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Bass distortion-Playing LP's only,,,,please help

VPI Prime----Ortofon Black Quintet (low output moving coil cart)-----Plinius Koru Phono Pre( loading at 20 ohms/gain at 66 db)-----Parasound Halo Integrated -----Martin Logan Montis speakers which have powered bass cabinets.

Using any other source component I have absolutely no issues. When I play an LP and increase the volume past 10 O'clock which is a little loud....but not ridiculously loud-I at times get this huge wave of bass distortion. I do have bass controls on the Montis's...and I have turned them down into the negative, but I still get what I previously described occasionally. 

Any and all help would be appreciated. This doesn't always happen, but its frequent enough to drive me crazy.

Thanks in advance.

krelldog

Showing 12 responses by moonglum

moonglum
619 posts
 
Good advice above Krelldog but one other thing worth trying : the Montis active bass will (I presume) have a bass roll off control. I've always felt with MLs bass output that "less is more". Try introducing a few dbs cut (say -4 setting on each or whatever you feel is appropriate) and see if it solves the problem and whether you can live with it?
All the best
moonglum
619 posts
 
(Sorry Raul ;)
moonglum
619 posts
 

Krelldog, take heart my friend. By way of encouragement :

  • I use a T/T of almost identical mass/config.

  • It is situated in the worst possible place – a corner.

  • There is an ML active bass cabinet right next to the T/T (Vantage)

  • The stand simply consists of 3x tri-spiked levels, 50mm thick solid oak throughout, set on a solid concrete floor.

Even at peak SPLs of 95db (measured) at 6 metres there is no trace of feedback. (Not that I routinely listen at such volumes, I prefer to retain my hearing! ;)

Bass integration is perfect and the sound completely natural.

Good luck! :)

moonglum
619 posts
 

Czarivey said :-

"It's not acoustic feedback to worry about it's EM resonance between cartridge and speakers"


This is nothing more than scaremongering. You'll find most audiophiles, including myself, will have learned to place sensitive gear e.g. CRTs and magnetic cartridges, at least 2ft from unshielded loudspeaker magnets.

MLs are magnetically shielded.

If you have both min clearance and shielding, case closed.

moonglum
619 posts
 

Those panels generate an electrostatic field not a magnetic one. To generate powerful magnetic fields requires high current (magnetic flux is proportional to current).

The aforementioned field is also constrained within the stators.

Magneplanars would be a different story... ;)

Anything else?

moonglum
619 posts
 

Czarivey, it works wonderfully well, thank you for asking. ;^)

 

On the other hand it’s not entirely clear what is being asked as the question is somewhat nebulous?

The first argument was EMI based but now the goalposts have moved?

Are you asking about possible stray capacitance?

A possible potential gradient between an electrostatic loudspeaker stator and nearby objects?

Or, entering Dr Strange territory, “a quantum field relationship” between the elements of a hifi system? ;^)

moonglum
619 posts
 

OP, personally, I would tend to explore the rumble filter option last rather than first.

Have you tried messing with the sub-woofer bass contour controls? Mine are 4.5ft from the front wall but I still need a sizeable bass cut to avoid overwhelming the room. :)

The added benefit is that it stops the spikes and panel bolts from vibrating loose! ;^) :D


I think it’s a given that you probably visit the MLC website but if you do there will be plenty of good advice there as well.

Good luck!

moonglum
619 posts
 
Mains,
Townsend's research looks pretty convincing. £1400 asking price does take the breath away :O
While I was browsing the Townsend I happened to notice someone with a pair of Montis was actually using Podiums to solve the OPs problem!
It looks somewhat floppy. I'm not sure I'd risk tall speakers on it.
Nevertheless they claim good results which seem to be backed up.
moonglum
619 posts
 
My apologies Krelldog. I didn't realise that you'd already tried negative values. Doh!

Memo to self: please read the entire post before commenting ;^)
moonglum
619 posts
 
Dear Krelldog,
Glad to hear things are working out.
I've had to correct my posts because I got the multiplier wrong :)

Use the x10 Rule to decide the cartridge loading rather than sticking with Ortofon's minimum figure of 20 ohms.
Since the manufacturers internal impedance is 5 ohms this would make your "realistic" minimum 50 ohms. I personally prefer x20  which gives 100 ohms, but many would suggest even higher values. It's a subjective decision based on your own taste and your phono stage. 
The important thing is to try it if you haven't tried it already.
Cheers,
Bill

moonglum
619 posts
 
The Koru is a great phono stage. I've heard lots of good things about its sound quality. If the nearest preset load setting was 120 ohms I would cheerfully go for that but it's likely that 100 will be available.

Interestingly, after I posted I read a review by MF of the quintet and he tells that although they started at 50 they eventually opted for 100 ohms so it looks like, on this occasion, my x20 guess worked better than the usual choices ;)
Can't guarantee that'll work every time but since most go for even higher values I'm very much in a minority anyway! :)
(I'm currently using 220 ohms which for me gives a nice balance on the Delos)


moonglum
619 posts
 

Dear Ralph,

"...is probably adversely affecting its compliance..."

I remember hearing about that theory at the time and thinking it sounded "ropey". I have great respect for JC but how resistive loading could influence compliance (physical/mechanical) in a significant/audible way left me feeling slightly sceptical.

Has any more been published about this?
Cheers,

Bill.

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