Correct - if there is a HP on the mains. In my case there is not. Remember that my mains have a Q of about .5, about 60 Hz fs, so they do roll-off gradually, and this, in effect, is the HP filter.
I asked a very similar question in this very thread.
Post #2132
It's a weird thing the Geddes multiple sub setup. 1st it has bandpass subs, then it doesn't, then it has the mains running full range, but then it has 30Hz high passes on them. Then it realises that the sealed mains are on a 2nd order roll off any way. It says that there are no crossovers on the subs, but then it says there are but they are staggered. It's left me a bit confused tbh, so much so that I've ended up leaning more towards the Harman / Toole/ Welti style.
Rob.
No offense Rob
But Earl writes this - and I quote - copy paste:
"What you are missing is that I have never suggested not using "lowpass filters on the subs". I always have. The question is where! They should not all be at the same frequency. Some sub/positions work better for the upper LFs and thus their LP freq is higher. The idea is to blend everything together smoothly, not abruptly.
"No crossover" is not the same thing as "No LP"."
I think there is nothing to be misunderstood. I though too, that LP and crossover is kinda the same. But the difference is, that a LP or HP filter adds phase problems - if the driver or cabinet construction itself makes the sound roll-off - then you have a "natural" LP or HP - but no phase problems. At higher frequencies the phase-shift is barely audible between a midrange and a tweeter at around 1-3Khz - if ever. So here a LP/HP filter is fine.
But at lower frequencies it is a problem for making sound from different sources at different places, blend nicely/smoothly.
Having one PEQ to smooth out a 30hz problems on the mains - is a compromise I would be willing to make too. But that's not a HP
In the end, if your looking for the perfect answer - there is none - it's to complex. As Earl also points out several times, somewhere in the thousands of posts - If you bought his system and followed his guide - then it will work like he intended. But If you have your own system and just want to kinda copy the "multi-sub-trick" - then you have to interpolate.
You see - everyone has their own perfect driver, listening space and interesting preference towards choise of electronics and the way it's hooked up - I have too. But when you sloooowly starts to get how sound works and how we listen - then you can be creative and make you system do almost the same. It's like a huge equation - where you have to understand which parameters you can change more easily and without compromise - than others
Yeah I think the bottom line in this method is to have as many low frequency sources as possible, distributed in the room. But after about four subs adding more is diminishing returns. After all, no need to spend money more than that. If mains play low, good, it is two more low frequency sources! so don't use highpass on the main speakers.
For subs, the point is to average out room related issues across the listening area. Playing around with each sub lowpass filter and gain and other parameters will help to adjust the frequency response to be good/similar on multiple listening seats. With one or two subs you might be able to adjust the response for just one seat good while making the others seats response worse. Pretty clear to me High pass on subs, or specific 60hz lowpass on mains just happen to relate to other things in the system, like protecting a BR sub from overexcursion or mains driver parameters that are optimized for efficiency for example knowing that subs will handle the lows so Fs can be whatever and sealed enclosure can be used. Another compromise well thought out There are lots of things to balance to get good overall system.
Use multiple low frequency sources to be able to optimize low frequency response on multiple listening positions in the room.
For subs, the point is to average out room related issues across the listening area. Playing around with each sub lowpass filter and gain and other parameters will help to adjust the frequency response to be good/similar on multiple listening seats. With one or two subs you might be able to adjust the response for just one seat good while making the others seats response worse. Pretty clear to me
High pass on subs, or specific 60hz lowpass on mains just happen to relate to other things in the system, like protecting a BR sub from overexcursion or mains driver parameters that are optimized for efficiency for example knowing that subs will handle the lows so Fs can be whatever and sealed enclosure can be used. Another compromise well thought out There are lots of things to balance to get good overall system.Use multiple low frequency sources to be able to optimize low frequency response on multiple listening positions in the room.
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It doesn't matter because it is the sum that one is interested in not the subs alone.None taken
So if you were to switch off the mains then what does the combined subs response look like at listening position ?
That's the goal and it can be done. I've done it several times. The more variables one has to manipulate the better the results can be, but the harder they are to achieve.
And yes, I have evolved my approach. I no longer use any bandpass subs, they were too hard to get right. Closed box is much easier.
A "crossover has a HP and LP set to the same frequency. I have always used LP functions on the subs, sometime electronic, sometimes acoustic, but that doesn't matter. I have never used "crossovers".
"Confusion" is in the eye of the beholder. I was never confused.
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Ok Earl,
I think it's getting clearer. Your multisub setup has various low pass slopes applied to the subs, which blend to create 1 slope at listening position / area and your mains have a 2nd order acoustic highpass on them.(at approx. 60Hz) There is no point at which the subs 'hand over' to the mains, because there is no crossover.
I for one am interested in the combined response of the subs on their own, and what the response looks like on its own, what with this being a subwoofer setup discussion on a subwoofer forum.
I never inferred that it was you who was confused btw, I said it was me quite clearly
Cheers,
Rob.
