Re: iMac for Recording

[Rainer Straschill <moinsound@googlemail.com>]

>> Will I have issues with the iMac using just the one hard drive? I 
>assume that I
>> could always, at least, utilize an external USB or Firewire-connected 
>drive if
>> necessary. And, am I hanging onto an outdated parameter as far as the 
>rotational
>> speed is concerned? THX!
> It depends on the number of channels you want to record
> simultaneously. Both my Macbook and iMac have 5400 rpm drives and run
> fine when recording 4 tracks. FYI: I haven't tested 6 or 8 tracks yet
> on these machines but I would expect that 7200 rpm is recommend when
> recording 8-16 or more tracks of audio simultaneously.

The parameter of a HDD relevant in this context is the continuous
(write) transfer speed - which somehow correlates to the RPMs, but not
exactly in a linear fashion.
Correlating the number of channels with the harddisc's RPMs now feels
like looking for a dependency between top speed of a car and its rev
redline.

To get more technical: contemporary *mobile* HDDs (e.g. Samsung
Spinpoint M6) are specified as 860Mbit/s (~100MB/s) from buffer to
disc and 300MB/s from host to buffer. For comparison, a mono audio
track (at 24/48, which makes sense in a lot of cases) would be
48000(samples)*3(24 bits=3 bytes)/(1024*1024 "byte to Mbyte") =
0,137MB/s. This is several dimensions below what your 5400RPM
harddrive can do (or to put it in context to the car example - even an
engine with a 5000rpm redline will be fast enough for innercity
traffic).

Continuous transfer rates of harddiscs are never the parameter that
will endanger any kind of audio recording today (that was different
like 15 years ago or so...). So unless your OS is configured oddly (so
it has a lot of disc access apart from the audio traffic - here the
second harddisc approach mentioned by Paul would help), there
shouldn't be any problem at all.

To give a real-life example: "A Tätowierte Katz'"
(http://moinsound.wordpress.com/2010/05/09/a-tatowierte-katz-another-twitterchords-tune/)
was recorded onto 15 audio tracks at 24/48 on a machine with a 5400prm
harddisk. Worked fine.

         Rainer