REL + Class D poweramp advice

[Ittaku]

2 minutes ago, Mike13 said:

That option is still there because it is easier than integrating them using DSP. I can’t see why it would sound better with the high level, but maybe it does!

Rel have been pushing the crap about using the high level inputs forever simply because that's how they started out and they're invested in that approach so they keep telling everyone that it's going to sound better that way. There is absolutely no way putting it through an extra layer can be helpful, nor does it provide any opportunity for crossing over the main channel speakers. Yes it's more complicated to split the sound beforehand but the potential benefits are huge, whilst putting it on the high level outputs is there for legacy reasons predating that option.

[G-Dubz]

39 minutes ago, Mike13 said:

I reconnected all my cords and wires and now my Rel T9i’s are switched off because they hum.

 

When I bought my Chord Qutest a helpful sales guy at Carlton Audio gave me half a speaker cord and said to connect it to a metal screw on the amp and a metal screw on the subs. This didn’t work. 

 

I bought something to go inbeteeen the TV aerial and the wall aerial socket. Didn’t work. 

 

I bought an ifi Ground Hog because it is supposed to fix hums. I’ll try it this weekend, however I’m sceptical because I’ve since realised that the straight print on a power cable means it is already grounded. Will report back. 

I'm still waiting on an RCA cable to try and ground through the LFE channel. Fingers crossed that will get rid of the hum with the black cable not connected. Will report back 

Edited April 5, 2019 by G-Dubz

[Serpeant]

10 minutes ago, G-Dubz said:

I'm still waiting on an RCA cable to try and ground through the LFE channel. Fingers crossed that will get rid of the hum with the black cable not connected. Will report back 

I can tell you it works.

 

You're meant to turn LFE to minimum, but I dont.

[blybo]

On 04/04/2019 at 10:18 PM, andyr said:

 

So it seems REL is able to get away with not having their USP (which is: connect through the main speakers to the subs) disproved ... because the people who use REL subs generally have HT systems (and, hence, AVRs) rather than stereo amps in a music system?

 

Andy

 

I don't! I use SVS and Subsonic subs in my HT room but a single Rel S3 for 2.1ch duties. I tried both ways and found the speaker level integrated better... and easier. Speaker level took 5 minutes playing around and I've only tweaked volume once since, and I've had the REl over 6 months now. I only notice my sub when its not on, or if listening to some poorly mastered modern music with dodgy artificial drum beats. 

 

I had it explained to me by the owner of the store that I purchased from (and plenty of other gear over the years) that speaker level negates timing and potential phase issues. I'm not technically minded, I just know what sounded better to me.

[blybo]

speaker level connections are hardly a USP of Rel either. Plenty of subs have that ability. Pretty sure my Subsonic does, even though I've never used that method. Rel probably put more effort into this connection than most sub manufacturers as they are generally used for dedicated stereo systems rather than AV, so there is a greater chance of the amp not having a pre-out connection.

Edited April 6, 2019 by blybo

[andyr]

1 hour ago, blybo said:

I had it explained to me by the owner of the store that I purchased from (and plenty of other gear over the years) that speaker level negates timing and potential phase issues. I'm not technically minded, I just know what sounded better to me.

 

I'd love to hear that explanation from the gentleman in question - because, to me, it doesn't make sense.

 

1 hour ago, blybo said:

speaker level connections are hardly a USP of Rel either. Plenty of subs have that ability.

 

The Rythmik sub in my 2nd system does too - but I wouldn't dream of using them.    And Brian Ding recommended I use the RCA inputs.

 

Quote

...so there is a greater chance of the amp not having a pre-out connection.

 

What is a 'pre-out' connection?  Do you mean a 'sub-out' connection?

 

Or are you referring to an integrated amp which is able to pass the output signal from its preamp stage to an external amp?

 

Andy

 

Edited April 6, 2019 by andyr

[blybo]

2 hours ago, andyr said:

What is a 'pre-out' connection?

Huh? The same connection if you want to connect a power amp to an integrated... if they have a pre-out, many older minimalist integrated amps don't, so that's where speaker level is always available. What do you do if your pre-power combo only has 1 pre-out? Use a splitter?

 

Here a view of the back of my integrated

It calls it a sub out/pre out, but every integrated I've ever come across prior to this one simply calls it a pre out.

