or Connect
AVS › AVS Forum › Audio › Subwoofers, Bass, and Transducers › Are three inexpensive subs better than one expensive sub-Dr. Earl Geddes Approach
New Posts  All Forums:Forum Nav:

Are three inexpensive subs better than one expensive sub-Dr. Earl Geddes Approach - Page 64

post #1891 of 2011
Here is the waterfall of my system with and without the J_Palmer_Cass MBM setup activated.

The upper section of the waterfall is my system's R & L main speakers plus ULF subwoofer.

The middle section of the waterfall is my system's R & L main speakers plus ULF subwoofer plus an added J_Palmer_Cass MBM connected in an overlap manner to cover the mid and upper bass.



post #1892 of 2011
Quote:
Originally Posted by otk View Post

well i knew that it doesn't matter

as long as it covers the frequencies you need it to cover, who cares if you call it a speaker or subwoofer or mbm



I guess what you call things does matter. I now use the J_Palmer_Cass MBM configuration.





Quote:
Originally Posted by otk View Post


i also think people think a ruler flat chart is the be all end all of good sound

it is a goal but not if you have to sacrifice other more important sound qualities to achieve it

if being flat is all that matters than all you need is a set of bose speakers and Audyssey

there's a reason why people don't care for what Audyssey does to the sound and it's not because they don't know what "accurate" or "good" sound is



You want to measure flat within reason. If you do not make measurements, you are flying blind. You never know what frequencies to work on nor if you did anything useful with your system changes.

Flat may or may not sound good considering that you measure the room and the speakers at the same time. You also measure speaker to speaker interaction when you measure multiple speakers at the same time.

I tend to use FR measurements to look for big problems rather than the smaller jaggies in the FR curve. A house curve sounds good to my ears considering the fact that I do not play back movies at "reference level".

The only thing that I am doing is filling in some of the major dips in my FR. You can not do that with EQ. Room treatments are not a cure either.
post #1893 of 2011
Quote:
Originally Posted by J_Palmer_Cass View Post

I concede. As Geddes has stated, what I am doing has nothing to do with what he has recommended that anyone should do.


I use the J_Palmer_Cass MBM configuration.

get yourself a 'TM' symbol and you're in business!
post #1894 of 2011
Quote:
Originally Posted by J_Palmer_Cass View Post

I concede. As Geddes has stated, what I am doing has nothing to do with what he has recommended that anyone should do.

Could you explain what you did different??
post #1895 of 2011
Quote:
Originally Posted by penngray View Post

Could you explain what you did different??



Geddes can't even explain what he is doing clearly, so I can't explain the difference. Geddes said that what I am doing is nothing like what he is doing, so we just have to take his word for it. Now if Geddes ever figures out how to explain what he is doing, he may be on to something!
post #1896 of 2011
Quote:
Originally Posted by J_Palmer_Cass View Post

Geddes can't even explain what he is doing clearly, so I can't explain the difference. Geddes said that what I am doing is nothing like what he is doing, so we just have to take his word for it. Now if Geddes ever figures out how to explain what he is doing, he may be on to something!

i know, it's all very ambiguous
post #1897 of 2011
Quote:
Originally Posted by J_Palmer_Cass View Post

Geddes can't even explain what he is doing clearly, so I can't explain the difference. Geddes said that what I am doing is nothing like what he is doing, so we just have to take his word for it. Now if Geddes ever figures out how to explain what he is doing, he may be on to something!

Got it!
post #1898 of 2011
Group,

Just a quick thought...

Multiple subs in a horizontal array w/an odd number of drivers (3,5,7, etc) could be arranged to mimic the behavior of a synthetic aperature radiator.

The center driver would be the only full range sub (0Hz-100Hz, for example) The next sub on either side would be lowpassed at a lower freq depending on the spacing. The remaining tilt of the frequency response could be flattened by minimum phase filtering and...voila!...constant directivity limited only by the width of the array.

The advantage of this is the elimination of interferometric nulls within a wide seating area.

This does not consider reinforcement due to room modes, but allows for constant power excitation of the environment.

