Gene, would you be so kind to post your REW file here for us to study? I hear you about the waterfall plot settings, but it makes it hard for your readers to compare your plots to other plots found here when you change the settings. If you want, just post a plot for your best seat because some of us are curious. I have no doubt if I added two more subs to my setup it'd sound slightly better than just two subs and the waterfall would look even better.
Also I never said absorption doesn't absorb, of course it does (I thought you were an EE like me, so I didn't state the obvious in my post here). Anyways, what I'm saying is there is a lot of energy that was previously lost due to wave cancellations that IS regained using bass traps
(e.g. bass traps fix the dips). No one said this was a free lunch, so maybe you are not understanding what I'm saying? There is some
energy that was previously lost to the room's characteristics, that is being regained with bass traps, so this net loss of energy you are so concerned about is lower than you might think. For example, here is a pic linked from Ethan's site:
Also, for others who really follow what your video says, they will not get as good of performance as multiple subs + some DIY bass traps. This is because DIY bass traps like the ones I made from OC 703 4" layers absorb way higher and even help mid and high frequency reflections too. Your method as you know only helps below the crossover freq set for your subs.
Sounds like you are concerned about lost efficiency, so how much energy do you think would be lost by adding lots of bass traps? Have you ever measured this or have a reference for us that does? My setup has tons of headroom and sounds great to me, with very very little ringing, but I'm using Dirac + multiple subs + acoustic treatments. Not trying to be sarcastic, but I'm genuinely curious. Anything I can do to my setup to improve things, I am going to at least study objectively.
Not sure if you used Dirac, but it's been very predictable for me. It appears their new system "Dirac Unison" will do exactly what you describe for Harmon's SFM, but I don't have Dirac Unison yet. As you imply, nothing wrong with wrong with not treating above 300 Hz if that's your preference, but hopefully your viewers add acoustic panels to treat early reflections. Dirac has always sounded great for me though, and I measure everything before and after in REW with no curve smoothing.
Originally Posted by Gene DellaSala
Thanks for painting our website with a broad brush. I saw your comment on our Youtube video and responded as follows:
First nobody called bass traps snake oil. I'm sorry that you misinterpret what we've said. Bass Traps do work and they can be a viable option for sound reproduction in small room room acoustics and are absolutely essential for sound production in recording studios. While you can measure a few points in space and show how bass traps fill in nulls in the room, the overall sound level in the room drops. Absorption ABSORBS. If you don't believe this, measure a speaker at 1 meter in an anechoic chamber and then measure it again in a real room. You will note, depending on location in the room and frequency in question, the in-room measurement will be anywhere between 6-18dB louder b/c of boundary gain and room gain. I suggest getting a copy of Sound Reproduction: Loudspeakers and Rooms by Dr. Floyd Toole as he goes into detail about this. There are NO free lunches, absorption turns energy into heat which means you lose some output. The default settings for REW don't show enough time domain resolution which is what we were getting at in the video. You need to change the window time to around 40ms if you want the waterfall to actually show a more accurate representation of decay rates in your room. Otherwise, you're masking the decay rate and seeing an almost infinite straight line of ringing for the entire span of the graph. WE actually have a video coming online next week that discusses this. Also regarding EQ, we aren't talking about Audyssey, we are talking about something far more effective called Sound Field Management (SFM) which is a Harman tech that crunches away measured data for each sub to properly set delay, phase, level and EQ to minimized seat-seat variations BEFORE applying a global EQ to all subs. Audyssey is NOT that sophisticated. What I did with mDSP is close but still note to the level of SFM.
As for stereo bass, you missed the point. My main speakers are designed to play as a single unit, hence why I configured their bass drivers for stereo bass. I wasn't concerned about stereo bass below 80Hz but between 80Hz to 300Hz. I also used the EQ of mDSP to help improve that region b/c EQ is still effective up to the room transition frequency (300-400Hz). For those that don't know what a room transition frequency is, it's the region where the room stops being the major influence of sound and the speaker takes over. This is part of the reason why above the transition frequency, Auto-EQ correction becomes ineffective and unpredictable.