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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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  • 2 months later...

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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  • 4 years later...
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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  • 4 years later...

I found Horswispr's review on the Wayback machine, hope you don't mind:

 

Pros: smooth, warmish sound; attractive real walnut veneer; excellent with choral music; relatively inexpensive

Cons: a bit thick in the lower midrange on some music; fairly large footprint

Marantz Imperial 6s are sleepers among loudspeakers from the 1970s. They are large, ported two-ways that didn’t sell as well as the three-way Marantz Imperial 7, but are now thought to be much better speakers than the 7s. The Imperial 6’s tragic flaw was that they were tonally neutral and didn’t stand out in a showroom full of speakers crying out via boomy bass and lower treble peaks to be taken home. There’s some interesting information on the internet about the Imperial 6 and Imperial 7, and some comparisons conducted by Marantz’s designers between their Imperial 6 and the best-selling Large Advent Loudspeaker. Google “Marantz Imperial 6 Large Advent” and Patrick Hart’s article “Loudspeakers: When is Good Enough, Enough?” will show up.

A pair of Imperial 6s recently showed up at my house for refinishing, so of course I had to give them a listen. Each Imperial 6 is approximately 25 ½” tall x 14 ¼” wide x 11 ½” deep and weighs about the same as a KLH 6, or about 32 lbs. The Imperial 6s are basic ‘70s boxes, resembling KLH 6s and AR-2axs in overall appearance. The cabinets are finished in real walnut veneer that appears to be comparable in quality to that used by Acoustic Research, KLH and Advent during the same era. The pair in my possession has no grilles, but I beleive I read somewhere that the original Imperial 6 came with dark tan cloth grilles. Some Marantz speakers (possibly including the Imperial 7) came with gaudy foam grilles that tend to rot over time. I think the Imperial 6s look quite nice naked.
 
The Imperial 6s are a two-way ported design featuring a 10” treated cloth-surround paper-cone woofer and a “phenolic ring” cone tweeter (you can read about the tweeter on the Parts Express website; part # 270-252). The large port is beneath the woofer, toward the left side of the front baffle. According to the above-mentioned Patrick Hart article, the Imperial 6s were the first loudspeaker designed for Marantz by Dawson Hadley, probably with guidance from his mentor at Marantz, Bart Locanthi. The Imperial 6s were said to have a frequency response of 60hz to 17,000hz.+/- 1.5 db, which is pretty darned smooth for a relatively inexpensive loudspeaker. They were made in the United States.

Hook-up and listening.

The Imperial 6s in my possession had little flat screws like those on Dynaco A-10s for speaker wire attachment, and they worked fine, though they’re close enough together that you have to be careful not to let stray strands of wire touch the wrong terminal. I hooked them up and placed them on my 20” speaker stands about 2 1/2 feet from the rear wall and separated by about 7 feet.
 
We listened first to Gary Burton’s Like Minds CD, an excellent jazz recording featuring Burton on vibes, Pat Metheny on guitar, Chick Corea on piano, Roy Haynes on drums, and Dave Holland on bass. I was immediately struck by how large and effortless the music sounded. Cymbals were natural and not overly sibilant or splashy, and the bass was surprisingly tight and punchy. Compared to the recently reviewed KLH 5’s, sound “came out” of the Imperial 6s more, but it was not more aggressive, nor was it more strained. There was some lower-midrange thickness through the Imperial 6s, which my audiophile friend said made the sound a bit “busy,” but I thought it added a bit of a sense of authority to the presentation. I was reminded of the A/D/S 810, which I also thought had a bit of a lower midrange hump, though the Imperial 6s may be a tad brighter than the 810s.
 
On Alison Krauss’s Paper Airplane CD, the sound was again really smooth. I thought Krauss’s voice was presented beautifully, with little or no CD edge, and a very expansive soundstage surrounded her. Guitars sounded realistic, mandolin and banjo had bite without being thrust forward in the sound stage, and bass was surprisingly tight. Most importantly, I found the presentation emotionally involving.
 
But it was Cantate Domino, a Proprius “audiophile” recording of organ and chorus, that really won me over with the Marantz Imperial 6s. I don’t think I’ve ever heard massed chorus sound more relaxed. And the air of the church was presented more convincingly than I can remember hearing. When I switched to my KLH 6s, one of my familiar vintage reference speakers, the sound was similar, but both solo vocals and massed chorus sounded just a bit “edgier,” and the air of the church was not as noticeable. On this recording, I definitely preferred the Marantz speakers.
 
On an EMI Classics recording of Arthur Rubinstein playing Chopin Nocturnes, the Imperial 6s were not as focused as were my “Customs” (Dynaco A-25s with Dayton soft dome tweeters) or the previously reviewed KLH 5s. Same with Keith Jarrett’s Standards Live, with Gary Peacock on bass and Jack DeJohnette on drums: The piano in both recordings lost a little of its attack, and the image of the instrument was a bit diffuse. I came away with the impression that the Marantz Imperial 6s are not at their best with piano music, though I hadn’t noticed any issues with Corea’s piano on the Gary Burton CD. And to confuse things further, the piano sounds fine on Stan Getz’s Serenity CD, which I’m listening to as I write.
 
