NJU2625 Application Note Acoustical Property Adjustment Procedure Manual New Japan Radio Co., Ltd Version.02
CONTENTS.ABSTRACT...2 2.COMPOSITION OF ACOUSTIC CONTROL...2 3.BLOCK DIAGRAM...5 4.PROCEDURE OF ACOUSTIC CONTROL...6 5.Specify the audio output...8 6.Adjustment of PEQ...9 7.Adjustment of Input Trim...0 8.Adjustment of Bass Enhance...0 9. Adjustment of Elevation...2 0. Adjustment of Surround...3. Adjustment of Phase Shifter...6 2. Other functions...25 CAUTION The products specifications and descriptions listed in this application note are subject to change at anytime without notice. The specifications on this application note are only given for information, without any guarantee as regards either mistakes or omissions. The application circuits in this application note are described only to show representative usages of the product and not intended for the guarantee or permission of any right including the industrial rights. --
.ABSTRACT The NJU2625 is a 24-bit audio DSP Suited to car audio system with functions of surround, elevation, bass enhance and all. The best effect for the seat position can be achieved by adjusting the sound after the car speaker performance is drawn out enough by the PEQ function. This manual explains the adjusting method of the best seat-positioning surround for the customer's set by the function to install in NJU2625. 2.COMPOSITION OF ACOUSTIC CONTROL Figure 2. and Figure 2.2 show the composition of the acoustic control of the car audio system. The setting of the set adjusts the sound by putting into the state without the effect, and using NJU2625 Demo Board and NJU2625 GUI. PC CD Player GPS Voice Signal DC 5V J 5 Lch J 7 Rch LI2 & RI2 U 3 J4 SDO0 SDO J5 Demo I/F Board APC-009-0 Front L/R Rear L/R 4ch AMP Front L Rear L Front R Rear R NJU2625 NJU262x Built-in Board APC-009-0 * Demo I/F Board APC-009-0 doesn't correspond to Subwoofer output (SDO2). Figure 2. Composition of 4ch speaker PC CD Player DC 5V DIN J 9 U SDO0 SDO2 SDO DAPP-004-0 NJU262x Board Front L/R Rear L/R 4ch AMP Front L Rear L Front R Rear R AMP for Subwoofer Subw oofer * Please connect it as shown in figure so that DAPP-004-0 NJU262x Board is opposite to the output of SDO2 and SDO. *2 The GPS Voice Signal input doesn't correspond in DAPP-004-0 NJU262x Board. Subw oofer Figure 2.2 4ch speaker + Composition of Subwoofer -2-
Figure 2.3 DEMO I/F Board and NJU2625 Built-in Board -3-
Figure 2.4 NJU2625 Demo Board -4-
3.BLOCK DIAGRAM The chart of the block of the firmware of NJU2625 is shown in Figure 3., and it explains the adjusting method of the block of the thick line since it the next pages. Moreover, it explains other blocks in the final paragraph. L/R (SDI0) L/R (SDI) NaviVoice Signal (SDI2) 8.Adjustment of Bass Enhance Lch copy to Rch Bass Enhance Input Trim Simulated Stereo * 6.Adjustment of Input Trim * Phase Shifter doesn't operate at the same time as Simulated Stereo. Input Trim 9.Adjustment of Elevation Front Elevation Rear Elevation Front Surround 0.Adjustment of Surround Rear Surround.Adjustment of Phase Shifter Phase * Shifter Time Alignment Phase * Shifter Time Alignment Time Alignment 7.Adjustment of PEQ Surround Mix 7Band PEQ / 5Band PEQ + Tone Control Surround Mix 7Band PEQ / 5Band PEQ + Tone Control Mono Out (L+R)/2 HPF HPF LPF Master Volume/ Channel Trim NaviMix Trim Front L/R (SDO0) Rear L/R (SDO) Subwoofer L/R (SDO2) Figure 3. Firmware block chart -5-
4.PROCEDURE OF ACOUSTIC CONTROL Figure 4. shows the procedure of the acoustic control. Please start the acoustic control after confirming the setting of the set doesn't have the effect. Moreover, the concept of each mode is shown in Figure 4.2. Start 5.Specify the audio output Specify the audio output port according to the speaker composition. 5.Adjustment of PEQ 7. Adjustment of Input Trim 8.Adjustment of Bass Enhance Correct the speaker characteristic including the case. Adjust the input value so that the input is too large and the swerve should not occur. Set Bass Enhance. 9.Adjustment of Elevation Set Elevation. 0.Adjustment of Surround Set Surround..Adjustment of Phase Shifter Set Phase Shifter. Here, each seat position's mode is adjusted. Adjust the following four modes. Driver Mode/ Front Mode/ Rear Mode/ All Mode 2.Adjustment of other functions Set Time Alignment, Simulated Stereo, Lch Copy To Rch, Filter, and GPS Signal Mix. End Figure 4. Procedure of acoustic control -6-
