Speaker Experiment--

[randy@matrixq.com]

I tried an experiment today and was pleasantly surprised.

Two years ago I found a nice pair of Kenwood KL-7080s at a flea market and picked them up in a brief fit of nostalgia.  After all, they looked just like a pair of Kenwoods I had way back in the day.

I remember checking them out when I brought them home and then set them out in the patio along with a Kenwood integrated amp.  I thought they would get some use out there but just ended up collecting dust.

The other night I was doing some internet searches and found a Danish website with a spec sheet for the 7080s and about all I could decipher was the fact that these things had an efficiency rating of 102db.  That got me thinking (always dangerous).  So I brought them in to my listening room and hooked them up to the Foreplay and the 300bs. 

I was not impressed at first, but as the music played they seemed to liven up and eventually began to sing quite nicely.  I don't even have them placed optimally.  They are just sitting out there on the floor in front of the Fostex Horns. On that note, these things are philosophically the opposite of my single-driver horns.  They have a three-way crossover and six speakers.  The woofer in these monkey coffins is the size of Dumbo's posterior.  I began to wonder what a little TLC would do for these things.

Which brings up a few questions:

Question 1:  I know new speakers need break-in, but does it make sense that old speakers that have sat silent for a long time would need some sort of "re-awakening"?

Question 2: These things are 40+ years old and have electrolytic capacitors in the crossovers that are probably every bit as old.  I'm wondering if it would be worth the time/effort/expense to upgrade the crossovers.  At the very least put in some new capacitors. 

Question 3:  Are there some other concerns I should have with speakers of this age?  Visibly, everything looks almost new.  Surrounds are all paper/cloth, no foam.

Finally, has anyone else tried any of the old Kenwoods?  I remember them being quite the big deal back in the day.  I don't think they will replace my Fostex Horns but they sure beat them on price and bass extension though I feel they may trail just a little in midrange clarity.  Sure seems like their giving them a run for it.

 

[ssssly]

Yes, when speakers have sat that long I have found that you need to knock the dust off of them before they start sounding decent again. And I would definitely re-do the crossover and give a listen.

I had a similar experience with a set of Kenwoods I had had sitting in my home theater setup for almost 15 years. Hooked them up to my SEX one night for kicks and was pleasantly surprised. Have been meaning to redo the crossover ever since. Maybe when I get home from this trip.

 

[corndog71]

Replacing those old crossover parts would be a huge improvement.  You will be shocked.

A good place to go is www.erseaudio.com

 

[Grainger49]

I haven't tried to revived speakers that sat unused that long but your idea makes sense.

My opinion is that electrolytic caps should never be in the audio path.  Many others agree.  A crossover is the audio path.  So change them and if it doesn't help you have some caps for the stash.

I would rotate each driver 180 degrees so the suspension is stretched in the other direction.

Let us know how they come along.

 

[randy@matrixq.com]

Wow, great ideas and advice.  Looks like I have another project on my hands.

Also, I examined the pictures I took of the crossovers (always handy to have) and the capacitors are bi-polar electrolytics.  Sizes are 2.2 (2 of those), one 3.3 and another that I think is 4.7.  Hard to see that last one in the picture (actually, I can only see the .7 so they may be .47).  I'll have to open up the boxes before I place any orders.

I imagine the dielectric in those are pretty well shot if they are really original.

I may have some decent orange drop caps in the garage that will at least bring it up to spec.  Then if things go well, I can order some higher-end audio caps.

I like the idea of rotating the speakers.  I've been around a little longer than they have and I could use some rotation myself. 

Thanks for your time and interest.  I will post again when progress is made and try to post some pictures.  Don't hold your breath, though.  School is in session and I have 5 preps and I coach Cross-Country as well.  I just sort of disappear until after the first weekend in November.  Then I get my head a little above the water line.

 

[2wo]

Try obbligatos, to replace the the caps. Very good and cost effective...John 

 

[Grainger49]

You can buy Obbligatos at Parts ConneXion now.

 

[randy@matrixq.com]

I've heard you guys speak highly of the Obbligatos on several threads and I really want to try them out.  I will probably use them when I build my Paramours.

I've got $60 invested in these speakers right now and the 10 Obbligatos I will need will run me around $150 or more.  Not sure I want to go there on this project.  At least not on the first round. 

I've got a seduction kit on the way (well, soon I hope) and may look to put a few in there as well.

 

[Grainger49]

Parts Express has good polypropylene film caps, 200 or 250 volt rating is the lowest, for pretty cheap prices.  These are great for crossovers.

 

[howardnair]

try this link madisound.com
http://www.madisoundspeakerstore.com/claritycap-caps/

 

[intojazz]

Randall,
Sounds like a nice find. Perhaps just use them consistently for awhile and see what you think.

 

[randy@matrixq.com]

It's been months, but finally I have gotten these old Kenwoods recapped.  I ended up with a mix of Bennic and Solen caps primarily for cost reasons.  I wanted to get rid of the aging bi-directional electolytics and provide a nice upgrade without exceeding what I paid for these things in the first place.

So, I hook 'em up and queue some tunes and "Oh No!"  I thought I'd killed them.  The sound was muted, and muddy.  The voices did not sing at all.  It sounded like the lead singer was in the background.

I remembered that caps need a little burn-in so I stuck with it.  After an hour, I was back where I started and thinking this was going to be a success.  After ten hours, things started getting much more interesting.  Clear, responsive, enjoyable music was once again filling the room. 

I now have about $120 invested in the pair and I couldn't be happier.  The KL-7080s have a switch in the back to alter the crossover to taste.  You have "Clean", "Normal", and "Soft" to choose from.  I found the "Clean" sounded the most like my Fostex horns.  There is also an option for tri-amping.  Anyone tri-amping these things back in the 70s had to be the envy of everyone in the audiophile club. 

These would be a fantastic find for anyone looking for a high sensitivity (100+db) speaker set to match with a low power amp and wanted to stay on a budget.  You sure won't break the bank and you can use the savings for a good turntable or DAC.

If nothing else, I've had fun playing with this experiment and learned a little in the process.

 

[corndog71]

That is one of the craziest looking crossovers I've ever seen!  Is that whole plate the negative leg? 

I realize this is just for fun. 

Still, if it were me I would also rewire it with some better wire and maybe find out the values of those inductors.  It might improve things some more to swap them out with air core chokes.  Some non-inductive Mills resistors might improve the sound over those old sand resistors too.

 

[randy@matrixq.com]

I think the plate is so large mostly because of all the options that are offered with that monster selector switch.  There are three crossover options for single-amp use (clean, normal, and soft), then there is a position that allows you to hood up three separate amps. 

I have to believe that at least one (likely two) caps are "out of circuit" in any one of the single-amp modes.

I have a very basic understanding of RC filters and I have an even longer way to go to be an expert in crossover designs.  Some day when I have a long weekend with nothing to do, I might sit down and try to draw out a schematic for this thing.  Once I know what parts are actually in circuit for the setting I prefer, I can concentrate on upgrading those parts and paths as needed. 

A few months ago, I searched online for a schematic or service manual to no avail.  I might try again if I get the bug.  These things are pushing 40 years in age and I'm just thrilled that they sound so great and work so well after all of these years.  Not many things are built with that kind of quality now or even then.