Two subwoofers in smallish HT room?

Eldartford

I guess I'll just agree to disagree then...my findings are very different than yours. I would hate to be standing in the room when those 20hz booms take place though...should take no more than 100,000 watts or so to blow the windows and bring down the roof!!!

Dave

Sogood51...It was a surprise to me, but I measured about 4.5 watts rms into each of my three SW system, a total of less than 15 watts, to shake the windows in my listening room, using a warble test signal around 30 Hz. The assumption that LF takes a lot of power does not stand up to objective measurement. My CarverPro ZR1600 amps drive a woofer system with one side and a MG1.6 with the other, and if I crank up the volume I can make the MG1.6 side clip (LED indicator) while the SW side is still loafing. Hard to believe, but that's the fact.

You might want to check Rives website and study up on room resonance. (Maybe buy his gadget also).

Eldartford

I also run three subs, your measurements go right along with my findings. My Onkyo M-504 sub amp has large power meters and confirm that very little power is needed to shake my 4,800 cubic ft. room on it's cement slab floor.

I do indeed have all the tools to measure my room in 1db increments and am very lucky that it measures very smooth over-all with no large peaks/dips down to 17hz...I did build the room as a " room with-in a room"... with my sons help.

I guess where we differ is in how we define "Boom". I was born in 1950 so remember sonic boom before it was outlawed over our homes. You can get a 100hz freq to boom within a room...20hz?...naaah, it would take a huge amount of power.

I guess the other place we differ is on how X-over effects room modes. I have done hundreds of tests using many configurations...over-all measurements as a complete system (speakers+sub) can change drasticly with only a change of x-over settings.

At this time my front subs are 25 ft apart and located at around the ceiling/floor null-point, (Supertowers are upside down) and in the corners in other words. What do you think Rives would think of that!...gotta love those measurements and go with what works after all.

Dave

Sogood51...I am now set up with a crossover where I can alter the SW X/O frequency while music is playing by twisting a knob, and my ears and my spectrum analyser tells me what happens.

With a white noise test signal (flat 20-20KHz) I am able to vary the X/O frequency from 50 to almost 200 Hz with no audible or visible spectral change to the sound. This tells me that I have got the SW well matched to the mains. With music, I sometimes vary the X/O frequency.
With "heavy" sound, like organ, choral, or some orchestral, the six big cone drivers in the subs work better than the Maggies, and I crank it up to about 150.

My room resonates at about 60 hz. Always has with any speakers. Rives uses 70 Hz as his example on the web site. If you are lucky enough to have a larger room it will be lower.

Eldartford

Our systems are somewhat similar...planers, three subs with six large drivers. I suspect the difference that I measure and you don't are related to X-over and mains settings.

Sounds like you run the Maggies full-range thus always the same at their location with the only change being at the subs location.

I use fixed points which changes output freq levels at both locations having greater effect on measurement..at least in my findings.

My Duetta Sig's have an in-room rise of 2db at 30hz and then a roll-off to 25hz...the lowest setting on my X-over is 35hz and the blend between the mains (run full-range) with 35hz X-over to the sub is a little much in my room...a new X-over {maybe one of the digitals) with more choice of filter would probably benefit.

At this point, I x-over at 50hz with 6db slope.

Well, I guess I have gone far off topic...sorry

Dave