I have read this thread with great interest (as you might imagine) and thought perhaps a few comments might be in order.
First, a big thanks to KEW for taking the time to do this write-up. Much appreciated. Second, my response here may be a little long winded - my apologies in advance.
As I've said many times in the past, speaker design is all about balancing trade-offs. Take tweeters for example.
Traditional dome tweeters are very popular as they generally have very good dispersion characteristics. Larger dome tweeters are quite popular since they can be crossed over lower allowing for woofers that can play deeper. But this is generally at the expense of performance higher up. (Which is why we use a 3/4" dome tweeter rather than a 1" in our standard SongTowers.) But even the best silk dome can only deliver so much detail.
In an effort to generate greater detail on the top end, some manufacturers utilize metal dome tweeters. These tweeters offer similar dispersion characteristics but gain the advantage of greater detail and extension on the top end.
This added performance, however, can come at a price. Many near-field monitors used in the recording industry, for example, take advantage of the top end response of a metal dome in order to produce more detail - an advantage in a mixing or mastering situation where you want to hear all the detail in a recording. But as anyone who has spent a full day mixing on these monitors can tell you (I spent about 35 years in recording studios), they can be a bit fatiguing. The detail they provide sounds glorious at first, but can be hard to listen to for extended periods.
One solution is to pad the tweeter down a little and this is often done. But the FR is no longer flat and you give up some of the high end detail that the driver could otherwise provide. So its a trade-off.
Another approach to providing enhanced high end detail is through the use of a ribbon tweeter. You can generally voice a good ribbon flat and there is no hint of long-term fatigue. The trade-off is somewhat more limited dispersion.
In the early days of ribbons, limited dispersion was a real problem. Today's better ribbons use shorter ribbon elements and some are horn loaded. These (like the LCY tweeters used in the SongTower RT version) tend to have good dispersion characteristics that approach that of a traditional dome tweeter.
When we first same out with the SongTowers, we used the 3/4" Hiquphon silk dome tweeter - one of the finest traditional domes available. The off-axis response of the resulting speaker was so good, we actually published an FR graph at 60-degrees off axis.
As the model gained popularity, we received quite a few requests for the same speaker with the added detail of a ribbon tweeter. So we came out with the RT version to address this need. While the off-axis response was somewhat more limited, most of our owners listen on-axis or relatively close. So the more limited dispersion, for these customers, is not an issue. They wanted a speaker with a very detailed and transparent top end and we felt that this was the best solution available.
What implications might this have on proper speaker set-up? Well, the midwoofers used in this design have extremely good dispersion characteristics. So with the RT version of the SongTower, I would start with no toe-in at all. The pinpoint imaging should still be quite good, but the soundstage should be quite a bit wider. I would only toe the speakers in if improvements in imaging were required.
I noticed in the write-up that the SongTowers were toed-in more than the other speakers. In theory at least (every set-up will be somewhat different) SongTower RT's are one model that would benefit from less or no toe-in.
Switching gear, let's consider the mid-bass/bass response.
My first comment would be that the bass in the SongTowers is not exaggerated in any way. The SongTowers use a mass-loaded quarter wave TL design (pioneered by Martin King) to extend the bass response of the system. This method takes advantage of the energy generated by the rear of the woofer cones to excite air in a chamber that is tuned to reinforce the bass response under the F3 one would normally obtain in a ported cabinet. When the output of the cabinet terminus combines with the output of the midwoofers themselves, the bass response is extended. Normally, you would obtain an F3 of around 50Hz with the SongTower midwoofers in a ported cabinet. But by utilizing quarter wave resonance, we were able to extend this response to 38Hz. In the process, no attempt was made to "tip up" or artificially exaggerate the bass response in this design. The SongTowers were designed to be extremely flat and accurate in terms of bass response.
Another poster commented on active amplification vs. a receiver. I can only speculate here. Customers who have typical receivers of this type are normally extremely please with the performance of their SongTowers. But we have had many owners upgrade to separates and report a significant performance increase, especially in the area of tighter and more articulate mid-bass/bass.
This is most likely due to a number of factors including a more robust power supply and better woofer control. Keep in mind here that the lower the speaker plays, the more power is required of the amp/power supply combination. While the amplifier circuits in a receiver can deliver the rated power, the power supply may not be able to supply the instantaneous power required to keep transients tight and articulate.
I saw a very interesting demonstration a few years ago. An RMS and peak-reading meter were both set up on an amplifier driving a pair of speakers. While listening to music, the RMS (average) meter ran about 5 - 8 watts at normal volumes. But, at the same time, the peak meter often hit 250 or more watts during transients (drum hits and the like). If the amplifier circuits and power supply cannot deliver the peak power demanded by these transients, the quality of response can suffer. This is often the case with receivers whose power supplies tend to be less robust. And that is why owners who upgrade to separates perceive an increase in sound quality.
I don't know what difference it would have made in this case, but I would assume that a high quality amp would have significantly improved the performance of the two speakers being powered by the receiver.
On a completely unrelated note, WrpDrv commented...
Not sure I could stomach the presence of HT4's in my house - they just look way too darn goofy to me, but the eye is in the beholder, and I wonder if they will be worth the entrance fee.
First, congrats on your new speakers! Enjoy!
As for your comment, I fully understand that the HT4 design might not appeal to you - tastes do vary. But I should explain that the look of the HT4 was not done for aesthetic or design reasons. Each element of the design was done because we felt it was the best way to do it.
For example, we wanted as little enclosure around the tweeter as possible. So you see very little baffle around the tweeter front edges and the enclosure tapers away as soon as it clears the tweeter body. This allows for maximum tweeter dispersion. The midrange enclosure is open backed and is radiused on the sides to transition from the narrow tweeter section down to the wider woofer cabinet. The woofer cabinet on the 12" is much larger and is radiused on the top to come up and meet the upper midrange/tweeter section.
I could go into more detail, but in short, every part of these cabinets was designed to optimize the performance of the drivers. They look like what they look like because that is the way they had to be built to meet our performance criteria. No compromises were made for design/aesthetic purposes.
The same was true for the drivers. Each driver was chosen with regard to performance. No consideration was given to cost. The net result is that this is a very expensive speaker.
As for whether or not someone feels paying this much for a speaker is justifiable, the only thing I can say is that these speakers are essentially flat from about 18Hz to 60KHz. Their on-axis response and 30-degree off axis response look nearly identical. They can handle any program material with minimal distortion and do a complete disappearing act. For me, this is the speaker I have been wanting all my life. It was well worth the effort and we feel it represents an incredible value (of course, we are extremely biased).
The fortunate thing is that we have so many good choices.
Once again, sorry for the long-windedness and thanks again to KEW for taking the time to give us a listen.
- Jim
