I have run T/S tests on a pair of 1772's using a Smith & Larson Speaker Tester. The drivers were broken in for one hour a Xmax. Average of three runs each for the two drivers are:
Re ohms 7.28996
Fs Hz 42.59512
Zmax ohms 28.85236
Qes 0.44508
Qms 1.31602
Qts 0.33256
Le mH 0.04414
Diam mm 165.5
Sd mm^2 21512.25
Vas L 72.76948
BL N/A 7.4432
Mms g 12.6453
Cms uM/N 1106.912
Kms N/M 905.7046
Rms R 2.57074
Efficiency % 1.1911
Sensitivity dB(1 watt) 92.76138
Sensitivity dB(2.83 volt) 93.166
The S&L tester does a constant current test, so the numbers will differ somewhat from testers that do constant voltage. The results are not surprising. the Vas lower than published is what I normally see, although I would have expected Qts to be somewhat higher than published rather than lower.
Nothing untoward here. I won't try to explain the glitch at 150Hz for now. I am impressed that there is no reflection off of the surround at ~1000Hz. That big old aluminum phase plug plus (I presume) a shorting ring very effectively kills any impedance rise.
One thing of note: The 1772's suspension is either not progressive or only weakly so. Unlike most Fostex drivers that can't be over-driven to Xsus, it is very easy to bounce the TB off of the back plate. Some care will be required is high SLP low frequency applications.
I will mount these drivers in my FT-2000 cabinet (MLTL). I won't be testing on an EIC baffle, so my FR plots may well have some box defraction artifacts in them, but so be it. It may be a few days before I report back.
Bob
Re ohms 7.28996
Fs Hz 42.59512
Zmax ohms 28.85236
Qes 0.44508
Qms 1.31602
Qts 0.33256
Le mH 0.04414
Diam mm 165.5
Sd mm^2 21512.25
Vas L 72.76948
BL N/A 7.4432
Mms g 12.6453
Cms uM/N 1106.912
Kms N/M 905.7046
Rms R 2.57074
Efficiency % 1.1911
Sensitivity dB(1 watt) 92.76138
Sensitivity dB(2.83 volt) 93.166
The S&L tester does a constant current test, so the numbers will differ somewhat from testers that do constant voltage. The results are not surprising. the Vas lower than published is what I normally see, although I would have expected Qts to be somewhat higher than published rather than lower.
Nothing untoward here. I won't try to explain the glitch at 150Hz for now. I am impressed that there is no reflection off of the surround at ~1000Hz. That big old aluminum phase plug plus (I presume) a shorting ring very effectively kills any impedance rise.
One thing of note: The 1772's suspension is either not progressive or only weakly so. Unlike most Fostex drivers that can't be over-driven to Xsus, it is very easy to bounce the TB off of the back plate. Some care will be required is high SLP low frequency applications.
I will mount these drivers in my FT-2000 cabinet (MLTL). I won't be testing on an EIC baffle, so my FR plots may well have some box defraction artifacts in them, but so be it. It may be a few days before I report back.
Bob
Oops! You're right. I misread the flier. So the specs are pretty much as I would have expected.
I have had a quick listen, of course with zero break-in. The TB's are not as forward as say 207's, I presume because the TB's don't have that 3k hump, but are every bit as detailed (what ever that means). We will just have to wait and see how the TB's mature.
I was playing these speakers with a visitor who had never heard anything better than a HT in a box. While listening to jim Croce's "Operator". He commented that he could hear the pick on the guitar string. Yes you can! There is live after iPod.
Bob
Bob, do the TB's require about the same equalization as the Fostex drivers to achieve flat response with rising frequency?
I applied 4dB of BSC starting at 400 Hz and 4dB of treble cut starting at 3kHz, simply because the factory FR indicated that. Initial impression is that the TB sounds more like an F200A than an FE207E, probably because of a lack of the 3kHz hump we have come to know and love with Fostex drivers. I'm going to let the TB's cook a while longer before I measure them.
Bob
If I were going to build a MLTL enclosure, should I order plans for the FT-2000 and not the LT-2000 MKII? Or will there be an FT-2000 MKII for the Tang Band W8-1772 driver?
