Welcome to No Limit Sound Productions

Company Founded
2005
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Our services include Sound Engineering, Audio Post-Production, System Upgrades and Equipment Consulting.
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Our mission is to provide excellent quality and service to our customers. We do customized service.

Tuesday, December 12, 2017

Q. Is asymmetry in monitors a problem?

I'm considering AVI's Pro Nine Plus system for my main nearfield monitoring, partly based on the great review they got from Paul White back in September 2005 (/sos/sep05/articles/avipronine.htm). Should I be worried about the fact that the tweeter mounting and porting are both asymmetrical in relation to the main driver? Will this cause slight delay/phasing issues when placed in the classic equilateral-triangle stereo setup?

AVI's Pro Nine Plus monitors (left) have their tweeter mounting and porting asymmetrical to the main driver. This is actually relatively common, as you can see from the Acoustic Energy AE22s and the Dynaudio BM15As (below). 
AVI's Pro Nine Plus monitors (left) have their tweeter mounting and porting asymmetrical to the main driver. This is actually relatively common, as you can see from the Acoustic Energy AE22s and the Dynaudio BM15As (below).
 Q. Is asymmetry in monitors a problem?Q. Is asymmetry in monitors a problem?

Via SOS web site

SOS contributor Mike Senior replies: Opinions differ about a lot of aspects of speaker design, as you can easily see even just from comparing the external appearance of a selection of similarly priced monitors. One such moot point is how important symmetrical driver placement is, and the Pro Nines are by no means the only speakers that have their tweeters skewed to one side like this. The Acoutic Energy AE22s and Dynaudio BM15As both feature this kind of setup, and are both nonetheless well-regarded. Although I've not tried these specific speakers myself, the main thing I'd be wary of in principle is that the size of the stereo sweet spot may be reduced. No matter which way you move your head (forward/back, side to side, or up/down) the potential for inter-driver phasing in the mid-range appears to me to be greater than with a more traditional vertically stacked driver configuration. Even if this theoretical concern is borne out in practice, though, the real question is how much it'll matter to you. If you're happy to stay in the sweet spot most of the time, and can check the mid-range balance with a single-driver speaker such as an Auratone (or similar), then it may not be a huge practical concern. Personally, I'd say that if you like the speakers otherwise, don't let the asymmetry be a deal-breaker.

As for the ports, again I don't think their asymmetry should really put you off, and although I find that porting in budget-level monitors can cause all sorts of low-end monitoring problems, I would imagine that these speakers are probably getting into the kind of price range where the potential problematic side-effects of the porting are kept well enough under control that you can work with them for mixing purposes. Certainly, the 90Hz low-end boundary on the published frequency-response figure leads me to suspect that the port hasn't been overhyped, as it seems to be on many budget models, and that counts for a lot in terms of accuracy.


Published February 2012

Saturday, December 9, 2017

Q. Do mixes benefit from low-pass filtering at mixdown?

I've heard a lot about high-pass filtering tracks to reduce clutter at mixdown, but not as much about low-pass filtering in this context. Would mixes suffer or benefit from doing the same at the opposite end? For example, would it be easier to bring out 'air' in a vocal if other parts were low-passed?

 Via SOS web site

SOS contributor Mike Senior replies: Particularly in small-studio environments where the low-frequency monitoring fidelity is questionable, there's a lot to be said for high-pass filtering in a fairly systematic way to head off problems at mixdown. However, widespread low-pass filtering offers fewer benefits, simply because so many instruments in a mix will have harmonics and noise components that extend right up the spectrum. In practice, I find peaking/shelving cuts are, therefore, more appropriate for dealing with typical mixdown tasks, such as frequency-masking problems. Yes, in theory you could make your lead vocal sound airier by low-pass filtering the other parts, but you'd still have to consider how the mix as a whole will sound during moments when the vocal isn't active, so achieving an airy vocal in practice isn't usually as simple as this.

