MartinC

Subwoofers for Music?

Recommended Posts

I thought I’d start a thread specifically about using subwoofers in music-focused systems. This often comes up in other threads with some people apparently being very against their use, whilst I know many here also feel their systems have been enhanced by the addition of a subwoofer (or 2). I won’t ‘out’ anyone by naming names though :). To state the obvious for most, I do use a subwoofer in my system and for some context here’s a photo of my Power Sound Audio S1510 subwoofer with the rest of my system:

979064828_Subbysystem_small.jpg.0496a583bb587fe4c79608aaed82cbb7.jpg

This is where to some extent I’d visually like my sub to sit but for best performance it actually lives in the front right corner.

Let me stress right at the start that I don’t think everyone should be using subwoofers. My standpoint whenever I mention them is that they are a viable option for people to consider, rather than just being relegated to a ‘you only need/want one for movies’ sideline.

At heart the reason to consider using a subwoofer is to improve the bass reproduction of a system, most simply to increase bass extension (how low a system goes) and/or to increase the low bass levels relative to the rest of the frequency range. Why not just use main speakers that do what you want in the first place though? Some reasons to consider a subwoofer are:

  • If someone already has main speakers they really like across most of the frequency range and just wants to improve the bottom end.
  • Subwoofers provide a much cheaper route to achieve a high quality full-range sound than buying big main speakers.
  • Traditional main speakers capable of a full-range sound are BIG, such that often a separate subwoofer will be a better physical and aesthetic ‘fit’ in the room.
  • Subwoofers can be positioned away from the main speakers. This means the sub can be where it’s best for the bass response without the constraints of where the main speakers need to be to sound their best over the rest of the frequency range and to produce the desired soundstage. The use of a combined left and right channel mono bass signal also means that a subwoofer position is equally good no matter where bass is panned left to right in a mix, whereas main speaker performance will typically vary.

The above points all apply to a basic subwoofer added to a conventional system with no change to the sound leaving the main speakers. There are further potential benefits if used with additional hardware/features:

  • If a high-pass filter is applied to the signal sent to the main speakers so that a subwoofer replaces the output from the mains rather than adding to it, then this can reduce distortion. Specifically, intermodulation distortion from the main speakers and usually harmonic distortion at the frequencies handed over to the sub will be lower too (in both cases more so for two-way main speakers than three-ways I should think). It will also increase the headroom of the amp driving the main speakers for the frequency range it is left to deal with. (I’m assuming an active subwoofer here.)
  • Some subwoofers have built in EQ that allows for correction of room mode effects over the region they cover.
  • In the wider context of EQ, it can be helpful to be able to adjust the output level of the low bass independently of the rest of the frequency range.

Some arguments against using a subwoofer though are as follows, and although it will be a shorter list this is not to suggest they’re less significant than the potential benefits I’ve just set out:

  • If someone can achieve a system that sounds perfect to them without using a subwoofer then there is no reason to consider one!
  • There is a HUGE challenge to get a subwoofer to integrate properly with the sound of the main speakers. It is very easy to add a subwoofer and make a system sound worse!
  • Additional space will be needed for the subwoofer, and aesthetically many may simply not want one too.

The integration question is key so I’ll say a little more about this, with there being a very clear distinction between simply adding a stand-alone subwoofer and making use of analogue or particularly digital crossovers to aid this process.

If just adding a stand-alone subwoofer then the challenge is to use the low-pass filter, phase and gain (volume) settings on the sub to try to manage the crossover region where the outputs of both sub and main speakers are significant and summing with each other. Often the frequency range of this overlap region can be large, due the gradual fall-off in the main speaker output at the bottom end and the equally gradual roll-off of filters applied by subs. As such it can be far from easy to achieve good integration and in many cases people simply fail to ever do so well and sell a sub on. The appeal of this approach seems greater to me the more limited the bass extension of the main speakers is but many achieve results they enjoy in this way even with full size floorstanding speakers.

