NEED ADVICE: Biamping vs. dual bridged monos

[Audiophile NewB]

I am now the proud owner of two Classe CA-100 power amps. I had one, loved it, then saw another available at an excellent price and couldn't walk away without it. So now I've got two.

...But now I need some guidance. With two 2-channel amps, what is the best way to power my speakers (Magnepan 3.5 in stock form, no modifications)?

I could use the CA-100s in mono mode; in mono mode they are rated (per the manufacturer's specs) for 350 watts each into 8 ohms, or 600W into 4 ohms.

Or I could use them in stereo mode and bi-amp my Maggies.

Which method is generally regarded as the better method?

If I go with bi-amping, then I need to get a new preamp because my old Denon preamp has only one set of pre-outs. Or is there a suitable way around that too?

Any insight you all can provide is greatly appreciated. As you can tell, I didn't put a lot of planning and forethought into this, I just saw a great deal on a Classe CA-100 and couldn't walk away from it.

Thanks!

 

[j_garcia]

I've never seen any receiver or pre/pro with dual preamp outs. You would just use a splitter. Regardless, I would just run them bridged.

 

[Audiophile NewB]

Thanks! Are there any concerns with bridging the amps to run in mono?

 

[GranteedEV]

Thanks! Are there any concerns with bridging the amps to run in mono?

If your speakers are 4 ohms, then bridging an amp to drive them will present the amp with a 2 ohm load.

If your speakers dip to 2 ohms, that means your amps will see a 1 ohm load.

So thus, you need to make sure your speakers won't have high current demands because the amp will see a low impedance.

 

[markw]

To totally avoid that low impedance thingy, I'd just vertically bi-amp them for now. At some point I'd look into getting hold of an active crossover to do it the right way though.

 

[j_garcia]

Yes, if they are low impedance, bridging could be an issue. When you bridge, you also lower the limits of the amp, but it should tell you what impedance it will be stable to when bridged. Most amps that are 4 Ohm stable during normal operation are only stable to 8 Ohms in bridged mode.

 

[Audiophile NewB]

If your speakers are 4 ohms, then bridging an amp to drive them will present the amp with a 2 ohm load.

If your speakers dip to 2 ohms, that means your amps will see a 1 ohm load.

So thus, you need to make sure your speakers won't have high current demands because the amp will see a low impedance.

Thanks. I'm not an electrical engineer so you guys are talking over my head. My Maggies are 4 ohms. What is the upshot of the low impedance? Would this put the amps at increased risk of blowing? Worse yet, would this put my speakers at risk of being overdriven?

 

[j_garcia]

There is no "upshot" exactly. Lower impedance loads draw more current from the amp, so running them bridged definitely increases the chances of damaging the speakers. I did not know the Maggies were 4 Ohm or I would not have suggested bridging.

 

[markw]

What is the upshot of the low impedance? Would this put the amps at increased risk of blowing?

Simply put, yes. Amps really, really don't like low impedances.

 

[Audiophile NewB]

To totally avoid that low impedance thingy, I'd just vertically bi-amp them for now. At some point I'd look into getting hold of an active crossover to do it the right way though.

Thanks.

Vertical biamping is each amp driving one speaker, both high and low, correct? What is the best way to connect the preamp to the amp and then the amp to the speaker in a vertical biamp setup?

 

[GranteedEV]

Thanks. I'm not an electrical engineer so you guys are talking over my head. My Maggies are 4 ohms. What is the upshot of the low impedance? Would this put the amps at increased risk of blowing?

Let's start with your speakers. The magnepan 3.5 correct?

I was unable to find an impedance chart for it but if the successor the 3.6 is any indication:

These are a pretty benign 4 ohm load - almost resistive for most of the audio band. I don't think the 3.5s would be TOO different. The 3.6s are 86db sensitive which is below average.

