How can I get two subwoofers in stereo?

Wirefire

Standard Member
Joined
Aug 28, 2009
Messages
2
Reaction score
0
Points
1
Feel free to hit me to the back of my head if this is the wrong area (or if this has been answered, didn't find anything by searching), but I figured you guys might be able to answer my rather weird question.

Since my puny Tangent EVO E5s (while being very decent computer speakers especially for the money) lack some boom, oomph and thump where it's required, I thought that perhaps I could wire two 10" subwoofers to go with the stereo speakers to enhance the bass. Now I have no experience with crossovers, subwoofer amplifiers and the such, but I was thinking of D.I.Y subwoofers to keep the costs down (I'm not ridiculously picky about the quality, just a tad choosy), preferably under 300$ for the subwoofer elements themselves and then some for the amps. If I have to replace my Onkyo TX SR507 I'm fine with that. I understand this can get a bit expensive, but since I'm intending to stick with standmounters, this seems to be a fun project that'll enhance the bass of not only my EVOs, but all of my future PC speakers (Wharfedale Diamond 10.1s?) too!

Sorry for the rambling. So my point is to have two small subwoofers in stereo + the standmounter stereo speakers themselves. Do I need to have an amplifier that has two outputs for left and right speakers (I believe this is called multi-room or something?) for this?

Thanks for your time!
 
Hi and welcome to the forum :hiya:

having 2 subs doesn`t make them stereo, stereo is a dedication of 2 separate left and right channels whereas the sub channel is a dedicated sub frequency mono channel.

You can have 2 to give you a bit more oomph as you say and you could expect an increase in output of 3-6 db. This is easily achievable by simply splitting the sub out from your amp using a RCA splitter and running both cables to each individual sub.

HTH Al :smashin:
 
If you have 2 subwoofers that have speaker level connection on the amp plate, you can wire each sub on the left and right speaker connections, inbetween the speakers and the amp.

The crossover on the subwoofer would control at which frequency the bass is bypassed and sent to your front speakers.

Remember the sub must have 'speaker in' and then 'speaker out' to be wired between the amp and fronts.

Hope that helps.


Ash
 
Hi and welcome to the forum :hiya:

having 2 subs doesn`t make them stereo, stereo is a dedication of 2 separate left and right channels whereas the sub channel is a dedicated sub frequency mono channel.

You can have 2 to give you a bit more oomph as you say and you could expect an increase in output of 3-6 db. This is easily achievable by simply splitting the sub out from your amp using a RCA splitter and running both cables to each individual sub.

HTH Al :smashin:
Thanks! This is what I already knew, but as stated I would love to learn how does the wiring and the such change if I indeed wanted the left and right subwoofers to play their own separate stereo channels, just like the actual front speakers do. I'm not trying to achieve the super low frequencies (hence the size of the subwoofers mentioned in original post) that don't seem to be coming from any particular direction, but to enhance the cello, bass, and other low-tone instruments in the recordings which I'm currently enjoying, since the relatively small woofer elements on the EVOs aren't enough to deliver immersive pressures to the lower end of the soundscape.

Thanks for the info, Ash_May!
 
A subwoofer is an speaker like any other. most subwoofers are active subwoofers just like active speakers. Feed line level into a Sub and you will get sounds only low frequency ones as dictated by the Xover.

The .1 LFE channel in surround sound is different to a normal signal as it is encoded with all LFE effects if you wire 2 subs with RCA Left and Right feeds respectively you will only get the left and right Low Freq sounds of each respective channel.

Your Onkyo doesnt have pre outs so you will need to use speaker level connections as Ash stated to get discrete sub channels
 
I am tagging on to this thread as it seems you understand the how subwoofers should be connected. I have an Onkyo TX-NR801 receiver with pre amp outputs which I would like to connect to 2 subwoofers and I think I understand how to do this using the pre amp output connections. However, my question is this, will I get the .1 subwoofer content from Blu-Ray discs if I am using the pre amp outputs? It seems that the .1 content is probably only sent to the subwoofer output on my receiver and in order to get the .1 content to my subwoofers I must connect my subwoofers directly to my receiver's subwoofer output. Is this correct?
 
hi space

if you do connect the subs via pre-outs, (left & right)
you can still have the .1 so to speak

you will just have to go into your amp menu and set bass out to main, not sub or both, i think this will solve it,

however, i could be wrong but i cant see why it wouldnt work, as there is the option in the amp aint there??

hope this helps

mark
 
Thanks for your comment.

You are probably correct. I have option of specifying my speaker configurations of being with or with subwoofer and this will probably direct .1 content to my left and right speakers if I indicate my configuration does not have a subwoofer.

This should be easy to test by simply disconnecting the left and right input leads from my receiver while leaving the .1 input connected and checking to see if I have any output at all from the receiver's left and right pre amp outputs.

Spaceman
 
Did anyone set this up and have any feedback on how it worked out? I am interested in the results with running bookshelf speakers through subs for stereo vs using an RCA splitter for 2 sub mono. Thanks.
 