If applying a high-pass filter to the main speakers then this can make integration easier if it enables the overlapping frequency range covered by both sub and main speakers to be reduced. An additional key aspect to improving integration that I’m only aware of being implemented via DSP is the ability to have full control over time delays between the main speakers and subwoofers. In many setups the subwoofer will be further away from the listener than the main speakers and so to get things properly time-aligned the signal sent to the main speakers needs to be delayed relative to the sub. A phase control on a subwoofer can’t do this, and even if a sub is closer than the main speakers controls on a sub are generally crude in comparison to what can be achieved externally via DSP. I will though note that DSP-based subwoofer integration will be a much more appealing option for those with exclusively digital sources than those who use a turntable, and that whilst I feel time-delay correction is optimal I don’t think it’s as essential as it may first appear. Many people who don’t fully correct for this still enjoy using subwoofers, including members of this forum.

One final point I’ll make on integration is that no matter what approach is being taken I think it is far easier to optimise with the aid of microphone measurements to see what is actually going on. Which is not to say lots of people haven’t got results they like without doing so.

.

I use DSP to integrate my subwoofer using a miniDSP SHD, along with applying EQ to manage room mode effects. It is particularly in this context that I am a ‘fan’, which I’m aware is very different to simply adding a stand-alone sub to a more conventional system. On the flip-side I would encourage those who have only ever tried the latter to not dismiss the former without having experienced it. For what it’s worth I doubt I could meaningfully enhance my own system with a sub without DSP and EQ. I did try adding a sub to a different system without DSP years ago but at the time I lived in a flat with poor sound-proofing and so essentially I could never run the sub loud enough to do anything meaningful. Consequently integration was rather moot :(.

Edited by MartinC
  • Like 5
  • Upvote 2

Share this post


Link to post
Share on other sites

I have used subs on and off for 20 years. My first was a Rel Stadium II, and now using a Velodyne DD15 and looking for a second to scratch an itch. Before the Velodyne I had twin M&K MX5000 and a MX350 in a second system. The DSP of the Velodyne gives them the edge in my view.

I have had a Kef 30b and thought it was poor. The jury was out on the BK FF200, OK, but a bit thumpy.

I have a Sunfire too, stupid heavy 30cm cube with DSP. 

Subs need a solid surface to work well, if you have suspended floors, you will need some stone based platform or a hardfoam platform. 

DSP is good with subs.

Edited by It Cost How Much!?!
  • Like 1

Share this post


Link to post
Share on other sites

I bought one from BK, only because the speakers I had at the time, last year (Argon 1's) were very bass shy for the 500 CD's and "homemade" recordings I had,

(pipe organ) where to hear true frequencies of 20 Hz was a  requirement, even tho the longest pipes of 32' reach a true 16Hz. For 99.9999% of my other music its "just there" as a support if needed, beside, one can always turn it off if required. My Argon 3 LS sound good, but still need a helping hand

Share this post


Link to post
Share on other sites

I am Keith ...,and I’m a sub user 😁

well my home brew units I would more describe as full range bass speakers as in my active system they run from <16 Hz to 200 Hz after which the mid bass unit is in my monitors take over.  It’s taken 18 months of tweakery and finally a new cabinet build with the 18” Volt drivers to get it as I like it etc ....and the use of 750 watt pa monoblocks feeding each one also helped 

  • Haha 3

Share this post


Link to post
Share on other sites

As a couple of people have mentioned BK subwoofers I'll say the first sub I used recently was a Monolith, that is currently sitting at the bottom of my stairs acting as a table as I haven't got round to selling it yet. The sub I had years ago was a Ruark LogRhythm for which BK were the OEM too actually.

