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Horswispr

Marantz Imperial 6 sound and crossovers

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I'm refinishing a pair of Marantz Imperial 6s, the "lost child" of Marantz's line in the 1970s. I actually do like the sound. It's a tad thick, but very musical, and especially good on massed chorus and female vocals. I'm wondering whether I should replace the capacitors just as a matter of course. I don't hear anything particularly wrong, but it's something I always consider. I've read that the 6s used a single 7 mfd capacitor, and I assume that's the unmarked cardboard thing in a little clasp. Anyone been inside these guys and have any comments? I like the fact that they used a post between the front and the back. Any comments about the sound? They're efficient and so are a good match with my little 17 wpc Fisher X-100B. I'll post another picture once I have them oiled up. I think they're going to look nice.

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Hi, I just finished upgrading a pair of Marantz Imperial 6 speakers. The original Imperial 6 as well as the later 6B and 6G models all used the same crossover which was essentially a 1st order 1.0 mH inductor with a 4 ohm resistor bipass shunt on the coil for the 10 inch bass/mid driver and 2nd order

(7.0 uf cap in series and a 0.6 mH inductor shunt) plus a 3 ohm resistor in series for the phenolic tweeter which also has an 8 ohm resistor shunt across it's + and - terminals. The crossover also had additional resistors via the 3 position switch to add or decrease resistance to the L-Pad to adjust the level of the tweeter. I personally did not need the felxibility of the L-pad so I left the additional resistors out of the circuit when I rebuilt the crossover. I also added another set of binding posts on the back of the speaker to allow bi-amping.

As to your question, yes the "cardboard" cap in the clasp is the 7.0 uf cap. The easiest fix would be to just purchase any high quality metallized polypropylene cap ( a 6.8 uf is OK since a 7.0 may be hard to find) . (You can also combine several values in paralel as the values add up if you want to get more precise) but Parts Express has Dayton Audio Precision 1% metallized caps which sound very good and are not very expensive ( around $10 for two 7.0 uf caps). This would be the most simple update you can do for the speakers and you could most likely use the original clasp on the crossover board to hold the new cap ( depending on the size of the new cap).

Now if you really want ot hear your speakers at their best, then I would suggest an all- out update and replace the caps, resistors, and even inductors and also the wire. The Imperial was a very good ( and also underated) speaker for its time and can sound incredibly good. I also replaced the phenolic tweeter with a New Large Advent tweeter as the phenolic ( while good for the cost) just did not measure up to the better tweeters. The 7.0 uf cap worked just fine with the Advent tweeter with no L- pad. I also bi-amped the speakers with 2 Marantz 170 DC amps and this allowed me to adjust the woofer with the tweeter levels which is essential. Running out of space but feel free to call me at 509-443-7196 if you want to visit about any of this.

Dean

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Thanks for your thorough response, Dean! I have some Dayton 5% 6.8 mfd caps here, so that's probably what I'll use when I go ahead and replace the caps. Interesting that the NLA tweeter sounds better than the original, but I'll probably just stick with the original. I can put some electrical tape around the 6.8 to make it fit into the clasp--it'll be nice not to have to break out the hot glue gun to secure the caps in the enclosure.

Any thoughts on what the KLH 6s would sound like with Parts Express's Dayton soft dome tweeters (or the phenolic tweeters)? I noticed that the Marantz Imperial 6s sounded smoother on massed vocals than my KLH 6s (already recapped with Dayton 8.2s), and it got me to wondering what tweeters would be smoother than the original KLH tweeter. Ultimately, I'll leave my KLH 6s "stock" as well, ecept for the capacitors, but it's fun to experiment.

Thanks again,

Colin

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Hi Colin- never had the chance to hear the KLH 6, but my 1st "real speaker" was a KLH 5 which I preferred over the Large Advents and AR 3A. The 6 used a similar tweeter as the 5 but I won't pretend to know if they were the same. Seems all of the H. Kloss tweeters were similar in design ( hard shellac paper) up through the NLA. I am sure a modern tweeter (or the phenolic tweeter) would change the sound but maybe not to your liking. It depends on the current crossover in the 6 and how KLH designed and voiced the bass with the treble. Do you know anything about the KLH crossover ( slopes/ etc) ?