I think it's getting clearer. Your multisub setup has various low pass slopes applied to the subs, which blend to create 1 slope at listening position / area and your mains have a 2nd order acoustic highpass on them.(at approx. 60Hz) There is no point at which the subs 'hand over' to the mains, because there is no crossover.
I for one am interested in the combined response of the subs on their own, and what the response looks like on its own, what with this being a subwoofer setup discussion on a subwoofer forum.
I never inferred that it was you who was confused btw, I said it was me quite clearly
Cheers,
Rob.
The thread topic is "Multiple Small Subs - Geddes Approach" which includes the mains, so it's logical to consider them. I've never looked at the subs alone because, to me, what they look like alone doesn't matter. I tend to shy aware from irrelevant data.
But your comments were quite critical about a technique that you clearly did not understand. Wouldn't it be better not to criticize the technique until you actually understood it.
But your comments were quite critical about a technique that you clearly did not understand. Wouldn't it be better not to criticize the technique until you actually understood it.
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Sorry Earl but when you repeatedly make comments such as 'no crossover' and 'large overlap between mains and subs' then it's not hard to see how it can be confusing when there are actual acoustic slopes in place on both the mains and the subs.
Maybe my comments were showing my frustration with the lack of clarity of the technique rather than a critique of the technique itself.
Rob.
Maybe my comments were showing my frustration with the lack of clarity of the technique rather than a critique of the technique itself.
Rob.
Perhaps. But that is not the way that it sounded.
There is a "lack of clarity" because there simply isn't one-way to do things. Every room and situation is different and so a cookbook type of recipe is not feasible and would probably wouldn't work very well either. You have to grasp the concepts and apply them to your specific situation. The concepts, I agree, are not simple and certainly not usual audio dogma. So I understand how you might be confused.
I get annoyed when people refer to any HP or LP filter as being a "crossover". That is not how I define things.
I think we've got to the crux of the matter. I get confused when people say there is 'no crossover' when there is a low pass on the subs and a high pass on the mains, creating a 'seamless blend' between the two.
I define a combination of high and lowpass slopes that achieve a transition from a subwoofer to a set of mains as a crossover, even if the electrical -6dB points are not set at exactly the same frequency.
Hence my confusion.
Rob.
Ah ha, "the light finally turns on" (or perhaps, the "brick finally hit me on the head!) - these last couple of posts clears up some confusion of mine too - makes much more sense now
Thanks very much Earl for your patience over the years and also Rob for 'high lighting' the confusion in the terms.
Thanks very much Earl for your patience over the years and also Rob for 'high lighting' the confusion in the terms.
This 'cross' could still take place if the mains were full range and the subs were rolled off much higher.. it would simply make less sense to do so. The speakers are band-limited allowing them to work together over the independent room problem where this can best help.
And why not? Speakers have a rolloff whether they have an electrical filter or not. Adding such a filter might signify that a choice has been made, nothing more.
Hello dr. Geddes,
I would like to ask you for your help.
I finally got 4 subs for my studio (control room) to solve room frequency response (room modes) with multisub approach.
I´m using 4 pieces of Presonus T10 Temblor ported subs (price/performance) - with frequency response 20Hz to 200Hz (+-3dB) with my mains.
I managed to get pretty flat frequency response of the room (+-3dB response curve) but I think that decay time is not good. The placement of the subs is asymmetrical, as Mr. Duke described for his system The Swarm. I´m also planning to elevate one of the subs above the center line. I have some absorption on the wall and in the corners (but still need to solve some flutter echoing).
First I placed my mains the best I could then I added 1st sub in the front right corner and set the gain, phase and add some EQ on that sub to bring a lot of low end from 20Hz to 40Hz to get best response possible. It´s strange that the sub didn´t deliver 20Hz to 40Hz spectrum naturally; despite manufacturer claims that T10 Temblor delivers 20Hz to 200Hz (+-3dB response curve and 20Hz -3dB), maybe there is some modal issue or something, I don´t know.
Then I added 2nd sub on the opposite wall, have set the gain, phase and corrected only one frequency with EQ on that sub.
Then I added 3rd sub along the long right wall pretty close to sitting position, have set the gain and phase and the 4th sub on the opposite left long wall, near front left corner and have set the gain and phase.
I have also corrected some critical mid and high frequencies of the main speakers with graphical EQ on my DSP.
During the placement and measuring process I also tried to set the delay times of the subs with the DSP but it didn´t make any significant change. I also set the HPF on the mains at 45Hz because I I´ve noticed some distortion lower than that freq. All subs have LPF at 130Hz to blend with main speakers as much as possible.
Please see my print screen of the final measurements, especially the waterfall (critical decay times) and some photos of the sub placement, absorption on the walls and corners, etc.
Measurments are having 1/6 smoothing. I can also send you REW measurement file if needed.
Should I repeat the whole procedure and set the subs with no prior dsp EQ and set the EQ on the end?
Should I bring up missing low end frequencis at 20Hz to 40Hz with the dsp EQ or leave just natural sub response?
Your help would be much appreciated. Thank you in advance!
I would like to ask you for your help.
I finally got 4 subs for my studio (control room) to solve room frequency response (room modes) with multisub approach.
