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Home Theater Bypass - Subwoofer setup

Sputnik

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This is my first post, I hope it is in the right place. I want to make some changes to my setup, but cannot figure out how to best connect a subwoofer to the setup I have in mind.

My current setup is an AVR as pre amp for stereo (Denon X4400H), and the Denon also processes the home theater stuff and drives the center, surrounds and height speakers. The stereo speakers (front L+R in HT) are driven by a Crown XLS power amp, throught the Denons pre out.

I would like to add a proper stereo pre amp with balanced in- and outputs in the chain. The reasons are many, it will improve the sound by using both a better dac and dedicated stereo circuitry, I can finally use the balanced out on my phone stage, I do not need to power on the AVR to listen to music all day, and like most of you, I love getting new gear.

I am therefore looking at a few stereo pre amps that have Home Theater Bypass. This lets you do exactly what I want, put a stereo pre amp between your AVR and power amp. I will link a list and more info about HT bypass for those interested.

Now my problem: how would I connect the subwoofer in this new system? It is currently connected from sub out 1 on the Denon to the LFE input on the sub. In the Denon settings, this sub out sends the low end of stereo via crossover to the sub, and the LFE signal, and all the low end of the surrounds. Simple, 1 rca connection does it all.

But if I use another pre amp for stereo, the subwoofer also needs to be connected to that 'stereo only' part of the system, which would not use the AVR. One option I considered would be to get a REL, connect the AVR to its LFE input, remove the crossover for the 'front' speakers, and tap into the speaker outs on the power amp using their Neutrik connection. From what I can read in their information, this is what they recommend anyway, so that could work. Except that their Neutrik input does not like class D switching amplifiers. Which is what I use. And which I want to continue using, for its low energy consumption, low heat, and great power and sound for the price.

Does anyone have an idea how I could do this, without using a different sub just for HT and another one for stereo?
 

Sashoir

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Rather than having separate line- and speaker-level connexions, I have an intermediate MiniDSP 2x4 which takes the AV receiver's line-level sub-out and my stereo's digital out and routes to my three sub-woofers. I wouldn't say it's seamless (unfortunately MiniDSP doesn't allow a remote control to map to only one device), but it does provide variety of options (bandpass, equalisation, summing, &c). At a price.
 
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Sputnik

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Thank you, MiniDSP could work, and likely with any sub, I will look into it.
 

symphara

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Option 1 - get an integrated amp with pre-outs and connect it like that to a subwoofer with LR line input (not speaker input).

Option 2 - get an integrated amp with full subwoofer management like the Lyngdorfs and then you can do full bass correction there, use the AV receiver with Audyssey in LR bypass mode and don't connect the receiver to the subwoofer anymore.
 
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Sputnik

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Option 1 - get an integrated amp with pre-outs and connect it like that to a subwoofer with LR line input (not speaker input).

Option 2 - get an integrated amp with full subwoofer management like the Lyngdorfs and then you can do full bass correction there, use the AV receiver with Audyssey in LR bypass mode and don't connect the receiver to the subwoofer anymore.
Thanks but that would not get the lfe signal and the low level of surrounds to the sub.
 

symphara

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Thanks but that would not get the lfe signal and the low level of surrounds to the sub.
Of course it would. Option 1 connects LFE from the receiver to the sub. It’s basically the same as you suggested except for using an integrated amp with pre-outs instead of speaker output, if I understood you correctly. As you say, some class D amps don’t like to have their speaker output connected to a subwoofer.

Option 2 declares no sub in the receiver and sets the front speakers to Large, so it sends all the bass (including LFE) to the front speakers (i.e. your integrated amp with subwoofer management), and thus further to your subwoofer.
 
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Sputnik

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Of course it would. Option 1 connects LFE from the receiver to the sub. It’s basically the same as you suggested except for using an integrated amp with pre-outs instead of speaker output, if I understood you correctly. As you say, some class D amps don’t like to have their speaker output connected to a subwoofer.

Option 2 declares no sub in the receiver and sets the front speakers to Large, so it sends all the bass (including LFE) to the front speakers (i.e. your integrated amp with subwoofer management), and thus further to your subwoofer.
I appreciate you wanting to help, and I'm sure it's the answer to a question, just not mine.

Why an integrated amp over a pre amp if all you use is rca? That makes no sense.

How would the integrated amp even know there is lfe, let alone be able to pass it to the sub? All it sees is the pre outs from the front l+r from the av receiver for movies.

Same for the surrounds.

(Edit: re-reading it may be that the avr sends all the bass through the fronts if you disable sub in the avr, but I never looked into this because I always use .1.

I still think having that info seperate would be better than having the avr mix it in with the front channels, and having the pre amp filter it back out to send to the sub. It would be very hard for a stereo amp to do this without any loss of quality, we're talking about all of the of the lfe info and bass from 6 surrounds, a center and 2 fronts. Just to filter it back out to send to the sub.

But I think I see where you were going, and I do appreciate you trying to help. I still don't get why you mention an integrated, which is in part what threw me off).
 
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symphara

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I appreciate you wanting to help, and I'm sure it's the answer to a question, just not mine.

Why an integrated amp over a pre amp if all you use is rca? That makes no sense.

How would the integrated amp even know there is lfe, let alone be able to pass it to the sub? All it sees is the pre outs from the front l+r from the av receiver for movies.

Same for the surrounds.

(Edit: re-reading it may be that the avr sends all the bass through the fronts if you disable sub in the avr, but I never looked into this because I always use .1.