Edited April 6, 2019 by blybo

[blybo]

2 hours ago, andyr said:

The Rythmik sub in my 2nd system does too - but I wouldn't dream of using them.

of course not, you are running active crossovers aren't you?

[Ittaku]

Even if there is no dedicated sub pre-out, a splitter on two channel pre-out makes more sense than using the high level outputs still.

[blybo]

47 minutes ago, Ittaku said:

a splitter on two channel pre-out makes more sense than using the high level outputs still.

Why? Because you can run a high pass filter on the main speakers?

 

What if you don't want that level of diminishing return?

[Ittaku]

5 minutes ago, blybo said:

Why? Because you can run a high pass filter on the main speakers?

 

What if you don't want that level of diminishing return?

Because you're unnecessarily putting it through the entire amplification stage to then just step it back down again internally in the subwoofer to line level again, and adding a component in parallel to the main speakers, altering the performance of the output to the mains (and potentially blowing stuff up if your -ve on the amplifier is floating as this thread started out discussing.)

[andyr]

1 hour ago, blybo said:

Huh? The same connection if you want to connect a power amp to an integrated... if they have a pre-out, many older minimalist integrated amps don't, so that's where speaker level is always available. What do you do if your pre-power combo only has 1 pre-out? Use a splitter?

 

Here a view of the back of my integrated

 

It calls it a sub out/pre out, but every integrated I've ever come across prior to this one simply calls it a pre out.

 

Aah, thanks.  Yours appears to be in integrated AV amp (given the USB & Ethernet connections) - not just an integrated stereo amp?

 

And yes, I agree with Con - if your pre-power combo only has 1 pre-out ... you use a splitter.

 

1 hour ago, blybo said:

of course not, you are running active crossovers aren't you?

 

As I said - the Rythmik is in my 2nd system.  This has a pair of NotePerfect 'Alpha' standmounts, with the Rythmik in the centre.  There is an active XO between the Rythmik and the Alphas - which is LP for the sub and HP to the Alphas, at 80Hz - this XO is provided by the Rythmik plate amp.  There's a minimal passive XO in the Aphas themselves - AIUI, it's simply a series cap to roll the tweeters off @ 6dB ... the woofer rolls off naturally.

 

So the wiring is basically:

• preamp output to Rythmik plate amp (R & L)
• RCA interconnects from HP filter output on the plate amp to R & L power amps.

(It's actually a little bit more complicated than that but this doesn't change the basic concept.)

 

Whereas, as I think you know, my main system is fully active - using a miniDSP 10x10HD to provide a 4-way active XO, including subs.

Andy

 

[blybo]

57 minutes ago, andyr said:

Yours appears to be in integrated AV amp (given the USB & Ethernet connections) - not just an integrated stereo amp?

Nope, stereo integrated with DAC and streaming built in.

58 minutes ago, andyr said:

This has a pair of NotePerfect 'Alpha' standmounts, with the Rythmik in the centre.  There is an active XO between the Rythmik and the Alphas - which is LP for the sub and HP to the Alphas, at 80Hz - this XO is provided by the Rythmik plate amp.  There's a minimal passive XO in the Aphas themselves - AIUI, it's simply a series cap to roll the tweeters off @ 6dB ... the woofer rolls off naturally.

So yes you are running a complexity I'm not interested in. Put me in the "subjective" camp if you like, it sounds good to me, I don't need to over complicate my stereo rig. I do run full Audyssey Pro DSP/EQ in my HT room with dual subs, but that is all built in to my receiver.

1 hour ago, Ittaku said:

Because you're unnecessarily putting it through the entire amplification stage to then just step it back down again internally in the subwoofer to line level again, and adding a component in parallel to the main speakers, altering the performance of the output to the mains (and potentially blowing stuff up if your -ve on the amplifier is floating as this thread started out discussing.)

My integrated amp is class A/B, I knew about the issues with class D so not a risk. I also think I'm getting better synergy BECAUSE the signal is going through the same amplification stage as my mains, so my mains and sub are getting exactly the same signal. As I understand it speaker level connections go unnoticed by your 2ch amp so do not hamper performance in any way. YMMV

[robmid]

This vide from REL shows how to connect and avoid disasters.

https://rel.net/how-to-connect-a-rel-to-a-class-d-amp/

[andyr]

18 hours ago, blybo said:

Why? Because you can run a high pass filter on the main speakers?

