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Old 17th August 2019, 09:39 AM   #81
GM is offline GM  United States
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I think/know this amp is what you ideally need if it really has a DF = 1, so if you can't afford it, find the closest to it within your budget: Diavolo SET 300B Copper Reference 10w Integrated Amplifier – Art Audio US

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Last edited by GM; 17th August 2019 at 09:42 AM.
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Old 17th August 2019, 04:59 PM   #82
FreedomJazzDance is offline FreedomJazzDance  Brazil
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First of all, I'm very grateful for all the efforts of everybody that is dedicating some time to help me to understand the subject: amps output impedance and full range drivers, thank you very much for the patience too.

Okay, I organized my thinkings about all this subject, and concluded that is a technical consensus, that for the majority of full range drivers be powered optimally, the low damping factor aka output impedance is vital.

Instead of still asking the thoughts about every amp that I found the damping factor specs, and their respective synergy with the full range driver that I want to use, I think is a much better way I learn how to read the specs properly, and this is my main difficult till now.

So, here are my questions, there's a quote that i did not understood, and the doubt numbered bellow the quote.


1. What is the specs nomenclature that I must look on the full range drivers specifications, in order to know if will provide synergy with the amp, when considering the output impedance of the amp? and how they are the commonly variants nomenclatures and unit of measurements presented by the manufactures?

For example, the damping factor of a Luxman tube integrated amp is described as 4 Ω (and a number 1 after this, without a unit of measurement about this 1), where I have to look on the specs of the full range driver, In order to know if will be a good match? this amp will be a good or bad match with the Fostex FE0208EZ? and why?

https://www.fostexinternational.com/...df/fe208ez.pdf


Quote:
“the technical reason is that a large proportion of the drivers used with back-horns are low-Q units designed to be paired with high output impedance (low damping) amplifiers, the majority of which are SET types.”
2. What is low Q units drivers? Never heard this terminology.

Quote:
“That said, PP normally has a high DF, so output impedance is typically ~1/8 - 1/2 ohm, so doesn’t raise the driver Qts too much: Qts' = Qts + any added series resistance”
3. This sentence is like if i was trying to read a sentence in Chinese, don’t understood nothing after “so output impedance is typically...” and then goes this crazy numbers and equation..

Quote:
“Output impedance should be somewhere 0.1->1Ω”
4. I presume this is when the amp manufacturer provide the output impedance spec, correct? when they describe as damping factor it's different? how different?

I’m reading this as 0.1 greater than 1ohm, my reading is correct?

This 0.1 is what? Volt? Watt? Other measure that i have no idea?


Quote:
“5k is the impedance the output tubes see. What we want to know is what do the 4Ω (or 8 or 16) see.”
5. What exactly means to know: what do the 4ohms or 8 or 16?


Quote:
“Damping factor is sort of the inverse of output impedance. You are looking for damping factor between 2 & 10 ohms.”
6. So I presume that is common that manufacturers present the damping factor in just Ohms measurement right? still not understand why this is a good measure to be used with the Fostex FE208EZ, neither where on the driver’s specs I have to look to understand this...

Quote:
"Output impedance is very important when it comes to matching speakers.. Here for example is the “same” bass reflex box, but 3 variations designed for amplifiers with different output impedance.

http://wodendesign.com/downloads/King-of-Swingers.pdf

for SETs with output impedance < 2.5Ω (or other high output impedance amplifiers)

for SETs with output impedance ~2.5Ω (or other high output impedance amplifiers)"
7. First means: for SETs with output impedance equal or greater than 2.5Ω, correct? What means the ~ on the second statement? What differs from the First statement?

Quote:
"Technically, damping factor [DF] is the specified load impedance (speaker system) divided by the amplifier's output impedance, so dividing 8 ohms [speaker tap]/3.8 [DF] = 2.1 ohms output impedance [Rs].

Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design

Hornresp automatically does this, so using a classic reflex alignment for comparison; inputting 0.5 ohms for wiring and 2.1 ohms amp [Rs] = 2.6 ohms in the [Rg] field and with a so called matching impedance 8 + 0.5 = 8.5 ohms.

