Advice needed: will adding a subwoofer for stereo listening be a good idea?

I would like your advice. I own a Mordaunt Short Aviano 7 subwoofer. With a frequency response of 35Hz - 200Hz and an adjustable crossover between 50Hz - 200Hz. The subwoofer is currently connected to my Denon AVR and is used only when watching movies. I was thinking of going through the trouble of connecting it to my Primaluna stereo amp which has a mono out to connect a subwoofer to.

Looking at the specs of the Montis speakers and the subwoofer, both state they can go as low as 35Hz. So, will it actually make any positive difference at all? Or will it just complicate my setup, muddy up the sound, or something like that?

I don't feel that the bass is lacking listening to stereo music. But I've never tried adding a subwoofer before, so I don't really know if I'm missing out on something.

Thanks for your time and hopefully your advice and thoughts!

No harm in trying. A lot depends on your room. I suspect the montis have great bass response as I have heard them before. I know nothing about your sub. I find sealed subs work better than ported with ML. and keep it away from corners

If the sub is set up optimally, the answer is yes.

IMHO, the (theoretical) primary benefit would be smoothing out the overall room bass response, especially if you have bass room nulls at some listening positions. It's unlikely you'd get deeper tighter bass by adding the sub.

Conversely, it could potentially muddy up your overall bass response. Ideally, it would be helpful to measure the before/after speaker +/- sub room frequency response (using a calibrated mic with REW, XTZ Room Analyzer, or Omnimic, etc), in addition to listening. Your sub only has two phase settings, so it might be challenging to get it optimally dialed-in.

Also, how will you use the sub for movies? Does your Primaluna amp (? integrated) have Home Theater Bypass, or would you buy another sub to connect to your receiver?

I agree with Alan (sleepy), any sub not capable of 20hz has no place in my system. Given how good the Montis is and depending on your room it's likely the real help you will need is the bottom octave

With specs like that, it sounds like more of a theatre subwoofer. That is - designed to make big bass, not deep bass. That aside, you can always try it and see if it is to your liking. But optimally dialled in, I don't think it'll do too much more than the Montis in terms of getting deeper / tighter bass.

Thank you all for your responses so far!

sleepysurf said:

[...] Ideally, it would be helpful to measure the before/after speaker +/- sub room frequency response (using a calibrated mic with REW, XTZ Room Analyzer, or Omnimic, etc), in addition to listening. Your sub only has two phase settings, so it might be challenging to get it optimally dialed-in.

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If I'll go ahead, I'll do a before/after frequency response measurement. I've done that before, trying to find out the impact of my DIY diffusion and absorption panels in the room. It gave me good insight in decay times and such, but still find it hard to interpret all that information.

sleepysurf said:

[...] Also, how will you use the sub for movies? Does your Primaluna amp (? integrated) have Home Theater Bypass, or would you buy another sub to connect to your receiver?

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It's an integrated amp with a dedicated HT bypass. So, by not being connected to the receiver, I will loose at least the LFE signal. Unfortunately I don't have enough floor-space to add another subwoofer. It also makes correct placement very limited in options. It's now lengthwise placed about 25% from the sidewall, but stuck to the wall behind the listening position. I really don't have any other option without completely rearranging my living space.

Replacing it with one that goes lower, like Twich54 suggests, is an option. My hearing doesn't go as far down as 20Hz, but I guess it might be more of a tactical sensation than an auditory one. I'm a bit worried about how the waves will propagate through to my neighbours though.

amey01 said:

With specs like that, it sounds like more of a theatre subwoofer. [...]

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Yes, it was part of my surround set I had before the Montis. For watching movies it is just fine for my liking, without getting the neighbours annoyed to much.

Given the config you've outlined, hard to see how you could benefit from the sub on both HT and 2ch duties, as the setup of the sub would have to be very different.

For the HT function, you'd want to use the LFE out going to an input of the sub that performs zero crossover duties. Usually called 'LFE In'.

For 2Ch duties, you'd want to route the L/R pre-amp level signal to the sub L/R Crossover input, then take the L/R crossover outputs and feed the power amp.

But now that messes with the HT bypass function, and you lose the L/R in HT mode.

I'd say just stand pat with what you have or replace the preamp and receiver with a modern HT preamp such as the Marantz AV7704 or AV8805 (or their receiver counterparts, as they have pre-outs for the L/R), and that way you have a simple to operate system, and can benefit from room correction on both HT and 2CH.

