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Single driver speakers

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Chris Firth View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris Firth Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2017 at 10:58pm
Since my last post in this thread the drivers have been changed out for MarkAudio Alpair 7s.
These are a significant step up in quality to the CHP-70s, and initially I ran the Alpair 7s as the sole drivers.
I took them round to Graham's with the Alpair 7s in this state (this was just before he got seriously pissed off with his listening space, and went about sorting out the issues that were hampering his listening experience).

Since then, I realised that I was ramping up the volume a touch too much for most of my listening, which is a sure sign to me of something not being quite right with the high end response.
So back into the frame came the high end helpers, and they've been part of the fixtures since.
I haven't even made any adjustments to the L-pad, or the elbow frequency of the Hi-Pass filter.

I have a few components to hand to move the values around slightly, but things sound so good as they are that I'm loathe to mess around for messing about's sake.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2017 at 7:33am
The show isn't over until the phase integrity sings.

I'd like to be remembered for that phrase. OK, I know it's my belief and my belief only ... Wink , but oversampling filters (developed by others than me - and for a reason...) prove that we hear higher frequencies than we do ? Confused

Utter rubbish! How can you hear higher than what you can hear when tested?

Sorry, but it isn't frequency, it's phase! The relation of phase at frequency extremes to the phase at mid frequencies, where our hearing is most sensitive.

Phase response is what we should be looking at, but where is it in the specs? Nowhere. But you can find it out easily - as far as the -3dB response goes that is.

Quite simple: 20Hz - 20kHz (-3dB points) equates to a phase response or flat phase of 200Hz - 2kHz (6 degree points). At the -3dB points the phase is out by 45 degrees, and 45 degrees is always half power, or should I say, what our ears expect it to be.

But then, in digital audio for example, the old "brick wall" filters would be multiples of 45 degrees out, but the frequency response would still measure -3dB at that particular point - totally unnatural.

Oversampling filters made it possible to place that problem far beyond that point in our hearing's range - the sound became more natural.

So are we phase integrity sensitive? It would appear so.

Having to turn the volume up too loud to get enjoyment is a sure sign of something being wrong. We should know that from the noise pollution that has built up in this world, eminating from "audio equipment" the manufacturers should be ashamed of. The authorities (customs officers) know them as boom boxes, because such products are useless at anything else. What a crap world it's turning out to be!

So Chris's ears told him the correct story. He can't hear what his HF unit is doing, but it's keeping the phase "up", and so sounds more natural, and natural is what we're designed to hear. Period.


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Chris Firth View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris Firth Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2017 at 8:58am
The thing to remember about my HF helper is that the corner frequency is 13.5 KHz, so from there there's little sound energy.
The filter is first order, which means that going backwards, one octave down is -6dB at 6.75 KHz, which is readily audible.
Coincidentally, that's the area where many wide band drivers have a peak in response that I personally cannot stand - it's where sounds can get very fierce and screechy (I find this with quite a few of the Fostex wide band units.
The Alpair 7 is pretty flat in this sensitive area.

I did sneak a peek at the response curves of the Alpair 7, and the CHP-70 (previously used driver), and they're very similar in fall off with rising frequency, and so the HF helper has been drafted back in without modification.
About the only thing I've changed is the position of the unit on the speaker cabinet - it's pulled back a touch from the front edge of the baffle, only few millimetres, and things sound really good. It's a phase thing, and carefully positioning the unit very subtly adjusts phase response mechanically, a benefit of having a tweeter mounted in a pod on top of the box.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ICL1P Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2017 at 7:22pm
Chris, what's happened to the picture of your little helpers?
Ifor
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Reflex M & ACCESSION M, CuSat50, Majestic DAC, a Proprius pair.
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