I have a pair of Stephens Trusonic FR150s and I think they can perform better than how I hear them play in a pair of Barzilay ported cabinets (3.5 cu ft/100 liters). They also need help beyond 5 kHz or so, but I thought I'd like to try 'em as FRers for a while. I imagine they won't be all that great in an open baffle either, and the baffles would probably be HUGE, but if you think otherwise, I'd like to know.
So: K-15, or am I barking up the wrong tree? I know I'll probably have to hear for myself, but initial feedback might be helpful.
So: K-15, or am I barking up the wrong tree? I know I'll probably have to hear for myself, but initial feedback might be helpful.
Alas, I don't have an audio signal generator or mic available. I miss the sweet little Wavetek I used to have. I just realized I might be able to generate audio waveforms with a computer. T-S can be measured with REW s/w?
Searching for T-S data on the internet has proved fruitless so far with a "not quite" at Audio Heritage (and it's been nine years since that thread started!). I guess I just need to get off my *** and borrow a mic and do the work of measuring.
Nevertheless, thanks for your generous offer to help me out.
Searching for T-S data on the internet has proved fruitless so far with a "not quite" at Audio Heritage (and it's been nine years since that thread started!). I guess I just need to get off my *** and borrow a mic and do the work of measuring.
Nevertheless, thanks for your generous offer to help me out.
You don't need a mic to meas T/S. Many examples of howto's on the web. Need oscillator (PC), a resistor, DVM, and some test leads.
Measuring Loudspeaker Driver Parameters
T-S Parameter Calculator
Measuring Loudspeaker Driver Parameters
T-S Parameter Calculator
you can do the parameters Weems method using 600 to 1K series resistor and introducing a 10 ohm shunt resistor at the frequencies of interest - that way, a cheap meter can be used - just crank the oscillator or soundcard's output up to read "10", remove the 10 ohm load resistor, connect the speaker and read the speaker relative to that "10". K15 would probably be fine for that speaker - smaller K's for 15" can be built but move the LF corner up kinda high. K15 is a nice design. A new K sans front shelf would work well but I think the distance from the inside of the wings to the port board would need be lessened and maybe the height made a bit more - - can those small changes be seen in akabak? K15 imo can have very nice bass response - jaw dropping at times on transients - and the cone barely moves.
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Okay, T-S measurements complete for a Stephens Tru-Sonic FR150 speaker:
Qms: 7.4 (mech Q)
Qes: 1.044 (elec Q)
Qts: 0.965 (total Q)
Vas: 357 liters
Looks like it definitely needs a closed back box and won't fare well as an OB speaker driver.
Qms: 7.4 (mech Q)
Qes: 1.044 (elec Q)
Qts: 0.965 (total Q)
Vas: 357 liters
Looks like it definitely needs a closed back box and won't fare well as an OB speaker driver.
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A Qts of close to 1 should work well in an OB and may not work as well in a Karlson. What technique did you use to measure the TS params?
When I get some time I will run the K15 sims but I will also need fs, Sd, Re, and Le. You probably have all this from the program used to calculate the Q's.
When I get some time I will run the K15 sims but I will also need fs, Sd, Re, and Le. You probably have all this from the program used to calculate the Q's.
if qt is really that high then you'd have to tune low plus would probably have some peaking. An open baffle should be good and simple. Where was fs and what was its magnitude?
I used the calculator link posted above and used Rod Elliott's technique
Re: 6.2
fs: 21 Hz
Sd: 1238 cm^2
Le: 9.7
Re: 6.2
fs: 21 Hz
Sd: 1238 cm^2
Le: 9.7
was that 0.97mH ? - I wonder if the speaker had that high of a qts when new? - how large is its motor?
good catch GM---Sd for a JBL 2220H is only ~890 sq.cm. and it had a small surround. - - the magnet must be weak unless the data is off - - ?
