Subwoofer questions from a newbie

[ChrisJam]

Hi, I'm a new member.

I got my first subwoofer this week, the Yamaha YST-SW315 (20-160 Hz), and added it to this system:

Yamaha HTR-5280 amp (equivalent to the RX-V800)
Eosone RSF-200 main speakers (bookshelves, 48-20,000 Hz)
No center or surrounds yet

I plugged the sub into the amp's subwoofer output. The cable goes from there to the sub's Input2/L socket. With the Yamaha amp, that means that I activated a frequency cut-off circuit at 90 Hz, sending signals 90 Hz and below to the sub, and freqs above that to the mains. My amp's subwoofer menu option is set to sub only, not both sub and mains.

Before getting the sub, my mains did well with most music--I love my Eosones!--but distorted when DVD movies produced extra-low tones--explosions, crashes, etc. The mains were set to large before getting the sub. Now I have them set to small.

From the research I did, I expected that the sub's freq cut-off dial would not work with this set up. After all, the amp was telling it what freqs to put out. But I found that the dial does work. Subwoofer newbie that I am, I have a few questions:

1. With this set up and with my mains set to small, if I set the sub's freq dial below 90 Hz, I'll get a gap in the sound, right? For example, if I set the sub to 70 Hz, neither the sub nor the mains would reproduce tones between 71 and 90 Hz.

2. According to my research, I should set the sub's freq dial to a little higher than the main's cutoff point. Right now I have the sub set to 95-100 Hz. Does that look correct to you, given the amp's cut-off point and my mains set to the small setting? I know that the higher I set the sub's freq, the more directional the sound will become.

3. I've read from several sources that if my sub's freq dial does work and I'm using an amp with a definite cut-off point, that I should set the sub's frequency dial to max (160 Hz). I tried this. The sub produced a wider range of tones, and the overlap with the mains seemed too big. I'm assuming that this advice is wrong for my set up. Am I missing something?

Thanks in advance,
Chris

 

[markw]

Survey says...

...Use option three.

By setting the sub's internal cross over to an unrealisticly high frequency, you are assured that the receiver is actually controlling what the sub is getting and it's the predominamt control here.

To wit: if the receiver is only passing 90 hz to the sub, it matters not that the sub is expecting up to 160 hz. All it'll ever see is that 90 hz max. If you setthe sub's xover to 90 hz (or so), you'll actually be using two low pass filters in series, which will not do the sound any good.


...good thinking on your part.

 

[mtrycrafts]

To wit: if the receiver is only passing 90 hz to the sub, it matters not that the sub is expecting up to 160 hz. All it'll ever see is that 90 hz max. If you setthe sub's xover to 90 hz (or so), you'll actually be using two low pass filters in series, which will not do the sound any good.
..good thinking on your part.

While this might confuse the poster, the receiver LFE has a slope: 12dB/oct, 18dB or 24dB. So, at 180Hz in the above example of 90Hz, 180Hz will be down that amount but 100Hz, 110Hz, etc will be passed and most likely audible. Localization steps in about 80Hz.
Double filters will just steepen the slope.

 

[Sheep]

I would keep the dail around 70Hz. My Yamaha amp uses a 90Hz fixed crossover and I can localize it when I crank it to defeat (max). I found 70Hz to be just right, and I hear no gap. The speakers and subwoofer still overlap enough for the gap to not exist.

SheepStar

 

[markw]

I would keep the dail around 70Hz. My Yamaha amp uses a 90Hz fixed crossover and I can localize it when I crank it to defeat (max). I found 70Hz to be just right, and I hear no gap. The speakers and subwoofer still overlap enough for the gap to not exist.

SheepStar

The crossover in the subwoofer should be set to as high as possible. Thid sllows the receiver to control the highest frequency the subwoofer will see.

If the receiver only sends out up to 90 (or 70, 80, or whatever), the sub will only respond up to that frequency.

 

[jaxvon]

The crossover in the subwoofer should be set to as high as possible. Thid sllows the receiver to control the highest frequency the subwoofer will see.