Thoughts, comments...

rob r. (zzzzzzzz)
post #1899 of 2011
Quote:
Originally Posted by J_Palmer_Cass View Post

Geddes can't even explain what he is doing clearly, so I can't explain the difference. Geddes said that what I am doing is nothing like what he is doing, so we just have to take his word for it. Now if Geddes ever figures out how to explain what he is doing, he may be on to something!

lol. that's a little over the top, but there is an element of truth to it, which makes for good comedy.
post #1900 of 2011
Quote:
Originally Posted by rob r. View Post

Group,

Just a quick thought...

Multiple subs in a horizontal array w/an odd number of drivers (3,5,7, etc) could be arranged to mimic the behavior of a synthetic aperature radiator.

The center driver would be the only full range sub (0Hz-100Hz, for example) The next sub on either side would be lowpassed at a lower freq depending on the spacing. The remaining tilt of the frequency response could be flattened by minimum phase filtering and...voila!...constant directivity limited only by the width of the array.

The advantage of this is the elimination of interferometric nulls within a wide seating area.

This does not consider reinforcement due to room modes, but allows for constant power excitation of the environment.

Thoughts, comments...

rob r. (zzzzzzzz)


No need to limit this to odd-order arrays at low frequencies.
post #1901 of 2011
Quote:
Originally Posted by jj_0001 View Post

No need to limit this to odd-order arrays at low frequencies.

True. Sub spacing is more forgiving than tweeter spacing.

rob r. (array awaaaaaay )
post #1902 of 2011
After living with the JPC MBM for a while, I like it. The room length modes are being dealt with with this setup. Test tones are clearer. Music sounds "better" in that things like bass guitar notes are all there at near equal levels.

I also added one more passive subwoofer stacked in the right front corner of the room for a total of three subwoofer drivers for the ULF subwoofer. This makes a vertical array of 3 subwoofers that goes from the floor to above the mid point of the room height. This helps clean up the bass a bit also. The height modes are being worked with this setup. A little extra help with bass output capability does not hurt either. Geddes mentioned something about locating one of his "inexpensive" subwoofers midway to the room height or higher.

I also tried to HP my main speakers at 50 Hz, but something was missing when I did that. The main speakers seem to support sub 30 Hz bass in the room when they are run as large. That was a Geddes requirement, and there is a reason for the main speakers to be run as large. I will have to look into that issue a more depth when I have the time. I will have to review Bosso's postings also.

I may make some more measurements, but everything sounds good with the present setup. I may even post the final measurements here!
post #1903 of 2011
I haven't really followed this thread since it's inception, but i do have a similiar system in the works and some questions in regards to what others are experiencing. Take a pair of sealed mains capable of an F3 of 60hz. The original thought was to HP them at 125hz and run stereo MBMs 125hz down. I get the feeling i'm better off running the mains full range over the MBMs....am i correct in my assumption?
post #1904 of 2011
Quote:
Originally Posted by mayhem13 View Post

I haven't really followed this thread since it's inception, but i do have a similiar system in the works and some questions in regards to what others are experiencing. Take a pair of sealed mains capable of an F3 of 60hz. The original thought was to HP them at 125hz and run stereo MBMs 125hz down. I get the feeling i'm better off running the mains full range over the MBMs....am i correct in my assumption?

I would run them full range.
post #1905 of 2011
Thanx. It will be easier to acoomplish as well with an AVR with Pre-outs.
post #1906 of 2011
Quote:
Originally Posted by mayhem13 View Post

I haven't really followed this thread since it's inception, but i do have a similiar system in the works and some questions in regards to what others are experiencing. Take a pair of sealed mains capable of an F3 of 60hz.

Quote:
Originally Posted by gedlee View Post

I would run them full range.

Why???

With mains that only go to an F3 of 60 Hz, if you run them "Full Range", you essentially lose everything below that. If you re-direct that low bass to the sub(s), you don't lose it.

I could see a "Large + Subwoofer" or "Subwoofer + Mains" setting as this would send a full range signal to the mains while still redirecting the bass below the crossover point to the sub(s). However a "Full Range" setting alone seems to waste the signal in the 60 Hz and down range.