Share this post


Link to post
Share on other sites

I’ve got a Ruark Vita 50, which I think was part of their home cinema range. It’s a rebranded MJ Acoustics sub, as far as I know. Dialled in to fill out the bottom of my Emit 20 s, it works pretty well, though I’ve been tempted by a QAcoustics 2070i, which I remember someone on here saying they preferred, due to its two small drivers array sounding tighter and tidier?

Share this post


Link to post
Share on other sites

I'm sure you knew I'd have a 1000 questions on this! :)

2 hours ago, MartinC said:
  • Subwoofers can be positioned away from the main speakers. This means the sub can be where it’s best for the bass response without the constraints of where the main speakers need to be to sound their best over the rest of the frequency range and to produce the desired soundstage. The use of a combined left and right channel mono bass signal also means that a subwoofer position is equally good no matter where bass is panned left to right in a mix, whereas main speaker performance will vary.

it's this area of Subs that interests me the most, it makes perfect sense to me as a tool to help manage the room

2 hours ago, MartinC said:

I use DSP to integrate my subwoofer using a miniDSP SHD, along with applying EQ to manage room mode effects. 

I'm assuming (hoping) that Dirac live can sort out the timing as well as EQ, is that right?

I'm quite interested in using multiple subs, quite a few challenges in getting it right I think. I had read a paper and a presentation on it but can't seem to find it now. From memory (and I might be remembering this wrong) 3-4 subs were recommended, the aim was to have 2 subs nearer to the plane of the main speakers, then other subs nearer to the listening position positioned in a way to address room modes. I think the subs near the speakers might have been opposite phase (can't remember if this was against the main speakers when no EQ was used to reduce the cross over, or if it was more against the other subs as a way to manage room modes better).

I've not really got any experience with phase cancellation, not sure how effective it is practically, and in this multi-sub setup if it's going to work like I picture it in my head.

a bit more info in these 2 links

http://www.acousticfrontiers.com/20101029using-multiple-subwoofers-to-improve-bass-the-welti-devantie-html/

https://mehlau.net/audio/multisub_geddes/

has anyone got any experience with multi-sub setups? would be interested to hear more about how you went about things and tips/tricks or problems.

1 other related question to all this, someone in the Linn forum was advised by Linn when integrating a sub into their system with no EQ to reverse the polarity of their speakers (I assume better to just do this with the bass if you're active/multi amped) and to also bung the ports. Assume the aim here is to minimise the impact of the speaker without any EQ, and you'll need to play with the gain on the sub to get things right. Might be a bit tricky to do all this by ear.

Share this post


Link to post
Share on other sites
25 minutes ago, Phobic said:

I'm assuming (hoping) that Dirac live can sort out the timing as well as EQ, is that right?

The 2 channel version I've used doesn't. There is a multi-channel version that I think now does but I'm not sure whether this can be used in an otherwise stereo setup or not.

Regarding your other questions about multiple sub setups my gut reaction is that you're probably making things more complicated than you need to be if you're still primarily concerned about a single listening position.

Edited by MartinC
  • Like 1
  • Upvote 1

Share this post


Link to post
Share on other sites
20 minutes ago, Phobic said:

1 other related question to all this, someone in the Linn forum was advised by Linn when integrating a sub into their system with no EQ to reverse the polarity of their speakers (I assume better to just do this with the bass if you're active/multi amped) and to also bung the ports. Assume the aim here is to minimise the impact of the speaker without any EQ, and you'll need to play with the gain on the sub to get things right. Might be a bit tricky to do all this by ear.

You'd want to check exactly what is suggested to be reversed. Reversing the polarity of the just the bass on a speaker would surely mess up the crossover region to the higher frequency driver? I've seen comments about this before but never dug into it more as I have no need to do it.

Share this post


Link to post
Share on other sites
2 minutes ago, MartinC said:

The 2 channel version I've used doesn't. There is a multi-channel version that I think now does but I'm not sure whether this can be used in an otherwise stereo setup or not.

I'll have to have a read about the right setup for my system.

