"Dialing" in a sub

[Buckeyefan 1]

Buckeye, are you using the acoustech's also?

No, I've got Polk RTi/CSi/FXi series for the 7.1.
Here's the specs on the towers:
Overall Frequency Response 20Hz-27kHz
Lower -3dB Limit 35Hz
Upper -3dB Limit 26kHz
Nominal Impedance 8 ohms
Recommended Amplifier Power 20-300 w/channel
Efficiency 89 dB
Crossover
(mid-high array) 2.7kHz, 12dB/octave low and high pass. 125Hz 12dB/octave high pass
Crossover
(subwoofer) 125Hz

 

[Buckeyefan 1]

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.

You would think, but the Hz control on the sub isn't an exact science, and there's quite a bit of rollover on that 40Hz frequency. It's just a parameter, not a parametric setting. The sub will (supposedly) play down to 25Hz even though the Hz control only goes down to 40Hz.

The XSUB IMO sounds best when the frequency is taken down as low as it can go. It's such a tight box with quite a bit of power, that it wants to be a punchy musical sub.

To get it to focus on the extremely deep HT bass, I've found that by dropping it to 40Hz and bringing up the gain, I can better control the deepest bass.

I'm a little bit off the beaten path when it comes to setup. I prefer to get my main speakers to sound as good as they possibly can, then add in the sub for bass (2 channel only).

For surround sound, the same applies, but I start out getting the 7 speakers to sound their optimum, then add the sub. I hate to take away from what my main speakers were meant to do, even if the crossovers take a load off my amp. That's why I've installed a pc fan over the heat sinks. So I can drive the amp and push the speakers - especially the woofers. Sure, I can take it down below 60Hz on the mains, but honestly, how deep are dual 7" woofers really going to play? And with a rollover effect, they'll put out a few Hz lower than that.

Overall, I'm very satisfied with the sound.

 

[Ron Temple]

You would think, but the Hz control on the sub isn't an exact science, and there's quite a bit of rollover on that 40Hz frequency. It's just a parameter, not a parametric setting. The sub will (supposedly) play down to 25Hz even though the Hz control only goes down to 40Hz.

The XSUB IMO sounds best when the frequency is taken down as low as it can go. It's such a tight box with quite a bit of power, that it wants to be a punchy musical sub.

To get it to focus on the extremely deep HT bass, I've found that by dropping it to 40Hz and bringing up the gain, I can better control the deepest bass.

I'm a little bit off the beaten path when it comes to setup. I prefer to get my main speakers to sound as good as they possibly can, then add in the sub for bass (2 channel only).

For surround sound, the same applies, but I start out getting the 7 speakers to sound their optimum, then add the sub. I hate to take away from what my main speakers were meant to do, even if the crossovers take a load off my amp. That's why I've installed a pc fan over the heat sinks. So I can drive the amp and push the speakers - especially the woofers. Sure, I can take it down below 60Hz on the mains, but honestly, how deep are dual 7" woofers really going to play? And with a rollover effect, they'll put out a few Hz lower than that.

Overall, I'm very satisfied with the sound.

Have you considered adding polyfil to the enclosure to increase performance. I popped the driver out of my broken XSub and there is none. I don't know enough about it yet (I saw a thread), but I'm considering it.

 

[mtrycrafts]

The woofer's crossover should be set to maximum, or disabled when using a receiver with bass management capabilitites.

If used, wouldn't you get a steeper roll off of the highs getting in there, a benefit?

 

[mtrycrafts]

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

There are a few more faces on the side that you could have used

 

[mulester7]

If used, wouldn't you get a steeper roll off of the highs getting in there, a benefit?

.....STANDING OVATION....Gentlemen, there's HOPE for Mtrycrafts with this answer....now if he would just listen to his favorite CD at reference levels with "BIG WATTS", when the slave amp transformer is only idleing, and ONLY feeding two mouths.....

 

[Buckeyefan 1]

Mule and Marty in agreement.
I think the next step is for them to break out a bottle of Shiraz, discussing the finer points of life. Yin and Yang.

 

[Buckeyefan 1]

Have you considered adding polyfil to the enclosure to increase performance. I popped the driver out of my broken XSub and there is none. I don't know enough about it yet (I saw a thread), but I'm considering it.

No polyfill, but there should have been what looks like carpet insulation lining the interior walls of your XSUB. Mine has it. I may replace this thinner insulation with acoustic baffling from PE.

The sub really isn't "boomy," plus too much polyfill will require a larger amp to reach the desired spl.

I've got my truck box about 50% full of poly in a sealed enclosure, and it takes just about everything my 924 watt class D amp can push out.

 

[WmAx]

If used, wouldn't you get a steeper roll off of the highs getting in there, a benefit?

The issues must be weighed. If the subwoofer performs poorly at the higher frequencies that will be fed through it, then yes, a steeper rate is desirable. However, in the case of an assymetrical crossover slope on the high pass vs. low pass, the summed response of the two will not be maximally flat.

