Idintify vintage 8" double cone driver

[DrBoar]

I saw a set of speakers at a flea market. The fullrange drivers are 8" and the center of the drivers appear to have a bolt running through it. At least it looks like a hexagonal bolt head in the very center of the cone. I have never seen anything like it so I got curious

[sreten]

Hi,

Might be the very old technique of bolting a flat washer, which has a
swirl pattern in it, to the front of the pole piece to act as the spider.

Don't hold your breath, excursion will be very limited.

rgds, sreten.

[DrBoar]

Thank you sreten,
If it is like that it could either really old like from the 50s or perhaps intended for those furniture style radios that got out of fashion with the arrival of the transistor in the mid 60s.

[Jonathan Bright]

Is that photo looking down on the top of a speaker? Is the unit a Sonab?
If so (say a old SA6) the speaker could well be the Philips 9710 (twin cone).

More details of the enclosure would be helpful.

Cheers, Jonathan

[DrBoar]

Picture is top down, driver is at one end of a rectangular box. At the lower edge of the picture you can see two cone drivers, there are two more and all four face inwards and in the middle of thouse four tweeters there is dowel sticking up perhaps 10 cm.

It is not a Sonab/Carlson box as it not a 9710 (I have a pair) nor is a bass reflex as larger Sonabs were. During a 20 year period there were many loudspeakers built in Sweden "inspired" by Stig Carlsson designs. Some with skills some were put together with no knowledge at all it seems

[DrBoar]

Solved: it is a Sonab OA-5 typ2, there is a false bottom underneath the box proper and a narrow slot around it so the cabinet is vented. The diameter of the cone is about 215mm so it is very likely a 8 1/2" driver such as the Philips 9710. But what kind of nut that put a nut on the pole piece I do not know.

I wish there was a way to edit the subject line not only the body of text...

As I already have a pair of 9710 (ceramic) I will not buy them as I do not think that the drivers are that good otherwise I might have bught them if they are Alnico to do side by side comparison of alnico and ceramic

[Jonathan Bright]

The bolt is a bit of a mystery as I thought the PHILIPS full ranger had a concave copper covering on the pole piece to reduce the inductance of the voice coil and increase high frequency response. Is it possible for you to unscrew/unbolt the unit and remove it or is that not possible?

[xrk971]

I don't understand this arrangement at all. Why do tweeters radially point to dowel? What is this bolt you are talking about?
Where is the front baffle?

[Jonathan Bright]

All good questions!! These were not classic speakers. In Oz they were sold in the '70's. They were sort of omi-directional. The "front baffle" is the top of the box. The bass/mid pointed either straight up of at a slight angle. Some were roughly 2-3 cubic foot conventional speaker dimensions and stood on their "backs" and one small one was definitely a cube or as good as "damn it". The tweeters numbered between 2 and 4 (from memory) depending on the box and were designed to radiate sound for roughly 360 degrees; hence odd positioning. They were Peerless paper cone jobs (1.5"- 1.75" approx' ) I think. These units are sort of ancestors to the early Bose 901's in philosophy. (hope that doesn't offend any one!) The dowel may be acousticlly significant and assist dispersion oh high freequencies. I can't be sure of that as I am not a Sonab expert. There were several in the series (OA xx, 5, 6 so on numbers) and if you google "sonab speaker photos" you should get a good idea of the style. The bolt can just be seen through the cloth in the first photo. It may help ID the unit. An 8.25" Philips was used in some.
Hope that helps......these are an interesting anomaly in the heritage of domestic speakers.

Cheers, Jonathan

[DrBoar]

xrk971 if you look at the center of the speaker driver in the first picture, inside the perimeter of the center cone you just can make out some hexagonal structure in the very center. I thought is was a bolt but it might be nut filled with dust so it is flat as a bolt head. You can also see screws around the driver, those screws are holding a basket of fiber glass that cups the back of the driver. The idea is to reduce the Qms to get a lower Qt of the driver in the box to fine tune the bass reflex.