Subwoofer standby tragedy

[Misterer]

I've just got a Kube 12b sub which has an auto standby feature - it turns on or off based on received audio signal. The problem with that is that it won't turn on until "sufficient" bass is played and it will even turn off during longer lasting audio tracks without enough bass. I could probably live with this if it worked correctly but it doesn't - the sub needs "lower" bass to trigger it to turn on than it is configured to play (simple test: play a track which doesn't trigger it (sub off), play another one which does (sub turns on), continue the first one (sub can be heard playing)).

It also doesn't have an "always on" mode (which would obviously solve the issue). I do like the sub otherwise so before I return it, is there anything I could do to make it turn on immediately and stay that way? Some say a Y cable could help but it doesn't look like a guaranteed solution - a minor improvement maybe?

I tried setting sub level to +9db on the receiver but that didn't seem to help.

I don't see many complaints about this on the net and I wonder why. To me it is completely unacceptable for a sub to turn on/off randomly.

 

[restorer-john]

Unfortunately it's a badly designed or faulty auto sense trigger. Such circuits are electronics 101, but it amazes me manufacturers can't get them right.

Unless you have a schematic and want to modify the design, I'd simply send it back as faulty.

 

[Slayer]

I don't see many complaints about this on the net and I wonder why. To me it is completely unacceptable for a sub to turn on/off randomly.

First off, restorer-john is a 100% correct.
Secondly, this probably doesn't help you seeing as you have a different brand of sub. My Monoliths were doing the same thing as you described when I first got them. Strangely enough, after 3-4 days or so, they began working as they should. Couldn't tell you why that is.
You might play with your subs volume (input sensitivity) knob, see if that does anything to help you out. Also, if using RCA connections, a Y cable couldn't hurt.
Not sure of your receiver, but no, you should need to add +9db on the sub pre-out. I personal try and keep the pre or receiver at zero and set the sub vol according on the sub itself. Others run the sub itself a little hot and have their receiver or pre in the negatives.

 

[Beershaun]

What receiver or pre amp are you using with them? I have noticed with mine that my Anthem triggered my subs on much faster and more reliably than the NAD that preceded it. Could this be related to the voltage being sent out by the receiver being insufficient?

 

[Misterer]

The receiver is X2700H. I have set the volume on the sub to ~50% and +9db on the receiver (if I set it to 0db, I can barely hear it). Is this unusual?

 

[SKBubba]

Could have something to do with receiver settings.

Front small v large, lfe v lfe+main, stereo v direct (although it wouldn't plat at all on direct)?

But if all that is correct or reasonable, sounds like poor signal detection on the subwoofer.

 

[Chrispy]

The receiver is X2700H. I have set the volume on the sub to ~50% and +9db on the receiver (if I set it to 0db, I can barely hear it). Is this unusual?

50% gain on the sub is just a suggested starting position for running Audyssey. Does sound like your pre-out level could be too low still. Did you run Audyssey?

 

[MattJ]

My Polk sub had to run the input volume around 1:00 (60%) to get reliably meaningful output.

 

[wwenze]

There are apps designed to prevent speaker from standby by playing an inaudible sound once in a while. In your case you might have to choose a <20Hz sound.

 

[MCH]

There are apps designed to prevent speaker from standby by playing an inaudible sound once in a while. In your case you might have to choose a <20Hz sound.

I experimented with a similar approach to this but more rudimentary: created a barely audible signal with Audacity that i could add at the beginning of playlists to wake up the amplifier before the music starts...
Any example of the apps you mention? How do they play simultaneously to the music/film? Do you need to plug like a second set of line cables with a Y connector?

 

[dougi]

I used to have this problem with my sub. If you are only using one RCA as input for LFE, connect a small automated MP3 player with some low bass tones on it to the left RCA and play it when you need to wake it up. I did that for years until the whole amp failed. After it was repaired, the auto sense was fine. Must have been a design revision.

