I have the following questions regarding SP Technology Loudspeakers:
1. Prior to discovering your products I was and still am interested in speakers, which utilize ribbon drivers. Proponents of ribbons claim the advantage of their low mass, which improves transient response. Since your products use a conventional dome driver, how do they compare with ribbons regarding transient response?
2. The specifications on your web site indicate that the primary difference between the Time Piece 2.0 and the Continuum A.D. is power-handling capacity. I am sure there are other differences, could you please elaborate?
3. The frequency response indicated on your site rolls off after about 16000. Why did you choose to do this there are many domes that extend well into the 20’s, or is it a by product of the wave guide technology?
Hello Audio Architect!
Pesonally, I will answer to the best of my experience your questions but I feel it would be much more prudent to wait for SP Pres. answers to the questions concerning the Timepiece 2.0 and the tweeter implementation...but from an educated and experienced aspect, I will answer them as I can.
This said:
1. Prior to discovering your products I was and still am interested in speakers, which utilize ribbon drivers. Proponents of ribbons claim the advantage of their low mass, which improves transient response. Since your products use a conventional dome driver, how do they compare with ribbons regarding transient response?
Lets talk about ribbons from a designers view and freom a listeners view, shall we?
I was very intriqued with ribbon drivers in the middle 70's and started working with them in design by the later 70's.
You remember the AMT1 by ESS?
After getting aquinted with them, I could see certain attributes that certainly caught my attention from the musical standpoint, although, I found their were other problems with that design (dipole, poor acoustic coupling due to magnet shape, crossover interaction at certain modes) but what did stand out is that they were open, fast, and could go very high.
When I worked in design with ribbons, I worked with the foster unit that Speakerlab in Seattle Wa. used in their designs then. It was property of Rank organasation UK at the time and this caused some working relationships with said tweeter to be rather strange business wise and also "political" in nature as well. IF you were not under their guiese at the time, you had no right to use the unit as it was liscensed. This said, the tweeter was awesome from 5K top 25K. That is Wide range for a single ribbon driver.
Going forward, my problem with most ribbons as in tweeters...(note that) (sans some of the newer 2000$/up units that I do not have the time or luxury to devuldge in) is firstly, they are quite fragile in power bandwidth. They do their finest job reproducing upper harmonics above the 4K fundamental up to the 30K and 40K range, althjough their dispersion is more non-linear than a dome (most ribbons use a mini waveguide to get around that) and the power response below 4K tends to cause serious problems, no matter how you load them acoustically. This said, they serve well as super tweeters to provide some additional "air" above 12k but for lower Frequencies, one would need to design the ribbon driver around that particular range. Basically what I am sayings is in my experience, ribbons that go all the way down to 100hZ, have a limited bandpass as do those that go in the above 20KhZ regions. All this means is if you want to try to reproduce 1K to 20K with a ribbon, As the timepiece waveguide demonstrates) their will be sacrifices in dispertion, powerband and other anomilies, because ribbons have a limited frequency range sweet spot. As been demonstrated by FOSTEX in their early 90' RB series of reference control loudspeakers, they had to use a four way design to keep all their ribbon drivers behaved in their specific range of frequencies. IT was a 4 way system crossed over if memory serves me from edgeless 12" woofers to 200hz, then 1K then 7K. It did sound mighty good indeed, and was a 40K dollar speaker syste. 3 way ribbons with woofers.
Ribbon tweeters have a hard time doing 20K and 2K at the same time coherently. They have a limited bandwidth power wise VS frequency.
So that is my exprience with ribbons to date. OF course, someone may find a way around said problems with another set of rules governing ribbons. Time will tell. At this day, the AMT 1 upper frequency driver, although not accurate to power response, did cover the widest frequency for its size In a ribbon device, in a single device, in it era.
the apogees (1 Ohm), and the Carver amazing loudspeaker, never took the design to a point that overcomed the objections to my ears and to the state of musicallity. Thie was always something, if you chose to look around it, that would be your choice.
