Issue with Bass in my HT Room (1 Viewer)

[Dixit]

So I took this room in my basement (15x25') and turn it into a theater room with 6 seats (2rows of 3 with the back row elevated on 12" platform).

Now let me give you the basics of the room so you can understand the layout. Its got a fall ceiling setup (2x2' tiles) This was there when I bought the house so not much I could do to remove it and attempt drywalling it. The floor is concrete but then basically the previous owner put a Pergo floor in the entire room. I then basically put a nice 10x14' area rug where the seats are. The walls are 1/2" drywall (one wall is actually drywalled that is the poured cement wall for the basement) with a few doors for access to HVAC and Water Heater.

Now let me explain what I got running audio wise, I got a Parasound 5250 amp driving my Polk Setup which is a pair of RTi12s, CSi5 center, FXi5 rears, and a PSW505 Subwoofer.

Now the biggest problem I got in this room is that I just feel I get no bass, if Im near the sub like within 5' the bass feels good but not room shaking like if I had this sub in my 10x10' office room upstairs. Even my front RTi12s biamped with a Parasound 2003 on the highs and the Parasound 5250 on the highs (basically pushing 450w total) still doesnt feel like they would say if I was in a room at a Home theater store. It just feels like this room either has some major sound wave cancelation going on or I just dont know what Im doing.

Recently I got a Sunfire True MKIV subwoofer (substantially more powerful than the PSW505) and even that doesnt come close to where it was in my friends house in his room. Ive moved the sub around to placing it on the platform of the rear row of seats but then only the seat closest to the sub gets the best fee the rest almost drop of 50% or more.

Im just baffled on what or where I should tackle first. At the same time I dont think I want to drop 2-5000 in just say acoustical ceiling tiles and wall treatments if thats going to fix my problem.

Im open to anything that you experts think my problem is.

Dixit

 

[Robert_J]

Until you start measuring the sub's response then everything you do is just a guess. An SPL meter and test tones will get you started.

-Robert

 

[chuckg]

Your basement room has nearly four times the space (volume) as your 10x10 room, so naturally there will be a lot less loudness in the bass. When you say the new sub has "substantially more power" do you mean twice as much, or ten times as much? Ten times the power is only about twice as loud.

Do you find spots in the room that have loud bass, and other spots with no bass? This would be a cancellation issue, brought on by the dimensions of the room. You can try the old trick of putting the sub in your favorite chair, then crawl around the room looking for a loud spot. Put the sub there, and there's a good chance that the bass in your chair will be loud.

Other than that, it starts to wander off into black magic with room treatments.

Oh and just in case -- you didn't mean that you have big fish swimming around, did you?

 

[Dixit]

Robert_J: I do have the digital RadioShack SPL meter I used when I was trying to get the setup even through the test tone Denon receiver generates. But when you say test tones, Im assuming you mean like a bunch of different ones from like 20hz, 35hz, 50hz, etc all the way to maybe 150hz to find out what the deal with the bass is. I might have to get a CD or something with those tones.

Once I do this, what will this tell me? Will it help me figure out if Ive got cancelation going on, or too much reflection, etc?

chuckg: Well the original sub was the Polk PSW505 and its about a 300watt continuous sub and 460w dynamic. The sunfire true mkiv sub I have down there now is I believe 2700w tracking downconverter based output. So thats why I think its substantially more power than the PSW505.

When I initially placed my sunfire on behind one of my chairs on the rear row platform, it sounded great on when sitting on that chair, but move to the chair in the first row, and you lose alot of bass, it just seems the bass is only good like 4ft radius around the sub.

 

[Robert_J]

Since you have an SPL meter, all you need is MS Excel to get started. I cover the steps here.

-Robert

 

[Dixit]

So I did a full reading between 10hz and 300hz using the test tones that RealTraps.com has. I set the initial PinkNoise to about 70db. Then proceeded with the test.

My sunfire subwoofer only shows information from 10-100hz (above 100hz its out of the picture since thats the highest it can crossover at).'

Attached is a chart I made of this in Excel. It doesnt look that bad with the test tones. Didnt sound that bad either.

So only thing I can think of is maybe when the full spectrum of sound comes in its cancelling the bass in some way, or maybe im just completely wrong here.

Dixit

 

[drobbins]

Eh.. I think you have an issue. If you look below 42hz it drops off sharply until you are almost 20DB lower at 26hz and below. This is the area where "real bass" is. Bass that you feel is under about 20hz. If it were me I would set the cross over about 50-60hz and turn up the sub. Then test again. I would definitely like to see the 26hz and below at a higher DB. If that doesn't help or moving the sub doesn't help either, you may need an equalizer.

 

[Dixit]

Understandable, I see your point there and you are right below 50 is really where the hard hitting bass notes come in. Right now the sub was already cranked to max on the sunfire (+15db on the dial).

I could crank up the EQ on my receiver and try to get that lower end up higher and try the test again.

Should I run the test with just the sub running? (turn off al the mains/center/rears)?

 

[Robert_J]

Turn off everything but the sub.

I didn't look at your attachment. Did you apply the meter correction values? Radio Shack SPL meters are way off. But at least we know where they are off and can correct for it.

-Robert

 

[Dixit]

So I redid the tests. Did about 3 new tests. I did one with just the mains, one with just the subs, and one again with both on.

The first screenshot compares the intial test I did (combined mains and sub) with the 2nd time of it combined. Dramatic difference in smoothing because I made some adjustments to my denon 3805 receiver. Played around with some settings to get it to respond better.

Then the 2nd screenshot is basically all 3 tests layered where it shows the response of just the mains, just the sub, and then again with both of them running.

So it definetely sounds better.

Dixit

 

[drobbins]

A few basic questions
Just making sure - is the sub connected with the LFE output? (rca)
What is your crossover set at on the sub? on the receiver?
Currently where is the sub located in the room for those readings?
Are all the other speakers set to "small" on the receiver?
You said that the volume is up all the way on the sub, what is the sub set at on the receiver? What are the other speakers set on the receiver?
Playing a test tone, say a 25hz, is the db reading the same through out the room, or is it higher in some spots and lower in others?

 

[Dixit]

The sub is running on LFE (always had it running in that method).

Crossover on the receiver is set to 250hz (but really doesnt make any change on that mainly since the sub has a crossover at 100hz or below only).

The sub is located about 8ft from the center seat in the first row on the right. (I have two rows of 3, rear row is on a 12" platform).

All the other speakers are not set to small, I actually have the RTi12s set to large as they can easily handle frequencies as low as 30hz. The center (CSi5) is also set to Large on the receiver as its also capable of playing lower frequencies. The Denon auto setup (using the mic included) sets them to large after an auto setup as well. The rear speakers are set to small (FXi5s)

The sub volume on the sub is set to max (+15db) and the reciever after doing auto setup or manually checking the SPL with test tone through receiver is about -5.0db. The fronts are coming in at +5.0db, Center is +3.5db, rears is at +6.0db. The auto setup comes up with pretty much same settings as me manually holding my SPL meter and doing the test tones through the receiver.

When I play say a 25hz or 30hz signal and measure the SPL, from the center seat lets say Im reading 90db. If I move to the right seat (which puts me now maybe 5-6ft from the sub) it will probably go up by 5db. When I move the left most seat in that same row I can see the SPL drop to as low as 79-80db. So there is definetely a good fluctuation in the SPL just moving around the room. Closer you are to the sub the better it reads and feels when listing to music or test tones.

Dixit

 

[drobbins]

It sounds like you have things set up well. My last theater was 17' x 22' with 2 rows of seating. This is a lot of volume for a sub to fill. I did not have the $$ for an earth shaking new sub, but I did have two subs. I positioned one front center and the other rear center as outlined in this study: http://www.harman.com/wp/pdf/multsubs.pdf
This filled the room evenly with bass.

Being as you have your current sub turned up all the way, I would try adding a second if you still have your other sub. Make sure that you adjust the phase with each other. If this doesn't work, maybe a PEQ would help or others here may have ideas.

 

[Dixit]

I still do have the PSW505 sub (was looking to probably get rid of it) but now that you pointed that out I may try them both out to see what happens. Since the Sunfire is so tiny, I may put that right on the platform in the rear and then maybe put the Polk PSW505 where the sunfire is now (about 8ft right of the front row of seats).

Guess I will have to head over to RadioShack to get a Y cable for the RCA to split the LFE line so I can run it to both subs.

Dixit