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Multi-Way Conventional loudspeakers with crossovers

Isophon P 203S Alnico speakers: please help me!
Isophon P 203S Alnico speakers: please help me!
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Old 1st December 2016, 01:47 PM   #11
Grasso789 is offline Grasso789  Germany
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Why sad? These are good parts, the tweeters, too. Equivalent Volume is prolly at least 50 liters, and a 70 liters box provided very deep bass, but if space is short, we need to use a smaller box equipped with mechanical damping via the stuffed bass-reflex duct. Mechanical damping is not in any way flawed, in fact most of the good HiFi stuff from the fifties and sixties, before dome tweeters and bass-reflex were invented, was done with mechanical damping.
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Old 1st December 2016, 01:57 PM   #12
Sonce is offline Sonce  Macedonia
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Peters8 wrote:
"(just a clarification, guys,: VAS parameter is not correct, infact the correct one is 20/30 ltr.)"
so I recommend closed box. But if the correct value is Vas=68 liters, than aperiodic box as you described is better option indeed.
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Old 3rd December 2016, 01:12 AM   #13
Peters8 is offline Peters8  Italy
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Quote:
Originally Posted by Grasso789 View Post
Why sad? These are good parts, the tweeters, too. Equivalent Volume is prolly at least 50 liters, and a 70 liters box provided very deep bass, but if space is short, we need to use a smaller box equipped with mechanical damping via the stuffed bass-reflex duct. Mechanical damping is not in any way flawed, in fact most of the good HiFi stuff from the fifties and sixties, before dome tweeters and bass-reflex were invented, was done with mechanical damping.
Thank you so much, dear Grasso789, for your precious encouragement and support!
You're very kindness!
Please, be patience with me...I don't speak english so well, so there's some thing I can't understand perfectly: for example, could you explane me (if that doesn't annoy you, of course) what is the mechanical damping?
Thank you very much for your collaboration
Regards!
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Old 3rd December 2016, 01:18 AM   #14
Peters8 is offline Peters8  Italy
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Quote:
Originally Posted by Sonce View Post
Peters8 wrote:
"(just a clarification, guys,: VAS parameter is not correct, infact the correct one is 20/30 ltr.)"
so I recommend closed box. But if the correct value is Vas=68 liters, than aperiodic box as you described is better option indeed.

Hi Sonce, first of all, thank you for your reply!
I can assure you, the correct Vas value is 20/30 Liters.
That is clearly specified in each isophon manual from 1968 until 1980.
Best regards!
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Old 18th August 2017, 06:31 AM   #15
Fernando R is offline Fernando R  United States
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The volumes specified in the Isophon Catalogs were not Vas but recommended enclosure volumes. Isophon did not publish Thiele/Small parameters till the 80s. I had a PSL 245/35 in the early 70s and the recommended Volumes were 40-60 Liters. These were highly compliant drivers designed for air suspension which was the standard at the time. The PSL 245 had a resonance in a 40 liter box of 64 Hz with a Qt (in the box) around 1.0
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Old 18th August 2017, 08:58 AM   #16
system7 is offline system7  United Kingdom
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What a very strange thread!

Some old Isophon P203 woofer. Maybe this:

Quote:
Impedanz (Zmax): 4 Ohm
Leistung (Pe):
Membranfläche (Sd): 240 cm²
Resonanzfrequenz (Fs): 35 Hz
Gleichstromwiderstand (Re): 3,8 Ohm
Schwingspulen-Induktivität (Le):
Mechanischer Q-Faktor (Qms): 1,98
Elektrischer Q-Faktor (Qes): 0,78
Gesamtgüte (Qts): 0,56
Äquivalentvolumen (Vas): 68 l
Membranverschiebungsvolumen (Vd):
Antriebsfaktor (Bxl): 5,13
gesamte bewegte Masse (Mmd):
effektive bewegte Masse (Mms): 24,5 g
I can do the sums. Vas and Qts gives you the critically damped Qtc=0.707 box size. I make it twice the Vas here. Well you're not going to do THAT. People seemed to use about 50L back in the day. Maybe with a few holes drilled as a sort of aperiodic. Notice the single cap to a 4" sealed-back cone tweeter in the Norelco. The bass might have a coil, not sure.

25L would give you a box Qtc around 1.0. The Heybrook HB1 with a Vas of 81L and Qts 0.7 driver was like that. Made for a slightly lumpy bass.

I'd be surprised if this driver still works, TBH.
Attached Images
File Type: jpg Isophon P203 Norelco NE-531.JPG (13.3 KB, 37 views)
File Type: jpg Telefunken TL-80 Isophon 203.JPG (19.3 KB, 37 views)
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Old 18th August 2017, 09:09 AM   #17
planet10 is online now planet10  Canada
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Isophon P 203S Alnico speakers: please help me!
I may have one of these, i certainly have run across a number of them. They were all used more or less open baffle in German consoles.

All of these passed thru before i was measuring T/S but here is an impedance plot.

dave
Attached Images
File Type: gif isophon-p203-70-18-imp.gif (13.8 KB, 39 views)
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Old 18th August 2017, 09:55 AM   #18
system7 is offline system7  United Kingdom
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Seems to confirm the 3.8 DCR, Dave.

I wonder if AlNiCo magnets are all that special?

That Norelco is not disimilar to stuff I grew up with on a Valve Radiogram. Sounded very good.

I've always put the good sound down to lively cones and those old cone tweeters. Crossovers were rubbish by modern standards.

My workplace has a lot of old interesting junk in the basement. A complete Steepletone HiFi from about 1972. With Garrard SP25 turntable. Some very retro 7" ELAC ceiling line speakers with cloth surrounds and small voicecoils. Bit like SABA Greencones really, and they are a bit of a legend.

I've been tempted to have a go at the ELACs.

Amazing what people used to do back in the day.
Attached Images
File Type: jpg EMI 13x8 bass plus cone tweeter.JPG (51.2 KB, 34 views)
File Type: jpg EMI 13x8 Elliptical Bass.JPG (35.7 KB, 32 views)
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Old 18th August 2017, 10:24 AM   #19
voltwide is offline voltwide  Ireland
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Quote:
Originally Posted by system7 View Post
Seems to confirm the 3.8 DCR, Dave.

I wonder if AlNiCo magnets are all that special?

That Norelco is not disimilar to stuff I grew up with on a Valve Radiogram. Sounded very good.

I've always put the good sound down to lively cones and those old cone tweeters. Crossovers were rubbish by modern standards.

My workplace has a lot of old interesting junk in the basement. A complete Steepletone HiFi from about 1972. With Garrard SP25 turntable. Some very retro 7" ELAC ceiling line speakers with cloth surrounds and small voicecoils. Bit like SABA Greencones really, and they are a bit of a legend.

I've been tempted to have a go at the ELACs.

Amazing what people used to do back in the day.
I loved my PSL203 in a DIY 15l shelfbox. That was in the early 70ies. The foam surrounding passed away in the 90ies, so I wonder whether any of these are still working.
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Old 18th August 2017, 10:34 AM   #20
Kay Pirinha is offline Kay Pirinha  Germany
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Quote:
Originally Posted by voltwide View Post
I loved my PSL203 in a DIY 15l shelfbox. That was in the early 70ies. The foam surrounding passed away in the 90ies, so I wonder whether any of these are still working.
That's not uncommon. Any foam surrounding may pass after some decades, due to inevitable degeneration of it's PU material. Fortunately, we can repair these issues rather easily in speakers with nowadays' common diameters.
Best regards!
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