Sorry for the delayed response. Here are some thoughts...
A few years ago I came across a number of AVS threads on the topic of building projection screen walls with speakers mounted flush with the wall surface. In thinking about this, it became obvious that since most speakers being sold today include baffle step compensation and mounting such a speaker flush in a wall would significantly change the effective width of the front baffle, "boomy" bass would be the most common result. (For an explanation, please refer to "Baffle Step Compensation Explained" on our web site - http://www.salksound.com/bsc.html
I was discussing the situation with a great speaker designer and friend, Jeff Bagby, and we outlined the basis for a speaker system design that could be mounted flush in a wall. And while we were at it, we thought why not create crossovers for wall-mounted and free-standing applications as well? At the time, I knew of no other company offering "customized" crossovers based on specific applications (now there are at least a few other companies doing so).
For maximum flexibility, this new system would also have to be sealed (not ported) since there was no guarantee that proper "breathing room" would be available in a given application for a ported design. This meant finding a driver that was optimized for a sealed enclosure.
Other criteria we decided upon included the use of a ribbon tweeter. At the time, there were not many speaker manufacturers using ribbon tweeters and based on the success of our Veracity HT1's, we thought we'd extend our use of them to this line.
The final criteria to keep the cost as low as possible was to use pre-built cabinets, produced off-shore, with custom-built cabinets as an optional upgrade.
Thus, the HTS home theater speaker system was born. It is an extremely flexible system with three speaker designs and three crossover options for each. So the resulting speakers can be tailored to almost any home theater (or music) application.
Sound-wise, the HTS speaker a very open, airy and transparent top end (just like our Veracity series speakers). In the midrange, they are not quite as detailed as speakers in our Veracity series and are a little "warmer" sounding. In many home theater applications, that can actually be a benefit. Some DVD's are mastered a little on the bright, edgy side and these speakers do a great job of smoothing out this type of source material.
While these speakers also do well reproducing music in a 2-channel or multi-channel format, they were primarily designed to be a very reasonably-priced, high-performance system for use in a traditional home theater setting.
The SongTowers, on the other hand, were originally developed with music reproduction in mind and they excel in this area. When first listening to this design, I was struck by, among other things, the clarity of the midrange. While this performance attribute really makes music come alive, it occurred to me that it would also be a great speaker for home theater applications since intelligibility would be very high. I also imagined that one of the first questions we would be asked when launching the SongTowers is "what would I use for a center channel?"
So I suggested to Dennis Murphy, the SongTower's designer, that we develop a center channel, surrounds and a subwoofer to round out the line. All of those designs are now essentially complete.
So, the questions are, how do these two systems compare and what would cause someone to choose one over the other?
As for the tweeters, there are very few dome tweeters that can compete with the Hiquphon OW2's in the SongTowers. As I recall, Oskar Wroending (OW) was the lead designer for ScanSpeak tweeters for many years and he now produces some of the finest 3/4" dome tweeters being made today. So the SongTowers have a lush, detailed and gorgeous top end.
The HTS series speakers utilize the AC G2si pure ribbon tweeter very similar to the G2 used in our Veracity series speakers. It is even more detailed and extremely transparent.
The fact that we use ribbon tweeters in our flagship speakers should be an inciation of my personal preference. But I can honestly say that I love Hiquphon tweeters and would chose them over almost any other traditional dome tweeter on the market today.
As for midrange, both the SongTowers and the HTS series speakers use paper-coned drivers. The SongTowers use 5" drivers that have greater dispersion resulting in better off-axis response and a wider and deeper sound stage. The only drawback is that a 5" driver is not normally as capable of extended bass response as a 7" driver. But in this case, the SongTower's quarter-wave transmission line-type cabinet allow bass extension beyond what these drivers would normally be capable of in a ported design.
The HTS series speakers utilize a 7" driver that was optimized for use in a sealed enclosure. As such, dispersion is not as great as in the 5" drivers in the SongTowers, but certainly on par with the best 7" drivers. Especially in a home theater setting, this is not a significant issue since listeners are seated in front of the speakers. So off-axis response really isn't a concern.
In terms of bass response, as indicated above, the SongTowers perform extremely well due to the cabinet design. The HTS series speakers also perform quite well in this regard, although being sealed, they roll off earlier than they would in a ported design. Again, this is not an issue since a subwoofer will almost always be used with these speakers.
So, which would be right in your application? Well, if you have a dedicated home theater and want speakers mounted flush in the wall or on the wall, the HTS series speakers are the most flexible in that regard. They would probably also be your choice if you love an open, airy and transparent top end.
If you are setting up a room where the main speakers can be placed even minimally into the room and/or you want a system that excels at both music reproduction and home theater sound, the SongTowers are more appropriate. They are an excellent music speaker that will also perform very well for home theater applications due to their high levels of intelligibility.
If I were setting up a system in a great room or family room, I would opt for the SongTowers regardless of whether or not it was for home theater, music or both. The WAF is quite a bit higher than is the case with the HTS series speakers. I might also note that we build the SongTower cabinets right here in Michigan for those who prefer to purchase products "made in USA".
I realize that some of you may have wanted a recommendation as to which speakers are superior. As I've often pointed out, speaker design is all about balancing trade-offs. In this case, selecting the "right" speaker system from among these two is also about balancing the trade-offs. In this case, however, you aren't really trading a whole lot either way.
I hope this helps.