[scottrichardson]

Hey all,

I'm almost finished setting up my home theatre.

The room is 4.4m wide by 5.4m long.

In a nutshell... I have no bass at the seating position. Nothing. Registering very little from about 60Hz down to about 30Hz. See my rather crude diagram of my bass response below.

Before you ask. Yes, I have tried the sub woofer(s) in every location around the edges of the room, and also in a bunch of random non symmetrical positions (ie: one at the front left, one at the back middle). To no avail. I even placed the sub at the seating position and crawled around the room.... I found a couple of spots with average bass... placed the subs there, and still little to nothing at the seating position.

It's driving me mad, and I'm getting extremely frustrated.

Before I go and start building some super chunks. I need to know, will bass trapping actually help my situation? I don't really want to move my seats to the back of the room, as I'll lose my surround field. I just want that pressurised bass sound at the seating position. Is that too much to ask? The floor vibrates, but that's not important to me!! LOL.

If anyone has any suggestions, it would be greatly appreciated... as at the moment this is turning what could be an amazing HT into one that sounds cold and empty

Many thanks in advance.

Scott

 

[scottrichardson]

I am wondering what would happen if I was to trap the areas where I CAN currently hear the bass, which is clearly in the corners... I am thinking some super chunks in the corners to start with. I am wondering how this may affect the bass.

Am I correct in assuming that the bass is currently being reflected from the rear wall and corners, back into the room, and happening to cancel out right at the seating position?

 

[tonyvdb]

Scott, Your room as fairly box shaped and thus is causing the hole. Have you played with the phase control on either of the subs?

 

[bpape]

Weill trapping help? Yes. Will moving the seating position forward help as much or more - Yes. If your drawing is to somwhat accurate scale, you're WAY too far back in the room.

Yes - boundaries will give you more bass - but also boomy and muddy bass. Getting seating in the right place is the absolute FIRST thing you need to do before anything else.

Bryan

 

[scottrichardson]

Tony, yeah I have played with the phase switches on the subs. No luck there either.

Bryan, agreed. I would actually like to be a little further forward.. say another 1-2 feet. But even then there's still a void of bass around that whole area.

 

[dyohn]

I agree your seating position needs to be about 1m forward. Plus, it appears your two subwoofers are equidistant from the side walls, correct? Change that. Leave one where it is and move the other toward the listening area and in towards the center of the screen. Plus, try it with only one subwoofer. In a space that small you probably only need one...

 

[scottrichardson]

OK I'll bring the seats forward... not sure i can go a full meter. The screen is 130" and might be a bit TOO big sitting that close?

I am limited a bit with the front wall.. its full of gear... ie: my two mains, two subs, and an antertainment unit holding all my electronics. I suppose I could bring the right sub out of its spot on the front wall, and bring it forward and to the left a little. Won't look really nice in there, but that's not really important when the room is dark.

What sort of effect do you think the corner super chunks will have if I do that too?

Cheers,

 

[dyohn]

If the subs are "housed" in an entertainment center that could be part of your problem too as it can create almost a horn-loading effect... bass traps can help eliminate the boominess in the room and reduce room mode cancellations. They are almost never a bad idea. But first try making sure the two drivers are not the same distances from the nearest boundaries. Also you say you tried the phase switches, but did you flip one out of phase with the other and see what happens?

 

[scottrichardson]

Hey again

Sorry I should clarify.

There is no entertainment unit there yet. All I have set up atm are my mains and my subs (not the final subs that will be in the room, but smaller ones for testing).

No I have not tried one in phase with the other out. I will try that! Thanks.

Also, I'll move one out of symmetry.

Will report back with the results!

Thanks mate.

 

[Mike P.]

What subs are they?

 

[scottrichardson]

Currently the subs are little 14" cubed sealed Shiva MkIII's with 600watt plate amps from Jaycar Electronics. Using my receivers sub EQ to boost the low end.

The subs arriving on Monday are Shiva X2's in 85litre sealed boxes, powered by a behringer epx 2000 amp.

 

[Mike P.]

I had the same problem as you in a 4.5m wide by 7.5m long room with a cement floor. The solution for me was a sub on each side of the listening position and 2 subs behind.

 

[scottrichardson]

That's a lot of subs! Its annoying really coz in other areas, with that many subs running, you end up with insane amounts of low end

I'll bring in a 3rd sub from my garage (downfiring 80L Shiva mkI) and place that behind the seats, the other two on the sides.. so how that goes Tho i think I am running out of Y splitters!

 

[Andysu]

Weill trapping help? Yes. Will moving the seating position forward help as much or more - Yes. If your drawing is to somwhat accurate scale, you're WAY too far back in the room.

Yes - boundaries will give you more bass - but also boomy and muddy bass. Getting seating in the right place is the absolute FIRST thing you need to do before anything else.

Bryan

Odd if I go a little way to the back of my room where I can get some insane lows unlike Scott issues, hmmm strange but not as most of us know there are the dreaded nulls and dips and peaks up and down the whole room.

 

[Andysu]

Hey all,

I'm almost finished setting up my home theatre.

The room is 4.4m wide by 5.4m long.

In a nutshell... I have no bass at the seating position. Nothing. Registering very little from about 60Hz down to about 30Hz. See my rather crude diagram of my bass response below.

