Montis + NAD = bliss with issues

[torifan60]

I am the proud new owner of a pair of Montis. Paired with a NAD C390DD, the sound is superb. I do have 2 issues though: The NAD will shut down with a "channel protection" fault when playing high frequency or busy pop music at moderate volumes (as low as -23db in certain passages). Did not have this trouble with my Polk cabinet speakers. 2nd issue: the frequency response at the listening position shows a +10db bump from about 5000Hz to 7500Hz peaking at 6000Hz. Then a sharp drop off at 13K to -10db and downhill from there.

I'm wondering if different cables would help, per the Sanders white paper that has been often discussed on this and other forums http://www.sanderssoundsystems.com/technical-white-papers/54-cables-white-paper. He claims that the right cables (his) can fix both the problem with low speaker impedance at high frequencies, and move the high frequency bump out to the inaudible range. Any opinions on this, or any other ideas to address these issues? I currently am using a pair of 10 foot blue jeans cable (Belden 5000) that have very low capacitance but also very low resistance. I've talked to NAD support about the protection fault - they had me put a 180 ohm resistor across the speaker terminals Didn't work - made it worse.

 

[JonFo]

Sorry to hear about your issues. Sounds like that NAD lacks the 'nads to power the ESL's (sorry couldn't resist the pun )

All ESL's have a very complex impedance curve as well as strong back EMF, and you need an amp capable of driving low impedance and high capacitance. A good measure of an amp that can do that is one that doubles it's output for every halving of impedance (e.g. 100w @ 8ohms / 200w @4 ohms) and can deliver high voltages into the speaker.

So an amp like the Sanders Sound Systems ESL is the ideal amp (delivering up to 2000 volt-amps).

Cables will not help at all in this case.

But many other vendors produce products that meet that spec. Check out Coda and look up other amp recommendations here, But please be sure they are models designed to double down on power. Amps that don't just don't sound that great on ESL.

 

[Gordon Gray]

So an amp like the Sanders Sound Systems ESL is the ideal amp (delivering up to 2000 volt-amps).

JonFo,

There are many quality amps that can drive the Montis.

With all due respect, seems like you've become a salesperson for Roger.

GG

 

[edwinr]

I'm sorry to hear your issues torifan60. I posted similar problems with NAD amplifiers a year or so ago. I tried various NAD high end receivers and despite their claimed ability to drive demanding speakers, they all shut down on me when driving Martin Logan electrostatics. I thought NAD might have fixed these issues - but obviously not.

Look torifan60, check out Peachtree Audio. I've heard Peachtree have demo'd their amplifiers with Montis speakers!

 

[torifan60]

Thanks Jonathan and Edwin. Here are the specs for the NAD.
Continuous output power (ref. 20Hz – 20kHz, rated THD) - 8 ohms ≥150W
Continuous output power (ref. 20Hz – 20kHz, rated THD) - 4 ohms ≥150W
Rated distortion (THD, with AES17 and AP passive 20kHz LP filters) <0.005% (ref. 20Hz – 20kHz, 500mW – rated power)
Clipping power >165W (ref. 1kHz 8 ohms 0.1% THD)
IHF Dynamic power - 8 ohms ≥160W
IHF Dynamic power - 4 ohms ≥350W
IHF Dynamic power - 2 ohms ≥350W

The dynamic power specs indicate that it increases with dropping impedance, but the continuous power specs don't increase at all.

I'm not ready to dump it yet - it has many strong points and provides so much value.

Any thoughts on my 6000Hz bump in the frequency response?

-David

 

[RUR]

Any thoughts on my 6000Hz bump in the frequency response?

David, do you have another amp you can insert and take a similar frequency response measurement? This would show us whether or not the amp is causing this bump. Also, what software are you using to take the FR measurements?

At one point, I purchased a TacT S2150 "power DAC", employing the same amplification principles as your NAD DD. It sounded terrific, but failed pretty quickly (multiple times) and I ultimately concluded that the reactive load of my Summits and the TacT were never going to play nice. It's impossible to say that your NAD is having the same problem, but it's an interesting data point, IMO. Also (apparently) like the NAD, lab measurements for the TacT showed FR dropping like a rock >~15kHz into low impedence loads.

Ken

 

[torifan60]

Ken, I do have another amp but it will be a few days before I can swap them out and take measurements. I may also see if the bump and dropoff occur in different parts of the room, or if speaker placement affects it.

I used the poor man's method: Radio Shack meter and sine wave test tones streamed through a Squeezebox Touch.