I still think having that info seperate would be better than having the avr mix it in with the front channels, and having the pre amp filter it back out to send to the sub. It would be very hard for a stereo amp to do this without any loss of quality, we're talking about all of the of the lfe info and bass from 6 surrounds, a center and 2 fronts. Just to filter it back out to send to the sub.

But I think I see where you were going, and I do appreciate you trying to help. I still don't get why you mention an integrated, which is in part what threw me off).
Ok so let me explain a little bit more:

If you set all the speakers in the AVR to "small", set the subwoofers to "none", the front speakers to "large", the AVR will sum up all the bass from the "small" speakers and the LFE channel and pack it in the front LR signal. This signal goes to your integrated amp, where you connect your subwoofer. This is option (2) I described above. There shouldn't be any noticeable loss of bass quality, and bass itself is not localized anyway. It will just come out of your subwoofer.

I personally have in use both options (1) and (2).

For (1), I have the subwoofer connected to the AV receiver on its subwoofer output to the subwoofer's LFE input, and connected to the integrated amp that deals with front LR from its stereo-pre-out to the stereo-line-in on the subwoofer. The subwoofer itself sums up the signals (LFE + L+ R).

From the point of view of the AVR it appears as if the speakers are full range. That's what it sees when it does auto calibration.

This way, when I listen to music on the integrated amp alone, I get the benefit from the subwoofer bass, and when we listen to movies, there's also the LFE channel going into the subwoofer, fed directly by the AVR. It works very well but it required some experimentation with the sub volume and crossover, since my integrated amp doesn't have any form of bass management.

For (2), I have the subwoofer connected only to the integrated amp. The AVR is set as described above (no subwoofer, all speakers as "small" except for front LR which are "large" so it sends all bass + LFE on front LR pre-out, connected to the integrated amp). This integrated amp has full bass management and auto-calibration, so it can extract the bass, apply room correction, and send it to the subwoofer. The AVR here is a Marantz and needs to be used in "Front LR bypass" for Audyssey, so you don't get double room correction. There are lots of people successfully using this setup with Lyngdorf TDAI-1120, 2170 and 3400 integrated amps. I guess it probably works with Dirac NADs just as well. I imagine you can add a miniDSP to anything that doesn't have room correction and will get a similar result for bass.

Now I don't know if you have a choice of amp, this is not clear to me from your post. It sounds like you might already have something and you don't want to change, so I don't really know what practical advice to give you. I was merely offering some ideas, take them as you will. If none of this applies to you, I'm sorry. I appreciate your DM and don't worry about hurting my feelings.
 
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Sputnik

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Thank you for the extensive explanation.

Currently the the AVR is a Denon X4400H, the power amp is a Crown XLS 2502, and the sub is a Klipsch SPL150. I am looking at adding a Rotel pre amp, a RC-1572 or 1592.

The solution to send all the bass through the front pre outs could work, certainly as a starting point. The Klipsch only has 1 set of rca inputs, so lfe and l+r is not possible. A different sub is always an option, but if I want to upgrade gradually, (2) might actually work, and be the easiest and cheapest solution.

I'm glad I asked for help here, I was stuck on getting the sub integrated, now I have options.
 

Silly Valley

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While most of the above mentioned approaches can work fairly well with some effort, they are not the simplest and most straight forward solution. What you really need is a preamplifier with HT Bypass which also includes a bypass for the sub; a 2.1 HT Bypass preamplifier. I like some of Rotel's gear and still own some. However the pieces you mention are not designed with this in mind. Consider something like a Parasound P6. It has all you need and is designed with this application in mind without a bunch of external monkey motion.

It goes like this:
Denon AVR L&R to P6 L&R HT Bypass inputs. P6 Pre Outs to your 2 Ch amp.
Denon AVR Sub Out to P6 Sub Bypass input. P6 Sub Out to your sub or subs.
Other Music sources connect to various P6 inputs.

When watching movies: Turn on your Denon AVR, 2ch amp and enjoy. P6 is in passive mode...Bypass. Denon Avr in control.

When listening to stereo music via other sources: Turn on P6, 2ch amp and desired source. Enjoy. P6 crossovers now directing signal to Main L&R and sub. No mess, no fuss.

Of course for 2ch through P6 only, you can't utilize Denon room correction for music. However with flexibility of sub placement and given a decent room, this may not be an issue, especially when using a sub with its own EQ. Whether or not you will hear a difference between your Denon and a 2ch Pre of your choosing is a question you will have to answer.

Unfortunately, there are very few preamps that are properly designed for this setup. Many will only handle full range 2ch and omit mains / sub blending and pass through. Another option is the Parasound NC 200 Pre but it lacks bal inputs if you are married to those.

All this would seem much less necessary if we had better 2 ch performance /quality in modern AVR's. As was explained by Dr. Rich in his 5 part dive into AVR build quality, the common choke point seems to be the large scale (LSI) volume controls used by many brands. Due to a number of factors, there finally seems to be a movement away from this practice to some degree (some late model Denon units). This would explain why most AVR's tested here on ASR at best fall into middle ground performance independent of price. Good luck!
 
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Sputnik

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Thanks @Silly Valley , and yes, I figured that out too. The stereo pre should also have trigger in so it goes on with the avr for smooth operation.

I saw the Emotiva xsp-1 (gen 2) has dedicated 2.1 ht input and was looking for other options like it, I'll have a look at the p6.
 
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