 

16 hours ago, blybo said:

So yes you are running a complexity I'm not interested in. Put me in the "subjective" camp if you like, it sounds good to me, I don't need to over complicate my stereo rig. I do run full Audyssey Pro DSP/EQ in my HT room with dual subs, but that is all built in to my receiver.

 

Aah, from these statement of yours, I think I understand where you're coming from, B.  (A completely different weltanschauung from me - but that's cool!  )

 

Yes, I do think the mains should have a HP filter applied when you add subs.  My own view is that you want 2 adjacent drivers to cover the same frequency range as minimally as possible.  Speakers have an XO between woofer & mids - and mids & tweeters - so that the frequency range covered by each driver impinges upon its neighbour as little as possible.  If this is standard practice in speaker building ... why wouldn't you follow the same logic with a sub-to-woofer cross over?

 

Rolling off the mains to match the sub roll-off point has 2 additional benefits (apart from taking away the muddiness that comes from a frequency band being shared by 2 adjacent drivers):

1. distortion in woofers increases, the lower the note it is being asked to reproduce (as the lower the note, the more extension is involved).  So if a woofer can actually produce a hearable 40Hz note but you apply a 24dB HP filter to it at, say, 80Hz ... it produces less distortion.
2. as extreme LFs suck up lots of amplifier power ... if you free up the amp driving the main speakers from having to deliver below 80Hz ... it will have more available power to reproduce transients in the remaining frequency range. So it will sound cleaner.

And for me ...if it "sounds good" - that's great ... but I always like to see if I can make it sound better! 

 

Andy

 

[blybo]

On 07/04/2019 at 9:34 AM, andyr said:

And for me ...if it "sounds good" - that's great ... but I always like to see if I can make it sound better! 

Agreed, but I'm not going to be adding components to do so. My system is 1 of the simpler ones out there, streaming integrated, TT, speakers & Sub. DONE.

 

If the integrated had DSP built in I'd use it, but I'm not adding an outboard processor

[G-Dubz]

If the hi/lo input to the sub which piggy backs off the same output from the Poweramp as the LS50's covers the low frequency wavelengths, particularly as I have set crossovers at 80Hz, does this reduce the load on the LS50's? I read that it does but I'm trying to figure out how.

 

Because the analogue output from the Poweramp will be going to both the LS50's as well as the sub. How will the LS50's know not to play the lower sub 80Hz frequencies if the Poweramp is outputting the same signals to both the LS50 & the sub simultaneously? 

 

Hopefully my question makes sense 

[andyr]

5 hours ago, G-Dubz said:

If the hi/lo input to the sub which piggy backs off the same output from the Poweramp as the LS50's covers the low frequency wavelengths, particularly as I have set crossovers at 80Hz, does this reduce the load on the LS50's? I read that it does but I'm trying to figure out how.

 

Because the analogue output from the Poweramp will be going to both the LS50's as well as the sub. How will the LS50's know not to play the lower sub 80Hz frequencies if the Poweramp is outputting the same signals to both the LS50 & the sub simultaneously? 

 

Hopefully my question makes sense 

 

My understanding is that the LS50's will not know how not to play the lower, sub 80Hz frequencies.

 

Perhaps @blybo would like to comment.

 

Andy

 

[G-Dubz]

17 minutes ago, andyr said:

 

My understanding is that the LS50's will not know how not to play the lower, sub 80Hz frequencies.

 

Perhaps @blybo would like to comment.

 

Andy

 

Thanks, I suspected so.

 

I've seen multiple forums posts though saying that adding subs into 2 channel stereo set ups can help to free up the 2 channel speakers mid range but doing the heavy lifting in the low frequency range. Perhaps a mini DSP or a regulatory device is needed for this?

[G-Dubz]

Just reporting back an update....the RCA cable from LFE to the sub connector on the preamp did indeed ground the circuit and there is no hum with the black cable disconnected. 

