Geddes multiple subwoofer method - 3 subs vice 4

Another important factor that was mentioned was room treatments for bass do not work. It is a total waste of money which could have been spent on another subwoofer or a better crossover. 

Not true...depends on what you get...I use 8 of the acoustic fields ACDA panels...250 lbs each, 16 inches deep (a bear to handle, obviously need a larger room to handle this stuff)...takes care of business clean down to 30 hz.

 

 

@erik_squires I have no idea in this day and age why someone would use a ported loudspeaker

Agreed, I recently got a pair of the 18 inch sealed Rythmiks, replacing 2 of my F12G for certain types of music..visceral soul churning slam fest down to an octave below 20 hz, can't make this stuff up.

Dear @deep_333 : " " Not true...depends on what you get...I use 8 of the acoustic fields ACDA panels ....clean down to 30hz. ""

Problem with room treatment and especially in the bass range because its main importance is that " clean down to 30hz ". First question could be at which frequency starts to " clean " and if exist in room measurements of frequwency response with and with out those kind of panels. Always is important not only what we are avoiding with but what we are losting with, obviously always exist trade offs and depends of each one of us what kind of trade off we are ready to take. Other alternative is something as the C20 electronic bass trap that operates between 15hz to 150hz :

I don’t have a dedicated room/system and when I had professional room treatments ( several kind of through the years. ) I really never been totally satisfied with. At random with the stuff in my parlor as wool carpets and the kind of the parlor furniture and treatment diffusors and curtains and mainly to the subs position I’m lucy enough to stay really satisfied as ever with no apparent troubles in all the room/system frequency range quality level reproduction at diffrent S¨PLs and different kind of MUSIC.

There are all kinds of guys making things too confused on different threads...

- Basic physics - standing waves/peaks/nulls occur between 2 parallel walls...Ya "effectively" absorb on those 2 parallel walls just as it pertains to your listening position to mitigate it....and leave the rest of the walls alone for absorption (i.e., don't suck the life out of/kill the room). Get the Harman room mode calc and plot your room modes, for starters. I am not concerned about what happens anywhere else in the room, no corner crap nothing.... I am only concerned about my main listening position. For example, It's a li'l strange to me when i see guys put a bunch of crap in the corners and all over the place as if they are hanging around/dancing around in a corner. I "effectively" absorb down to 30 hz with my  ACDA panels on the front wall, back wall, left wall, right wall for my primary listening position (modes check, sbir check). Yes, they are 16 inches thick and weigh 220lbs each for a reason. I use a couple of different lighter panels on the ceiling for the same purpose and to take care of some floor/ceiling bounce issues.

- That's it...no more absorption...Everything else i use is diffusion (first reflection, ipsilateral, contra, etc, whatever to boost perceived resolution, detail, spaciousness and so on for the listening position)

- I don't usually put subs on the front stage for show...Refer to the harman paper - virtual sub principles, especially If restricted to 2 subs (very few people set up more subs than 2)  Reading the results of a room mode calculator will guide you more on placement for the same purpose. In fact, you can mitigate a certain amount of modal issues with multiple subwoofers, placement and phase adjustment (a bit trickier to do), except only up to the crossover point of the subs...For something higher, you would need absorption.

In short, follow the physics...and when you do, you may rejoice/float around in a uniform warm womb of bass....the core foundation for jawdropping sound.

 

My room is an inverted L with two parlors ( first smaller one ) in the second and main parlor is where the speakers/subs are seated in front of my listening position.

@rauliruegas , An L shaped room makes things a bit more complicated on the sim domain. Talk to an integrator. It is hard to write technical essays on a thread. Nevertheless, the harman room mode calc will still work between any 2 parallel walls in that room.

Google harman room mode calculator. You would enter your room dimensions to determine where the hell all the strongest nulls/peaks are. The results would look like this....

 

Here’s another way to visualize it....(top view, scratch rough sketch)....Also how you deal with nulls and peaks. Goofy bass is all a guy hears unless he does stuff like this. (Basic Physics - Standing waves/nulls/peaks occur between parallel walls). This again shows you the advantage of larger rooms. The smaller the room, the harder it gets to deal with this.

 

Here’s some expansion on what i was trying to describe with the Harman virtual sub principles. By strategic placement of subs, you can get rid of many of the strongest peaks/nulls upto the sub’s crossover frequency. For nulls/peaks occurring at frequencies higher than the sub’s crossover, you have no other choice but absorption.