Quote:
Originally Posted by mayhem13 View Post

The original thought was to HP them at 125hz and run stereo MBMs 125hz down. I get the feeling i'm better off running the mains full range over the MBMs....am i correct in my assumption?

If the MBM's have more/better output than the mains in this frequency range, (very likely), then using them would be better. OTOH, if the mains have more/better output in this range, (highly doubtful), then you would be better off using them.

The other issue is placement. If the mains can't be placed where they provide the best bass response, (due to considerations for optimization of soundstage and imaging), then a set of independently place-able MBM's would be a much better solution, (at least IMO.)

Craig
post #1907 of 2011
Quote:
Originally Posted by J_Palmer_Cass View Post

Just as a follow up, the best sounding setup that I have tried consists of adding a single speaker HP filtered at 50 Hz and LP filtered around 160 Hz or so (upper limit of the external subwoofer amplifier LP). The subwoofer amplifier is connected to the R & L preamp outputs with no time delay. The "Geddes" speaker is located near the listening area, to the side and a bit to the rear. The overlap method is being used.

The speaker that is being used is a typical 2-way speaker that matches my other speakers. F-3 of 60 Hz, single 6 1/2" driver with tweeter. I had to change from a subwoofer to a smaller speaker due to sound quality and interference between the front bass and the "Geddes" deep in room subwoofer.

The trick is you just want to "fill in" a bit in the mid and upper bass with the "Geddes" speaker without creating too much deep bass that will mess up the front bass. The 60 Hz f-3 of the speaker plus the 50 Hz HP filter keeps the sub 50 Hz bass interference free with the use of the "Geddes" speaker. The sound levels used are not that high, but you can hear a difference in the mid and upper bass.

I am still evaluating the setup, but I don't think that my system has ever sounded better than it does right now!

I was considering acquiring an additional subwoofer or two, and trying the multi-sub approach. The ULF sub in the front R corner. The first additional wideband sub would go along the middle of the rear wall, and the 2nd one on the L side wall, as a starting point.

But this post got me thinking. I already have a speaker on the side wall, above the center line, that can reproduce down to 50 Hz. It's my Ls speaker. And I have another pair of them on the rear wall, which can be driven in tandem (if that helps them to act like a speaker at midwall ??). It may not be ideal, but it's free to use one, or all four of these speakers for bass distribution, so I figure why not give them a try.

To derive the signals to feed them, I happen to have an electronic crossover on hand--again--no cost to put into this trial. The overall bass management plan is in the figure. Just as with real subs, I can adjust the LP filter and gain from each speaker, and I can also adjust time delay and even the HP filter as well, and the slopes of the crossover filters from 1, 2 ,3, 4, or 5th order, if need be. The unit has 4 independent outputs, so each can be tailored differently.

The ULF sub is covering 20 Hz to 50 Hz, the main L/R get the sub's HP output above 50 Hz. The L/R signals feeding the 2-ch crossover are summed to mono so all 4 filtered outputs contain the same content mix, which is the bass from every channel (incl LFE) nominally covering 50-150 Hz.

My HT room is a few weeks away from completion, so I cannot try it yet, but will do so. If it doesn't work, I may have to obtain separate subs after all, but I thought I'd try the most practical solution first. Even if I go for real subs, I may keep the crossover in the plan, as it gives me more flexibility than normal sub controls. For illustration purposes, assume all the resistors are 10k.
post #1908 of 2011
wow, long thread, pardon me if I've missed some info, but what type of SPL does Dr.Geddes achieve in his room? Also, what is he achieving below 25hz?
post #1909 of 2011
Quote:
Originally Posted by dlfromcanada View Post

wow, long thread, pardon me if I've missed some info, but what type of SPL does Dr.Geddes achieve in his room? Also, what is he achieving below 25hz?

He did not care about below 25Hz for the longest time but recently there has been some discussion about the importants of sub 25Hz performance, thats atleast my opinion on that topic.

