Direct drive vs belt vs rim vs idler arm

Richard,

Great post about the arrival time difference between our ears of a sound 15 degrees away from straight ahead. It really made me think about how sensitive our ears and brains are. I'm kind of surprised that I never thought about this. I wonder if this has something to do with components that soundstage and image very well. It could just be that the component processes or amplifies (whatever the component is doing whether it be an DAC or an amplifier) all frequencies and gets them to the output terminals in exactly the same amount of time. The component would also have to have the same exact, non-wavering processing time for the right and left channels.

I checked the math (twice) and got a time difference of 0.00008 seconds between the left and right ears, though, not 0.0000053 seconds as you calculated. I may have made the same error twice or maybe not. It still doesn't change the fact that the time difference is extremely small for a sound that is 15 degrees away from straight ahead.

For those who didn't do the math, at a distance of 4 meters, 15 degrees is equal to the sound source being about 1 meter away from straight ahead. 1 meter is a reasonable distance to use for this calculation. I think anyone could tell if something is straight ahead or 1 meter to the right with their eyes closed. We are probably capable of hearing even smaller changes in distance.

We can tell the direction of a sound source by the arrival time difference between our ears.

A sound source 15 degrees to the right of straight ahead at a distance of 4 meters will reach the right ear slightly sooner, but this is not all that clues us into where the sound is coming from. The sound will also be louder in the right ear because there is a more direct path into the right ear. It's more than likely both things that help us determine where sounds are coming from- time differences and volume differences.

Dear Win, I place you way above me in experience and knowledge, when it comes to turntables. However, this is the first time I find myself disagreeing with you AND thinking that I have some personal hands-on experience to back up my quibble. Specifically, I would take serious issue with your contention that the plinth is not so important for direct-drive turntables. In my home system, I have had a lot of experience listening to different DDs in different plinths, meaning, the same motor mounted in different plinths and/or different motors mounted in the same (type of) plinth. The plinth is so "in the picture" and can do so much harm to DD sound that I have some empathy for Halcro, et al, who espouse the no-plinth approach to DD use, because a "bad" plinth does much more harm than no-plinth. (However, I maintain my position that, even with all the sonic problems a plinth can introduce, one is still necessary; it just has to be really carefully designed and built, and there is no substitute for trial and a willingness to admit error.) I would posit that what you do not like so much about DD's you have auditioned is largely due to plinths or to subtle suboptimal function of the drive system.

Hey, I love idlers too, as you know.

Mosin,
an excellent summary you made which I will fully underwrite. Especially on idler drives many among us seem to have made not the best experiences and this is definitely due to the equipment they were working with. If you put a lot of efforts in carefully designing and implementing designs on belt drives (best with two excellent motors and a perfect steering) as well as idlers you reach wonderful results. It is more the concept and its implementation rather than the difference between the various drive technologies which makes the difference!

Quote:I believe a great direct drive is the most difficult to achieve because of audible artifacts introduced by most implementations

I would have to say this is the total opposite IMO Idler would be the most difficult because of all the mechanical things it possess..... motor. idler wheel..idlerwheel arm etc. etc...I personally played with a few Idler TT but mostly the lenco...problem is these tables will not play the bottom end like a good direct drive period! most people that use idler tables use horn systems with limited bandwidth so they do not understand what i mean...the idler (lenco) can give you a false impression of bottom end because its shelved up in response in the 40 cycle range but homogenizes the last octave....please do not kid yourself they are very nice sounding but not IMO in the same league that the upper best DD are

win we talked about this remember...I think you may have taken offense and if so I am sorry... I hear what i hear and i know what i know

Lawrence
Fidelity Forward