In short, you can use subwoofers to REMOVE nulls/peaks. It is not just for giving some oomph on the low end for a flaccid speaker.

 

 

If you had 4 subs, this is how you would place them and phase adjust them to get rid of the maximum number of the strong nulls/peaks in light of the above mentioned principle (up to the sub’s crossover point).

sub 1: 1/4 lengthwise, 1/4 widthwise position

sub 2: 1/4 lengthwise, 3/4 widthwise position

sub 3: 3/4 lengthwise, 1/4 widthwise position

sub 4: 3/4 lengthwise, 3/4 widthwise position.

 

If you only have 2 subs,

sub 1: 1/4 lengthwise, 1/4 widthwise position

sub 2: 3/4 lengthwise, 3/4 widthwise position.

 

Same principle works for the room’s heightwise modes. You ever heard of guys lifting subwoofers off the floor to the heightwise modal points? That is the reason and the physics behind it.

The idea is to tackle the max number of strong nulls/peaks with sub placement...and then use absorption to deal with the rest (modal nulls/peaks/frequencies higher than the sub’s crossover). It is also a very very good idea to get subwoofers with a variable phase knob (not just a 0/180 phase switch). Rythmik is a good example of subwoofer brands that give you a variable phase knob.

 

Everything else should be diffusion so you don’t kill the room with absorption all over the place. Focus only on the main listening position.

Hope that helps you...and some of the other confused guys here...

 

 

 

 

Dear @deep_333 : My room geometry is not easy to use the Harman calculator, these are more or less the dimensions/shapes:

as I posted my apartment has 2 parlors from the entrance door. First parlor where is not seated the system its wall distance to the other extreme, where is the second parlor/listening area/system, are 9.70m to the window that’s behind the speakers.

Now the speakers are at 95cm. in front of the windows and the left speaker is at 30cm. from the side wall, the rigth wall is at 8.5m from the left one.

The center of the speaker tweeters in between are at 2.60m and the speaker woofers at 3.05m.

Listening area length is 4.70m and the wide is around 4.5m. Exist a passageway of 1m. wide by 14+m. in length. This apartment has 3 bedrooms and two complete bathrooms. All in one floor, so is a little big.

Dining room is big and the dining room central/rectangular table is for 10 seated people.

Both parlors are full of ( mainly ) wood furniture as the dining room and all around exist wood display cabinet ( like seven of them ). The parlor furniture are made from natural absorbtion materials and due to the shape of the wood furniture it works as difussors.

Rigth now the system is working truly fine and till today I think that I can’t do ( ? ) anything to improve its very high quality MUSIC reproduction and very high resolution.

It does not matters the SPLs the room/system just refuse to distort: MUSIC stage always is there/nothing change but SPL. Yes, its noise floor and distortions levels are so low that can be dangerous to the ears with out taking in count due that we can’t be aware of those distortion levels. No, I normally listen at around 82 or even a little lower db SPL and only during some kind of system audio items tests I listen at 95db with peacks at 105+db for only a few minutes.

@rauliruegas 

I'm having difficulty visualizing this with the written description. Do you have a top view sketch/schematic with distances, etc (that you can post here)? "Picture says a thousand words", Confucius said.

 

I’ve found them too "hot" sounding over longer durations in being more forward and incisive in their sonic nature than my own system. To by fair, in many ways the 4367’s are delightful speakers; exhilarating, energetic, honest, clean, extremely informative (I’d say a wee bit too "insisting") and - apart from the low octave shifting towards a warmer imprinting - fairly coherent.

The thing is though, to my ears and sensibilities they simply become too much over time, and moreover I find string instruments like violins to have a slightly "plastic"-like and/or nasal character to them (I prefer the M2’s and 4349’s here with their flatter waveguide), which is a dealbreaker to me. My EV main speakers by comparison with their large format horns + subs are sonically more akin to large panel speakers; more relaxed, less "beamy," fuller and more visceral/physical/dense. Where it becomes apparent they’re a larger package overall, apart from their more natural height of presentation, is at higher SPL’s (not least with movies) where the sheer unadulterated force and power is at full display.

