Recall Sheets #1

Hi there!

I recently started to design some recall sheets for hardware I use and that doesn’t come with pre-made sheets. As I guess some of you might also be interested in these, I will continually provide new recall sheets as I design them.

Here are the first two for a Stam Audio SA400 as well as a ART Pro Channel (v1):

stam-sa4000-recall

Stam Audio SA4000

art-pro-channel-recall

ART Pro Channel

You can also download .png and .svg files of these designs in order to adapt them to your specific needs:

Stam Audio SA4000 – png
Stam Audio SA4000 – svg
ART Pro Channel – png
ART Pro Channel – svg

If you find these files useful I’d like to encourage you to leave a comment below and help spread the word about this blog.

Thanks and all the best,
Markus

Stam Audio SA4000

Hi all!

I recently received my Stam Audio SA4000, a replica of the famous SSL Stereo Bus Compressor.

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In order to get a feeling for what this comp can do I took my recent mix of Jokers, Jacks & Kings song Sea of Leaves and used the SA4000 on the main bus instead of the Waves API2500 that I originally used in that mix. Furthermore I did a comparison with some plugin emulations of the SSL Bus Comp, namely the Acustica Audio Sandbus4 as well as the Waves G-Buss Comp. All settings have been carefully matched and I specifically ensured that there are no differences in volume across the different mixes.

You can clearly hear that the SA4000 does something to the mix that probably only hardware can, although, one has to admit that the Acustica Audio Sandbus4 comes quite close to the hardware. It just lacks a little bit of that additional 3D quality.

Stam Audio SA4000 (Ratio 4:1, Attack: 30 ms, Release: 0.1s, GR: 2-3dB)
https://www.dropbox.com/s/qwbt95xoopqoiid/Sea_of_Leaves_SA4000_Release-01.mp3?dl=0

Acustica Audio Sandbus4 (Ratio 4:1, Attack: 30 ms, Release: 0.1s, GR: 2-3dB)
https://dl.dropboxusercontent.com/u/79766823/Sea_of_Leaves_SANDBUS4_Release-01.mp3

Waves G-Buss Comp (Ratio 4:1, Attack: 30 ms, Release: 0.1s, GR: 2-3dB)
https://dl.dropboxusercontent.com/u/79766823/Sea_of_Leaves_Waves_G-Comp_Release-01.mp3

Stam Audio SA4000 (Ratio 4:1, Attack: 30 ms, Release: Auto, GR: 2-3dB)
https://dl.dropboxusercontent.com/u/79766823/Sea_of_Leaves_SA4000_Release-Auto.mp3

Acustica Audio Sandbus4 (Ratio 4:1, Attack: 30 ms, Release: Auto, GR: 2-3dB)
https://dl.dropboxusercontent.com/u/79766823/Sea_of_Leaves_SANDBUS4_Release-Auto.mp3

Waves G-Buss Comp (Ratio 4:1, Attack: 30 ms, Release: Auto, GR: 2-3dB)
https://dl.dropboxusercontent.com/u/79766823/Sea_of_Leaves_Waves_G-Comp_Release-Auto.mp3

If you are interested in a more in-depth discussion with further examples (in german) you can head over to the recording.de thread.

Meanwhile I will do some more comparisons of the SA4000 on different sources and will post further examples in an upcoming blog post.

All the best,
Markus

P.S.: Here are the links to Stam Audio and the used plugins.

Stam Audio SA4000
Acustica Audio Sand
Waves G-Master Buss Compressor

Jokers, Jacks and Kings – Sea of Leaves

Hi all!

I did a practice mix recently that I really enjoyed and wanted to share with you.

The song is called Sea of Leaves by south-London band Jokers, Jacks and Kings and it is a great composition if you ask me. For those of you who want to try and mix the song yourself the multitracks can be found in Mike Senior’s Multitrack Library.

I’d be very interested in your thoughts and comments. And if you happen to mix this song yourself, please drop me a line with a link so we can discuss it.

All the Best,
Markus

Counter The Eulogy – Transitions

Hi all!

I very much apologize for leaving this blog out in the cold for so long. However, there was a good reason for that.

I was very busy over the last year executing the first complete production here at Orthogonal Records. Now that it has been officially released I wanted to let you know about it. We are talking about the debut album of my Alternative Rock band Counter The Eulogy, entitled Transitions.

It is available for download and streaming at all major vendors and you can pre-order it as CD with DigiPac directly from the band (website above).

To give you an idea of how the finished CD will look like, here are some mockups of the DigiPac showing the artwork as well as the front cover image.

