REW - sending LF signal problem (Right and sub are playing but not left speaker?)

[moves]

I wish I knew more about this stuff so I could trouble shoot on my own even further... but I don't.

I am sending a 30Hz test tone VIA REW to my sub with an 80 crossover set in the Pioneer SC-27 AVR and the left channel is not playing anything (which is expected)... BUT THE RIGHT CHANNEL IS PLAYING BASS....

The subwoofer is also outputting a signal....

I want to isolate the sub... with an 80Hz crossover in the AVR... how is the right channel getting any signal? It should all be coming out of the sub... UGH.. any ideas?

 

[everettT]

You want no crossover, full sweep. I still highly recommend the bridged.

 

[moves]

You want no crossover, full sweep. I still highly recommend the bridged.

I am just trying to isolate the subwoofer only just for a test... why is the right channel outputting a signal and not the left channel @ 40 Hz? The only speaker that should be outputting a signal is the sub.

For the sweep, I can't disable the crossover in the AVR so just set it to 200Hz? (which is max)

 

[everettT]

I'm not sure what your trying to accomplish. Set the avr to full range no crossover. No speakers but sub. What are the settings in the crown? Dont make any changes in the crown unless every connection is disconnected from it. As I stated in the other thread you can connect directly to the crown with rca.

If your convinced that you dont want to bridge, buy a more powerful amp and run 1 channel. I dont know anyone that had done it the way you have it. It's hard to troubleshoot an unorthodox setup.

 

[moves]

I'm not sure what your trying to accomplish. Set the avr to full range no crossover. No speakers but sub. What are the settings in the crown? Dont make any changes in the crown unless every connection is disconnected from it. As I stated in the other thread you can connect directly to the crown with rca.

If your convinced that you dont want to bridge, buy a more powerful amp and run 1 channel. I dont know anyone that had done it the way you have it. It's hard to troubleshoot an unorthodox setup.

In this thread, I am just trying to send a 40Hz test tone.... just to see if the signal is going only to the sub... which it should. But it is not. The signal is also going to the right channel, which it shouldn't.

In the AVR, I can't set the speakers to full range. I can only change to small and large and SW on or off... the crossover options when the subwoofer is on are 50 - 200 Hz.

The Crown setting are input sensitivity set to .775V and the dials are turned to 9 a.m. in stereo mode.

 

[moves]

So I figured it out I think but I don't think I understand... In REW in the generator window at the bottom, There is an output option L+R, L, and R.. I had it selected as R. So this is why the right channel was active. BUT... not sure why because it was a 40Hz signal where the cross over in the AVR is set to 80Hz... REW must be bypassing the crossover in the AVR somehow.

 

[everettT]

Do you have a speaker AB on off switch on the avr? If yes set the mains to large no crossover and turn the speakers off. Or disconnect them.

 

[moves]

Do you have a speaker AB on off switch on the avr? If yes set the mains to large no crossover and turn the speakers off. Or disconnect them.

no AB on off option like the older AVR models. I disconnected the external amp that run my mains and posted my first graph in the other thread.

I was stumped on how to set up the channel level for sub only so I followed the initial set up for the mic as if I was going to run sweeps with my mains... i.e. placed the mic at the listening position and set the volume on the AVR until the SPL read 75db... then I placed the mic in front of the subwoofer and ran the sweep with the external amp that runs the mains disconnected.

 

[TLS Guy]

So I figured it out I think but I don't think I understand... In REW in the generator window at the bottom, There is an output option L+R, L, and R.. I had it selected as R. So this is why the right channel was active. BUT... not sure why because it was a 40Hz signal where the cross over in the AVR is set to 80Hz... REW must be bypassing the crossover in the AVR somehow.

Your problem is that you don't understand crossovers. Everything is working as it should. On an AVR the high pass is 12 db per octave and the low pass is 24 db per octave above crossover. So if you send a 40 Hz signal to the AVR with the crossover set to 80 Hz, then the right speaker will be 12 db down at 40 Hz. That is quite a bit of power and easily audible.

Playing each amp channel to each VC is perfectly acceptable and actually the best and safest way to do it. Bridged amps should actually be factory matched like Quad have always done. You system gets the same result as bridging, yes, exactly the same result, and is much safer. Many amps have been ruined by bridging as a slight mistake is lethal. I'm no fan of bridging and never have been. It should be avoided where ever possible. In addition those Crown amps have a very unusual connection system in bridge mode, which adds to the possibility of confusion.

 

[moves]

Your problem is that you don't understand crossovers. Everything is working as it should. On an AVR the high pass is 12 db per octave and the low pass is 24 db per octave above crossover. So if you send a 40 Hz signal to the AVR with the crossover set to 80 Hz, then the right speaker will be 12 db down at 40 Hz. That is quite a bit of power and easily audible.

Playing each amp channel to each VC is perfectly acceptable and actually the best and safest way to do it. Bridged amps should actually be factory matched like Quad have always done. You system gets the same result as bridging, yes, exactly the same result, and is much safer. Many amps have been ruined by bridging as a slight mistake is lethal. I'm no fan of bridging and never have been. It should be avoided where ever possible. In addition those Crown amps have a very unusual connection system in bridge mode, which adds to the possibility of confusion.