I do a "lot" of fooling around with old speakers ( I have ADS 810s, AR 11s, EPI 100s, JBL 100s, Marantz imperial 6s, Infinity Qa and Qes, Large Advents, New Large Advents just to name a few) and I have found that in almost all cases, they can be updated with an audible improvement in sound ( to my ears) but the improvement is often subjective. Newer, modern tweeters usually measure and should sound better ( this is always subjective) as manufacturing materials and tolerances/etc have greatly improved but many folks like the "sound" that the vintage speakers produce so they may not want to change it. If the drivers and crossovers are not functioning as per spec, then it is obvious that an update will improve the speaker but if everything is working properly, then folks may be perfectly happy to leave things as they are. However, old parts do drift out of spec or corrode/etc and many of the parts were used to keep a commercial product profitable so updates may be worthwhile. For instance, most of the older speakers I modify always used functionally adequate but very inexpensive caps, inductors and high guage wire . Also, to my ears ( and also as per measurements) the upper mids/high frequencies were often shelved down compared to the bass/lower mids ( if you look at old AR literature you can see this in the response graphs as well). This gave the speakers a nice smooth sound and it is what I like about vintage speakers of yesterday but the sound is not the same as my Sound lab full rage electrostatics. I find that modifying the mid/high aspects of a vintage speaker brings it closer to the the sound of my electrostatics and sounds more natural to me. I love the deep bass and really do not mess with it .

I can get really long- winded on speaker mods so I will stop here. I also have some pretty high end systems but I get the most fun out of playing with vintage speakers and as you know from this Web site, there is a lot of passion and emotion regarding what sounds best and what should or should not be modified /etc. There are no absolutes as it all is in the ear of the beholder and that is OK. Its just a lot of fun fooling around with this old equipment and in spite of todays advancements in technology, I am always surprised at how good it all still sounds today!

BTW - if you do decide to do more with your Marantz 6 speakers feel free to contact me and also, if you ever decide to let them go, I would be interested in them.

Dean

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Dean,

Like you, I'm pleasantly surprised by how good these older speakers can sound, even compared to some good speakers from later eras. I recently had some KLH 5 here (for a cosmetic restoration) and wrote a review of them on Epinions, to which I'll post a link below. Let me know if you think I captured them well. I really enjoyed them; I found them easy to listen to over long periods of time.

I'm also doing the "mix and match" thing just to see what I come up with. Right now, my most successful project is just a pair of Dynaco A-25s with the Dayton soft dome tweeters. The sound is a little mellower than with the stock SEAS tweeters, and my friends really like them, though I prefer them on some music and the stock Dynacos on other music.

One thing I'd like to do is to "tame" the slightly bright trebles I perceive in the New Large Advents. Other than that (the bright trebles on some music), I really like NLAs. They sound dynamic and spacious to me. I tried a lower capacitor value, trying to introduce a slight "BBC dip," but it just made the trebles stand out more. I suppose I could try 4 or 6 ohm resistors on the way to the tweeters, but I haven't gotten around to it yet. My NLAs are at a friend's house right now.

Another simple project that worked well was with some empty KLH (I think they're called 26) cabinets I came up with. They're basically KLH 24s with RCA jacks, so I went with generic 8" woofers and SEAS Dynaco tweeters. Very nice! I'm using one as an extension speaker with my KLH Model 21 radio in the kitchen and it sounds great.

I'll probably hang onto these Marantz Imperial 6s, as I really like the large sound they put out. Also, they're efficient or sensitive (whichever is the proper term), and so work well with my 17 wpc Fisher X-100B amplifier.

Best,

Colin

http://www.epinions.com/review/model-5-speaker/content_605933506180

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Nice review of the KLH Model 5s, Colin. I have often had a chance to hear these speakers (the 5s) since I sold mine in 1974 and they have always still impressed me. Appears you have quite a lot of experience with speaker mods so I think we do have spomething in common besides being members of Classic Speakers Pages. Regarding the NLA tweeter, the only times that I have heard this tweeter sound harsh is with a poor crossover design or an abused tweeter. As you may be aware, the original "fried egg" Advent tweeter had a 2nd order crossover at 1000 hz. For whatever reason ( reliability issues ?), the NLA model raised the tweeter crossover point to around 1500 hz (I believe), but relied on a 1st order slope ( 13 uf cap if I recall correctly). The NLA tweeter also had ferrofluid in the gap and was a different design - to my ears, it has better high frequency extension compared to the original tweeter but cannot go down into the midrange like the original. Consequently, a lot of NLA tweeters slowly bit the dust due to loud rock and roll and that 1st order slope. ( My college roommate burned his out over time in about 2 years - it just eventually died). Lowering the crosssover point will only stress the tweeter more and cause more distortion. If I were to have New Large Advents, I would substitute the original tweeters and the original Large Advent crossover back into the NLA cabinets - you lose a little bass, but have a more accurate speaker in my opinion. The re-design of the NLAs was a compromise from Advent in the wrong direction as the woofer is almost run full range and the tweeters are getting too much power due to that 1st order slope. In my current designs ( like the Imperial 6) I use the NLA tweeter around 3000 hz with a 1st order slope (7.0 uf cap). One of my current best sounding vintage speakers uses the NLA tweeter with the EPI 8 inch bass/mid all crossed over via an electronic crossover (bi-amped) at 2000 hz - 6 db on the 8 inch and 12 db on the NLA. Very detailed and smooth and definitely a system I will keep (eventually I will sell my Sound Lab electrostatics and this is the sytem I will live with).