We are very much looking forward for your thoughts about it and would highly appreciate your support by purchasing your copy and following our social media activities.

Here are some links for you:
iTunes/Apple Music
Google Play
Spotify
Microsoft Groove
Amazon

We really hope that you like this new release that we worked our socks off to be as good as it could possibly get and thank you for your interest.

All the best,
Markus

P.S.: I will now also resume my series on building a proper control room and plan to come up with additional studio stuff and reports in this blog. So please stay tuned.

Building a proper control room – mounting fabric and difference measurements

Hi again! Welcome back to the fourth article in this series.

Today it’s time to see what difference it makes if two layers of cotton fabric are mounted above the construction that we already measured last time. Since that task is quiet simple, today’s article will be relatively short.
The primary reason we want to put some fabric on top of the bass trap construction is a purely aesthetical one. We simply do not want the vapour retarder and it’s imprint to be seen trough the slits in the wooden board construction that is planned on top of the bass traps. Since we used a cotton fabric that is relatively thin and the imprint of the vapour retarder would still shine through a single layer, we used two layers of fabric.

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Two layers of cotton fabric mounted on top of the construction – front wall.

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Two layers of cotton fabric mounted on top of the construction – rear left corner.

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Two layers of cotton fabric mounted on top of the construction – ceiling.

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Two layers of cotton fabric mounted on top of the construction – ceiling.

A side effect of this approach is, that the fabric also alters the acoustic response of the room, as does every change that you make to the room. Let’s see how strong the effect is. Looking at the frequency response curve we can only spot slight differences. That’s perfectly reasonable since one shouldn’t expect a drastic change in frequency response by just two layers of thin cotton fabric.

Stoff_SPL

Frequency response after the cotton fabric has been mounted; speakers and microphone at best position – 1/48 octave smoothing, both speakers measured simultaneously (blue curve) as well as individually (red and green curves).

The EDT curve, as well as the waterfall and spectrogram plot, however, show that the fabric changed the decay time of the high frequencies. Everything above about 1.5 kHz is now damped considerably more than without cotton fabric. This is exactly the effect that we already mentioned in the last article. Frequencies in this range had obviously been reflected by the relatively thick vapour retarder. Nevertheless, the two layers of cotton seem to be thick enough to dampen those frequencies some more. This in turn helps to bring down the decay time to a maximum of about 400ms (0.4s) throughout the entire frequency spectrum.

Stoff_EDT

Early Decay Time (EDT) curve after fabric has been mounted.

Stoff_waterfall

Waterfall plot after the fabric has been mounted on top of the bass traps.

Stoff_Spectrogramm

Spectrogram plot of the room with installed cotton fabric.

Changes in the ETC are actually not worth mentioning since we still haven’t done anything specific to the “real” early reflections up to now,e.g., a treatment of the side-walls.

Stoff_ETC

ETC plot.

In the course of treating early reflections via side and cloud absorbers and due to the fact that a big couch for future clients is planned at the back end of the room, we need to think about not over-damping the room in the high frequency range. This will be achieved by mounting wooden boards across the construction that we built so far. These boards will have a certain width and will be mounted with a certain slit between each other. These two dimension then define a limiting frequency. All frequencies below this limiting frequency are diffracted into the absorber construction, whereas all frequencies above the limit are reflected by the wooden boards.

More on this construction and it’s effect on the room response will be the topic of next weeks article.

All the best,
Markus

Building a proper control room – construction of bass traps

Hi and welcome back to the third article in this series.
After we discussed the prerequisites, came up with an acoustic design concept and did the first measurement of the naked room, it’s now time to actually start construction works.

Along the line of our acoustic design concept we will start with building a wooden frame for the bass absorbers at the wall-ceiling junction. Remember, we want these to be 40cm high and one board of mineral wool deep, i.e., about 70cm when allowing some additional space for the frame. The construction of the frame is relatively simple. One slat is screwed to the ceiling and one to the side wall. These two slats are now joined to form a cuboid. After filling one part of a frame with mineral wool it is reinforced at the bottom and sides with further slats. These also support the mineral wool boards.

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Construction of the frame for the mineral wool bass traps at the wall ceiling junction.

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Bass absorbers at the wall-ceiling junction getting their filling – rear right corner.

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Bass absorbers at the wall-ceiling junction getting their filling – front right corner.

After the wall-ceiling junction has been finished the remaining ceiling is lowered accordingly and likewise filled with 30cm of mineral wool.

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Entire ceiling lowered using a wooden frame that’s filled with mineral wool.

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Entire ceiling lowered using a wooden frame that’s filled with mineral wool.

