Dual sub placement - corners or beside speakers?

[Thetiminator]

Thanks MA. That is a huge difference indeed but 4 subs would cost me hundreds of thousands....by the time you count the divorce costs.
I’m generally very happy with the sound at the minute. I have the subs set that they fill in the missing octaves and vastly improve the soundstage without muddying detail or the sound signature of the sound of the mains in any way. 45hz was the crossover for improved sound, literally 46hz and you could hear the subs impinging on the mains and it was all downhill from there on.
Maybe DSP will improve things further and I’ll definitely give it a try, but I use open elec for my operating system so DSP will have to be a separate unit in line the chain. It’s effects might be offset by the degradation in sound by adding the hardware into the chain...I put a pair of Cardas XLR/RCA adaptors in the chain recently and the sound fell to pieces....the system is just so revealing....

 

[Purité Audio]

A pair of XLR/rca adaptors and the sound fell apart,wow!
Keith

 

[Thetiminator]

Yep. Flat as the proverbial....

 

[h.g.]

Do it by ear I'm sure you'll be fine, I had a sub with ATC 25s and ATC recommend not high passing the mains. I found it very helpful to have a friend adjusting the controls on the sub while I sat in the listening spot! This is a helpful guide from Genelec, it's more aimed at studios but the Sub placement is relevant:

Advice not to high pass the mains is very strange given this would remove one of the main benefits of using subwoofers for music which is to clean up the bass and midrange in the mains. To see some hard evidence scroll down to the intermodulation section here to see measurements for a 3 way with and without a sub. The benefit is stronger for 2 ways but it is still significant and audibly beneficial for 3 ways.

Setting up subs by ear is nigh on impossible if you wish to use them to improve low frequency sound quality by controlling the room response which dominates what we hear at low frequencies. As other have said earlier, you need to measure and introduce a form of equalisation in order to achieve this. Just adding subs into the room without integrating them with the mains or the room is completely missing the point of what subs are for when it comes to sound quality for listening to music. Impressive sound for exploding planets perhaps but not music.

I would agree with you that there is some good advice in the Genelec handout.

 

[Ted-M]

Advice not to high pass the mains is very strange given this would remove one of the main benefits of using subwoofers for music which is to clean up the bass and midrange in the mains. To see some hard evidence scroll down to the intermodulation section here to see measurements for a 3 way with and without a sub. The benefit is stronger for 2 ways but it is still significant and audibly beneficial for 3 ways.

Setting up subs by ear is nigh on impossible if you wish to use them to improve low frequency sound quality by controlling the room response which dominates what we hear at low frequencies. As other have said earlier, you need to measure and introduce a form of equalisation in order to achieve this. Just adding subs into the room without integrating them with the mains or the room is completely missing the point of what subs are for when it comes to sound quality for listening to music. Impressive sound for exploding planets perhaps but not music.

Different manufacturers/engineers will have different opinions, but I believe the advice when it comes to ATC is to integrate the sub lo pass with the natural roll off of the mains (Genelec have a different opinion). But yes, I don't disagree that high passing the mains might have a benefit, depending very much on the quality of the sub.

Why would setting up the sub by ear be impossible? If you are setting up a mixing or mastering studio then measurement would be essential but we're talking home listening. Set it up so you like the sound Like you would an eq - you don't unleash the measurement mic when you're adjusting the eq (if you have one). IMO by far the biggest problem with subs is knowing that you only need a little bit (i.e. no exploding planets!)

 

[Purité Audio]

Ideally you want the sub to be seamlessly integrated to create tight, deep bass with no overhang you don’t want just , ‘a little bit”
You want the correct amount to create your preferred target room curve.
This is simply achieved using a processor and EQ if necessary.
Keith

 

[h.g.]

Different manufacturers/engineers will have different opinions, but I believe the advice when it comes to ATC is to integrate the sub lo pass with the natural roll off of the mains (Genelec have a different opinion).

The science of how sound works at low frequencies in rooms and how we perceive that sound is a matter of fact not opinion. It is widely known and understood by engineers leading them to them all to give pretty much the same advice. The engineers at ATC will be familiar with the facts about what causes distortion in speakers and what can be done to reduce it. I find it very hard to believe that advice not to high pass main speakers is coming from such a source.

Now people in hi-fi shops selling ATC speakers and, possibly, the people marketing ATC speakers (Ashley whats-his-name of AVI fame I believe used to market ATC speakers and he could come up with some spectacular nonsense) are quite different. I recall visiting my local hifi shop a few years ago (name withheld to protect the guilty) and the topic of room boom came up in a discussion mainly about something else. He quite firmly stated he never had any issues with room boom because he knew which cables to use. Completely threw me and I had difficulty continuing the conversation.

But yes, I don't disagree that high passing the mains might have a benefit, depending very much on the quality of the sub.