Well, the old brochure's specs imply ~ OEM Altec 515B measured specs except with a gap flux density midway between it and the 416B's, so with a measured 21 Hz Fs [Vs two different brochure's 20, 23 Hz], ~825 – 856 cm^2 Sd and published ~13 k gauss flux density, I'd expect to see Qts around 0.25-0.28 and a Vas around 700-1000 L.
At a glance then, something doesn't compute since its Fs hasn't risen over time to account for its much lower Vas, higher Qts unless the magnet has been severely drained as his measurements seem to imply. That, or it’s a very heavy diaphragm assembly since it calcs as ~170 g, but all low Fs HE 15” of the day that I’m aware of were at least half this, so I’m inclined towards a weak magnet.
GM
At a glance then, something doesn't compute since its Fs hasn't risen over time to account for its much lower Vas, higher Qts unless the magnet has been severely drained as his measurements seem to imply. That, or it’s a very heavy diaphragm assembly since it calcs as ~170 g, but all low Fs HE 15” of the day that I’m aware of were at least half this, so I’m inclined towards a weak magnet.
GM
Sim of FR150 in K15
Soldersmoker,
I used an estimated Sd of 993 cm2 based on an assumed 14 in active cone dia. This driver is not well suited for a K15 as there is a huge bass peak which probably means the Qts is too high. I tried it with the larger Sd and it is even worse. Sorry...
X
Soldersmoker,
I used an estimated Sd of 993 cm2 based on an assumed 14 in active cone dia. This driver is not well suited for a K15 as there is a huge bass peak which probably means the Qts is too high. I tried it with the larger Sd and it is even worse. Sorry...
X
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if his Stephens is truly that far out of whack then it would probably peak as simmed. I had ~ 6dB peaking with a screwed up pair of Peavey 1808 (T-S below) in a small "K18" also I have a pair of Peavey 15cx whose fs and qes is also pushed up - both pairs have very stiff spiders - perhaps silicone oil would help if I ever get back to them
even with the peaking, it didn't sound as boomy as it measured - the messed-up & stiff PV 18s are usable for open baffle and sound more articulate in their range than the budget Goldwood GW1858 - the Goldwood would dig deeper - the PV better for opera.
were the OP's F0 and F1 precise?
Revc= 6.2040 ohms
Fs = 46.5065 Hz
Zmax= 61.6199 ohms
Ro = 19.5522 ohms
F0 = 37.9675 Hz
F1 = 56.4854 Hz
Fmin= 187.8370 Hz
Qms = 7.9149
Qes = 0.8861
Qts = 0.7969
Le = 0.8436 mH @1kHz
XLe = 10.9585 impedance @1kHz
PLe = 28.9275 phase @1kHz
even with the peaking, it didn't sound as boomy as it measured - the messed-up & stiff PV 18s are usable for open baffle and sound more articulate in their range than the budget Goldwood GW1858 - the Goldwood would dig deeper - the PV better for opera.
were the OP's F0 and F1 precise?
Revc= 6.2040 ohms
Fs = 46.5065 Hz
Zmax= 61.6199 ohms
Ro = 19.5522 ohms
F0 = 37.9675 Hz
F1 = 56.4854 Hz
Fmin= 187.8370 Hz
Qms = 7.9149
Qes = 0.8861
Qts = 0.7969
Le = 0.8436 mH @1kHz
XLe = 10.9585 impedance @1kHz
PLe = 28.9275 phase @1kHz
What 15" has a Sd this large? Even the old single fold paper surround drivers has less than this.
GM
Dunno, guess it depends on its design. FWIW it didn't work for me on the few various drivers I tried it on, though had some limited success with WD40 and Marvel Mystery Oil.
Yes, it'd be nice if he posted all of his data...........
GM
In the absence of a reasonable number I assumed that the active membrane area is about 1 in less than nominal 15 in dia or 14 in. But looking at the Sd of a B&C 15 in driver I see that it is closer to 13 in (or Sd of 855 cm2). Still won't matter much given the way-high Qts. Best use would probably be an OB.
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