L LS R RS Driver Mode Because the sound of each speaker gathers in the driver seat, the audio image is located forward. L LS R RS Front Mode The audio image spreads forward of the front seat. Therefore, the driver and the front passenger can listen to music naturally. L LS R RS Rear Mode It is a mode to listen to the surround in a rear seat. A Rear Mode can hear the surround only with the rear speaker. L R All Mode It is the best mode for all seats. Music extends to the whole in the car. LS RS Figure 4.2 Concept of each mode -7-
5.Specify the audio output Please suit to the speaker composition, and set the audio output port. Table 5. shows the speaker composition and the audio output. Please refer to the firmware block chart of Figure 3.. Speaker composition Audio output SOURCE 4ch 4.ch 4.2ch SDO0 Front Out L/R L/R L/R SDO Rear Out L/R L/R L/R SDO2 Subwoofer Out Nothing L (Mono) L/R (Mono) Table 5. speaker composition and audio output Figure 5. shows the Other Tab screen of NJU2625 GUI. In 4.ch, 4.2ch case, please move to Other Tab after starting GUI. When the check is put in Subwoofer Mono Out, Subwoofer is output to SDO2. Please turn on Filter (2.4 Refer to Filter) when you use Subwoofer. Figure 5. Other Tabs -8-
6.Adjustment of PEQ This paragraph explains the adjusting method of PEQ. The setting of PEQ can be easily adjusted with not only the manual adjustment but also automatic sound place correction tool to an arbitrary characteristic. Figure 7. shows the frequency response after it adjusts it. The gain in 00Hz and the vicinity of KHz has amplified about 0dB by the frequency response before green adjusts it. To become smooth, do the self adjustment of this characteristic with PEQ automatic sound place correction tool. Please refer to handling manual ("AN2625-APP-PEQ_Ajustment_Mannual-E00.doc") for the usage. setting of PEQ automatic sound place correction tool Adjustable range: 00~20,000Hz (The adjustable range is decided from the speaker reproduction ability) Bands: 5 bands Target characteristic: Flat. Frequency response after adjusting Green: Result of a measurement Red: Adjustment result Blue: Target feature White: PEQ adjusted value Figure 7. Frequency response after adjusting The maximum gain and the frequency of PEQ are displayed in upper right. In this case, it is +.80dB at 0024Hz. Therefore, to avoid the clip warp by the PEQ processing, it is understood to only have to lower the input trimmer at least by -2dB. adjustment result input trimmer :-2dB Band (f0: 00,2Hz Gain:-09.5dB Q: 8.2) Band2 (f0: 0,22Hz Gain:-2.0dB Q: 3.30) Band3 (f0: 02,88Hz Gain:-09.0dB Q: 5.60) Band4 (f0: 04,466Hz Gain:-09.0dB Q: 8.20) Band5 (f0: 0,000Hz Gain:+2.0dB Q: 6.80) Band6 (unused), Band7 (unused) -9-
7.Adjustment of Input Trim Input Trim is a function to make it not distort even if the input level is lowered beforehand, and the level is amplified by the gain of Surround and PEQ. Please lower the input level with Input Trim in consideration of the influence of Surround and PEQ before starting adjusting. 8.Adjustment of Bass Enhance This paragraph explains the bass reinforced method. The bass reinforced function "Bass Enhance" is installed in NJU2625. Bass Enhance increases bass boost level dynamically by input signal level. The speaker characteristic became smooth by adjusting PEQ. Afterwards, the acoustic control is started. PEQ must use the parameter for Front, Rear, and All Mode. It allocates and it explains the Preset number to each seat position as shown in Figure 8.(Note: Please make it to "All Tabs" when adjusting it). Here, Preset5 (All Mode) is used. Please make it to "All Tabs". Figure 8. Bass Enhance Tab (def) : Bypass 2 : Driver Mode 3 : Front Mode 4 : Rear Mode 5 : All Mode 6 : not used 7 : not used 8 : not used 9 : not used 0 : not used Task turns on Bass Enhance and PEQ. Other signal processing function is turned off. Figure 8.2 shows the Bass Enhance Tab screen. First of all, please adjust Gain of Bass Enhance to 0. -0-
