Advice needed about adding a sub to my stereo set-up

grnnvrzz

Active Member
I am doing some research looking for some advice regarding whether I could consider adding a subwoofer to my 2 channel set-up. I don’t necessarily need a sub, but I do like tinkering with my system so I am looking at options in terms of placement and then, when and if appropriate, possible kit.

A word on my current set-up; I am a Roon user, with a hardwired system. I have an Intel NUC running the Roon software, and this feeds a raspberry pi 4 running ropieee over Ethernet which provides an input into my Topping D90 DAC via USB. The DAC feeds my Musical Fidelity M6si amplifier which feeds my Kef Reference 1 speakers.

I have a relatively small room (see attached schematic for size measurements) that is irregular in shape, the room doubles as my listening room and office. I have previously measured my room acoustically to create digital correction filters and I have also attached those results. And for good measure, I have included a photo too!

My initial question is around potential placement, and in the schematic I have marked some possible locations for a sub – see numbered boxes. Are there any thoughts, positive or negative, as to these possibilities? I can shift kit around if needs be.

Finally, are there any thoughts on kit that might be a good match?
 

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ShanePJ

Well-known Member
AVForums Sponsor
Where do you feel you are missing on bass as you are wanting to add a woofer, as having heard how low those 1's go, I wonder whether adding a dedicated power amp is the way to go using the M6si for the one half (top of bottom half) of the speaker and using something like the PRX to drive to other half (top of bottom half). This should then give you the extra oomph to get that bottom end working without having to turn the volume up to much. My only concern is the alcoves as this might be causing an unwanted effect if you are noticing a drop off as it could be pulling or booming the sound in those areas
 

grnnvrzz

Active Member
Thanks for the reply @AV Online. Thats really interesting, I had not thought of that at all - adding an additional amp instead of a sub. I do tend to listen at more normal volumes (although my other half still tells me its loud!!) rather than ear bleedingly loud.

As to what I think I am missing, thats a good question. I am not sure how to describe it, its definately not a huge absense, more a sense there is more performance to be had. I think a bit more bass at lower volumes maybe also be a good way to describe it. Alternatively, I am well aware that I do like to tinker and try different things, so it could just be that.

So, if I was to add a PRX, would i run the XLR from the M6si into PRX, then have two sets of speaker wires running to the speakers - with the speakers having their terminals seperated?

I wonder if there is a cheaper way to try this approach? The latest class d amps (hypex etc) review and measure very well for instance.
 

grnnvrzz

Active Member
You have also go me thinking (painful) about the 'problem' differently. I wonder if I am using the current amp most effectively. There is a fairly small band where the volume goes from low to high (around 9 o'clock), and as I said I don't really listen at high volumes. I am therefore wondering if I am using the amp at too lower a volume to be really effective, and perhaps I actually have a gain issue as in, too much.

I have some in-line attenuators somewhere that I could try and this might open up the volume control. My only pause is around any negative effects on quality.
 
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ShanePJ

Well-known Member
AVForums Sponsor
I feel the tough one on this matter is volume and yes those speakers do need a bit of power behind them and sometimes power doesn't always mean volume. Good current which is what you will experience when adding a matching power amp should give you more without more volume as you will in truth also be adding twice the current to those speakers which should deliver that extra detail you feel you ought to be hearing

XLR is the way to go as this always add more separation in my opinion although I'm sure others will have their own comments on this area. Now I notice that you will not be able to partner a power amp this way as your integrated amp only has one set of XLR inputs

I would also have a look at just plugging the USB cable into the M6si (software downloads) and bypassing the V90 DAC to see if that makes any difference. I a PC for playing music and use a Teac UD-501 (its modern replacement is the UD-505) and in my system the DAC was a significate area where I heard a massive change in how I listened to music. Prior to it, I have an Arcam CD36 and when I used the Teac transformed the CD36's musical ability, then I used my laptop and it basically made the CD36 sound sluggish and quite none descript (what's amazing is I was happy with the CD36 before the Teac arrived). Because of the musical improvements, I sequentially build myself a dedicated media player and added an audiophile USB output stage card plus many pieces of software to give my DAC the best signal I could and yes the sound is better than I could ever imaging. If you did run down the route of the TEAC, then you can also hook it up with XLR cables and I have to say, My DAD had a Krell CD player and when I tried it in his system, it matched it on ability which gives you an idea where it sits