I'm wondering what the point of stereo subs is? My (admittedly limited) understanding is that the sound frequencies subs deal with are pretty much non-directional. To enhance cello, etc using a sub, only one is needed? And if you are concerned about higher frequencies, wouldn't it be cheaper and acoustically more effective to replace the front pair with something with more low end? The only times I've seen multiple subs mentioned is to deal with the acoustic properties of a space or to get round domestic prohibitions...


You could raise the cross-over to a point where you'd get a stereo effect from the subs, but then would you be getting the best from any of your speakers?

This is genuine curiosity - I'm still putting my 5.1 system together and now only have the sub to get.
 
Last edited:
I've been reading everything I could on the subject, but info is few and far between. I did read a post where a guy was talking about showing how you can tell a difference between stereo subs and 2 mono subs, but clearly stated that the difference is slight. So I figure if one of the guys in the "for" camp for stereo subs states that is a slight difference from 2 mono subs, I am not going to worry about it. I just happen to have bookshelf speakers for the fronts and 2 subs, and was curious about this configuration option. I already have the RCA splitter, and that is what I originally had planned for the 2 subs. My receiver has Audessey and getting the 2 subs calibrated for mono will be a big enough hassle anyways. I may try this configuration some day after the fact if I get bored though, still curious about it.
 
I'm wondering what the point of stereo subs is? My (admittedly limited) understanding is that the sound frequencies subs deal with are pretty much non-directional. To enhance cello, etc using a sub, only one is needed? And if you are concerned about higher frequencies, wouldn't it be cheaper and acoustically more effective to replace the front pair with something with more low end?

This, imo, pretty much says it all.

Stereo is designed to give seperation and imaging between different instruments etc.
I fail to see the point of twin mono subs, given the non-directional sound.

Much better to get one better sub, unless you want two to try and give better room response.

And if it's bass (not sub bass) that's the problem, as suggested invest in better speakers.
 
Stereo is designed to give seperation and imaging between different instruments etc.
I fail to see the point of twin mono subs, given the non-directional sound.

Much better to get one better sub, unless you want two to try and give better room response.
Badger (Hi, BTW :)) you mention something that has been occupying some of my time and thoughts lately and it prompts me to commit to a Russ Ramble. For those easily bored, look away now.:rolleyes:

Whilst I agree regarding one better mono sub in place of two inferior examples, there comes a point when the only option is doubling up - I couldn't really justify a single 200L box in my room at any price, but a pair of 115L jobs disappear quite nicely, thankyouverymuch.

What is new is that I've just spent some time with a receiver sporting stereo (not just dual mono) subwoofer pre-outs and it's quite distinctively different to a dual mono output containing the sum of the total information. It makes sod all difference with studio recordings and electronica where there's no real sound stage, but with acoustic instruments that have a real position in space and deliver high order harmonics, even when the fundamental is in the sub-bass range, it seems to deliver a more spacious sound stage with a greater sense of the natural acoustic. The other aspect is that even if the ear is poor at discriminating the direction of certain frequencies, the body as a whole is pretty good at feeling the direction big impacts emanate from. The huge drum rolls in Dire Straits' 'Private Investigations' seem to occupy the room from wall to wall and not just between the speakers is one example that springs to mind.

As I've gone for two subs either side of the room and they're roughly equidistant making channel delays a non issue, I've been playing with using higher crossovers; up to 120Hz in fact. This isn't just to increase power handling (although it helps), but was as a result of trying to alleviate floor bounce. Floor bounce? It's the cancellation you get at the frequency that corresponds to the extra distance covered by sound output from the bass/midbass driver of your stereo speakers. The sound that 'bounces' off the floor creates a destructive interference with the direct radiated output and it happens at a number of frequencies. At the lower frequencies affected, the dip in the power response is wider and deeper and audibly a lot more obvious, although as it's one of those things most people have always lived with, it's not really noticed.

I was reading about this phenomenon and noted the example of floor-standers where the dedicated bass driver in a 2.5 or 3 way design was positioned as low as possible to minimize the differential path lengths and thought 'hang on!" We've all basically got at least one bass driver right on the floor and so I set about finding if it was a practical solution.

The measured response of my speakers shows about a 3dB dip at 140Hz, spanning 120 to 160Hz and so I simply EQ'd the subs flat with a full range input (easy with DIY subs) and simply turned up the crossover one step at a time until the dip disappeared. I wasn't hopeful given the high frequnecy the dip was centred on, but it turned out that a 120Hz crossover was perfect, but 110Hz was near as dammit indistinguishable and 100Hz notably better than either 80 or 90Hz. The audible effect was a notable extra tunelfulness and warmth without increasing levels and a much increased mid-bass kick with music and of course it all goes a bit louder with a bit less strain. Nice.

Now I must emphasize that I am running two subs either side of the main stereo speakers with drivers that were chosen very much because of their clean upper bass output. Other subs may not allow a crossover that high due to their natural limitations (regardless of where the sub's crossover is set) and I am using both channels of the BFD to EQ the subs independently, not as a sum of the combined output, so it's all very much conducive to being run as an extended stereo pair. However I would suggest those with a single good sub placed somewhere in between the front speakers may find that for stereo music at least, it's worth trying out. As ever, YMMV.

