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
I just finished blasting a couple of cuts from  a couple of bass heavy records on my VPIClassic /ART9 at a level I NEVER use-2-3:00 o'clock. Just comparing what I heard during a demo of the exact model amp  at a dealers.

Cant imagine what the cause of your problem is. Be interesting to read what you find. I HATE having those isolated,quirky bugs!


Sounds to me like you might be getting acoustic feedback/acoustic breakthrough/intermodulation distortion/rumble through the speakers.

This happens if the system is turned up too loud and the speakers are causing the arm/cart to excite. A rumble filter would solve this.

I’m assuming you checked all the alignment parameters of the turntable/arm/cart?
I am willing to bet you are getting some feedback. Can you remove the grill and observe if the woofer is oscillating abnormally? If it is, its a feedback problem. I had this problem with my Scout and now my Prime. My turntable is on top of a rack on a solid 3 inch thick maple air dried platform which is sitting on a sandwich material I bought from Mapleshade. I still got it. I bought a KAB Rumble filter for 180.00 and put it through the tape loop. Now the problem is solved and I haven’t lost any bass quality. You should hear how subteranian it goes during some songs on Amused To Death.  I could rattle the fillings out of someone's teeth!
Wow.... I have never heard of a rumble filter....but it sounds spot on to my issue. My bass cabinets aren't accessible,so I can't confirm the rumble. However for 180 bucks its worth a try.... thanks guys.
Krelldog, Better to move either your turntable or probably just one of your woofers (if they are separately housed).  Though the rumble filter will probably do the job, it's another item in the signal path that probably you could get along without.  Filters are not entirely transparent.
@krelldog...these were/are known also as subsonic filters.  I'm sure you've owned at least one preamp or phono stage that had one.  They used to be pretty prominent on preamps, but not so much now.
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
(Sorry Raul ;)

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! :)

move tt away from speakers.
Best case scenario is that you will solve your problem before adding a subsonic filter, I personally haven't needed them in my systems since moving up from an AR EB101 to a VPI Scoutmaster then a Prime. If you decide that you need the filter search for the Nakamichi SF-10 or SF18 which are 10Hz and 18Hz filters with a 6 db roll off they were my go to filters when needed and they do fix the problem. I sold mine with the AR or I would give you mine. Good luck
The KAB rumble filter uses audiophile grade parts and I can't hear any difference with it in or out other than the bass not distorting and the woofers not going into oscillation..  The quantity and quality of bass remains the same.  You can order one from KAB and have it within a week.  I run mine through the processor loop on my preamp, but a tape loop will do the same thing.  Also I moved my Scout and Prime all over the living room, trying different platforms, even one bolted to the wall but in the end, the rumble filter was the only thing to eliminate.  I have an old house with squeaky floors so perhaps that had something to do with it.
Another option!
http://store.acousticsounds.com/d/60042/DB_Systems-DB_Systems_Subsonic_Filter-Turntable_Accessories
If you decide on using the filters and you have no issues with other sources then plug directly into phono stage and then plug table into them.

+1 yogiboy

Looks like it will do essentially the same thing for a lot less money.  You have nothing to lose by trying these.

Scroll up and re-read lewm's post on 7-17.
Also check to be sure that your head shell is secure
Agree with most folks here - very likely acoustic feedback.  First choice of potential fix - move the tt further from the speakers.  If the speakers and tt both sit on the same suspended frame wood floor, this can be a bitch to eliminate.  If you can get them on two different flooring structures, you're way ahead in the game.  I know that's a big "if", but it's the best way to go whenever feasible.
Anvil turntable footers completely solved my acoustic feedback issues.  I agree with trying to move place your table farther from the powered woofers if possible. You never know how much better it might sound.
it's not acoustic feedback to worry about it's EM resonance between cartridge and speakers

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 , Didn't I mentioned Electro-magnetic resonanse?

Do you have any idea how heavy the ELECTRIC field of panel speakers? They can cause not only rumble but even ED when you hang around too close!

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?

So are these electrostatic panels shielded or not?
How does 4kv static charge sounds to ya and how it's compared to the delicate LOMC output? 

I ordered the KAB Rumble filter.....I'll let you know what the results are. I can't move my turntable due to my setup. I did move the M/L Montis's out into the room more.....The amazing thing is: It doesn't happen all the time. The sound in my new setup is spectacular. I just want to cure the rumble issue.

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? ;^)

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!

