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No Sound from Sub

 

Bronze Member
Username: Ghiacabriolet

NC

Post Number: 86
Registered: Apr-04
Setup:

NAD T763 receiver
REL Strata III powered sub

I'm not getting any sound out of the sub in either multichannel mode or stereo. Previously, I had this sub connected to a NAD c350 amp and the sub worked fine.

I've got the sub's Lo Input plugged into the Audio Preout Sub1 connection on the T763, . I've verified through the menu setup that the sub is turned on in the speaker setup. My speakers are set to Large. The crossover on the receiver is set to 80mhz right now.

I'm going to try hooking up the High Input next to see if that makes a difference.

Any suggestions on what I may be doing wrong?
 

J. Vigne
Unregistered guest
Sorry, I don't know what High and Low refer to on your subwoofer. I'm going to assume that means the sensitivity of the input(?). Do you have any indication that the sub might not be working other than no sound? In other words is there a pilot light that is lit? Is there an external fuse you can check? If that checks OK, try this: Shut the sub off. Disconnect the sub cable at the reciever end. Turn the sub on and adjust its level to minimum. Just lightly and quickly touch the positive connector pin of the sub cable with your finger to hear if the sub responds in any way. If it doesn't I would say you have a dead amp in the sub and it probably has a fuse blown. You would have to take the input board off if there are no external fuses and I don't know that I would recommend that. If none of those suggestions lead to a solution the only other suggestion I could make right now is to temporarily run the sub from your speaker outputs to the high level inputs (the speaker connectors) of the sub to see what that would get you. Or have I missed the point and that is what you are about to try?
 

Bronze Member
Username: Ghiacabriolet

NC

Post Number: 87
Registered: Apr-04
Thanks, Jan. After I connected the high level input through the speakers, I am getting output from the sub now.

Also, dumb me, there is a low level input control on the sub that had been turned down. Once I turned this up, the sub responded on the low level input.

The sub manual says the low level input is best used in home theater to get a more "fulsome bass" and the high level input is best used in audio for a more "audiophile character" in stereo listening.
 

Bronze Member
Username: Oknessad

Post Number: 26
Registered: May-04
If you set your speakers to large (at least on my T753) the receiver sends no bass to the sub because it assumes you want it going to the speakers. I found that annoying since I would prefer to have the lowest frequences going to the sub since my speakers can go down to 32hz or so.

My solution was setting my fronts to small and having the sub crossover at 40hz. Is there another solution?
 

Bronze Member
Username: Ghiacabriolet

NC

Post Number: 98
Registered: Apr-04
OknessaD

Once I hooked up the hi level input on the sub, I was able to get output to it - at least in stereo mode. In 5.1, the output seems to be much less. I do have my speakers set to Large but there was also a sub setting which was set to On so I just assumed that meant the sub would be used. I'll take a closer look at this tonight.
 

J. Vigne
Unregistered guest
Ghia - Glad to hear things are working and just require some tweaking. Your owner's manual seems to be an exercise in creative writing as opposed to helpful hints. I would say in 5.1 you should just make your adjustment for what sounds correct to you at the DVD player's menu and then use your on the fly adjustments at the reciever to trim levels as needed for various source material.
OknessaD - Your solution should work just fine though I would suggest you try setting your crossover point a little higher since you are still asking a good deal of power be made by the reciever at 40 Hz. By moving the crossover point upward you will have cleaner sound from the amp and front speakers and should be well within the range of the sub.
 

Bronze Member
Username: Ghiacabriolet

NC

Post Number: 99
Registered: Apr-04
Jan,

I set up two presets on the receiver to control the crossover. I set one preset for movies and have the crossover set to 100 hz. The other preset is for music and is set to 40 hz.

But, reading your above post, this may not be a good thing? My speakers' low end range is 40hz so I thought it would be better to have the crossover set to that point. I have the sub crossover set to 40hz too.

Any comments about my settings?
 

Bronze Member
Username: Oknessad

Post Number: 30
Registered: May-04
I'll try to answer even though I'm not Jan. I think those settings are fine. Jan is correct in saying a higher crossover would present less of a load to the receiver. So, if you would set your crossover to 60 hz that would allow your speakers to more naturally roll off and let your sub pick up the extra slack.

For movies, I think 100 sounds pretty good. In my sub, I can start localizing the sound at that frequency so I have mine set to 80 hz. Alot of it is just personal preference and how faithfully your sub can reproduce those frequencies. What sub do you own anyways? I have a Klipsch KSW12 but am considering moving up to a SVS PCi 25-31 as there are so many positive reviews on them.

