I have been listening to my new SongTower QWT speakers for about a month. They are new MTM speakers in a floor standing transmission line cabinet, designed by Dennis Murphy, built and sold by Salk Signature Sound. Here are some photos.\r\n\r\nWhen describing the sound of new speakers, I should mention what speakers I previously used. This has an important influence on what I notice about the new speakers. My old speakers were vintage 3-ways, JBL L-100s that were greatly improved by new crossovers. The original L-100s were highly popular and highly flawed speakers from the 1970s. Aware of some of these flaws, I took them to Dennis Murphy for testing and redesign. Dennis kept the existing drivers and designed a totally new crossover that greatly improved the glaring bright sound of these speakers. If anyone is interested in more details about this, read the link in my signature line. It is a good illustration of just how important a crossover can be.\r\n\r\nThe 14" wide JBL cabinet contains a 12" woofer, a 5" midrange, and 1½" cone tweeter. As modified, the crossovers are about 950 Hz and 5,000 Hz. As a result of these rather high crossover frequencies, there is considerable beaming by the woofer and midrange drivers, as well as the rather large tweeter.\r\n\r\nIn contrast, the SongTowers come in a much narrower 8" wide cabinet, with two 5" midwoofers and a ¾" dome tweeter. The single crossover point is about 2.6 kHz. Dispersion is extremely wide and smooth. These speakers image beautifully.\r\n\r\nImaging\r\nAlthough standard frequency response curves can’t directly show how wide a speaker’s dispersion is, several of these curves measured with the microphone placed at various off-axis positions can indicate this. The attached figure compares SongTower frequency response measured on axis and 60° off axis. Below 10 kHz, the two curves are very close to each other. This excellent off-axis performance means great dispersion and is a major reason why SongTowers create superb imaging. Most other speaker manufacturers don’t show off-axis response. Those few that do usually show response curves measured at 15° or 30° off-axis.\r\n\r\nCompare this to the on and off axis frequency response of the well received Ascend Sierra-1 speakers (scroll down to the 2nd graph). At 30° and 45° off axis, the response of its 5" woofer drops in the 1-2 kHz range, and the 1" tweeter response drops off well below 10 kHz. I’m don’t mean to unfairly single out the Sierra-1 – I only do this because Ascend Acoustics is one of the few speaker manufacturers that show these graphs in similar detail for its products.\r\n\r\nWith my old JBL speakers, I was used to a sweet spot in the center of my sofa, about one sofa cushion wide. With the SongTowers, the sweet spot covers nearly the whole sofa!\r\n\r\nI often think of imaging for speakers as that “out of the box sound”. Instead of sounding like little musicians sitting inside speaker cabinets, speakers that image well create the illusion that the musicians have climbed out of the speaker cabinets and are sitting in your room. It reminds me of those impossibly tiny cars I saw at the circus as a kid, that would drive up and spew out 15 clowns. The last clown out usually leaned in the open door and said “we’ll meet up with the rest of you guys later”. So if you rate speakers’ imaging ability by how many clowns climb out, I’ll give the SongTowers a score of 30+ clowns. (Note, my clown\/image rating scale has no upper limit.)\r\n\r\nMidrange & Treble\r\nI have so far focused on imaging, but the frequency response curves also make it clear that the SongTowers have essentially a flat response across the entire audio spectrum. The SongTowers sound neutral, clear, and transparent. They are neither laid back nor too bright, neither veiled nor etched sounding. They stand out by doing nothing wrong. To some, this may seem like faint praise, because many of us have heard speakers, with a flat frequency response, that sound lifeless. The SongTowers stand out because they do all this while maintaining a sense that the music is live in the room where I sit.\r\n\r\nLinear response refers to a speaker’s ability to respond to increasingly more powerful signals by generating louder tones in proportion to the original signals. Every speaker has an upper and lower limit to its linear response range. The SongTowers have an extremely wide linear response range which adds to their ability to image well at low volume as well as high. In my old speakers, high volume was required to hear good imaging. The more I listen to the SongTowers, the greater I appreciate this unexpected feature.\r\n\r\nBass\r\nThe SongTowers’ bass is startlingly good. I can’t say this enough. The SongTowers’ bass is startlingly good. And I’m comparing it to JBL speakers with 12" woofers that were famous (or infamous) for bass response. Just how do two 5" drivers keep up with one 12" woofer with a huge alnico magnet and 3" voice coil made with edgewound copper ribbon? The answer is the transmission line cabinet design.\r\n\r\nProperly designed transmission line cabinets allow significantly greater bass extension than either sealed or ported cabinets would allow for the same woofers. In the SongTowers, these 5" woofers produce bass down to below 40 Hz. In a smaller ported cabinet, one of these same 5" drivers can only deliver bass to 50 or 55 Hz. (This is the Dennis Murphy 2-way DIY design that I built about two years ago that started me on the quest for better sounding speakers.) The transient responses of small woofers (the speed at which they start and stop making sound) are much faster that those of larger heavier woofers. This difference is easily audible, and is often spoken of as “fast bass”. The air inside SongTower cabinets actively participates in producing bass from below 40 Hz to above 125 Hz. It is louder than a sealed or ported cabinet would be with the same woofers, and if suitable small woofers are used, as in the SongTowers, the bass transients are fast.\r\n\r\nTransmission lines create louder and deeper bass by coupling the rearward woofer motion to a large column of air inside the cabinet, and allowing this energized air to move freely out of large openings. An additional benefit of this is improved midrange clarity because eliminating internal back wave reflections results in less midrange interference. In most other cabinet designs, these woofer back waves are largely absorbed or suppressed. It makes me wonder how much low frequency energy is wasted by these designs. The only way they can generate good bass is by brute force.\r\n\r\nSo, how do they sound? Jim Salk describes the SongTowers at his website as follows:\r\n\r\n• The driver dispersion and the slim cabinet combine to offer superb imaging\r\n• The soundstage is deep and wide with instruments and vocals precisely located.\r\n• The top end is lush and detailed – just what you'd expect from the exceptional Hiquphon OWII tweeter\r\n• Midrange is detailed and accurate. Voices are rendered with realism. \r\n• The TL cabinet results in very impressive bass extension considering the design uses 5" midwoofers.\r\n\r\nIn my honest opinion as an owner, this isn’t just slick marketing language; it’s the best description I’ve seen of how the SongTowers sound. Considering the first rate quality of the cabinet construction and finish, I don’t know how he does this for $1,500. See this example of the Salk cabinet construction process. The speaker shown, the Salk HT-3, is much more complex to build than the SongTower, but the care and quality are similar.\r\n\r\nSome of you may have noticed a repeating theme here – that I have three pairs of speakers designed (at least in part) by Dennis Murphy: the CAOW1 2-ways, the rebuilt JBL L-100s, and the SongTowers. If you call me a Dennis Murphy fanboy, I’m guilty as charged. I have to wonder why everyone else doesn’t own speakers he has designed – they sound that good.