Need help and advice on grainy sound

[L Plate]

Can anyone suggest what should I do to get rid of the grainy sound?
I have a pair of Monoblocks:
500W/RMS @8 OHMS and 900W/RMS @4 OHMS.
Frequency response : 10Hz-20Hz +/-0.5dB
Distortion (THD) : <0.01%
Damping coefficient : >400
Signal-to-noise ratio +A: 118dB
Gain: 26dB
Input impedance : 47 Kohm

Pre-amplifier (Hybrid type)
Maximum undistorted output amplitude : RCA port 9V, XLR port 18V, Tube port 8V, Subwoofer port 9V
Input impedance : 47K ohms
Output impedance : 100 ohms
Distortion : <0.005%; Tube port <0.5%
Input sensitivity : RCA 3V; XLR 6V
Signal-to-noise : >120dB
Frequency response : 10Hz-80Hz

The loudspeakers are floor-standing rated at 100dB/mW.
Power : 300W. Impedance : 4 Ohm.
Speaker configuration : 2 x 12 inch woofers and H-7 horn.
Horn is in the centre.
Speakers measurements : 117cm (H) x 34.4 cm (D) x 34.4 cm (W)

I have installed XLR in-line Attenuator (-20dB) and in-line Unbalanced Attenuator (-12dB) to stop the hissing sound.

Whenever I play rock music, I get this grainy sound at some parts of the music. This happens when a second guitar sweeps in or more than one vocalists or shall I say a chorus. But something strange to me is that I have no problem with Classical music, Jazz, Jazz Rock, Acoustic music and even with some Asian music (not guitar driven type). They are mainly traditional instruments like flute, Gong, heavy drum, etc etc.

Some suggest that I replace the speakers and either buy a pair of low sensitivity speakers around 86 dB/mW or amplifier with lower power output.
Can anyone kindly advise?

Edit: Some say that it is called "Intermodulation Distortion IMD".
The worst distortion when I play Fleetwood Mac Rumours especially with Stevie Nicks' vocal and when Christine McVie starts to join in with the guitar coming in. Songs like Dreams and Silver Spring

 

[voodooless]

The question is: What is the source of the issues? Just randomly replacing stuff won't solve anything. Can you maybe record the grainy sound? Does it also happen on a frequency sweep? If so, maybe try to identify whether it happens at certain frequencies? And if so, does it happen through both speakers, or only one? Does it happen on both the tube and transistor outputs of the pre-amp?

 

[L Plate]

The question is: What is the source of the issues? Just randomly replacing stuff won't solve anything. Can you maybe record the grainy sound? Does it also happen on a frequency sweep? If so, maybe try to identify whether it happens at certain frequencies? And if so, does it happen through both speakers, or only one? Does it happen on both the tube and transistor outputs of the pre-amp?

I use Foobar2000 player with different file formats namely DSF, PCM, Flac and MP3. I ripped the files from DVD Audio, Blu Ray, and Redbook CD and SACD.
This usually occurs whenever it hits high notes followed by another vocalist with guitar sweeping into the song. One good example is Fleetwood Mac Rumours which I have ripped from the DVD Audio disc. Tracks like Dreams, Go Your Own Way, Silver Spring, etc etc are very obvious and they are very high pitch especially with Stevie Nicks vocal. But this is not the only one. Elton John DVD Audio Goodbye Yellow Brick Road is the same. I suspect that it is at the upper mid range say 2 to 3 kHz.
Yes it happens on both speakers.
Yes it happens on both tube and transistor outputs of the preamp.

 

[Redacted]

IMD can make a "gritty/grainy" sound, but so can incorrect gain structure (causing clipping). It could also be poor rips - what software did you do use to make the the rips?
You don't say much about what feeds the pre-amp - you said that your media player is FB2K, presumably on a PC. Does it feed a USB DAC or PC internal DAC or what? We need to know more about the topology, and the actual units you are using, not the specs to pulled off the internet, which are mostly irrelevant...

As @voodooless is implying, you need to start from the source and work downstream. So test play some affected ripped files with FB2K set to exclusive WASAPI mode through the PC's internal DAC to headphones. If you still hear the distortion, then it either a file issue or a PC issue. To test if it's a PC issue, put one the files on a phone say, and repeat. If the files are fine on other systems, then it's a PC issue - if using the internal DAC, can you use an external DAC instead? Do you have an audio CD player you can use to test the pre-amp and the rest of of the system? Really, it's not that hard to work out the source of the problem with a bit of logical analysis!

 

[Chris A]

Tell us a lot more about your loudspeakers, particularly your horns. Do the horns have slots in them? What exact model of compression drivers are you using--are they titanium dome drivers?

Also, can you tell us exactly which version of Fleetwood Mac Rumours you are referring to: what is the exact year of release of the version of that album?

Third, have you taken an in-room acoustic measurement (like REW) of one or both of your loudspeakers (one at a time, please)? If so, can you post those measurement files (i.e., not screenshots of magnitude response only)?

Chris

 

[Cote Dazur]

can you listen to that track on Head Phones? that would clear if it is the source ( probably not the source ).
can you use or borrow an other amplifier, any amplifier will do.
Do you have an other pair of speaker, or can borrow one.
Can you move your speakers position, and/or your setting position. My bet is that it is related to your room and listening position.

