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· http://*****aplaudio*****/
151 Posts
Discussion Starter · #1 ·
Product Brand & Model: Acoustic Power Lab, APL1 equalizer

Condition of all items: new

Total Price: 400 euros:

Shipping Terms: EMS:

Pictures: Acoustic Power Lab :: APL1

Additional info:


I would like to introduce DIY community to new solution which is not so new for professionals. It was at the AES convention in October 2006 when professionals were introduced to it. And now it is widely used for studio monitor tuning to get the most accurate reference possible which allows recording producers and sound engineers to do their job two times faster as before.

Many years ago we had just two „knobs” - LF HF to adjust some device’s sound to our preference – turn knob, listen to result. Turn again; listen again ... and so on.
Then, when electronics became more advanced, we had 10 knobs (1 octave EQ) and we had more space for our creativity – turn and listen.
Then, when electronics became much more advanced, we had 31 knobs (one third octave EQ) and some kind of analyzer with about 31 bands usually. Now are able to see analyzer results, not just listen to them. And we now see, turn, listen... and so on... And we „know” that not every dip that we see on curve is supposed to be equalized.
Everyone who has tried to do such a job knows that it is infinite job ...

Another story is with „power” domain measurements introduced to world in far 2004-2006.
With power domain measurement curves you don’t need to decide which of the dips are qualified to „do not touch” and which are supposed to be corrected. Everything on curve is valid.
This tends to create CAD of EQ – Computer Aided Design of EQ.
We can get highly trustable curve of Sound Power Frequency Response or Sound Power Density Response (for closed environments as car interior).

Attachment 01.png

And by use of CAD of EQ (APL Workshop software) can create EQ filter based on SPFR – SPDR measurement: Acoustic Power Lab :: SPFR

Attachment 02.png

Now tuning process is – measurement, equalizer design, listen to result, add some preference (parametric EQ) listen to result and that is it.
And you can start from such result:

Attachment 03.png

You have full freedom to decide how much to follow measured curve and how much to introduce your own.
But CAD will free you from routine job to recreate curve by use of some parametric EQ and it will free you from decision “do” or „do not touch” and allow you to use your creativity to find your own sound.

In such way APL with a help of Sergey received two gold’s in EMMA 2013 European championship’s „heaviest” classes:

Costs: APL Workshop software -320 euros, and APL1 FIR equalizer unit- 400 euro.
Acoustic Power Lab :: APL1
If you are representing tuning studio you just need one copy of software to install and setup any number of APL1 units.

There is APL EP1 VST plugin available for „Car PC” users for 150 euros.

APL Workshop software demo and APL EP1 VST plugin is available to take a look over APL equalization solution without hardware and for free.

Alexander Martyanov ((his nick is „martyanov” here and he is two times EMMA European champion Sergey’s engineer)) has 4 year experience of APL installations into SQ competitor cars. His build log is available here:

About usage of FIR:


Raimonds Skuruls
Acoustic Power Lab :: Home


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· http://*****aplaudio*****/
151 Posts
Discussion Starter · #11 ·
I need to research this.. Looks very interesting!
Thanks! You can listen to sounding effect of APL in your car by use of APL Workshop and APL EP1 VST demos.

To confirm, this is for the APL1 with dual RCA and optical, or is it for the APL3 that's in the picture?

Secondly, any help on the software for it?

Please let me know, I'm very interested.
The picture of APL3 is used just for illustration - beautiful? : )
APL3 contains 3 PCB boards of APL1.
Please find a picture of APL1 PCB above.
Quick Start Guide may help you.

Thank you,

apl (at)

· http://*****aplaudio*****/
151 Posts
Discussion Starter · #12 ·
Some answers on good questions.

1. Would it be appropriate to place this device before a DSP in the signal chain, i.e. have the attenuation being done before the signal is split by the crossovers?

Yes, it is right (may be only) place for APL1 unit!

2. I intend to use it in a car, what kind of power requirements does it have?

APL1 unit was developed as car unit and therefore has all features as car installation requests:
1) power conditioning to use unit in car noisy environment and in voltage range 7 to 16 Volts (43 Volts, if input capacitor is changed to support 43 V),
2) power management as usually– Remote In, Remote Out.

A power consumption is 3.5 Watts.

3. Does a copy of the software come with the processor, or is the 400 euros just for the unit?

As it is stated in very first post of my topic:
„Costs: APL Workshop software -320 euros, and APL1 FIR equalizer unit- 400 euro.
If you are representing tuning studio you just need one copy of software to install and setup any number of APL1 units.”

Best Regards,

apl (at)

· http://*****aplaudio*****/
151 Posts
Discussion Starter · #14 ·

· http://*****aplaudio*****/
151 Posts
Discussion Starter · #15 ·
You can use VST plagin to hear (listen to) a result of APL correction without using APL1 unit. And this sounding result will be same as with APL1 used.
VST plagin allows running APL processing by software on PC.
You can use VST plagin in almost any audio processing software, DAW or Foobar player.

· Registered
560 Posts
Have being using APL1 for little bit more than one year. Impressions - my best investment in caraudio. Along with fat features of the unit itself, I got a number of target curves for preseting and a selector with 16 positions for these presets. Great device.

· Registered
5,092 Posts
Time for a little review of the APL1. I don't own the actual unit but I have tried out the software. I want to start to thank Raimonds for the support and the demo he supplied me.

The APL software can be considered a form of auto tune. It collects a large amount of samples (I did 250 per side) while sweeping the microphone around the entire listening space and then calculates the acoustic power response. It's a different method than the usual spatial averaging around the "head space". You do one sweep for the left side and one for the right side and then simply import the *.fir file created into either the DSP-unit or the VST-plugin (I used the VST together with foobar2000 on my laptop). I was a bit skeptical at first since the response looked very different from the one I previously measured using the "standard" method.

I should perhaps mention that the system already was tuned when I tried the APL EQ. The staging and tonality was good to begin with but wow... it improved both focus, depth and tonality. It seemed to "remove the room" in a sense, not really but that's my best subjective analysis... it sounded more transparent simply put.

The EQ-curve it created for my left side looked like this:

Quite an amount of complex EQ.

I didn't have the time to actually confirm what it did (in the acoustic domain), but it did work. I must say that this is by far the best sounding form of auto EQ I've ever heard. The only complaint I have is that it killed my lows. Had to bring everything from 20-80Hz up by 10dB or so afterwards, no big deal really. Would be interesting to use it together with a headunit such as the P99 to gain precision EQ without a stand-alone DSP. It could actually be used in CarPC setups, with the VST-plugin.

This is the VST-plugin in action (foobar2000)

I really recommend this product (I assume the DSP-unit works as good as the VST), good stuff indeed. Quite easy to setup and good results on the first try!
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