Figure 8.2 Bass Enhance Tab Next, cutoff frequency "fc" of the speaker is set. It searches for the part where the attenuation of the low frequency starts from the frequency response of the speaker as shown in Figure 8.3. Because attenuation starts from this speaker from 80Hz, the cutoff frequency is assumed to be 80Hz. Frequency that attenuation starts SPL(dB) fc = 80Hz 0 00 k 0k 00k Frequency(Hz) Figure 8.3 Frequency response of speaker Those who adjust it sit on the Front seat, and adjust the gain while listening to evaluation CD (CD must prepare the one that the bass is clearly heard). Increase Bass Enhance Gain one by one, and look for the compatible value while confirming the effect. Next, Release Time is set. Table 8. shows the relation between Release Time and the effect. Table 8. Relation between Release Time and effect 0.sec <-> 0.5sec <-> 5sec Bass reproduction with intonation Default Bass reproduction that suppresses intonation The Release Time adjustment also does while listening to evaluation CD. It looks for the compatible value by shortening Release Time based on the default value or lengthening it. Please sit on a rear seat at the end, and confirm the effect. --
9. Adjustment of Elevation This paragraph explains the adjusting method of Elevation. The car speaker is usually installed in a low position. Therefore, the sound image is located to a low position. The sound image at a low position can be lifted up to the height of listener's ear by adjusting Elevation. Figure 9. shows the Elevation adjustment screen. Please turn on Bass Enhance, Elevation, and PEQ. Adjust Elevation Gain to 0dB (PEQ must use the parameter for Front, Rear, and All Mode. Use Preset5 (All Mode)). Adjust the Front speaker first. Those who adjust it sit on the reception desk seat. Adjust it while confirming the sound image lifts by increasing Elevation Gain by db. At that time, please do not raise Gain so much. Rear speaker is adjusted just like the adjustment of the front speaker. Those who adjust it must sit on a rear seat. Even if tweeter is installed, this function is effective. In that case, please set gain low. Figure 9. Elevation adjustment screen -2-
0. Adjustment of Surround This paragraph explains the adjusting method of Surround. The surround does two kinds of adjustments. The first adjusts the front surround sitting on the front seat. The second adjusts the rear surround sitting on a rear seat. Preserve the parameter after it adjusts it. Confirmation before surround is adjusted After PEQ, Bass Enhance, and Elevation is adjusted, Surround is adjusted (PEQ must use the parameter for Front, Rear, and All. Preset5 (All Mode) is used here). Please turn off the function of Phase Shifter before the adjustment of Surround starts as shown in Figure 0.. It becomes turning off by removing the check on the check box of each channel. The Surround function and Phase Shifter function or Time Alignment function (Refer to Figure 3. firmware block) operate when Surround is turned on. Figure 0. Phase Shifter Tab when it begins to adjust Surround -3-
Adjustment of Font surround The Front surround is adjusted first. Figure 0.2 Please turn on Surround just like the adjustment screen of Surround. Surround Gain and Surround Ch Trim adjust the front and rear to 0dB. Those who adjust it must sit on the front seat. Vocal is emphasized by increasing Front Center Gain in increments of 0.5dB. Figure 0.2 Adjustment screen of Surround The following of the adjustment of Gain adjust Front Center Ch Trim. Front Center Ch Trim subtracts only the same value as Gain. Ch Trim of Surround adjusts the balance of not the one that a right and left balance is adjusted but the surround signal and non-surround signal. Adjustment of rear surround A rear surround is adjusted. Those who adjust it must sit on a rear seat. Rear Surround Gain is increased by 0.5dB, and the surround is emphasized. Only the same value as Gain subtracts Rear Surround Ch Trim as follows of the Gain adjustment. -4-
