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TBProAudio ABLM 2
5 5 out of 5, based on 1 Review

The only Loudness Matching tool you need gets better!

24th July 2021

TBProAudio ABLM 2 by Sound-Guy

  • Sound Quality 5 out of 5
  • Ease of use 5 out of 5
  • Features 5 out of 5
  • Bang for buck 5 out of 5
  • Overall: 5
TBProAudio ABLM 2

AB Loudness Match 2 by TBProAudio
AB Loudness Match 2 (ABLM2) is the second version of TBProAudio’s AB Level Matching software, a plug-in that does not add saturation, compression, or EQ to your signals, but measures loudness of an audio track before and after other plug-ins saturate, compress or EQ the track, and then automatically adjusts both loudness and latency to enable comparing before and after processing without loudness bias. Since the original AB Level Match (or any of its multiple updates) was never reviewed in Gearspace, now is the time to describe this excellent, affordable and very flexible tool.

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The Main Event
Not only can ABLM2 match pre and post signal loudness levels, but can let you switch between hearing pre and post for all FX chains in a project that use ABLM2 with a single mouse click (well, plus the Alt key!). ABLM has always had both manual and automatic gain matching, with the loudness measurement capable of using RMS Sum or Average (with user adjustable integration time), EBU R128-2014 Momentary Loudness (400 ms), EBU R128-2014 Short Term Loudness (3 seconds), or the good old fashioned VU metering which is what many audio engineers used for decades. My tests found that EBU R128-2014 Short Term Loudness worked “perfectly” for me, and using separate accurate LUFS meters (Klangfreund Multimeter) to analyze input and output levels, I find the loudness matching from pre to post FX, even with a variety of dynamics plug-ins in the chain, holds within 0.1 dB. Oh, you can also match “maximum peak” levels though I have no idea why anyone would need that since peak level is very unlikely to relate to loudness.

For mixing you simply insert an instance of ABLM2 before all the plug-ins on a track or bus and it will show up as a “Send” module with an assigned Link ID number (starting with Link # 1). The next ABLM2 you insert, at the end of your FX chain, will automatically be a “Receive” module with the same Link ID. You can continue this for each FX chain you wish to analyze, and each pair added will use an incremented link ID. I also used a duplicate track command in Studio One to create multiple tracks with both a Send and Receive unit, but had to manually change the Link numbers which was still faster than inserting a dozen pairs manually. Note that if you do create ABLM2 Send/Receive pairs with the same Link ID, you need to change the Link ID to a unique pair for each FX chain being leveled before running audio – this is not an option!

Resizable GUIs include Send module and Receive module, shown center and right in Pre and Post FX modes.

The top menu of the Receive module has the Link ID, Latency value, PDC button (auto-sets Latency value), RMS integration length window (in milliseconds), metering mode, and an overload protection setting. The large area below the top menu shows a graphic of the signal path thru ABLM2: either directly from Sender to Receiver in Pre FX mode or round the right side in Post FX mode, thru a Drive FX control, a Pre FX loudness display, the FX chain you wish to bypass, a Post FX Gain Difference display, and a display of the Post FX Gain applied to match post FX loudness to pre FX loudness. You switch the signal path by clicking the PRE FX or POST FX button itself and the graphic reminds you which signal path is active.

Several of the windows are inputs, such as the Link ID, the PDC button (Plug-n Delay Compensation) to automatically determine the latency shown in the window left of the button, the RMS integration time window, the metering mode (default is EBU R128-2014 Short Term Loudness), and the over protection setting (on/off and “clip” level).

The Drive FX control window enables increasing or decreasing the signal level sent on to the plug-in chain, which is very handy to observe the effect of different levels on dynamics processors and plug-ins with saturation effects. You can change this while playing sound and ABLM2 will quickly adjust the loudness as needed so you can listen to pre/post effects with loudness bias removed. Note that the Pre FX Loudness window shows the current level driving the FX. Excellent!

The only other control is the Match button which is needed only if you use Manual Match mode (chosen in the lower menu) and the reset button which undoes the matched level in Manual Mode. The other controls at the bottom are the Active switch which turns the current instance of ABLM2 on or off completely, a Delta switch and the Expert GUI/Normal GUI switch in the far right corner. I’ll take a look at the Expert mode soon, but Delta is a superb feature of ABLM2.

As you might guess, Delta changes the output from a loudness compensated output of your FX chain to the difference between the input signal and output of the FX chain. This is a killer feature, worth the price of admission! Fantastic to hear what a single processor or a full FX chain is doing to the audio. Note that the latency compensation must be set to exactly the correct value in order that the input signal contribution is cleanly removed. I found the automatic PDC button to work perfectly in Studio One, my production DAW.

Using Delta mode is enlightening – for example, if you have a dynamics processor like a compressor, you will hear what the compressor is “ducking”, clear of the full audio. And with saturation FX you will hear only the added harmonics. This can be very enlightening – BUT BE WARY if you turn on the Delta mode and push up track or master faders to clearly hear subtle effects. DO NOT turn off Delta until you’ve pulled the faders back down or you may have a very unpleasant experience! Many effects are quite subtle, especially saturation, and you might find yourself boosting the level 20 or 30 dB to hear what is being added. You have been warned.

For Experts Only
Clicking the icon in the very lower right switches to the Expert GUI.

