Hi Xanthe, I hope you don’t mind me tagging you into this thread. I was tempted to post myself that the OP shouldn’t be put off the idea of adding DSP to the sub signal in case of added latency, but though it would be better coming from someone who actually uses such a setup.
Thank you @Xanthe for your explainations.When I considered at first the dsp solution,I was hoping that there could be more delay with my reflex speakers filters than with a dsp/sub set,and thanks to that that applying extra delay to the dsp/sub set would match the speakers one,after solving the placement issues.
Even though I read all I could find about dsp and acoustic,I’m not really confident of the way I see them.
So you would advise me to try it don’t you?
Calling naim for the Sub high level input issue seems to be the most appropriate,as they are busy replying mails I didn’t want to take their precious time for a froggy’s oral English lesson but I will tell them that @xcentric asked me to😂
Once again thank you for your help lady and gentlemen
Hi Max,
In terms of delay, due to their very nature, subs always have a degree of delay at the crossover frequency to the main speakers (in comparison to the signal from the main speakers). This is inherent in the way they work and is a combination if the heavy speaker cones, the amplifier used and the filter circuitry. Typically at crossover frequency this will be 2.5 to 5 ms. This can’t really be reduced any further (the manufacturer will already have minimised this as far as they can with any particular design).
There is a very simple way to compensate for this delay: place the sub closer to the listening position than the main speakers! The question is how much closer and how to determine the exact distance: for 2.5ms this is 0.85m; for 5ms this is 1.6m. In my case the phase match occurs when the sub is 1.2m closer to me than the main speakers (it sits behind my listening position). The answer is to measure it. You are investing a lot in the sub, investing a further €150 to accurately set up the room integration of your whole system seems to be a wise use of funds. What you need: a calibrated measurement microphone (such as the miniDSP UMIK-1 ~€110) a copy of REW (software €0) and a laptop and a cable to connect the output from the laptop to the preamp. REW will do a frequency sweep and measure the both the frequency response and the phase response in the room. This makes it much easier to align the crossover frequency, phase and gain of the sub to suite your main speakers in your room, as everything is then clearly visible. This is much more accurate than trying to determine each of these things by ear, all at the same time… You can’t specifically just listen to the effect of one of these parameters without also hearing the effects of other two at the same time: so (despite what others will tell you) doing it by ear, is for most people, nearly impossible to get right; measuring it makes it easy.
A further advantage of this approach is that the frequency response plot can be used to fine tune the position of the sub to get the room integration of the sound to be as even as possible. If you use a DSP to integrate the sub you can also tailor the response of the sub to reduce the effect of room resonance modes.
Another side benefit (but nothing to do with the sub 
) is that the phase and time plots can be used to identify unwanted reflections from your main speakers!
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Thanks for your well informed post…I knew you would be able to shine a light on the nitty gritty…cheers
Is there anything special about the laptop 3.5mm jack to pre-amp din cable needed to run REW ? Is it something readily available if I find somewhere that sells something like a miniDSP UMIK-1 ?
No, nothing special: in the UK many people can supply one (such as ‘Flashback Sales’ & many others) - it doesn’t even have to have ‘high audiophile quality’ credentials!
Another option if you have a suitable DAC is to connect your DAC to the laptop using a USB connection (or S/Pdif if the laptop jack has an optical output).
Another option (the one which I use) is a cheap USB to S/Pdif converter which then connects to a digital input on my 272.
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Hi @Xanthe
Your explainations are crystal clear,thanks a lot!
The two things I was afraid of with dsp was if it could degrade sound quality,placed between the pre and the amp.It would have been the best solution to manage every channel(mains and subs) ,after placement considerations with rew.What do you think!do you actually use your dsp between your pre and you amp for all channels or only for subs,not to interfere with the signal going to your mains?
The second thing was that I had no idea of the delay values a sub could get,but if two metres or so should be enough to compensate for any good sub Delay that’s great news!
I was willing to proceed exactly the way you advised me to,with rew at first for placement and acoustic treatment(I have some Gik panels waiting for that)then a minidsp for correction ,which was also solving the issue with nac552 output cable length some forumers were afraid of.I have just received a reply from naim,there seems to be no issue using the nac552 third variable output for a sub,provided it is not too long.
But I’m still waiting their answer about high input subs connection considerations.I will keep you advised.
Thanks a lot for the time you spend helping!
Unfortunately I have neither a DAC (other than in my headphone amp) nor a digital input. Dinosaurs roam free…
Now most of them fly rather than roam (but some have subsequently lost the ability to fly).
Mainframe computers in the 21st century are like dinosaurs in the Paleogene: they’ve got smaller and learnt how to fly!
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Hi everyone
I’ve just received a reply from naim about connecting a nap500 to subs high level input.They don’t talk about any failure or any big issue proceeding that way.But the low level connections from the nac552 will provide better quality with naim’s kit.So they recommend the last option.
So I’m gonna get some infos about this kit…
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