Jeff Rowland

Preamp is the same. Power amp modules are what you want to investigate. The Continuum S2 has a Pascal power unit. No idea about 525. Why not call Rowland to inquire.

I called Rowland and they suggested going from my 525 to the
625, which is out of my price range. I'm curious if anyone
on Audiogon has done a direct comparison between the 525
with the Capri 2 preamp and the Continuum S2 Integrated amp?

I think that their suggestion is a good one. I have compared the 525 and 625, and the 625 is clearly a step up in performance. It's more refined overall with improved body, depth and dynamics. The 625 has a more effortless presentation when compared to the 525. Of course that improvement comes with a commensurate increase in price.

I should note that I currently own the 625, so my opinion may be biased accordingly. I'm always looking for another upgrade (sound familiar?), but am having trouble finding something significantly better than the 625 without almost doubling its price. There is no end to the madness of this hobby!

Bill_k,
Thanks for the response. There is no doubt in my mind that the 625 mk2 will be a significant upgrade, but for now it's more than I can spend. I'm currently using a Bricasti M1 direct to the 525. I just added a pair of SVS SB 13 Ultra subs and was wondering if adding a preamp would provide better results...that's why I ask is adding a Capri 2 preamp or getting the Continuum S2 Integrated the best option? I'm biased also and will stay with Jeff Rowland amps. I really love the JR sound.

"I just added a pair of SVS SB 13 Ultra subs and was wondering if adding a preamp would provide better results"

Yes, but you have to get the right preamp.

Zd542 is correct, you need to add a suitable quality preamp to improve the sound of running your M1 DAC direct to your amp. Many preamps will actually degrade the sound, so you would be best off if you could audition the exact preamp you're considering in your system before committing to purchase it. Hopefully that is an option available to you.

Zd542,

Any suggestions on preamps I should listen to? I had a Parasound JC2 BP and to my ears it degraded the sound when compared to the PS Audio DSD I had at the time. The Bricasti M1 sounds much better direct than the DSD.

Why do you think you need a preamp?

I don't know if I need a preamp. I'm looking for the next step forward.

Forward to what? Your system is at a point where you need a clearly defined vision of what you are trying to accomplish. What is that vision?

"The Bricasti M1 sounds much better direct than the DSD."

That's your reference, so whatever you do, you'll need to compare it so you don't make a backwards move. A preamp is a very personal choice. So whatever is recommended, by me or anyone else, needs to be followed up with a demo. I really can't stress that enough. A preamp is the one component you really can't afford to mess up. Also consider that you have good sound now, going direct with your dac. When you already have good sound, its much easier to make a mistake than an improvement.

I'll start off with 2 recommendations. For solid state, I would look at an Ayre K-5, and for tubes, an Aesthetix Calypso. Those 2 pieces do everything right, and work well with a wide variety of components. Either should go very well with your Rowland.

Onhwy61,
I have a clearly defined vision. I want better separation between instruments and better front to back placement of instruments.How to get there(what's my weakest link) and how much it's going to cost is the question? It may be time to investigate replacing my Aerial 7Ts!

I didn't mean to suggest that you didn't have a vision, but that simply that you hadn't stated it. How to achieve your goals is a very different question than what you asked. It's not guaranteed, but everything you want may be had by different loudspeaker/listener positioning.

Onhwy61,
I'm looking into speakers now. A few on my list are Joseph Audio Perspectives and Dynaudio C2s.

"I want better separation between instruments and better front to back placement of instruments.How to get there(what's my weakest link) and how much it's going to cost is the question? It may be time to investigate replacing my Aerial 7Ts!"

At this level, its not good enough to just pick components. In order to get what you are looking for in the above quote, you must consider at the whole system. One mismatched piece can ruin the systems ability to image properly.

Just to give a real example of what I mean, my system consists of speakers and electronics that excel at imaging, scale, soundstage, etc.. I have this one Jeff Rowland amp, and it doesn't matter what system I put it in. With the Rowland, the imaging goes from 3d to 2d. Its just a good example of why you can't take anything for granted when putting together a high end system. Most people would assume an expensive amp like that would automatically work with no problems.

Zd542, would you please share with us what model Rowland amp you are referring to? I'm interested since I've heard many of them and your experience runs counter to mine. TIA

Zd542,
I've owned several amps and listened to several in different systems over the years(Parasound, Bryston, Peachtree, Bel Labs, Classe, Levinson). To my ears Jeff Rowland is one of the few amps that produces a 3d image and I'm very satisfied with the 525, especially for how much it cost.