With a friend’s CD recording of Holst’s The Planets, the Marantz Imperial 6s were really back in their element. The scale and depth of the music were both well-presented, and the soundstage was three-dimensional and placed mostly behind the plane of the speakers, meaning that orchestral climaxes were enjoyable and not thrust into the listener’s face.
 
With Greg Brown’s The Poet Game CD, the Marantz Imperial 6s surprised me. I expected Brown’s gravelly voice to sound full but a bit diffuse. Instead, it was crystal clear and dead center, but with less heft than I expected. It was satisfying, but in a different way than I had anticipated.

Conclusions.

I admit that I am surprised by how much I enjoyed listening to the Marantz Imperial 6s. They come from an era when mid-fi loudspeaker designers still cared about sound quality, and were torn between what’s right and what sells. The Imperial 6s were designed right, and it shows. I consider them to be fully competitive with the better known classics of their day, including KLH 6s, Acoustic Research AR-2axs, and Large Advents. Which you like best will be a matter of personal taste, as well as the music you are listening to.

It’s worth noting that all of the speakers mentioned in the previous paragraph are acoustic suspension designs, while the Marantz Imperial 6 is a ported design. In theory, the bass of a comparably sized acoustic suspension speaker should extend deeper (and efficiency should be lower), but I found the bass of the Imperial 6s to be quite good on the Proprius organ and chorus recording. Perhaps they give up something in the bottom octave, but I didn’t notice it. As expected, the Imperial 6s were more efficient than the other speakers, and generated a higher SPL for the same volume control setting than the KLH 6s, Dynaco A-25s or my “Custom” A-25s with Dayton soft dome tweeters. Their high efficiency makes the Marantz Imperial 6s especially well-suited for modestly powered tube amplifiers, like my 17 watt per channel Fisher X-100B.
 
In my system, Marantz Imperial 6s had a really surprising combination of smoothness, soundstage depth, and, on some music, an almost Klipsch Heresy-like presence and immediacy. They may not be pin-point imaging champions (though they surprised me on the Greg Brown CD), and they may not at their best with solo piano (though their performance with piano seemed to vary with the recording). But they are really good with choral and orchestral music, and I thought they did a nice job with female (and male) vocals as well.
 
Retail price of the Marantz Imperial 6 was $129 each in the early 1970s, but today you could probably find a pair for well under $200. My guess is that cosmetically challenged pairs could be found for well under $100. Because they didn’t sell well in their day, they are probably rarer than Dynaco A-25s, Acoustic Research AR-2axs, or Large Advents. But if you see a pair out there in working condition, I recommend you give them a listen. I may just add this pair to my permanent collection.
 
Associated equipment used in the writing of this review:  NAD 521BEE CD player; Kenwood KT-7300 tuner; AR ES-1 turntable with Shure M97xE cartridge; NAD 1020 preamplifier; Fisher X-100B tube integrated amplifier; Dynaco A-25 loudspeakers; Dynaco A-25 loudspeakers with Dayton soft dome tweeters; KLH Model 6 loudspeakers; DCM Time Window loudspeakers; M&K V-2B subwoofer.

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  • 2 weeks later...

Very nice write up Pete B. I pretty much agree with your observations. The 6 is fantastic with jazz and classic pieces. Blues are also great providing you don't try to run them in concert levels. 

I am the original owner of 2 Imperial 6-Gs. In the 70's I work for a quality stereo retailer and have listened to many speakers. The 6-g at the time gave me the best sound value. Comparable to speakers costing 100s more. 6-g was so efficient even the budget receivers can power them very well! The 6-g with the Marantz 4270 and Dual 125 lasted to this day reliably with no distortion. A number of my friends are musicians and enjoy this setup very much. Some may tweak the bass/treble, not too much as everyone's taste is different. Tweaking the L switch did not do much as the tweeter depends on the music selection can be a bit bright. 

In a fairly large room and the speaker set a couple of feet from the wall. The speaker shines despite its size. In smaller enclosures, the low range can get a bit overpowering as you increase the volume. I find loosely stuffing cotton rags in the ports helps make them brighter.

Lately I inherited 4 6-g and a Marantz 4270. They were used in a very large open room. I set up the new system in the cellar. The receiver set up in 4 channel mode and found huge disparity in sound among the speakers. So of course, I tested all 6 speakers by checking polarity, spl and sound of each individual drivers. 2 tweeters and one low range driver was defective. All from the inherited speakers. I suspect maybe the 4270 may be too much power. Swapping the bad for the good, I was able to get 4 good speakers. What is interesting is one pair uses what looks like fiberglass sound deadening. Another pair uses foam padding. The last pair uses sound deadening panels you would use on walls for accoustic! Surprised to see this from the same model speakers.

Well, I notice each panels changes the nuance of the sound. I was used to the fiberglass material so naturally I choose that sound. The foam padding sounds too bright, as if the padding is not absorbing the sound much. The padding looks like the pads you would find in furniture. The acoustic padding is much better and makes the sound a bit boomier. I kept the acoustic padding and the fiberglass and gave the last pair with defective drivers to a vintage shop that restores speakers. I expect it be on eBay soon.

