Beogram: Dust covers on or off during when playing

[Giorgione]

Glitch wrote:

It seems like a significant amount of the engineering innovation was a result of overcoming the compromises dictated by the styling. This seems most evident in the speakers made between the 1980’s and 2010’s.

That’s what most people, let alone the audio-files think and gifted the world with such hilarious B&o folks stereotypes personificated by the yuppie neighbours as seen in “National Lampoon’s Christmas Vacation”, ouch! I had Pentas, always thought these pipes and towers were’t really great, the “Sausalitos” were fine, even the BL3 for restricted spaces. But all these powered speakers were lacking something I found again in passive gear.

Giorgione wrote:

I’d like to hear opinions/findings/speculation/test results about these alleged disturbing resonances transmitted via the lid

Have you considered duplicating the pro-jectusa test? This seems like an easy test to setup. You would also have the benefits of testing at the listening levels that you normally use along with your exact equipment location and room acoustics. I don’t put much merit in other people’s “listening tests”. There are too many possible variables that make any results meaningless. Glitch

Easy to setup? How? I don’t think I have the gear to do that – only the ear, ha ha. I don’t pretend my test to be objective but if it sounds better to me either wa it’s still meaningful, to me at least. I also think that most parameters remain the same, whether doing a hearing as well as an instrumental test, the only variable being the lid.

[Glitch]

Giorgione wrote:

Easy to setup? How? I don’t think I have the gear to do that – only the ear, ha ha. I don’t pretend my test to be objective but if it sounds better to me either way it’s still meaningful, to me at least. I also think that most parameters remain the same, whether doing a hearing as well as an instrumental test, the only variable being the lid.

One would already have most of the equipment needed for the test as part of their normal stereo system. Additionally, a multimeter and a phono preamp would be needed to take the reading from the turntable. The phono preamp linearizes and amplifies the signal from the cartridge. The amplified signal should be large enough to measure with the multimeter on the Vac setting. MP3/FLAC test tones would provide the source tones. The only other thing needed is a fair amount of patience to take and record the readings.

I would expect that you will have a difficult, if not impossible, time running a meaningful subjective test. I won’t go into all of the details, but Google something like “A B audio test pitfalls” and you’ll find plenty of info. In addition to the things typically listed, you will also have to deal with echoic memory in the relatively long time it takes to switch lid positions.

I guess in this case, “easy” is a very relative term ;-).

Glitch

 

[Giorgione]

Thanks for the instruction but I neither have an external phono pre-amp nor a multimeter. The physical principle according to the project test seems to clearly indicate that there is an effect and I don’t see any commercial reason faking something here. Maybe a say 4002 will make a difference due to its construction? I will listen to a full record first with closed and then without lid, so there will be a target onject A/B but target group A only – me! Maybe I will repeat the test with other record the upcoming days and eventually stick with whichever versions sounds better to me, and to me only 🙂  I never cared about figures much, only wondering whether somebody in the community came along this question in the past. Seemingly not really.

[Glitch]

It is important to distinguish between “different” and “perceptibly different”. Pretty much any time one makes a change, it will be “different”. This even includes items that were meant to be the same. It was not surprising to me that the three lids positions had different results. What isn’t clear is if any of them are perceptibly different.

What I believe that the test needed to show is a comparison between the noise signal (i.e. the lid/chassis resonance at the cartridge) and the equivalent cartridge signal. The measured relative difference between these two is important. There are many studies that define what a typical human can differentiate. Something like this https://www.ussi.com/acoustical-rules-and-demystifying-decibel.php (this was simply the first hit I noticed on Google).  The good thing about running a test like this is that it takes the monkey out of the loop.

My postulation is that, at typical listening levels and room acoustics, the level differences between the signals, lid up/down/off, are lower than can be perceived. The problem with human judgement tests is that people will “hear” what they want to hear. Sort of like the audio equivalent of “these are not the droids you are looking for”. 😉

I have very good hearing, but I don’t trust my brain to get it right. This is because I’ve tried running a test myself, then getting help from others and running a similar test double blind. The results were different.

Maybe someday I’ll try to run my modified pro-jectusa test and know for sure.

Glitch

[Dillen]

Would the main problem be reflections of the sound produced by the needle playing the record,
or acoustic feedback from the speakers to the record?

The first I don’t believe one moment. And there would be many other things involved having greater effect anyways,
like:
– Do you wear your glasses or not when listening.
– Do you drink red or white.

The latter I can vote for. We ran a quite powerful mobile discoteque many years ago.
At high playing levels the record could take up enough energy from the moving air to jump the needle.
Definitely perceptible.
Closed the lid when playing – problem solved.

The warming up of old rubber suspensions (MMC20CL in particular, in my opinion) also provides a very much perceptible difference – to the better, if you ask me.

Martin

[Glitch]

Dillen wrote:

Would the main problem be reflections of the sound produced by the needle playing the record, or acoustic feedback from the speakers to the record?

I think their proposition is that the sound waves are driving the turntable chassis, which in turn makes its way into the cartridge. I could be misinterpreting this.

The problem with trying to run something like this as a “mental experiment” is that one doesn’t know the contribution of each part of the turntable. For example, how much effect is from the sound waves hitting the record/platter? One could argue that lid down would block the waves from reaching the platter. But lid down could also increase the overall surface area and in-turn the total energy going into the chassis. It isn’t that hard to come up with many more similar combinations, none of which anyone has the answer for.

It also depends on the particular equipment that one is using. I would guess that a lightweight turntable would be more susceptible to these kinds of issues than a heavy one. However, I don’t know if the issue is really an issue on either one. That is why it is important to test your own equipment in your own environment.

It seems that the cartridge suspension response versus temperature would be easy enough to test. Run the frequency response test from a frequency sweep on a test album, record the results, run a FFT. Next do the same at a different temperature. Lastly, rerun the first two test to verify that they are repeatable. I’m confident that there will be a difference since it is well known that the characteristics of rubber change with temperature. However, I wouldn’t be able to say if the difference is perceptible. Even less, I wouldn’t able to say which one is actually “better” since “better” is subjective.

Playing devils advocate… Are most people brains wired to assume the warmer physical temperatures are correlated to warmer music tone?

Glitch

 

[Giorgione]

Glitch wrote:

Dillen wrote:

Would the main problem be reflections of the sound produced by the needle playing the record, or acoustic feedback from the speakers to the record?

I think their proposition is that the sound waves are driving the turntable chassis, which in turn makes its way into the cartridge. I could be misinterpreting this.

I think the Pro-Ject test is clear. Here’s the link again for the convenience of those willing to read it before commenting and speculating:
https://pro-jectusa.com/2024/03/22/should-i-play-records-with-the-dust-cover-down/

Two things regaring these measurements I’ve noticed:
Primary E turntable w/ Ortofon OM 5E moving magnet cartridge -> This turntable seems discontinued, no gear with hinged lids in the Pro-Ject portfolio left, from the cheapest up to the “high end” gear. BTW: The more they cost, the uglier they are, IMHO
Floorstanding speaker pair distanced 1m (3.28 ft) from the turntable -> this sounds rather unspecific to me. I mean, where and how exactly are they positioned? This seems a crucial detail to me. Also, why did they measure only frequencies and not the intensity?

Temperature is important for many reasons, most gear and people prefer warmth, me included 🙂

Cheers

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