Phono - Speaker issue

[BuzzzFuzzz]

G'day folks.

 

I've recently bought a new TT - Music Hall MMF 2.2 - Running through a vintage Sharp 'Optonica' SM-5100H Japanese amp (50/60Hz - 350W) into vintage Technics SB2755 Australian made speakers (8 Ohm - 200W).

 

I've made temporary isolation with a concrete garden paver, cut sections of pool noodles and a sandstone slab, until deciding which feet to buy for the sandstone.  This has worked and I've checked for any sound through the speakers when tapping on the paver, there is none.  I did this check with the stylus resting on a stationary record, as suggested in the 'Best Isolation Platform' thread.

 

While doing this check I found that when I turned the volume right up, to around 3/4, there was some sort of issue developing with a pulsing, or throbbing coming through the speakers.  Please excuse my basic description, my journey into the technical side of Hi Fi has only recently begun.

 

I've not noticed this problem before, as I rarely have the need to turn the volume up so much.  But with no music playing, and doing the mentioned check, I did.

 

My older TT has been sent of for servicing and new cart/stylus, so I don't have another to connect and check.

 

I have recently taken the back covers off the speakers for cleaning inside and tightening some driver screws which were creating an annoying little rattle.  I have left the covers off to hear how they sound with an open back.

 

As a novice it seems to be some sort of feedback.  As I turn the volume up it begins and builds quickly, and the pulsing is very rapid with a very low tone.  I am unable to see the drivers while this is happening as the front mesh is fixed to the speakers, but from the sound it seems to emanate from the bass drivers. 

 

The TT is situated just over 1 metre from the front of one speaker.

As I've just sorted out the isolation, I thought I might check with fellow members for any thoughts before moving everything around again.  I know many other vinyl lovers have their TT quite close to speakers without problems.

 

Thanks in advance for any ideas or suggestions.

 

Regards.

Ant. 

[Gryffles]

Read up on subsonic filters. 

 

From what you have described sounds like that’s what you need.

[BuzzzFuzzz]

Thanks @Gryffles - The amp does have a 30Hz subsonic filter, will turn it on and have a listen.

 

Cheers.

Ant.

[aussievintage]

33 minutes ago, BuzzzFuzzz said:

While doing this check I found that when I turned the volume right up, to around 3/4, there was some sort of issue developing with a pulsing, or throbbing coming through the speakers.

It will be acoustic feedback.  Despite isolation, this can happen directly via the air to your cartridge/tonearm.

[aussievintage]

1 minute ago, BuzzzFuzzz said:

Thanks @Gryffles - The amp does have a 30Hz subsonic filter, will turn it on and have a listen.

That should help, but also, positioning might cure it without the need for a filter.

[BuzzzFuzzz]

Have done a re-check with the subsonic filter on.  It did allow me to turn up a little further, but not much.

 

I am running two sets of speakers, the Technics and some Harman floor stands, but the issue is only through the Technics, which are quite large and closest to the TT/amp.

 

Looks like it may be positioning.

 

I am a little limited with cable lengths, any suggestions on how far I should have the TT from the speakers, or simply a matter of trial?

 

Having a little whinge now - I've recently moved interstate, found a nice rental with no immediate neighbours which is ideal for music lovers.  I've sorted the layout of the rooms, acquired some cool, second hand, timber furnishings, and finally began feeling settled. 

Now I have to re-arrange everything in the living room again.

Not a problem for me as everything centres around my stereo, but a pain in the arse as I was expecting a nice relax today after a busy w/end at work.

 

Oh well, here we go.

 

Will update when sorted.

 

Thanks guys.

Edited October 6, 2019 by BuzzzFuzzz

[aussievintage]

I have found having the speakers well in front of the turntable helps a lot.  My speakers are the nearest thing to my listening position.  I walk through and behind the speakers to get to the turntable to change a record.

[Guest Muon N']

That amp is spec'ed at 33 watts per channel into 8Ω, those speakers are what sensitivity? I'd be careful turning a low powered amp up high unless the speakers are a very easy load and high sensitivity.

 

Edit: not the issue you are dealing with, but i'd exercise care with levels with a signal unless they are sensitive, I guess they are likely 89db to 94db, somewhere in that range.

Edited October 7, 2019 by Muon N'

[BuzzzFuzzz]

1 minute ago, Muon N' said:

That amp is spec'ed at 33 watts per channel into 8Ω, those speakers are what sensitivity? I'd be careful turning a low powered amp up high unless the speakers are a very easy load and high sensitivity.