Although fairly systematic high-pass filtering is very sensible in home-studio mixing, as you can see in this screenshot from a recent Mix Rescue project, it's rarely beneficial to apply low-pass filtering in a similar way. 
Although fairly systematic high-pass filtering is very sensible in home-studio mixing, as you can see in this screenshot from a recent Mix Rescue project, it's rarely beneficial to apply low-pass filtering in a similar way.

Having said that, there's nothing wrong with low-pass filtering if you really want to kill the high frequencies of an instrument for balancing reasons. I would most commonly do this with amped instruments, such as electric guitars, which are capable of contributing a lot of undesirable amplifier noise in the top two octaves of the audible spectrum. However, this has to be evaluated on a case-by-case basis, because it's very easy to dull the overall mix if you're not careful.


Published January 2012

Thursday, December 7, 2017

Q. Is flutter echo a problem in a well-treated room?

My daughter managed to play a tough piece she's been practising on the keyboard this weekend. She played it so well that we clapped our hands... then we noticed how strange the clapping sounded. It rang on but died very quickly, and for the time it rang on, it sounded very metallic and almost robotic.That was close to the middle of the room. The room is partially treated at the moment, with panels at the side-wall reflection points and ceiling, one on the ceiling, and three corner superchunks. I tried clapping again with some further panels on the side walls directly to the left and right of where I was sitting, and the noise disappeared. I understand enough to realise the sound is the clap bouncing back and forth between the two walls, and I'm guessing that this is what folk refer to as flutter echo. What I'm a little less sure about is whether it is a problem, and what — generally — a hand clap should sound like in a well-treated room.

Via SOS web site

SOS Technical Editor Hugh Robjohns replies: If we're talking about the sound in a control room, the point is what the room sounds like when listening to sound from the monitor speakers. It is conceivable that, by design (or coincidence), the acoustics could well sound spot on for sounds from the speakers, but less accurate or flattering for sources elsewhere. And, unless you're planning on recording sources in the control room at the position you were clapping your hands, those flutter echoes might not represent a problem or require 'fixing'.

However, in general, strong flutter echoes are rarely a good thing to have in a control room and I'd certainly be thinking about putting up some absorption or diffusion on those bare walls to prevent such blatant flutter echoes.

Flutter echoes in a studio can be distracting and fatiguing, so it's often worth putting up some absorbent foam on bare walls to reduce them.  Don't overdo it, though: you need to maintain a balanced acoustic. 
Flutter echoes in a studio can be distracting and fatiguing, so it's often worth putting up some absorbent foam on bare walls to reduce them. Don't overdo it, though: you need to maintain a balanced acoustic.

You shouldn't go overboard with the room treatment, though, because while working in a control room that has 'ringy' flutter echoes or an ultra-live acoustic can be very distracting and fatiguing, so too is trying to work in a room that sounds nearly as dead as an anechoic chamber!

Of course, traditional control rooms are pretty dead, acoustically speaking, and that is necessary so that you can hear what you are doing in a mix without the room effects dominating things. But the key is to maintain a balanced acoustic character across the entire frequency spectrum. The temptation in your situation might simply be to stick a load of acoustic absorbers on the walls, and that would almost certainly kill the flutter echoes, but in doing so there is also a risk that you'd end up with too much HF and mid-range absorption in the room (relative to the bass-end absorption).

That situation would tend to make the room sound boxy, coloured and unbalanced, and that's why a better alternative, sometimes, is to use diffusion rather than absorption; to scatter the reflections rather than absorb them. The end result is the same, in that the flutter echoes are removed, but the diffusion approach keeps more mid-range and HF sound energy in the room.

The question of which approach to use — diffusion or absorption (or even a bit of both) — depends on how the rest of the room sounds, but from your description I'd say you still had quite a way to go with absorption before you've gone too far.

To sum up, I'd suggest that you're not worrying unnecessarily, and that it would help to put up some treatment to reduce those flutter echoes.


Published February 2012