Stereo Simulation

[DJBohn]

Stereo Simulation of Monophonic music is a difficult feat at best. Localization of instruments sometimes isn't very good. But stereo simulation of vocals is where Diamond Cut can really excel.

A while back I did a restoration of "Patti Page Golden Hits" on a Monophonic Mercury High Fidelity LP. I used our common procedures of recording it as Stereo on to the hard drive, doing the Impulse Noise Reduction & Continuous Noise Reduction on each of the channels independently, and then recombined them as a Monophonic file. This of course improved the overall output and reduced the noise floor even further.

I then used the File Conversion feature to change the Monophonic file back into Stereo, using a 10ms offset. (The time offset seems to give the illusion of depth in the sound stage) I then opened up the Paragraphic EQ and applied the preset "Stereo Simulator Left Channel Comb Filter Wide" to the Left Channel, and did the same using the "Stereo Simulator Right Channel Comb Filter Wide" to the Right Channel, and saved the resulting Stereo file.

I was very happy with the results. On one of the restored songs in particular, ("Old Cape Cod" - Reached #3 on the Billboard Charts on 06/03/1957) Patti Page is singing lead while they overdubbed the recording with her also singing harmony. The Simulated Stereo sounds so real you'd swear it was True Stereo. It actually gives the illusion of the lead vocal in one channel with the harmony in the other.

Give this Stereo Simulation process a try on these types of vocal recordings. The results may amaze you as well!

[Brian]

Thanks DJ,

In the "olde days" they used to market "pseudostereophonic" records by taking a mono recording and band-pass limiting low frequencies to one channel and high frequencies to the other with a fairly soft-shouldered crossover. Quite popular in its' time - but your technique is much superior. Thanks for sharing it with us!

Brian

[Craig Maier]

Fifth Dimension Album

Hi -

This week I found an old reel to reel tape of (what I think is) the Fifth Dimensions first album (has Up, Up and Away on it). The tape recording was made circa 1969. This recording was made when I was in college and I recorded it via a Magnecord pro tape deck (I think it was a model 1024 or similar) and my own home made model Marantz 7 (tube based) preamplifer*. Needless to say, the recording is impeccably clear, transparent and distortion-less after clean-up.

Unfortunately, this recording was monophonic. Although it cleaned up very nicely, it lacked dimension (no pun intended).

I had completely forgotten about the comb filter that we created years ago in the paragaphic EQ. DJ's post reminded me of it.

So, I followed his process but for one change. I used a time offset value of 20 mSec rather than his value of 10 mSec (I guess it is largely material dependent).

I have been driving around today listening to this CD and it sounds just like a studio stereo recording.

I highly recommend folks trying this on mono material; it is very natural sounding.

Thanks DJ for reminding us of this feature. How on earth did you find it??

Craig

*Note - I repaired high-end audio equipment when I was in high school working for a company named "Stuarts Audio". They are still around (in Westfield, NJ). When I worked there, they were in Cranford, NJ. As a result of my work, I had access to the engineering drawings (schematics, etc) for the various lines of high - end audio equipment including BOM's. I could not afford a model 7 Marantz, so I just built one based on the schematic. I still own it. I am now putting it up for sale for anyone who may be interested in purchasing it. It still works very nicely. Let me know if you are interested in it. The one big advantage of my version over the Marantz version is that Marantz used "bumble bee" paper caps. I did not. I used all mylar and silvered mica types.

[Dan McDonald]

Very impressive! I just tried it with an audience recording I made in 1973 and it sounds so much better than the original. Thanks DJ.

I also tried it on a very early 78 recording of "De Brewer's Big Hosses" by Homer Rodeheaver. I don't notice as much improvement on that one. Would that be because of a limited frequency response of the source material?

Dan

[Craig Maier]

Dan,

Less source signal bandwidth will result in less stereo simulation effect using this technique.

I note that the paragraphic EQ has two sets of comb filters with two of them designated with a suffix of "W". The "W" settings produce a wider slot bandwidth, so maybe experimenting between the regular comb filters and the "W" type may make a difference on certain material. However, I would not suggest mixing between regular comb filters and "W" types on a given project. In other words, do not apply a "W" type comb filter to the left channel and a "non-W" type to the other channel. It was not designed to be used that way.