Hey Man.  Thanks for your input mate.

 

This is the area where I need a lot of help.  As mentioned in my first post, my understanding of the technical side of Hi Fi is extremely limited, a journey just begun.

 

I'm not sure what sensitivity the speakers are, they are 3 way, 8 Ohm, 200W, as listed on the back cover.  That's all I know, they were bought second hand with no paperwork and a google search doesn't bring up anything on this model, which is unfortunate as I have two pair of them.  The drivers don't look like anything flash and are made in Taiwan.

Is sensitivity the Ohm rating alone?

 

I really need to read up on some material explaining some basics, but find a lot of it too confusing as I'm not really technically minded.

 

Do you, or anyone else have some suggested reading aimed at the novice/beginner.

 

 

 

[BuzzzFuzzz]

I've been looking at different speakers, a phono stage or pre amp, and also amps and power amps.

 

At this point I don't really know how to match things up, or even if a phono stage is the same thing as a preamp.

 

I'm in a rural area and auditioning gear will be difficult.

Edited October 7, 2019 by BuzzzFuzzz

[BuzzzFuzzz]

Oops.

[Guest Muon N']

24 minutes ago, BuzzzFuzzz said:

Hey Man.  Thanks for your input mate.

 

This is the area where I need a lot of help.  As mentioned in my first post, my understanding of the technical side of Hi Fi is extremely limited, a journey just begun.

 

I'm not sure what sensitivity the speakers are, they are 3 way, 8 Ohm, 200W, as listed on the back cover.  That's all I know, they were bought second hand with no paperwork and a google search doesn't bring up anything on this model, which is unfortunate as I have two pair of them.  The drivers don't look like anything flash and are made in Taiwan.

Is sensitivity the Ohm rating alone?

 

I really need to read up on some material explaining some basics, but find a lot of it too confusing as I'm not really technically minded.

 

Do you, or anyone else have some suggested reading aimed at the novice/beginner.

 

 

 

Sensitivity is the decibel level (db) the speakers put out at 1 watt power measured at 1 meter distance. For every increase of 3db it requires doubling power.

 

Different to impedance which is measured in ohms, usually only nominal is in the specs, but across the full frequency range 20Hz to 20kHz this impedance rises and dips, lower makes for a more difficult load where more current is called upon from the amplification

 

Those speakers shouldn't be too bad, likely a sensitivity of between 89db and 94 db.

Edited October 7, 2019 by Muon N'

[Guest Muon N']

4 hours ago, BuzzzFuzzz said:

I've been looking at different speakers, a phono stage or pre amp, and also amps and power amps.

 

At this point I don't really know how to match things up, or even if a phono stage is the same thing as a preamp.

 

I'm in a rural area and auditioning gear will be difficult.

A pre amp is of course pre amplification, sometimes they have a phono pre amp built in, the signal level of a TT cart is small, smaller with MC, so that signal has to be not only boosted but also the RIAA or equalization has to be corrected as because of the vinyl format requires the music be laid down with adjustments to bass and treble so the stylus doesn't go berserk and jump off the record, so the phono stage corrects this for normal play back.

The phono stage brings the level up around what is called line level, Then a pre amp that is separate or built into and 'integrated' amp raises that level for the next stage...the power amp, separate or integrated with the pre in the case of an integrated amp.

 

Phono stages are connected to line level inputs, like that of CD, AUX and cassette tape inputs, or in the case of an integrated amp that also has a built in phono stage you connect the TT directly to the Phono inputs.

Edited October 7, 2019 by Muon N'

[BuzzzFuzzz]

Thanks @Muon N', was just reading up on sensitivity.  I don't have a sound level meter.  Is that something that might be available as a phone APP?

 

As you mentioned, if the amp is rated at 33 watts per channel, how do I have 1 watt power to measure at I metre distance?

 

If the likely sensitivity of the speakers is between 89 and 94db, does that mean they are an easy load and high sensitivity?

 

The amp does have a phono stage, as I connect the TT directly into it.  I am thinking I may get a better sound if using a phono stage, and have been looking at the Schiit Mani with an upgraded power supply.

 

The cart is Music Hall Magic 2 MM.

 

Deeply appreciate your time and input mate - thanks.

