Question Please explain subwoofers to me

Hmm12

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Hi,

I am a bit confused about subwoofers. I am confused in a way that I find hard to put in words thats how confused I am.

Firstly ,hypothetically let's say I have a room that's 3mx4m, in that room one 500w 12" subwoofer for argument sake can reach reference levels (115db?) cleanly. It is placed in a space that gives good bass at the desired listening posititon, with no obvious nulls or peaks, a flat desired response.

Now in this scenario, let's say I switched to a 18inch 1500w subwoofer, what benefits would one expect, besides from headroom? If the 12 inch is already reaching reference? It obviously goes louder, but would one want to go beyond reference?

In the second scenario, where one subwoofer is giving good response at the desired seating position, what benefit would adding a second, third or fourth subwoofer have? I know a second one will add some headroom as well, but I mean more notifiable differences? I understand that if multiple seating positions needed even bass that multiple subwoofers would be a good idea. But what if its just a single space?

I see people having 10 or more subwoofers in a home cinema, but I don't understand why? To me that sounds like playing speakers way louder than 0db, I know it's not all about loudness, but if two subwoofers are both calibrated to reference what benefits will a bigger or multiple subwoofers have?

Il leave it at this for now, enlighten me please.

Thank you
 
Firstly a 12 inch 500w subwoofer wouldn’t be able to reach reference levels cleanly in a normal room with a flat response down to below 20hz. The benefit of a more powerful subwoofer is that it is less stressed and more capable of producing bass up to reference levels without distortion. It takes a huge amount of power to produce bass down into the infrasonic frequencies and smaller less powerful subwoofers simply can’t manage it. That is why people get large powerful subwoofers. If you hear a 12 inch subwoofer maxing out, a lot of what you hear is distortion. Get a pair of 18s in there and there is no/far less distortion. The bass has a lot of power but isn’t loud, distorted and unpleasant to listen to, it’s just clean and powerful.

The reason for multiple subwoofers is that it is rare to get a flat response with no peaks or nulls from a single subwoofer. Multiple subwoofers flatten out the frequency response.
 
Great question, it could be the start of a great debate :smashin:

If the hypothetical 12 inch 500 watt sub, is achieving a flat frequency response at all of the listening positions, at the loudest volume that you want to listen at, with no clipping or distortion, then, goal is achieved. Adding more headroom or more subs will be moot, as you don't need it.

The point is that if you really accurately measure what that sub is doing, it probably isn't delivering a totally flat response, and it may not be playing cleanly at the maximum volume that you need it to.

More subs give you more even bass, less nulls and peaks, and more volume. Plus bigger drivers and more amplification also give you more volume.

But, there does come a point where you cross a line and just have a load of additional headroom and bass potential that can never be enjoyed in an average sized room.
 
Thank you for both answers.

That's where I was getting confused at. Ofcourse the 12 inch could be any size, as long as its achieving desired reference levels results for a given room, then an upgrade to a bigger sub as u said won't achieve more.

Because I keep hearing this, that u can never have too much bass or bigger is always better, but I guess there comes a point where you have reached bass saturation(if that's even a thing) for the space your trying to pressurise and any more or bigger will be a waste of money?

To wrap my head around it, because a subwoofer is different to normal speakers I suppose, in that to hit reference it needs to be able to play cleanly at 115db? But at what frequency? Is this an average of its operating frequency band? Let's say from 15hz to 200hz? Because I doubt it would be able to play 115db at 15hz?

Also by adding a second sub the biggest benefit is more bass at more places in the room and filling in nulls, that makes sense. The second sub will also mean they can play louder, 3db increase is what I keep reading, is this around a 50% increase? Would this 3db be roughly that at all the frequencies? Instead of 102db at 20hz it can now play at 105db with two subwoofers?
 
You’re definitely right, there is a point where you’ve got enough bass and don’t need any more. However that point is not easy to get, which is why people buy or build multiple large subwoofers. The thing is getting the higher frequencies playing at a loud level is not as hard as getting the low frequencies, down to 20hz and lower at a decent level. That is where you start to need big power and lots of cones.


To find out what’s going on in your room you need to measure your subwoofers response with a mic and some measuring software. You want a flat graph from ideally single digits up to 120+Hz. That is not an easy thing to get. For example I had with one sub a dip in the frequency response at 30hz (a null) and a hump at 50hz. This can be because the bass is bouncing off the walls in the room and at the low frequency is cancelling itself out and at the high frequency is being boosted. You can calibrate this out to some degree but calibration can only do so much. If you put another subwoofer in the room at a different location, you may be able to cancel out the negative effects of the first subwoofer so when measured the null and peak are flattened out and the response is more even. I put another sub at a different location which when measured had the peak at 30hz and the null at 50hz. The two when measured together worked out and overall response was flatter. Not perfectly but an improvement, then I used the room correction from my receiver and the results were even better. I am building some smaller subs so that I have more flexibility in placement to get the response even better though (hopefully) and also to boost the lower end even more.

It is not always as simple as 3 or 6db increase across the board as the increase depends where they are in the room relative to each other.

Hope that helps to some degree.
 
That was useful thank you for your explanation.

Now to apply this. In my 3.12 by 6.67 room I am really struggling to get the right bass.

Currently I am using 2x svs pb16 ultras, I also have a SVS pc2k.

When running the 2 pb16s I am having a null at 40 to 45 hz that I cannot get rid of. Both subs are placed front corners of the front wall.

Firstly what would be the best way to run these? I am using a marantz 6011, would it be better to calibrate them using both independent pre out sections of the avr, or running both using a splitter and using only one pre OUT? When done independently the sub gain is significantly different compared to when I run them as dual MONO. Around -27 on each sub when run independently vs - 34 when run dual mono on the sub gain.

I also tried running all three subs together with the svs pc2k placed in the corner at the back of the room, according to the marantz app the graph looked a lot smoother that way, and the null at 40 is a bit better but still not gone.

What confuses me the most is that when I only run 1 pb16 I find it to be better than the other 2 scenarios. I mean the bass doesn't sound as smooth as when running more than one, but it seems a lot more presense and punchier sounding, compared to running dual or 3.

I have tried crossover from 80 all the way to 120 with no real difference when running duals or all 3.

What am I missing? I like the sound of multiple subs, it's easier to listen to, and the bass is omnidirectional vs running only one but it seems to lack power as funny as that sounds.

In my case, do I have too much subwoofer my the size of my room?
 
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