Model Eight speaker info (and question)

[JKent]

Some time back, there was an interesting post describing the origin of the KLH Eight driver. It went something like this:

Back in 1959 the audio consultants Bolt, Beranek & Newman had a project to equip the Senate chambers with high quality individual speakers for each Senator. So BB&N went to KLH and Kloss designed a speaker but the project fell through, so the speaker ended up in the Model 8 radio in 1960

But... it also went on to say that the driver was the same ubiquitous driver used in so many later models (later Eights, the 21, and speaker systems 11, 12,14,15,and others.

I just took a Model Eight speaker apart, and the drivers are quite different from the familiar 4" full range/mid range drivers. Photos attached show them side-by-side.

Now a question: The reason for taking this apart is there was distortion at higher volumes, in the bass area. Real "ragged" sound. The culprit seems to be ONE of the 2 drivers. It "looks" OK. Any suggestions for troubleshooting or repair are welcome. My only other options are to either buy a pair of new full-range 3" drivers, such as Tang Band, but there goes the authenticity! Or, make a new front panel and install a single 4" driver.

What to do?

 

 

[Andy]

Hi, That was my post about the origins of the Model Eight speaker - Kloss was recounting the history of KLH in the Lander interveiw in 1996.

I'm clearly wrong when I mentioned the driver found it's way into models 14,15,19 and the 21 radio unchanged. After seing your photos, the speakers are very, very different. Through the years I had talked with various collectors and many assumed the model eight driver migrated into the models mentioned above. Interestingly, in a photo of a model eight driver from a 1962 KLH ad, the driver looks exactly like the other drivers in the the other models ? ? This further led me to beleive they we4re the same. Never having the need to remove a driver from a model eight, it seemed to make sense that the drivers would be the same since the task at hands was the same...greatest frequency response from a 3" driver. The Model 15 &19 systems used frequency contouring like the Model eight. The first use of a "small" driver after the model eight would have been in the Model 11 portable phonograph of 1962.....then in the models 14 & 14B of 1963. The models 15 & 19 came along in 1964. I am pretty darn sure that KLH labeled the model eight receiver "Use only with a model eight speaker" becouse no one else was making a high quality driver in a small size that could cover the frequency range of the KLH unit.

I don't know what can be done about your damaged driver, but would think a good way to go would indeed be a vintage KLH drive such as we've been talking about. Other members may have insight into a repair, but it will likely be a tricky job.

Thanks again for posating these pictures-

Andy

[JKent]

Hi Andy

I knew that was your post, but did not want to sound like I was criticizing you As one whose professional background is in science, I know it is important to add to the knowledge base, but internet communication is so impersonal, I did not know how you would receive being "corrected." I have gotten a lot of useful and interesting information from you, and want to stay on positive terms!

Here's another interesting thing: I measured the resistance of those drivers and they are about 9 ohms each. They were connected in series, so the combined resistance is about 20 ohms! Later Eights used the single driver that was, I assume nominal 8 ohms (I'll measure a couple of them later). So were the electronics in both receivers (the early and the late Eights) the same? The Model Thirteen stereo adaptor also accepted a Model Eight speaker (or its own Model Thirteen speaker). Is it OK to use either a single-driver or a double-driver Eight speaker with the solid state Thirteen? More mysteries to ponder.

cheers

Kent

[JKent]

followup:

I stopped at Bristol Electronics in HoHoKus, NJ to pick up some items Tim Schwartz worked on for me (KLH Eight, Thirteen, Twenty-Seven, Twenty-One and a Fischer 350C tube tuner). I recommend him highly! Anyway, he looked at the 3" driver and listened for coil scraping. Sure enough--it's a coil problem. He picked up the phone and called Bill LeGall at MillerSound, who said these are not really fixable Figures--there is no easy way to get inside.

So...anyone have one 3" KLH Eight driver they want to sell? Or an entire KLH Eight speaker?

Plan B will be to use a 4" driver from a KLH 21 to replace the two 3" drivers.

Kent

[Andy]

followup:

I stopped at Bristol Electronics in HoHoKus, NJ to pick up some items Tim Schwartz worked on for me (KLH Eight, Thirteen, Twenty-Seven, Twenty-One and a Fischer 350C tube tuner). I recommend him highly! Anyway, he looked at the 3" driver and listened for coil scraping. Sure enough--it's a coil problem. He picked up the phone and called Bill LeGall at MillerSound, who said these are not really fixable Figures--there is no easy way to get inside.

So...anyone have one 3" KLH Eight driver they want to sell? Or an entire KLH Eight speaker?

Plan B will be to use a 4" driver from a KLH 21 to replace the two 3" drivers.

