Thump Does Thump - Bass Extension
As most of you know, Klipsch works very hard at insuring our speakers will be “LOUDspeaker.” Some ignore this philosophy because it is difficult to achieve, but it is the first rule that PWK founded and the first rule for our designs engineers at Klipsch.
High Efficiency…
What some of you may not know is that high efficiency speakers do not necessarily dictate wide bandwidth or full range. In particular, bass extension is one of the biggest challenges for high efficiency loudspeaker. Here is why…
You can generally treat the characteristics of a woofer to the gain curve of a transistor. This may not help you if you are not an electronic engineer but the same characteristics apply. To make drivers more efficient you can fool the laws of physics. Typically the motor has to be much more powerful. This means a bigger and badder magnet and thicker magnet steel to avoid saturation of the flux. This also means the cone has to be structurally rigid yet be a very light mass. All of our systems are horn loaded but this effect only goes down to a certain frequency unless it is a pro theater speaker. As I had mentioned earlier a 30 Hz horn must be 11.5 meters in length to control properly to that frequency. We do this buy folding horns in the cabinet on our pro models and some of our home models. So if you have a normal speaker size in a living room and you want it louder you should get a more efficient speaker first but remember that the bass may suffer if it has not been thoroughly optimized by a Klipsch engineer.
Attached is a representative graph of four theoretical driver responses.
In the graph you can see that the bass cutoff frequency is higher as the SPL goes higher. This can tend to be a general characteristic for a high efficiency loudspeaker. The 100 dB reference SPL driver has a -10 dB response at 35 Hz; whereas an 88 dB driver shows 23 Hz. This example is highly simplified but for the sake of understanding I thought I would start out with a simple set of trends.
To make up for this difference there is several things you can do in a 2 channel or home theater system. The most common thing to do is add a powered subwoofer. This is a very practical approach because it takes a lot of power stress off of the receiver for the main channel speakers and reduces the chance of IM Distortion by elimination of the cone modulations in the subwoofer band. In other words the 30Hz is no longer going to the main speaker (HP) but to the subwoofer so the IMD can’t occur. Another option would be to use a larger speaker enclosure. Typically the bigger the better to some extent when it comes to increased box size. This makes some incorrect assumptions that the Thiele Small parameters are still optimized in this larger box but if the engineer has done his homework he will have modified the driver to allow for the larger box. This is generally referred to as the Cas or Compliance of Air Mass for the speaker.
If anyone is interested I can get into the more intricate parts of a driver design where we look at Q of systems and drivers and box volume, etc.
The next time you think about how to improve your sound system you might want to start with the speakers. Amplifiers can only do so much, but if you have an efficient speaker such as a Klipsch you will gain more in decibels.
Keep Thumpin!