Preservation of parameter Preserve all parameters to here. Make the part of a red frame "All Tab". Next, click "Save" button. Select "Preset5". It is completion by selecting OK at the end. Preserve the same parameter as "Preset3 (Front Mode)" and "Preset4 (Rear Mode)" similarly. 2 3 Figure 0.3 Method of preserving all parameters "Preset2 (Driver Mode)" is PEQ parameter for the driver mode. Please input the parameter by manually of adjusted Bass Enhance, Elevation, and Surround when you preserve in Preset2. Start.Write down the parameter of Bass Enhance, Elevation, and Surround. 2.It makes to "All Tabs" and Preset2 is selected. 3.Reflect the parameter written down in each function of GUI. 4.Preserve it in Preset2. End Figure 0.4 Method of preserving parameter of driver mode -5-
. Adjustment of Phase Shifter This paragraph explains the adjusting method of Phase Shifter. The adjustment of each seat position becomes possible by changing the phase by Phase Shifter. Two roles are provided as this function. First is to adjust the phase of each speaker, and to make the sound image located. This is a role of Phase Shifter to adjust the driver mode. Second puts out the extension feeling by giving the phase lag of the right and left speaker output. This is a role of Phase Shifter that does by adjusting a reception desk mode, a rear mode, and all modes. Please put the check in each channel of Phase Shifter before it adjusts it and make the function effective. The function becomes effective by checking the check box. Figure. Phase shifter adjustment screen Please readjust the surround gain after adjusting Phase Shifter of each mode. The parameter of the NJR demonstration car was written here as recommended value. Please use it for the reference of the adjustment. -6-
Figure.2 and Figure.3 show the Phase Shifter adjustment flow chart of each mode. Start.Measure the distance of the driver seat (headrest) and each speaker. 2.Input the distance to GUI. 3.Click "Calculation" button. The frequency and the switch of Phase Shifter are renewed 4.Fine-tune it. NO OK? YES End Figure.2 Phase Shifter adjustment flow chart of driver mode Start.The frequency is set according to the example of the Phase Shifter adjusting method of each mode. 2.Surround Gain is readjusted according to each mode. 3.The frequency is set again according to the example of the Phase Shifter adjusting method of each mode. NO OK? YES End Figure.3 Phase Shifter adjustment flow chart of Front mode / Rear mode / All mode -7-
. Driver mode Phase Shifter adjustment Condition Task: Bass Enhance, Elevation, Surround, PEQ : ON; Preset: Driver Mode (Here, use Preset2); Sit on the driver seat and adjust. Figure.3 Task setting of driver mode. Measure the distance from the center of the headrest of the driver seat to each speaker as shown in Figure.4. L R L R LS RS LS RS Measure the center of the headrest of the driver seat and the distance of each speaker. L R L R LS RS LS RS Figure.4 Measurement image of driver seat and each speaker -8-
2.Input the distance to a red frame of NJU2625 GUI (Phase Shifter Tab) as shown in Figure.5. Figure.5 Distance input screen 3.Next, click the Calculation button of a blue frame of Figure.5. Then, the Phase Shifter switch of each channel and the update of the frequency are completed as shown in Figure.6. Renewal of switch of each Phase Shifter The channel away most from the driver seat is turned off by the automatic operation Update of frequency of each Phase Shifter GUI calculates by the automatic operation Figure.6 NJU2625 Phase Shifter screen after adjustment -9-
4.It explains fine-tuning. When the sound image is not forward but is located right and left after Phase Shifter is adjusted, it fine-tunes it with the manual. Do not change the parameter of the channel that turns off a high frequency or the function in front Phase Shifter. Adjust it based on the frequency of the channel of the other low frequency. Table. shows the method of fine-tuning Phase Shifter. When the sound image is located to the channel side of the high frequency. Raise the frequency on the channel side of the low frequency. Oppositely, lower the frequency when the sound image is located to the channel side of the low frequency. Figure.7 shows the example of the method of fine-tuning Phase Shifter. Rear Phase Shifter is not fine-tuned. Table. Method of fine-tuning