Dark Side Of The Moon,and bass

I'd get this first. Its a lot cheaper than a new arm!

http://www.netsoundsmusic.com/nsdsii/1/72323275/1/shure/1/1/9999.html

 

It's possible that a combination of factors is causing your problem, and that the preamp exacerbates matters by not rolling off the subsonics. This isn't 'rumble filter' it's simply what record reproduction requires.

There's no way to say exactly what your problem is, whether it's the deck's position, mounting, or the cartridge/arm compatibility, or all three, but it is a problem.

Paul

 

some are saying its not a problem,its normal,so which is right?

I can change the arm easily enough,and get a cart that is recognisably compatible,but not if its just normal in a Planar 3

 

Cones flapping isn't normal, it's a symptom of substantial subsonic output that is definitely not signal from the record. Call it 'distortion'...

It will be exaggerated by some types of loudspeaker, but is wasting amp power and limiting the output of real signal.

Unless your cartridge is a high compliance model (something like a Shure V15, the older ones anyway) then I'd suspect the mounting or positioning of the turntable first.

Paul

 

Saab,

There is a formula for calculating the resonant frequency of a particular arm & cart. combination. The formula and other information can be found at The Analogue Department. Once you know the parameters of arm and cart. you ought to be able to determine suitable combinations.

AFAIK you wont be able to eliminate this resonance, simply move it out of the audio band. As such, if the cone flap is causing you concern there are three options that I'm aware of:

1 - put a filter in line to cut frequeniies below xHz
2 - put your 'speaker grills back on - out of sight out of mind
3 - get a nice air of sealed box 'speakers - this greatly reduces the flap as the air in the box damps/controlls wanton cone excursion

This ought not be a concern if a) the resonate frequency is outside the audio band and b) the flap does not drive the cone/s to maximum excursion.

Regards,

Stuart.

 

With apologies to TonyL over at PFM, he has a graph which makes this easier to work out:



Add together the arm mass, cartridge mass and the mass of the cartridge bolts together and then read off against the cartridge compliance. This will give you the value for your arm/cart resonance. If its in the blue area, you're okay, if not you may have problems. Of course a test record is easier if you have one that'll show you your arm resonance.

That said assuming this P3 has an RB300, the arm has (according the OL site) a mass of 11g - assume a cart and bolt weight of 6g and we have a mass of 17g. In order to be in the arm/cart resonance danger zone, whatever cart Saab is using would have to have a compliance either below 7cu (which is very very low and unlikely or above 25cu (which is very high). Which makes sense as the rega is a medium mass arm which should cover most bases except the most extreme. I don't know what cart Saab has, but its unlikely to be outside these limits but I guess a test record will tell all.

Graham, I stand corrected re the rumble - presumably then, I've just been pretty lucky re arm/cart compliance and positioning of all my previous deck/arm/cart combos.

Also if just tapping the stand causes some cone flap, doesn't that really start pointing the finger at how the deck is situated? If dinging the rack is putting out enough low frequency energy to flap the cones could low frequency energy from the listening environment ie. the speakers be the culprit? Could a combination of a rack which either because of how its constructed and/or where it is in the room seems to "sing", be the cause? Some sort of feedback loop and resonance in the rack say?

 

That was a really informative and useful post.

However, I think it's unlikely that the speakers could be the culprit in a feedback loop as I don't think that there would be sufficient energy in the cone flapping. Also, I suspect that the nature of such a loop, if it existed, would be to start off small and then build up until the cones flew out of the drive units and frisbied across the room.

I think that (temporarily) Saab should place an inner tube (or similar) between the turntable and the stand. A pillow would probably do if there's no inner tube. Tapping the TT body should then reveal whether the cone still flaps as it does when the stand is tapped now. (Tapping the stand would indicate how good the isolation was.)

If the cone still flapped this would point to a TT/arm/cartridge resonance.

Wouldn't it?

 

What if the record's not pressed 100% central, so that the arm "wiggles" side to side as it plays? That could cause very low frequency rumble, could it
not?

On to the LP12 - why would a newbie want a deck with bass that's stodgier than a primeval swamp? Let's face it - you have to seemingly spend a LOT of money on an LP12 to get accurate, non-coloured bass. Those who claim different are either deaf, deluded, or trying to comfort themselves at buying an outdated turntable for waaaay too much money... (sorry - I just don't "get" the LP12 - maybe there should be a thread on here about IYHO overrated hifi????

