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Multi-Way Conventional loudspeakers with crossovers

Classic monitor designs?
Classic monitor designs?
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Old 14th September 2017, 02:22 AM   #551
Ro808 is offline Ro808  Netherlands
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What's the whizzer woofer in the last picture?
It reminds me of a BG-20 (the glossy coating on the surround), but it appears to be much bigger.
Did you remove the dustcap?

Last edited by Ro808; 14th September 2017 at 02:25 AM.
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Old 14th September 2017, 02:31 AM   #552
zman01 is offline zman01  Bangladesh
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Classic monitor designs?
Ro808,

IIRC the big woofer in Bigun's build is an Audio Nirvana 15".

Edit: Found the build thread - A Big'un - the Audio Nirvana Super 15
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Old 14th September 2017, 03:13 AM   #553
Ro808 is offline Ro808  Netherlands
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Thanks, Audio Nirvana occurred to me, but I didn't know they produce woofers larger than 8 or 10". A couple of years ago I was tempted to buy a pair of Audio Nirvana 8" drivers for 100, but wasn't sure about the quality of these.
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Old 14th September 2017, 03:42 AM   #554
system7 is offline system7  United Kingdom
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Those are some serious 12-15" subwoofers, Bigun:

Click the image to open in full size.

I suppose they project the sound very well on the big baffles. What Troels Gravesen describes as "Comes with a room" on his huge "Poor Man's Strad" project:
Poor Man'

I'm not too fanatical about big bass.

Click the image to open in full size.

The bigger pair is just closed box without much bafflestep, ie a small bass coil. Close to the wall, you shouldn't need bafflestep. And too much bass just annoys me. My brother in law describes bass as a sort of foundation to the sound, an acoustic which conveys the concert hall, and I think he is right.

I ought to spend some time explaining how BW3 works, because I'm not sure people really get what it does. Your comment about the poor PMC FB1 (famous old vifa metal dome, isn't it?) dispersion might then make more sense. See, phase aligned like LR2 and LR4 is fine on axis, but above and below axis the two drivers lose phase coherence, and the sound changes. This is the 3dB power hole I often describe.

Both the speakers in my room are butterworth designs. 90 degree phase at crossover, but nevertheless flat frequency response on axis. They have more power at the crossover point, which makes them more consistent off-axis. There is a higher power lobe above axis, IIRC, but this is offset by the poorer dispersion of the bass, so it sort of works out. The fact is you don't get the huge nulls off axis like you do with phase aligned designs. And this is one of the musical secrets of most BBC and KEF designs.
Rogers Loudspeakers › LS5/9

In fact the impedance is remarkably flat too. Which made them valve-friendly. Another interesting aspect is with, say, LR2, you might tune the bass filter to 2kHz, and the tweeter filter to 5kHz for a 3.5kHz XO. With 3.5kH BW3, both filters are tuned to the same 3.5kHz frequency. Bafflestep is a separate matter, but there are ways to do it.
Attached Images
File Type: jpg PMC FB1.JPG (29.7 KB, 175 views)
File Type: png Third Order Theoretical values 3kHz.PNG (18.6 KB, 175 views)
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Old 14th September 2017, 11:30 AM   #555
Ro808 is offline Ro808  Netherlands
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3500Hz will do in a 5 or 5.5" woofer and 1 or 0.75" tweeter mini monitor, but I would prefer an 8 or 10" with 1.25" tweeter HES crossed at 2KHz or - with waveguide - even lower. If you want full range, 40Hz and up.... 1 step closer to Royal Albert Hall

XRK971's FAST is an appealing alternative, but with sensitivity most likely <90dB.

Last edited by Ro808; 14th September 2017 at 11:43 AM.
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Old 14th September 2017, 01:58 PM   #556
Ro808 is offline Ro808  Netherlands
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@Bigun, I jumped through your build thread and I do like the concept of 1 big driver in a large cab. As usual, a few questions arose:
- How does that whizzer / phaseplug perform in relation to the lower (cone) spectrum? I would suspect some cuppy, beamy characteristics.
- VAS is very high and xmax very low, which implies a very, very large cab or an OB as was mentioned in the thread. I wonder how these AN drivers would handle high power, bass heavy input.
- As I understood, you didn't measure these drivers in the cabs, which would be the only objective indicator on performance.
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Old 14th September 2017, 05:38 PM   #557
system7 is offline system7  United Kingdom
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In the end, there is no debate about the compromises of domestic loudspeakers. We make compromises. The facts of it.

