Something stirs in the Undergrowth

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IslandPink
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Re: Something stirs in the Undergrowth

Post by IslandPink » Wed May 08, 2019 10:00 pm

God willing, on Friday .. unless I go for a walk .. then I have to go to see my mother later & stay ... in which case Sunday.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by IslandPink » Mon May 13, 2019 8:18 am

Hooray ! - in stereo properly now.
Picture looks remarkably similar except there's an extra wire to the right OB.
Found a couple of interesting things on the right channel of the 300B breadboard while I was fitting the low-pass filter. The wire from the pot wiper to the circuit was hanging by a thread, if at all connected. Likewise one of the (silver) lead wires on the existing Jensen ( Angela ) copper PIO caps was broken and only touching to complete the circuit. Might explain some intermittent problems I'd attributed to the phono connectors from the arm !
OB_Final.JPG
Next job is to build an IKEA table on which to put the phono amp.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

izzy wizzy
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Re: Something stirs in the Undergrowth

Post by izzy wizzy » Mon May 13, 2019 8:54 am

Nice one.

Just for those at the back of the class whose homework got eaten by the dog, can you summarise what amps go where via whatever crossovers/filters that's all going on there please?

Thanks.

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IslandPink
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Re: Something stirs in the Undergrowth

Post by IslandPink » Mon May 13, 2019 10:13 am

Good point, I had it in mind to produce a summary diagram, it's surprising how often I have needed to go back myself and check values for crossovers etc.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Ali Tait
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Re: Something stirs in the Undergrowth

Post by Ali Tait » Mon May 13, 2019 11:33 am

Good effort Mark, shame I'm not still working over your way.
Image[/img]

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Re: Something stirs in the Undergrowth

Post by IslandPink » Mon May 13, 2019 12:31 pm

Here is current amp/speaker set-up.
Note that the tweeter amp high-pass is only about 225Hz ( plus the transformer roll-off ) at present, so I can demo them at Owston.
QuasarAmps_May19.jpg
Good old Windows 10, can't get that picture the right way up.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by IslandPink » Mon May 13, 2019 6:29 pm

Let's try again from an older OS ... :
QuasarAmps_May19.jpg
Yes, sorry I wasn't a bit quicker with the final build, Ali - but you know me :)
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by IslandPink » Mon May 13, 2019 6:49 pm

Initial report from Nick re. Munich 2019 confirmed that the Vox Palladian/Basso did not disappoint.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by izzy wizzy » Mon May 13, 2019 7:20 pm

IslandPink wrote:
Mon May 13, 2019 6:49 pm
Initial report from Nick re. Munich 2019 confirmed that the Vox Palladian/Basso did not disappoint.
It's a funny old game this. A friend from NZ was over in Germany for business and went to Munich. I mentioned the Vox room being my fave from last year. He'd been the year before that and this and didn't rate it. He used to have Acoustat 1+1s like me, now has Tannoy 15 golds like me (but in the pro enclosure) but you get the picture, so you'd think we'd be on the same wavelength ... but apparently not :roll:

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Re: Something stirs in the Undergrowth

Post by IslandPink » Tue May 14, 2019 8:01 pm

Odd indeed.
I'll go with Nick !

Well, listening so far has been mostly excellent, sometime amazing, sometimes a bit painful.
I would say that there will still be changes to the speaker and amp crossover diagram above.
The top end from the 45 amp and the ribbons has been completely successful. I am absolutely made up with the quality of detail and tone and dynamics coming out on flutes, bells, top saxophone notes, wood blocks etc. Didn't think that level of quality was available, from the Lps or cartridge, on some things. Also the integration to the FX120's sounds really good when playing instrumental stuff.
On vocals it is somewhat different. Then I can hear that there's still a rather 'HiFi' edge to vocals despite the tone, and on some things it's quite aggressive where it shouldn't be, like early Beatles vocals. I think there is still too much HF coming from the twin FX120's , maybe in the 7/8k region. The mids need to be rolled down earlier, and maybe the zobel bit needs to contribute more to steepening the slope after 5kHz.
Lower mids and bass are rather low in the mix - more than I expected after the calcs and initial test of the Lpad.
Spatial feel & soundstage depth is excellent.
Placement within soundstage is rather soft - probably never going to be a strong point with the wide baffles. That's an acceptable trade-off.
Bass timing and evenness is OK but nothing special - a shortcoming driven by the mids sensitivity, I fear.
However the bass and lower mids still need some experimentation - I think the padding lpad resistors to the Supravox could be improved, maybe only 2R to the Supravox , I will try that. I'm still not clear on whether I should be targeting 8R or 16R for the speaker+Lpad combo.

Low-level detail and tone is superb. This the first speaker on which I've noticed pre-echo in the next room !

The low-pass to the bass/mids needs to be brought down a bit more - maybe even to 3.5k given the rising response of the FX120's after 4k.

One other thing I have not spotted is that the output transformers on the 300B amp to the Bass/mids should really be tried at 16-ohm taps instead of 8R - the OB is mostly in the 16R range. This should slightly sweeten the distortion profile for the vocals from the FX120's.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by chris661 » Wed May 15, 2019 9:51 am

Hi Mark,

Great to hear you've got the full system up and running.

Some thoughts in no particular order...