"At this level, its not good enough to just pick components. In order to get what you are looking for in the above quote, you must consider at the whole system. One mismatched piece can ruin the systems ability to image properly." Okay, but in an earlier post you say "I'll start off with 2 recommendations. For solid state, I would look at an Ayre K-5, and for tubes, an Aesthetix Calypso. Those 2 pieces do everything right, and work well with a wide variety of components. Either should go very well with your Rowland."
My experience tells me that switching one component or cable for that matter can have a significant impact on the sound. Yes, it's a system, but each component can impact the overall signature of the sound. I'm looking for suggestions, but I'll let my ears and wallet decide.

I believe he is referring to the Model 112. I currently use this amp and get great soundstage depth and imaging definition. Not every component will work in every system.

"Yes, it's a system, but each component can impact the overall signature of the sound. "

True, but I'm not sure if you understood the point I was trying to make. Each component does impact the overall signature of the sound. However, you can put a component in the system that takes away from the others. Going back to my Rowland example, when I put it in the system, it doesn't allow the other components to do things they normally do.

Zd542,
My JR 525 replaced a Parasound A21. Prior to purchasing the 525, I had in my system, a Bryston 4bsst2, Ayre integrated, and a JR 125. To my ears and in my system the, with the exception of the bass, the Jeff Rowland 125 was the most musical. I decided to get the 525 based on my evaluation of the JR 125.

Ricred1,

I believe every word you are saying. I just used my Rowland as an example of how things can go wrong when you least expect it. If you chose your Rowland because you liked it best, then you made the right choice. I still keep my Rowland, even though its not currently being used, because it does do things that no other amp I've heard at any price, or design does. Equipment matching is not bashing. Sometimes good components don't work well together.

Zd542,
I know your not bashing...my point is that I "try" to evaluate components in my system. I continue to say, "there are no absolutes in audio only preferences."

That's what I figured, but I just wanted to make sure you didn't take offence to any of my comments.

I had a JR 525 in my system briefly, replacing a monster McCormack DNA-500. I paired it with a Modwright-LS 36.5 preamp. It sounded pleasant enough but I felt it was lacking in dynamics, presence and oomph. I then bought a used JR Continuum S2 here on A'gon and used that in place of the 525/MW and McCormack/MW combos. Much, much better. I sold the 525, McCormack and Modwright -- all great units, but the Continuum sounded at least as good as the McCormack-MW combo and I thought it was appreciably better than the 525-MW combo.

Schacter,

Thanks for the feedback, although I feel my 525 could be better with musical nuance/detail and I'm actually happy with the dynamics. Do you still have the Continuum S2 or do you have the Spectron Musician? If you have the Spectron, how does it compare to the Continuum S2. Thanks!

I have the Continuum S2. I had the Spectron many years ago. I guess I should update my system as it is now completely different.

Schacter,

Please describe the differences you hear between the 525 and Continuum S2...is there a night and day difference?

Hi Richard, I have listened at some length to Continuum S2 and Capri S2… And have heard comparative opinions of Continuum S2 with M525 from people that I respect who have considerable Rowland experience.

Continuum S2 is based on the Pascal M2Pro module, which is a higher end module than the S2Pro used in M525… And the audible results, for all that have listened to them, are quite in evidence… Continuum S2 is extremely textured and marvelously nuanced. By contrast, all comparative findings that I have heard from people in the know, is that M525, while excellent at its price point, might be a little more matter-of-fact and less emotionally involving than Continuum S2.

Continuum S2 delivers 400W with a peak current of 38 Amps…. It will drive anything you throw at it, except some uber-large speakers…. A pair of M525 bridged to mono ops might give you a smidjin more authority than Continuum S2…. At the cost of some subtlety and musicality.

Capri S2 and Continuum S2 share the same/identical preamplification circuit… There is no difference… And yes, Capri S2 is a wonderful preamplifier… I have heard it, and really like it. It is more textured and nuanced than the original, its bass is more complete, harmonically structured, and treble has greater delicacy than the original.

The question is rather.... If you have a single source... The Pricasti M1 DAC, you might not need a preamplifier at all. These days, if you have a really good DAC with high quality variable analog output, a preamplifier justifies itself mostly for system management in a system with a combination of digital and analog sources.

On the other hand, upgrading the power amplifier or adding a line stage are not the only way with which your system can enhance its performance very significantly. Yes, there are speakers of course, and then there is cabling, which can make a world of difference.... What wires and PCs are you using today?