As you are well aware, MLTL's are quite tolerant to driver variations. Any of the three drivers -- Lowther DX3, Fostex FE207E and TB W8-1772 will work in either cabinet with a bit of fiddling with port lenght and series resistance. If I was doing mass production, I'd have a compromise cabinet and let it go at that. Since I am doing one-off custom work, there is no reason not to optimize the cabinet to the driver.
I originally did the LT-2000 for the DX2. However, the price of the DX3 is so close to that of the DX2 that I decided to ignore the DX2 entirely and only advertise the DX3. I found that the DX3 is happier in a slightly smaller cabinet. Hence the LT-2000 MkII. The FE207E works well in the original LT-2000 cabinet with a longer port, so the name changed to FT-2000. I could add the MkII just to align things, but it would be meaningless. The real difference between the LT-2000 MkII and the FT-2000 is 1 1/2" in depth and the port length. Just looking at the Vas numbers suggests that the TB would like an even larger cabinet.
My naming convention goes like this:
- First letter: Manufacture
- L = Lowther
- F = Fostex
- T = Tang Band
- Second Letter: Cabinet type
- T = Transmission line -- MLTL
- B = Bass reflex
- Number: Driver size
- 20 = 20cm in BR
- 2000 = 20cm in MLTL
I was going to name my speakers after conquistadors which has local meaning here in Hot Springs Village AR, but I was told that such names are offensive to a small population. Geez -- get over it!
BTW there is no chance that the TB will go into the FB-20 BR cabinet. It needs some 10% larger cabinet -- maybe 40 l/40Hz.
Now the short answer: You can use either set of plans and adjust the cabinet depth accordingly. I presume that I will draw up TT-2000 plans once I become familiar with the driver.
Bob
Personally, I reckon your conquistador naming idea would've been really interesting Bob.
Sounds good to me. It should have been obvious, but I didn't understand the naming convention until you explanied it. I'll wait until you've finalized the TT-2000 enclosure depth and port length recommendation.
Bob, I am really psyched to hear your listening impressions of this interesting new driver!
P.S. I think it's good to shy away from the conquistador stuff. Here in New Mexico, people have really long memories. 400 years ago is like yesterday.
In the 1590's (or thereabouts), the "last conquistador" Juan de Onate cut the feet off 24 Native American men (an event that nobody to my knowledge disputes). 400 years later, some Native Americans did the same thing to his bronze statue (they cut a foot off), and it stirred up tremendous debate about whether this figure should be honored, whether the statue had been vandalized per se or simply made to tell another side of the story, etc.
On the other side, the descendants of the original Spanish settlers are still fighting in the U.S. courts for certain land grants. The past is still the present in these parts.
P.S. I think it's good to shy away from the conquistador stuff. Here in New Mexico, people have really long memories. 400 years ago is like yesterday.
In the 1590's (or thereabouts), the "last conquistador" Juan de Onate cut the feet off 24 Native American men (an event that nobody to my knowledge disputes). 400 years later, some Native Americans did the same thing to his bronze statue (they cut a foot off), and it stirred up tremendous debate about whether this figure should be honored, whether the statue had been vandalized per se or simply made to tell another side of the story, etc.
On the other side, the descendants of the original Spanish settlers are still fighting in the U.S. courts for certain land grants. The past is still the present in these parts.
OK, here are some FR plots. The first is scaled to match the plot on the TB spec sheet:
Now one stretched out so the details are visible:
That's the smoothest on-axis FR plot I have ever seen for a wide-range driver. Off-axis, things gets pretty messy above 5kHz. I'll have to see if I can hear any of this.
The sound of these speakers is pretty nice. As noted elsewhere, I applied 4dB of treble cut based on the factory FR. That may be too much. After some more break=in, I'll pay with the EQ.
Bob
An externally hosted image should be here but it was not working when we last tested it.
Now one stretched out so the details are visible:
An externally hosted image should be here but it was not working when we last tested it.
That's the smoothest on-axis FR plot I have ever seen for a wide-range driver. Off-axis, things gets pretty messy above 5kHz. I'll have to see if I can hear any of this.
The sound of these speakers is pretty nice. As noted elsewhere, I applied 4dB of treble cut based on the factory FR. That may be too much. After some more break=in, I'll pay with the EQ.
Bob
Oh, yea -- Here is the impedance plot:
Bob
An externally hosted image should be here but it was not working when we last tested it.
Bob
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