Sitting in a null spot -thoughts?

gex23

Active Member
So it seems my main seating position is in a bass null spot, and i'm wondering if you have any thoughts or advice as to how best approach / correct it? The LFE is most prevelant along all walls and within 45 - 50cm of these boundaries, with the most obvious null spot occuring in the centre of the room. The MLP LFE SPL seems to be approx 6 - 9 dB lower than around boundaries and corners.

The setup itself is a basic 5.1

The room is 4.3m long, 3.4m wide and 2.4m high, with the sofa and TV being situated on the width as opposed to length of the room. It has very little in the way if soft furnishings, besides a large rug, curtains and blinds for the french doors (leading to the garden room), with the floor being laminate and all walls having no furnishings bar the odd ornament.










I've provided a crudely drawn diagram that any self respecting 4 year old could better, and some photos that look like I was half drunk while taking them, in the hope they help provide some context to the room dimensions and potential acoustic problems.



The equipment is :

Panasonic VT65 55" plasma
Denon X3400H AVR
Sky Q box
QA 3050i mains
QA 3090ci centre
QA 3020i surrounds
Monoprice Monolith 12" Subwoofer

The subwoofer was initially on the front left corner, but has now been moved to the position in the photo, which has gained a 'little' bass in the MLP.

I haven't done the subwoofer 'crawl' yet, due to its size it has limited places it can realistically go and lack of long RCA! Other options (not already tried) include :

- Behind the sofa facing sideways along the rear wall
- Far right wall (where the cat tree is)

These options would need a wireless transmitter in the form of the MA WR1 or SVS soundpath, which is possible.

Also know i'll have to consider acoustic treatments, but these will have to be limited to walls and floor - the ceilings off limits!

Look forward to your feedback :)
 

blacksheep99

Well-known Member
Have you tried REW and the room sim? Play with sub positions etc? Could give you a good indication of what is possible
 

gex23

Active Member
Have you tried REW and the room sim? Play with sub positions etc? Could give you a good indication of what is possible

I haven't got access to such equipment unfortunately - what do you recommend buying?

Re: Sub positions, it can go behind the MLP between the sofa and the wall (using the wireless transmitter solution), the far left corner (where it was originally), or on the far right wall where the cat tree / light is) - doors and sub size mean locations are limited unfortunately.
 

blacksheep99

Well-known Member
You don’t need anything other than a laptop or pc to run REW.


The room simulator allows you to simulate the response at you MLP based on sub location. You could compare the positions you mention above. You can also simulate a 2nd sub to see if that may be something to consider in the future.

HTH
 

gex23

Active Member
That's great, i'll use it tomorrow, I'm assuming I use the internal mac on my MBP?

I also have the Denon calibration mic I could use?
 

Conrad.

Moderator
You don't need a mic for Room sim. You give it the dimensions of your room, put the head where you sit (virtually, on the diagram) and then move the sub around. It'll show you roughly what the response looks like with the sub in different positions.

You'll always get stronger bass along a boundary, but it's not necessarily better. You're likely hearing a single note getting overblown, probably somewhere in the 40Hz region. Once you've got your room into room sim you can move the head around and see how the frequencies change.

I just did it for your room and there's a mode at 40Hz which becomes dominant a the walls. If you can pull your couch forward by a foot that might help you.
 

blacksheep99

Well-known Member
That's great, i'll use it tomorrow, I'm assuming I use the internal mac on my MBP?

I also have the Denon calibration mic I could use?

If you want to do it for real you’ll need a mic like the UMIK-1 which will work grand with your Mac. Do as Conrad says though and you’ll get a good idea of what is likely going on
 

gex23

Active Member
You don't need a mic for Room sim. You give it the dimensions of your room, put the head where you sit (virtually, on the diagram) and then move the sub around. It'll show you roughly what the response looks like with the sub in different positions.

You'll always get stronger bass along a boundary, but it's not necessarily better. You're likely hearing a single note getting overblown, probably somewhere in the 40Hz region. Once you've got your room into room sim you can move the head around and see how the frequencies change.

I just did it for your room and there's a mode at 40Hz which becomes dominant a the walls. If you can pull your couch forward by a foot that might help you.

