Something stirs in the Undergrowth

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IslandPink
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#2506 Re: Something stirs in the Undergrowth

Post by IslandPink »

In the meantime, i got this from my friend at work today, who was not convinced of the flatness of the ECM8000 response and went looking for data.
This graph would go some way to explain the first graph I showed with the REW testing a couple of weeks ago. The 'typical' level of these mics is about 4dB up at 10kHz.
Only problem is they vary quite a lot from unit to unit -
ECM8000_calib_various.jpg
edit : and quite likely also explains the odd 'droop' from 13kHz to 20kHz on my measurements.
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chris661
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#2507 Re: Something stirs in the Undergrowth

Post by chris661 »

Good tools ain't cheap...

I went for a Beyerdynamic MM1, which is about the cheapest I could find that came with a measured curve for each mic.

On-axis, there's a slight rise in the last octave - it's like baffle step in speakers. With the mic at 90 degrees (ie, pointing at the ceiling or floor), the response is linear. I tend to like a slightly falling high end, so point the mic at the speakers.

If your mic has a rise at the high end, it'll report larger numbers back to REW, resulting in an elevated HF response in the measurement.

Chris
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Nick
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#2508 Re: Something stirs in the Undergrowth

Post by Nick »

Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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IslandPink
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#2509 Re: Something stirs in the Undergrowth

Post by IslandPink »

Thanks. I also have the loan of another microphone, I'm just checking the data on that one.
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Dave the bass
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#2510 Re: Something stirs in the Undergrowth

Post by Dave the bass »

Nick wrote: Fri Nov 15, 2019 10:56 am ECM Calibration file
Doh, that link wasn't what I was expecting.

I was hoping for huge Germanic reverbs, stylistic album covers and a tracks from Jan Garbarek, Eberhard Weber, Keith Jarret et al.
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IslandPink
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#2511 Re: Something stirs in the Undergrowth

Post by IslandPink »

Did you forget about Colin Walcott and Terje Rypdal ?
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Dave the bass
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#2512 Re: Something stirs in the Undergrowth

Post by Dave the bass »

Pffftttt! They were inc. in the 'et al'.
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#2513 Re: Something stirs in the Undergrowth

Post by Ant »

You forgot zakhir hussain too Dave! How could you! He's not called al
Also starring Rex Hamilton as Abraham Lincoln

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#2514 Re: Something stirs in the Undergrowth

Post by IslandPink »

If you remember my comments about the double-horn -
IslandPink wrote: Sat Sep 28, 2019 2:59 pm ...
The lower part of the midrange on male vocals is OK but not as good as I hoped. Doesn't have the tone or 'snap' I had from the folded horn at one stage. Maybe the phase disjoint from the front driver to the shorter horn mouth in the 150-300Hz region is not helping.
The bass on its own is well-shaped dynamically and doesn't seem 'lumpy' or coloured - the twin horns and their carefully chosen lengths seem to be doing a good job.
The low bass is actually pretty good, despite the roll off on the sims - room gain is enough, if the rear of the horn is placed about a foot from a wall ( or bay window in my case ) .
The bass delay is audible. If you've been listening to OB or sealed boxes, it's fairly obvious. I had hoped the staged delay from front output to horn 1 to horn 2 might blend things in a more convincing way, but it doesn't ...
Well, we had a 'Pinkfest' at my house here , on Saturday. Nick arrived as the double horn was being played on Ali's EL34 amp. After about 3 mins, he said "it's a speaker of two halves really, isn't it ? " !

We had a session testing Ali's Bastani OB's, and got some very useful progress. There was difficulty in knowing the correct phase ( polarity ) to run the bass from the Behringer ( the mids and treble can go straight to a valve amp ) due to the different inversions of the signal. By ear at first it wasn't quite clear which was best, though I think we were heading in the right direction. However with the REW & UMC202 testing, it was clear there was a hole around 200-300Hz the way Ali had it set up. With reversed connections, that hole filled-in and it did sound a lot better afterwards on music. We also found a broad dip where the mid driver dropped off suddenly around 5kHz , with the tweeter only coming in around 10kHz with a single 1uF cap. With an extra 1.5uF cap to the tweeter, the response was pretty flat and that end of the FR also sounded much better. Thanks again Chris, for providing all the info to get the right kit and the set-up ; though we did need to use the correction file for the Behringer mic.
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Ali Tait
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#2515 Re: Something stirs in the Undergrowth

Post by Ali Tait »

Yes, a good and instructive day was had, thanks to Mark for hosting and measurements, and the others for being patient. :D

I'd always had niggles about these Bastanis, being sensitive to phase as I am. Now banished with phase being correct, and nice to know I was right in thinking something wasn't quite right.

Dropping the tweeter crossover has had a profound effect. I got the soldering iron out this morning and I've been playing track after track since. Amazing what an effect just adding 1.5uf can have. The speakers are so much more involving and now sound pretty seamless from top to bottom. I'm very happy with them now.

We also heard some very nice sounds from Mark's in progress OB's, in my view the only criticism was a slight boom in the bass, other than that I couldn't find anything to criticise. Great mids and a lovely treble from the ribbons. Plenty detail but a sound you could happily listen to all day. Mind, Nick's Reference phono stage was certainly helping things along. :D
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#2516 Re: Something stirs in the Undergrowth

Post by IslandPink »

Minor upgrade on wiring from crossover to mid-drivers. TQ Blue replaced with TQ Black ( some cheap s/h lengths ). In the process I found out what's inside the 'Black'.
It took me a few days to do this work in short bursts, first the left channel then the right - it was very fiddly and induced some sweating and swearing. I think there's a benefit, but it's slight.
Black_s.JPG
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IslandPink
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#2517 Re: Something stirs in the Undergrowth

Post by IslandPink »

Oh, look at these nice drivers ... can't really justify the 165's, but rare to see any of these 2nd-hand ; plus some lovely 285's ...
https://theartofsound.net/forum/showthread.php?67426-FS)-Supravox-165-2000-285GMF-Radian-475Pb-MiniDSP
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IslandPink
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#2518 Re: Something stirs in the Undergrowth

Post by IslandPink »

This may be of interest ( maybe not ). After putting in 'Black' instead of 'Blue' wires to the FX120's, I had a loss of lower mids, a slight thinning of the tone. I decided just to try adjusting the capacitor value in the series crossover to see if it was fixable that way The cap in these crossovers mainly controls the upslope ( high-pass ) of the mid drivers in the approx. 80-300Hz region.
My first efforts with three options ( 89uf, 129uF and 149uF ) this weekend suggest that 89uF is a lot closer to correct than the 129uF I had on there with the 'Blue'.
This is a fair old change, and the 129uF was arrived at by a long process of trial and error and listening, it was based on listening to timing and the specific area of the upper bass and lower mids.
I will report back as/if I refine the value. I can't help thinking I need to measure something here, but I have some other stuff to measure in the meantime.
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Ray P
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#2519 Re: Something stirs in the Undergrowth

Post by Ray P »

I wonder if the black wires will be better at lower latitudes? :lol:
Sorry, I couldn't resist!
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IslandPink
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#2520 Re: Something stirs in the Undergrowth

Post by IslandPink »

Good point - but it might limit their sales a little.
More to the above - what the cap change suggests is that there's different phase behaviour in the two cables.
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