Craig

[Dan McDonald]

Thanks Craig -
On a related question, is there a way to have the multifilter function so that you could do a process on the left channel only, then a process on the right channel only?
I don't recall seeing this ability, but maybe I'm just not thinking about it the right way. Not just in this particular context, but I occasionally find myself wanting to do something only to one channel and leave the other channel alone.
If it's not possible, It might be helpful to put it under the wishlist for the next version.

Dan

[Craig Maier]

Hi,

You can get the multifilter to operate on one channel only by clicking on the square L or the R button on the toolbar which will then highlight only one of the stereo tracks (the one on which the system will operate).

But, I think that you are asking for the Multifilter to do something different to each channel in the same pass? Is that correct? If that is your question, I do not know of any way to do that right now. I am not exactly sure how we would go about that. I guess each filter would need its own R or L button within. Still thinking about it. Is that correct?

Craig

[Dan McDonald]

Hi Craig -

Yes, that's right. So you could do things like preview the stereo simulation in this thread by having it do both channels before running the procedure.

I was thinking of something like a 'temporary' placeholder that you'd put in the multifilter so that it would apply until you lifted it off, so, for example:

Temp ; File-left channel only ; left comb ; unTemp ; Temp File-right only right comb ; untemp

or
Temp ; File - left only ; paragraphic EQ ; untemp ; normalize (where the normalize would work on both channels after some eq on the left channel)

Anyway that is what I was thinking.

[Craig Maier]

Rick and I will have to look into the code implication of doing that. Would it be easier (or as effective for you) for us to make a dedicated stereo simulation effect module?

Craig

[Dan McDonald]

Hey Craig -

Well, if I'm the only one who would find this useful, then I don't think you should bother with it. It wouldn't be just for stereo simulation.

I just run into situations where sometimes one channel is very different from the other, so it would be useful to do these all in one multifilter, so that you could preview whatever you're doing.
For example, if there's something going on in one channel and you want to fix that, but are unsure of the effect it will have on the entire sound (i.e., both channels together), then it would be useful to have this. Otherwise, you have to fix it as a single channel fix, then play the result, so you don't really get to preview the full effect.

Dan

[Dan McDonald]

I guess another way of doing it would be to have the option of a left channel or right channel pull down in the multifilter window, so that you could do something like this:

left channel ; eq1 ; right channel ; eq2

OR

a button on the multifiler that added a window, one for left and one for right.

Of course, that's just visualizing it, not trying to figure out how to program it.

Dan

[Craig Maier]

Hi Dan,

Yes, I can see where it could be useful in the general case. The most obvious way to do it would be to have a L and R and Both Buttons on each filter and effect, I think. But the obvious way may involve a lot of programming. I will have to chat this one over with Rick and see what his thoughts are on it.

Certainly, it does sound like it would be useful. Does anyone else agree?

Craig

[DJBohn]

Hi,
Such a feature may be helpful to some, at least for some of the tools. I can envision applying something like different degrees of echo & reverb to each of the channels, and being able to hear it right away. And it would also be cool to have a dedicated Stereo Simulator feature in the Tool Bar.

But by the most part, I have gotten very used to our existing methods for most features. I don't think it would be good idea to use such a feature on tools like the Impulse Reduction and the Continuous Noise Reduction features. After removing noise, I prefer to audition each channel independently with both ears to make sure all the unwanted is gone. Trying to listen to both channels simultaneously after certain processes forces the mind to "multi-task" which could lead to human error - one could miss a small click or such. Reduction of steps to save time could be counter productive in some instances.

One other approach to this for users could be to simply work on one of the stereo channels and have another instance of DC7 doing the other channel.

[Marc Hildebrant]

Comb Filter Settings ?

Group,

With regard to using the Comb Filter in the Paragraphic area...does the Comb Filter on the left channel option select the left channel for you or do you have to manually select the left channel ?

Also, was the idea with the comb filter to seperate some frequencies for the left and some different ones for the right to create the stereo effect ?

Regards,
Marc

[Craig Maier]

Hi,

I have not used that feature in a while, but as I recall there are two sets of presets (for a total of 4) in the paragraphic EQ. Each pair is offset in frequency distribution with respect to the other. I believe that one pair of presets provides a stronger effect than the other, so you can choose to your taste.

To use this feature, you would have to apply the Left channel preset selectively to the left channel and then repeat the process but this time applying the right channel preset to the right channel.

You can use the channel selector buttons to focus in on the appropriate channel.

At least that is my recollection about that function. As I recall, it works quite well. Some folks add a little time offset using the file converter filter when they are done with the paragraphic comb filters in order to improve the effect.

I hope that helps.

Craig