Need info or opinion on some drivers: Isophon B25A, Sansui W100 and Pioneer PW302a - diyAudio
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Old 12th June 2014, 09:10 AM   #1
DeonC is online now DeonC  South Africa
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Default Need info or opinion on some drivers: Isophon B25A, Sansui W100 and Pioneer PW302a

Hi guys

I need some help with any info or specs on a few drivers. I got all of these in a single (AWESOME!!) deal from a local dealer (along with a pair of Peerless HE tweeters). [Thanks again, Andre. You are the BEST! ] I intend using them in a pair of 3-way, OB speakers.

I need some info on the following drivers:
1. Isophon B25A full-range drivers,
2. Sansui W100 10" woofers (from the Sansui SP100), and,
3. Pioneer PW302a 12" woofers (8-ohm versions, from the Pioneer CS-A31A speakers)

All these units are alnico. From the info I have found it seems that the Isophon B25A are full-range drivers. The only manufacturer's frequency response graph I could get was for the older Isophon P25/25/11, and they have a response plateau between 2kHz and 7kHz (see pic below). The other frequency response graph I have is from a German site (cannot remember the address). That graph is the 2nd pic below.

As far as the Sansui W100 and the Pioneer PW302a are concerned, they both come from speakers that were rated (by the two manufacturers) at circa 100dB/W. This seems a bit optimistic to me, so I was hoping someone else had some info on these for me.

I hope some of the knowledgeable folks here on the forum can help me.

Thanks,
Deon

PS. I have also bid on and won (on eBay) a pair of the Isophon oval drive-units. They look exactly similar to those Lukasz Fikus uses in his P24 Delusion speakers. I might end up going for a 4-way system, using the Isophon B25A as lower mids, but I am not sure. I think my listening distance is too close to make that viable, but we will see.
Attached Images
File Type: jpg Isophon P25-25-11.jpg (36.4 KB, 39 views)
File Type: jpg Isophon B25 freq response.jpg (40.1 KB, 38 views)
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Old 13th June 2014, 06:22 AM   #2
DeonC is online now DeonC  South Africa
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Nothing? No-one? Does anyone then have any experience with the Sansui SP100 or Pioneer CS-A31A speakers they can relate? I really hope so.

Thanks,
Deon
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Old 13th June 2014, 11:00 AM   #3
system7 is online now system7  United Kingdom
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Hi Deon. You are certainly setting a homework problem here.

I think you should be reading about Greencones since they are this sort of vintage driver set:
Greencones

And lampizator: Endorphine from Kingston Kitchen

I think that will give you some ideas.
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Old 13th June 2014, 01:25 PM   #4
DeonC is online now DeonC  South Africa
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Hi Gary

Thanks for answering. Jup, I saddled myself with some serious work. But how much fun can one guy have on his own. Gotta share it.

I was actually thinking of something like the P24 Delusion from Lukasz (Dr. Lampizator) Fikus. The Isophon oval units I got on eBay look exactly like those he uses next to the Raal ribbons. And to compound it all, I just couldn't resist another Saba, a PERMADYN 19-200-5298-U8, but one with a closed magnet. I got it for a song. Now I am just waiting as the seller is tracking down another one for me (mine has the closed magnet, almost the same as the TIGGES magnet, but not quite) and I will be buying that too. So many toys to play with. I will also be buying some phase plugs from Dave at Planet10 HiFi to fit to these. That is one of the reasons I was thinking of going 4-way- the Isophon 10" for lower mid, the Isophon oval or Saba for upper mids, and then the Peerless tweeter (and later a good ribbon- possibly the Fountek Neo3X to keep up with the efficiency of the mids).

My plan is basically this: I will be using the Sansui W100 10" woofer and the Pioneer PW302a 12" woofer in parallel below baffle step (circa 300Hz). They are both 8-ohm, so in parallel they will be 4-ohm. Then the Isophon B25A (it is rated at 4.5-ohm), and then the tweeter. Then I can also experiment using the Isophon oval or Saba PERMADYN as upper mids. Problem with the 4-way idea is that my listening distance will only be between 8ft and 9ft from the speakers, and I am not sure they will all blend together well enough. One idea I thought of was to angle the baffles on which each driver sits (see pic below for exaggerated idea of what I am talking about). I can calculate at the angle at which each baffle needs to be for each driver's center to be beaming at my listening position (taking listening height and distance from speaker, height of driver in cabinet, etc. all into consideration in the calculation), and then place each driver on it's own angled baffle. That way each will be pointed directly at the point where my ears are. Do you think this will work?

Thanks for the input so far. It is appreciated.

Deon

Side view of angled baffles:
Click the image to open in full size.
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Old 13th June 2014, 01:28 PM   #5
IG81 is offline IG81  Canada
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IMO the Isophon looks more like a wideband midbass than a fullrange.

The Sansui and Pioneer drivers are probably more like ~90-93dB/W/m. Sensitivity was not measured the same in the Kabuki-speaker era. My guess is they have somewhat high Qt and the 12" should do OK on a large OB, but probably will run out of excursion fast. The best might be to use it in an enclosure similar to the one it is originally from.