What I don't want to do is fog the one good v two lesser subwoofer debate although I fear this one will become blurred by the box tickers and feature counters. The problem is that as more receivers deliver 7.2 outputs, the rush to put a plug in every output to satisfy pub bragging rights will overwhelm the quality argument. Two inferior subs will become the norm in much the same way as people with 7 crap speakers shoehorned into a room assume that it's the ultimate in surround, when those in the know are getting a superior experience with 5 better examples with space to breath.....

Russell
 
Hello mate :smashin:

Very interesting, but having had a quick read, a bit heavy, given I'm watching a film combined with the obligatory things that go with that (beer) :D

I'll have another look tomorrow and respond (if indeed I can :rolleyes:) :)
 
Russell, just joined so I could thank you for your post. I have been searching on this topic and it is incredible the irrelevance of other replies I have seen. I saw one topic where the question was specifically whether stereo subs make a difference. In 12 pages of replies, all but one post even remotely addressed the question in any way.

I wonder whether it is stupidity, ignorance or perhaps people who own mono subs do not want to know whether stereo is actually detectable after spending a lot of money on their setup.

Anyway, your post is extremely helpful. Not many can experiment the way you did so wonderful to hear about the experience from someone who has tried.

My interest is for setting up a high quality sound system in a car. I plan to put subwoofers either side below the rear seats so this point was important in deciding whether to get two channel or mono amplifier.
 
You can run true stereo subs with a AVR/processor which has only mono sub output by:

1. setting a x-over in the AVR/processor but not connecting anything to the sub output, and
2. taking line outs from a suitable output (eg the Tape or Monitor output) and feeding those to the subs.

The subs will either need to be traditional active subs with their own crossover control, or the line level output would have to be put through an external crossover, either way the subs' crossovers should be set to the same value as set in the AVR/processor.

edit: this would work for music, anyway. For film, the LFE channel would be missing :(. I don't think there's any way to distinguish between the "LFE" and the crossed-over bass.
 
Last edited:
A couple of points:

A low bass speaker position is also useful for achieving maximum floor gain. The output is effectively doubled as a result of the first reflection. There are no losses to the reflected image at low frequencies so the ear hears two drivers closely coupled to each other. Direct and reflected. Handy for bass reinforcement with OBs which have a high natural roll-off point unless provided with a very large baffle. My own system must be unique in having no first reflection. This is due to having an open stairwell between my chair and my speakers.

Stereo is not possible with dual mono as a result of splitting a mono signal into two channels. The stereo information must already be in the two channel signal going to the two subwoofers. (or speakers)

Since normally the speakers steer the bass imagery many listeners will not notice any "real" stereo information in the deep bass. Not even if they could wire up two subwoofers to play in "real" stereo. Many recordings do not contain stereo information because they are a multi-miked and the results knitted together electronically to present a stereo image on steroids. The speakers steer the bass and everybody thinks they are hearing great stereo.

A minimalist (crossed microphone pair) stereo recording might well contain stereo information at all frequencies. Most recordings aren't stereo and wont provide any useful advantage over mono (or dual mono) sub-bass unless you collect your music entirely by reading the sleeve notes by looking for crossed-pair recordings. Good luck with that. ;)

Putting your sub-bass speakers in the back of the car (or room) will result in time delays and phase cancellation at certain frequencies. These will depend on the different path lengths to the ears. I doubt it is worth pursuing real stereo in such a layout. The speakers will steer the bass imagery (as usual) requiring no special effort to achieve "real" bass stereo by duplicating subwoofers. Better to build one high quality subwoofer which can actually play tunes. Then just let the speakers steer the bass as usual.

By using a dual mono, active crossover one can split a full range (two channel) stereo signal at any chosen crossover frequency. The four channel stereo output is fed to dual speakers and dual subwoofers. Provided the matching L&R subwoofers are close to the main L&R speakers "real stereo" is available if the source material has stereo information present. Only then will stereo be heard as nature (and the producer) intended. One must be careful not to confuse matters by playing the Left bass with the Right speaker channel and vice versa.

One can quite easily use high level connections to two subwoofers and obtain stereo bass. The downside is that the speakers play full range unless the potentially inferior, onboard, subwoofer crossover is used to feed the speakers.

One should not arrange two subwoofers for the first time, feed them with stereo signals and think you are enjoying full range stereo. The sound of two subwoofers is likely to very different to a single one. Particularly if the single one was placed off axis to the listening triangle. Where full range stereo is sought then it behoves the system builder to arrange the subwoofers sensibly. Then to feed the subwoofers (and speakers) with a real stereo signal.

The question remains whether it is worth pursuing sub-bass stereo. With my (very) offset single subwoofer on the left my ears are easily fooled into thinking that the bass is precisely placed across the entire sound stage. The speakers do all the steering despite being rolled off at 80hz.
 

The latest video from AVForums

Is 4K Blu-ray Worth It?
Subscribe to our YouTube channel
Back
Top Bottom