Guido

Guido,

My digital and balanced interconnect cables are Wireworld Platinum Series 7. My powercord and speaker cables are Wireworld Silver Series 7.

I've gone back and forth because I didn't think I would have the opportunity to compare everything. It looks like I may have the opportunity to compare my Bricasti M1 DAC/JR 525 combination to the Continuum S2 and Bridged 525s to the S2.

I know that upgrading the power amp, adding a line stage, and/or changing speakers can have a significant impact on the overall sound. I'm limited on what I want to spend; therefore I'm trying to figure out the best way to spend my money. I've ruled out changing my speakers or my DAC.

Guido, as always thanks so much for your input.

Hi Richard, seems to be an excellent plan to me. On the subject of line stage, adding a line stage between DAC and amplifier is not likely to increase resolution per se. On the other hand, it can do the following...

* if a hypothetical DAC were sounding a little hard fed direct into amps, linestage might be able to eliminate some of the treble intermodulation causing the hardness.

* In some cases, a linestage might add some authority, and macrodynamics to the analog output of the DAC.

* If a DAC signal could not be attenuated down to 0 with its volume control, a linestage would get you down to zero volume.

On the subject of cabling.... I am getting some startling results by applying a pair of High Fidelity CT-1 power cords to my system. I will be creating a thread in the next few days to describe my break-in findings. Stay tuned.

Saluti, Guido

Thanks for the advice and good conversation...decision has
been made to purchase another 525 and use them bridged. I
will provide some feedback within several weeks.

Good luck, I hope that you'll be very pleased with your decision!

Fabulous.... Do keep us posted Richard!

Guido

06-02-15: Ricred1
Onhwy61,
I have a clearly defined vision. I want better separation between instruments and better front to back placement of instruments.How to get there(what's my weakest link) and how much it's going to cost is the question? It may be time to investigate replacing my Aerial 7Ts!

06-12-15: Ricred1
Thanks for the advice and good conversation...decision has
been made to purchase another 525 and use them bridged. I
will provide some feedback within several weeks.

Ricred1, I've been following this thread & noting the exchange between you & the other members. Some members like Bill_k & Zd542 have tried to give you good advice but I suppose you were not listening. I'm not sure that adding a preamp would have solved your issue (of lack of instr sep & soundstage depth) but IMO its a heck of a lot better than a decision to use 2 525s in bridged mode.

Do you understand how bridged mode works?? I'm inclined to say "no" but I'm making an assumption (maybe a big one). I don't see any conversation here re. bridged mode & your decision seems sudden & I'm not sure what it is based on? In bridged mode, the 2 channels of the amplifier drive the speaker in a differential mode - one output of one amp drives the plus terminal of the speaker & the output of the 2nd amp drives the minus terminal of the speaker. So, the output current is doubled (since each amp is working independently to drive the same speaker). The doubling of current can also be viewed in another way - to the amp, the speaker impedance is halved. This is the key part - in bridged mode, the amp now sees a 4-ohm speaker that was nomimally 8-ohms. All of a sudden in bridged mode, the amp is outputting 2X the current. Can the 525 amp handle this in bridged mode?
If you read the specs, it says 950W at 8-Ohms. It does not specify what is the minimum load impedance that the speaker is allowed to go such that the amp remains in spec.

http://jeffrowlandgroup.com/us/amplifiers-model-525-stereo-amplifier.html

If you look at bridged mode specs from amp manuf, in general, you will notice that the speaker impedance is 2X for the output power in bridged mode. For example:
300W/ch, 8 ohms
600W/ch, 4 ohms
1200W/ch, 2 ohms
600W/ch, 8 ohms, bridge-tied load (or BTL) mode <----
in bridged mode, you don't get the 600W/ch at 4 ohms (that was specified in non-bridged mode); you get the 600W/ch at 8-ohms. That's because the output current capability has doubled in bridged mode.

What is the minimum speaker load for the 525 in bridged mode?
if you look at the Aerial 7T spec, it clearly says that the impedance dips to 3-ohms.
http://www.stereophile.com/content/aerial-acoustics-model-7t-loudspeaker-specifications

and you can see that here in the impedance + phase plots - Fig1
http://www.stereophile.com/content/aerial-acoustics-model-7t-loudspeaker-measurements

Make sure that the 525 can handle 3-ohms minimum in bridged mode without frying the output stage of the amp. Rowland has not spec'd it on his webpage; a call to Rowland is in order to confirm this.