Not really. The benefit to the mains comes from reducing the distortion induced by large deflections of the mains own woofer or midwoofer. This is independent of the quality of the subwoofer used. Unless the subwoofer is inappropriate, e.g. being significantly smaller than the woofer or midwoofer in the mains, it will do better a job covering the low frequencies for which it is designed compared to the mains' woofer or midwoofer.

Why would setting up the sub by ear be impossible? If you are setting up a mixing or mastering studio then measurement would be essential but we're talking home listening. Set it up so you like the sound Like you would an eq - you don't unleash the measurement mic when you're adjusting the eq (if you have one). IMO by far the biggest problem with subs is knowing that you only need a little bit (i.e. no exploding planets!)

It is an interest in high sound quality in a technical sense that makes it close to impossible to set up subs by ear. The variation with frequency/phase for a single sub might be just about be doable (e.g. think fiddling with sliders on those old graphic equalisers guided by some hand calcs about what is going on) but how would you go about setting up more than one by ear? If there is no interest in sound quality in a technical sense then of course one can do whatever one likes with subs. But the perceived difference in sound quality between the typical room boom of most hi-fi setups and a competently integrated set of subs with the mains is large. Not audiophile cable night-and-day difference large but large in the real world with everyone hearing the same thing.

 

[Tw99]

The science of how sound works at low frequencies in rooms and how we perceive that sound is a matter of fact not opinion. It is widely known and understood by engineers leading them to them all to give pretty much the same advice. The engineers at ATC will be familiar with the facts about what causes distortion in speakers and what can be done to reduce it. I find it very hard to believe that advice not to high pass main speakers is coming from such a source.

hg, I agree with a lot of what you say, but in this case the ATC subwoofer manuals are pretty clear in their advice: "The Low Pass control should be set at, or slightly above, the specified low frequency cut-off of the satellite speakers." Perhaps if they made a sub with a high pass output it would be different though.

 

[Beobloke]

Regardless of whatever tuning and/or DSP you choose to use, corners are the last place you should put subwoofers unless you really have absolutely no choice.

 

[Ted-M]

Ideally you want the sub to be seamlessly integrated to create tight, deep bass with no overhang you don’t want just , ‘a little bit”
You want the correct amount to create your preferred target room curve.

I agree Keith, what I mean is, what I have heard a few times with hifi setups with a sub, is way too much dominant bass (i.e. 'impressive' in quotes), whereas a correct full range sound isn't obviously 'bassy' it just extends down a long way. And I found for me (when I had a sub) that it didn't need very much to achieve that sound.

The science of how sound works at low frequencies in rooms and how we perceive that sound is a matter of fact not opinion. It is widely known and understood by engineers leading them to them all to give pretty much the same advice. The engineers at ATC will be familiar with the facts about what causes distortion in speakers and what can be done to reduce it. I find it very hard to believe that advice not to high pass main speakers is coming from such a source.

I know I keep bringing up ATC, but their sub placement manual states don't put it against walls or in the corner, and this is a different 'opinion' to the Genelec manual. I agree that you would expect all advice to be the same. It's weird isn't it. But yes, at the end of the day I guess everyone can agree on whether the sound is correct or not.

 

[Ted-M]

Not really. The benefit to the mains comes from reducing the distortion induced by large deflections of the mains own woofer or midwoofer. This is independent of the quality of the subwoofer used. Unless the subwoofer is inappropriate, e.g. being significantly smaller than the woofer or midwoofer in the mains, it will do better a job covering the low frequencies for which it is designed compared to the mains' woofer or midwoofer.

I wouldn't say it's 'independent of the quality of the subwoofer', I'd rather have no sub, than hi passed mains and a cheap sub.

I'm sure you're right about setting up multiple subs being impossible by ear, I was thinking about when I set up my single sub which I didn't think was too tricky. Sorry for the confusion

 

[h.g.]

hg, I agree with a lot of what you say, but in this case the ATC subwoofer manuals are pretty clear in their advice: "The Low Pass control should be set at, or slightly above, the specified low frequency cut-off of the satellite speakers." Perhaps if they made a sub with a high pass output it would be different though.

Well I am surprised. I don't take much interest in ATC beyond their midrange driver but assumed their kit would be standard but you are quite correct about their subwoofers: they are effectively unusable without an external box to handle the delay, filtering and a signal to the mains. I wonder why? Anyone? Even aggressively budget £300 subs from Behringer have a filtered output to the mains.

In the home the advice to match to the roll-off of the mains isn't normally going to be possible. In an anechoic chamber the speakers may roll-off at a 1st, 2nd, 4th or whatever rate depending on cabinet loading but boundary loading and room gain (never mind room resonances) will shift both the rate, frequency and introduce wiggles. The spec sheet says ATC only supports a 2nd order rate and so it can't even work in an anechoic chamber with a sealed cabinet which is often the best option when using subs.