I can also add my praise for the KAB Rumble filter.  I had a horrible time with my McIntosh turntable thumping on certain LP's.   The KAB Rumble filter totally eliminated the problem and made all of my LP's sound better.
Where is turntable placed?
When placed in corner I had rumble.
Mid wall no rumble.
Bass builds up in corners.
hi 
your answer is a pair of Townshend Audio Seismic Podiums please check out for sale on audiogon the seller can provide any size to order at discount prices. All you need is your speakers footprint and weight for the correct size and load cells you will be gobsmacked i will add some links to reviews over here in the UK they are definitely the answer unless your equipment is faulty.
Check out Townshend Audio Website for reviews, i use the big Sound lab Dynastats i could never get the bass right until i put them on the Seismic Podiums the results are jaw dropping , you can buy from audiogon for sale pages good luck you will not have any further bass problems and you will hear your speakers like never before.
I agree with Mofimadness and a few others that you may be dealing with "acoustical  feedback".  I had the same issue in a console. My turntable was producing a lot of hum when using my turntable and turning the volume anywhere past 11:00. I ended up getting an amazing isolation platform from  Symposium called the ISO Segue! It solved the problem immediately- quiet as a mouse!
Even though my turntable was on a wall bracketed shelf, I still got air-bourne feedback. The woofers, especially my subwoofers, would be oscillating, and I also saw my tonearm bouncing up and down -- not out of the groove, but it was pretty peculiar to watch.

I used a KAB rumble filter, added more methods of isolation under the turntable, even between the wall bracket and the wall itself. The only other thing that comes to mind is isolating your turntable in another room, but then you would have to get up everytime to tend to it.

Best to you in your rumble and feedback endeavors -- hope you can solve your problem.
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.
I would look at my tonearm alignment.  If the VTA is off, you'll get overwhelming bass.  Assuming you have a VPI unipoint arm, they are very good, but very difficult to set up.  Look at the arm as you track a record and see how it looks.  Make sure the azimuth is set correctly, the stylus is 90 degrees in the groove (cartridge isn't 'listing' to one side).  Look at the base of the tonearm and make sure that is balanced perfectly and not listing as well.   It should appear as its floating, not dragging.
It has been a while since I had to deal with issues like you describe but, as one other poster suggests, this sounds like it could be a feed back issue of some sort since you may be unknowingly producing frequencies with this recording that are somewhat distinct from other recordings. I would also try changing slightly the direction of one or more or your speakers as a way of seeking to diagnose and fix the problem.
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 ;^)
How compatible is that Ortifon cartridge with the VPI arm?  Is it possible that this is just an arm mass - cartridge compliance mismatch that accentuates rumble on certain albums, and that it becomes more evident at higher volumes?  Have you tried a cartridge with a lower compliance on your arm?
The KAB rumble filter did not solve the issue. In fact my system did not like the addition. I am solving the issue by adjusting the bass controls on the Martin Logan Montis's,,,,,and moving the Montis's farther out into the room away from the turntable. I did try these adjustments before I bought the rumble filter.....but for some reason I'm having better results now. I'm still considering a isolation platform for my VPI Prime also.....thanks for all the suggestions.
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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

I would advise against the use of filters.  Yes cartridge loading can be a real issue and 20 ohm loading should be increased to 100 ohms and see (or rather hear) any difference.
Secondly, most good preamps will pass DC which will of course create havoc with your woofers.  Some woofer motion with normal vinyl playback will be present on a fair amount of material. 
So as presented earlier, TT isolation is paramount + proper cartridge loading.
Best of luck,
I get the cartridge loading, I have a lot of choices with my Plinius Koru.

Without sounding stupid...and I've never proclaimed myself an audio expert....

What exactly is Turntable isolation???  The first thing that comes to mind is a 2-3 inch platform underneath the turntable. I'm all in on this. I've certainly made the investment in LP playback. What else am I missing in terms of isolating my turntable???

As always I truly appreciate the help and guidance of other audiophiles that know a helluva lot more about this stuff than I do.
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)


Secondly, most good preamps will pass DC which will of course create havoc with your woofers.
This statement is entirely false. No preamp made passes DC!

Regarding loading:

If loading is affecting the sound, it suggests that the phono section is unstable with RFI at its input. Once corrected you will find that the loading no longer is needed.

The loading is used to detune a high frequency resonance caused be the inductance of the cartridge and the capacitance of the tone arm cable (inductance and capacitance are the building blocks of Radio Frequency circuits). This resonance is usually well above the audio band and can occur at several MHz.

Many circuits don't sound right in the presence of RF energy so eliminating it or the sensitivity to it (which yields greater benefit) is quite audible.

I discussed this issue with Jonathan Carr of Lyra fame a couple of years ago at Munich. We both had come to the realization that low impedance loading of a cartridge is probably adversely affecting its compliance, and so it likely reducing its performance in some tone arms. The idea is damping, not unlike how an amplifier can damp a loudspeaker.

So if you chose a cartridge to work in an arm based on its compliance (and resulting mechanical resonance), loading the cartridge may throw things off a bit.

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.