With a miniDSP or other active Xo, it would be easy to set-up an EQ'ed sealed box for either the 10" or 12" driver, low Xover, say ~100-200Hz, use the Isophon from there up to ~3-6kHz in dipole config and passively bring in a helper tweeter above this, preferably a small horn with restricted dispersion to match the Isophon cone. Roll-off the Isophon with a single coild if it's natural top-end response is not smooth. An active Xo will also mitigate sensitivity differences between the drivers, assuming correct amplifier power is provided to each. Not 100% OB as you intended, but you'll get better performance out of these given drivers IMO. The best would be to measure the TS parameters to know where you're headed.

http://sound.westhost.com/tsp.htm

Last edited by IG81; 13th June 2014 at 01:32 PM.
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Old 13th June 2014, 02:53 PM   #6
system7 is online now system7  United Kingdom
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I kinda agree with IG81 here. I think you have bought three pairs of efficient bass units.

They will all work in reflex boxes IMO. The Isophon B25A is the easiest IMO, must be an efficient 25cm bass unit. I've got one a bit like that with the Sony E44:

Click the image to open in full size.

They'll need some simple filtering before crossing over to cone tweeter or cone mid with that HF lift. I guess 1mH series, 4 ohms and 10uF shunt for a 6 ohm nominal unit to roll off at 3kHz or so.

Ought to sound rather good. Oh wait, that's not open baffle!
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Last edited by system7; 13th June 2014 at 02:56 PM.
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Old 13th June 2014, 02:57 PM   #7
DeonC is online now DeonC  South Africa
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Hi IG81

Thanks for the link on how to measure speaker TSPs. I am going to take my time and read through it carefully.

My idea is to use the two woofers (Sansui W100 10" woofer and Pioneer PW302a 12" woofer) only down to about 70Hz (I will use an active, tube-based high-pass before the amp, 4th-order or so). Below that I will have separate subwoofers to take care of the low bass. I hope they have more sensitivity than that, but I will have to measure them. The problem is that they were both used in largish, reflex enclosures, but from what I have read, neither were known to have very deep bass. Tight, but not deep. As for measuring the TSPs, I am still deciding whether to buy a USB microphone and use Room Eq Wizard, or wait for the re-release and then to buy the Dayton DATS system. I would prefer the entire main panel to be OB, but I will probably dampen the rear-wave with carpet underfelt. As far as DSP is concerned, that would be difficult. I am buying a JWN tube amplifier and want to use it to drive the entire main panel.

Another idea occurred to me. Make the bass (Sansui W100 10" woofer and Pioneer PW302a 12" woofer) quasi-cardioid. Put the Sansui W100 10" woofer on an OB and the Pioneer PW302a 12" woofer in a sealed cabinet (or the other way around, maybe). Then make the mid (or mids) cardioid as well. This might help power handling and help with room integration.

What am I going to do? Don't know, but I think it's going to be fun to find out.

Deon
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Last edited by DeonC; 13th June 2014 at 03:06 PM.
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Old 13th June 2014, 03:04 PM   #8
DeonC is online now DeonC  South Africa
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Quote:
Originally Posted by system7 View Post
They'll need some simple filtering before crossing over to cone tweeter or cone mid with that HF lift. I guess 1mH series, 4 ohms and 10uF shunt for a 6 ohm nominal unit to roll off at 3kHz or so.
Will a phase plug not help for this to a degree? I was hoping that would reduce the lift.

Deon
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Old 13th June 2014, 03:09 PM   #9
IG81 is offline IG81  Canada
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A solid reach down to 70Hz still requires a somewhat large OB. Perhaps the 12" in an H-Frame would be the best way to get down that low, might still need some EQ and I'd keep an eye out not to bottom it out. It was a stretch when I tried something similar with a sealed-box spec Foster 12".

I don't see a practical or useful way to integrate the Sansui 10" in there, not without some overly complex scheme. The Isophon may have the best midrange of all drivers you have, especially if high-passed, and I would use this one above the 12", then your tweeter of choice.

A passive Xo in the range where it would be useful to cross-over the Pioneer/Isophon drivers will likely require some LARGE coil(s), $$$. Then the issue of sensitivity mis-match still has to be dealt with, aggravated by dipole loss on the 12", the coil's resistance, baffle-step on the Isophon and its HF plateau. Both drivers having their resonance in the vicinity will also require corrective action.

Last edited by IG81; 13th June 2014 at 03:15 PM.
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Old 13th June 2014, 03:12 PM   #10
system7 is online now system7  United Kingdom
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Quote:
Originally Posted by DeonC View Post
Will a phase plug not help for this to a degree? I was hoping that would reduce the lift.

Deon
Might do. A rigid paper dustcap does increase midrange output. It sounds horrible too IMO.

Even simpler, just remove the dustcap as Troels often does. But I'd have a listen first, after all, it's a bit irreversable.

Oh wait. Is this what the 10" Isophon looks like? I don't see many options there for modifying. Looks like they've added varnish or something to the centre of the cone to raise the HF response.
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File Type: jpg Isophon P25A.JPG (38.9 KB, 25 views)
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Last edited by system7; 13th June 2014 at 03:26 PM.
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