Is two subs that much better than one?

Hi there

My setup has 2 subs, 1 in the bottom of each speaker, and I think that makes a lot of difference, (not that I could ever turn one off to make any diff but there you go).

I remember having quite a long and tough discussion on the HI FI choice forum a year or so ago about whether bass is mono or stereo, I think we agreed to disagree in the end. (I beleive it was with Matt F, if that's the same Matt F that is).

Maybe it doesn't make as much difference in music, but I think it certainly does with Films.

 

Merlin, forgive me, but if your system sounds anything like a cinema I think I'll pass.

 

Merlin is currently using them in his AV system

Dont take the piss, these are superb for music, and you'd have to pay a very serious amount of money to better them (musically) with commercial subs.

 

This is absolutely spot on – low distortion is the key and when you first hear low bass with little/no distortion it can be a bit weird – it sounds like there is less bass until you get used to how clean it is.

It's not difficult to play cleanly at low volumes or at high frequencies but to play cleanly at decent volumes down at the lower frequencies (>25Hz) is where it becomes tricky and that's why subs with minimal distortion are thin on the ground – a few DIY designs (Merlin, take a bow), some expensive servo controlled-units and a few cheaper gems such as SVS and Paradigm's Servo 15. As Merlin says, you are almost always talking about big enclosures, big drivers and plenty of power.

Unfortunately, distortion figures are hardly ever quoted – you can hazard a guess at why – let's just say that it would not make pleasant reading. I know that Nic Rhodes (no not that one - a member over at avforums and a respected engineer) has measured distortion figures for loads of popular subs – according to him it was not uncommon to see distortion figures of 30-40% from some of the little “5 star†boxes!

I also agree about the nonsensical specmanship regarding how low subs will go. The fact that these specs are incomparable due to various reasons (different –dB readings, "in room" vs anechoic) makes the whole thing laughable – according to specs an REL Q200 (small box, 10†cone, 200 watts) drops to 17Hz but a Velo HGS15 (big box, 15†cone, 1250 watts) only manages 18Hz but the former is –6dB "in room" and the latter is –3dB anechoic. The Q200 at –3dB gives 25Hz – remove room loading and we'd be talking more like 30Hz.. Yamaha take the biscuit – they use –10dB figures!

What would be good would be for a standard to be applied – say –3dB anechoic. It would be really interesting though if a maximum distortion limit was used too (say 10%). Tom V of SVS published a list a while back showing the maximum depth and output of a whole host of subs using a 10% distortion limit – it made interesting reading – a lot of them looked much less impressive when limited in this way.

L Hatkins – yes I am the same Matt F and I can vaguely remember the debate. I think I was arguing that bass below a certain frequency (i.e. where it become non-directional) doesn't need to be in stereo because the positioning cues out brains use is taken from the harmonics and that this is why home cinema only needs to use one channel for LFE (which is generally below 80Hz but can theoretically be up to 120 Hz, I think),

Enough from me.

Matt.

 

Alex,

what they do is give proper bass with gravitas. None of this "soundalike" , constipated and overdamped crap that people think is correct simply because they have spent all their life listening to typically wimpy mini speakers

 

For movies it is ok higher xover, with almost any sub, but my system is calibrated for music, and my comments are related to music, of course when a system plays well music, I mean "whole" frequency range, it plays movies more than well enough, I still look out the window every time there is a storm playing, as well as rain, stronger than me, and I think this shows it is fairly accurate... :MILD:

 

Merlin's custom JBL subs, are the best I've heard as an all round sub package, they are complete musicaly, superb imiging and intergration, with beautiful image tangiability & reinforcment, yes I've heard louder and lower subs, but none as 'complete', mind you if they were animal, they would be a redeo Horse Wm

 

The biggest problem with most systems, regarding bass, is the room, regardless of the subs used, even my golden ratio room with two subs has some peaks, but they only bother me with few discs, I dont need EQ with most...

 

Just to add that in my system running the sub at line level rather than speaker level is a rather obvious improvement.

 

As it should with proper active xover, at least with non "full range" speakers... :MILD:

 

There's two different things there. The 80hz cut-off wasn't really around till THX picked it for their system. It was chosen from studies into psychoacoustics and is pretty much the highest crossover frequency usable before bass becomes obviously directional. Stereo pressure differences may still be detectable below this frequency and I think Lexicon still suggest that stereo subs are a good idea.

The LFE is an 'additional' channel, bandwidth limited to 120hz and recorded -10db below reference. It's purpose originally was to allow cinemas to cheaply add extra subs or use existing unused speakers for additional bass headroom. Cinemas did/do run with some very old speakers and this allowed them to upgrade without having to replace their front speakers. The LFE is an extra channel and systems should run perfectly without it being reproduced.

In my house all the really deep bass does is make everything rattle. Which is a pain and doesn't really add to the enjoyment.

 

I just talked to Nestorovic about some of these points. He says that each manufacturer gives specs mesured in conditions the unit shows its best because "all" of them have high distorsions in normal conditions. They are magazines who aren't giving anymore specs for woofers because they don't have any sence.
Nestorovic says his goals is to have "very low" distortion subwoofers but that is very complicated to do. He has noticed that every driver which is bigger than 12" 'break up' the cone. This means that when looking with a strobe light, the cone doesn't move up and down as a unit. You see waves in it. Especially very light cones break up and this makes lot of distortions. But this which makes colouring is very appreciated by lot of people especially in Rock & Roll. Another point are the standing waves in the chassis mostly caused by parallel sides. These standing effect the motion of the cone and also add colouration.
His subs go down to 16Hz and at 10 Watts the distortion is less than 1%.
-1 db anechoic.

 

Well, most of them do but not "all" - SVS and Paradigm (Servo15) generally keep distortion below 5% and don't go above 10% - this is still very low - SVS go for large enclosures, Paradigm use servo control. Velodyne's HGA15/18 keep below 1% - which is outstanding but takes mega-over engineering - huge amps and servo-control.

A good new pointer is THX Ultra II for subs as to pass this a sub has to produce 105dB at 20Hz with no more than 4% distortion under anechoic conditions. You can count the subs that have passed this on the fingers of one or two hands - you certainly wouldn't have to take your shoes and socks off.

As for showing your sub at it's best - this is not always the case - some are just more honest that others - M&K, for example, could make their subs look better by moving from -2dB to -6dB. Velodyne could improve their figures by using room loaded figures rather than anechoic ones. It all comes down to knowing what methods/dB's each manufacturers use and what difference they can make.

What would be interesting to know would be how much distortion an average floorstander produces down at, say, 35Hz or 40Hz - I've a feeling it would be quite a bit.

As for the LFE channel - to me it's an essential part of the soundtrack (although some films make more use of it than others) - I would concede though that you need a decent sub set up properly to get the most from it.

Matt.

 

Saturday we tested a few subwoofer ICs with a Quake, first cheapo Profigold, then a fairly expensive (for a sub IC) QED QN, incredible, a lot more bass, sounded like the sub had been disconnected before, then my Audioquest G-Snake, nearly half the price, believe me, he heard lower notes that we didn't know where there before, and much tighter bass too...

So there is more than the sub itself to take in consideration, mainly setup, of course, but most people doesn't take full advantage of their subs, regardless of specs... :JPS: