"Dialing" in a sub

I see all the posts here about people that just added a new sub and talk about how they finally got it to properly mesh with their system. I just put together my new system (my first), and I don't think I have it down.

First, my system is Acoustech fronts and center (still waiting to get the surrounds), a Cadence xsub, and a HK AVR 630 reciever.

My problem is that the parameter space is just too big to work with. I thought that I would only have to adjust the crossover and the volume on the back of the sub. However, the reciever also has independent crossovers for each of the speakers. The BIC website lists the frequency response as going down to 35 (fronts) and 55 (center). I figured these numbers were going to be on the optimistic side so I set the reciever crossovers at 60 and 80 (I think). The sub crossover started at 80, but later I tweaked it up to 90ish (would this even do anything or would it be overridden by the reciever?)

Another problem is that I just don't know what it is supposed to sound like. I've never visited the home of an audiophile, so I have no basis for comparison. The music I've played so far has been classical (with very little low frequency), and some modern music off the urban radio station (new to the area, so I don't even know the radio stations yet). These tracks present opposite problems, because modern music tends to strongly over-emphasize the bass. I don't want my system to sound like the Imapala on the street with the rattling trunk (ten years ago I would have, but not anymore), so I tweaked down the sub volume until it sounded like it blended. But then I popped in Monsters Inc. (there was a long review here about the xsub where they guy got all excited with the scene where the girl cried), and I was hardly impressed.

And I haven't even started to talk about the variable of sub placement.

Any pointers would be appreciated.

"supposed to sound like"

Taking preferences out of it, you can use a HT setup DVD like Avia along with a sound meter to set up your sub/audio. Then try to get as even a response as you can for the subwoofer sweeps.

BBigJ said:

The BIC website lists the frequency response as going down to 35 (fronts) and 55 (center). I figured these numbers were going to be on the optimistic side so I set the reciever crossovers at 60 and 80 (I think). The sub crossover started at 80, but later I tweaked it up to 90ish (would this even do anything or would it be overridden by the reciever?).

Click to expand...

Firstly, the numbers shouldn't be optimistic. If the specs say the speakers accurately go down to 60Hz and 80Hz, then they should accurately go down to 60Hz and 80Hz.

You shouldn't really have the crossover, either receivers or subs (see later) less than this, as it implies that you are directing frequencies to the speakers that they cannot accurately handle.

If you are using the receivers crossover, then you should set the subs at max. By setting the sub's crossover to max, it will play everything that it get's sent up to that maximum frequency. However, setting it to max effectively makes it redundant because you are already controlling what is being sent to it with the receiver's crossover setting, so that even though the sub would play frequencies higher than you'd like it to, it's not being sent frequencies higher than you want it to.

See?!

Regards

BBigJ said:

I don't want my system to sound like the Imapala on the street with the rattling trunk (ten years ago I would have, but not anymore), so I tweaked down the sub volume until it sounded like it blended.

Click to expand...

That's definitely something to keep in mind. If the bass sounds like nothing more than boom, boom, boom and you can easily determine that the sound is coming from the sub, then the setup is not correct.

My problem is that the parameter space is just too big to work with.
You must be a programmer or mathematician. It's not that bad, really.

First, you are going to be using the xover settings in the receiver, so turn the xover on the sub all the way up or disable it if the sub allows that. See, one variable eliminated already.

There is some debate on whether or not it is useful to have separate xover frequencies for each channel. Set them all to 80 Hz as a starting point and then after you've gone through the procedure you will have gained some experience on the process and could re-visit individual settings for each channel, if you choose. Two variables down.

Now you are left with 3 variables: the sub volume control position, the subwoofer channel level on the receiver, and sub placement in the room.

- Generally, you start with the sub volume control at 1/3 to 1/2 the way up.
- You start with the subwoofer channel level on the receiver at zero.
- Generally, the sub works best in a corner or near the front speakers - so start there [furniture placement and room layout may dictate where you can place the sub]

The goal is to integrate the sound of the sub with the other speakers and that means matching it's level with the other speakers. The internal test tones of the receiver and an SPL meter is all you need. You can do it by ear, but the results will not be as accurate as using a meter. As the tone plays in each channel, you adjust the channel trims on the receiver so that the SPL is a level of your choosing (Dolby Reference Level = 105 dB, so when the meter reads 75 dB, you are at that level because the internal test tones are at -30 dB).

To get the sub level to read 75 dB on the meter, you can adjust either the sub volume or the sub channel level on the receiver. You may have to go back and forth between the two settings to get the level you want. I would try to keep the receiver's level >= 0 because if it is too low, the auto-turn on feature of the sub may not work reliably (that's been my experience anyway). So, if the sub level is too high, try turning down the sub volume control a bit rather than decreasing the receiver level to below zero. Remember too that if you change placement of the sub, you need to do the calibration again.

Once you get the hang of it, you can start messing with different xover's for each individual channel and redo the calibration procedure until you get it set to your liking.

You must be a programmer or mathematician. It's not that bad, really.

Click to expand...

Physicist actually

Thanks for the help. I suspected that the reciever ought to supercede the sub crossover, I just wanted to hear that confirmed. That makes things much easier. So if the reciever does a decent job handling the crossover (big if? or not?) I'm really just down to one variable, the volume (adjustable at the sub or in the reciever).

Currently the sub is sandwiched between the tv stand and the left tower. That tower is only 18" or so from the corner of the room (the tv is on the far right side of the tv stand, so it isn't as cramped as it sounds). So it sorta fits both of your criteria. When I get a better ear, I'll try moving it around.

El pollo suggested using a test DVD. Is there any such track that I can download and burn to CD or DVD for testing? That sounds like it would help a lot.

I would just use the test tones in your receiver and purchase a Radio Shack SPL meter for 35.00. This should do the trick if you only want to set the levels.

Otherwise the DVD would be the way to go due to the video calibration tests it offers.

i'm no calibration expert. I purchased an SPL last weekend, calibrated my 5 speakers to 75db, pretty much everthing was in +/- 0 range. The sub was at -10 and still 6-7db too high. I turned the gain down to nearly 0 to get it w/i 3 db. I then tried several DVDs and 5.1 DTS/DVD A mixes. It just wasn't right to my ears. During playback I bumped the sub to -3 and it sounded great.

I think most people's ears like the dramatic bass. I will re-calibrate again, but set the damn system the way it sounds best to you. You can always change it back...

BBigJ,

For sub placement, a neat trick is to place the sub at your listening position, playback a number with good bass and crawl (on all fours to get your ears at the sub height level) to various places in your room.

Once you have found the best sounding area (an area which may be deemed acceptable from a practical standpoint), put the sub in that new location.

Then calibrate the entire system with a SPL meter.

I havn't seen any mention of phase control. If you havn't already, try adjusting the phase control on your sub while having the SPL meter at the listening position to see which setting gives the highest reading (you could also do this by having someone else adjust the phase while you listen at the seat for the best output).

What this does is help time align the sub to your mains. If the sub is out of phase with your mains you will have a cancellation of bass around the Xover frequency where both the sub and mains are out putting the same signal, in effect lowering the overall SPL around these frequencies.

The reason for the need to do this is 2 fold:
1) The sub is seperate from the main speakers and can be placed at different distances and different places in comparison to the mains, this in itself can cause a time delay. But even if the speakers are physically aligned you still have the 2nd problem to overcome

2) All Powered subwoofers have internal amplifiers and electronics which slow down the incoming signal. The resulting time delay can vary from sub to sub.

This time delay should be accounted for by adjustment of either 'Phase Control' at the Sub or in the Receiver settings with 'Time Delay' or 'Speaker Distance'. This is why Receivers with Auto Room Eq's and such will set the Sub distance further away then it actually is, hence the receiver will send the signal to the sub slightly before the mains and because it is slowed down through the subs electronics the sound reaches your listening position at the same time(In Phase) as the sound from the mains. Personally I think this should be done at the receiver.

Hope this helps
Cheers

I didn't realize the SPL's were so affordable. I'll consider that.

I hadn't messed with the phase control because my sub is basically in the center of my viewing space. I'll fiddle with it to see if I'm getting any interference.

I've settled on 40Hz on the XSUB setting, phase at 0, and gain/volume at the 12 O'clock position. It's a small enclosure IMO, and needs the help of corner placement as well as lower frequency tuning to sound great with tv/dvd's.

The sub sounds fantastic, and shakes the entire downstairs (I get yelled at by the wife nightly ). It took awhile to get it dialed in properly, but that's the setting I currently use. The kids like those INXS, Think you can dance, etc... specials, and the sub really adds to the shows.