There is a fairly small band where the volume goes from low to high
I suspect this is down to those speakers just asking for extra current as mentioned earlier as you may find that you just need a little more to hear the full range

Now as for a cheaper option, you should be able to use anyone's amp so long as they match, so I'd double check with MF, but the Arcam PA240 is a similar product and is on offer at the moment

Attenuators are something that I have honestly not played with, so although I understand what they do, I've never experienced and if they do not reduce the signal, then it may have the opposite effect on trying to increase the current to the speakers
 

Paul7777x

Distinguished Member
You have also go me thinking (painful) about the 'problem' differently. I wonder if I am using the current amp most effectively. There is a fairly small band where the volume goes from low to high (around 9 o'clock), and as I said I don't really listen at high volumes. I am therefore wondering if I am using the amp at too lower a volume to be really effective, and perhaps I actually have a gain issue as in, too much.

I have some in-line attenuators somewhere that I could try and this might open up the volume control. My only pause is around any negative effects on quality.

If there is any degradation from properly constructed attenuators I have yet to hear it, even on super revealing expensive (ish) active speakers.

If the input on the MF is being loaded too heavily I’d definitely suggest trying the Attenuators. At the very least it will give you a better range volume control.
 

Paul7777x

Distinguished Member
Ps, the MF manual doesn’t say what the line level gain threshold is, and I’m not sure what your front end outputs, but 9 O’clock is way too low to be excessively loud so I’d certainly say there’s a gain mismatch there.

I’d be quite astonished if the M6si did not have enough power for the Kefs. I know they do dip to around 3.2 ohms, but the MF has a current swing of 45 amps. That is by no means modest.

And personally I’d say your room and positioning issues with a sub (preferably two) would benefit hugely from a Dirac addition.
 

grnnvrzz

Active Member
If there is any degradation from properly constructed attenuators I have yet to hear it, even on super revealing expensive (ish) active speakers.
I have had a play with the attenuators (JTS), they have -10db, -20db and -30db as options. I tried them all, and I could not hear any degradation in the sound. I ended up leaving them on -20db for a few days, with the main benefit being I could use more of the volume control. I have pulled the attenuators back out, and have them in my desktop (Adam F5s, RME ADI-2DAC) setup to check, again with no obvious degradation. I have not decided yet whether to add back in, on the whole, I think 'yes'.

Ps, the MF manual doesn’t say what the line level gain threshold is, and I’m not sure what your front end outputs, but 9 O’clock is way too low to be excessively loud so I’d certainly say there’s a gain mismatch there.
I am trying to find out about line level gain threshold of the amp. I have a look at the DAC manual - see below. To confirm I am on XLR. I run the DAC in DSD mode, so no pre-amp, and provide it DSD 256.

1637843145200.png

I wonder whether adding a dedicated power amp is the way to go using the M6si for the one half (top of bottom half) of the speaker and using something like the PRX to drive to other half (top of bottom half)

Although unsure about this approach (given the relative high cost - prx = £2500k ish) I have spoken to my local hi-fi shop (Sevenoaks Bristol - I bought the 6si from them and a number of other bits and bobs over the years) and they have agreed to lend my a PRX to try out the bi-amping, although not for another month or so. MF have suggested using the PRX to drive the LF (230w) and the M6si to drive the HF (220w). Another worry is lack of speaker cable now to bi-amp! I currently have some Blue-Jeans (Belden 5000UE 12 AWG), which I might need another few lengths of.

I obviously like to tinker, as I have also been reading up on DIY amps, I might try a NC400 Hypex based build in the future.
 
