Danieln
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EL34 tube options for more bass/tonal richness
Danieln replied to Chiliarches's topic in Talkin' Tubes
I suspect the output transformer is more probably the cause instead of the tube itself. Not enough primary inductance will cut into the bass. -
There is a Part 2 ! http://www.x3mhc.no/dokumenter/SE-v-PP-Part2.pdf Quite interesting stuff about low listening level PP with respect to hysteresis curve induced distortion. Anyone with high efficiency speakers will fall in this category most of the time. The first watt matters most, and this is where Push-Pull design relatively lacks the more.
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But Mark, you are right in the sense that in the absence of the swamping resistor, the amp will effectively see an easier load (40 ohms in many of the old klipsch xovers). it ensue that in the presence of the said resistor, the amp will work harder compared to when there is no resistor. And as you are pointing, some energy will be absorbed by the swamping resistor. The thing is that the swamping resistor (Which we should name an impedance matching resistor) is there to accommodate higher output impedance amplifiers who will have their amplitude perturbed by a high midrange impedance. Simple ohms law in fact that can easily be demonstrated. Dan
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Marvel is right, the swamping resistor is only there to make the midrange an 8 Ohms speaker, as the tweeter and the woofer already are. Dont worry, if your amp is able to generate 3 watts at 200 Hertz into 8 Ohms, it will also do it in the midrange with the same 8 Ohms without sweating. Regards, Dan
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Deang, ever heard about a Zobel?? Hint...it is used to nullify the VC inductance when required. If I remember, ALK used one of them in his Forte crossover , and other design. On the other hand, in another one, he states that he utilizes this inductance as part of his filter. It's there and cannot be ignored. https://www.trueaudio.com/st_zobel.htm
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John, thanks for the factual post. My goal is to understand. Basically you state that in order to get rid of the big 2000 Hz bump, the crossover must be lower in order to get enough attenuation at 2000. You propose around 500 Hz, which make sense. But in this case, the crossover will be stated to be @500Hz. Speaker's acoustic output is proportional to electrical signal that drives it. So when I measure voltage at the electrical crossover, that must be reflected in the acoustical response. The fact is that I measure a lower electrical crossover with the 2.5mH on my crossover. It is quite an easy measurement to do using an AC voltmeter and tone generator. So do you propose that electrical and acoustic crossover frequency are not the same?
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Wrong crossover. You can run any amp on a constant impedance one :-)
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Mark, I consider the ALK crossover in high regard. Mine is inspired by his work. But as you noted, I slightly modified, simulated, constructed and measured the result. My hearing is not so good, so i will trust a good design methodology and measurement over my hears anyday :-) I cannot stress enough that you need a constant impedance network with Single Ended Triode (SET) amplifiers or even more so with pentode (without feedback). The key is the damping factor, or say another way the amplifier output impedance. The worst offenders are the original Klipsch networks. The midrange is boosted by several DB without controlled impedance, but is flat with a constant impedance network. been there, done that! Dan
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Thanks Mike, i don't remember exactly which one is which, but as you noted it shows the phase shift. i strongly encourage you to try and confirm the measurement. You don't really need a scope, just an AC voltmeter. Use "onlinetonegenerator dot com" to drive your amp. I'm jealous of your K-horns , but in my case haven't corners to put them in. Dan
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the other using 2.5mH crossing @300Hz:
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So I rewired my crossover to use a 2.5mH inductor and precisely measured using my scope and also confirms with an AC voltmeter. I re-simulated both the 1.25mH and the 2.5mH design. The results are not surprising: Using the 2.5mH, the crossover point is lower. Simulation shows 338Hz @ -4Db Measurement shows 300Hz@ -4.8Db Using the 1.25mH, the crossover point is higher. Simulation shows 417Hz @ -2.8Db Measurement shows 430Hz@ -2.8Db It is clear that my crossover requires the 1.25mH woofer inductance. Joined are two pictures, showing equal low and mid levels and the measured period and frequency. One channel on the woofer, the other on the mid, before attenuation. Dan
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in the next couple of days, I will revert one of my crossover to 2.5mH and measure the crossover point again. Quite curious to see how this will compare to my simulation.
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Mike, exactly as you describe. I have a two channels oscilloscope. Channel one on the woofer, channel two connected to mid range before attenuator (Output of 300uH inductance). I then use "online tone generator" and find at which frequency the two channels reads the same peak to peak amplitude. This is the crossover frequency. I then measure the crossover input level. My measurement were 2.0Vpp (Woofer and midrange) with a 2.75Vpp input @ 430 Hz. 20Log(2.0/2.75) = -2.8Db very slightly off the -3.0Db (.727 vs .707) Dan
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I see Deang, L2 is about 2.5mH. The point is that part of this is in the voice coil. Else, how can I explain my measured point is 430?
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Here is the simulation schematic:
