Opinion of using the Emotiva XPA-DR1 to power a Martin Logan Focus Center Channel speaker

[Robert D]

I'm powering a pair of Aerius i with XPA-1 Gen monoblocks. I'm not having any issues besides the speakers being too bass shy.

This is what I was referring to.

XPA-DR1 Differential Reference™ Monoblock Power Amplifier

The XPA-DR1 monoblock power amplifier provides massive power, superb dynamics, incredible resolution, and maximum control giving you the best sound. Shop today!

emotiva.com

I was going to get it, notice it's quite a bit more expensive than the xpa-hc1.

XPA HC-1 High Current Monoblock Amplifier

The XPA HC-1 is a true monoblock power amplifier and features a single high-power XPAGen3 amplifier module, powered by its own dedicated massive switch mode power supply (SMPS). Shop today!

emotiva.com

I called Emotiva and got a great tech on the phone. She warned me not to use a differential amp on powered speakers. She said that it could very well damage my speakers.

I think what you have is not differential. I think the differential amps they have are a relatively new model.

 

[RCHeliGuy]

I'm currently using an XPA-2 Gen 2 which has been working well for me for a number of years, but it is a more traditional type A/B amplifier.

I heard numerous complaints and issues with a number of the newer designs starting with Gen 3 being a bad match for electrostatic speakers, but I haven't been on their forums in a very long time.

What's interesting is that there are some Class D amps out there that apparently work very well with ML's, but Emotiva had a lot of issues with theirs.

 

[Russr]

I agree, Leporello. I talked with Martin Logan about this topic, and they disagreed. Also, many Magenpan users use differential amps to power their setups with no issues.

I also think about scores of end users that utilize differential amplifiers from PS Audio and ATI Pure Balanced designs. I cannot find end users who have issues with planar or electrostatic speakers, whether passive or powered.

I'm about to buy a pair of Emotiva XPA-1 Gen 2s from a dealer who ran several of them in his theater with Magnepans. He had no issues.

Hi folks

Just a quick note about Maggies/Magnapans when compared to ML/ESLs in general:

While they sort-of have a similar form-factor, the mechanism/technology of the Maggies is totally different from MLs. Yes, they are both planar-looking dipoles. They both use Mylar membranes. That's where the similarity pretty much ends.

Maggie Panels are Mylar membranes with voicoil-type structures bonded to the membranes. There is a solid planar surface behind the Mylar membranes (with slots cut in it, if I remember correctly) with strips of rare-earth magnets arranged vertically. As the design developed, the inventor (Jim Winey) used aluminum strips (foil?) for (some?) voice-coil material in order to maintain a nominal impedance of 4 Ohms. (Great story here: Magnepan Speakers: A Different Approach ). I seem to remember trying to repair some Maggies (back in the late 80's), and the voice coils looked a bit like piano wire... but maybe I am conflating with different speakers).

In summary, Maggies are easier to drive that MLs and have no power supplies.

p.s. Something I got from the article was the use of the DWM Bass panels... might try a set when $$$ are no longer in short supply... might be just what the doctor ordered to work with my SL3's!

 

[Leporello]

You won't have trouble with the XPA-1 Gen2 amp and ML speakers or Magnepans. It's not the same design as the XPA-DR series amps from Emotiva which are a Bridged design so speakers lower than 4Ω are too low for this amp series.

As far as I know the ML Masterpiece speakers are not a Common Ground design. I just checked mine and there is no common connection between Ground and either speaker terminal so any amp should work fine with regards to the ground issue, whether differential or not. A bridged amp is a different matter, as bridging reduces stability into low impedance loads.

An example of a Common Ground component that can be connected to an amplifier, but should not be "fully" connected to a differential amp, is a subwoofer like my Rel. My Rel is a Common Ground design. The Black wire should not be connected to the Negative speaker output terminal of a differential amplifier, but instead, it should be left unconnected. The reason is that the Rel's Black wire is connected to Ground, all the way to the power outlet.

It's a mistake, though, to conflate "differential" and "bridged". A differential amplifier is simply a gain block with two inputs--an "inverting" and a "non-inverting"--symbolized by a triangle with a plus and minus sign on the input end. Whether or not the output is referenced to ground is a whole other matter. A bridged amplifier is one made up of these gain blocks arranged to output two out of phase signals. Grounding one of these outputs will at best, disable half the output and at worst, cause a DC short which the amplifier definitely will not like.