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ShanePJ

Well-known Member
AVForums Sponsor
I have had a play with the attenuators, they have -10db, -20db and -30db as options. I tried them all, and I could not hear any degradation in the sound. I ended up leaving them on -20db for a few days, with the main benefit being I could use more of the volume control. I have pulled the attenuators back out, and have them in my desktop (Adam F5s, RME ADI-2DAC set-up), again with no obvious degradation.


I am trying to find out about the amp, the DAC manual says - and I am on XLR.

View attachment 1608748


Although unsure about this approach I have spoken to my local hi-fi shop (Sevenoaks Bristol) and they have agreed to lend my a PRX to try out the bi-amping, although not for another month or so. MF have suggested using the PRX to drive the LF (230w) and the M6si to drive the HF (220w). My only worry is lack of speaker cable now! I currently have some Blue-Jeans (Belden 5000UE 12 AWG), which I might need another few lengths of.
I'm sure if they're happy to loan you the amp, they would also be happy to loan you a pair of interconnects plus speaker cabling up to the same standard as they understand your system. It's pointless only offering it if you cannot use it

I will be interested in hearing what you have to say once you've got the system in place. I would have ordinarily said to run down the woofer route, but I just cannot see how you will make one work in the room plus getting one that will have the ability to work with the electronics you own needs to be good. I also know that those Kef's do have a good level of depth and to my ears go down low, hence leaving the only option I can really think of as you should really be able to get some depth from them and as you are running them at lowish volumes, to me it seems you need more current to push the bottom end because of this and without turning the volume up, this is the alternative way

Oddly, with good quality electronics (which you own), volume should never be a concern as turning the volume up should open the sound stage more than increase the volume, its an odd effect that happens (and yes the volume gets a little louder, but the high fidelity doesn't diminish. Its usually this area where uncomfortable listening becomes noticeable hence it becomes louder. This is why I have mentioned this route as it should enable you to get the speaker moving without increasing the volume anymore). So in reality, running down this route should enable you to increase the sound stage whilst keeping everyone in the house happy, If it doesn't, then I feel you really need to look at the system as a whole as its not delving what you want
 

Paul7777x

Distinguished Member
I have had a play with the attenuators (JTS), they have -10db, -20db and -30db as options. I tried them all, and I could not hear any degradation in the sound. I ended up leaving them on -20db for a few days, with the main benefit being I could use more of the volume control. I have pulled the attenuators back out, and have them in my desktop (Adam F5s, RME ADI-2DAC) setup to check, again with no obvious degradation. I have not decided yet whether to add back in, on the whole, I think 'yes'.


I am trying to find out about line level gain threshold of the amp. I have a look at the DAC manual - see below. To confirm I am on XLR. I run the DAC in DSD mode, so no pre-amp, and provide it DSD 256.

View attachment 1608748


Although unsure about this approach (given the relative high cost - prx = £2500k ish) I have spoken to my local hi-fi shop (Sevenoaks Bristol - I bought the 6si from them and a number of other bits and bobs over the years) and they have agreed to lend my a PRX to try out the bi-amping, although not for another month or so. MF have suggested using the PRX to drive the LF (230w) and the M6si to drive the HF (220w). Another worry is lack of speaker cable now to bi-amp! I currently have some Blue-Jeans (Belden 5000UE 12 AWG), which I might need another few lengths of.

I obviously like to tinker, as I have also been reading up on DIY amps, I might try a NC400 Hypex based build in the future.

Both the single ended and XLR outputs are on the normal side for what they do. But I’ve often found that too high for many amps.

Some still have ridiculously low thresholds, as if they’re all driving TTs or tape decks from the seventies still.

If the attenuators are not degrading the sound, and I can’t really see how they could, then I’d stick with them for a couple of months to see how you become accustomed to the extra volume headroom. It takes a little while to become accustomed to even little positive differences and it’s worth the time taken.

