Jeff Rowland

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.

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.

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.

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.

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.

Ricred1

cool, Ricred1.
One suggestion - when you talk to Rowland the next time do request some specs of the M525 in BTL mode. All of us can see just one spec - 950W into 8 Ohms. The question is what is the minimum load impedance it can drive? The Aerial 7T will go down to 3 ohms at certain freq which will look like 1.5 Ohms to the bridged M525 (as Almarg also stated in his post). Ask Rowland if driving 1.5 Ohms in bridged mode will be an issue.
Keep us posted. Thanks.

06-14-15: Guidocorona
Richard, if you ask the question above to Jeff, please explain that 7Ts speakers go down to a relatively reasonable 3 Ohms under normal conditions.... 1.5 Ohms may occur only in theory with a bridged amp... You do not want to lead Jeff to believe that your speakers dip normally to 1.5 Oh... Meaning a ghastly 0.75 Ohm from a bridged amp.

G.
Guidocorona (Threads | Answers | This Thread)

06-14-15: Bill_k
Guido is absolutely correct, he beat me to it in pointing that out.

Guidocorona, Bill_k,
my post made is very clear that the Aerial 7Ts were a min of 3 Ohms nomimal & 1.5 Ohms in bridged mode. This was very clearly written, no?
I'm cutting & pasting that part of my post again for your resp. convenience....

The Aerial 7T will go down to 3 ohms at certain freq which will look like 1.5 Ohms to the bridged M525 (as Almarg also stated in his post). Ask Rowland if driving 1.5 Ohms in bridged mode will be an issue.

Ricred1,
great! thanks for the update. looks like you are good to go w/ the M525. You now know that you won't have a melted output stage with the Aerial 7T's 1.5 ohms in bridged mode.

Still......I would give heed to Almarg's suggestion (which was also on my mind but Almarg beat me to it) of using 1 stereo M525 for each speaker in a vertical biamped format. The amp will not see 3 Ohms (because it will be running in plain old stereo mode) & you will have 1 dedicated amp for driving the bass for each channel.
Since you will have 2 M525s you can try the bridged mode & the vertical biamped mode. Yeah, you will need 4 interconnects pre-power & 4 speaker cables to try the vertical biamped mode.
Let us know how you fare. Thanks.

If I don't think the Continuum is a big enough difference, I will sell my 525 and look for a used/demo 625 mk1....

+1 Almarg, Zd542.
Ricred1, before you sell off your M525 in the event the Continuum integrated is not a major step-up in SQ, do try using your 2 M525s in a vertical biamp config. It might just surprise you SQ-wise - amps driving a higher impedance are generally less stressed & sound better, no matter what the manuf says. (There are a few expensive amps that buck this general trend but these are exceptions).
If it doesn't, so be it, you tried/explored every configuration with all the Rowland gear you had on-hand & it did not work out so you decided to go for the M625 Mk1.
Like Zd542 wrote - you have both M525s & all the cabling (if I understood Almarg's post correctly), it behooves you to try the vertical biamp config. thanks.