Kent

Hi Kent,

Thanks for not saying "Andy was wrong". Even after years of KLH collecting, there's always more to learn. It would be interesting to pull apart a late model eight speaker - in the 11,000 serial number range. There may still have been a production change - that ad I have from late 1962 or early 1963 has the photo of the model eight/thirteen driver and it looks exacty like the other drivers....steel basket with oval cut-outs and a large square magnet ??

Things were changing at KLH during this time, they were getting national press and Singer bought KLH in 1964. I'm sure there was all knds of pressure to do away with small company labor intensive assembly, such as the epoxied woofer in the Model six & seven. In addition, the change from walnut to plywood cabinets plus the change to 1 driver in the Model eight surely a mainsteaming - cost saving move....a driver change may have happened then ? More research is needed !

I say go for a vintage KLH driver to replace yours which has the voice coil problem....good luck with the repair.

Andy

[JKent]

Here's a speaker with the 4" driver. This one happens to be sn 008070--it's an extension speaker with volume control and special connector. btw Andy, I'd be interested to see that ad. Any chance of posting a hi-rez scan in the Library?

[Andy]

Here's a speaker with the 4" driver. This one happens to be sn 008070--it's an extension speaker with volume control and special connector. btw Andy, I'd be interested to see that ad. Any chance of posting a hi-rez scan in the Library?

Kent,

My printer is out of order right now, but if you email your mailing address I'l send a copy of the add to you. my email is ash2222@verizon.net.

I'll try to get a image to the library in a couple of weeks

Andy

[Pete B]

Hello gentlemen,

I'm not a KLH collector and I've known about the KLH radio but only that it is quite good as far as table radios go.

Kent sent me the 3" driver out of the Model 8 and I was expecting the usual cheap stamped frame type of driver. It is quite impressive with a cast frame and large magnet structure. Looks more like a pro driver. The voice coil seems to be badly damaged, I'd say windings coming off, probably due to overheating or age of the glue. It probably can be repaired but the labor is excessive. Any tips on how to release the glue joints are welcome here.

I don't know Meniscus well, I have spoken to the owner many years ago and he certainly seems dedicated. I've read that he repairs smaller drivers and people may want to consult him. I seem to recall reading that he repairs the small Phillips AD5060 used in Snell, Dahlquist and many other speakers. You might also try Madisound but I believe that they only do higher end drivers such as Dynaudio.

The 4" driver looks very much like the old standard Foster Fe103 made in many variations and copied by many companies. Does anyone know if there is a connection, or which came first?:

http://www.t-linespeakers.org/drivers/tunn...flex/index.html

I'm also not an Fe103 expert but here is some discussion about them:

http://www.diyaudio.com/forums/showthread....&highlight=

There is a modern version currently available that's manufactured by Fostex, the Fe103E:

http://www.madisound.com/catalog/product_i...products_id=266

[Pete B]

Here's a decent 3" very inefficient though:

http://zaphaudio.com/audio-speaker18.html

[Pete B]

I measured Kent's 3" model 8 driver.

Interesting to note the low Fs, for such a small driver, of

108.4 Hz, the low moving mass of 1.1 grams. These parameters

should help when selecting a substitute:

Fs 108.4 Hz

Vas 1.44 liters

Re 8.42 ohms

Qe .71

Qm 1.85

Mms 1.10 grams

no .25 %

SPLref 85.9 dB

Bl 3.10 T-m

Qts .52

Cms 1.96 mm/N

Pd 5.4 cm

Test condition:

Fshift = -27%

Fsm = 78.7 Hz

[JKent]

Thanks for the info Pete.

For the technically impaired (me) , how do those HiVi 3" full range speakers compare? Any other 3" full-range that look good?

Kent

[Pete B]

Thanks for the info Pete.

For the technically impaired (me) , how do those HiVi 3" full range speakers compare? Any other 3" full-range that look good?

Kent

I don't know that radio very well, is the box sealed, is there any stuffing?

Are the two 3" drivers in series for a total load of about 18 ohms?

Is the amp, solid state or tube?

The amp has FR contouring I believe, do you know if it is mainly bass

boost to make up for the small speakers, and probably a bit on the

high end since there are no tweeters?

The HiVi has much higher moving mass which indicates that it would

have a lower closed box resonance, Fc. This simply means that it will

reach lower into the bass. Here is the T&S data:

http://www.zaphaudio.com/tidbits/HIVI-B3S-TS.gif

I'm going to guess that the HiVi also has

probably about twice the Xmax of the KLH driver. both of these conribute

to lower efficiency by about 6 dB which is huge. You need 4 times the

power for the same SPL. If the amp has more than enough, and you

change both drivers then it might be fine. The lower impedance of the

HiVi's would partly make up for this, do you know if the amp can handle

a lower impedance? What is the impedance of the 4" driver, is it used

with the same amp? There is also the question of mechanical fit, I did

not check this.