Next:
Proponents of ribbons claim the advantage of their low mass, which improves transient response. Since your products use a conventional dome driver, how do they compare with ribbons regarding transient response?
Since ribbons have a limited frequency range in which they operate in linear fashion, you are comparing a driver that can go from 950hZ to 18K within a 1.5dB range to a driver that may not have that (or will not) spread. As per my observations, I feel that mass loading a driver with air in the impedance transformation gurantees a stable transient response througout its range, theirfore due to the wide bandwidth of the waveguide, you enjoy linear response throuout a wide range of frequencies both in amplitude, rise time and lineararity in frequency reponse. Perhaps SP Pres can elaborate.
The specifications on your web site indicate that the primary difference between the Time Piece 2.0 and the Continuum A.D. is power-handling capacity. I am sure there are other differences, could you please elaborate?
This is a question for SP Pres. I have not listened to the continuim so I reserve any explanation of fact. I will say that the 4ohm load presented will enjoy the amplifier delivering more power and the added cone ara and air movement potential shall result in higher dB enjoyment. As per what was done to the high pass unit to "keep up" with the compound woofers, only the designer is qualifyed to expound in this.
The frequency response indicated on your site rolls off after about 16000. Why did you choose to do this there are many domes that extend well into the 20’s, or is it a by product of the wave guide technology?
Lets look at a bare dome tweeter. It is small, ususally 1" or less. The radiationg area of the dome has a physical limit of vibration in hZ due to the moving mass and how much air it can "grab" This said, Domes fall terribly short in trying to propagate (we are talking 1" dome tweeters or up to 33MM, more than one inch) the lowest frequencies due to being too phyically small to move enough air at those frequencies (below 1.8K actually) to be linear within the diaphrams natural propagation pattern and what it can push. The low frequency effective limit of a one inch dome is 1.8K in power response. Most 1 inch tweeter voice coils would smoke at 10 watts driven with a 10 watt pure sine wave at 1800hZ Reason why is for the tweeter to be able to be light enought to actually do a nice 22K hZ frequency, the voice coil wire is 52 gauge windings and thermally, it cannot take that kind of juice at 1.8KhZ also.....where as above 12K, the dome is radiating sound from a small portion of the dome, namely the decoupled part of the center of the dome. Of course frequencies travel down the surface of the dome and you get interferance..but a 1" dome can effectively radiate full power response (1") at 23khZ but with vary narrow dispersion, usually less than 17degrees, even with a phase plug.
The waveguilde itself allows the dome in the timepiece loudspeakers to operate as low as 950hZ because it has an impedance transformation due to being coupled with the air in front of it, effectively. Because of this impedance transformation, the driver is unable to have flat power response throughout the entire waveguide above 20khz. It WILL reproduce above 20KHZ in very limited dispersion. Off axis, their is substantial rolloff above 18K...but I measured 2dB rolloff at 18K and pretty darn flat at 16K.
What does this mean? It means if you take linear power response of the system at a 30 degree reading, the highs above 16K roll off. Point source, no such anomily. It is only fair that the company provide real world specification rather to ignore them. The impedance transformation is a trade off. The dispersion narrows above 16K in order to provide flat power response down to 950hZ..
If you sit directly within ear shot of the waveguides of the SP technology loudspeakers, then you will enjoy wave proagation to 20KhZ at a relatively flat power response. I used my B&K 3529's to measure at direct beam, flat to 21K very very close to the actual dome itself (at distance, the rolloff is there)...but this is cheating, we do not have laser beam ears. I use them slightly off axis...because I can and they are accurate at 22 degrees...where many speakers are not. I let them point to a spot that is at my elbows if I have my hands extended...so they do not point at me. Even when I did have them point source, since I am almost 45, I did not enjoy any "extra" high frequency response.
I hope this has some enlightning to you questions about driver. As a long time speaker engineer, I really love reviewing my knowledge in this and if it serves you properly, and others, it is great to interact!
Everyone, have a great weekend. The grill is fired up...Just waiting to wrap the veggies and put them on.
