot demonstrate phase relations at every frequency and at every position in 3D space.
Two sealed subwoofer's will also cancel each other out when there's a path length difference between them causing the distance between listener and each subwoofer to be between 135o and 225o apart.
About the bass reflex cabinet; what I should have also mentioned, is that Fl resonance is always at a frequency well below cutoff, so the system can never be used there to begin with.
Baring all this in mind, I'm not saying that every vented subwoofer and every sealed subwoofer will necessarily sound good togethor. There's other things to consider - bandwidth, distortion, transient response, etc. If either one of the subwoofers performs poorly in one or more of these area's, then they may not be a good match.
My point is that when the distance between two sound sources causes the listener to percieve a 135o to 225o phase difference between them (subwoofer's in the example's we've been discussing), then they'll notice cancellations at these positions. And the two sound sources can be any kind of system you like - both sealed, both vented, one sealed and one vented, or whatever combination you like.
Adrian
Hi Omnifex
I think that's the reason too. Most subwoofers used in pro sound applications are tuned around this area, so it makes sense to protect the driver at low frequencies by using a highpass filter where the driver unloads.
OK - must not have picked that up when I was skimming through the replies. But in any case, the same theory applies. Complete cancellation happens when two sound sources are 180o apart. Phase is also destructive +/-45o from this point, so phase is destructive when there is a distance differential between the sound sources and listener which is between 135o and 225o and complete cancellation occurs when there is a distance differential of 180o between two sound sources and the listener. I had originally thought this may have been for a home setup, but I see it isn't. In any case - the only thing different is that in your large stadium or other large venue, you'll run into vectors where two subwoofers will combine constructively, and area's where they interfere destructively. In the home, you won't. But when there's a path length difference causing two sound sources to be between 135o and 225o apart from the listener, then they'll cancel. The same theory applies.
You can use a sealed subwoofer in conjunction with a bass reflex subwoofer. The graph you posted simply shows the individual phase response of each subwoofer - i.e: sealed and vented, but that is it. It doesn't show cancellations between the two systems. You can calculate vectors where the distance between listener and each subwoofer causes a path length difference differential between 135o and 225o, which will determine which vectors or positions in 3D space will combine destructively. Likewise, you can calculate which vectors will combine constructively as well. A simple graph like the one you posted cannot demonstrate phase relations at every frequency and at every position in 3D space.
Two sealed subwoofer's will also cancel each other out when there's a path length difference between them causing the distance between listener and each subwoofer to be between 135o and 225o apart.
About the bass reflex cabinet; what I should have also mentioned, is that Fl resonance is always at a frequency well below cutoff, so the system can never be used there to begin with.
Baring all this in mind, I'm not saying that every vented subwoofer and every sealed subwoofer will necessarily sound good togethor. There's other things to consider - bandwidth, distortion, transient response, etc. If either one of the subwoofers performs poorly in one or more of these area's, then they may not be a good match.
My point is that when the distance between two sound sources causes the listener to percieve a 135o to 225o phase difference between them (subwoofer's in the example's we've been discussing), then they'll notice cancellations at these positions. And the two sound sources can be any kind of system you like - both sealed, both vented, one sealed and one vented, or whatever combination you like.
Adrian
Can ay body run some software for me to Tune 5foot W bin chamber to a DAS 18S driver/ I have 4 of them in Keele bins and fell that someone has just lengthenedthe 85mm dia ports to try to go lower, they are 240 long .What parameters I have are Vas 303, Qts 0.329, fs 33, x max 6, 98db 1w/m. looking to tune at34-35hz as per original design ox box. Big thanks if anybody can offer usefull thoughts.
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