If the receiver only sends out up to 90 (or 70, 80, or whatever), the sub will only respond up to that frequency.

Incorrect. The receiver crosses over the signal at said frequency. Beginning at the frequency, the signal is rolled off at a predetermined rate, probably 12dB or 24dB per octave.

 

[markw]

a techniacality.

Incorrect. The receiver crosses over the signal at said frequency. Beginning at the frequency, the signal is rolled off at a predetermined rate, probably 12dB or 24dB per octave.

Yes, the crossover starts a downward slope at the determined frequency but, think about it... the LFE input on a sub (that has one) totally bypasses the internal crossover. IOW, it's seeing a full range signal that is limited only by the device feeding it.

That's my basis for setting the subs xover to as high a point as possible. Two crossovers in series are redundant.

 

[ChrisJam]

Mtrycrafts and jaxvon, thanks for your posts; I learned something. You're right, mtrycrafts, your answer went over my head. But I did some research and I think I understand it now. The answers I got from the two of you explain why I can hear some higher tones coming from the sub when I expected it only to be putting out 90 Hz and below.

Sheep and markw, thanks for answering. Sheep, I guess your sub and mains overlap because of what mtrycrafts and jaxvon said--that there's some upper frequency carry-over, even if its volume is diminished as the frequency increases.

I'll have some time tomorrow or Monday to play with the sub's settings again. I'll retry setting the sub's freq dial to max and then playing some music and DVDs to see how it works.

Chris

 

[Tomorrow]

Keep in mind that the receiver's crossover only filters the main audio track. The low frequency part of this signal (the 'redirected' bass) crosses over to the sub as has been stated by the other posters. The LFE channel is a separate channel, and is controlled by your Bass (or LFE) Out to Sub Only setting (or whatever setting you choose). This signal is limited to 120 Hz and down, by convention...standardized by the kind folks at Dolby Labs.

Also note that when you set your speakers to small, the Rx crossover is in effect and will limit the signal. When set to large, the speakers will get a full-range signal, regardless of the xover setting.

 

[mtrycrafts]

Yes, the crossover starts a downward slope at the determined frequency but, think about it... the LFE input on a sub (that has one) totally bypasses the internal crossover. IOW, it's seeing a full range signal that is limited only by the device feeding it.

That's my basis for setting the subs xover to as high a point as possible. Two crossovers in series are redundant.

If any speakers in the system are set to small, the low frequency from that channel goes to the LFE and the crossover has to be used internally, with a slope.
On the other hand, the discrete LFE channel signal itself may only contain up to 80Hz, if it is THX spec designed and up to 120Hz as posted above. So, one could have a pretty audible signal above 80Hz no matter what.

 

[mtrycrafts]

Mtrycrafts and jaxvon, thanks for your posts; I learned something. You're right, mtrycrafts, your answer went over my head. But I did some research and I think I understand it now. The answers I got from the two of you explain why I can hear some higher tones coming from the sub when I expected it only to be putting out 90 Hz and below.

Sheep and markw, thanks for answering. Sheep, I guess your sub and mains overlap because of what mtrycrafts and jaxvon said--that there's some upper frequency carry-over, even if its volume is diminished as the frequency increases.

I'll have some time tomorrow or Monday to play with the sub's settings again. I'll retry setting the sub's freq dial to max and then playing some music and DVDs to see how it works.

Chris

Thanks for the feedback. One aspect of providing some answers is that the user may do further research. You did and have a better handle on this now.

I would just put your sub crossover to 80Hz as well. The only issue is that the markings are an unknown quantity; you have no idea how accurately it is placed there, will the 80Hz be as advertised or 95Hz or 65Hz?

 

[mulester7]

Double filters will just steepen the slope.

.....thank you....double amount of chop-chop db rolloff....never a bad thing for cleanness....

 

[cheapskete OCer]

i am in the same boat with my klipsch sub and polk R50s...and how would one tell if the crossover markings are actually 80Hz and that the recievers crossover is actually putting out the 80Hz ?