Records with really wide runouts: Why?

Wasn't sure if this belongs in Music or Hardware...

Anyway, today I obtained the VMP double LP of The Flaming Lips - The Soft Bulletin. I know that albums are sometimes spread across two records to give the grooves more room to "breathe", so I was surprised when I noticed the runout grooves. The runout area is really wide, something like a radius of 4 inches.

What would be the reason for not spreading the musical grooves out more? There wasn't enough dead space to make me think that they could've squeezed this onto one LP, but if you have space on a side, why not take it up?

 

Hi!

I think they don't need so much extra space. I have an album - Siouxsie and the Banshees - Superstition 2xLP, 2018 remaster - where the forth side is completly empty and there is only a big sign stamped on it.

Also they avoid Inner-Groove-Distortion (IGD). Most of my reissues which I bought recently are not cut as close to the label as are most of my 80s records.

Bye Andrea

 

Think about magnetic tape. You get higher resolution by increasing the speed of the tape speed this noted by inches per second. Because the groove on a record is a spiral, for each rotation the linear length of the groove decreases. The label is 4 inches in diameter or a 2 inch radius. So your 4 inch runout radius is incorrect. It can't be 4 inches. A 12" record has a 6" radius. You've described a record without a groove. So I'll assume the runout is 2 inches from the label. For the sake of simplicity I'm going to approximate length of the groove at the run in and I'm going to use 12 inches because it's easy. The perimeter of a circle is 2πr or πD, so the length of the groove is 12π or about 37.7 inches. The rotation speed of an LP is 33-1/3 rpm or 0.55 revolutions per second. So 20.9 inches per second (ips). Now if you we go with a 2 in runout and add the label we have an 8 inch diameter. So calculating the ips at the runout we have 14.0 ips. If we go in another inch our radius is 3 inches with an ips of 10.5 ips. The more common record with a 1 inch runout is 1/2 the ips of where it starts, which means it sounds much worse.

It's not about breathing, or whatever that is, it's about inches per second.

 

Very good points about IGD and tracking speed, thanks. I know that spacing the grooves further apart can be beneficial, but now I see the incentives to not do that.

 

Assuming they even thought about it - which they might not - there is a compromise between modulation of the groove (i.e. volume), inner groove distortion, and playing length. If your music is 20 minutes or so per side, there is not much choice anyway. If it is significantly shorter than that, they can play with the other two: A wide runout groove means they avoid the inner parts of the record, where the absolute speed is lower, thus the "wiggles" for the same frequencies have to be packed tighter, thus reducing fidelity. That requires lower modulation though, thus decreasing SNR. The opposite is to maximise modulation, thus optimising SNR and creating a really loud record, and in order to minimise the problem of inner groove distortion they can cut the record at 45. That is the philosophy behind 12 inch singles, but on an LP you want 33 throughout so as to not confuse listeners.

 

I will totally agree with everything you said except for the part about it not being about breathing. Many mastering engineers like having a little space or breathing room between the grooves. It is a balancing act between groove spacing, the lowest frequencies in the grooves and runout groove size.

 

Ideally you want the grooves as close as possible without actually touching, arbitrarily increasing the pitch adds nothing of value to the record and can only detract from overall SQ. Of course the groove excursion (low frequency content, signal level, stereo width) will dictate just how close the grooves can get.

 

The radius of the label (R1) is 2 inches, the radius of the runout groove (R2), which includes the label if course, is 4 inches. R2 - R1 is the width of the runout groove (also 2 inches).
The radius of the record, R3, is 6 inches. This leaves 2 inches (R3 - R2) for the musicians the run in groove.
This is how I interpreted the OP's wordsw seemed not only correct but completely clear to me.
Put slightly differently, the 4 inch runout radius that you describe is actually the label and the runout in the OP, and hichthe runout has a width of 2 inches.

 

Theres not much benefit to space grooves apart. You want them as close together as possible given the material youre working with.