Question Best option to power my passive subwoofer through a Denon 1910 receiver?

Whoozzem

Member
Hi,
I have a subwoofer which was originally active but is notorious for amplifier board faults, so back when it's internal amplifier went for a second time (a year after getting it repaired) I ripped its' internal amplifier out and made the subwoofer passive. Now I have tested it both through a car amplifier (JBL GTO 6000) and my basic USB amplified headphone soundcard (Asus Spitfire) so I know that provided the amplification is there it can work, though this was a few years ago and not used for any length of time.

The receiver I bought for the subwoofer (and speakers - but they're running without issue) was a Denon 1910 however at the time of purchase I didn't realise that the receiver only provided non-amplified output to the subwoofer so I'm wondering what the best way of getting the subwoofer working would be?

I've looked online and the subwoofer is rated at 210W RMS 8 ohm. I don't know if this halves, doubles or does nothing to the subwoofer but currently I have its' two positivie/negative terminals wired out to just one single cable (and this is how it was with the car amplifier and USB soundcard) . Looking online it's described as being a three ringed subwoofer? but only appears to have the two sets of wires connected - unless when I made it passive I broke off a third pair, it has been many years ago since I converted it.

Further online searches have come up with the following three options for powering the subwoofer with the receiver and I'd like someone to clarify things for me as I know next to nothing about sound setup etc.

Firstly if I understand correctly, to convert from RMS back to W would be 210/0.707 so this subwoofer would want a single 300W amplifier for maximum performance, is this correct?

Secondly, I did find an old site where someone with this speaker system/subwoofer set up their Denon (a 1610) by utilising the Front A+B connection and passing low frequencies through to the subwoofer plugged into Front B.

The manual for my 1910 says that when using Front A+B together never to use anything with an impedence of under 12 ohm because otherwise the system will either overheat or enter protection mode. The subwoofer and speakers are 8ohm so I presume this is ruled out even though someone did this with the other Denon model?

Thirdly I did debate buying a smaller powered amplifier and I did see a 70W RMS (2x35) amplifier in my (now much restricted) budget and I wondered is there any danger/risk to either the amplifier or subwoofer if I used this lower RMS rated amplifier to power the subwoofer, or would it just be quieter?

Thanks.,
 

gibbsy

Moderator
The only way to connect a sub to your receiver is via LFE to powered sub woofer.
 

Rambles

Distinguished Member
I have never tried it, but theory suggests that going from the LFE output of the AVR into a power amp, and connecting the subwoofer speaker connections to that power amp should work.

The Behringer A800 might be good for that, I use one in mono mode on my centre speaker, sounds and measures fine, Class D, very inexpensive, might be worth a try:

 

494930

Distinguished Member
Replacing a subs amplifier is straight forward enough. You need to decide between fitting another plate amp or going outboard with something like a Behringer NX.

The outboard amps usually contain a noisy cooling fan and are a bit less tidy but you get much more power for your money which is why they're the most popular option.

You can't have too much power, the driver will only pull what it needs. It's too little power that is dangerous as the amp clip the signal when it reaches max which then sends a square wave to the driver which can blow them.
 

Whoozzem

Member
Thanks for the replies.

The Behringer models do look nice and I am surprised you can get that power rating for the price. However because the only other three amplifiers I've ever owned all had amplified subwoofer output I put almost all my budget just on the Denon, so my remaining budget is nearer the £20 mark now, hence the question about using a low powered amplifier/ Front A+B.

"You can't have too much power, the driver will only pull what it needs. It's too little power that is dangerous as the amp clip the signal when it reaches max which then sends a square wave to the driver which can blow them. "
Please could you clarify this for me, as if a driver (had to google that to find out what a "driver" was :D) is always trying to pull its' maximum power, doesn't turning the volume down cause this signal clipping to occur since you're (presumably) limiting the amount of power it's getting? And if not, how is using a less powerful amplifier any different to turning the volume down?

