When using the 7" format, it is always wisest to cut at 45. This allows for a faster groove velocity which gives a clearer sound with less distortion and louder levels.
Technically speaking, the clarity of the record depends on groove velocity, how fast the vinyl passes under the stylus. The faster it does, the better the sound.
| Size | Speed | Outermost Groove | Innermost Groove |
|---|---|---|---|
| 12" | 33-1/3 | 20.1 ips | 8.5 ips |
| 10" | 33-1/3 | 16.6 ips | 8.5 ips |
| 7" | 33-1/3 | 11.4 ips | 7.5 ips |
| 12" | 45 | 27.1 ips | 11.5 ips |
| 10" | 45 | 22.4 ips | 11.5 ips |
| 7" | 45 | 15.5 ips | 10.2 ips |
| 10" | 78 | 38.9 ips | 15.9 ips |
To maintain a fast groove velocity on a small record, it's recommended to turn the record faster. This is why seven inchers sound better at 45.
The problem then arises that the faster you turn the record, the quicker you use up the time you can cut. Packing the grooves closer together for longer times is what needs to be done.
When packing the grooves closer together, there is less room for the vibrations of the grooves, and therefore, the level has to be reduced.
The standard level for a 45 is 4db louder than that of a standard 12" LP, and it's maximum length is only 3:30. This is fine for a pop single. Reducing the level to that of a standard 12" LP will allow 5:15 on a side of a 7". 2 db quieter than a 12" LP will allow 6:00, 4 db quieter than a 12" LP will allow 6:30, and 6 db quieter than a 12" LP will allow 6:50. As a reference, 6 db quieter is half the volume.
On some projects, if the bass is not that strong or infrequent, we can use a computer controlled system to pack the quieter, less bass heavy parts, and spread the grooves for the louder and more bass heavy sections. We have had success with cutting 6:30 on a 45 peaking at 2 db louder than a 12" LP. Each cut has to be individually evaluated, and there are times when the best we can do is still 2db quieter than a 12" LP. Even at that, the higher 45 speed will give a better clarity with less distortion than cutting at 33. It's a trade off, but I personally prefer clarity over level.
The next issue is that of pressing a 7" record with that much time. In general, 7" presses are designed for fat deep grooves, and therefore the pressure, heat and time in the press are designed for this type of groove. Once a record strays from that norm, adjustments may have to be made. United Record Pressing will not guarantee a 7" 45 over 4:30.
Sometimes, there is no choice but to go ahead with a 7" at 33. We generally cut this format at 3 db quieter than a standard LP to avoid distortion. Even as such, the high end suffers at this slower groove velocity. If you music is not that crisp, and distortion is not an issue, the 7" 33 format may work just fine.