Phase Lower the frequency Frequency Raise the frequency Sound image moves a high frequency or function to the channel of turning off. Sound image The sound image moves to the channel being operated now. Fix the frequency of Lch because the function is turning off. Sound image The sound image moves to the Lch side when the frequency of Rch is lowered. The sound image moves to the Rch side when the frequency of Rch is raised. Figure.7 Example of fine-tuning Phase Shifter The sound image was located forward in doing the above-mentioned operation. However, raise Front Center Gain when an effect of lift up and a plain feeling are insufficient. Moreover, do a right and left volume balance with Ch Trim. recommended value Surround Front Center Gain = +6.0dB; Front Center Ch Trim = -6.0dB; Rear Surround Gain = +6.0dB; Rear Surround Ch Trim = -6.0dB; -20-
.2 Adjustment of Front mode Condition Task: Bass Enhance, Elevation, Surround, PEQ : ON; Preset: Front Mode (Use Preset3); Sit on the front seat and adjust. Figure.8 Task setting of front mode The phase lag is put out by changing the frequency of Phase Shifter of each channel. Table.2 shows the example of the adjusting method. The frequency of one of channels is fixed by 4kHz, and it changes a frequency so that the phase lag of khz may change with the other channel by ten degrees. And, it looks for the parameter so that the audio image extends between the driver's seat and the passenger's seat. Table.2 Example of Front Mode adjusting method Front Mode Parameter Phase Difference Front Lch Front Rch Rear Lch Rear Rch 330 00 Hz 4 khz 4 khz 00 Hz 320 220 Hz 4 khz 4 khz 220 Hz 30 320 Hz 4 khz 4 khz 320 Hz 300 40 Hz 4 khz 4 khz 40 Hz 290 490 Hz 4 khz 4 khz 490 Hz 280 550 Hz 4 khz 4 khz 550 Hz 270 600 Hz 4 khz 4 khz 600 Hz 260 650 Hz 4 khz 4 khz 650 Hz 250 700 Hz 4 khz 4 khz 700 Hz 240 740 Hz 4 khz 4 khz 740 Hz Recommended value The frequency is changed by operating the slider. Figure.9 Method of setting frequency of Front Mode -2-
It explains the method of fine-tuning Surround of Front Mode. To increase a plain feeling of the surround further, the value of Rear Surround Gain is raised, and the value of Rear Surround Ch Trim is lowered. Then, the surround element is emphasized more and output from rear speaker. recommended value Surround Front Center Gain = +6.0dB; Front Center Ch Trim = -6.0dB; Rear Surround Gain = +9.0dB; Rear Surround Ch Trim = -.0dB; Phase Shifter Front Lch = 220Hz; Front Rch = 4kHz; Rear Lch = 4kHz; Rear Rch = 220Hz;.3 Adjustment of Rear mode Condition Task: Bass Enhance, Elevation, Surround, Surround Mix, PEQ : ON; Preset: Rear Mode (Use Preset4); Sit on the rear seat and adjust. The example of the adjusting method of Rear Mode copies the Phase Shifter frequency of Front Lch onto Rear Lch as shown in Table.3. Similarly, the parameter of Front Rch is copied onto Rear Rch. You add a reception desk output and a rear output by using the Surround Mix function. The parameter of Surround Mix recommends Front Ratio 0.5 and Rear Ratio 0.7 (Figure. Refer to the Surround Mix adjustment screen). In addition, the value of Front Ch Trim must be half (-6dB). Table.3 Example of Rear Mode adjusting method Rear Mode Parameter Phase Difference Front Lch Front Rch Rear Lch Rear Rch 330 4 khz 00 Hz 4 khz 00 Hz 320 4 khz 220 Hz 4 khz 220 Hz 30 4 khz 320 Hz 4 khz 320 Hz 300 4 khz 40 Hz 4 khz 40 Hz 290 4 khz 490 Hz 4 khz 490 Hz 280 4 khz 550 Hz 4 khz 550 Hz 270 4 khz 600 Hz 4 khz 600 Hz 260 4 khz 650 Hz 4 khz 650 Hz 250 4 khz 700 Hz 4 khz 700 Hz 240 4 khz 740 Hz 4 khz 740 Hz Recommended value -22-
You make the frequency of Lch of Front and Rear the same. Figure.0 Method of setting frequency of Rear Mode You make the frequency of Rch of Front and Rear the same. recommended value Surround Front Center Gain = +6.5dB; Front Center Ch Trim = -2.0dB; Rear Surround Gain = +5.5dB; Rear Surround Ch Trim = -6.0dB; Surround Mix Front Ratio = 0.5; Rear Ratio = 0.7; Phase Shifter Front Lch = 320Hz; Front Rch = 4kHz; Rear Lch = 320Hz; Rear Rch = 4kHz; Ch Trim Front Ch Trim Lch/Rch = -6dB; Rear Ch Trim Lch/Rch = 0dB; Subwoofer Trim Lch/Rch = 0dB; Figure. Surround Mix adjustment screen.3 Adjustment of All mode Condition Task: Bass Enhance, Elevation, Surround, PEQ : ON; Preset: All Mode (Use Preset5); Sit on the front seat and adjust. Next, sit on a rear seat and adjust. Adjust All mode while repeating this. -23-