For my Active Adams I can’t use a modern preamp/dac without attenuators. They are absurdly sensitive to input voltage.
 

grnnvrzz

Active Member
For my Active Adams I can’t use a modern preamp/dac without attenuators. They are absurdly sensitive to input voltage.
What attenuators do you use? I might grab some more, so I have some for each system. And what setting do you have them on? Its an interesting area, I found the RME DAC to output on the high side, and I ended up taking the volume down on the Adams, and then level matching with a mic, but I always thought that did not help the Adams, and the inline attenuators was a better solution.

I'm sure if they're happy to loan you the amp, they would also be happy to loan you a pair of interconnects plus speaker cabling up to the same standard as they understand your system. It's pointless only offering it if you cannot use it
True, I will ask!
I will be interested in hearing what you have to say once you've got the system in place. I would have ordinarily said to run down the woofer route, but I just cannot see how you will make one work in the room plus getting one that will have the ability to work with the electronics you own needs to be good. I also know that those Kef's do have a good level of depth and to my ears go down low, hence leaving the only option I can really think of as you should really be able to get some depth from them and as you are running them at lowish volumes, to me it seems you need more current to push the bottom end because of this and without turning the volume up, this is the alternative way

Oddly, with good quality electronics (which you own), volume should never be a concern as turning the volume up should open the sound stage more than increase the volume, its an odd effect that happens (and yes the volume gets a little louder, but the high fidelity doesn't diminish. Its usually this area where uncomfortable listening becomes noticeable hence it becomes louder. This is why I have mentioned this route as it should enable you to get the speaker moving without increasing the volume anymore). So in reality, running down this route should enable you to increase the sound stage whilst keeping everyone in the house happy, If it doesn't, then I feel you really need to look at the system as a whole as its not delving what you want
Thanks for the explanation, I will report back!
 

Paul7777x

Distinguished Member
What attenuators do you use? I might grab some more, so I have some for each system. And what setting do you have them on? Its an interesting area, I found the RME DAC to output on the high side, and I ended up taking the volume down on the Adams, and then level matching with a mic, but I always thought that did not help the Adams, and the inline attenuators was a better solution.


True, I will ask!

Thanks for the explanation, I will report back!

I had to use -20dB with my Adams. I tried -10 but it wasn’t enough to get the volume control on my (then) CDQ8200 moving effectively.

It was the same (that is very similar) with my Mdac, Anthem MRX, current Lyngdorf, a Lexicon processor and an old Yamaha DSP-E800 amongst others.

Before that a tiny turn or remote stab sent the volume whopping up.

I had some made by John Westlake as a favour. He’s a very friendly guy.

Any attenuators that are made properly will do a good job. I prefer the single value ones to multi option, but that’s just a Luddite attitude. It makes little if any difference.

Ps, dropping the gain too far on the Adams, or any active speaker, is not the best way (at least so I’ve found), it always seems to make them less dynamically inclined. And, I’m convinced, though I have no graphs to illustrate it, that bass control, especially at low volumes, suffers a penalty in that it never seems quite as well pronounced.

Attenuators every time for me, with the speaker gain at at least half, assuming an issue in the first place.

And for passive amps, if the dial is at less than at least 11 o’clock + for comfortable listening, then -10dB for them too.
 
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grnnvrzz

Active Member
I had some made by John Westlake as a favour. He’s a very friendly guy.
I am jealous!

As ever with the internet, as soon as I start looking I find ever increasing price options. I think the Rothwell XLR Balanced In-line attenuators are the way to go, they are -20db fixed, and on AV Online, however I did read a few issues with quality on other sites, but, that may just be a few out of many sold. I then made the mistake of finding these, I want one of those now! Its shiney.
 

Paul7777x

Distinguished Member
I am jealous!

As ever with the internet, as soon as I start looking I find ever increasing price options. I think the Rothwell XLR Balanced In-line attenuators are the way to go, they are -20db fixed, and on AV Online, however I did read a few issues with quality on other sites, but, that may just be a few out of many sold. I then made the mistake of finding these, I want one of those now! Its shiney.

They are extraordinarily fine looking pieces of engineering. Especially the remote ones.

I’d have one.

Possibly too expensive for what you need though 😁

Still, they do look awesome...