There are two issues with amps whose outputs float with respect to ground. The first is if you attempt to implement Haffler-style passive sum and difference channel speakers, or a passive subwoofer that sums the two speaker inputs. Neither use case is very common today. Today anyone interested in multichannel audio is going to have some sort of avr or pre-proc, and even when using the speaker inputs to the sub, afaik all of them use electronically isolated L and R channels.

The other is that each amp sees half the impedance compared to one of them driving the same speaker, which you definitely do not want to do with problematic loads such as ESL's or ribbons.

 

[ttocs]

The Emotiva DR series amps cannot handle low impedance. Yes, they are differential, but

It's a mistake, though, to conflate "differential" and "bridged".

This is a quote from Keith at Emotiva speaking to the question "XPA vs DR Amps - What is the difference?":

"
In terms of cost and complexity.... each channel on an XPA-DR is equivalent to two high-power channels on an XPA Gen3 and uses two amplifier modules.

A fully differential balanced amplifier has two amplifier channels operating in a bridge mode.
In electronic terms, each of those two modules sees half of the impedance of the load....
So, in terms of load, when you connect an 8 Ohm speaker, each module sees 4 Ohms, and when you connect a 4 Ohm speaker, each module sees 2 Ohms.
Because each module on the XPA-DR is expected to see a lower load, the power supply in the XPA-DR is configured to supply a lower rail voltage.
It's basically the same power supply - but set differently.
(A lower rail voltage enables the amplifier to operate more efficiently into lower impedance loads.)
"

The way I read this and other explanations by Keith, any speaker connected to a DR series amp will be seen as half the load of what it really is. So if it's a 2Ω load, the amp will see that as a 1Ω load, and the minimum impedance of a 13A, 0.7Ω, would be seen as 0.35Ω, which is something a DR series amp does not want to see.

 

[Robert D]

The Emotiva DR series amps cannot handle low impedance. Yes, they are differential, but

This is a quote from Keith at Emotiva speaking to the question "XPA vs DR Amps - What is the difference?":

"
In terms of cost and complexity.... each channel on an XPA-DR is equivalent to two high-power channels on an XPA Gen3 and uses two amplifier modules.

A fully differential balanced amplifier has two amplifier channels operating in a bridge mode.
In electronic terms, each of those two modules sees half of the impedance of the load....
So, in terms of load, when you connect an 8 Ohm speaker, each module sees 4 Ohms, and when you connect a 4 Ohm speaker, each module sees 2 Ohms.
Because each module on the XPA-DR is expected to see a lower load, the power supply in the XPA-DR is configured to supply a lower rail voltage.
It's basically the same power supply - but set differently.
(A lower rail voltage enables the amplifier to operate more efficiently into lower impedance loads.)
"

The way I read this and other explanations by Keith, any speaker connected to a DR series amp will be seen as half the load of what it really is. So if it's a 2Ω load, the amp will see that as a 1Ω load, and the minimum impedance of a 13A, 0.7Ω, would be seen as 0.35Ω, which is something a DR series amp does not want to see.

Thank you for that explanation. That makes a lot of sense. I didnt know those facts. I just know what the tech at Emotiva told me on the phone, to not use the differential amp on a powered speaker like Martin Logan. That amp would be great for a standard cone speaker though I would surmise.

That makes sense too because if you look at the stats on the two amps, the differrential amp is 650 watts vs 300 watts on the regular XPA.

 

[ttocs]

With regards to concern about "reference to ground" with our speakers which have active components, being curious, I checked my Expression speaker and Ground is not tied to either of the speaker posts. Not being one to accept this as proof that it's ok to connect any amp to any speaker, I sent a question to PS Audio since most of their amps are bridged according to Paul.

PS Audio specs show that low impedance doesn't seem to be a factor in determining worthiness with ML speakers, and their amps are built very well and are designed to overcome some shortcomings of being bridged. So my question to them is, should one be concerned with connecting one of their bridged amps to a speaker with active components?

 

[ttocs]

That amp would be great for a standard cone speaker though I would surmise.

I think it's just that the Emotiva XPA-DR series amps aren't designed for low impedance, just more Watts. So while they could've designed the amps to handle lower impedance loads, it would make the amps more costly, so my thinking is that they wanted to design to a price point.

 

[SKY888]

I have 3 emotiva HC-1 monoblocks running my LCR (ESL9 and c18).
I’m very happy with them, and never had any issues even when I go close to reference level volume

I bought them over DR-1 because this is what Emotiva told me:
“I would recommend the HC-1's over the DR2 for one primary reason. The DR amps are fully differential, using two amplifiers in a bridged, differential configuration. Electrostatic speakers like your Martin Logans produce a highly capacitive load to the amplifier, which can cause issues with the fully differential amps that really see half of the rated impedance of the speaker the way the differential amps are configured. We do not recommend using the DR amps with electrostatic panels.”