I´m using 4 pieces of Presonus T10 Temblor ported subs (price/performance) - with frequency response 20Hz to 200Hz (+-3dB) with my mains.
I managed to get pretty flat frequency response of the room (+-3dB response curve) but I think that decay time is not good. The placement of the subs is asymmetrical, as Mr. Duke described for his system The Swarm. I´m also planning to elevate one of the subs above the center line. I have some absorption on the wall and in the corners (but still need to solve some flutter echoing).
First I placed my mains the best I could then I added 1st sub in the front right corner and set the gain, phase and add some EQ on that sub to bring a lot of low end from 20Hz to 40Hz to get best response possible. It´s strange that the sub didn´t deliver 20Hz to 40Hz spectrum naturally; despite manufacturer claims that T10 Temblor delivers 20Hz to 200Hz (+-3dB response curve and 20Hz -3dB), maybe there is some modal issue or something, I don´t know.
Then I added 2nd sub on the opposite wall, have set the gain, phase and corrected only one frequency with EQ on that sub.
Then I added 3rd sub along the long right wall pretty close to sitting position, have set the gain and phase and the 4th sub on the opposite left long wall, near front left corner and have set the gain and phase.
I have also corrected some critical mid and high frequencies of the main speakers with graphical EQ on my DSP.
During the placement and measuring process I also tried to set the delay times of the subs with the DSP but it didn´t make any significant change. I also set the HPF on the mains at 45Hz because I I´ve noticed some distortion lower than that freq. All subs have LPF at 130Hz to blend with main speakers as much as possible.
Please see my print screen of the final measurements, especially the waterfall (critical decay times) and some photos of the sub placement, absorption on the walls and corners, etc.
Measurments are having 1/6 smoothing. I can also send you REW measurement file if needed.
Should I repeat the whole procedure and set the subs with no prior dsp EQ and set the EQ on the end?
Should I bring up missing low end frequencis at 20Hz to 40Hz with the dsp EQ or leave just natural sub response?
Your help would be much appreciated. Thank you in advance!
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This is with 4 small subs. 3 klipsch sw350’s. Two of those in cabinets mounted to a wall with ventilation under. One more on the right of my couch and an energy 10” to the left of couch. 3(8’s) and one 10. Not too bad for room gain looks like. This is no eq beside me playing with things in roomeq/distance and the 10” sub has a full phase dial I can adjust to get it to play well with the others.
Just added a dsp in but haven’t redone things yet to see if I can get it any better.
Just added a dsp in but haven’t redone things yet to see if I can get it any better.
Attachments
Hello.
Thank you for your reply. I´m sorry, I uploaded pictures via google email account so I don´t know what happened. It displays the photos to me.
Anyway I´ll to upload them again, no problem
Studio freq response measurment - 1 - Image on Pasteboard
Pasteboard - Uploaded Image
Pasteboard - Uploaded Image
Control Room multisub placement (panorama) - 2 - Image on Pasteboard
Thank you for your reply. I´m sorry, I uploaded pictures via google email account so I don´t know what happened. It displays the photos to me.
Anyway I´ll to upload them again, no problem
Studio freq response measurment - 1 - Image on Pasteboard
An externally hosted image should be here but it was not working when we last tested it.
Pasteboard - Uploaded Image
An externally hosted image should be here but it was not working when we last tested it.
Pasteboard - Uploaded Image
An externally hosted image should be here but it was not working when we last tested it.
Control Room multisub placement (panorama) - 2 - Image on Pasteboard
An externally hosted image should be here but it was not working when we last tested it.
Awesome, the freq response o the sub looks great! Thanks for sharing. Do you also have multisub setup?
Your situation looks to me like you have the best that you can do with your constraints. Clearly the rooms two lowest modes have little damping and hence the long decay. This cannot be corrected with the subs because it is a room problem. Your bass traps are clearly not working at these very low frequencies. The only solution down that low is to have the walls themselves act as absorbers - just like I do in my room. This is the only technique that can provide substantial damping at these VLF.
I would say to just live with what you have unless it is unacceptable. Then you need to make the back wall floating with a lot of damping.
Thank you for your review dr. Geddes, I really appreciate it.
My bass traps are made of ticker MDF and filled with mineral wool insulation Knauf DP80, so yeah, like you said, they are not suitable for very low region. It seems I will have to live with that until I will construct diaphragmatic absorbers (Acoustic Fields blueprint) like I planned before multisub setup.
Do you think that diaphragmatic absorbers would be enough in the rear corners or should cover the whole rear wall with them? How did you construct your walls? Do you have floating drywall of somekind?
Do you think that my Sub 1 in the corner should face away from the bass trap?
My bass traps are made of ticker MDF and filled with mineral wool insulation Knauf DP80, so yeah, like you said, they are not suitable for very low region. It seems I will have to live with that until I will construct diaphragmatic absorbers (Acoustic Fields blueprint) like I planned before multisub setup.
Do you think that diaphragmatic absorbers would be enough in the rear corners or should cover the whole rear wall with them? How did you construct your walls? Do you have floating drywall of somekind?
Do you think that my Sub 1 in the corner should face away from the bass trap?