There are two very good posts from a pro user, pentagon, on gear space about how he gets the best response from ATCs. There seem to be lots of ways to skin a cat.
"One room: 100ASL freestanding no subs -3dB point 26.6 Hz, with dual subs (these are 15" subs with 226L cabinets sealed) this room is extended down to 19.7 Hz for -3dB point.
- Second room: 110ASL freestanding no subs -3dB point 28.6 Hz, with dual subs (these are 18" subs with nearly 300L cabinets ported) room is extended down to 15.08 Hz for -3dB point.
- My room:100ASL freestanding no subs -3dB point 20 Hz. I have no sub integrated for extension because the room provided that much support with placement.
3 different rooms. 3 different responses for low end -- all very much about placement. The one thing clear is none of these suffer from "light bass" even without subs
if you place the speakers correctly. These are the numbers with the flat segment of the bandwidth
per speaker at 85dBC at the listening position (and with no strain or compression playing to our required 105dBC.) (listening position 2.5m to 3m away depending on room)
People may like exaggerated bass or throw speakers in their room with zero sense of positioning ("my one speakers worked well here, everything should") but set up correctly, the large ATCs are not bass light. And the room makes a tremendous difference for the low end.
(As an aside, was just in a room I couldn't get to work below 40Hz. And the room had 7 subs. But the problem was the room and the required positioning of the speakers prevented better tuning. This was another brand of well-respected speakers.)
Three major things: boundary walls, room dimensions (especially width) and vertical height.
Large woofers often end up in the vertical null due to the floor to ceiling height. You don't want the voice coil to be at a 1/4, 1/8, etc (and multiples) in the vertical plane. A standard 8ft ceiling can cause problems for that.
Second, have the rear of the speaker pressed against the wall behind it. The cabinets of the 50 and up are already deep which means the rear wall of the speaker to the voice coil is going to be at a distance already that you can't overcome. But you want it coupled to the boundary as close as you can (unless you have a really large room in which case you can be very freestanding -- but I've rarely seen a room like that outside of rooms like Real World Studios, etc because then the listening position can't be in an awkward null in the room (which mean even a longer/bigger room.) So pressed as close to the rear wall behind the speaker as possible. This also pushes up the cancellation dip from the 60-100Hz range up into the treatable higher ranges. Suckout in the below 100Hz range is what gives people the idea of lack of bass.
Third, the placement of the speakers in the width of the room. Hopefully you are working in a symmetrical room (just for L/R balance) but positioning the speakers even across the width often means you are putting them in nulls again. Measuring from the woofers again (since only the large wavelengths matter produced from the woofer, the woofer position is the only one to care about) make sure they don't sit in even (1/16, 1/8/, 1/4 and multiples) or third spacings of the room of the room width but in between.
Finally there's the listening position. You can approximate the position from the front wall (you won't be wanting to sit in even positions again) but I like to run sound out the speaker and sitting in a rolling chair, roll front to back down the center line to find the right listening point. Toe in/toe out of the speaker doesn't really matter because this is about low end. I like to do it with bandlimited pink noise 40-80Hz but I'm very familiar about how that should sound verses frequencies poking out (a dominant resonance.) I think most outside of those who do Dolby tuning often, would not. Then I'll start to measure from that spot to see if I've picked the right one.
After finding the spot, then adjust the toe-in/toe-out of the speaker to make sure the directional frequencies are generating a proper stereo field with a crystal clear phantom center image.
This isn't a fast process (my surround systems take about 7-8 hours to setup.) Which is why I brush off those who just get in speakers and pop them up and start making judgements. Every speaker has a different cabinet size, woofer size, different woofer placement in the baffle, and different acoustic center axis which has to be adjusted for. And when you get to large woofers and large, heavy cabinets the issues are more pronounced.
Just to point out how prevalent bad positioning can be: walked into VKLA's listening room. They had the ATC
SCM150ASL. First thing I noticed is they had them on incredibly high stands. The woofer, was at the center of the vertical height of the room. I put a track out them (I was there to listen to other speakers but couldn't resist since I'm on 100ASL all day) and they sounded anemic. Far worse than my speakers. Just awful. A sales guy and his client walked in and they saw the size of the speaker and said "they sound great, don't they?" and I went "No, they sound awful. They need to be set up right." And then I tried to explain to the client that this isn't how the speakers should sound. But first impressions... he probably thinks they are "bass light" now."
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