Pioneer FH-X731BT Car Receiver for Home

I’m not really into car audio but I came across this while surfing the net. Apart from being able to play with a multitude of sources, what caught my eye were the Crossover and Time Alignment features. That got me thinking. What if, instead of installing it in a car, adapt it for home use. For a mere $105 at Amazon, it would be quite a bargain. If it’s good enough, it’s a affordable entry to a High quality, Active Tri-amping System. Let’s take a closer look at what it’s all about.
 

Crossover in Network Mode

The CROSSOVER has two modes, STANDARD and NETWORK. I am testing the Pioneer FH-X731BT in the NETWORK mode because with this selection, I’m able to set the crossover for the Tweeter, Midrange and Woofer, essentially a 3-way system. The following are the settings:

HIGH HPF – This stands for Tweeter High Pass Filter. You are presented with a range of spot frequencies starting from 1.25kHz to 12.5kHz. After you select the frequency, you then decide at what slope. You have the option of 6dB, 12dB, 18dB or 24dB.

MID LPF – This stands for Midrange Low Pass Filter. Selection is the same as HIGH because this is where the Midrange hands over to the Tweeter.

MID HPF – This stands for Midrange Low Pass Filter. This is the other end of the Midrange, where it stops and the Woofer comes in. Spot Frequencies are from 25Hz to 250Hz. Filter slopes are 12dB, 18dB, 24dB and 36dB.

SUBWOOFER – The woofer is displayed as SUBWOOFER because the emphasis is on low frequencies. Selections are the same as MID HPF so you cannot cross a woofer to the midrange higher than 250Hz. SUBWOOFER is also in MONO.

Now, let’s see how this work out in practice. System configuration is Active Tri-Amping. The Pioneer’s internal amplifiers are not used. Instead, signals are taken from the back panel’s LINE OUTS to external 400 Watts power amplifiers.

Test speaker is the Super-Micro, a tiny satellite comprising of Tang Band W3-1364SA 3″ Full Range driver and Peerless BC25SC08 for tweeter. Subwoofer is a 10″ Aluminum Cone Dayton DA270.

HIGH (HPF)

First test was to see how the crossover slopes are.

Fig 1 shows the BC25 response when crossed at 4kHz at 6dB (Blue), 12dB (Black), 18dB (Brown) and 24dB (Red).

Impressive, so far. No drift in the corner frequency when the filter slope changes.

bc25_4k_6db_24db_crop

(Fig 1) Frequency Response of Peerless BC25SC08 (No Smoothing, mic at 0.5 meters tweeter axis, 5 msec gating)

w3_bc25_hp_lp_4k_24db_05meter

(Fig 2) W3-1364SA and BC25SC08 Response (No Smoothing, mic at 0.5 meters tweeter axis, 5 msec gating)

In Fig 2, the W3-1364 Low Pass is at 4Khz (24dB) and High Pass at 250Hz (24dB). The tweeter, the BC25SC08, High Pass is at 4kHz (24dB). Disregard readings below 500Hz as my room is interfering with the measurement.

So far, so good. The midrange and tweeter are crossing cleanly at 4kHz.

full_w3_bc25_4k_24db_05meter

(Fig 3) Summed Response of W3-1364 and BC25SC08 (No Smoothing, mic at 0.5 meters tweeter axis, 5 msec gating)

Summed Response

Fig 3 shows the Frequency Response of the Super-Micro. Since the W3 Low Pass is at 24dB and the BC25 High Pass is also at 24dB, the tweeter is wired in normal polarity (ie Red to +) for proper summing.

distortion

(Fig 4) Super-Micro Distortion

Distortion

Distortion is quite low, generally at 50dB below the fundamental. Interestingly, it revealed a rather high peak at 8kHz. This is quite unexpected. I’m not sure whether it’s from the Pioneer itself or switching artifacts from my switched mode power supply which is right beside the unit.

Further tests confirmed that it came from the tweeter’s High Pass Filter Network and not from the midrange. Fortunately, it’s 2nd harmonic, so should not present any issues. This was verified on musical playback.

3-way

(Fig 5) 3-way Drivers Acoustic Center Offsets

Time Alignment

The Time Alignment feature in this Pioneer is actually designed  for in-car use, not for home. This is what happens when one is seated in a car.

If you’re the driver, for example, you’ll hear the speaker nearest to you first, likely the one in your door. Sound coming out from the speaker that’s farthest away, like a subwoofer in the trunk, will reach you last. This creates an unrealistic sound stage. If the sound from the speaker nearest to you is delayed so that it reaches the you the same time as the subwoofer, the effect is much more realistic. In a nutshell, this is what the Time Alignment feature does. It allows you to adjust the timing of individual speakers in the car so that all of them reach you at the same time.

For home use, it’s entirely different. There’s no necessity to “delay” either the Left or Right Speaker because the listener is seated right in the middle. Being equidistant, both sounds from the Left and Right Speakers will reach the listener at the same time. So, one may ask, how is Time Alignment useful in the home?

Let’s take a look at Fig 5 above. Even though all the drivers are mounted on the same front panel, sound from the tweeter, midrange and woofer don’t reach the listener at the same time. That’s because the “Acoustic Center” of the tweeter is nearer to the listener than the rest. This is a physical defect that exist in all multi-way speakers. The highs, the mids and the lows all reach the listener at different times.

If we can delay the tweeter and midrange so that both of them arrive together at the same time as the woofer at the listener’s position, then at least, the sound would be closer to originating from a single source.

Having tested the Pioneer FH-X731BT, I’m happy to say that you can indeed do this. The technique is simpler than the conventional time alignment method. Instead of setting delays in milli-seconds for each driver, you key in the distance from you to the drivers. Let’s say you are 50 inches away from the midrange. Enter 50 in MID. Since the tweeter is closer by 1 inch, enter 49 in HIGH. Woofer is 4 inches from midrange, enter 54 in SUBWOOFER. The Pioneer will then adjust the delay automatically so that sound from the tweeter, midrange and woofer reach you at the same time. In other words, your speakers are now Time Aligned.

Sound Quality

In terms of sound quality, I’m impressed with the Pioneer FH-X731BT. If the speakers are properly calibrated and driven by quality external power amplifiers, it will beat a typical 5.1 Home Theater Receiver. However, you’ll need to invest in a microphone for calibration. Softwares are freely available in the internet that allow you to do basic frequency sweeps. You’ll also need to invest in a power supply. I’m using a 12V “Mean Well” switching power supply that I bought from Parts Express for $30.

How would I use the Pioneer in a home?

I would not hesitate to recommend using the Pioneer FH-X731BT as the head unit for your hi-fi. It is that good. On playback, I’m unable to tell whether my CD’s are playing from the Pioneer or from my PC with an M-Audio Delta sound card.¬†

Another use is for Background Music. Hook it up to a distribution amplifier and you will be able to have music in different zones like your living room, bed room, kitchen or office.

There’s also no reason why it cannot be used in a business environment. Pubs, fashion boutiques, food courts etc, can benefit from this Pioneer. Have all your music on FLAC and connect your External Hard Disk to the USB on the Pioneer and your entire library is available.

This Pioneer unit offers immense potential. It is only limited by your imagination.