Scottmoose said:
Thanks Scott, once again! I'll put the order in ASAP.
Also, what exactly have I done by putting in that 2.49 ohm series resistance?
From what WinISD Pro is showing me, it looks as though the series resistance has brought up and/or flattened out the response between the tuning point (67Hz) all the way up to 500Hz.
Just for fun, I added another model with those 4.7 ohm resistors I tried before and it shows a stead rise from 500Hz down to the tuning point, equaling a total of +1dB.
Although, it doesn't show anything about that nasty "suck-out" I got, naturally.
chops said:
so if it can "talk" directly to an Airport Express, with a suitable chain of components connected thereto, you could have at least reasonable 2 channel audio from your phone?
Forgive me if I still find that potential more than a bit intriguing.
chops said:
Right. You're artifically raising the Qe & Re, of the driver & lowering Bl. Mass corner (Fhm) will drop from 455.84Hz (assuming the factory specs are accurate, which they won't be), to 355.5Hz, & with 4.7ohms in series, you'd be looking at 300.75Hz. In practice, I the motor of the 103 is likely to be substantially weaker than Fostex's claims, so mass corner in all cases will be somewhat lower.
Scottmoose said:
Two questions...
1) What exactly is "mass corner" and where did that 455.84Hz come from? I've seen the term mass corner used several times and can't find anything about it anywhere. Also, what is the advantage of having a lower mass corner?
2) Isn't "BL" the strength of the magnet or motor system? How does adding series resistance cause this to lower?
Sorry for all the questions all the time. I'm just trying to learn all I can so I can better understand what I'm reading and doing.
As usual, many thanks! 😉
Mass corner (Fhm) is the -3db point of the driver's natural LF roll-off. A driver with a high mass-corner is inherently very well damped (usually with an extremely powerful motor), & a shallow roll-off; a unit with a lower mass corner is less well damped (usually with a weaker motor) & a steeper roll-off. Advantage, as ever, is application dependant, but a driver with more raw motor power is usually more flexible as you can always get rid of what you might not need.
Re the latter, it doesn't exactly lower Bl itself per se, but it has that effect.
Re the latter, it doesn't exactly lower Bl itself per se, but it has that effect.
Scottmoose said:
Ah... Now I understand. Thanks!
Just curious though...
Looking at the FE103E spec sheet, the impedance starts rising right around 600Hz. When impedance rises, an amplifier starts putting out less power to the driver. If this is the case here with the 103, is that the cause of the LF roll-off starting at 455Hz? The driver is getting less power below 600Hz, so it's starting to produce less output also below 600Hz which would probably put it right around -3dB at 455Hz. (funny enough, this is also right around the BSC frequency of my baffles - 467.24Hz)
I mentioned earlier in one of my other posts yesterday that there is no measurement for "Le" in the spec sheet, I'm assuming because the small VC of the 103 acts more like resistance than it does inductance. Since you need to know the inductance of a driver to formulate a Zobel network, it is even possible to make one for the 103? And if so, would it even effect it down around the Fs where the impedance peaks? If it's possible to have a Zobel network that works that low, wouldn't that help a lot in solving the shouty, forward sound of these drivers?
chops said:
Only true when you have a voltage amplifier... if you have a current amplifier, the power will increase. So far the best amplifiers for this familiy seem to tend toward the current end of the spectrum.
attached is an FE127 impedance plot, FE103 will be similar.
dave
Attachments
planet10 said:
But only until the output bumps into the voltage rail of the amplifier. (Analogous to a voltage amplifier running out of bias.)
eLarson said:
Indeed... true of any amplifier. It can only put out more power until it runs out/clips.
dave
planet10 said:
Well all I'm using is the little original SI T-amp.
I have no clue what you guys mean about voltage and current amplifiers. All amplifiers use both current and voltage to amplify the signal. 😕
chops said:
Most SS amplifiers these days approach what are termed voltage amps -- they try to maintain constant voltage and then deliver as much current as is necessary.