My brother-in-law has always liked the good sound. He generously gave me his old Radford STA-25 valve power amp. Being a mere noob, back in the 1960's day, I really didn't appreciate you had to set the grid bias up for low distortion.

And valves really never liked a complex-impedance reflex load. Happier with closed box.

Where's he at these days? When he was confined to his bedroom during a painful cancer recovery, he was listening to Joachim Gerhard's splendid Manger design. Something quite amazing about those speakers, but COLD.

These days, he has a splendid 5 unit MTM Scanspeak/RAAL surround sound system, supplemented by huge 4X 15" bass units built into the wall. A subscription to the Berlin Philarmonic's high quality feed doubtless adds a lot.

TBH, it is SO GOOD that you just get totally involved. BBC Music - 20 moments to remember the Proms 2017 by. Check out #8, Anoushka Shankar's concert for the real deal.

Last, but not least, is BW3 dispersion. I like it.
Attached Images
File Type: jpg Manger_zerobox_103_loudspeaker.JPG (32.5 KB, 149 views)
File Type: jpg MTM Scanspeak RAAL Ribbon Selah Audio.JPG (35.7 KB, 158 views)
File Type: png BW3 Power response.PNG (26.7 KB, 47 views)
File Type: jpg Radford STA 25 power amp.JPG (58.8 KB, 150 views)
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Old 14th September 2017, 08:28 PM   #558
Ro808 is offline Ro808  Netherlands
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My brother listened to some "high end" (read expensive) speakers with Manger drivers on more than 1 occasion, he defined the sound quality as "ridiculously bad". These were not the speakers designed by Joachim Gerhard.
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Old 15th September 2017, 12:37 AM   #559
Ro808 is offline Ro808  Netherlands
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Low output SET amps are not the best companion to BR loudspeakers of modest size, that's a fact. Even more so if the impedance shows serious drops.
Solution: step up in cone size (HES) and you might switch to 16 Ohm drivers. Another option: feed the bass with class D.

Last edited by Ro808; 15th September 2017 at 12:40 AM.
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Old 15th September 2017, 02:28 AM   #560
system7 is offline system7  United Kingdom
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AFAIK , the Radford STA-25 was not a SET amplifier. My version was not exactly the same as this one:

Click the image to open in full size.

With valves you did best make a guess at speaker impedance, so 4-8-16 ohm taps. This mainly affected efficiency, but because of the output transformer which worked less well at extreme bass frequencies, you just didn't get huge damping factor on the bass. Mine differed in having an adjustable pair of potentiometers to set the grid bias, aka output crossover bias. But if we look at a schematic, I see some global feedback. Which is less SET and more mainstream negative feedback.

The pre-amp and FM tuner were both transistor designs. So clearly the magic was in the fast valve output stage.

TBH, I puzzled over valves for years. It seemed like subsequent transistor designs were a lot worse. But we now know that early transistor designs suffered from transient intermodulation distortion. Which was simply that output transistors ran out of gain at high frequency, so feedback stopped working properly. More modern designs like my Rotel transistor amp pretty much do what it says on the box. 0.1% distortion into 8 ohms up to 20kHz.

The exact Norton-Thevenin mathematical theory tells us that, WITH A FLAT IMPEDANCE LOAD, voltage and current devices get to the same place. So my interest these days is getting a flat impedance!
Attached Images
File Type: jpg Radford Valve Amp MkII.JPG (95.2 KB, 21 views)
File Type: jpg Rotel RA-931 and Rotel RCD-965-BX Amp and CD.JPG (14.1 KB, 273 views)
File Type: png Norton-Thevenin Equivalent Drive.png (20.1 KB, 21 views)
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