Geddes multiple subwoofer method - 3 subs vice 4

Dear @phusis : Velodyne ( at least my HGS, not the DD models with Kevlar driver. ) were made for MUSIC sound reproduction systems and not HT where needs are different and especially on SPL.

The Velodyne aceleromete/servo ( patented. ) avoid that THD can goes over 0.5% and when it’s approaching that figure power gone lower but not the bass frequency.

I never had a problem with my HGS and maybe because my main speakers has 95db efficiency but I measured at my seat position ( near field. ) 97db SPL with peacks at around 105db and the bass range is fabolous.

I readed other reviews on the DD models where what you read it did not happens but at the ned the critical subject is to mantain ( for listen MUSIC not HT. ) the THD at minimum in the bass frequency range. This is the why of my post more than about thisor that sub.

In your link review we can read this ( HT ):

" 

Batman Begins followed by the Dark Knight, both of which offer not only a very powerful and engaging audio track but also are enjoyable movies to watch. The master volume was set to -15 for the entirety of both films.

Throughout the various action and dramatic sequences of the films the DD18+ provided a stellar performance. Subtle background bass undertones were just that and when demanded the DD18+ provided a lot of power and room shake. On sections that contained deeply extended bass the DD18+ had generous extension that provided an extra feel or size to the sound that lesser subwoofers simply do not. As previously discussed the performance of the DD18+ as far as definition and ability to track notes is excellent. If there was any small caveat to the DD18+ performance it might be that it was not quite as sharply dynamic on a few parts as I recall they can be, the tumbler chase scene being one example, the gatling gun test, bankers shotgun blasts and the hospital explosion being others. My large listening room acoustics are such that it is very difficult for a single subwoofer, even a very capable and powerful one such as the DD18+, to handle alone so perhaps the DD18+ was being limited a little on a few extremely loud sections. Audio memory is a hazy thing at best so I can’t be sure and to be quite honest I’m stretching to find even that small caveat with the DD18+’s audible signature. It is that good. What I can be sure of is that the DD18+ always sounded composed throughout and easily produced one of the top performances that I have experienced from a single subwoofer in my room. Very deep bass was presented with apparent ease and fundamental tones or pitches of bass transients were spot on.  "

Not so bad as those measurements and the reviewer seats one DD-18 at 4 meters from his seat position, not near field.

R.

@phusis :  " Looking at the CEA-2010 maximum peak output of the DD18+ puts it in the upper middle range of all subwoofers ever tested and near the top of all sealed subwoofers. It produces output easily in excess of 110dB over the critical music range and offers impressive deep bass output as well mustering over 103dB at 20Hz and almost 99dB at 16Hz which is impressive for a sealed subwoofer. The DD18+ CEA-2010 output is amplifier limited above 20Hz and was distortion limited at and below that point. The DD18+ is the first commercial subwoofer that I have ever evaluated that was able to produce a CEA-2010 passing result at 10Hz. 86.1dB may not seem like much but any passing result at the 10 and 12.5Hz bands denotes rather prodigious deep bass output capabilities due to the amount of displacement involved to produce any meaningful output that low in frequency, not to mention that distortion must be under some amount of control as well. If distortion is ignored completely the DD18+ can almost muster 90dB at 10Hz. "

R.

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 :

AVAA C20 - Active Bass Trap - PSI Audio

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.

In the other side and about the ported loudspeaker still today is what almost all top manufacturers use it and the customers jut buy because there are not to many sealed/acoustic suspension speaker alternatives. Even Wilson uses ported.

For subwoofers I totally agree: must be sealed not ported.

R.

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.