 

[voodooless]

Do that frequency sweep... Also try at diffrent SPLs

 

[Chris A]

Some suggest that I replace the speakers and either buy a pair of low sensitivity speakers around 86 dB/mW or amplifier with lower power output.
Can anyone kindly advise?

No--unless the horns and/or the compression drivers you have are low quality slot-type throat horns and titanium dome tweeters that chatter above 6-8 kHz (i.e., non-pistonic modes).

The use of an attenuator to suppress amplifier noise (quiescently) is a sign that you already have a noise problem in the electronics that will also tend to produce grainy sound characteristics.

Edit: Some say that it is called "Intermodulation Distortion IMD".

This is the type of distortion you hear when the loudspeakers sound "loud" and opaque when playing loudly (above 100 dB at the listening position using horn-loaded HF drivers). Since you are using higher efficiency loudspeakers, this eliminates the chance that you're listening to IMD. But higher order horn modes is a real possibility, especially if the horns have slots in their throats.

Chris

 

[OldHvyMec]

Anything from a "RIP," I would question. The first thing I would try is different source material. It saves time and a lot of guessing.

The original Fleetwood Mac Rumors was recorded to analog tape. It was released on vinyl, cassette, 15ips reel-to-reel and on 8-track tape. I would really question the recording you have now. I had it on both 8-track tape and still have 2 copies on original vinyl.

You have a record player?

Regards

 

[Redacted]

Anything from a "RIP," I would question. The first thing I would try is different source material. It saves time and a lot of guessing.

Why so? I have ripped tons of my CDs, mostly using fre:ac on a PC and often on "paranoia" settings. Every one has been excellent - so long as the bits can escape the transport, they appear to be fine, if you trust accurip and my own ABX tests etc. I'd be surprised if the OP didn't get "Rumours" off a CD.

But yes, start with the source and work downstream - there will be a reason for poor sound. Check for bad cables and connectors too.

 

[SSS]

Since at DVD rips the sound is not perfect it may be the rip process? Other source may be the horn. There are PA horns which are good for loud audio distribution but not good at high fidelity in a room. And further, a very strong amplifier for sensitive horn may be used with low power where the distortion may be higher than at higher power. But first in my opinion it is needed to test the soundfiles with a different well known good system.

 

[voodooless]

Easy to verify if it's the source: just play it elsewhere. Headphones or IEMs are ideal for this.

 

[fpitas]

Since at DVD rips the sound is not perfect it may be the rip process? Other source may be the horn. There are PA horns which are good for loud audio distribution but not good at high fidelity in a room. And further, a very strong amplifier for sensitive horn may be used with low power where the distortion may be higher than at higher power. But first in my opinion it is needed to test the soundfiles with a different well known good system.

Agreed that some PA horns are inappropriate for high-fidelity, although in this case I'd guess the horn crossover is allowing low frequencies into the driver.

 

[SSS]

Agreed that some PA horns are inappropriate for high-fidelity, although in this case I'd guess the horn crossover is allowing low frequencies into the driver.

Agree too. But we no nothing about the horn, the x-over cut frequency and the steepness of it.

 

[fpitas]

Agree too. But we no nothing about the horn, the x-over cut frequency and the steepness of it.

Yes, I was hoping to shake loose some information.

 

[kemmler3D]

Knowing something more about the speakers would help.

If you're getting audible distortion on Dreams then my first guess is something is wrong with the compression driver, but you can get a better idea by doing a frequency sweep as others have mentioned.

Does not need to be fancy to make progress. You can do it manually and by ear using this: https://www.szynalski.com/tone-generator/

Go slowly and listen for problems like you hear with music.

If you can't hear anything wrong that way, the problem is probably somewhere upstream from the speaker.

 

[Redacted]

Yes, I was hoping to shake loose some information.

Yes, thread is spiraling away a little because of lack of data.
Nevertheless, the logical order is to go through this from the sound source and outwards.

 

[tineared]

I use Foobar2000 player with different file formats namely DSF, PCM, Flac and MP3. I ripped the files from DVD Audio, Blu Ray, and Redbook CD and SACD.
This usually occurs whenever it hits high notes followed by another vocalist with guitar sweeping into the song. One good example is Fleetwood Mac Rumours which I have ripped from the DVD Audio disc. Tracks like Dreams, Go Your Own Way, Silver Spring, etc etc are very obvious and they are very high pitch especially with Stevie Nicks vocal. But this is not the only one. Elton John DVD Audio Goodbye Yellow Brick Road is the same. I suspect that it is at the upper mid range say 2 to 3 kHz.
Yes it happens on both speakers.
Yes it happens on both tube and transistor outputs of the preamp.

To aid the investigation, kindly list the manufacturer and model of components in the signal chain and attempt to make a recording of the distortion.

 

[MaxwellsEq]

Do you have tinnitus? Do you possibly have hyperacusis? Have you had a hearing test recently?

I'm not trying to be rude, but sometimes hearing health problems can make certain sounds seem distorted.