As for Rothwell, I’ve only ever heard good stuff about them. I had a pair of their -10dB phono attenuators for a while, years ago, and they did exactly what I wanted them to.

There’s always likely to be some negative internet comments for anything that sells enough numbers. Sometimes for genuine faults, which I assume they’d replace, and sometimes from people who don’t know what they’re doing.

I’d say the Rothwells are a good buy, a well known set up that’s been around for a good while.
 

grnnvrzz

Active Member
They have arrived (the Rothwell Attenuators), that was quick! Reading the blurb, it seems to suggest plugging into the back of pre-amp, so as the M6si is integrated, I assume straight into the back of the amp. This is a change, as with my other attenuators, I have gone straight from the back of the DAC.
 

Paul7777x

Distinguished Member
It’s best form to put them into the amplifier.

That way the signal is not attenuated until the last point before it needs to be.

Sending a strong signal is good practise. Accepting a too strong signal is not.
 

grnnvrzz

Active Member
It’s best form to put them into the amplifier.

That way the signal is not attenuated until the last point before it needs to be.
I managed to shuffle my rack forward a little so I could accomodate the new attenuators. I do wonder if I went a bit far with the -20db instead of -10db. Anyway, I have done a few hours of listening and everything sounds good.

To listen loud, the volume knob is around 12 - 1 on the dial. I thought the amp would be hotter, but it is relatively cool, at least, no hotter.
 

Paul7777x

Distinguished Member
If you consider 12-1 to be loud then you’re ok with -20.

Try it out at, say 3. If that’s too loud, and it’s likely to be so then you don’t have a problem.

It probably just seems odd compared to loud at 9 o’clock.

You might be able to exchange them for -10, but I can’t see it as a problem, unless you frequently want to feel window breaking volume at parties?
 

lindsayt

Active Member
I can shift kit around if needs be.
What a lovely room!

If I had your home I'd be really annoyed by the positioning of the Kefs.
They intrude far too much into your cosy room.

I'd be looking to have speakers placed right in the alcoves. Recording studio style. Mounted high up on the wall, angled downwards towards the sofa.

If the Kefs sounded crap in that location I'd change them for other speakers. Old school studio monitors - eg Altec 604's or 605's would have a good chance of working as well as any speakers in that location. This may well result in speakers with much larger cabinets, but from a practical point of view you'd have a very nice net gain in terms of the floor space available to you.

As an alternative to Altec type dual concentrics, you could go for a single driver full range solution. EG Fane 12" full range driver or Lowther 8".

With the right type of speakers in your alcoves you could then reasses whether you wanted a sub or two or not.

With Fane 12-250TC's costing £75 per channel brand new, it's one of those where it's worth taking a punt. And if you don't fancy a bit of simple woodworking, just get a local cabinet maker to cut, glue and screw together the braced plywood cabinets for them.

Your audio equipment should be a slave to you. Show your system who is boss and put your speakers in their rightful place.
 

FRFT

Active Member
I feel you're going the wrong way with your solution and being pushed into what other people think is best, even if it's not best for you.

I'd either buy a sub that does what the kefs can't - clean extension into the 20hz range - or just download a programme like equalizer APO and simply add some bass boost like that. I assume your amp has some kind of sub out if you want to add a sub?

Run a frequency sweep on YouTube (careful when the video starts at 20hz) and see what you find. Listen out for big peaks and dips in your frequency response to determine the issue.

Peaks are easy to fix, just eq them down. Any big dips throughout the response are usually a room issue and best not to worry about those as they can't usually be easily fixed.

Only issue I can see with adding a sub is I'm not sure where you would fit it as your room isn't the biggest, depends how much you value the floorspace. With those kefs, I'd go for a larger sub as you should be crossing it around 40-50hz tops.
 

spinaltap

Distinguished Member
A risk in simply adding a Sub is the likelihood of the Sub ‘singing along’ with your main speakers. That is, without being able to control the frequency cut-off point of your Sub via the pre/amp, the outcome of what you desire will not be realised.
 

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