[Pete B]

The other 3" that has a reputation for very flat response is the Tang Band W3-871:

http://www.partsexpress.com/pe/showdetl.cf...tnumber=264-813

The Fs is 110 Hz, moving mass is 2 g, efficiency is 87 dB which are a much better

match to the KLH 3". Note that the Xmax is only .5 mm, but it is probably similar

to the KLH. Qts is .59 also very close to .52 for the KLH. Impedance is lower than

the KLH so this along with mechanical fit should be checked.

The HiVi would be an upgrade, however you would want to check if there is enough

power available.

[JKent]

I don't know that radio very well, is the box sealed, is there any stuffing?

Are the two 3" drivers in series for a total load of about 18 ohms?

Is the amp, solid state or tube?

The amp has FR contouring I believe, do you know if it is mainly bass

boost to make up for the small speakers, and probably a bit on the

high end since there are no tweeters?

The HiVi has much higher moving mass which indicates that it would

have a lower closed box resonance, Fc. This simply means that it will

reach lower into the bass. Here is the T&S data:

http://www.zaphaudio.com/tidbits/HIVI-B3S-TS.gif

I'm going to guess that the HiVi also has

probably about twice the Xmax of the KLH driver. both of these conribute

to lower efficiency by about 6 dB which is huge. You need 4 times the

power for the same SPL. If the amp has more than enough, and you

change both drivers then it might be fine. The lower impedance of the

HiVi's would partly make up for this, do you know if the amp can handle

a lower impedance? What is the impedance of the 4" driver, is it used

with the same amp? There is also the question of mechanical fit, I did

not check this.

Hi Pete

Let me try to answer your questions semi-intelligently.

First, I bought one of those Tang Band drivers but it is not a good physical match. I think that center cone protrudes past the front of the speaker. Anyway--if I were to use that I should use 2, not one TB and one original KLH.

The KLH Model Eight speaker is acoustic suspension. The early ones had two 3-inch drivers, later ones had one 4" driver like the ones used in the Model 21 and several other speakers including the 5 and 12 (see the 1st post in this thread). In either case, the speaker (1 driver or 2) "should" have an 8 ohm nominal impedance, but as I wrote in the earlier post, the dual driver speakers seem to be close to 20.

The amp is tubes. Don't know how many watts. Here's the schematic:

http://www.somerset.net/arm/reprints/KLH8_schematic.pdf

My solution to fix the speaker system with one bad 3" driver was to make a new speaker baffle and install a single 4" driver from a Model 21. It's authentic and works, but I would have liked to preserve the dual 3" setup.

Thanks again

Kent

[Pete B]

Hi Pete

Let me try to answer your questions semi-intelligently.

First, I bought one of those Tang Band drivers but it is not a good physical match. I think that center cone protrudes past the front of the speaker. Anyway--if I were to use that I should use 2, not one TB and one original KLH.

The KLH Model Eight speaker is acoustic suspension. The early ones had two 3-inch drivers, later ones had one 4" driver like the ones used in the Model 21 and several other speakers including the 5 and 12 (see the 1st post in this thread). In either case, the speaker (1 driver or 2) "should" have an 8 ohm nominal impedance, but as I wrote in the earlier post, the dual driver speakers seem to be close to 20.

The amp is tubes. Don't know how many watts. Here's the schematic:

http://www.somerset.net/arm/reprints/KLH8_schematic.pdf

My solution to fix the speaker system with one bad 3" driver was to make a new speaker baffle and install a single 4" driver from a Model 21. It's authentic and works, but I would have liked to preserve the dual 3" setup.

Thanks again

Kent

Hi Kent,

I follow most of what you're saying here but how do you wire the two 3" drivers (about 9 ohms each) and get 8 or 9 ohms? They'ed be about 18 in series and 4.5 ohms in parallel? Is the single 4" 8 or 16 ohms or ....?

Looking at the radio schematic, I'd say it's about 2 or 3 watts, certainly less than 10. I don't think that it is enough to drive the HiVi's and have reasonable headroom. You could use the 6.3V windings with voltage doublers to power a chip amp type power amp, but I doubt you want to do something like that.

Yes, you'd probably want two of the Tang Bands and have you considered a recessed baffle to handle the phase plug clearance issue? How does the Tang Band compare in sensitivity to the original 3" driver?

I always liked the SEAS 13GMBX driver but I think it is larger than even the 4", and it would probably need a tweeter.