 

However....not that the black cable is disconnected as per the REL official website...there is no output from the sub anymore with only the red & yellow cables connected. Given that connecting the black cable in may damage class D amps...not really sure what to do now. Potentially give up on the speakon cable and just use the low level RCA connection, which is pity because the speakon cable is very good...Seems like the REL in my amp setup is critically reliant on the black cable connected in order to produce any sub output. I tried pulling the black cable in & out and clearly sub output was fine with black in, and nothing with black cable out. 

Basically, sub output works with black cable in. 

 

 

 

 

No sub output with black cable out

 

 

Any troubleshooting ideas would be great

Edited April 8, 2019 by G-Dubz

[andyr]

7 hours ago, G-Dubz said:

I've seen multiple forums posts though saying that adding subs into 2 channel stereo set ups can help to free up the 2 channel speakers mid range but doing the heavy lifting in the low frequency range.

 

If you just have a stereo amp driving your main speakers, Geoff, then they are obviously being driven 'full range'.  So the speakers will deliver bass to whatever level they have been designed to do.  Let's say 35Hz (which is what my Maggies are specced to).

 

The speakers will try to produce a 20Hz note if they are fed one but, basically:

a. because it's beyond the FR the woofer can deliver, it simply won't be loud enough to be head.

b. whatever 'noise' the woofer is trying to make at that frequency will incorporate high distortion.

c. having the woofer trying to deliver such LFs is taking away amplifier power.

 

If you add a sub (or, better, a pair of subs), you need to use a HP filter to roll off the mains - ie. you won't be "freeing up the 2 channel speakers" unless you have this filter in place.

 

7 hours ago, G-Dubz said:

Perhaps a mini DSP or a regulatory device is needed for this?

 

Yes, an active filter is required to roll off the mains.  This filter can be provided by:

• the sub's plate amp (like on the Rythmik in my 2nd system)
• a miniDSP (like I use in my main system), or
• some other make of active filter.

Andy

 

[tubularbells]

Apologies if I missed your post but did you try my suggestion of grounding the black wire to the chassis of either the amp or other equipment?

 

IMO your making it harder than it needs to be by using a RCA cable just to ground the sub. It should definitely work using just the yellow and red wires though as I and many others have used this approach to connect to class D or bridged amps in the past.

[Ittaku]

It is possible add a subwoofer without crossing over the main speakers and still derive the benefit of the main speakers not working as hard, but you still need DSP or even tone controls to do so. Imagine you add a subwoofer and it's set to louder than the woofers are at the frequency you want the subwoofers to take over. Then you turn down the bass from that point downwards in the frequency response thus making the woofer work less. It's a less satisfactory way than actively crossing over the main woofers but can also help. Many subwoofers have built in crossovers these days and the best way to do it without adding another component or DSP is to use the pre-out into the subwoofer, and use its crossover and use the subwoofer out back into the power amp in.

[G-Dubz]

2 hours ago, Tubularbells said:

Apologies if I missed your post but did you try my suggestion of grounding the black wire to the chassis of either the amp or other equipment?

 

IMO your making it harder than it needs to be by using a RCA cable just to ground the sub. It should definitely work using just the yellow and red wires though as I and many others have used this approach to connect to class D or bridged amps in the past.

Thanks for the reply.

 

I haven't tried grounding the black cable to the chassis, but it seems like the sub sound disappears as soon as the black cable is taken out of the L- Poweramp port.

 

Thanks for the feedback that red and yellow should work. 

 

Perhaps either the cable is broken, or the amp doesn't like the yellow and red cable only, but that would be odd because the Kef LS50's which are connected to the same amp outputs work fine.

 

So it must be something to do with the speakon cable, or the sub.

 

Bit of a predicament, leaving the black cable in on a class D amp is too risky. I've googled high and low and noone else on the internet has reported this problem of no sound from yellow or red. This R305 is super old so out of warranty, I'm not sure REL would help..Maybe I should just bail on the speakon cable and use the low level RCA inputs. Pretty frustratingly niche problem though, was hoping to be good to go with the whole set up.

 

Surely Primare Class D amps can't all be incompatible with these sorts of subwoofers?

Edited April 9, 2019 by G-Dubz

[tubularbells]

Is the REL plugged into a different power point than the rest of the system?

 

If so another thing to try is running the REL from the same power point as the amp as that can also reduce hum.