The example of the adjusting method of All Mode adjusts Front Center Gain and Rear Surround Gain to the same value. In addition, you change the phase as much as Front Mode by ten degrees and look for the parameter to which the sound image spreads from the center of the space in the car. Table.4 Example of All Mode adjusting method All Mode Parameter Phase Difference Front Lch Front Rch Rear Lch Rear Rch 330 00 Hz 4 khz 4 khz 00 Hz 320 220 Hz 4 khz 4 khz 220 Hz 30 320 Hz 4 khz 4 khz 320 Hz 300 40 Hz 4 khz 4 khz 40 Hz 290 490 Hz 4 khz 4 khz 490 Hz 280 550 Hz 4 khz 4 khz 550 Hz 270 600 Hz 4 khz 4 khz 600 Hz 260 650 Hz 4 khz 4 khz 650 Hz 250 700 Hz 4 khz 4 khz 700 Hz 240 740 Hz 4 khz 4 khz 740 Hz Recommended value The frequency is changed by operating the slider. Figure.2 Method of setting frequency of All Mode recommended value Surround Front Center Gain = +5.5dB; Front Center Ch Trim = -5.0dB; Rear Surround Gain = +5.5dB; Rear Surround Ch Trim = -5.0dB; Phase Shifter Front Lch = 320Hz; Front Rch = 4kHz; Rear Lch = 4kHz; Rear Rch = 320Hz; -24-
2. Other functions There are Time Alignment, Simulated Stereo, Lch Copy To Rch, GPS Signal Mix, and Filter in NJU2625 as other functions. This paragraph explains other functions. 2. Time Alignment The sound image comes to remain locating forward even if you turned off (Adjust Front Center Gain and Rear Surround Gain to 0dB and become turning off.) Surround by adjusting Time Alignment at the driver mode. The driver can turn Surround on and off without the sense of incompatibility. The range enclosed in a red line in Figure 2. becomes Time Alignment adjustment part. Figure 2. Time Alignment Tab The adjusting method is based on the speaker away most from the driver seat as shown in Figure 2.2. And, calculate the difference of the distance with other speakers. The calculating formula of Figure 2.2 is recorded in the following. (Front Lch) (Front Rch) (Front Rch Delay Distance) (Delay Sample) 300mm - 830mm 468mm 60 Sample (Front Lch) (Rear Lch) (Rear Lch Delay Distance) 300mm - 50mm 48mm 9 Sample (Front Lch) (Rear Rch) (Rear Rch Delay Distance) 300mm - 570mm 733mm 94 Sample Adjust the surround gain to 0dB with the front and rear at the end. And, select Time Alignment of a red frame of Figure 2.3. -25-
The delay distance and delay time by Delay Sample are displayed. Figure 2.2 Time Alignment adjusting method_ Please adjust Front Center Gain, Rear Surround Gain, Front Center Ch Trim, and Rear Surround Ch Trim to 0dB. Figure 2.3 Time Alignment adjusting method_2-26-
2.2 Simulated Stereo It explains the Simulated Stereo function. This function makes the mono-sound source a pseudo stereo sound source. Therefore, turn on the Simulated Stereo function in case the mono-sound source. Moreover, this function cannot use the Phase Shifter function together. Select Time Alignment when you use Simulated Stereo. (When Simulated Stereo is turned on, NJU2625 GUI automatically selects Time Alignment.) 2.3 Lch Copy To Rch It explains the Lch Copy To Rch function. This function is used when there is a signal only on the Lch side. It is prevented from not being output from Rch by the signal of Lch being copied onto Rch. 2.4 Filter It explains the Filter function. When 4ch + subwoofer composition of 4.ch or 4.2ch. It uses as a crossover filter of the subwoofer and front speaker and rear speaker. A reception desk output and a rear output are High Pass Filter (The cutoff slope is -6dB/oct). The Subwoofer output is Low Pass Filter (The cutoff slope is -6dB/oct). GPS Output Select Filter Switch Cut Off Frequency Figure 2.4 Other Tabs 2.5 GPS Signal Mix It explains the GPS Signal Mix function. This function can do Mix the GPS Signal input of DSP at the Front output or the Rear output. The output destination is selected with GPS Output Select of a red frame in Figure 2.4. GPS Mix Trim can output only the voice of GPS by making music a mute for another processing with Master Volume. (Refer to Figure 3. firmware block.) -27-