 

[Robert D]

I have 3 emotiva HC-1 monoblocks running my LCR (ESL9 and c18).
I’m very happy with them, and never had any issues even when I go close to reference level volume

I bought them over DR-1 because this is what Emotiva told me:
“I would recommend the HC-1's over the DR2 for one primary reason. The DR amps are fully differential, using two amplifiers in a bridged, differential configuration. Electrostatic speakers like your Martin Logans produce a highly capacitive load to the amplifier, which can cause issues with the fully differential amps that really see half of the rated impedance of the speaker the way the differential amps are configured. We do not recommend using the DR amps with electrostatic panels.”

Right. I did the same thing. I listened to the tech on the phone and got the HC-1 instead of the DR. I'm happy with the amp powering my Focus center channel. Huge improvement over using my Marantz receiver for it!

 

[Robert D]

I have 3 emotiva HC-1 monoblocks running my LCR (ESL9 and c18).
I’m very happy with them, and never had any issues even when I go close to reference level volume

I bought them over DR-1 because this is what Emotiva told me:
“I would recommend the HC-1's over the DR2 for one primary reason. The DR amps are fully differential, using two amplifiers in a bridged, differential configuration. Electrostatic speakers like your Martin Logans produce a highly capacitive load to the amplifier, which can cause issues with the fully differential amps that really see half of the rated impedance of the speaker the way the differential amps are configured. We do not recommend using the DR amps with electrostatic panels.”

Right. I did the same thing. I listened to them and got the HC-1 instead of the DR. IM happy with the amp powering my Focus center channel. Huge improvement over using my Marantz receiver for it

 

[Robert D]

 

[codesx100]

Right. I did the same thing. I listened to them and got the HC-1 instead of the DR. IM happy with the amp powering my Focus center channel. Huge improvement over using my Marantz receiver for it

The focus definitely needs its own power amp. I ran it off a receiver once just to see and it was nowhere near as good.

 

[Robert D]

The focus definitely needs its own power amp. I ran it off a receiver once just to see and it was nowhere near as good.

The receiver I use was one of the top two offered from Marantz, so it did ok but using the Emotiva monoblock produced a noticeable difference. It wasn't incredible, but noticeable. Definitely worth just under $900. I was kinda surprised how well the Marantz did driving the ML center channel speakers. I used it on both the theater i and the new Focus. So when I compared the theater i sound to that of the new Focus, I was using the Marantz on both. It was a bigger upgrade going from the old ML speaker to the new, and then using the monoblock was another small increase in sound quality.

 

[ttocs]

With regards to concern about "reference to ground" with our speakers which have active components, being curious, I checked my Expression speaker and Ground is not tied to either of the speaker posts.

On the Masterpiece speakers with powered woofers, the amps are indeed GROUNDED via capacitors so this cannot be properly checked without power being applied.

So, the Emotiva DR series amps cannot be used with these speakers. I spoke to Lonnie from Emotiva at AXPONA about this and he remembers the discussion about this with an MLO member. ML gave him schematics for the woofer amps and there are some capacitors TIED TO GROUND as a safety design. This is what can make the Emotiva DR amp go into protection.

 

[Robert D]

On the Masterpiece speakers with powered woofers, the amps are indeed GROUNDED via capacitors so this cannot be properly checked without power being applied.

So, the Emotiva DR series amps cannot be used with these speakers. I spoke to Lonnie from Emotiva at AXPONA about this and he remembers the discussion about this with an MLO member. ML gave him schematics for the woofer amps and there are some capacitors TIED TO GROUND as a safety design. This is what can make the Emotiva DR amp go into protection.

Ok. I called in and was told not to use the DR amp, but I guess I could have because I was just using it on a Focus center channel. The tech said not to use them on ML speakers since they are powered. So having the es panel powered isn't an issue?

 

[ttocs]

Ok. I called in and was told not to use the DR amp, but I guess I could have because I was just using it on a Focus center channel. The tech said not to use them on ML speakers since they are powered. So having the es panel powered isn't an issue?

No, not an issue with the stat panel getting power to energize it. It's only a problem with the internal amps that power the woofers on the Masterpiece speakers which have a path to ground via the capacitors that are there specifically for grounding.