A few amps (FirstWatt F1) try to keep current constant and deliver as much voltage as necessary -- current amps.
Most amps are in between true V-amps & c-amps. No global feedback SE triode amps tend towards c-amps, no global feedback SE pentode amps are very much on the current side (as are PP).
Adding resistance in series pushes a v-amp towards current amp behaviour and why with things like the Fostex and the T-amps, skinny speaker wire helps things out (IIRC you have been playing with series R? ie pushing the t-amp towards being a current amp)
dave
planet10 said:
I'm beginning to see. So I take it the SI T-amp is a v-amp. Is it safe running these little amps towards c-amp behavior? It doesn't seem to be bothering it at all, and it's not running any warmer than normal.
Of course, I'm just asking a couple of very basic, general questions ATM since I am on my lunch break. Once I get home tonight, if I have the time, I'm going to read through that PDF file that Scott posted above. I glanced through it a little just now, but I simply don't have the time right now.
BTW, I just wanted to add... The more of the "inner workings" of drivers and amplifiers that I'm learning from you guys are really making it that much more interested to learning more. This is making DIY audio a LOT MORE fun for me, and I really really appreciate it!
As always, many thanks! 😉
Another question regarding series resistance (SR)...
Since I have the components on the way for inserting BSC for the 103's, will I no longer need or want SR?
Also, if SR is possible, feasible, required, wanted, etc, etc, with the BSC inserted, wouldn't I have to readjust the values of the BSC inductor and resistor to compensate for the added 2.49Ω SR?
Meaning since the 103's Re = 7.45Ω and the SR = 2.49Ω, which the T-amp is seeing roughly a 9.94Ω load.
My incoming BSC components are based off of the driver's 7.45Ω (1mH inductor & 3Ω resistor). If I were to still use SR along with BSC at a combined 9.94Ω, the BSC components should be a 1.4mH inductor and 4.1Ω resistor, correct?
Am I get out of hand with all of this or reading too much into it?
Since I have the components on the way for inserting BSC for the 103's, will I no longer need or want SR?
Also, if SR is possible, feasible, required, wanted, etc, etc, with the BSC inserted, wouldn't I have to readjust the values of the BSC inductor and resistor to compensate for the added 2.49Ω SR?
Meaning since the 103's Re = 7.45Ω and the SR = 2.49Ω, which the T-amp is seeing roughly a 9.94Ω load.
My incoming BSC components are based off of the driver's 7.45Ω (1mH inductor & 3Ω resistor). If I were to still use SR along with BSC at a combined 9.94Ω, the BSC components should be a 1.4mH inductor and 4.1Ω resistor, correct?
Am I get out of hand with all of this or reading too much into it?
The BSC replaces the SR. I use BSC on all of the Single Full Range speakers I build--and I use SS amps (1970's vintage receivers.)
Isn't this so much more fun than going to a store & bringing home a couple big boxes! Way more play value!
Cheers, Jim
Isn't this so much more fun than going to a store & bringing home a couple big boxes! Way more play value!
Cheers, Jim
chops said:
Personally, before i mucked with filters, i'd get those out of the carboard box and into a proper plywood one.
dave
chrisb said:
I just want to be sure to cover all my bases! LOL 😉
Jim Shearer said:
Thanks for your input Jim!
Yes, this is much more fun than just buying speakers like I did around the first of this year. I enjoy listening to this little system a lot more than the big one in the theater room... A LOT more!
Speaking of 70's vintage receivers, this is what one of my brother's is using ATM as the heart of his system. This thing is in MINT condition too! I'm sure you know exactly what it is...
planet10 said:
I know. This is just for fun until I make up my mind on what enclosure I want to build, and until I get my car audio system finished. Once I get my vehicle done, I'll devote all my efforts on these little guys.
chops said:
A Sansui G-something. I have one of the 30-35 watters. Ugly as sin, but supposedly not too bad sounding.
dave
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