[opnly bafld]

Depends.  In some cases, agree.  However, there are exceptions to this.  Some amps have sufficient engineering where bridging with low(er) impedance speakers is not an issue.

Do you have an example?

[Freo-1]

McIntosh  amps with autoformer output. 

[opnly bafld]

McIntosh  amps with autoformer output.

I wouldn't call that "sufficient engineering", more a design choice, and none of the current 2 ch amps that I saw on their website can be used mono.

[Freo-1]

A good design choice IS sufficient engineering.   


The Devialet Expert Pro amps are better in mono,  and can handle most lower impedance loads.   There are a few speakers that are truly punishing loads, and those require a very high current amp, which would exclude the majority of amps. 

[opnly bafld]

I didn't say a "good" design choice, some think it is, many disagree.

Thought we were discussing possible disadvantages to bridged amps, no doubt reduced ability to drive lower impedance loads is one. There are a surprising number of speakers that drop below 4 ohms.

At least you had an opportunity to get your Devialet plug in.

[Freo-1]

Of course many speakers drop below 4 ohms for certain frequencies.  However,  most don't live below 4 ohms across the spectrum.  If one's chosen speaker does live in the low impedance across the board, then one should consider something along the lines of Pass Labs offering. 


Another amp that I know works fairly well bridged into lower loads is the Primare A34.2. 


The Devialet amps with Speaker Active Matching allows the supported low impedance speakers to be driven safely.  Good engineering.

[mresseguie]

Hello, Freo-1.

I looked into Devialet a while back after you mentioned them to me. Their SAM technology does sound very attractive. However, in my case, Devialet has not added Daedalus speakers, Jeff Bagby speakers, nor Fritz Speakers to their list, so I cannot take advantage of that bonus.

Michael

[Freo-1]

Hello, Freo-1.

I looked into Devialet a while back after you mentioned them to me. Their SAM technology does sound very attractive. However, in my case, Devialet has not added Daedalus speakers, Jeff Bagby speakers, nor Fritz Speakers to their list, so I cannot take advantage of that bonus.

Michael

Hi Michael,


The SAM function currently supports 1000 speakers, and the number continues to grow.  There are so many boutique speaker manufactures out there, it's impossible for them to cover them all.  I can report that it works great, as it extended the LF of my Dynaudio Focus 360 all the way down to 18 Hz.


Regarding this topic, mono amps can provide several benefits over a single stereo amp.  Regarding bridging amps, as long as the speaker doesn't go much below 4 ohms for a large part of the frequency spectrum, the extra power is welcome.  If the speaker is a difficult load, then it's usually better to not bridge amps, and use a voltage source amp that can support the tough impedance loads, such as Pass Labs offerings. 

[Falcon]

Thanks for added clairification Speedskater: Yes, mono bridge mode is what I meant to say...

[opnly bafld]

Regarding bridging amps, as long as the speaker doesn't go much below 4 ohms for a large part of the frequency spectrum, the extra power is welcome. 

There are a lot of bridgeable amps that don't like a load much below 8 ohms since the bridged amp sees an 8 ohm load as 4 ohms and a 4 ohm load as 2 ohms. Better off using them as a 2 ch amp with 4 ohm speakers; no extra power in these situations.

[Freo-1]

There are a lot of bridgeable amps that don't like a load much below 8 ohms since the bridged amp sees an 8 ohm load as 4 ohms and a 4 ohm load as 2 ohms. Better off using them as a 2 ch amp with 4 ohm speakers; no extra power in these situations.

Agreed.  Would not in general use bridged amps with nominal 4 ohm loads. 


There are a few exceptions, such as some of the better legacy McIntosh amps with autoformers.  For example, here are the specs for a MC2500:

ELECTRICAL500w/ch. (1000w mono). Response 20-20kHz (+0 -0.25dB). Distortion 0.02%. Noise and hum -95dB. Output impedance 1, 2, 4, and 8 ohms. (0.5, 1, 2, 4, 8 and 16 ohms in mono). Damping factor 30 or greater. Input impedance 50k. Input sensitivity 0.75v or 2.5v. Sentry Monitor. Power Guard.


I've also successfully used Primare A34.2 amps bridged in mono with Dynaudio Focus 360 (nominal 4 ohm load) with no issues. 

[Speedskater]

Making amplifiers that work well into low impedance loads is expensive. Making two channel amps that can be bridged into low impedance loads is even more expensive.
Now, new modern Class "D" amps are changing that, But some Class "D" amps can't be bridged and others lose quality when bridged.

[Dormouse99]

Agreed. I'm getting my first set of monoblock amps fairly soon, two Hypex NC1200s. It's remarkable what's happening with Class D amps. A few years ago, NC1200 amps cost as much as a small car. Now they can be had for about $1000 per monoblock. While these types of Class D amps can't be bridged, they are putting 400W into 8 ohms and 700W into 4 ohms. So that's a bit.

[emailtim]

Agreed. I'm getting my first set of monoblock amps fairly soon, two Hypex NC1200s. It's remarkable what's happening with Class D amps. A few years ago, NC1200 amps cost as much as a small car. Now they can be had for about $1000 per monoblock. While these types of Class D amps can't be bridged, they are putting 400W into 8 ohms and 700W into 4 ohms. So that's a bit.

Be sure and report your findings on the NC1200.

FWIW, the previous high cost of the NC1200 amps was due to Hypex's minimum pricing policy for those boards which has since expired allowing more vendors to have access to them.