Before you ask. Yes, I have tried the sub woofer(s) in every location around the edges of the room, and also in a bunch of random non symmetrical positions (ie: one at the front left, one at the back middle). To no avail. I even placed the sub at the seating position and crawled around the room.... I found a couple of spots with average bass... placed the subs there, and still little to nothing at the seating position.

It's driving me mad, and I'm getting extremely frustrated.

Before I go and start building some super chunks. I need to know, will bass trapping actually help my situation? I don't really want to move my seats to the back of the room, as I'll lose my surround field. I just want that pressurised bass sound at the seating position. Is that too much to ask? The floor vibrates, but that's not important to me!! LOL.

If anyone has any suggestions, it would be greatly appreciated... as at the moment this is turning what could be an amazing HT into one that sounds cold and empty

Many thanks in advance.

Scott

Scott, you’re a lucky bugger mate if your floor vibrates as mine is a type of concrete and it takes a loud low frequency to jolt it! :hsd:

Lose your surround filed rubbish. If you place a few more of the same speaker along the sidewalls spaced out a bit it will increase the since of the surround.

I use up to x12 JBL control 1 for the surrounds in my room that is only 15 feet long by 10 feet 6 inches wide by 7 feet 8 inches high.

I have more or less the same issue where I might have a tone at 40Hz that isn’t as strong as its suppose to be when looking at frequency on the LCRS to LFE.1 direct on an RTA I see a common 40Hz to 50Hz those tones can be nice feeling but if they’re passing right over or underneath you, well there it is.

You’re suss it out soon your figure it out.

Have you even ran REW to see the current issues that your room is presenting with your sub and don’t forget the LCRS they maybe be canalling one or many few frequencies when playing in Dolby stereo/Dolby digital mode.

Also shifting the sofa forwards doesn’t cost penny! also lifting the sub off the floor may improve on the frequency response. Who says it has to be on the floor?

If you had the cash for second and third and forth then stacking the subs in close proximity to each other mutual coupling also standing sub on top of the other as the one on the floor may only cater for so much while the one on the top will cater for the frequencies that your are losing on the sub that’s sat on the floor.

Go to some large super size grand cinemas and you’re most likely see stacks of subs behind the screen to generate a uniform frequency response as well as increased pressure that seems real enough, well almost; it can’t make a real explosion real as the real thing would kill you instantly, now then.

If I stand to the front and crouch down to do the itching dragon and then stand back up the sine wave tone changes and it will show clearly on an SPL db meter. Yeah depressing isn’t it. LOL

Now if I placed second sub high up off the floor and spent some time balancing the sine wave tones till I’m more than blue in the face with it, it might take me days to tweak and perfect it.

 

[robbo266317]

Have you tried varying the phase of the subs as compared to the mains?
Or change the distance setting for the sub on the receiver.

Also if you can post a graph from REW it would be good.

 

[scottrichardson]

Hi guys,

I tried with REW but sadly lack an SPL meter atm, so its difficult to calibrate. I have a really nice RODE studio microphone for the actual measurements.

Anyways..... some news.

I have had a lot of advice to move the seats forward in my HT. This really didn't work for me for 2 reasons - less bass, and too close to the screen.

So I moved back instead. I'm now at about 85% of the way back in the room. I have a massive screen though at 130" so I don't feel this is too much of an issue.

On to the bass. I DO get some bass pressurisation here. But There's still a null. I ran some test tones, and created a rather basic response graph (produced by ear) to show what I am hearing. I compared the seating levels to the levels up near the front of the room where the response is pretty flat (to my ears). Please note the curve and frequencies only, and ignore the actual SPL/dBs as I just drew my curve anywhere up the volume scale as I have no way of determining the actual volume level without an SPL meter!

As it turns out.... it's slightly higher bass that I'm missing the most, between around 55 - 110Hz, and particularly between 60 - 90Hz.. where there is a lot of punch and oomph in your chest. I have plenty of response down below 50Hz to 26Hz, where my little heavily EQ'd subs start to roll off (big ones come tomorrow!). In fact, so bad is the null at 75Hz, that when turned up loud, all I hear is mechanical noise/THD!!!

Anyways... I am now feeling a little better.. knowing that my troublesome frequencies (at this seating position) are higher up the sub scale. Perhaps bass traps will have a rather positive affect at this range?

Sadly if I go back to my preferred seating position at about 66% of the length of the room, The null is MUCH larger.. spanning 30Hz - 110Hz. I just can't see bass traps affecting such low end? Unless others here personally have had positive experiences fixing low end bass below 90Hz with traps? From what I have read, traps only really work to 100Hz??? Anyone care to prove me wrong?

I'll be ordering some Bradford Ultratel insulation tomorrow, which I'll use for super chunk bass traps

 

[Mika75]

http://www.hometheatershack.com/forums/home-theater-design-construction/21966-semi-modest-home-theater-australia-2.html#post206581

Read this post I made earlier today mate, exactly what I predicted, ur subs are crossed over too early and ur missing out on that all important 'punch' :T

 

[davidburn]

The 600 watt plate amps from Jaycar have a 32hz response suggesting they would only be suited to music not ht?

 

[Mike P.]

The 600 watt plate amps from Jaycar have a 32hz response suggesting they would only be suited to music not ht?

Good catch David. The current Jaycar 600 watt plate amp only goes down to 32 hz according to the published specs.