His SPL is HUGE and undistorted, his Summas are pro style designs that reach very high SPLs without distortion and the are constant directive designs same FR around the whole axis probably up to 60 degrees or greater meaning HUGE sound stage, larger then any speakers talked about in this forum.

Its different then having speakers that just go loud (with distortion and no constant directivity).
post #1910 of 2011
SPL from subs only?

What I'm getting from this thread is that his approach produces an overall smooth response and overall great sound, is cost effective, but lacks the serious SPL and extension that only larger subs can produce.

So if you like SPL and LFE, what does this setup do for you? Do you simply use three highpowered giant subs, or just add an additional megasub to his type of setup?
post #1911 of 2011
Quote:
Originally Posted by dlfromcanada View Post

SPL from subs only?

What I'm getting from this thread is that his approach produces an overall smooth response and overall great sound, is cost effective, but lacks the serious SPL and extension that only larger subs can produce.

So if you like SPL and LFE, what does this setup do for you? Do you simply use three highpowered giant subs, or just add an additional megasub to his type of setup?

If the subs are mixed to be about flat to the mains and the mains can go so loud as to be painful without the subs clipping, then its pretty much irrelavent what the subs alone output is. Its probaly higher than the mains, but it could be lower too. All I know is that I am not about to test it that high as I wouldn't want to be in the room with or without hear protection.

My system does go flat to about 20 Hz. from my measurements, but that's probably coincidence due to the extremely well sealed room and the modal gain at these frequecies. I don't target these frequencies - the room sets the LF capability and usually the room is what it is.

I don't understand how you could have arrived at "but lacks the serious SPL and extension that only larger subs can produce" from the discussion here. I never talk about this aspect because, as I said, it will get louder than anyone could or should withstand. Quite honestly, I find the "SPL War Games" laughable. The LFs need not be able to produce any more SPL than the mids or highs - why should they? If this is all above the "threshold of pain" then its simply a numbers game with no relavence to anything.
post #1912 of 2011
Quote:
Originally Posted by dlfromcanada View Post

SPL from subs only?

What I'm getting from this thread is that his approach produces an overall smooth response and overall great sound, is cost effective, but lacks the serious SPL and extension that only larger subs can produce.

So if you like SPL and LFE, what does this setup do for you? Do you simply use three highpowered giant subs, or just add an additional megasub to his type of setup?

We went down this path in this thread.

Geddes makes a valid point about SPL....you have to ask yourself what your main tweeters can do? 120dB max? probably 115dBs.

Multiple small subs can do serious SPL I have 4 SC-8s and its louder then I ever want in my room when I tested them so the goal here isnt maximum SPL its maximum in room response at common sense SPL levels.

Of course I require some serious drivers/power because I want 10Hz but that is outside of the objectives in this thread.
post #1913 of 2011
Quote:
Originally Posted by penngray View Post

We went down this path in this thread.

Geddes makes a valid point about SPL....you have to ask yourself what your main tweeters can do? 120dB max? probably 115dBs.

Unless you are using compression drivers, this is seriously optimistic - maybe 105-110 dB SPL?. At the levels that you quoted the voice coil may not burn out, but any direct radiating tweeter is going to be compressing and distorting heavily. Its achievable, but not listenable. The one overwhelming comment that I get about my speakers is how well they handle high SPLs. Thats because the tweeters CAN produce 115-120 dB SPL without loosing it completely - thermally and linearly.
post #1914 of 2011
Quote:
Originally Posted by Craig John View Post

With mains that only go to an F3 of 60 Hz, if you run them "Full Range", you essentially lose everything below that. If you re-direct that low bass to the sub(s), you don't lose it.

The above would be true if all main channels had extreme bass information recorded at all times, in all films. But the thing is, that isn't the case, at all times, with all films. At best, it's a great deal of films, a great deal of the time so it's more of a quasi-certainty rather than an absolute certain statement that you've made above. See where I'm going with this ?