It is out of production but still available at Zalytron:

http://www.zalytron.com/SeasNOS.htm

[JKent]

I follow most of what you're saying here but how do you wire the two 3" drivers (about 9 ohms each) and get 8 or 9 ohms? They'ed be about 18 in series and 4.5 ohms in parallel? Is the single 4" 8 or 16 ohms or ....?

As I said... I measured the dual driver speaker at about 20 ohms.

I have a few of these and I just checked them. The dual driver systems run about 18-20 ohms. The single 4" speakers run about 9-10 ohms. That much makes sense, but when I wrote that they "should" both be 8 ohm nom, I based that on the fact that the radio receivers are marked "use only with KLH Model 8 spkr" and AFAIK the radios did not change, but early ones had 18 ohm speakers and later ones had 9 ohm speakers.

As far as the TB sensitivity; I don't know. Here are the specs if you can interpret them and determine whether 2 TBs in series would be comparable to 2 KLHs:

Specifications: Power Handling: 12 watts RMS/25 watts max *VCdia: 3/4" *Impedance: 8 ohms *Re: 6.6 ohms *Frequency range: 110-20,000 Hz *Fs: 110 Hz *SPL: 87 dB 1W/1m *Vas: .06 cu. ft. *Qms: 6.57 *Qes: .65 *Qts: .59 *Xmax: .5 mm *Dimensions: A: 3-5/8", B: 3", C: 2".

Kent

[Pete B]

Hi Kent,

Yes I saw the specs, they look close but sometimes the specs are optimistic

so I like to hear or measure the two drivers side by side.

If you have the matching radio for both a single 4" and a dual 3", you could

measure the DC resistance at the output of each radio with it turned off. This

might tell you if the secondary winding on the output transformer is different.

You might also look for a number on the output transformers to see if they

compensated for the impedance difference.

Here's an interesting alternative if you're interested in a mod:

http://www.zaphaudio.com/ZBM4.html

[Pete B]

Hello gentlemen,

I'm not a KLH collector and I've known about the KLH radio but only that it is quite good as far as table radios go.

Kent sent me the 3" driver out of the Model 8 and I was expecting the usual cheap stamped frame type of driver. It is quite impressive with a cast frame and large magnet structure. Looks more like a pro driver. The voice coil seems to be badly damaged, I'd say windings coming off, probably due to overheating or age of the glue. It probably can be repaired but the labor is excessive. Any tips on how to release the glue joints are welcome here.

I finally got around to removing the cone and spider assembly from this driver.

There was nothing wrong with the voice coil, however looking into the gap I can

see that the pole piece is off center. This was probably a production tolerance

or a defective part that slipped through. This error makes it much more sensitive

to voice coil centering and it probably shifted with age and then began to rub.

It might have had the rub from day 1, who knows?

I don't see anyway to fix this driver, which is what we concluded originally.

[Pete B]

Here's a low, low cost 3" speaker that might be of use:

http://meniscusaudio.com/rowe-wide-range-p-1077.html

[simons007]

Kent -

This thread stopped just as it was getting good. Did you ever solve the 9 ohm vs 18 ohm mystery? Did you measure the transformer resistance on your radios? I recently bought a Model 8 without a speaker and was told to use a 16 ohm speaker which I have been doing. My radio has a solid walnut case so I'm assuming it is an earlier model that came with a dual 3" speaker, so the 16 ohm should be correct but it would be nice to know for sure.

Thanks

Simon

[JKent]

Kent -

This thread stopped just as it was getting good. Did you ever solve the 9 ohm vs 18 ohm mystery? Did you measure the transformer resistance on your radios? I recently bought a Model 8 without a speaker and was told to use a 16 ohm speaker which I have been doing. My radio has a solid walnut case so I'm assuming it is an earlier model that came with a dual 3" speaker, so the 16 ohm should be correct but it would be nice to know for sure.

Thanks

Simon

Hi Simon

Apparently it doesn't make a bit of difference whether you use the single 4" or dual 3" even though the impedance is different. The tube amp handles either just fine. As I wrote to you in a PM (but repeat here in case others are interested) your best bet is a KLH speaker with 4" driver, since these are common and relatively cheap. Either a Model Twenty-One extension speaker or a Model Eleven-W speaker or similar. Another good (maybe even better) choice would be a single Model Nineteen speaker. These had TWO 4" drivers and a port, so they should have a "bigger" sound (I've been meaning to try this).

You could also use a high quality mini such as a Realistic Minimus 7 or a little Cambridge Soundworks speaker. I discuss this in my Model Eight Restoration guide here: http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=6387

Good luck.

Kent