Also, sonically, you are providing brute force to the Aerial 7T in bridged mode (assuming that it will work, as questioned above). I have never seen any amp or any system provide more nuances (instr sep, soundstage depth - the attributes you are looking for) when it is brute forced. In fact, search these archives, people have expressed their dismay at worsening of the sonics in bridged mode. In fact, those in the know, will never resort to running an amp in bridged mode unless it's for PA (public address)work when using, say, a Crown amp where SQ does not matter much at all.

Rowland gave you good advice. Note that they did not advise you to run the 525 in bridged mode. They knew & know that bridged mode is not a preferred mode for audiophile listening purposes.

Soundstage depth might not be the domain of class-D amplifiers as yet - I could be wrong here. They have acquired many other nice attributes as class-D has matured but soundstage depth might not be one of them. In my experience soundstage depth is a function of linearity & in this department the SET wins hands down. Single output tube doing push & pull, directly heated tube, there is no matching of push & pull transistors or tubes & you get the best front-back layering.
Solid-state does not do front-back layering as well as a SET & again in my experience, the class-A solid-states do a better job of front-back layering than any other solid-state topology.

I think you are going to be sorely disappointed at the outcome. My 2 cents for whatever they are worth. Thanks.

Bombaywalla,

I take all advice with a grain of salt. Ultimately my ears
and wallet determines what I purchase.

I called Jeff Rowland several times and talked to them
regarding bridging the 525 to drive Aerial 7Ts. Per my
conversation with them, the 525 wouldn't have any problems.
I will follow-up on Monday to confirm bridged 525s can
drive the Aerial 7ts. They recommended the 625 mk2 as the
best option, but as already stated the 625 is out of my
price range.

I respect your opinion, but to insult my intelligence by
assuming I don't understand how bridged amplifiers work is
a little too much...I'm capable of reading..JR clearly
shows how the 525s are connected when bridged. Furthermore,
your assumption is I haven't compared bridged 525s to a
single 525. To my ears bridged 525s have more bass impact,
an ease to the music, and yes a more open soundstage. No it
wasn't with my speakers, but I should have the opportunity
to listen to bridged 525s in my system.

I don't know your experience with Jeff Rowland Class D
amplifiers, but if the recording allows, the 525 presents a
very good soundstage and separation, but just like many on
Audiogon, I want to go to the next level.

Finally, I enjoy Audiogon and post questions to provide
food for thought. That being said, I submit anyone that
purchases components simply on the advice of others is a
fool.

Bombaywalla,

Yes you are correct, M525 would not be more inherently nuanced in bridged mode than in standard stereo mode. However, if in bridged mode each chassis is on a lower duty cycle for the Ariel speaker, it is quite possible that the end effect will be... One of enhanced nuance. I already know from eyewitness reports that M525 delivers markedly greater authority in bridged mode than in stereo mode.

From all reports I have heard, M525 do not degrade their performance in any way in bridged mode... That is why Rowland has decided to place an easy to flip selector switch in back of amp.

Rowland specs are extremely conservative and simply do not tell the whole story.... Yes, Rowland has applied M525 bridged to large lower impedance speakers with great results... Sorry I do not remember which ones.

This is not a tribunal... Richard need not justify his audiophilic cravings in front of us *grins!*

I for one am looking forward to hearing Richard's findings... I am following threads to learn more than anything else... Damm the specks... All steam ahead Richard! *Grins!*

FG.

Ricred1, Guidocorona, thanks for your respective posts & clarifications.
What happened in my post also happened earlier in Onhwy61's post when he asked what Ricred1's vision was. Just like me, Onhwy61 didn't think that Ricred1 had a vision for his improvements until Ricred1 came back in the next post & said so. It seems to me that Ricred1's not the greatest in communicating his thoughts & ideas & when he's out looking for advice like this, communication is everything. We don't know each other & we can only go by what info is posted. Like I wrote in my post there are no posts on bridging the M525s so I naturally assumed no one's discussed the pros & the cons....
Yeah, I agree its not a tribunal for sure. If Ricred1 is soliciting advice then lets discuss the topic in depth but that only happens when there's a better flow of information otherwise people end up making wrong assumptions.

Ricred1 I didn't insult your intelligence - I wrote that I assumed you didn't understand & further in parenthesis I also wrote that my assumption could be wrong.