Thanks,
 

494930

Distinguished Member
doesn't turning the volume down cause this signal clipping to occur since you're (presumably) limiting the amount of power it's getting? And if not, how is using a less powerful amplifier any different to turning the volume down?
I'll try to explain, it might not strictly be 100% accurate but should demonstrate what I mean.

Lowering the volume attenuates the signal, lowering its amplitude without affecting the shape of the waveform, so you audiio sounds the same just at a lower SPL.
Left: volume down Right: volume up
amp_Strength.jpg

An amplifier with too little power will reach a point where it's unable to cleanly output any more power and will thus have to distort the signal in an attempt to keep up. This pic shows it quite clearly, the blue waveform would be an amp with sufficient power, see how it rises and falls in a smooth arc and never remains at its limit for any length of time. The red waveform is trying to play the same signal at the same level but doesn't have the power to do so, so it ends up sitting hard against the limiter until the power required falls below this level. It's these moments against the limiter that kills drivers.
sine+clip.png

The problem with all this is we don't know how much power you actually need, you may be fine with a low powered amp if you keep your listening volumes quite low and aren't trying to reach the lowest octaves, so i wouldn't recommend using any amp that's rated lower than the one it came fitted with (if you do purchase a lower power amp then listen carefully for any distortion and lower the volume immediately if you hear any). I would run your setup without the sub at all for a while until your able to afford something that is suitable for your needs. What sub is it anyway?
 

Whoozzem

Member
Hi,
Thanks for the explanation, it made it a lot clearer to understand.

The speaker set in question is a Creative Cambridge Soundworks Gigaworks S750.

I don't tend to have the volume too high, in fact currently the Denon is set at -15db which I found through testing earlier today gave the best all round volume for each of the inputs (e.g music from a phone via RCA was a perfect volume even at -20db, but hdmi was just a bit too quiet).

I could crank it up to 0db (sounds weird saying that), but above 0 I did start noticing distortion, but that could be the very old and cheap cable I was using with the phone - which if left unplugged from the phone caused feedback buzzing through the speakers - I hadn't tried upping the volume beyond 0 for the other input types. You can definitely hear the lack of bass / (for want of a better word) punchiness at times though.
 
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494930

Distinguished Member
Ah, that's a system more suited to connection to a PC rather than home theater,and those satelites are going to need a sub to underpin them, but there no reason you cant make it work. Just to confirm, you're using the Cambridge satellite speakers connected directly to the Denon? (Do these specify how many ohms they're rated to on the back of them?) and plan to also connect the Cambridge sub to the Denons LFE output?

The manual specifies the subwoofer amplifier as being 210w (notice how they don't give any info on how that figure was derived ;)). If I had to guess, I'd say it probably has 1/4-1/2 that in reality, so your 70w amplifier you found is quite likely to be better than what it originally had.

My updated recommendation is to keep an eye on Gumtree for subwoofers locally, these things sometimes sell for buttons, I picked up an old REL a few years ago for £30 which would be a massive upgrade on what you have.
 

Whoozzem

Member
Hi,
Yes the satellites are all (well two currently) plugged into the Denon.

- Please see subsequent post for details -

Thanks.
 
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Whoozzem

Member
I have now found enough specifications to say that:

The original subwoofer had three amplifier boards each providing 70W RMS.
The subwoofer driver has three voice coils, one for each amplifier board.
This 3 x 70 is where the subwoofers' 210W RMS rating has come from.
The driver is stamped with 8 ohms, and someone else "Fluke" tested each of their own coils in the past and found each is 8 ohms.

Since originally I'd been told the other 2x35W RMS would probably do (@494930 - I really did look out for active subs first but they were all lower RMS ratings or too far away to collect) I decided to look out for other amps on the off chance I found one more capable.

I stumbled on an 80W RMS @8ohm amplifier (on all 5 channels) so have gone ahead and purchased that.

It looks to be the better bet as it allows passing all LFE through to the speaker outputs and has a single subwoofer input line - that and it was only £5 above my budget.

Again though, thanks for all the previous responses. :)
 
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