Aastra’s 6739i vs Polycom SoundPoint IP650?

Aastra 6739i Desk PhoneOn the VUC call of May14th we were fortunate to be joined by Tony Lewis, CEO of Schmooze Communications, the creators of PBXact. Tony was, to the best of my knowledge, the very first person to join the call using Aastra’s latest uber-desk-phone, the 6739i.

Tony was able to fill us in on some of more details about Aastra’s product line, and specifically their implementation of wideband voice…or as they call it “Hi-Q.”

It was just over a year ago that there was a hint that Aastra has released some firmware for their existing 57 series phones that implemented G.722 wideband capability. However, like snom before them, they were adding wideband voice support to a hardware platform that was not from the outset designed around such capability.

The result was Hi-Q, a combination of smart marketing and engineering. Aastra tweaked the DSP processing in their existing phones to compensate for some potential inadequacies in their existing transducer hardware. Given some help from firmware based frequency contouring the existing models could support wideband voice out to 7 KHz, certainly enough to support G.722.

In the traditional broadcast signal chain, be it radio or television, there is all kinds of audio processing taking place. Within certain physical limits basic frequency contouring (equalization) is often very effective at overcoming consistent roll-off of the high- or low-end of the physical capabilities of transducers.

The very fact that Hi-Q was initially a pure software implementation makes the 57xx models a curiosity in themselves. It would be interesting to perform some controlled measurements to see if their approach was as effective as simply using better, and presumably more costly hardware.

Sadly, my aged 480i CT was not capable of loading the Hi-Q firmware so I guess that I’ll never know.

As the company moved to launching newer models like the much-admired 6739i they had the opportunity to address wideband voice in the hardware itself, without relying upon electronic trickery any further.

Since this past Friday was the first time that we had someone using the new Aastra 6739i it presented an opportunity to do some ad hoc comparison of audio quality. VUC regular Karl Fife instigated this effort, asking Tony to try both the handset and the speakerphone. As a comparator we have Karl using both the handset and speakerphone of his Polycom SoundPoint IP650.

In this initial sample I choose a section of the call where Karl as asking Tony and myself about what hardware we were using. In the screen shot from Cool Edit Pro you see the distribution of energy vs frequency. The Y axis is frequency from 0 Hz to 8 KHz, consistent with a G.722 call sampled at 16 KHz.

I’ve also added a yellow line at 4 KHz, which is the absolute best case point beyond which there would be no energy in a G.711 narrowband call typical of the PSTN.

Finally, I added notation below the timeline display indicating who is speaking by way of initials; Tony Lewis, Karl Fife, or Michael Graves (me!)

Handsets: Tony Lewis (Aastra 6739i) vs Karl Fife (Polycom IP650) vs Michael Graves (Eyebeam+Plantronics Savi Go)

(Click on the image to see a large version in a separate window)

A short while later we did the same little comparative listening test, this time with both gentlemen using their speakerphones.

Speakerphones: Tony Lewis (Aastra 6739i) vs Karl Fife (Polycom SoundPoint IP650)

(Click on the image to see a large version in a separate window)

Of course, these are completely unscientific and not really a rational basis for comparison. The two men have very different voices and were in different acoustic environments. However, I still think that the visualization exercise is helpful in confirming for our eyes what our ears are actually hearing.

While I still respect and admire my Polycom IP650s, I look forward to trying the Aastra 6739i.

  • I have a few 57iCTs around somewhere, I’ll load one up with the latest firmware and try to get on the call this week to see how the older hardware handles it.

  • Kim

    Hi,

    nice comparison. It would be great, if you could compare the smaller one: Aaastra 55i and 53i, too

    Kim

  • Michael

    What application did you use to extract the G.722 stream out of the pcap file and convert it to a wave file? Wireshark doesn´t support G.722, only G.711…

    • I was on the call using my Polycom IP650 with the optional productivity suite. Thus I could record the call to the USB stick on my phone. If the IP650 is on an HDVoice call, as it would be called into ZipDX via SIP URI, it records an uncompressed wav file sampled at 16 KHz.

  • Michaek

    Thanks for the information. You don´t know another application that is able to convert pcap with G.722 audio to wav?

    • Not from a network capture. However, I often use a soft phone to record a call. Many soft phones can do this, although I generally use Counterpath’s Eyebeam.