JonFo said:

Given the config you've outlined, hard to see how you could benefit from the sub on both HT and 2ch duties, as the setup of the sub would have to be very different.
For the HT function, you'd want to use the LFE out going to an input of the sub that performs zero crossover duties. Usually called 'LFE In'.
For 2Ch duties, you'd want to route the L/R pre-amp level signal to the sub L/R Crossover input, then take the L/R crossover outputs and feed the power amp.
But now that messes with the HT bypass function, and you lose the L/R in HT mode.

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Thanks JonFo, but the Primaluna I have is an integrated amp with a dedicated mono out for the sub, connected to the same RCA connector on the sub as is used for LFE.
That doesn't make the situation that much different though. I either connect the sub to the Integrated amp or to the AVR. But I was wondering if connecting both via a analog switch would be an option. I realize that the switch must be a good one as having connected both to the sub at the same time (with everything powered on) could cause damage to all connected components. But could this be a simple solution for my 2 amps to 1 sub situation?

Anyway, I'm thinking of getting an SVS SB-2000 to fill the 19-35Hz gap I have with the Montis'. I'm not sure if I have to dial that in more than the current sub and therefor removing the possibility/effectiveness of connection both amps.

JonFo said:

I'd say just stand pat with what you have or replace the preamp and receiver with a modern HT preamp such as the Marantz AV7704 or AV8805 (or their receiver counterparts, as they have pre-outs for the L/R), and that way you have a simple to operate system, and can benefit from room correction on both HT and 2CH.

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I really like the Primaluna for music. I can't quantify it, but it's more engaging compared to any other AVR or amp I've owned before. So, I rather stick with it. And, if necessary, I'll stick with the current situation without any sub in 2CH.

I almost forget to mention that I've connected the sub today. After some dabbling with all the dials and such I find that some instruments like the piano and violin/viola, feel more full-bodied. Drums also have more heft to them. So that's why I was thinking of getting the SVS SB-2000 and experiment some more.

RDC said:

Thanks JonFo, but the Primaluna I have is an integrated amp with a dedicated mono out for the sub, connected to the same RCA connector on the sub as is used for LFE.
That doesn't make the situation that much different though. I either connect the sub to the Integrated amp or to the AVR. But I was wondering if connecting both via a analog switch would be an option. I realize that the switch must be a good one as having connected both to the sub at the same time (with everything powered on) could cause damage to all connected components. But could this be a simple solution for my 2 amps to 1 sub situation?

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Now that I've read the manual for your preamp, I understand a bit more, and it's as I thought, a tough situation.

For HT, it's all pretty straightforward, and the way you had it wired at the beginning of the thread was fine, Sub LFE In being fed by AVR LFE out, and the L/R routed through the HT bypass in the PrimaLuna.

Now, for 2ch mode, to use a sub with the PrimaLuna presents a problem: Where to do the crossover between mains and sub?

The Primaluna mono output is a simple summation of the L/R pre-level output. No crossover is specified for it, so it is a mono FULL-RANGE signal.
Feeding that into the LFE In of a sub is not correct, as the sub will be trying to reproduce the full range until it hits natural roll-offs, but not before totally coloring the mid-bass range.

But even if you feed the L/R crossover inputs on the sub and set a reasonable low-pass crossover point (say 60Hz), you would still have 'double bass' as the Montis is still getting below-60Hz content as well. So bass will be overwhelming and boosted significantly around the crossover point, where the Montis and the sub are well within their capabilities.
So that's not ideal either.

What's needed is for the L/R pre-level output to go to a crossover, be split into low-pass for the sub and high-pass for the Montis and the high-pass fed back to the PrimaLuna. One problem, the PrimaLuna does not have a pre-out-amp-in loop, so that is not possible.
Basically, for some crazy reason, the designer includes a mono summed pre-out (full range), says it can be used for a sub, with zero consideration for proper crossover configuration. Pretty poor design choice in my book.

And because all of the above hookup is in the analog domain, critical things like time-delay and phase can't be adjusted for ideal blend either. So very sub-optimal.

Which is why my original recommendation still stands, a modern pre-amp that can handle all the configurations needed in one simple box.
If the 'sound' of the primaluna is important, then I'd suggest an amp-only version, or given their pricing, just keep the one you have and use it as an amp fed via the HT input.

I go into all that not so much as to try and convince you to take my recommendation, but I wanted to be detailed for the other readers as well. This is an all-to-common setup challenge.

So for me, the choice is binary: 1- stay put, 2ch mode is just the Montis, no sub. 2- New pre-amp or AVR (with pre-outs) to handle both 2ch and Surround, sub is managed by the AVR in all modes. PrimaLuna is just an amp (fed via HT input).