Something stirs in the Undergrowth

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IslandPink
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#2386 Re: Something stirs in the Undergrowth

Post by IslandPink »

No, they're not fully 'tuned' yet and I haven't worked through the logistic planning of how to get them and the amps etc to Owston. I'd need to hire a van and make sure someone locally who isn't too old or has a bad back ( that rules out all the easy choices ) can help me load them into the van.
I'm going to bring one Yuichi horn and a ribbon from the OBs, with a crossover, to compare amps.
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IslandPink
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#2387 Re: Something stirs in the Undergrowth

Post by IslandPink »

I just sat down and did something I had been intending to do - look carefully at the FX120 response curve and the low-pass filter in the amp, and work out how the driver's rise at 6k to 8k modifies the low-pass position.
Well, there's about 2dB extra at 6kHz and 4dB at 7.5kHz. Noting those numbers and adding them on to the dropping dB levels from the approx. 3.7kHz low-pass from the amp, I get a modified -3dB point of around 6kHz if you allow a dip at 4kHz and a bump at 7.5kHz.
This means, it makes more sense to have 2.7uF/0.68mH to the tweeters to raise the HP to 5.7kHz.
Yesterday I was probably listening to it with an excess of 5k-8K response.
With 2.7uF I get a bit more attenuation of the ribbon particularly below 3kHz, so if there's some distortion, it should reduce.
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IslandPink
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#2388 Re: Something stirs in the Undergrowth

Post by IslandPink »

2.7µF heap good !
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chris661
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#2389 Re: Something stirs in the Undergrowth

Post by chris661 »

IslandPink wrote: Fri May 17, 2019 12:36 pm
I have a measurement mike and an pre-amp, but last time I tried to measure anything it just gave me odd results with Audacity, and I never got to the bottom of it.
Sounds like you're making good progress here Mark.
Might be worth downloading REW. It's free measurement software that can do frequency response, impedance, and a load of other stuff. I find in-room sweeps can end up exceptionally fuzzy due to all the reflections. Some smoothing can help with that.

Chris
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#2390 Re: Something stirs in the Undergrowth

Post by Scottmoose »

Or just gate the damn thing to remove the reflections. Job done. Is it as good as an anechoic chamber? No. Is it fine for system design purposes? Yes.
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#2391 Re: Something stirs in the Undergrowth

Post by chris661 »

True, gating can help, although it does mean you lose information at low frequencies. Then you get the, er, fun of trying to splice close-mic'd measurements, and I've found those aren't particularly reliable either: when trying to find the port tuning frequency by measuring a notch in the cone output, I could move the mic around the 15" cone and get anything from 38Hz to 25Hz.

Perhaps below a couple of hundred Hz, it's best to consider speaker + room as a system and work the result.

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#2392 Re: Something stirs in the Undergrowth

Post by Scottmoose »

True, you need to use ground-plane or similar measurements for the LF & merge into the gated for the rest of the range; on the other hand, I thought (I admit I've only skimmed the thread so obviously I am in error) that the current issue was more with the transition from the midrange to the HF, for which gated measures work fine.
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#2393 Re: Something stirs in the Undergrowth

Post by IslandPink »

This is actually a fast-changing situation here in Denbigh.
I was concerned about the HF/mid integration, but with the last mod of the 2.7µF/0.68mH ribbon cross it sounds very good indeed, and have checked on familiar stuff like Joni Mitchell 'Mingus' for reference - very sweet.
Then my concern became one of poor sounsdtaging in mids/upper bass or some phasey efects/ear discomfort. Was worrying about this yesterday and checking all polarities.
However today, during an unrelated visit to the doctors, I had ears checked and found I had the left ear half-blocked with wax and the 'good' right ear totally blocked ... apparently ! Though this does sound a bit hard to believe - however, clearly all bets are off. I'll be on the olive oil treatment now urgently ahead of Owston !!
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#2394 Re: Something stirs in the Undergrowth

Post by pre65 »

I got a tiny USB camera off Ebay so I can check my own ears.It was inexpensive. :)

Don't tell Andrew I, but Hydrogen peroxide 3% (food grade) works wonders on ear wax.
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IslandPink
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#2395 Re: Something stirs in the Undergrowth

Post by IslandPink »

Wow !
But ... is it a cheap substitute for the gas cylinders in the Sodastream :)

I'll start with the olive oil.
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#2396 Re: Something stirs in the Undergrowth

Post by vinylnvalves »

Maybe a good reason - to measure speaker responses.... and not voice them by ear :D
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#2397 Re: Something stirs in the Undergrowth

Post by IslandPink »

This olive oil thing is not much fun. Can hardly hear anything out of both ears now. Hope it'll be OK by next Saturday.
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#2398 Re: Something stirs in the Undergrowth

Post by IslandPink »

Phew !
Got my ears done this afternoon after a morning spent phoning around to find experts who weren't away on holiday this week. The bloke used that 'microsuction' thing which seems like it's actually quite powerful. I think the only thing that's 'micro' is the size of the probe at the end. There were some horrible banging and cracking sounds and some pain as he pulled all the stuff out from the eardrum area.
Also the machine seems to use water and has a sort of holding tank for the debris where it swirls around afterwards - reminded me of some TV item I saw once about colonic irrigation.
Came out listening to the massive cacophony of birds twittering and the wind blowing through the trees.

Oh, note also : I apparently have very large-bore ear canals, which is odd given I have a relatively small head and ears.
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#2399 Re: Something stirs in the Undergrowth

Post by Nick »

I apparently have very large-bore ear canals
Maybe, that's the case now, but wasn't before the sucking out process.
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#2400 Re: Something stirs in the Undergrowth

Post by IslandPink »

Everyone was surprised what was uncovered !
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