Something Stirs in the Workshop

Dedicated to those large boxes at one end of the room
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IslandPink
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#166 Re: Something Stirs in the Workshop

Post by IslandPink »

I found it hard to find drivers that were good enough, most cones are too heavy duty and don't sound like a planar or a horn at low levels. It's back to the usual light full-range cones but trying to avoid the breakup problems, which do, to be fiar, happen higher-up.
I am actually looking vaguely at resurrecting the 'Undergrowth' project with a FE167E ( loaned ) on a small box like the 2nd Purifi enclosure ( small slot port ) if for nothing else than a specialised mono set-up for listening to guitar music.
"Once you find out ... the Circumstances ; then you can go out"
vinylnvalves
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#167 Re: Something Stirs in the Workshop

Post by vinylnvalves »

Finally got around to finishing off the second es250 horn. Personally I cannot qualitatively assess a single channel, needs to be stereo. They have merit, a different presentation to my midrange AMT’s. They bring the musician into your room, opposed to taking you into the music venue. Not as much air, but other qualities. Whether they are missing to top end sparkle or not, I would need to add the super tweeters to see if > 12k is important or not. Maybe it’s time to buy a couple of matched capacitors, to see if I can improve the SQ further, than the current lash up.

Having two options, adds a dilemma of what to take to the WAM show later this year.
Was hoping to be able to get Chris around for measurements and a second opinion. I may have to have a bake off in the next month or so to let others decide...
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#168 Re: Something Stirs in the Workshop

Post by vinylnvalves »

Been doing some further measurements and comparisons. However I don’t know which sounds better, as I am currently unable to listen to music as I seem to have an issues with my hearing post Covid. Hopefully when get I get to see a GP things might improve.

Previously I had compared the es250 horn with the midrange AMT in the OS horn. I have now compared the ES 250 horn with the mid range AMT “nude”. The ES250 has a back chamber and 40mm of acoustic foam to attenuated the back wave a little

Both arrangements measure well, bit more floor bounce with the ES250 as mike is further from the floor. However I suspect the OB AMT drivers won’t be dynamic. The ES250 horn with the pair of GRS planar drivers is 98db efficient.

No DSP manipulation, just plain LR4 crossovers and efficiency matching.



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vinylnvalves
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#169 Re: Something Stirs in the Workshop

Post by vinylnvalves »

Time is marching on for getting something ready for the WAM show. I have been revisiting a few of my previous projects, to see if I missed something worth resurrecting.
I have been playing again with the Beyma 12p80nd, this time in a U baffle ( also it was loosening up too compared to last time)
It seems to have more merit than before, with midrange horn qualities now developing. So I cobbled it together with the Beyma TPL. They seem to work well together. The plan will be to cross at 1250hz to match the dispersion of the 80 deg horn.
So I have come up with this idea...
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Haven’t decided yet whether the midrange driver is dipole sealed or Cardioid, leaning towards the later. But the cabinet will have a removable back so I can experiment.
The12p80nd is only good for 100hz, so need some LF helper. I have 4 Seas L26R04y drivers, that I know work well in an open baffle sub ( Orion 4 sub & LX521) I plan to use. I plan to use these drivers facing forwards and am matching the crosssectional areas front and rear accounting for the magnet to hopefully better balance driver asymmetric.

Any thought before I start making sawdust....
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#170 Re: Something Stirs in the Workshop

Post by vinylnvalves »

Been measuring these today, custom OS horn profile for the Beyma TPL, paired with the Beyma 12P80nd driver. Machined into a 45mm thick birch ply front panel. With a 50mm radius edge to reduce diffraction.

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.

One of the challenges with using the 12P80nd, is it’s a 0.19 qts driver. So poor LF extension, my modelling showed the baffle step may make the situation worse. I ignored it assuming the DSP will fix it. :D
The measured response wasn’t what I was expecting- better. I tried adding a 2.3 ohm resistor in series to improve the f3 point. To my surprise very little affect- simulation suggesting a 6db improvement. Not sure what’s going off ….. help please.
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Further measurements of the Beyma TPL, shows a nice clean response well below 1000hz, which is good as this was the intended crossover point.
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vinylnvalves
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#171 Re: Something Stirs in the Workshop

Post by vinylnvalves »

No real challenges matching levels as both 99db plus drivers.
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The challenge will be how to match a subwoofer below it crossing at 100hz.

I tried a cabinet with side vents…. To get some cardioid, not sure if I over stuffed them, but little response difference between them breathing and blocked off.
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IslandPink
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#172 Re: Something Stirs in the Workshop

Post by IslandPink »

I feel your pain ... and admire the hard work you're putting in.
However with that driver I feel it's just a case of 'You can't get there from here' .
If you want real high-90's efficiency then the classic approach is with a 15" driver with a higher Qts.
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vinylnvalves
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#173 Re: Something Stirs in the Workshop

Post by vinylnvalves »

Wouldn’t want to cross a 15” above 800 hz as would be beaming - like hell
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IslandPink
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#174 Re: Something Stirs in the Workshop

Post by IslandPink »

OK then, smaller driver and accept less efficiency :)
There are no easy answers in this game.

The only future plan I can see for my horn-based system now is a FE167E on a sealed or low, slot-ported box. At least i have reliable output down to 500Hz with the 288 on the Yuichi.
Are you really certain that you can't stand the beaming ?
I see that this subject (of matching dispersion angle) seems to have taken over the DIY speaker discussions in recent years. But we are not building a PA system.
There are plenty of floor-stander speakers out there with 6.5" bass units crossing over to dome tweeters at 2 to 2.5kHz, that are entirely successful in terms of listenability. Surely that's the same thing ?
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vinylnvalves
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#175 Re: Something Stirs in the Workshop

Post by vinylnvalves »

I think there is a solution with a 12” driver crossed at at 100hz to another unit, let’s call it a sub. Yes the BBC did design shaded drivers which can allow a 15” driver to be usedhigher. I have tried the concept, cloning the JBL shading guide. I didn’t like what it did to my 15” supravox sound wise. You might be right about directionality…. but this is the first horn I have designed which sounds the same a good 45 degs off axis.

Hampered by only having one, which I find hard to make a qualitative sound quality assessment about, i need stereo. Need to get some LF sorted as obviously it sounds thin without the lower octaves.

Where it’s good enough to replace my existing AMT loaded horns which cover from 300hz to 8khz is another matter.
iansr
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#176 Re: Something Stirs in the Workshop

Post by iansr »

Everything I’ve read about the TPL suggests you want to be crossing no lower than 1200 and ideally at 2k, so your horn must be having quite a positive impact.
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simon
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#177 Re: Something Stirs in the Workshop

Post by simon »

IslandPink wrote: Sun Aug 06, 2023 6:16 pm However with that driver I feel it's just a case of 'You can't get there from here' .
That takes me back Mark, it's 1985 again!
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#178 Re: Something Stirs in the Workshop

Post by iansr »

what do Elvis and REM have in common . . . . ?
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simon
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#179 Re: Something Stirs in the Workshop

Post by simon »

They're American :D
iansr
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#180 Re: Something Stirs in the Workshop

Post by iansr »

Unsurprisingly, no prize for that !
"Its good enough for Government work."
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