The last step is to build the front corner traps as described in the design concept article. To achieve this each mineral board is cut into two halves. Each of these halves is then cut into two triangles of the same size which are finally stapled on top of each other. Finally the corner traps are supported by another frame of wooden slats.

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The front right corner trap as well as the entire ceiling filled with mineral wool.

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The front left corner trap as well as the entire ceiling filled with mineral wool.

In order to prevent damage from moisture the entire construction has to be thoroughly sealed using proper vapour retarder. If the construction is mounted to a concrete wall/ceiling it is best to use a humidity adaptive vapour retarder that allows the construction to desiccate back into the room when necessary. Furthermore, the vapour retarder provides a barrier for the mineral wool fibres. Please note, that it is of utmost importance to mount the vapour retarder properly, i.e., using the system-specific adhesive tape and glue as directed by the manufacturer. Failure to do so can lead to severe problems with moisture and mouldiness.

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The entire construction is thoroughly sealed with vapour retarder.

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The entire construction is thoroughly sealed with vapour retarder.

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The entire construction is thoroughly sealed with vapour retarder.

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The entire construction is thoroughly sealed with vapour retarder.

All right, now it’s time for the next measurement. Using the exact same position as for the first measurement the result looks like the following. We will keep the order of graphs the same in all articles. First is the frequency response, which already improved quite a lot, e.g., the peak that we had at 40Hz has been lowered by 10dB and the region from 100 to 500 Hz has been smoothed out dramatically. Of course there is still comb-filtering and one can also identify the slightly asymmetric response of the two speakers due to the room-asymmetry that we mentioned in the last article.

Dampfbremse_SPL

Frequency response with installed bass traps with speakers and microphone at best position – 1/48 octave smoothing, both speakers measured simultaneously (blue curve) as well as individually (red and green curves).

Even more impressive is the change in the EDT curve. Please note that the curve has been re-scaled in comparison to the first measurement. While we had an early decay time of about 3.6s (3600ms) in the 100 – 200Hz region and more than 1s nearly everywhere else in the frequency spectrum during the first measurement, it’s now down to about 0.6s (600ms) for the worst region, i.e., the highest frequencies. The region of interest for now is the one up to 500Hz which is already looking very good apart from the lowest bass regions.

Dampfbremse_EDT

Early Decay Time (EDT) curve.

This change in the EDT curve is of course also reflected in the waterfall plot. Here, you can also see the dramatic improvement in the bass area. One point that can also be noticed is the impact of the vapour retarder. Normally, one would expect the high frequencies to be damped quiet easily by the bass traps. However, the vapour retarder is a relatively thick film (or foil if you like) and thus obviously reflects frequencies above about 1.5kHz. We will see this statement to be confirmed by the measurements done after mounting two layers of cotton fabric above the vapour retarder.

Dampfbremse_waterfall

Waterfall plot after the bass traps have been installed.

Of course, the spectrogram shows the same facts as the waterfall diagram, as already pointed out in the last article.

Dampfbremse_Spectrogramm

Spectrogram plot of the room with installed bass traps.

The last plot, the ETC (Energy Time Curve) is not that useful to look at yet, since we haven’t done anything to eliminate early reflections up to now. Nevertheless, we will show it here for the sake of completeness.

Dampfbremse_ETC

ETC plot.

As you hopefully see, the construction of bass traps already helped a lot in the achievement of a proper control room acoustics. Keep in mind that in the bass region “the more the merrier” is virtually always true.

Next time we will see how mounting two layers of fabric alters the measurements and talk about what we can do to prevent overdamping in the high frequency region.

I hope you are enjoying this series and am looking forward to meeting you in the next article.

All the best,
Markus

Building a proper control room – first measurement and analysis

Hi all! I hope you are doing fine. I’m finally back with the third article in this series.

After discussing the prerequisites and the acoustic design concept in the first two articles of this series, we will now have a look at the first measurements of the naked room that finally became our new control room. As you can see from the following pictures, the room is a typical cellar room.

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Front right corner of the naked room.

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Right wall of naked room.

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Left and rear wall of naked room.

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Front left corner of naked room.

