PB12 initial thoughts & decision

[lovinthehd]

To your point ShadyJ - I may be under the impression that 90w rms / ch receiver and RF-62II will give me similar kick drum SPL's as back in the day when I would go to electronic raves. And that is probably too much to expect without running external amps and more full range speakers with dual 8" or 10" woofers running at like 300 w rms.

I do have YPAO volume and Adaptive DRC enabled - both play with high and low frequency boosting when listening at low volume levels. It may be mucking up the works. I will try turning them off in addition to using Pure Direct and see if it gives me the desired effect.

Stay tuned and thanks for all the support - I clearly joined the right forum.

I'd particularly turn off the Adaptive DRC, at least I don't want dynamic range compression in play. YPAO Volume is more like a loudness contour and at lower volumes I would use that. YMMV.

 

[KahunaB14]

Appreciate the thoughts and responses. Here are some more things I learned.

1) Pure Direct only runs the RF-62II's (full signal range) and turns off the sub and center. I was actually quite surprised at how LOW the RF-62II's can go. (more on this later)

2) I played a variety of songs with pretty deep bass while toggling the sub on and off. For most songs I cannot tell which is which if I do it with my eyes closed.

3) Turning off DRC and YPAO volume didn't have much impact to my audiophyte ears.

4) Turning the front's to "full" with the sub set to "use" allows the sub to be on AT THE SAME TIME as the fronts. However I have no idea what the sub crossover is as there is no separate control for that. This may give me an opening to use a MBM.

5) Adding the Y splitter and re-calibrating told me the Y splitter is equivalent to a ~+5dB bump (the AVR had to compensate by going from -2.5dB to -7.5dB during re-calibration)

6) I used several frequency sweeps and constant frequency tones to test from 100Hz down to 15Hz. (I tried both with sub off (Front=large) and sub on (Front=crossed at 160Hz...so off for my testing). Note my sub gain knob was at ~45% and in AVR I have the gain on the sub turned up ~+4.5db from what YPAO set it at, while my mains are at 0dB, where YPAO set them.

My findings...

At 90 and 80Hz the RF-62II's had the CLEAR advantage in output. I also liked the tone of the RF-62II's better. They were more natural sounding to my ears. More like an instrument.

At 70Hz the tone advantage went slightly to the PB12 and the output advantage slightly to the RF-62II.

At 60Hz the output advantage CLEARLY went to the PB12, tossup on tone.

At 50Hz...and this is odd...they sound almost identical in output and tone...at multiple volume levels.

At 40Hz the output advantage went to the PB12, but not by THAT much. The tone was more "full" on the PB12 as well.

At 35Hz the output advantage went to the PB12...and the RF-62II's started soundy slighty choppy...like an aircraft prop instead of a smooth tone. As I turned the volume up the PB12 pulled away even further.

At 30Hz the output & tone advantage CLEARLY went to the PB12...shakes the house bigtime...but you can STILL hear the RF-62II's...theres just no power there and it sounds increasingly choppy.

At 25 and 20Hz there's almost nothing from the RF-62II's...the PB12 is shaking the house when turned up...my wife was saying it felt like an earthquake or a freight train rolling through.

At 15Hz the house shaking stops but you can still hear the PB12 moving some air. Nothing from the RF-62II's

At MOST frequencies with constant test tone I can hear 2 major nulls when walking around. So I should do a sub crawl...except there is only 1 place my wife will let me put the sub in our current home...so there is no point.

In summary the $500 PB12-NSD is nicely filling in the 20-60Hz region, while the $500/pair RF-62II's take care of everything from 60hz on up. I will cross at 60Hz.

My wife is wondering why I bought the sub since it cost the same as the mains but is only good from 20 to 60Hz.

My response: "Cause Earthquake"

 

[Irvrobinson]

It is impossible to know for sure without being there, but I suspect that some of what you're hearing are differences in room effects due to placement. If you can (and I realize that's tough with an HT set-up), you might try changing the placement of the RF-62IIs a bit. Sometimes 6" makes a significant difference.

The RF-62IIs do have surprising bass, down to about 32Hz in my room, which is smaller than yours at 16x14. Below 32Hz their response drops off like a rock, measured one meter from a speaker.

In my music system I use a sub with 5-band parametric equalization to do judicious fill-in for the mains (due to my speaker placement being optimized for imaging and midrange smoothness, not bass), and it works out great.

Glad to hear that you finally found something that sort-of works. Bass in residential rooms is tough to get perfect.

 

[KahunaB14]

The only lingering question that is nagging at me is this: How is a 400w rms 800w peak 12" ported giant of a sub that is supposedly super linear all the way to 200Hz being outclassed by a pair of 125w rms dual 6.5" woofer Klipschs being driven by a 90w rms AVR at ~70Hz & 80Hz? I may try pointing the sub woofer/vent out into the room and re-run YPAO. This doesn't make sense.

 

[shadyJ]

The only lingering question that is nagging at me is this: How is a 400w rms 800w peak 12" ported giant of a sub that is supposedly super linear all the way to 200Hz being outclassed by a pair of 125w rms dual 6.5" woofer Klipschs being driven by a 90w rms AVR at ~70Hz & 80Hz? I may try pointing the sub woofer/vent out into the room and re-run YPAO. This doesn't make sense.

It does make sense. The combined area of the cones of the Klipsch speakers do have more surface area than the SVS sub. But the Klipch drivers are probably far more sensitive and efficient in mid and upper bass frequencies. They have a lot less mass to move (less heavy cones and VC/former) have a much higher resonant frequency, so just a little wattage makes them go a long way in that frequency band. However that makes them unsuitable for deep bass frequencies that the SVS tackles. The SVS driver is going to be easier to push at deep frequencies where its resonant frequency lays, and also the resonant frequency of the cabinet/port.

 

[KahunaB14]

Thanks Shady - I should have just not been lazy and ran the calc on the cone surface area ... good points that make mechanical sense also on the mass...F=M*A more F needed for more M at constant A.

Am I correct in assuming that greater acceleration, at higher mass and surface area as well as natural frequency interactions are what is primarily responsible to achieve a higher dB SPL on a sub?

I also overlooked the fact that I'm only at at most 50% gain on the sub knob. The thing can do more than I am asking of it...it wasn't a scientific test after-all. Not even to mention room gain or nulls coming into play.

 

[Irvrobinson]

I also overlooked the fact that I'm only at at most 50% gain on the sub knob. The thing can do more than I am asking of it...

I would not make that assumption. You got one part right, the volume control on the sub should really be seen as a gain control. If the input signal is relatively high the sub could be nearing its driver or amplification limits even though its volume control is not near its maximum setting.

 

[shadyJ]

Thanks Shady - I should have just not been lazy and ran the calc on the cone surface area ... good points that make mechanical sense also on the mass...F=M*A more F needed for more M at constant A.

Am I correct in assuming that greater acceleration, at higher mass and surface area as well as natural frequency interactions are what is primarily responsible to achieve a higher dB SPL on a sub?

I also overlooked the fact that I'm only at at most 50% gain on the sub knob. The thing can do more than I am asking of it...it wasn't a scientific test after-all. Not even to mention room gain or nulls coming into play.

Yes, you need a lot more power to move heavier cones, especially at higher frequencies (takes a lot more energy to move a heavy object quickly rather than slowly). The moving mass in subwoofer drivers are very heavy compared to the midwoofers that Klipsch uses in their tower speakers. Those woofers typically have to be capable at frequencies well over 2 kHz, whereas the SVS driver only needs to worry about 20 Hz to 200 Hz. Very different set of mechanical and electrical demands.