BTW - I think vinyl "does" note decay better than CD as the lower-level resolution is better; CD has loads of distortion and innacuracies as you go lower in volume from 100% output, and it seems to me that you have to spend a lot on a CDP that can resolve this lower level detail cleanly. Certainly, as I've moved from cheapo CDPs upwards, note decays get more natural and believable.

 

7_V, it can be feedback related without being completely uncontrolled.

Dom, you can bang on about your ignorance of the LP12 all you like but you aren't going to get my cones flapping. And calculate what frequency an off centred record would generate with a badly setup arm/cart...

Paul

 

I 've just put DSOTM on my Rega/dynavector and watched the cones,and noticed no cone flap,just a slight moving backwards and forwards,the same with other LPs just a slight movement,I then tapped with my finge onr the Plinth of the Rega,the cone then started flapping.

 

I have never experienced this problem so it would seem to indicate a problem with the decks set up.

I listen to Ed Rush and Optical, all on vinyl, if that dosn't produce bass then no music does, and no flap. The cones are working hard, and I think the difference appears to be that on vinyl the cones can work a lot harder before your ears bleed blood.

To get the cones working as hard on CD seems to have a detrimental effect on the treble, a problem simply not apparent on Vinyl and why I much prefer vinyl (IMO of course)

And the bass is better on vinyl.

 

What happens when you all play A Higher Place from Royksopp's Melody A.M. on CD?

 

<takes speaker grilles off and has a listen>

To start with, nothing out of the ordinary....but around the 3 minute mark - major cone flap

Also checked out the end of Chemical Brother's Hey Boy, Hey Girl on Surrender and when it does those twidly sounds at the end I also get serious cone movement but not as much as on the Royksopp track.

In both cases it appears to be at sub-sonic frequencies. I guess it might happen more often in my system but since I always use the grilles I wouldn't notice.

Michael.

 

will try the pillow test ta

but tbh I really can't fathom the graph thing,I was hoping for an easy answer,but several others have this problem so it seems it might just be a bi-product of particular carts and an RB300 (ie Adam gets the same flap when he taps his deck).

watching the cones again it seems to me to be definate flap,rather than just working hard,they wobble quite noticably

The cart is an Ortofon 530MrkII.

I am getting new speakers next week and will see what happens on a new rack,in a new house and a new cart.

thanks for all the replies

any recomendations for a cart on the Planar 3? around £100

 

See if you can get an Ortofon MC3, they really sing on a P3, should be possible for about £100 if you get lucky. There's a guy on ebay sometimes has them

 

ta

MY name is Dave,I suffer from Cone Flap

 

Hi Dave (Saab),

from the graph, the reasonance is about 8Hz. The compliance for your cartridge is 25. This is on the limit of the safe band.

I would try looking at the placement of the turntable. Get it out of the line of fire from the speakers. Also look at what it is sat on & where this is with respect to the speakers.

Turntables will produce a noise through the speaker if the plinth is tapped. The plinth is picking up energy from the speaker and through the floor. This energy is transfered to the arm & cartridge. It will go down through the amp to the speakers. If this energy is great, you may hear the effect through the speakers. Also you will see the bass cones go crazy if it gets really bad. I.E. unstable.

The output is adding to the input and creating a loop which gets bigger & bigger till it gets unstable. If it is mild then you may get the bass flap.

SCIDB

 

Must be, really, if you can clearly see the flapping (moving backwards and forwards 20 times a second is pretty damn fast when you're watching it).

 

mine are big and slow flaps

 

Flaps per second??

Seriously as SCIDB points out, the Ortofon 530 II is a very high compliance cartridge and you are on the edge, and maybe actually in the arm/cart resonance danger zone. If your tt isolation is less than ideal as well then I guess we're close to the answer.

To work the graph you need to know your arm mass with cart (we've estimated 17g) and the compliance of your cart (25cu), you find the 17g point on the bottom axis of the graph and draw an imaginary vertical line from this point. You then find the 25cu point on the vertical axis of the graph and draw an imaginary horizontal line from this point. Where these two imaginary lines cross gives the the resonant frequency of your arm/cart combo by reading off this point against the diagonal lines - in this case about 8Hz - just on the edge of safe zone.

I can only speak from a theoretical point of view as its something I've never experienced. For a long time I ran my old Michell with an RB250/Ortofon 530 II - which is pretty close to your setup. That deck was set on a very hefty and heavy piece of furniture (Wood and metal) and a home made isolation platform (MDF with sorbothane feet) ... it was a lot closer to the speakers than ideal mind and a suspended floor too - I never had cone flap though.