It’s immediately obvious from the pictures that symmetry, one crucial part of room acoustics, might be a problem in this room. On the one hand, there is the chimney and the door in the rear left corner as well as the ventilation pipe at the left wall. On the other hand, there is a naked rear right corner and right side wall. We will see what these things do to the frequency responses of left and right speakers respectively.
The first crucial step is to determine the best starting position for the speakers. This is done by performing several measurements starting at a reasonable position and successively varying the position of speakers and microphone for each measurement. Finally, the measurement that gives the flattest frequency response is used as the best starting position. In small rooms it has been shown several times, i.e., often measured in the recording.de room acoustics forums that the speakers are best positioned directly at the front wall, i.e., with the smallest possible gap to the front wall. This is due to the speaker boundary interference response (effect) (SBIR/E) producing dips in the bass frequency spectrum due to destructive interference of the direct sound from the speakers with it’s reflections from the front wall (the wall behind the speakers). If the speakers are positioned close to the front wall the dip in the spectrum is moved to lower frequencies which in turn can work against room modes, resulting in a better overall frequency response. Be aware though that this is only beneficial in small rooms where it also helps to maximize the distance between listening position and rear wall. By the way, the SBIR effect is also the major reason why main monitors are often flush mounted in pro studios.
Nevertheless, the best position always has to be determined by measurements since no two rooms will behave the same and therefore an acurate prediction of the best position is quite difficult. You can see pictures of the best position as well as it’s frequency response in our room in the following pictures.

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Best position of speakers and measurement microphone.

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Best position of speakers and measurement microphone from below.

Erstmessung_SPL_no_smoothing

Frequency response of the naked room with speakers and microphone at best position – no smoothing, both speakers measured simultaneously.

Erstmessung_SPL

Frequency response of the naked room with speakers and microphone at best position – 1/48 octave smoothing, both speakers measured simultaneously (blue curve) as well as individually (magenta and purple curves).

As you can see, there are massive peaks and dips in the frequency response. These are due to room reflections superimposed on the direct sound and thus altering the perceived frequency response via comb filtering. In the course of treating the room to achieve our target values (RT60 etc.) we will see that the frequency response will automatically start to flatten due to the elimination of room modes and reflections. At the moment we have a difference of over 40db between the highest peak and the lowest dip, which is quite horrible.

Erstmessung_EDT

Early Decay Time (EDT) curve.

The early decay time (EDT) curve gives a first impression of how disastrous the reverberation of the room is. This is the curve that corresponds to the RT60 value, we calculated last time using Bob Gold’s calculator. (We won’t call it RT60 here, because that terminology is only valid if we had a completely diffuse sound field.) Remember, that our target value is between 200ms and 400ms throughout the whole audible spectrum. At the moment the curve jumps between approx. 3600ms and 900ms, with the worst area between 100Hz and 200Hz. This resembles the modal problems that Bob Gold’s calculator computed, with the most massive room modes up to 200Hz.
These problems are even more obvious in the so-called waterfall diagram. In that 3D graph the frequency is plotted logarithmically on the horizontal axis, the level in dB on the vertical axis and decay time in ms on the axis perpendicular to those two. If you trim it to show a level difference of -60dB from the highest peak, then you have another depiction of the early decay time. In a proper control room all frequencies should have been attenuated by 60dB within 200-400ms. If we take a mid-range value of 300ms this means nothing should be cut off in the first waterfall plot. This obviously isn’t the case with our naked room.

Erstmessung_waterfall

Waterfall diagram with meaningful settings.

To further elucidate the problem I show you a waterfall plot with a decay time setting of 2000ms (2s). Even here we still have cut off parts in the modal region between 100-200Hz. So there clearly is a massive problem in this region.

Erstmessung_waterfall_2000ms

Waterfall plot with increased decay time (2s).

The spectral plot shown in the next picture is another alternate view on the rooms decay time, showing the frequency on the horizontal and the decay time on the vertical axis as well as the level coded as different colors.

Erstmessung_Spectrogramm

Spectral plot

The last important plot is the Energy Time Curve (ETC) providing information on the early reflections and their temporal location, i.e. the time difference between direct sound and a given reflection. This will allow us to find the points of reflection, e.g., side-walls, ceiling, etc.

Erstmessung_ETC

Energy Time Curve (ETC)

An explanation of the ETC of an untreated room like ours and a perfect example for a proper ETC can be found in the next picture. Our target is to achieve an ETC that is as close to the latter picture as possible.

etc_schematic

The areas of the ETC for an untreated room (above) and for a properly treated room (below).

As you see, an untreated room has massive problems that have to be cured in order to use it as a proper control room. Otherwise, you would never be able to make objective decisions for your recordings or mixes, resulting in mixes that don’t translate to other systems and places.
I hope you will be part of this journey of transforming the horrible room we just discussed into a proper control room where making objective decisions is no longer a whishful dream but rather an actual fact.

More on that next week, when we will start to build bass traps and measure their impact on the rooms response.

Best regards and keep the music coming,
Markus