ok the outputs of the 2 opamps must be summed to create a single mono channel. you need a 3rd opamp to do that. there are opamps that have all all these 3 opamps built in. i dont remember model numbers as I am too old and if I did I'd have to forget something else like my name. there is only so much that a battered old brain like mine can store.
Moi:
Before we go into the best way to deal with the problem, I must ask a couple of questions:
A) Do you have the subwoofer already built, or is all this preparation to get the electronics set up before you build the subwoofer? There is nothing wrong with that approach, I just want to know if we are dealing with an existing subwoofer or one that is yet to be built.
B) Is there any reason that the 80 Hz cutoff that your Sony DVD player provides is not satisfactory? Why 200 Hz? Generally, Subwoofers blend in best with the rest of the system the lower the cutoff. Many audio fans would consider the 200Hz cutoff too high-in fact, when subwoofers were first introduced back in the sixties, they had 200 Hz cutoffs and people found that was too high a cutoff.
It is your choice to do this if you want, but I am just curious as to why you want to bypass the DVD's built in crossover and go to the effort of making one yourself. Your front speakers, left and right, should have no difficulty going down to 80 Hz, where the subwoofer can blend in.
I am not saying you should not do what you are trying to do-give the subwoofer a 200 Hz cutoff-I am just curious as to why you want to go through the effort of doing it. Your DVD player's SUBWOOFER OUT already has an electronic crossover in it.
Before we go into the best way to deal with the problem, I must ask a couple of questions:
A) Do you have the subwoofer already built, or is all this preparation to get the electronics set up before you build the subwoofer? There is nothing wrong with that approach, I just want to know if we are dealing with an existing subwoofer or one that is yet to be built.
B) Is there any reason that the 80 Hz cutoff that your Sony DVD player provides is not satisfactory? Why 200 Hz? Generally, Subwoofers blend in best with the rest of the system the lower the cutoff. Many audio fans would consider the 200Hz cutoff too high-in fact, when subwoofers were first introduced back in the sixties, they had 200 Hz cutoffs and people found that was too high a cutoff.
It is your choice to do this if you want, but I am just curious as to why you want to bypass the DVD's built in crossover and go to the effort of making one yourself. Your front speakers, left and right, should have no difficulty going down to 80 Hz, where the subwoofer can blend in.
I am not saying you should not do what you are trying to do-give the subwoofer a 200 Hz cutoff-I am just curious as to why you want to go through the effort of doing it. Your DVD player's SUBWOOFER OUT already has an electronic crossover in it.
Moi:
I looked all over the net, but was unable to locate the Sony DVD 735 manual online. Often, manufacturers put their manuals online in .pdf form. Apparently, Sony does not.
Do you still have the manual for your Sony 735 dvd player?
If so, they should tell you on the Specification page, (usually located in the back), what the cutoff for the SUBWOOFER OUT is. I will surprised if it is not 80 Hz.
Also, in post #16, AndersP mentioned that there often is a setting on the Audio Video setup where the entire system is put into "Subwoofer Mode", where the rest of the speakers, or at least the front speakers, are cut off at 80 Hz, and let the subwoofer handle it from there. In other words, it perfectly integrates your other speakers and your subwoofer. I suggest you check that out-the sony dvd player may well have such a mode, and I suggest that you use it.
If you have any questions about how to use that mode-it might be called something else-come back here and ask.
Let us know if the have the manual. Also, let us know how it works out.
I looked all over the net, but was unable to locate the Sony DVD 735 manual online. Often, manufacturers put their manuals online in .pdf form. Apparently, Sony does not.
Do you still have the manual for your Sony 735 dvd player?
If so, they should tell you on the Specification page, (usually located in the back), what the cutoff for the SUBWOOFER OUT is. I will surprised if it is not 80 Hz.
Also, in post #16, AndersP mentioned that there often is a setting on the Audio Video setup where the entire system is put into "Subwoofer Mode", where the rest of the speakers, or at least the front speakers, are cut off at 80 Hz, and let the subwoofer handle it from there. In other words, it perfectly integrates your other speakers and your subwoofer. I suggest you check that out-the sony dvd player may well have such a mode, and I suggest that you use it.
If you have any questions about how to use that mode-it might be called something else-come back here and ask.
Let us know if the have the manual. Also, let us know how it works out.
Hi Moi,
Quick answer: Yes, the channels are already properly filtered before the outputs.
Caveat: Only for units with 5.1-ch analog outputs. Anything with only 2-ch output has downmixed AC3 into matrix for ProLogic decoding.
For Sony, the XO for the sub is 120Hz.
How? I have a Sony DVP-NC650V 5-disc DVD/CD/SACD changer. It has 5.1 analog outputs and all I need are 6 channels of amplification.
ensen.
PS: I'll post this in keltic's thread too.
Quick answer: Yes, the channels are already properly filtered before the outputs.
Caveat: Only for units with 5.1-ch analog outputs. Anything with only 2-ch output has downmixed AC3 into matrix for ProLogic decoding.
For Sony, the XO for the sub is 120Hz.
How? I have a Sony DVP-NC650V 5-disc DVD/CD/SACD changer. It has 5.1 analog outputs and all I need are 6 channels of amplification.
ensen.PS: I'll post this in keltic's thread too.
Moi,
Plug your sub out from the DVP into the spare Samsung channel, then into your passive sub. The Sony will take care of bass management. Although your DVP has internal menus to control balance, I recommend using the L/R balance on the Samsung to modify the mix between centre and sub. I find that the more you do in analog, the better things sound, because changes in volume with digital controls affect the overall dynamic range of the channel under control.
The one thing missing from your system is a single volume control. You have 3 knobs to turn and whenever you want a volume change, you have to re-balance the mains vs rears vs centre/sub each time. You should consider placing a 6-ch passive attenuator between the DVP and the various amp inputs. Once you've balance the 3 amps, you can control volume at one place.
ensen
Plug your sub out from the DVP into the spare Samsung channel, then into your passive sub. The Sony will take care of bass management. Although your DVP has internal menus to control balance, I recommend using the L/R balance on the Samsung to modify the mix between centre and sub. I find that the more you do in analog, the better things sound, because changes in volume with digital controls affect the overall dynamic range of the channel under control.
The one thing missing from your system is a single volume control. You have 3 knobs to turn and whenever you want a volume change, you have to re-balance the mains vs rears vs centre/sub each time. You should consider placing a 6-ch passive attenuator between the DVP and the various amp inputs. Once you've balance the 3 amps, you can control volume at one place.
ensen
Re: Passive line-level filter questions
A PLLXO comprised of Rs & Cs getts overly droopy above 2nd order, and once you put in a buffer it becomes an active XO. The Marchand that Ken points out is LC and will work at higher orders -- with proper care this solution has the potential to outperform any active XO.
Depends how you configure things... at some point you have to drive two inputs in parallel.
In the case of the low pass for sure. Since they are passive you need some way of adjusting levels and this is easiest at the power amp.
A buffer can be as simple as some in-line Rs.
Yes, as KW points out the input impedance need to be "larger".
dave
7V said:
A PLLXO comprised of Rs & Cs getts overly droopy above 2nd order, and once you put in a buffer it becomes an active XO. The Marchand that Ken points out is LC and will work at higher orders -- with proper care this solution has the potential to outperform any active XO.
Depends how you configure things... at some point you have to drive two inputs in parallel.
In the case of the low pass for sure. Since they are passive you need some way of adjusting levels and this is easiest at the power amp.
A buffer can be as simple as some in-line Rs.
Yes, as KW points out the input impedance need to be "larger".
dave
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