-Chris

 

[mulester7]

The issues must be weighed. If the subwoofer performs poorly at the higher frequencies that will be fed through it, then yes, a steeper rate is desirable. However, in the case of an assymetrical crossover slope on the high pass vs. low pass, the summed response of the two will not be maximally flat.

-Chris

....I can go with that, WmAx, and, the lower the frequencies, the less rolloff is needed applied to a phase lapover to be inaudible, but, if it's there to be had/used, even if it's inaudible and overkill, why not?....and thanks for not saying, "mule and Marty sittin' in a tree"........

 

[WmAx]

No polyfill, but there should have been what looks like carpet insulation lining the interior walls of your XSUB. Mine has it. I may replace this thinner insulation with acoustic baffling from PE.

The sub really isn't "boomy," plus too much polyfill will require a larger amp to reach the desired spl.

I've got my truck box about 50% full of poly in a sealed enclosure, and it takes just about everything my 924 watt class D amp can push out.

Dampening performs two important functions.

(1) Increases the effective volume[for sealed boxes] or increases the effective line length[for TL boxes]. However, for ported boxes, the more stuffing, the worse the system will perform so far as low frequency efficiency. The more lossy material present equals greater energy losses of the vibrating air molecules of the air volume, thus resulting in reduced efficiency of coupling to the resonator[port or passive radiator].

(2) Dampen high frequencies, such as those 1 octave past the crossover cutoff point of a 4th order crossover, where a resonance related to box 1/2 wavelength dimensions could potentially cause audible degradation[in a band approaching the most sensitive to human hearing according to credited research]. However, if the box dimensions are substantially less then 1/2 wavelength of any frequency[x2 frequency of cutoff point for a 4th order crossover rate] that will be played through the system, then it does not seem probable that stuffing will benefit the sound quality, and with a ported system, it is optimal to use no box stuffing if possible.

-Chris

 

[Nick250]

Just a note on using a sub with music. In theory, with music, you should not notice that your sub is on, ie the sub does not draw attention to itself. The sub is however, noticed by it's absence. The sound will lose it's fullness and will sound thin.

 

[Ron Temple]

No polyfill, but there should have been what looks like carpet insulation lining the interior walls of your XSUB. Mine has it. I may replace this thinner insulation with acoustic baffling from PE..

Yep, it has the carpet pad. I do recall that it was getting pretty clean, before I sent the hummer back. I replied to your post on replacement 12" drivers. PE made a suggestion, but didn't believe I could get below 40hz out of the Cadence box. I think we'll see... A 2nd Cadence for $100 seems like a good deal.

 

[BBigJ]

Ok, this might explain my poor impression. I just tried fiddling with it, and it doesn't look like the sub isn't doing anything at all. The power light for the sub is on, but the power light for the sub's amp light isn't lighting, so it looks like the sub isn't coming out of power save. I tried several different inputs (dvd, network player, tuner) and several different options for speaker size/surround settings and nothing seems to work. I also checked the fuse on the sub and tried a different set of RCA cables. I know the sub worked when I first got the system, because I tried it before any of the other speakers arrived. Any suggestions?

 

[MDS]

What did you end up with for the receiver's sub channel level? I've had the same thing happen before when the receiver's level is too low and that is why I suggested trying to keep the receiver's level at zero or higher (and turn the sub volume down if need be).

 

[BBigJ]

I haven't even adjusted it yet. I went to adjust the levels yesterday but couldn't (I bought a refurb and HK sent me a 635 remote, so I can't figure out how to get to the auto-set feature. I emailed HK about it, but they are closed till monday.) I tried cranking up the bass in the reciever, but that didn't fix the problem. I haven't specifically changed the sub level.

 

[BBigJ]

In order to test MDS's suggestion, I just set the sub as high as I could (+10db) and the remaining speakers as low as I could (-10), cranked the bass and treble to their relative extremes, and cranked up the volume as loud as I dared with the baby sleeping downstairs. I was able to get up to a volume of -15 db (now I'm comforably watching the football game with the volume at -50) and still there was no sign of the sub coming to life.

How should I troubleshoot this? Is there a way to check if there is a signal coming from my reciever? Or a way to force the sub on without an input signal?

 

[Tomorrow]

Did you verify that your receiver's subwoofer (LFE) setting is set to "Yes"...and I don't mean just the volume?

 

[BBigJ]

As far as I can tell, there isn't a yes/no setting. But on the speaker setup screen, I have the sub slot set to "L/R+LFE". When I set all the speakers to "small" I believe that setting automatically changed to "LFE".

 

[annunaki]

If used, wouldn't you get a steeper roll off of the highs getting in there, a benefit?

Potentially, yes, I guess that could be an option. Although, I recall reading a paper or article that suggested against that, as there was the possibility of induced distortion or something along those lines. I will have to try and remember where I saw that.