Me neither. You'll only 'lose' stuff if that stuff was recorded and if it's not recorded then you don't 'lose' it. I know, circular but, well, it's true. For all you know, there wasn't much bass recorded in the front channels in the first place in a handful of films. Just because all main channels have full bandwidth extension to what, like 3 Hz, doesn't necessarily mean that the mixing engineer will always exploit that bandwidth and put such information there to be expoited.

FYI : yeah, I know, in most cases, you're right, so I'm just being a facetious ass (if there is such a thing). But there are cases where I'm right so I suppose I'm not such an ass but more of a pedantic prick. I also could have compressed my post into a single line and it would have carried all the meaning and significance that I wanted it to convey. Oh well, maybe next time.

Regards,
post #1915 of 2011
Quote:


All I know is that I am not about to test it that high as I wouldn't want to be in the room with or without hear protection.All I know is that I am not about to test it that high as I wouldn't want to be in the room with or without hear protection.

FYI, sub frequencies generally don't cause hearing damage. Our ears are wonderful devices Earl. They happen to be less sensitive to longer wavelengths. Not more but less. 115 dB's at 40 Hz or 50 Hz is not going to cause hearing damage.

Quote:


The LFs need not be able to produce any more SPL than the mids or highs - why should they?

For a few reasons. Probably 10 reasons and all of them happen to be identical reasons. The reason ? Because LFE equals 'big bass headroom advantages' and mixing engineers tend to exploit those advantages.

If the bass should produce no more or less than the mids, then perhaps we should alter the LFE track by 10 dB's less in the AV receiver menu (although I'm sure J_Palmer_Cass's top secret AVR can 'sense' which movie has what LFE recorded and can compensate accordingly to match an even level with the mids and high's)

Just a thought.

Regards,
post #1916 of 2011
Quote:
Originally Posted by goneten View Post

If the bass should produce no more or less than the mids, then perhaps we should alter the LFE track by 10 dB's less in the AV receiver menu (although I'm sure J_Palmer_Cass's top secret AVR can 'sense' which movie has what LFE recorded and can compensate accordingly to match an even level with the mids and high's)

The 10dB advantage in the LFE channel is not there to give bass any particular advantage over the rest of the spectrum, but to enable it merely to keep up with the 3 screen channels, which gives a cumulative advantage of roughly 10 dB when operating together.
post #1917 of 2011
Quote:
Originally Posted by Roger Dressler View Post

The 10dB advantage in the LFE channel is not there to give bass any particular advantage over the rest of the spectrum, but to enable it merely to keep up with the 3 screen channels, which gives a cumulative advantage of roughly 10 dB when operating together.

Which equates to increased headroom. If a subwoofer is required to put out 121 dB's maximum output at reference level when speakers are set to 'small' (including LFE track) then the sub must comply otherwise it will compress the sound. Otherwise 115 dB's if speakers are set to 'large'. Or more if one sets their subwoofers hot.

But like I said, let's rather just reduce the LFE level by 10 dB's, destroy our dynamic range so that the mid's and high frequencies's remain at a closer level since bass should never be out of proportion between those two even though, you know, if one calibrates their systems flat and equalizes their room response flat, the bass will still overpower when called for it because the mixing engineer would decide how much or how little bass will be required, at what level and frequency. He ultimately will exploit the headroom available within each main channel as he sees fit.

Let's turn our bass levels down by 5 dB's relative to all main channels as well as turning the LFE level down 10 dB's then, and only then, should the bass and mid-range and high frequencies be at similar enough levels.

I'm joking about this, I hope you know that.

Regards,
post #1918 of 2011
Quote:
Originally Posted by Roger Dressler View Post

I was considering acquiring an additional subwoofer or two, and trying the multi-sub approach. The ULF sub in the front R corner. The first additional wideband sub would go along the middle of the rear wall, and the 2nd one on the L side wall, as a starting point.

But this post got me thinking. I already have a speaker on the side wall, above the center line, that can reproduce down to 50 Hz. It's my Ls speaker. And I have another pair of them on the rear wall, which can be driven in tandem (if that helps them to act like a speaker at midwall ??). It may not be ideal, but it's free to use one, or all four of these speakers for bass distribution, so I figure why not give them a try.