Jace
 

Bronze Member
Username: Oknessad

Post Number: 31
Registered: May-04
oh and another thing that I didn't see in your post...

Don't set the sub and receiver crossover at the same time. It ends up degrading the signal as sound goes through two crossovers before being produced. It would be better to either defeat the sub crossover or turn it up to its highest setting so it doesn't further filter the sound from the receiver.
 

J. Vigne
Unregistered guest
Well, I've kind of sorta discussed this in another post but I sure can't remeber where so I could just say go read this here and I would not have to type. It's not my best talent. But for Ghia I know you want to read this so you can get this running and have more time to devote to rebuilding your car while listening to music so here goes. I've stated that I think the optimal settings for levels and delays and so forth are purely what pleases the owner of the system. If somebody wants to set their levels differently than I do, it doesn't bother me. Others feel that there are some near absolutes that should be adhered to. OK, too. Since your reciever has the ability to do presets I would set one for music (maybe one for classical and another for Johnny Cash) using several discs that you feel give good representative bass performance. Do the same with your videos on another preset. Then use the on the fly adjustments on your remote to make changes for different recordings as some will need more or less bass and so forth. John A. and I have had a bit of a time with this on a querry about SPL meters. (I'm beginning to sense a proletariat there!) As you set your crossover points keep these ideas in mind. No crossover, with the exception of the brick wall filters built into some CD players and DAC's, will simply cut off the frequency above or below the crossover point. Crossovers have roll off rates that are expressed in dB per octave. Most often these values are different for the high pass and low pass sides of the crossover. Anyone need an explanation of high and low pass? You can normally find these specs in your owners manual for the sub and reciever but may have to research the answer on the speakers. If you set the X-over point at, let's say 40 Hz at the reciever, it will start to roll the frequencies above and below that point off at a specified rate. If you also set the X-over at 40 Hz on the sub it will begin to roll the frquencies above and below that point at its own rate. This will give a steeper curve than you may expect and one that is hard to determine. The suggestion then is to set the X-over point at one location only, in your case at the reciever. Set the sub for as high a crossover point as possible (usually around 150 Hz) to remove as much above that point from the sub and to keep the roll off at 40 Hz as smooth as possible. This can change since as the wavelength of a frequency gets smaller than the driver's diameter the speaker becomes more directional, hence the sense of hearing the location of the sub. On your speakers the specified low frequecy limit may be specified at, again let's pick 35 Hz, but if you look at a review with specs you will see that is a rough guess in an anechoic chamber (usually). The speaker probably begins to roll off slightly above that and depending on its enclosure type may disappear quite rapidly below its resonant frequency (ported speakers, 12 to 24dB per octave) or roll off rather gradually (sealed box, 6dB per octave). It could have a BIG impedance peak at about 70 to 125Hz and we know what impedance does to relative power. And that has nothing to do with your placement of that speaker in your room which can add as much as 9dB of additional bass reinforcement. All that is to say, in my long winded manner, that a speaker that is said to go to 35 Hz with a sub X-over at 40 Hz may or may not have too steep of a roll off. But it might not. Does that make sense? That is why I suggest the suck it and see method of using your ears. You have to determine what sounds best to you based on your system particulars, your room and set up, your musical taste and what you like. Though I can give you plenty of absolutes in audio; what you will like is not one of them. One absolute here is that bass draws tremendous amounts of power from the amp as opposed to mids and highs and the distortion from a full range speaker at 10 watts input at 40Hz is far greater than anyone would accept from an amplifier. We're talking 10 to 20% from the speaker sometimes as opposed to 0.0001% from the amp. So the more bass you can remove from the amp and speaker and pass it off to a larger amp (hopefully cleaner) in the sub and (hopefully) a driver better able to handle those frequencies the cleaner your sound will be. Can you hear it? Don't know, sorry. Depends. But in theory it works, so why not try it.
So there you go, Ghia. Hope that makes sense. If not let me know. Bottom line is I don't have an answer for you. You have to decide what sounds best to you. Then change it as you feel it is warranted by your tastes. Now, I'll give you the answer that always got blank stare when I was selling. Remember, whatever you change you will affect at least two other things.
Oh, my fingers ache from that one.
 

J. Vigne
Unregistered guest
Oh, I forgot to mention, not all subs will allow the crossover control to affect anything when you connect through a line (high) level input. Many have a fixed frequency point when you use that input.
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