Bombay walla, soliciting advice or options does not imply that the questioner has an obligation to heed such opinions, nor to explain his deviations from the above.

In the end, Richard's own findings in situ will add to the body of hard evidence-knowledge on this site one way or another.

G.

Earlier in this thread I never meant to suggest that Ricred1 didn't have a vision, but that I wished he'd actually state it as opposed to the original question about a preamp vs. separates.

I too am a little surprised by his choice of bridging the power amps, but I suspect he'll be quite happy, at least for a little while. All his stated goals can be better addressed by loudspeaker placement and acoustic treatment (sometimes adding, sometimes removing). I also wonder why saving up for the 625s is out of the question?

It's not a tribunal, but to think there are no judgments being made is naive. I would hope that on these forums we can honestly and directly share our thoughts.

I believe that the just announced Rowland M625 S2 may cost approx $18K. Makes for significant planning impliccations. G.

06-13-15: Guidocorona
Bombay walla, soliciting advice or options does not imply that the questioner has an obligation to heed such opinions, nor to explain his deviations from the above.

Sorry Guidocorona, I find this very weird then. If one is not going to take the advice given nor is going to share the deviations from the advice given then why bother asking a question on a forum & why bother wasting people's time soliciting their advice? One should just go off & do what one wants....
If one is engaging other people in a forum for one's own benefit then, yes, one does need to share owns own knowledge base pertinent to the subject at hand & let everybody (who is trying to help you) why one is going off on another track.

Bombaywalla... Sorry but I do not grock you... I must be senile. G.

Bombaywalla,

When I post a question, I'm looking for feedback from individuals that have firsthand knowledge of the components in question. Yes, anyone can have an opinion based on their experience; however if you not familiar with any of the components in question, why on earth would I take your advice? To my knowledge, Guido and Schacter are the only individuals that have direct experience with the JR 525 and/or the JR Continuum S2. It's only logical to take in consideration what they say. Take in consideration, not do it because they say so.

To say I don't take advice when posting/asking a question isn't true. I recently had a conversation with a guy on Audiogon concerning subwoofers. My thought was to pursue JL Audio only. This individuals owns a JL Audio F112, SVS SB13 Ultra, and a Rythmik subwoofer. Based on his advice I went and listen to a SVS SB13 Ultra. In addition, I tried to listen to a Rythmik subwoofer, but they were less than accommodating. I ended up purchasing a pair of SVS SB13 Ultras. He had direct knowledge, I took his advice to listen. I used my ears and wallet to make the decision on what's best for my system.

No, I don't post every little detail about what I've done. I have listen to many speakers since I've had the Aerial 7Ts. If I had the money I would own Raidho C3.1s, they are the best speakers I've ever heard. After listening to many speakers I decided to keep the Aerial 7ts...not because they are perfect, but the cost to replace them is way more than I'm willing to spend.

I do have room treatment and have moved the position of the speakers several times. Prior to inserting my subs, I removed my bass traps, but found it sounds better with them in now that I have subs.

I appreciate everyone taking their valuable time to respond to my questions. When there are disagreements I submit we should remain cordial...it's only audio.

"Take in consideration, not do it because they say so." ... My thinking's exactly Richard.... We can offer only data points... These may be applicable or not, or partially applicable, to your particular situation.

Hence my query: what made you opt for a second lovely M525 instead of going the Continuum S2 integrated route?

Congrats always! Guido

"Yes, anyone can have an opinion based on their experience; however if you not familiar with any of the components in question, why on earth would I take your advice? To my knowledge, Guido and Schacter are the only individuals that have direct experience with the JR 525 and/or the JR Continuum S2."

I get it, but you're not being consistent. In some of your other posts, you appear to have no problem discussing different components, as well.

06-02-15: Ricred1
Zd542,

Any suggestions on preamps I should listen to? I had a Parasound JC2 BP and to my ears it degraded the sound when compared to the PS Audio DSD I had at the time. The Bricasti M1 sounds much better direct than the DSD.

06-03-15: Ricred1
Onhwy61,
I'm looking into speakers now. A few on my list are Joseph Audio Perspectives and Dynaudio C2s.

Huh... Richard on trial... Again?! *Sighs!*

however if you not familiar with any of the components in question, why on earth would I take your advice?

