THE IMPORTANCE OF TIME DOMAIN RESPONSE MUST READ


Speaker designers ignore or downplay the importance of TIME. Why?

A high end speaker should be as accurate as possible and that means it should not only be optimized with regard to frequency response but time response.

Back in the 70’s and around that time, speaker engineers thought that a perfect speaker would be one that had a flat response. This idea has waxed and waned in popularity over the years and even now there is no consensus.

What the speaker engineers forgot to consider is Time response.

The time reponse of a speaker is how fast it starts and stops. A perfect speaker would have a perfect time response of 0. Since this is not possible, we must get as close to it as possible. The problem is speakers engineers have neglected this aspect of the design and so speakers over the last 40 years have not improved in this respect.

Time is such an important aspect of the sound we hear. We not only hear tone but also time. The brain can detect time differences of only a few microseconds. Experiments have shown that the start of each note is what we use to determine what instrument is producing that sound.

We must ensure that our crossovers do not smear the time response because it will be heard by our ears. Time inaccuracy is why high end speakers do not sound like real instruments.

Diffraction from the cabinet can also cause time smear. We need spherical cabinets not square boxes. Tweeters need to be time aligned in order to ensure that when the woofer stops so does the tweeter. When the woofer starts, so must the tweeter. The woofer itself has to have a Qts of ZERO to prevent time smear. Ports must not be used or else you will get ringing.

We need to make it mandatory for speaker companies to publish the time response of all their speakers so that consumers can easily compare and decide exactly what they want. Some may actually prefer a speaker that has a poorer time response and that is fine. The problem is, we cant decide unless we know what we are buying can we?

Unfortunately, 90% of speakers on the market, even high end speakers have ports. And they are also made of cheap wood, even though there must be better materials by now. Some materials ring more than others.

So dont be deceived folks. If you want better speakers, you will probably have to make them yourself because speaker manufacturers dont care about sound quality. They spend millions of dollars on anechoic chambers all so that they can get a flat response but they spend zero effort on better time domain response. We are being duped.

kenjit

Showing 2 responses by larryi

One more thing, speaker/driver design involves balancing different performance parameters because there is no one design that optimizes all measures of performance.  Even if one is shooting for a very low Qts (extreme damping), this will affect other parameters, such as Cms (compliance of the speaker--the stiffness and how easily it is to move the diaphragm) and therefore, also the Fs (the resonant frequency which determines at what frequency the driver will roll off).  To achieve that high damping of a low Qts, the speaker will have to be very stiff, meaning it will also roll off at a high frequency, will require more power, and subjectively, it will sound dead and tuneless.

Qts that is being referred to is a Thiele-Small parameter for damping of the speaker--a combination of the mechanical and electrical damping--with a lower number indicating higher damping.  In a simple minded way, a lower number does reflect closer to instantaneous stopping of the driver after an impulse.  But, that does not imply that a lower number is better.  The parameter allows one to choose the right driver (primarily woofer) for the particular kind of speaker (sealed box, bass reflex open baffle, etc.) and to determine the particulars of the design being employed (volume/dimensions of the box, port dimensions, etc.) and so there is no one ideal value.  Higher values are better in some applications.  Pick too low a value and the speaker will lack bass, sound dead and overdamped.  

Unfortunately, as in previous postings, the OP has seized upon one thing as the magic bullet for perfect speaker design when there is no such thing.  There is no one speaker in the whole world that everyone will agree on as sounding the best, much less any single approach to achieving a high performing design.