Now classe's spec sheet rates these as

600 Watts into 4 ohms (Mono)

Which implies that these are in fact bridgable into a 4 ohm load. It should be stable driving the 3.6s at least. 600w into 4 ohm + 86db/2.83v/m on paper should be getting you 100db peaks at your listening position. On paper though. I noticed this looking up your speakers:

REVIEW: Magnepan Magneplanar MG3.5R Speakers - jimmyjames - Planar Speaker Asylum

You can rock out with the 3.5R but not loud and not long without blowing fuses. I had these speakers through 3 amps, 2 different vintage Adcoms and a Mark Levinson 332 and if it got loud loud, the speaker fuses blew.

So chances are, all that extra power is pretty redundant because you'll just blow your fuses Not a big deal if you don't listen that loud. But yeah... your best bet...

...
.....
..........

Is to buy some new pair of speakers for that new 2 ohm stable 100wpc Classe Amp of yours

Two pairs of speakers for two amps

 

[j_garcia]

Thanks.

Vertical biamping is each amp driving one speaker, both high and low, correct? What is the best way to connect the preamp to the amp and then the amp to the speaker in a vertical biamp setup?

preamp out to Y splitter to each amp channel.

Which implies that these are in fact bridgable into a 4 ohm load.

Figured Classe would be hefty, but 4 Ohm bridged capable is a fairly stout amp.

 

[markw]

Thanks.

Vertical biamping is each amp driving one speaker, both high and low, correct? What is the best way to connect the preamp to the amp and then the amp to the speaker in a vertical biamp setup?

for one channel:

Get two "Y" connector with one male and two female connectors.

Take one "Y"connector and plug the male into one channel of the preamp out.

Get two interconnects. Plug one into each female connector of the "Y" connector and the other ends into each of the inputs of two channels of the power amp.

Using two speaker cables, connect one channel of the power amp into the high connector of the speaker and the other channel into the low connector of the speaker. It doesn't matter which channel is which.

Repeat the process for the other channel.

 

[Audiophile NewB]

Also, which manufacturers (or specific models) of active crossovers would you recommend?

 

[Audiophile NewB]

So chances are, all that extra power is pretty redundant because you'll just blow your fuses Not a big deal if you don't listen that loud. But yeah... your best bet...
...
.....
..........
Is to buy some new pair of speakers for that new 2 ohm stable 100wpc Classe Amp of yours
Two pairs of speakers for two amps

Ugh. My wife would tell you that this is typical of me; jumping into something without thinking it all the way through. ...But I just couldn't walk away from such a good deal on the amp.

Now I've got to figure out how to make this work ... or I'll never hear the end of it.

 

[markw]

Also, which manufacturers (or specific models) of active crossovers would you recommend?

I'll have to beg off on this one. I've never found biamping necessary for home usage. Now, when I did sound work for the churches in this area, the company I partnered with for sound reinforcement for pro concerts used quad amping but that's a totally different matter, and a totlly different venue.

 

[j_garcia]

If you are indeed a NewB as you say, I'm not sure I would recommend the path of active biamping.

 

[GranteedEV]

Also, which manufacturers (or specific models) of active crossovers would you recommend?

I can't imagine much improvement from an active crossover in your case; and it would have potential to make things worse rather than better.

If you insist though, a DEQX:

DEQX Products

would be my choice.

 

[Audiophile NewB]

I think I am what you would call a newbie. Only a few years ago I was listening to a pair of Klipsch bookshelf speakers driven by a Denon receiver and sourced by a very basic Sony CD player.

Then I bought a pair of Magnepan MMGs, which suited me fine until this past spring when I saw a pair of Magnepan 3.5s being sold on CraigsList of all places. They were a steal at only $1,500 so I had to buy them! (This is a recurring theme, as you will see.)

Of course, the 3.5s required more power so I set out in search of a decent amp at an affordable price. A friend turned me onto AudiogoN, where I bought my first Classe CA-100 amp.

I then happened upon a good deal on the Denon 3910 disc player, so I had to buy it. Only $250 for a $1,500 disc player; how could I walk away from that?!

Of course all these "great deals" somehow seem to lead to a need for more expensive equipment.