My towers are set to LFE+Main, so the gain on the sub needs turned up to compensate. The mains are crossed over at 60Hz (they claim to go down to 35Hz, but IMO it's probably more like 45Hz).

One other technique for getting more/better bass from your sub. Try experimenting with the distance from the wall/corner. You'd be surprised at the difference it makes. This holds true for your towers/fronts also.

Buckeye, are you using the acoustech's also?

Buckeyefan 1 said:

I've settled on 40Hz on the XSUB setting, phase at 0, and gain/volume at the 12 O'clock position. It's a small enclosure IMO, and needs the help of corner placement as well as lower frequency tuning to sound great with tv/dvd's.

The sub sounds fantastic, and shakes the entire downstairs (I get yelled at by the wife nightly ). It took awhile to get it dialed in properly, but that's the setting I currently use. The kids like those INXS, Think you can dance, etc... specials, and the sub really adds to the shows.

My towers are set to LFE+Main, so the gain on the sub needs turned up to compensate. The mains are crossed over at 60Hz (they claim to go down to 35Hz, but IMO it's probably more like 45Hz).

One other technique for getting more/better bass from your sub. Try experimenting with the distance from the wall/corner. You'd be surprised at the difference it makes. This holds true for your towers/fronts also.

Click to expand...

Don't quite understand... You have the subs xover @40 but the receiver @ 60. Isn't there a hole at 40? I was thinking of experimenting with dropping the xover to 40 and raising the gain. I don't understand why the gap. My mains go down to 40 (probably 47-48 rolloff). If there's any advantage to using your method, I'll try it. Please explain.

There's an interesting thread over on the Klipsch forums about optimizing sub settings:

http://forums.klipsch.com/forums/602013/ShowPost.aspx

The consensus seems to be that for home theater you should basically set all speakers to small, let the receiver deal with bass management, and open the crossover on the subwoofer all the way up.

Lots of reasons this makes sense, including movies being mixed with this configuration in mind and that letting the sub handle everything below 80Hz allows the mains to not have to reproduce as wide a range of frequencies which *theoretically* means they can reproduce what they do more cleanly. Of course, "how things sound" is about as subjective a topic as you can get, but having tried all of the possible combinations with my speakers (I'm using the Acoustechs) I'd have to agree that overall this sounded best.

If I recall, the manual for my 630 said that "small" speakers were those that couldn't reproduce anything below 200 Hz, whereas "large" was the 60-120 neighborhood. this means that all the Acoustechs fit into the "large" catagory. I'll look at the thread though. What sub are you using eric?

I'm using the Acoustech sub.

Here's another article from eCoustics that includes this advice:
If your speaker can't put out more than 100dB at 20 Hz, set it to "small."

http://forum.ecoustics.com/bbs/messages/34579/128214.html

This is excerpted from a book called Home Theater Hacks.

Eric is correct here. If the speaker is not good down to 20hz at a reasonable output, it should be set to small. The woofer's crossover should be set to maximum, or disabled when using a receiver with bass management capabilitites.

annunaki said:

Eric is correct here. If the speaker is not good down to 20hz at a reasonable output, it should be set to small. The woofer's crossover should be set to maximum, or disabled when using a receiver with bass management capabilitites.

Click to expand...

There are many good suggestions in this thread.

My own experience suggests that it is also a matter of personal (sound) preference and general system issues such as the performance qualities of the speakers. Admittedly, I am not familiar with the HK amp or BIC + Xsub speakers. It is probably a good 'rule of thumb' guideline to set speakers up thusly...but it is that, a guideline... and one's ears should be the final judge.

You can see my system in my signature. AverageJoe and I sat and tested a myriad of settings with my equipment and both agreed that the fronts set to large with LFE out at the preset crossover developed a far richer, more complete sound than setting the fronts to small. So I would suggest trying both ways. And I find that, even though at setup I used the Avia disk and spl meter, I must adjust my (receiver controlled) sub volume depending upon the source...tv/ht/music. Just my .02.

Sure is fun learning this hobby. Isn't it?!

Here is a link to help you calibrate your sound system:

http://www.audioholics.com/techtips/setup/index.php

I won't tell you exactly what to read...
but your answers are there.

I would only suggest that type of use for more seasoned hobbyists when listening to two channel only. When using the system for theater, all speakers should be set to small.