Base null in centre of room

[aoaaron]

Tempted by the second sub option as I do have room to grab another SB1000. The rest of the setup is pretty decent (Speakers are Dali opticon 2 MK2’s) so obviously want the best result after spending far too much money

If you are dual subbing, you need to budget for a tool to time align, volume match the subs etc. otherwise you can end up with some disastrous results.

 

[Cryfreeman]

If you are dual subbing, you need to budget for a tool to time align, volume match the subs etc. otherwise you can end up with some disastrous results.

Would the receiver do that during speaker setup? At least to a decent starting point.

 

[lucid]

Would the receiver do that during speaker setup? At least to a decent starting point.

Unless you're going with a higher-end AV receiver (£1000+) then you're unlikely to get anything that will deal with two independent subs, let alone EQ them as accurately as you'd get with a specialised bass-only processor.

 

[melmac]

Tempted by the second sub option as I do have room to grab another SB1000. The rest of the setup is pretty decent (Speakers are Dali opticon 2 MK2’s) so obviously want the best result after spending far too much money

What Receiver do you have? What crossover are you using? Are all the speakers the same the whole way around?

 

[lucid]

Done the sub crawl. I can find the perfect spot while crawling, swap positions and the base still hits 4ft or so Infront and behind my seating position.

That's because your seating position is in the centre of the room.

Every half- quarter- eighth- and every other even fraction of the room's length- width- and height is going to experience a pressure null. There's no real way to change that. It's the physics of sound propagation in an enclosed space.

Let's take your room length of 12ft. To find the first frequency that's going to be a null in the dead centre of your room's length we take the speed of sound in air (1130ft/s) and then divide that by double the room length. We have then 1130/24 = 44.08Hz.

Your room width is also 12ft. That will generate another room null at 44.08Hz as well. Now you're dealing with not just one bass null of 44Hz, but two superimposed on each other.

The room height also has a null, but because the the dimension is different (I'm presuming 8ft, but YMMV) then the frequency at a point 4ft from the floor level is 70.6Hz

You're not going to fix this with electronics alone. You've either got to remove or reposition the room walls, which isn't feasible unless you're doing a whole floor rebuild, or you move the seating position out of the double-sized gravity well that the room creates (potentially the cheapest solution), or do something with the bass energy in the room so that the room acts like it's bigger. For that you need bass traps - and really big ones. Even then you're only going to attenuate the size of the null rather than remove it completely.

Your two most practical and wife/significant-other acceptable solutions are to change the seating position and use some electronics.

 

[melmac]

You're not going to fix this with electronics alone. You've either got to remove or reposition the room walls, which isn't feasible unless you're doing a whole floor rebuild, or you move the seating position out of the double-sized gravity well that the room creates (potentially the cheapest solution), or do something with the bass energy in the room so that the room acts like it's bigger. For that you need bass traps - and really big ones. Even then you're only going to attenuate the size of the null rather than remove it completely.

Exactly. Something has to change physically. Either the seating position or the speaker/sub position. Sometimes changing the crossover and adjusting the subwoofer distance on the receiver can help. He didn't report back to say whether putting thick duvets on the walls and pillows in the corner has made any difference. He does realise himself that his room shape isn't ideal!!

I wonder would it be worth him trying the sub near or just behind his listening position? It would take the room out of the equation. It might lead to a few more peaks, but, the receiver's EQ should be able to solve them.

 

[aoaaron]

Exactly. Something has to change physically. Either the seating position or the speaker/sub position. Sometimes changing the crossover and adjusting the subwoofer distance on the receiver can help. He didn't report back to say whether putting thick duvets on the walls and pillows in the corner has made any difference. He does realise himself that his room shape isn't ideal!!

I wonder would it be worth him trying the sub near or just behind his listening position? It would take the room out of the equation. It might lead to a few more peaks, but, the receiver's EQ should be able to solve them.

No. Have you measured a subwoofer post EQ? AVR EQ's are awful at taming a subwoofer; especially Audyssey. You're ignoring just how bad the peaks are in terms of audio performance.


Infront of or behind... without measurement software and instruments.. you're guessing.

Its sad but you were simply wrong.

A sub crawl is decent at best but without measuring devices, you're guessing based of of of perception of sound, ignoring what makes a subwoofer sound good which is more than just perceivable SPL.


How does he.. or anyone.. even know whne to crossover?For all you know, your sub might have a gigantic null at 60 to 80hz... yet your crossover might be set at 80hz.

 

[lucid]

Sometimes changing the crossover and adjusting the subwoofer distance on the receiver can help.

The distance setting changes the relative timing of the sub bass pulses to the speaker bass pulses - its the same as phase - so I'd expect that only to alter the interaction between the speakers. When the sub is playing on it's own then phase/distance makes no more difference to the sound than pressing play/pause. Tgeres nothing for phase/distance to time against in that instance.

