Model 5 and 23 woofers

[day67]

Hi. Does anyone know what the internal differences are between the Model 5 & 23 woofers? I know there are magnet differences -- in shape at least -- but are the voice coils different or other characteristics that make performance different? Excursion about the same? They are often thought of as interchangable but maybe not. Thanks for any light you can shed on this.

[RoyC]

Dan,

Those that I have seen (8 in all) appeared physically identical, and had square ceramic magnets. DCR of about 4ohms and inductance of around .7mh was also consistent between the woofers from each model. All had a number between 24 and 26 written on the cones.

Roy

[Carlspeak]

>Dan,

>

>Those that I have seen (8 in all) appeared physically

>identical, and had square ceramic magnets. DCR of about 4ohms

>and inductance of around .7mh was also consistent between the

>woofers from each model. All had a number between 24 and 26

>written on the cones.

>

>Roy

Roy,

I'm working on two model 5's now. The serial numbers are 027870 (11/'69) and 003555 (6/'67). The months and yr noted are stamped on each woofer respectively. They are 10.75 inch OD with inverted roll cloth surrounds. Each has a round, ceramic magnet.

The older woofer has 25.3 written on the front of the cone. The other has 239 (I believe this is really 23.9) written on the back side. I'm pretty certain these are weights in grams of the bare cone. They are made from paper pulp cast in a mold. The back side clearly shows the roughness of the pulp that has air dried without compression. Whereas, the front side has the small dimples which must have been engraved/embossed in the solid mold. They may have helped with acoustical propagation and also, mold release.

Those older, heavier cones were needed for AS speakers and were probably designed to a specific weight and kept to tight tolerances during manufacture.

I tested both's Thiel/Small parameters and the later one had an Mms of 47.2 gms and the older one 46.3. Mms is the total weight of the cone, VC, surround. dust cap and test acoustical load. So, it all makes sense.

Re also was about 4 ohms each. This is a rather unusual reading, however. Usually, 4 ohms speakers meas in the 2.5-3.5 ohms range and 8 ohm speaker are in the 5-7 ohm range.

It's all about the music

Carl

Carl's Custom Loudspeakers

[RoyC]

Hi Carl,

You caught me wandering from the AR forum :-).

Your serial numbers are lower than the 5's I have seen. I just checked my notes again. It seems I did have one here with "23.5" written on it.

I recently tested two from a pair of KLH 23's. Both had an fs of over 30hz (33hz and 36hz)...higher than I expected. I'm used to seeing the 20hz+/- measurements of the AR 12incher.

Anyway, thanks for the info!

Roy

[Carlspeak]

>Hi Carl,

>

>You caught me wandering from the AR forum :-).

>

>Your serial numbers are lower than the 5's I have seen. I just

>checked my notes again. It seems I did have one here with

>"23.5" written on it.

>

>I recently tested two from a pair of KLH 23's. Both had an fs

>of over 30hz (33hz and 36hz)...higher than I expected. I'm

>used to seeing the 20hz+/- measurements of the AR 12incher.

>

>Anyway, thanks for the info!

>

>Roy

Hi Roy.

The Fs I got were 29 and 33. About the same as yours.

It's all about the music

Carl

Carl's Custom Loudspeakers

[day67]

Thanks Roy and Carl for the fs information. I wondered what the 5's (or 23's) might come in at. A good reference point. It seems that the square magnets on the model 5's came around 1970/1971 but this is an estimate based on what I've seen on ebay and my own experience. As you pointed out, the dates are often inked on the back of the magnet or speaker frame. I dont know if there is some correlation between the introduction of the square-magnet woofers and the newer curcuit board type cross overs -- always wondered if the cross over frequencies were also then changed to accommodate the square-magnet woofers. Probably not. Thanks again.

[RoyC]

> -- always wondered if the cross

>over frequencies were also then changed to accommodate the

>square-magnet woofers.

Dan,

I believe it is well within the realm of possibility. Crossover tweaks that appear to correspond with same-model woofer changes certainly took place over in AR-land.

Roy

[dynaco_dan]

Hi there;

I have written about my ebay visits regarding KLH 10" woofers over the past 6 or so months.

Yes, I did buy a few, from KLH Five, KLH Twenty-Three and KLH Twelve's.

When I came to this site a few years ago, I did not know much about KLH as it was poorly distributed here in Vancouver.

I did buy a used pair of KLH Twelve's here about 10 or so years ago.

Maybe mid 2006 I remember a member writing that the KLH Five's, Twelve's and Twenty-Three's used exactly the same woofers.

Their cone weight was given as a range of 23 - 25 +/- grams.

KLH Six cones were given as 18 - 20 +/- grams.

I bought several woofer's, round single magnet, dual round magnet and square magnets.

There was a writing of fires caused by woofers voice coils bottoming out and causing fires in, KLH Twenty-Three's only, I believe.

There was also a follow-up, of the dimpled rear square magnetic plate, that identifies, a factory correction.

I have seen black felt figures written on the front and also the rear of the cones.

On occasion I have also seen the numbers 5, 12 and 23 written instead of the previous weight.

I do not forsee myself ever buying anymore, with USPS dropping their economy surface fees, the price has at least doubled to have them shipped here now.

[KLHSvcMgr]

Hi Vern...

The Model 12 used a different woofer (C00132) than the Model's 5 and 23 (C00134). I am sorry but I do not remember the electrical difference between the two. The updated version of the 5 and 23 driver has the extension of the throat of the driver which can be seen as the "dimple" on the rear of the magnet assembly. The fire situation only occurred with the Model 23, the non-ported unit. However, both the 5 and the 23 started using the new driver although we didn't have any reported fire problems with the 5.

Mark

>Hi there;

>

>I have written about my ebay visits regarding KLH 10"

>woofers over the past 6 or so months.

>

>Yes, I did buy a few, from KLH Five, KLH Twenty-Three and KLH

>Twelve's.

>

>When I came to this site a few years ago, I did not know much

>about KLH as it was poorly distributed here in Vancouver.

>

>I did buy a used pair of KLH Twelve's here about 10 or so

>years ago.

>

>Maybe mid 2006 I remember a member writing that the KLH

>Five's, Twelve's and Twenty-Three's used exactly the same

>woofers.

>

>Their cone weight was given as a range of 23 - 25 +/- grams.

>

>KLH Six cones were given as 18 - 20 +/- grams.

>

>I bought several woofer's, round single magnet, dual round

>magnet and square magnets.

>

>There was a writing of fires caused by woofers voice coils

>bottoming out and causing fires in, KLH Twenty-Three's only, I

>believe.

>

>There was also a follow-up, of the dimpled rear square

>magnetic plate, that identifies, a factory correction.

>

>I have seen black felt figures written on the front and also

>the rear of the cones.

>

>On occasion I have also seen the numbers 5, 12 and 23 written

>instead of the previous weight.

>

>I do not forsee myself ever buying anymore, with USPS dropping

>their economy surface fees, the price has at least doubled to

>have them shipped here now.

>

[dynaco_dan]

Hi Mark;

What a revelation, thank you.

I guess I need to see what version of woofer is in a KLH Twelve enclosure now.

I went into those auctions based on what I read here, as gospel, carved in stone.

It was mentioned that the KLH Twelve, Twenty-Three and Five have a marking, either those numbers or cone weight, 23 - 25 gram's.

It looks like it's never to late to learn, an expensive lesson too, maybe.