Hi. I bought a pair of unknown speakers years ago, and they weren't ever that bad. Over time I've come to see how badly built the boxes are, and they're very ugly, so I've taken everything out and I want to do a rebuild (refurbish in a way) with those speakers. I'm hoping to end up with very tall speakers.
So I've measured the bass-midrange's - there are four of them. Their specs are not ideal, to say the least. However, they did sound quite fine, so I think they're usable.
Fs is around 72 - 80 Hz
Qms is sporadic, but more or less 5
Qes is also sporadic, but averages to something like 7
Qts is average >3
They're 5" each.
In the boxes, I discovered the simplest crossovers. I know I won't be able to use them - a single 4.7 uF capacitor in series with the (laughable) tweeters.
I have a number of drivers. These four things, the two tiny tweeters, two 1" fabric tweeters (very nice Wharfedales) and a pair of 6.5" bass-mids with about Fs=65Hz and Qts of about 2.
I've also bought a cheap set of "woofers". 6.5" 8 ohm. I'll have to measure them, but they look alright. They claim to be 200W. The build quality isn't the best I've seen, but I'm guessing they're going to provide some decent bass. I have attached photos of them. If anyone can identify them, I'll be grateful.
So, I'm thinking of using a Wharfedale tweeter, two 5" mids, one 6.5" bass mid, and a 6.5" bass per speaker. The 6.5" bass mid will be in a sealed box, and the 6.5" bass will be in a ported box (probably). The idea is to make something of the bits and pieces I have. With some clever electronics, can this work well? I'm not talking B&W, but just something that looks great and goes loud with enough bass.
So I've measured the bass-midrange's - there are four of them. Their specs are not ideal, to say the least. However, they did sound quite fine, so I think they're usable.
Fs is around 72 - 80 Hz
Qms is sporadic, but more or less 5
Qes is also sporadic, but averages to something like 7
Qts is average >3
They're 5" each.
In the boxes, I discovered the simplest crossovers. I know I won't be able to use them - a single 4.7 uF capacitor in series with the (laughable) tweeters.
I have a number of drivers. These four things, the two tiny tweeters, two 1" fabric tweeters (very nice Wharfedales) and a pair of 6.5" bass-mids with about Fs=65Hz and Qts of about 2.
I've also bought a cheap set of "woofers". 6.5" 8 ohm. I'll have to measure them, but they look alright. They claim to be 200W. The build quality isn't the best I've seen, but I'm guessing they're going to provide some decent bass. I have attached photos of them. If anyone can identify them, I'll be grateful.
So, I'm thinking of using a Wharfedale tweeter, two 5" mids, one 6.5" bass mid, and a 6.5" bass per speaker. The 6.5" bass mid will be in a sealed box, and the 6.5" bass will be in a ported box (probably). The idea is to make something of the bits and pieces I have. With some clever electronics, can this work well? I'm not talking B&W, but just something that looks great and goes loud with enough bass.
Attachments
A Qts of OVER 3?!No, that can't be, I don't believe that. How did you measure that?
I measured twice. I could have written an incorrect Qts there - it may be between 2 and 3, but it's very high. I'll post the exact measurements when I am near the speakers again (2 hours time about).
Here's an example (very similar to my real measurements):
Vrms of amplifier: 0.92 V
Test resistor: 10.1 ohm
Fs: 79 Hz
Speaker current: 65 mA at linear region
Speaker current: 42 mA at resonance
Reference value: 1.55
Measure Fh and Fl of 90 Hz and 70 Hz respectively
Qms = (Fs x reference) / (Fh - Fl) = 5.83
Qes = Qms / (reference - 1) = 10.6
Qts = (Qms x Qes) / (Qms + Qes) = 3.76
This is using this method.
If I'm doing it wrong, I'd love to know.
Firstly, where's your Re? Secondly, you don't measure the current, you're measuring the voltage over the resistor! If you did, fine - but that's the value(s) needed to verify it, not the (calculated) current. Note down the voltages, without that it's useless. To adjust the frequency, you have to increase it - to the linear range. There's no way it's already linear at 90Hz, we're talking about probably 1kHz. See, there's one massive error wich alone makes your measurement completely useless.
And to add to it, that would be the f-range where the practically all cheap digital multimeters don't measure anything usable anymore.
There are a lot of guides how to measure it, I don't want to write the 100. one and explain it too.
Finally I have to say I find it very annoying you're trying to 'back up' your measurements with a very bad meme gif because measurements and physics doesn't found on beliefs.
And to add to it, that would be the f-range where the practically all cheap digital multimeters don't measure anything usable anymore.
There are a lot of guides how to measure it, I don't want to write the 100. one and explain it too.
Finally I have to say I find it very annoying you're trying to 'back up' your measurements with a very bad meme gif because measurements and physics doesn't found on beliefs.
You wrote 70 and 90Hz:
And neither are in the linear range.
And for the osci: You have to calculate with rms, not pp. Either way, the calculation or measurement aren't correct, at the Qts check it shows a huge discrepancy, the TSP aren't consistent, these values aren't mathematically possible.
And neither are in the linear range.
And for the osci: You have to calculate with rms, not pp. Either way, the calculation or measurement aren't correct, at the Qts check it shows a huge discrepancy, the TSP aren't consistent, these values aren't mathematically possible.
Well, it is easy with ARTA but without an amplifier of any kind you can't measure anything.
How do you expect ppl to help you if you make it so hard for them? I give up. The tsp you've calculated are impossible. You did something very wrong while measuring (driver face down on the table?) or calculating. The drivers can't be that bad, air dried membrane cone and d.cap, good sized magnet.
Just measure it with the ARTA suite, you'll end up with a vastly different set of parameters.
Just measure it with the ARTA suite, you'll end up with a vastly different set of parameters.
Not familiar with Visaton accuracy, but your measurements are so far off from published that it's strongly implying you're not doing something right: W 170 S - 8 Ohm
I haven't done this longhand in 30+ yrs, but it's obvious that Ro is much too low since Ro = Rm[Fs]/Re, so no way it can be only 1.538 ohms with a 3.9 ohm Re.
Using ICG's [corrected math] Rm = 12.3 ohms, then Ro = 12.3/3.9 = 3.154 ohms is likely too low since Rx [Fl, Fh] = [Ro*Re]^0.5 = 3.5 ohms, so all things considered, time to start over from scratch unless someone's sure Rx can be < Re in which case Qms will shoot up, Qes plummet to more realistic [though still high] values.
GM
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