Edited October 7, 2019 by BuzzzFuzzz

[BuzzzFuzzz]

If my amp has a phono stage inbuilt, can I then use an external phono stage connected to the phono input?

[Guest Muon N']

Those speakers are likely a pretty easy load, you don't need to measure them

 

No, If you get a separate phono stage you will connect it to a line level input like AUX ( auxiliary ) and not the phono input, connecting it to the phono inputs will be adding far to much gain and you will have two phono equalization compensations being done when only one is needed and works, not to be done

 

Edit: Phono equalization (RIAA)

https://en.wikipedia.org/wiki/RIAA_equalization

Edited October 7, 2019 by Muon N'

[aussievintage]

Maybe, to clarify...    If your power amplifier is not huge, then when you want to listen loud, you turn it up.  Now as any amp approaches it's ratings (even if they are honest ratings) you get more distortion.  Distortion is what kills speakers, particularly tweeters, worse than overpowering them.   Hence people buy bigger amps than what they really need, and so can listen loud, at what is still an easy drive for their big amp, and hence low distortion.

 

But, you should also note, that many people only use a few watts of power, for normal listening levels, especially if their speakers are reasonable sensitive.  So, 30 watts may be plenty for your situation, and you can happily listen "loud" at maybe a third of your amps power rating. It just depends.

[aussievintage]

22 minutes ago, BuzzzFuzzz said:

 

As you mentioned, if the amp is rated at 33 watts per channel, how do I have 1 watt power to measure at I metre distance?

It's not something you need to measure yourself, it's normally part of the specification for the speakers.  You may find the specifications for yours on the internet.  Most are out there.

[Guest Muon N']

With the original issue you pointed to, try different isolation under the table, instead of the pool noddles and sand stone, if you can try placing the table on one of the large 35mm thick Bamboo chopping boards from IKEA, and place 4 of these White's anti-vibration blocks under the Bamboo chopping board.

 

https://www.ikea.com/au/en/catalog/products/60233431/

 

You can try the smaller blocks that are more dense or the larger ones that have larger air spaces between the material, see what ones work best for isolation between the Bamboo Butchers block and rack shelf.

 

https://www.bunnings.com.au/whites-50-x-50-x-12mm-anti-vibration-squares-8-pack_p3961977

 

https://www.bunnings.com.au/whites-on-site-100-x-12-5mm-rubber-anti-vibration-mat-4-pack_p3961547

[Guest Muon N']

1 minute ago, aussievintage said:

It's not something you need to measure yourself, it's normally part of the specification for the speakers.  You may find the specifications for yours on the internet.  Most are out there.

I couldn't find it myself, but other similar models seem to be in the low 90db range.

[aussievintage]

2 minutes ago, Muon N' said:

I couldn't find it myself, but other similar models seem to be in the low 90db range.

 

yes, unless you are in a large room and sit a long way from the speakers, you should be fine at all normal listening levels.

[Guest Muon N']

2 minutes ago, aussievintage said:

 

yes, unless you are in a large room and sit a long way from the speakers, you should be fine at all normal listening levels.

I agree, he should be fine in normal listening situations.

[08Boss302]

Is the issue only when you have the amp set to your TT?  If you are running an ext phono stage have tried a different auxillary input in the amp - just a process of emimation.

I have my to the side of my speakers and in front and have no issues.  Cable from TT to phono stage about 90cm and then i've got a bout 3m of cable from phono stage to back of amp running around the room.  Keep the run from the TT to the phono stage no longer than 1m but from phono stage to amp its not as critical IME.

 

Have you checked the wires on the cartridge to the tone arm, nothing loose or touching there also?  Also check grounding..

 

I usually start with the simple stuff and work my through that way, if its still happening then I look to move stuff but more often than not for me its been a grounding or input issue

 

 

[Rocketfrogs]

2 hours ago, BuzzzFuzzz said:

The amp does have a 30Hz subsonic filter, will turn it on and have a listen.

Excessive Cone excursion (that's woofer pumping not Stoner's on a road trip) was a problem I had with a new phono stage.  I used Harrison lab 30Hz inline filters and that solved the problem.  Since your amp handily has a subsonic built in hopefully that will solve the issue.

[08Boss302]

http://myhometheater.homestead.com/splcalculator.html

 

Hey Ant, not going to help with the noise but this is cool calculator to give you some idea of speaker sensitivity and amplification power

Edited October 7, 2019 by 08Boss302