I had a play with Dirac live and I don't remember seeing anyway to control timing. My surround sub's not currently integrated into my 2 channel setup, is it a sub specific setting? either than or I just didn't spot it, though I found dirac refreshing simple and easy to use.

2 minutes ago, MartinC said:

Regarding your other questions about multiple sub setups my gut reaction is that you're probably making things more complicated than you need to be if you're till primarily concerned about a single listening position.

yes I recognise that. I'm looking at multi-sub more as a potential longer term upgrade option rather than something to jump straight into. I've got a lot to learn and try before I get to a place where I'd be ready to give it a try

8 minutes ago, MartinC said:

You'd want to check exactly what is suggested to be reversed. Reversing the polarity of the just the bass on a speaker would surely mess up the crossover region to the higher frequency driver? I've seen comments about this before but never dug into it more as I have no need to do it.

The instructions from Linn were 2nd hand so not certain exactly what they were suggesting.

I'd not even thought about the crossover region, makes perfect sense now you mention it.

Share this post


Link to post
Share on other sites
1 hour ago, mr neds said:

I’ve got a Ruark Vita 50, which I think was part of their home cinema range. It’s a rebranded MJ Acoustics sub, as far as I know. Dialled in to fill out the bottom of my Emit 20 s, it works pretty well, though I’ve been tempted by a QAcoustics 2070i, which I remember someone on here saying they preferred, due to its two small drivers array sounding tighter and tidier?

Do you have any idea what the person in question was comparing with? My gut reaction to this last part is that the 2070 may just have not gone as low. I just had a quick Google for info. on your Vita 50 but can't find much more than pictures. What size driver does it have? And any idea of the amplifier power? A 2070i may not be an upgrade...

Share this post


Link to post
Share on other sites

forgot to say @MartinC

your first post was brilliant, a really good & objective overview to the topic. Thanks for taking the time to write it.

makes me wish there was a wiki on this site, it's really hard for people to find relevant info, the search function can be a bit hit and miss.

Edited by Phobic
  • Like 1

Share this post


Link to post
Share on other sites

Martin, the Ruark is 50 watts, I think, as per the model number.The driver is an 8”. I would have thought that the sum of the 2070 drivers would be at least equal? I don’t or rather can’t listen at high levels, so I don’t need much power

Share this post


Link to post
Share on other sites
18 minutes ago, mr neds said:

Martin, the Ruark is 50 watts, I think, as per the model number. The driver is an 8”. I would have thought that the sum of the 2070 drivers would be at least equal? I don’t or rather can’t listen at high levels, so I don’t need much power

Yes, you're right, the Q Acoustics sub should be more capable :). Do you know what the person you quoted before was comparing to though? I don't believe there is an inherent advantage of using two smaller drivers other than that it allows the cabinet to be narrower, which I expect is the real reason they've been used by Q Acoustics. For what it's worth there is a bit of a myth that big drivers are 'slow', whatever that means, but ignore it.

The 2070i is a ported sub whereas from what I can see from photos your current sub is sealed? This difference would lean towards your current sub being slightly cleaner/tighter sounding if anything I'd have thought, unless its distortion is higher due to working closer to its limits.

A BK Electronics Gemini ii would be an alternative to consider if you're looking for a newer small sub, which should go a bit deeper than the Q Acoustics sub. If you were looking to buy new be aware that BK sell of 'Grade B' stock on eBay using the colossusxb username. The general consensus on AVForums is that people who buy these struggle to find what is actually wrong with them bit in principle it's blemishes on the cabinet that make them cheaper.

Your listening requirements are obviously a bit unusual though so something you could try first may be best. Or possibly picking up something second hand local to you that you could sell on for roughly what you paid for it if it didn't work out.

  • Like 1

Share this post


Link to post
Share on other sites

I’m always using bookshelf/standmount speakers. Hence, a sub is necessary. I enjoy adding a sub to my system. Currently using the Rythmik F12. 

  • Like 1

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.