The only vintage system that I have a desire to play with is the Dynaco A-25. I am always on the lookout for a good pair but have not come across any locally ( Spokane WA area). This design was so well reviewed, I feel it has a lot to offer. Speaker Builder journal did a modification to it with a Dynaudio D28 tweeter and it was well-received. I especially like the A-25 design as there is no driver correction ( crossover) on the 10 inch bass/mid as it was engineered correctly for the system right from the start. Makes it very easy to modify with a high quality tweeter (as you did) or to bi-amp electronically. Still looking for a good condition pair of these!

Best regards,

Dean

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Colin

Nice project. Just one caution: Our resident engineer/speaker guru John O'Hanlon has warned against using hot melt glue on film caps--the excessive heat can damage the caps. Better to use cable ties, RTV or Goop.

btw--the KLH Model Five is a great speaker. Beautiful looking and sounding. I was underwhelmed with mine until I used a very light coat of Roy's cloth surround sealer on the woofers. Wow!

Good luck with those Imperials!
Kent

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Dean,There are lots of Dynacos floating around the Bay Area, and I've sometimes been given empty cabinets from parted out Dynacos. They're my favorite speakers to "project" because they're so simple, as you say. Have you tried putting out a "Wanted" on Craigslist? Never know what folks have in their garages. I'll keep your NLA thoughts in mind. The tweeters sounded clean in the ones I've had, just a little bright on some music. Kent, thanks for the words of caution about hot clue on capacitors. I go by "just a dab will do" and I've gotten away with it so far, but I'll be careful or look for alternatives. In KLHs I just float that last 8.2 mfd capacitor in the fiberglass nastiness.

--Colin

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I finally got my review of the Marantz Imperial 6 posted. I'm listening to them now and still like the sound. I haven't recapped them yet. I'll try to attach a picture or two. I made some frames and screens for them. I used AR-2ax style material from Jo-ann's, as that's my default. The wood for the frames came from Home Depot.

http://www.epinions.com/review/imperial-6-speaker/content_607406034564

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On 12/17/2012 at 1:15 PM, JKent said:

Just one caution: Our resident engineer/speaker guru John O'Hanlon has warned against using hot melt glue on film caps--the excessive heat can damage the caps. Better to use cable ties, RTV or Goop.

Hello Kent and All!

Long time no speak!

I realize this is an ancient thread but felt the need to say that if hot glue is your method of choice then by all means have at it. It will in NO WAY harm a modern polypropylene or film and foil type cap in ANY way

Arnie Nudell, back in the day, and Klipsch, starting around the Kg4 era, sure fell in love with it and used/use it by the barrel. 

It won't hurt a thing

Most of us SOLDER them into the circuit, yes?  Think about it

A lot of current Klipsch product and lower end JBL are still using it religiously to this day, as well as many others, too many in fact to mention

I personally don't, and wouldn't, use it but for other reasons, but damaging caps isn't one of them (and as Kent pointed out, there are "better" ways)

If you are apprehensive regarding what I am saying then take the time to simply review the tech sheet for any film type and put your mind at ease

Best to all

Craig

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On 12/15/2012 at 4:16 PM, Horswispr said:

 I assume that's the unmarked cardboard thing in a little clasp. Anyone been inside these guys and have any comments? 

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The cardboard tube with the green wires sticking out is not the cap per se, rather the cap "assembly"

It contains a nondescript mylar cap and some sand for damping/isolation

Then obviously hot wax is poured on top to seal it off

It is from the same supplier JBL used through the '70s in both "pro" and consumer models

Excellent quality build for a cap install execution, period, and especially for a speaker that fell in this price range

The mylars were of good quality for the time, but I have measured more than a few that have drifted significantly over the decades (or either they weren't that closely matched to begin with as far as tolerances go), so as always, either way, it doesn't hurt to change them out and I do so as standard practice whenever I encounter these - I would also suggest the purchase of a very basic cap tester, one good enough to at least let you know if, A - your values are close from cap to cap, and B - if you have a decent value match from cab to cab

Whenever I encounter this type I salvage the tube, wax and sand, stuff in the new poly with a .01uF film and foil by-pass and add the sand and re-seal with the wax

And by the way: JBL didn't use the very nice spring steel clamp to hold the tube like on your Marantzs - they just hot glued theirs to the masonite boards

Craig

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It's five years later now, and I'm still using my Marantz Imperial 6s as my "vintage references." I never did redo the caps (scared I'd screw things up), but I don't really hear a need to redo anything. They sound smooth and balanced, and I can listen to them for a long time without fatigue (my friends agree).  I finally brought the NLAs home, and am listening right now. They sound incredibly clean and have the tightest (and possibly deepest) bass of any of my speakers (including older AR-3as), so I will keep them. But they still sound a tad bright to me,  so I turn the treble control down to 9 o'clock on my NAD 1020 preamplifier when I listen to them.

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