Ricred1, you would want to heed my advice because my advice is based on engineering & is agnostic of equipment. My advices deals with physics & the limitations it creates on any electronics. No matter what the brand, it cannot defy physics. If you ignore those considerations I stated in my original post you could end up in a very bad situation with potentially a large out-of-pocket expense coming your way.
If the M525 is spec'd to handle your Aerial 7T - fine, you have nothing to worry about in terms of equipment compatibility. If the M525 is not spec'd to drive your Aerial 7T in BTL mode, a dangerous situation was detected for you well before any mishap.
When soliciting advice on any forum there are always 2 aspects to one's question - one, people who have direct experience with the equipment you are seeking yourself & two, the electrical compatibility of the equipment you are seeking with the rest of the equipment you already have. Both aspects are equally important. I addressed the 2nd aspect of your quest for better SQ. That's why you need to heed my advice OR anybody else's advice who addresses this aspect.

If you seek the advice of only those people with direct experience of the gear you are seeking but fail to see that this gear is incompatible with your gear, you will not have the same experience as they did. Do you know what the impedance of their speaker is? If yes, is that the same impedance as your speaker? If yes to both then only can you use their data point as-is; otherwise, you have to start from scratch as your speaker impedance is different i.e. just because it works in their system does not mean it will work in your system.

I appreciate everyone taking their valuable time to respond to my questions. When there are disagreements I submit we should remain cordial...it's only audio.

we mutually agree on this 100%. Thanks for stating it for the benefit of all of us.

I posted on 6/3/15 that I would explore a couple of speakers...10 days later I posted "After listening to many speakers I decided to keep the Aerial 7ts...not because they are perfect, but the cost to replace them is way more than I'm willing to spend."

Bombaywalla,

I assure you I know the impedance of my speakers. In fact I'm 100% sure I told that to the individual that I spoke with when I contacted Jeff Rowland. I didn't say at what frequency it dipped below 4 ohms, but I did explain it went below 4 ohms...they put me on hold, returned to the phone and told me it wouldn't be a problem. I talked to a dealer ad he told me it wouldn't be a problem. I promise you I'm listening and that's why I stated I would call Jeff Rowland on Monday and confirm that bridged 525s don't present a danger went driving Aerial 7Ts. If they tell me something different I will let you know.

Bombaywalla, your concerned about compatibility of 7Ts with M525 in bridged mode is addressed by the following fragment from Richard....

"I called Jeff Rowland several times and talked to them
regarding bridging the 525 to drive Aerial 7Ts. Per my
conversation with them, the 525 wouldn't have any problems.
I will follow-up on Monday to confirm bridged 525s can
drive the Aerial 7ts."

G.

Richard, I have no experience whatsoever with Rowland equipment, but I do have a suggestion I think may be worthwhile. When you get the new amp, in addition to trying the two 525's in bridged mode, try them in a vertical biamp configuration (which you can do with your speakers).

You would of course need an extra set of speaker cables and also probably a pair of XLR y-adapters (used at the amp inputs) to vertically biamp a pair of 525's, but for initial experimental purposes, at least, those things needn't cost much. And given the very low output impedance of the Bricasti M1, it won't have any problem driving two amplifier channels from a single one of its outputs.

Also, regarding Bombaywalla's most recent post above, I agree 100%. And the concern he expressed earlier about bridged mode perhaps being an issue when used with a 4 ohm speaker is certainly valid as a general word of caution. Not so much with respect to the amp's ability to function (at least in the case of a high quality amp that is presumably designed in a robust manner, such as a Rowland), but rather with respect to sonics.

In this case, as I have no experience with Rowland equipment I of course have no idea as to how applicable that caution may be to the specific amp in question. But I would cite several posts Atmasphere has made in the past in which he has asserted that ALL amps will sound better to some degree when driving higher impedances, such as 8 ohms, than when driving significantly lower impedances, such as 4 ohms. And (as Bombaywalla indicated) in bridged mode the amp will "see" the nominal impedance of your speakers as 2 ohms, and as not much more than 1.5 ohms at some bass frequencies which often require lots of energy.

Which is one reason for my suggestion of trying the amps in a vertical biamp configuration as well as in bridged mode. Another being that I wouldn't be at all surprised if vertical biamping were to provide a significant improvement in imaging relative to what you have now, that you are specifically looking for, without the possible sonic downsides of bridging. The possibility of improved imaging presumably resulting, at least in part, from elimination of the inter-channel crosstalk that inevitably occurs to some degree in a stereo amp, via grounds, power supplies, and other paths. In a vertical biamp configuration that is eliminated since the same signal is going through both amplifier channels.

Good luck. Regards,
-- Al