Thanks! I always thought that if I send a 40HZ signal where the crossover is set to 80Hz... then everything below 80Hz will be redirected to the subwoofer but I guess this is not so.... Rather, the right and left are still getting signal with a 40HZ signal with a 80Hz crossover but the signal going to the left and right channel is just weaker?

 

[lovinthehd]

Sometimes a pic is worth a thousand words for a crossover

 

[moves]

So the mains are still playing some signal just not as loud?

 

[lovinthehd]

So the mains are still playing some signal just not as loud?

Yes, speakers play below crossover and sub plays above crossover, just on slopes as mentioned. It's not a brick wall as you imagined.

 

[moves]

Yes, speakers play below crossover and sub plays above crossover, just on slopes as mentioned. It's not a brick wall as you imagined.

You mean subs play BELOW crossover and mains play ABOVE crossover no? because of the rolloff?

 

[lovinthehd]

You mean subs play BELOW crossover and mains play ABOVE crossover no? because of the rolloff?

The sub's main content is below crossover and the mains' main content above, but as you can see in the graphic the sub also plays some above crossover and the mains below crossover....the slopes "crossover" at a given point. The slopes roll off at different rates as TLS guy mentioned....depending on the type of crossover/filters used.

 

[moves]

sheesh... and I thought it was a brick wall

 

[lovinthehd]

sheesh... and I thought it was a brick wall

LOL don't worry, many people are in the same boat. You have been armed with knowledge instead of an assumption....

 

[TLS Guy]

I thank hd for showing that graph which I should have done.

Now a bit of history the crossover slopes where chosen by THX. The idea was to have the speakers sealed, so they rolled of 12 db, then the electrical slope plus the acoustic roll off would be 24 db. Then with a 4th order low pass on the sub you would have 24 db high and low pass filters.

Of course this is not the way it turned out. Most speakers ended up ported with a 24 db per octave roll off. So the crossover is not correct.
That is why I like most UK speaker manufacturers do not advise the usually recommended US practice. If the speakers are capable they should not be crossed over, but the sub gently used to fill in at the natural roll off of the mains. The sub should handle the LFE signal up to 120 Hz. I have researched and measured this, and it does result in the best measurements without a lot less hassle, and subjectively it gives by far the best musical quality. The big draw back is that there are far too many speakers that are now incapable of being driven full range. However there are plenty that are. There is nothing adverse about using a high pass filter below box tuning to prevent useless driver excursion.

I personally believe changes to practice about bass management are warranted. Current practice is not optimal in my view, and I do not follow it, with excellent results.
I only follow it if the speakers are sealed, like my Eagan system where the center is sealed and the main speakers are integrated in one enclosure with the bass mids in sealed compartment and an integrated isobarik coupled cavity bass system that handles the low frequencies and the LFE. I agree that is another unusual approach. However I have good reasons for doing what I do.

 

[lovinthehd]

I thank hd for showing that graph which I should have done.

Now a bit of history the crossover slopes where chosen by THX. The idea was to have the speakers sealed, so they rolled of 12 db, then the electrical slope plus the acoustic roll off would be 24 db. Then with a 4th order low pass on the sub you would have 24 db high and low pass filters.

Of course this is not the way it turned out. Most speakers ended up ported with a 24 db per octave roll off. So the crossover is not correct.
That is why I like most UK speaker manufacturers do not advise the usually recommended US practice. If the speakers are capable they should not be crossed over, but the sub gently used to fill in at the natural roll off of the mains. The sub should handle the LFE signal up to 120 Hz. I have researched and measured this, and it does result in the best measurements without a lot less hassle, and subjectively it gives by far the best musical quality. The big draw back is that there are far too many speakers that are now incapable of being driven full range. However there are plenty that are. There is nothing adverse about using a high pass filter below box tuning to prevent useless driver excursion.

I personally believe changes to practice about bass management are warranted. Current practice is not optimal in my view, and I do not follow it, with excellent results.
I only follow it if the speakers are sealed, like my Eagan system where the center is sealed and the main speakers are integrated in one enclosure with the bass mids in sealed compartment and an integrated isobarik coupled cavity bass system that handles the low frequencies and the LFE. I agree that is another unusual approach. However I have good reasons for doing what I do.

What about closing off ports in speakers when sealed speakers aren't involved? What about where xover is well above the natural roll off point below tuning of a ported enclosure?

 

[TLS Guy]

What about closing off ports in speakers when sealed speakers aren't involved? What about where xover is well above the natural roll off point below tuning of a ported enclosure?

The problem with closing ports is that the box size will be wrong, and unless you know the T/S parameters of the driver you won't know F3 unless you measure it. Also for a lot of speakers F3 will be far too high after port closure. The second option still leaves you with the wrong slopes as you have a second order and not fourth order high pass.

I guess the point is essence is that a crossover has to be designed case by case for optimal results. You actually could make a really good case for speakers and sub to be designed and sold as a unit. What we have now is chaotic and hit and miss. Unfortunately usually miss.