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The Expert GUI shows the same upper menu as the normal GUI, but the rest of this window has a number of different controls and displays. The section below the upper menu is a Reference Level display and control that enables you to shift the input level to a given reference loudness level. It makes this adjustment based on the input signal level present when you click the associated Match button. This is an advanced mode for those who work with calibrated audio systems and want to match levels to a known value. The circular arrow button “undoes” the Match as you might expect.

The next section is for Pre FX and shows two measurements, the current signal level entering the FX chain and the maximum signal level since the circular arrow reset button was last clicked. The area below this section includes a Pre FX Drive control that duplicates the Drive FX control on the main GUI and a Pre/Post button that duplicates the main panel switch. The next section is a Post FX control and measurement panel. The Diff meter shows the loudness difference of Pre and Post-FX signals and the Match button duplicates the Match button of the main GUI. This is used only when the match mode is "Manual". When Match mode is "Auto" the loudness of Post FX is automatically matched to the Pre FX and the Diff meter will read 0.

The Match Mode controls are duplicated from the main GUI next with one additional setting – the Inverse Match Mode: If enabled, Post loudness will not be matched to the current Pre loudness, but both Post and Pre listening modes will be set to match the output loudness of the FX chain. Note that the loudness matching won’t occur until the Post mode is used – after that, clicking the Pre/Post FX button will provide matched loudness at the output level of the FX chain rather than at the Pre FX loudness level. This is the best mode to use if applying loudness correction to multiple tracks or buses in a mixing project because it best maintains the mix balance. And ABLM2 not only enables switching between Pre FX or Post FX loudness – you can also quickly switch to normal FX routing with no loudness matching (the way you actually hear and render a mix) by turning off all instances of ABLM2 using the “Active” button with the Alt key (see below). This is another great feature.

The lowest Expert GUI panel provides controls to store and recall settings of up to four snapshots for FX drive and Post-FX gain so you can quickly test plug-in chains with different drive levels, all loudness matched.

And there is More!
All this is very good, but there are a few more features that should be noted. The Over Protection control in the upper right is used to turn on a clipping circuit to prevent the output from exceeding a set limit. This is an instantaneous peak limiter that will prevent any sample value from exceeding the set limit and may help prevent overloading your ears if you accidentally pop in too much Drive FX, but in general you should use signal levels that will never trigger this over protection system.

There is an additional Match Mode called Gain Staging. This mode does not match loudness of the pre and post FX signal. The pre FX gain and any additional Drive FX gain is simply removed from the audio stream after the FX chain for "pure" gain staging purposes. This is a feature I didn’t find as useful as the various loudness matching functions, but was requested by users and TBProAudio listens to its customers!

There are a number of functions that can be extended using the Alt key: when used with the Active control button Alt turns all instances of ABLM2 in a project on and off, very handy at mixdown. Used with Drive FX, an Alt mouse/drag can increase or decrease gain of incoming signal fed into the FX chain of all ABLM2 instances. And Alt used with the Pre/Post FX switch, or with the Delta switch, will control all instances of ABLM2 at once. This range of control is beyond any other loudness matching system I have seen. And is extremely useful.

Does It Work?
In short, yes, very well. I particularly find the auto matching mode using the EBU R128-2014 Short Term Loudness mode to consistently yield loudness matching that stays within 0.1 dB even with devices such as compressors in the FX chain and with the source level bouncing all over the place. The Delta mode, as I’ve mentioned, enables hearing what an FX chain is actually doing in real time, be it EQ, compression or distortion. And the Drive FX control is very useful to hear how dynamics processors respond at different input levels without loudness bias clouding your judgment. An excellent tool!

Requires Windows 7, or later, OpenGL 2 GFX card/Mac OS X 10.11 or later, Metal GFX card. Plugins provided for Win: 32/64 Bit VST, 32/64 Bit VST3, 32/64 Bit AAX or OS X: 64 Bit VST, 64 Bit VST3, 64 Bit AU, 64 Bit AAX .

I tested ABLM2 using a PC Audio Labs Rok Box with Intel Core i7-4770K CPU @ 3.5 GHz, 16 MB RAM running Windows 7 64 bit. CPU usage was measured using pairs of Send and Receive modules since there needs to be a post for each pre. I found a single pair of instances used a low CPU load of about 0.1% to 0.14%. Latency of ABLM2 itself is zero, but any plug-ins in the FX chain will, of course, add their latency which ABLM2 will correct as needed for Delta mode and A/B comparisons.

An amazing loudness and latency matching tool with some extremely useful features at a very fair price.

Delta mode is especially useful for plug-in evaluations well as hearing the contribution of any processor or FX chain clear of the original input signal.

Inverse mode is excellent for evaluating multiple tracks at once.

Multiple loudness measuring protocols including RMS, VU, and the now standard EBU R128.

Gain Staging mode added by customer demand.

Up to 256 sender/receiver pairs, which seems plenty!

Freely resizable GUI.

Free upgrade for owners of the original AB-Loudness Match

Did I say, a very fair price? €49 or about $US64

Nothing that bothers me.

Attached Thumbnails
TBProAudio ABLM 2-allthree.png   TBProAudio ABLM 2-advanced-1.png   TBProAudio ABLM 2-receive-post.png  
Last edited by Sound-Guy; 26th July 2021 at 04:57 AM..

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