 

...know about that "plastic’y" sound all too well and it goes all the way up to their top end line. The measurement heavy JBL/Harman PhDs don’t seem to care too much, as long as it measures great! They may need to put their big egos down and learn a thing or two from the likes of Borresen, Yamaha, TAD, etc.

What horn subwoofers do you use? DIY? or something else? I might be interested in getting one.

@deep_333 wrote:

What horn subwoofers do you use? DIY? or something else? I might be interested in getting one.

They’re the tapped horn principle, DIY and called MicroWrecker (a sibling to the LilWrecker tapped horn, which has a 5Hz lower tune for a 50% addition in volume (30cf.) and ~3-4dB hit in sensitivity). I got the plans over at AVS Forum from a developer there, and had them built by a cabinet maker. The developer also simulated drivers for the specific design in the Akabak (or Hornresp) software, and so had a range of suitable woofer choices to go with. These have to have the proper electromechanical parameters within a fairly narrow window in a given tapped horn design for them to work the best here, which is to say to properly resonate the horn; too weak a motor and the horn isn’t "excited" enough, and too powerful a motor will compress the air too severely at the throat, also leading to insufficient horn resonation. The B&C 15TBX100 (8 ohm) unit I’m using sits right in the middle of the desired performance window here, and so is close to the ideal driver for the purpose. Close, because it lacks the very last bit of excursion range to be fully exploited at its rated power (1000W nominal power handling, 2 hour pink noise test, free air) before hitting Xmax in this design with a ~23Hz tune, but it’ll take 600W up until that point, so perhaps a theoretical 2dB SPL subtraction overall. Fine with me, as a single MW will still do over 120dB’s down to 25Hz with the B&C unit, and I have two of them - corner mounted. The same driver is used in Danley’s TH-115 subs, but being this tapped horn design has a higher tune the driver can be used at full power here.

Size of speakers doesn’t seem to scare you off, but be aware it’s still a 20cf. volume per cab. When you see them "in the flesh" it can a bit unsettling getting a feel for their true size, I know it was for me at first. In the same ballpark there’s also great designs by Josh Ricci over at Databass.com, notably the Skrams, Skhorns and Othorns. The latter is also a tapped horn, though built around the 21" B&C 21SW152 woofer - a beast - and with a ~28Hz tune. Initially I intended to have a pair of the Othorns built, but the woofers were out of stock for months, and so I opted for the MW’s. The Skrams are a great design as well, and more driver "friendly" than the Othorn. Meaning, a range of 21" pro woofers can be used here, whereas the Othorns are only fully pleased with named woofer or its IPAL equivalent.

The inspiration for the MW’s were Danley’s TH-50 tapped horn, and they’re very much alike in vital areas. Josh Ricci opted to develop the Gjallarhorn tapped horns instead (also inspired by the TH-50), which is built around TC Sounds LMS-Ultra 5400 driver (18"), but that driver is no longer built. A beast of a sub, and about the most one can squeeze out of an 18" woofer, I’m told. They’re tuned a bit lower than the MW’s, but I never truly considered them as they are too monstrously sized (plus more than 300 pounds w/driver) and a bit hampered in their upper range due to the slightly lower tune.

In any case any of the above designs are extremely capable in putting out high quality bass at prodigious SPL’s and low distortion levels - certainly compared to most any low eff. "hifi" subs out there.

@phusis , appreciate the info you provided....I have a couple of rooms in my basement for audio (no WAF issues), 1 for multichannel and the other room for stereo. Size of speakers and subs is not an issue (bigger the better).

I recently went up to a pair of the 18inch F18 Rythmik subs for my multichannel room, which go infrasonic, usable output down to 10hz, an entire octave below 20hz technically speaking...All you hear from the naysayers is.."There’s no content that hits that low or ya can’t hear that low", whatever. On the contrary, it’s flipping nuts, the impact these monster subs have on many tracks, that i have heard a thousand times. It’s a new phenomenon, lol....

It is also perhaps a motivation to try out something different in my stereo room....like a pair of large horn subs! My current open baffle GR subs that i have in the same room are good for what they are, but, it’s more for precision (not for the visceral maniac stuff). Have you heard of these Devastator horns? I ran into a couple of AVS threads with guys talking about it....

It looks like they get down to 19hz, comes with all the flatpacks, i.e. seems to be a more complete easier diy kit. I’d hate to stare at drawings and start cutting wood from scratch, not have it be too much of a time investment.