Monoblocking Amps

Gang

Just feeling a bit nervy now that I have organised a second Nad 218 to monoblock with my existing one.

In the Manual it states :

" In the bridged mode the loudspeakers impedence is effectively halved as seen by the amplifier. An 8 ohm load looks like 4 ohms, a 4 ohm speaker load looks like 2 ohm, and a pair of 4 ohm speakers operated in parallel will resemble a 1 ohm load.

Driving paralleled speakers low impedence speakers to high levels may cause the amp to overheat and shut down. or may cause internal fuses to blow in order to protect the amplifier.

In bridged mode you must connect only ONE loudspeaker whose normal impedence is 8 or higher "

Now, I'm running a pair of Dynaudio Audience 10's which are 4 ohm - are these OK to run ?

I won't be biamping - Dynaudio only have one set of terminals as they don't believe in biamping.

Any help/advice much appreciated.

 

Seems quite clear.

So clearly not OK.

Just use a single channel of each amp, rather than bridge both channels in each amp. Or sell both amps and buy one better one.

Paul

 

hmm I know nad amps are beefy, and a lot of speakers are conservatively rated, so some 8 ohm ones will go a lot lower.
I would try it, its only going to be at high levels problems creep in, so start of low and raise the vol.
After 20 mins, feel the tops of the amps, and see how warm they are.
If they cut out, they will recover, its like a trip, so you will roughly have an idea how to use them.
And fuses are a piece of cake, these will be for more serious abuse.

connect one amp to one loudspeaker. the other to the other

I think it may be both red terminals on each amplfier, but am not sure, check instructions for wiring carefully.

 

as long as you only connect 1 speaker to one bridged amp you'll probably be ok (as long as the amps can deal with a 2 ohm load).
the worst that will happen (from what you say) is that a fuse will blow. if that happens, replace it and don't run the amps bridged.
cheers


julian

 

What's the point of bridging to quadruple power, and then playing quietly?

Contrary to what's reported as being in the instructions the NAD218THX seems to have a specified burst power output when bridged into 4 Ohms. So it shouldn't end up smoking.

But reading between the lines this usage looks like being intended for subwoofer type use, it may not sound as good as using the amp unbridged. And do you really need more than 200W?

Paul

 

Gang

Thanks for all your replies - I'll chew on this overnight - never thought for one second that either the Nad or the Dyns could be overpowered (not in the Biblical sense anyway)

When bridged, the Nad will kick out over 600w per amp - perhaps I'm being over ambitious but I always wanted a second 218.........

The question is then, what in hell speakers are designed to take this sorta punishment ?

 

ATC passives can take up to 1500wpc, but I don't think that is the direction in which you need to go.

 

Remember this very apt saying "Too much is not enough"

 

If I were you in run them in stereo one for treble one for bass I think bi amping often sounds better like that than in bridged mono anyway.

Worth a go to see how it sounds.

 

i don't think dynaudios are bi-amp / wire able. i may be wrong though. they also like a bit of a kick up the arse to wake them up by all accounts too.
cheers


julian

 

Julian is correct, Dyns are single wire. Well all the ones i have seen.

 

meh!

 

Yep - single wire only. Dynaudio don't believe in bi-wiring.

Now I'm not technical at all, but what I can't understand is why Dynaudio (which indeed does like a good kick up the ass) now seem to be all coy of a sudden. Or is that the amp's fault ?

Anyway, slowly but surely going off the idea of the second Nad as it looks like I would need to spring for new speakers (and I love my Dyn's)

I was round at an engineer's house this morning with my existing Nad 218, just for him to double check about the voltage conversion from 110 to 240, and after a little internal examination, he pronounced no problem. So I thought I was over my last hurdle.

Anyway, during our conversation he happened to mention he had Krell monoblocks (the baby one's he said), and me being a bit cheeky said "show me".

Bloody hell, he showed me into his listening room but it wasn't the Krells that floored me (or the Wadia CDP), but dominating the room was a pair of Living Voice Air Partners. Jeez, these things are absolutely HUGE HUGE HUGE.

I was sorta gob smacked from there on in. Now I'm depressed.

 

This halved impedance load on bridging has caught a great many people out in the past, NOT LEAST THE DESIGNERS.

To be perfectly honest, a pair of 218s won't sound hugely different to a single 218. Better off selling the first, putting it together with what the second would have cost and buy an S200 or something.

 

I think there are at least 3 of us (4 now ) here who would never hanker after another speaker again after acquiring those. The end of all roads.

 

What bothers me about that post is the Krell mono's, while spoil a decent speaker with those amps?, beyond me & why so much power arn't they some thing like 103db efficent? just need a decent valve amp, job done

 

I did wonder that, for all people who are not sure how this works, you can get 109 dbs out of 4 watts!! of valve amp, and you would need from say 87 db speakers errrr.....

over 150 watts

that's the way to go....

and the main amp maker that makes super amps is....MF...for work stress, life stress, better than valium, panacea for all hassle and bad hair days, better than a hot chocolate and esoteric philosophy book for sleeping at nite, MF 300 watters and spendor spx.

 

I also was wondering about the logic of Krell monoblocks into a pair of horns?!

que?

 

Kudos on hifi forums

Michael.

 

**** Nad