 

[HarmonicTHD]

The receiver is X2700H. I have set the volume on the sub to ~50% and +9db on the receiver (if I set it to 0db, I can barely hear it). Is this unusual?

The receiver should get its volume setting from the Audyssey measurements. If I understand correctly, Audyssey sets it to plus 9dB, which indicates that the volume setting on the sub can be increased. I would set it so Audyssey comes back with 0dB or even slight negative values and see if this helps. Otherwise I would send it back. (The KC62, KF92 work, but those are a vastly different price range. Regardless you should have to put up with this regardless of price).

 

[Misterer]

Thanks for all your replies, I guess I can't be bothered with implementing workarounds. I'm just going to return it and get a sub which would allow me to disable this autosense nonsense.

 

[HarmonicTHD]

Thanks for all your replies, I guess I can't be bothered with implementing workarounds. I'm just going to return it and get a sub which would allow me to disable this autosense nonsense.

Did you try what I suggested above. I can only recommend it as other subs might also exhibit the problem when fed a relatively low signal, in your case ca. -9dB. After that you can still return it.

 

[Chrispy]

Thanks for all your replies, I guess I can't be bothered with implementing workarounds. I'm just going to return it and get a sub which would allow me to disable this autosense nonsense.

Many subs do have an auto on function. I'm still thinking you've not set it up ideally myself....and if the current sub has a simply on all the time feature, you might just use that.

 

[Grateful Garret]

Hi there. I recently bought 2 of the KUBE 12b and what a mess this auto shutoff thing is. I think these will be going back. Contacted the seller and they said turn the sub out on the parasound halo p6 all the way up and the sub volume down (now at less than a 1/4 on the dial). Got the subs to turn on and then turned volume down to a nice quiet volume for sitting by the fire and drinking tea. Jazz with bass and drums. Within 10 minutes, both subs had shut off and I had to jack the volume up on the preamp to get them to turn on again. I’m an old audio salesman and this simply will not cut it. Just wondering if anyone on this old thread had a workaround that I hadn’t thought out. I guess I know why their new KUBE subs have an always on feature. Guess that there were a lot of us having this issue.

 

[Beershaun]

Hmm. It sounds like the line level signal to the sub is too low for it to stay on. Have you attempted to contact Kef and get their recommendations based on your setup? They may be more knowledgeable than the previous owner. There may be a setting you can adjust in the app. Also, you could try plugging both RCA subwoofer outs (assuming you are only using one) into the Kube to see if that helps with lower volume signals.

 

[Grateful Garret]

Hmm. It sounds like the line level signal to the sub is too low for it to stay on. Have you attempted to contact Kef and get their recommendations based on your setup? They may be more knowledgeable than the previous owner. There may be a setting you can adjust in the app. Also, you could try plugging both RCA subwoofer outs (assuming you are only using one) into the Kube to see if that helps with lower volume signals.

Thank you for the reply, my friend. I’ve got two sub outs on the parasound preamp into the KEF wireless set up so I can place the subs in the right places. Had the same set up with my previous SVS subs (which now I wish I would have kept) and they did not have this issue. Sub gain is turned ALL the way up on preamp so full signal going to subs, but still shutting off at nice low volumes and then I have to jack up volume to turn them on again. I can get sub cables out but it’s not practical for where i need to place them for best audio. I may just return these and go back to my old SVS set up. Like I said, I think this is why the newly released KUBES have an always on feature, methinks this has been an issue for many.

 

[Chromatischism]

If your sub has two inputs, you can increase the signal by using a Y-RCA cable. Sounds weird, but people on AVSForum have been doing it for a while.

 

[Grateful Garret]

If your sub has two inputs, you can increase the signal by using a Y-RCA cable. Sounds weird, but people on AVSForum have been doing it for a while.

The Kef wireless set up uses a unit that is attached directly to the rear of the subwoofer. If I use sub cables, I’m going to need to rearrange placement and I’ve got these in just the right spots for my listening position. BUT, I will try the y-cable if I break out the sub cables and see and appreciate this suggestion. Thank you.