It is all rather interesting. Does anyone know why ATC subs are as they are? For example, does ATC perhaps take an analogue-only marketing position in order to appeal to audiophiles?

By the way none of this changes the science of how sound and subs work in rooms or what engineers know about it. Even the ones from ATC.

 

[h.g.]

I know I keep bringing up ATC, but their sub placement manual states don't put it against walls or in the corner, and this is a different 'opinion' to the Genelec manual. I agree that you would expect all advice to be the same. It's weird isn't it. But yes, at the end of the day I guess everyone can agree on whether the sound is correct or not.

If a manufacturer's sub lacks the controls to be used in a reasonable manner the advice on how to use it may well differ to that of a manufacturer of subs that do contain enough controls to be used in a reasonable manner.

Everyone can agree on a high sound quality in a technical sense because that is reasonably unique and well defined. However, if the objective is to create whatever sounds good to an individual then there is scope for large disagreements. Some characteristic sounds are attractive to some and baffling to others. Most of us have stood next to someone enthusing over a speaker with a strong characteristic sound and just been baffled by what they are picking up on to like.

 

[HansW]

Interesting subject.

I quickly checked what Velodyne and REL suggest, being focused subwoofer specialists. Both of them recommend placing their subs as close to a corner as possible. I believe Wilson also recommend corner placement of their very large offerings. Naim recommend placing their n-Sub against a side wall but away from corners.

I have an n-Sub which I now have placed in a corner and works better there than against the back wall (couldn’t find a good side wall placement). I have purchased a second n-Sub and am contemplating where to place it.

Best regards

Hans

 

[h.g.]

Where to place a sub depend on your objectives. A corner drives lots of room modes and a mid wall less room modes. Which works better depends on what you are doing with the subs. If you have only 2 then front mid wall and rear mid wall and setup to knock out the axial modes is likely to be the best in terms of sound quality but it isn't a common thing to do.

Where to place subs depends on a range factors like room shape and size, listening location, how many you have, what control you have of the sub, severity of particular room modes,... It is a pretty large task to assess all the viable combinations of locations to find a reasonably optimum one. A few more subs will always be able to fill in dips or knock down valleys in the response. I am of course talking about high sound quality in a technical sense and not an audiophile sounds good sense.

If you want to get a feel for the pros and cons of sub location then the interactive room simulator in the freely available REW software can provide this.

 

[Thetiminator]

It seems like it is a case of trial and error indeed.
I suppose there are so many variables too, like my situation where in my system the bass is so different to most other speakers as they are horn loaded. It’s completely different to the bass from my Salons, which are renouned for their bass performance.
The Air Partners don’t need any help above their roll off point and any outside influence from a sub just degrades the job (speakers have 18” Vitavox compression drivers at £3k each). There’s absolutely no overhang in the bass so it doesn’t excite the room the way box speakers do.. I’m just filling in the tiniest touch from c.45hz down, volume set at -15db...

 

[March Audio]

Regardless of whatever tuning and/or DSP you choose to use, corners are the last place you should put subwoofers unless you really have absolutely no choice.

This is not actually correct. If you use multiple subs and or dsp it is fine. You also have benefit from the boundary gain which makes the sub work less hard. Refer to my post above to see the results of corner placement.

Any sub installation is going to have problems with room modes regardless of placement unless you use dsp. HG s comments above are correct regarding high passing the mains. You reduce distortion and have a better controlled crossover region.

 

[March Audio]

It seems like it is a case of trial and error indeed.
I suppose there are so many variables too, like my situation where in my system the bass is so different to most other speakers as they are horn loaded. It’s completely different to the bass from my Salons, which are renouned for their bass performance.
The Air Partners don’t need any help above their roll off point and any outside influence from a sub just degrades the job (speakers have 18” Vitavox compression drivers at £3k each). There’s absolutely no overhang in the bass so it doesn’t excite the room the way box speakers do.. I’m just filling in the tiniest touch from c.45hz down, volume set at -15db...

modes are dependant upon the room dimensions not speaker type. Unless you have cardiod speakers which help to a degree. Larger rooms push the main modes lower in frequency where they may become less noticeable, but they are there.

No need for trial and error, as HG said, use REW room simulator, get a cheap umik mic and measure what's actually happening.

 

[Tw99]

It is all rather interesting. Does anyone know why ATC subs are as they are? For example, does ATC perhaps take an analogue-only marketing position in order to appeal to audiophiles?

ATC stick with a very traditional approach, very little "tech". For example they recommend against active room correction. I think this probably all derives from Billy Woodman's philosophy of what matters in sound reproduction. I don't think it has anything at all to do with appealing to the infinitely bizarre foibles of audiophiles because their studio equipment has the same philosophy.

It's an interesting question as to whether this approach can continue to be viable against competitors that use modern technology to their advantage.

 

[Purité Audio]

How do you integrate yours Tw with the anti mode?
Keith