- You'll probably find the bass level/tone will improve with the L-pad removed - try putting a clip lead across the 2R5 resistor and see what that gets you.
- To track down the harshness, it might be time to find a measurement mic of some kind. I once had a compression driver on a horn which had serious problems, but only on some vocals. Turned out it was a really narrow peak in the 7kHz range. Some material didn't excite the peak, but when the wrong bit of music came along it'd drive you out of the room. One notch filter later and it sounded great. The notch took a bit of dialling in, though - too wide and you lose detail. Not enough cut and the peak remains. etc etc.
- Another potential source of harshness could be the ribbon if it's receiving much power outside its operating range. My current speakers had problems with that - I ended up with a 3rd order highpass filter, as the 2nd order one still let too much midrange through to the 0.75" dome tweeter.

Chris

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Re: Something stirs in the Undergrowth

Post by IslandPink » Fri May 17, 2019 12:36 pm

I kinda have a plan of action, but some comments below, not all at once ! -
chris661 wrote:
Wed May 15, 2019 9:51 am
- You'll probably find the bass level/tone will improve with the L-pad removed - try putting a clip lead across the 2R5 resistor and see what that gets you.
Well I started from no Lpad. I also tried no attenuation, so there has to be some sort of more sophisticated approach.
One of the things worth bearing in mind ( which I didn't when I worked out this Lpad ) is that I shouldn't be aiming for an 8R impedance for the attenuated driver. I forgot that the driver itself is from 9R to 13R near crossover, also the big cap in the series crossover ( which determines how soon the FX120's come up ) was developed by ear when the driver had just a 3R3 in series. This would mean about 12R to 15R overall impedance from the 285GMF near crossover. I'm very much hoping not to change that cap , as it's built in to the crossover structure now !
So I think currently with the initial Lpad, I've likely spoiled the crossover slope on the bass driver, leading to the lower midrange sounding a bit thin.
So the plan is to try around an overall of 12R , which will mean a higher parallel resistor on the driver. At some point the bass will sound bloated, of course. We shall see ... probably work on this today.
chris661 wrote:
Wed May 15, 2019 9:51 am
- To track down the harshness, it might be time to find a measurement mic of some kind. I once had a compression driver on a horn which had serious problems, but only on some vocals. Turned out it was a really narrow peak in the 7kHz range. Some material didn't excite the peak, but when the wrong bit of music came along it'd drive you out of the room. One notch filter later and it sounded great. The notch took a bit of dialling in, though - too wide and you lose detail. Not enough cut and the peak remains. etc etc.
Chris
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. As it is, there are very nice independent FR results for the FX120 from 'HiFiCompass' :
fx120_offaxis.png
Which I'm happy to accept. There isn't excessive peaking, unlike with some of the other Fostex drivers like the 126e ot 206e. ps The graph scale is pretty expanded on this plot. A single driver alone sounds pretty sweet.
Having read Lynn Olson's account of the Ariel crossover ( again )
http://www.nutshellhifi.com/Arieltxt2.html#top
I think plenty of potential for the harshness to be due to running the pair of mid drivers too high. At least they are physically closer than the Vifas on the Ariel, so should be able to run higher in frequency. So far I have been able to improve the vocal performance substantially by using the zobel which will have knocked down the response by about 2.5 to 3dB at 10kHz.
I don't currently fancy the idea of adding a notch filter to this series cross and the zobel. I have no idea how it will interact.
I have plenty of milage yet in experimenting with the low-pass position which will also knock down the 7-8kHz hump.
Onwards and upwards !
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by IslandPink » Fri May 17, 2019 5:06 pm

Tried 2R & 33R on the bass drivers this afternoon. Sounded good enough to complete in stereo and do some listening. Gets me back some bass level and bass lines . A touch strong in the low bass at times, as expected, but not excessive.
Next the low pass on the FX120's - definitely too much there 5k+ area when you sit on-axis to the drivers.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by IslandPink » Sat May 18, 2019 2:50 pm

Well, did some looking at the amp LP filter ( for bass/mids ) with LTSpice.
The one in place was actually 3dB down at 6.2kHz, to my surprise. I think it's my confusion ( still ) between what is 3db down and 6db down. I'm not clear when to use 10log(v1/V2 ) and when to use 20log(V1/V2) . There was also a small effect from the LP pair being followed by another cap and the grid-leak resistor of 150k. This resistor is in parallel with the resistance formed by the pentode anode resistor and the in-line resistor , so changed what would have been 5.7kHz to 6.2kHz.
Anyway... last night I altered the silver-mica cap to ground to 3900pF instead of 2400pF. This should get me around 3.7kHz low pass.
Certainly things sounded a lot better last night after getting it all running and adjusting the tweeter level.
chris661 wrote:
Wed May 15, 2019 9:51 am
- Another potential source of harshness could be the ribbon if it's receiving much power outside its operating range. My current speakers had problems with that - I ended up with a 3rd order highpass filter, as the 2nd order one still let too much midrange through to the 0.75" dome tweeter.
Chris
With transitional filter I'm using, the HP response looks like this , 3dB down at 3.7kHz and 20dB down at 1kHz. The horizontal divisions are 2dB.
HP_Ribbon_OB_May19.JPG
Listening to the tweeter alone, it seems OK , I will do more listening and decide if it needs any changes. Currently I have a sensitive & partly clogged left ear from a cold earlier this week, which is making it hard to judge things properly. The ribbon is getting max 2W , so I'm hoping that filter should be OK.
I can always keep the passive parts in place, and bring up the HP slope in the amp to form a 3rd-order slope below 2Khz if needed. That will have to be after Owston though.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by Cressy Snr » Sat May 18, 2019 3:39 pm

Are you bringing the baffles to Owston?
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