Big difference and will be more extreme loaded in a BLH, so figure you'll need a relatively large series resistor, which won't sound the same as a matching impedancooze amp, i.e. DF = 1."
8. This whole statement is totally trying to read chinese, everything, understood absolutely nothing, mostly because all the math involved, my fault of course, due my lack of repertoire on the subject.

Quote:
"I think/know this amp is what you ideally need if it really has a DF = 1, so if you can't afford it, find the closest to it within your budget: Diavolo SET 300B Copper Reference 10w Integrated Amplifier – Art Audio US"
9. While checking the specs of this amp, I noticed that they specified like this: Output Impedance as 4Ω and 8Ω. But on the statement of the friend here on the Forum, he tells me that the Damping Factor is 1, so I presume that he made a calculation to convert the Output Impedance value, that was presented in between this two values of Ohms, to Damping Factor value of measurement, correct? If yes, how I can do this calculation using a tool that is provided on the web, where I just put the number and the conversion is made? Such auto calculator tool is available?

Oh and, the Damping Factor is 1 what? what unit of measurement?

Many thanks to all! I hope that I was clear, I done my best trying to be concise and please forgive my bad english.

Last edited by FreedomJazzDance; 17th August 2019 at 05:16 PM. Reason: to organize the text better
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Old 17th August 2019, 05:03 PM   #83
planet10 is online now planet10  Canada
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Need advices, First DIY Project, Back Loaded Horn
Quote:
Originally Posted by FreedomJazzDance View Post
...that for the majority of full range drivers be powered optimally, the low damping factor aka output impedance is vital. =
I would suggest the the use of “the majority” is probably the wrong choice of words. It is true if you are talking about most Fostex FE series drivers and things like Lowthers, but their are many FRs that do not fall into this class.

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Old 17th August 2019, 05:22 PM   #84
planet10 is online now planet10  Canada
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1/ This is determined using a box modeller ideally, the formula GM has given is theone you would use to find an effective Qt for any modeler that does not include a provision for high output impedance amplifier.

2/ Low Qt, typically less than 0.3 or so.

4/ the general term damping is most often used instead of the more salient output impedance. Damping is defined as the speaker impedance divided by the amplifiers output impedance. Usually specified at a nominal frequency. Since both the output impedance & the speaker impedance are generally not flat, the number at 1k often has little to do with the LF areas where is often most noticable,

5/ the OPT takes the output of the tubes (which can typically only drive high impedances) and transforms it to drive the much lower impedance of the typical loudspeaker. 4/8/16/32 are taps that have different ratios and the idea is to connect the speaker to the terminals that most closely match the speaker’s impedance. Given that many speakers — particularily ones w XOs have widly varying impedance picking the right tap is sometimes hook it up & listen.

6/ Damping factor is Ω/Ω so has no units.

8/ it is pretty clearly stated, you are going to have to lift your knowlegde level to comprehand it.

9/ that is not the output impedance it is the “size” of suggested taps for connecting the speakers to the OPT.

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Old 17th August 2019, 07:50 PM   #85
FreedomJazzDance is offline FreedomJazzDance  Brazil
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Many thanks planet, but your explanations are still out of my knowledge..

Appreciate very much more replies in a more simple way (if possible), for a novice like me start to understand this better.
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Old 17th August 2019, 08:50 PM   #86
FreedomJazzDance is offline FreedomJazzDance  Brazil
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If my post was too long, the simple question is:

I just wanna know how to interpret the amplifier's output impedance (damping factor), in conjunction with the full range driver's specs.

What is the driver's spec that I must look, in order to know if the given amp will be a good match, or it will overdamp or underdamp the driver.

A simple hypothetical example:

Luxman LX-380 tube integrated amplifier's damping factor is described as 4Ω (and a number 1 after the ohm symbol, without a unit of measurement about this 1).

Where I have to look on the Fostex driver's specs, in order to know if this amp will be a good match, or it will overdamp or underdamp the full range driver?

https://www.fostexinternational.com/...df/fe208ez.pdf


Simple as that, I think I can't be more concise than this, I can't believe that I write massive texts, when I just could resume my doubt like this hehehe...

Best regards to all! and THANKS FOR THE MASSIVE PATIENCE with my noob questions!
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