Now, I'm using the 4270 with the accoustic panels speakers in front and the fiberglass panels in the rear. Seems like an interesting setup in quadraphonic mode. The fiberglass being 'quieter' provides a real nice setup. Now to have the musicians provide insight.

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  • 6 months later...
On 12/17/2012 at 7:07 PM, Dchristie said:

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

Hi, according the imperial 6 I have, is the coil over the tweeter only active in switch position decrease. Plus the 6ohm resistor parallel to this coil.20230126_120316.thumb.jpg.2c32f4285c17c5bda42e8556690a3b17.jpg

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In the Imperial 6, 6B, and 6G speakers, the 0.6 mh coil is shunted across the positive (+) and ground (-) inputs and the 7.0 uf cap is in series with the positive input which provides a 2nd order cutoff for the tweeter at all times. These components are always active in the crossover circuit along with a 3 ohm, 5 watt resistor in series with the positive input. An 8 ohm resistor is also shunted across the + and - inputs of the tweeter. The 1 ohm and 6 ohm resistors are switch operated to provide an increase and decrease in the tweeter output, respectively. The normal position on the switch takes the 1 and 6 ohm resistors out of the circuit. All of the rest of the components remain active in the crossover at all times.

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Hi thanks,

According crossover board Marantz Imperial 6 I have (seriële nr's 27807 and 27819) the woofer is in serie with a 4 ohm resistor, this resistor is in parallel with coil 1.0mH.

If the switch is in normal position, 7uF is in serie with 3 ohm resistor and tweeter. The tweeter is in parallel with 8ohm resistor. 

The 0.6mH coil is only used in the decrease position in parallel wit a 6 ohm resistor 

Regards, from the Netherlands

PS: I have also a Marantz 5

Very strange the woofer is not connected to the 1.0mH coil, but direct at the plus and minus connectors.

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  • 2 weeks later...
On 1/31/2023 at 7:53 PM, Dchristie said:

Could possibly have different versions of the Marantz Imperial 6 speaker. But the version I am familiar with here in the USA is as described in the above forum discussion. The schematic from the Marantz 6 service manual is attached for your information.

 

Imperial6_crossover_schematic.pdf 559.64 kB · 7 downloads

Hi, I managed to open your pdf. I noticed 1 speaker is as in the pdf diagram, in the other one, the wires are wrong. So I re-wired them.

Do you have also a pdf diagram from Marantz 5 model. I checked the wires and noticed the woofer has no crossover frequentie and is directly connected to the input terminals. 

Regards, Libertus 

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On 2/12/2023 at 8:34 AM, Libertus said:

Hi, I managed to open your pdf. I noticed 1 speaker is as in the pdf diagram, in the other one, the wires are wrong. So I re-wired them.

Do you have also a pdf diagram from Marantz 5 model. I checked the wires and noticed the woofer has no crossover frequentie and is directly connected to the input terminals. 

Regards, Libertus 

Libertus, in the model 5, the woofer has a natural acoustic rolloff at 2000 hz( no additional crossover components are needed) . The woofer rolls off by itself at the crossover point and is wired directly to the amp. The tweeter crossover is very similar to the model 6.   A 1.0 mh mh coil is shunted across the positive (+) and ground (-) inputs and a 4.0 uf cap is in series with the positive input which provides a 2nd order cutoff for the tweeter at all times. There is also a 10 ohm, 5 watt resistor shunted across the tweeter terminals. These components are always active in the crossover circuit. A 3 ohm, 5 watt resistor in series with the positive input and A 10 ohm, 5 watt resistor shunted across the + and - inputs of the tweeter,  are switch operated to provide an increase and decrease in the tweeter output, respectively. 

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15 hours ago, Dchristie said:

Libertus, in the model 5, the woofer has a natural acoustic rolloff at 2000 hz( no additional crossover components are needed) . The woofer rolls off by itself at the crossover point and is wired directly to the amp. The tweeter crossover is very similar to the model 6.   A 1.0 mh mh coil is shunted across the positive (+) and ground (-) inputs and a 4.0 uf cap is in series with the positive input which provides a 2nd order cutoff for the tweeter at all times. There is also a 10 ohm, 5 watt resistor shunted across the tweeter terminals. These components are always active in the crossover circuit. A 3 ohm, 5 watt resistor in series with the positive input and A 10 ohm, 5 watt resistor shunted across the + and - inputs of the tweeter,  are switch operated to provide an increase and decrease in the tweeter output, respectively. 

Thank you,

It is as you described. I noticed only the coil is 0,6mH in both Marantz 5 (without Imperial) woofer with paper cones and rubber. Tweeter the same model as in  the Marantz 6, only smaller and smaller magnet.

I measered all component from Marantz 6 Imperial also, in one I replaced the resistors (1%,10W) and Capacitor 7uF. I did not hear any differance with the one not modified. So I replace the original components back again.

When you have heared a Marantz 6, the Marantz 5 is disapointing. But overall I like more the AR3a.

Thank you for all information,

Libertus 

 

 

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