I'd be very surprised then if phase/distance did anything to tame the room modes excited by the sub.

He didn't report back to say whether putting thick duvets on the walls and pillows in the corner has made any difference.

Bass penetrates wooden floors, stud walls, even brick walls. A bit of hollow fibre or duck down in some bedding might absorb high frequencies, but I don't see it having the same soundwave-to-kinetic/heat-energy dissipating properties as a bass trap, so I wonder just how useful that really is for sorting subwoofer issues.

I wonder would it be worth him trying the sub near or just behind his listening position? It would take the room out of the equation. It might lead to a few more peaks, but, the receiver's EQ should be able to solve them.

Doing the room crawl gets the sub out of one of its generated bass null points.

Moving the sub closer to the seating position won't change the sound wave propagation in the room. If it was a sub that's too small for the room then it would help counter the sound dissipation over distance - make it sound louder and contribute some feeling of bass too - but with an SVS SB1000 in that size room then power and feel probably aren't the big worries.

Exactly. Something has to change physically. Either the seating position or the speaker/sub position. Sometimes changing the crossover and adjusting the subwoofer distance on the receiver can help. He didn't report back to say whether putting thick duvets on the walls and pillows in the corner has made any difference. He does realise himself that his room shape isn't ideal!!

I wonder would it be worth him trying the sub near or just behind his listening position? It would take the room out of the equation. It might lead to a few more peaks, but, the receiver's EQ should be able to solve them.

 

[aoaaron]

Exactly. Something has to change physically. Either the seating position or the speaker/sub position. Sometimes changing the crossover and adjusting the subwoofer distance on the receiver can help. He didn't report back to say whether putting thick duvets on the walls and pillows in the corner has made any difference. He does realise himself that his room shape isn't ideal!!

I wonder would it be worth him trying the sub near or just behind his listening position? It would take the room out of the equation. It might lead to a few more peaks, but, the receiver's EQ should be able to solve them.

Do you mean Basstraps?

Room treatment should be the corner stone of any HT build but again, some people can't afford it for decor reasons.

And how do you know your room treatment is working?... with a UMIK-1, REW and measurements.

 

[Cryfreeman]

What Receiver do you have? What crossover are you using? Are all the speakers the same the whole way around?

Yamaha RX-A3080, Dali Opticon 2 mk2’s fronts/centre with Oberon on walls, sides and rears. Crossover at 80 Hz.

 

[Cryfreeman]

If I move back more towards the rear wall this is an excuse for a bigger TV right?

 

[melmac]

I'd be very surprised then if phase/distance did anything to tame the room modes excited by the sub.

I was thinking of lowering the crossover. But, in this room, you are probably right, there won't be much if any difference by doing either. But, it doesn't cost anything but time to try.

Bass penetrates wooden floors, stud walls, even brick walls. A bit of hollow fibre or duck down in some bedding might absorb high frequencies, but I don't see it having the same soundwave-to-kinetic/heat-energy dissipating properties as a bass trap, so I wonder just how useful that really is for sorting subwoofer issues.

I wasn't suggesting that this would sort the problem. They aren't going to be much good for low frequencies, but, they would still change what's happening in the room, maybe enough for the guy to decide if he wants to invest in a more permanent solution. Or maybe not even a little.

Moving the sub closer to the seating position won't change the sound wave propagation in the room. If it was a sub that's too small for the room then it would help counter the sound dissipation over distance - make it sound louder and contribute some feeling of bass too - but with an SVS SB1000 in that size room then power and feel probably aren't the big worries.

I am talking about placing the subwoofer nearfield to his listening position. It won't be much good for more than two people at the main listening position though. And it definitely doesn't have any Wife appeal.

 

[melmac]

If I move back more towards the rear wall this is an excuse for a bigger TV right?

LOL, it's a great excuse!! Is your TV the only reason why you can't move your listening position back closer to the rear wall? If it's because of speakers, it's ok to be close to the rear ones. With the side speakers just on the side of your listening position?

Moving the listening position would be the simplest solution to your bass problem.

 

[Firestar_3x]

Tempted by the second sub option as I do have room to grab another SB1000. The rest of the setup is pretty decent (Speakers are Dali opticon 2 MK2’s) so obviously want the best result after spending far too much money

Very real chance of creating more problems than you solve.

Needed a minidsp 2x4hd and umik-1 to sort my dual subs out properly.

 

[aoaaron]

Very real chance of creating more problems than you solve.

Needed a minidsp 2x4hd and umik-1 to sort my dual subs out properly.

Exactly.

A second sub can cause more issues than solve then unless you have the proper tools to measure and time align them at the very least.