 

[Northy]

You should exercise caution as not to damage the Montis. It is obvious that the NAD is struggling with the current requirement. I am assuming you have dropped over $10K for these sperkaers but you are trying to mate them with an amp which was not clearly designed for this task. You should look into the used market for beefy amps with massive power supplies if you want to get the best performance out of the Montis.

 

[Jemplayer]

Highs rolled off as the amp cannot drive the HF due to the low impedance in the upper frequency range. Also amp shuts down as load is too much for it. Simple. You need an amp as mentioned that doubles down into 4ohm and then again into 2ohm. Even my linn klout did that and it doubled into 4ohm (no rating into 2 ohm), shut down at high ish volumes...but was only rated 80/160 respectively. Although, was plenty for most medium floors standers.

My feeling is that you need to audition other amps that are rated down to 2 ohm and follow the effective doubling down as mentioned. I had same issue, went though various amps including the Tact 2150 which I didn't like at all and other d class such as rotel and wired 4 sound' and many other class a and ab.

The amp I ended up with plays well under an 2 ohm and doubles down as it does so. It is robust And powerful. The sanders white paper really says it all. However, I only read it after my journey down amp lane..was very reassuring to see what I found right there in black and white.

If your set on your nad, then you will continue to have this issue, and nothing you do will change that, even magical cables wrapped in silk and fairy dust..;-) it a power low ohm issue plain and simple.

 

[twich54]

I believe Jonathan nailed it………. your NAD is a 'lightweight', Class D switching amps rarely do well with complex loads IMO. Jonathan's example of the Sanders amp clearly indicates what a robust amp can do with a complex capacitive load that our Logans present.

There are many quality amps from which to choose, search and ask questions …………..

 

[torifan60]

Thanks everyone. I just got an email reply from Roger Sanders with a detailed technical explanation of my system and inherent problems. I think everything you guys have said is aligned with what he said.

So I need a powerful amp that doubles down as the impedance drops. Since the NAD is an integrated and where it really shines is in the pre-amp section, what do you think of keeping it as a pre-amp and feeding the pre-outs to a power amp? Since my budget is already blown, I'm considering a pro amp from Crown, Behringer, and the like. There was a long discussion on pro vs. home amps for powering panel speakers on another board and with ABX testing, the testers could not distinguish. Fan noise is the big problem with many of the pro amps.

 

[twich54]

with your budget 'blown'………how much are you realistically planning on spending on a amp ?

 

[torifan60]

I think as long as I stay under $1000 I'll also stay under the radar with my wife...

 

[MrBT]

I think as long as I stay under $1000 I'll also stay under the radar with my wife...

Please, treat you Montis ($10k) speakers with respect they deserve......

 

[Jemplayer]

I think as long as I stay under $1000 I'll also stay under the radar with my wife...

Pro audio is out. There is plenty of used gear you can buy , don't have to spend 10k on a decent amp. Mine. Was 3.5k US dollars, and it is brilliant. Go to audiogon or the like, and buy an amp based on what you have learned here and via sanders.

My advice, sell the nad, and buy another integrated, check out the Chinese stuff, I use it and it is good, so don't go brand mad. I listened to some very serious heavy hitters via my summits like mark Levinson,Plinius,Conrad johnson,classe etc. don't feel I am missing anything with my current amp. In fact dare I say, to me it's better?!?! No, how can that be.

 

[Bevensee]

I would advise you to look into Vincent hybrid tube/transistor power amps. I use a set of SP-T100 to drive my Vantage with great success. They have never shut down, not even after several hours of loud music, and they don't roll off the high treble when driving the stats.

They may be a bit above your budget, but perhaps you can find a pre-loved pair, or try with some of their smaller amps. Vincent amps are very hard to beat for the money, and they are stable into any load I have been able to test them with.

 

[twich54]

I think as long as I stay under $1000 I'll also stay under the radar with my wife...

if your confident with used (AudioGon) there lies your option, if not …….. start saving your pennies !!

 

[edwinr]

Buying a used power amp sounds like the best option for you at the moment. The Montis is one of the very best loudspeakers you can buy - disregard the price Martin Logan asks for a pair because the asking price doesn't bear any relation to how good they sound. So you need to bite the bullet and ditch the NAD and get a decent amplifier. I went through months of heartache dealing with NAD support and at the end of the day, they had no answers for me.

 

[Northy]

Try to be extra nice to your lady and she may let you get away with $1500-2000. Now, you can buy a nice Bryston, Classe, or Adcom on the used market.

 

[torifan60]

Twich54:

if your confident with used (AudioGon) there lies your option, if not …….. start saving your pennies !!

Well, guess where I bought my Montis?