@Conrad. - Thanks for taking the time to reply and use room sim on my behalf - i've posted some room response graphs below with more accurate measurements of room dimensions - hope they show you something? (it goes above my head, however i'm assuming the freq. response graphs look bad?)

If you want to do it for real you’ll need a mic like the UMIK-1 which will work grand with your Mac. Do as Conrad says though and you’ll get a good idea of what is likely going on

Cheers @blacksheep99 - i've posted the results as above - though this is for a square room rather than an odd shaped room such as mine.

I'll consider getting the UMIK-1 in the future for sure - looks like it'll prove useful!

I guess I should buy a long RCA at some point, haul the 57kg beast onto the MLP of the sofa and do the 'subwoofer crawl' - see if it reveals anything too?

So here are the results - how with the sub position, i've put it so the sub distance is from the wall to the very front of the sub enclosure (80cm), is this correct?

Here was the original position :



This is the current position :




These positions below will require the addition of the MA WR-1 and WR-T wireless transmitter, so not possible at the minute - but are feasible if look better in terms of freq. response? :

Behind sofa :



Near French doors on the right :



How bad is it looking?
 

Conrad.

Moderator
A couple of things I'd change:

It looks like you took the absorption from the front walls. Unless you know for sure that's the case it's best to leave them at 0.1, that helps a bit.

Your LF -3dB point is too high. Looking at the specs for the monolith 12" you should be using 18-20Hz in that box. I'd remove the crossover as well, you're just interested in the best sub location at the moment.

Any chance you can close that door? If you can then the room becomes sealed and you can get a decent response with the sub behind the couch.

This is with the door open:
1604946649703.png

And this is with it closed (but with the sub in a slightly different location):
1604946716736.png

Neither are terrible and both should be eminently correctable by a half decent room correction system.

Sub crawl isn't particularly useful but there's no need to rush out and buy an Umik-1, unless you have a need.
 

gex23

Active Member
A couple of things I'd change:

It looks like you took the absorption from the front walls. Unless you know for sure that's the case it's best to leave them at 0.1, that helps a bit.

Your LF -3dB point is too high. Looking at the specs for the monolith 12" you should be using 18-20Hz in that box. I'd remove the crossover as well, you're just interested in the best sub location at the moment.

Any chance you can close that door? If you can then the room becomes sealed and you can get a decent response with the sub behind the couch.

This is with the door open:
View attachment 1398021

And this is with it closed (but with the sub in a slightly different location):
View attachment 1398022

Neither are terrible and both should be eminently correctable by a half decent room correction system.

Sub crawl isn't particularly useful but there's no need to rush out and buy an Umik-1, unless you have a need.

Thank you for breaking down the details - that makes sense, I just assumed (incorrectly) to put the crossover in.

And yes the door can be closed so that's not an issue - the only issue I have there is hoping the wireless transmitters work as advertised :) (or a long RCA cable under the rug lol)

Sub crawl sounds like it's over-rated and cheers for the advice re: Umik-1!
 

Conrad.

Moderator
Long sub cables can be had pretty cheaply. I use amazonbasics for my four subs, the longest pair are the 15m ones and they work fine. You'll have less trouble and less latency with a cable if you can do it.
 

gex23

Active Member
Long sub cables can be had pretty cheaply. I use amazonbasics for my four subs, the longest pair are the 15m ones and they work fine. You'll have less trouble and less latency with a cable if you can do it.

@Conrad. - Thankyou for the advice - I ordered just that, a 10m Amazon Basics cable (they actually look pretty decent!) to go under the rug directly to the receiver.

I hope that positioning it behind the sofa will improve response?

Cheers :)
 

gex23

Active Member
Moving the subwoofer behind the sofa has made a big of difference - I didn't realise just how capable these Monoprice Monolith subwoofers are🤯

Big thanks to @Conrad. and @blacksheep99 for taking the time and having the patience to advise me here - it really is appreciated 🙌
 

The latest video from AVForums

Podcast: Q Acoustics Q3030i, Humax Aura, Roku Streambar & WandaVision Reviews and more...
Top Bottom