To derive the signals to feed them, I happen to have an electronic crossover on hand--again--no cost to put into this trial. The overall bass management plan is in the figure. Just as with real subs, I can adjust the LP filter and gain from each speaker, and I can also adjust time delay and even the HP filter as well, and the slopes of the crossover filters from 1, 2 ,3, 4, or 5th order, if need be. The unit has 4 independent outputs, so each can be tailored differently.

The ULF sub is covering 20 Hz to 50 Hz, the main L/R get the sub's HP output above 50 Hz. The L/R signals feeding the 2-ch crossover are summed to mono so all 4 filtered outputs contain the same content mix, which is the bass from every channel (incl LFE) nominally covering 50-150 Hz.

My HT room is a few weeks away from completion, so I cannot try it yet, but will do so. If it doesn't work, I may have to obtain separate subs after all, but I thought I'd try the most practical solution first. Even if I go for real subs, I may keep the crossover in the plan, as it gives me more flexibility than normal sub controls. For illustration purposes, assume all the resistors are 10k.



Roger, that setup should work and is very flexible. I would experiment with stereo bass instead of the sum to mono R & L mix even though the RB and LFE will still be mono. I like to listen to 2 channel music, and the stereo BP filtered bass in the L & R surround speakers may work out better than what I use.


Our basic setups are similar. My setup (5.1) uses that same L, S, S no SW BM scheme. My ULF subwoofer(s) are in the front right corner and are LP filtered at a nominal 50 Hz. My ULF subwoofer and JPC MBM signal source is taken from the R & L preamp output. However, I do not HP filter my R & L main speakers.


I am using a receiver, so I use a more basic scheme for the JPC MBM. I simply use an external NHT X-1 subwoofer crossover with the input connected to the receiver's R & L preamp output. The crossover's LP is set to a nominal 50 Hz and feeds the ULF subwoofer(s) amplifier. The crossover's HP filter can be set to 50, 80 or 120 Hz. The crossover's HP output (set to 80 Hz HP) feeds a standard external subwoofer amplifier that is connected to a single JPC MBM (LP all the way up = about 160 Hz).


I have three subwoofers stacked in the right front corner, with the uppermost subwoofer driver placed at ear level when seated. The JPC MBM is pretty much just below ear level when seated, and is located nearfield beside the listening area. The volume level for the JPC MBM is easily fine tuned by ear, but is initially set by RTA.


As far as the use of additional in room subwoofers are concerned, they caused me nothing but trouble during my experiments. I found that I did not need the output capability nor the bass extension of a real subwoofer for use of the speaker as an overlap MBM.
post #1919 of 2011
Quote:
Originally Posted by J_Palmer_Cass View Post

I have three subwoofers stacked in the right front corner, with the uppermost subwoofer driver placed at ear level when seated.

Have you tried bolting a subwoofer on the back wall at ear level height ? Rumor has it that it will cancel all even order modes across that section but it needs to be at ear level height.

I think the future is ear level positioned subwoofers all across the ceiling and wall-ceiling junctures. That would be amazing. Confuse the hell out of those comb-filter buggers so that they won't know what hit 'em. I'll try it out and then let you know what I think.

I've got a spare subwoofer, I think I'm going to suspend it at ear level height behind my head to see if it eradicates a null of 20 dB's. I'll report back soon.

Regards,
post #1920 of 2011
Quote:
Originally Posted by goneten View Post


If the bass should produce no more or less than the mids, then perhaps we should alter the LFE track by 10 dB's less in the AV receiver menu (although I'm sure J_Palmer_Cass's top secret AVR can 'sense' which movie has what LFE recorded and can compensate accordingly to match an even level with the mids and high's)

Just a thought.

Regards,



Roger uses the same BM configuration that I do. There is nothing magical about my receiver's BM.
New Posts  All Forums:Forum Nav:
  Return Home
AVS › AVS Forum › Audio › Subwoofers, Bass, and Transducers › Are three inexpensive subs better than one expensive sub-Dr. Earl Geddes Approach