This started as an email to a guy who goes by the name of funkmonkey on AVS Forum. He emailed me about his desire for a great speaker that has bass extension to 30Hz. His budget was $2000. When he posted that he recieved an email from me, someone asked if I would post the email on his thread. Later, someone suggested a re-post it here as well. So here it is...
You asked me to post the contents of an email I sent you a few weeks ago. Sorry it took so long. I took the liberty of editing it somewhat for purposes of clarity. Let's call it...
THE $2000 CHALLENGE
funkmonkey wants a great speaker with bass extension down to a solid 30Hz and has a budget of $2000. This is a real challenge for a speaker designer.
It is possible to design a great speaker that plays to 30Hz. The problem is, it will exceed funkmonkey's budget. Here is why:
Speaker design is the art of balancing trade-offs. The speaker world is controlled by the laws of physics. You can't violate them. So you have to deal with the trade-offs involved.
Before we get going, let me say that there are many "good" $2000 speakers on the market today. But there are no "great" speakers that will play to 30Hz in this group.
First, it is important to realize that 80% of information is found in the midrange. If you don't get this right, you may have a speaker some will find acceptable, but certainly not what we will refer to as a "great" speaker. Herein lies the first trade-off.
Every driver excels in a certain frequency range and no driver can produce great midrange (accurate and detailed) and also produce deep, extended bass to 30Hz.
In a 2-way design, you can select a driver that plays deeper, but you will generally have to give up performance higher up in order to get more extended bass response.
Let's examine how this choice impacted our SongTower design as an example.
One major reason the SongTowers have been so well received, is that they reproduce an exceptionally accurate and detailed midrange and, at the same time, exhibit superb imaging (very deep and wide sound stage). All of these are the result of using a smaller (5") high-quality midwoofer with the extremely good dispersion characteristics a smaller driver can provide. (Most companies will publish FR plots 15-degrees off axis. We have published one at 60-degrees off axis.)
The trade-off is that a 5" driver will not play exceptionally deep. That is an issue we had to deal with and is where the SongTower's transmission line cabinet comes into play.
Unlike a sealed or ported cabinet, the transmission line cabinet is actually part of the speaker rather than an inert box holding the drivers. The energy radiating from the back side of the midwoofer excites air in the transmission line and the "line" is tuned to extend the bass response below where it would be using the same driver with any other type of cabinet. TL cabinets are difficult to design and not all drivers work in them. But, in this case, it works out quite well and many people are surprised by the bass extension of the SongTowers.
But even with the TL cabinet, we can't get to funkmonkey's 30Hz. So what are the alternatives at our disposal?
Well, going with a larger midwoofer in a 2-way design will allow greater bass extension. But the trade-off will be less detail and accuracy in the midrange and far more limited dispersion, resulting in a narrower and shallower sound stage.
In speakers sold at retail, midrange quality is often sacrificed for bass extension. When listening in an audio showroom, people are generally impressed by two things: the amount and extension of the bass and the "air" in the tweeter section. Only after they purchase them and spend some time with them, do they realize that there is a notable lack of midrange quality and relatively poor imaging. You can often add one-note, boomy bass as well.
And that "air" in the tweeter section can also be a problem. Since the larger midwoofer utilized cannot play as high, a tweeter must be chosen that can cross relatively low. In many cases, the top end "air" may result in pushing this larger tweeter to levels of distortion that can contribute to listener fatigue.
There are other alternatives in a 2-way speaker design, but they all involve advanced technology and very expensive drivers. The Seas Excel W18 in our Veracity series speakers is a good example. It uses a very low mass and extremely stiff magnesium cone to generate a great deal of midrange detail. But it is a very expensive driver in comparison to the drivers in the speakers in your price range. And even then, 30Hz is generally not obtainable.
In short, it is highly unlikely that a 2-way design of any consequence could meet the 30 Hz criteria.
Another alternative is a 3- or more-way design. But it is extremely hard to to successfully integrate 3 or more drivers. Integrating drivers, even in a 2-way, is difficult. Only a very small number of 3- or more-way speakers in the world get this right and they are very expensive.
In this situation, finding a combination of 3 or more great drivers and, at the same time, keeping the finished cost under $2000 is basically impossible.
This is especially true if you are designing a speaker that will be sold at retail. An audio dealer needs a 40 - 50% margin in order to carry a product. So the manufacturer must deliver the $2000 speaker to the dealer for around $1000.
In order to do that, and also cover overhead, marketing, R&D, the cost of the cabinets and provide for a profit, the manufacturer can't spend more than about $150 on parts (drivers, crossovers, binding posts, etc.).
To put that into perspective, the Hiquphon tweeters in our SongTowers would already exceed that parts budget. And the woofers in our Veracity HT3's cost more than that each.
Great musical reproduction starts and ends in the midrange. If you don't get that right, you may have an acceptable speaker, but it will not be a "great" speaker. Again, 80% of what you hear is in the midrange. The "you are there" experience most experienced audiophiles look for can be found in the midrange.
That is why we concentrate so hard on midrange performance. It is the foundation of every great speaker design.
Beyond that, you should have detail in the tweeter section as well. The more detail you have here, the better the speaker will re-create the overtone structure of instruments (the level of which is down considerably in volume from the fundamental tones). The more detail you have in the top end, the more "real" instruments will sound. It takes a very good tweeter to provide this detail without causing listener fatigue.
While bass extension is important, if your intention is to design a truly great speaker, you should pursue this only after the midrange and top end are addressed. Because unless you have those two elements well in hand, you will not have a truly great speaker.
So the problem in creating a $2000 speaker with bass extension to 30Hz comes down to accepting some trade-offs that really aren't all that acceptable if you want the best in audio reproduction. You will have to give up a detail, accuracy and imaging, which are attributes that contribute to the "magic" most experienced audiophiles look for.
The bottom line is this: If you are looking for a "great" $2000 speaker with bass extension to 30Hz, your search will likely be in vain. It just doesn't exist.
Well, I could go on forever. But that is probably enough for now.