Dchristie

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.

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

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.

I am looking for bass drivers (25 F-EW) for the Dynaco A25 XL or A40 XL series speakers. I have a pair of original 25 TV-EW drivers for the A25/35 speakers that I would trade if so desired or I am willing to purchase F-EW drivers as well. Please send a PM if anyone can help me out. Thanks, Dean

Found a pair of M1 speakers so disregard my WTB request. Thanks Dean

I recently bought a pair of AR M1 holographic speakers and unfortunately, one of the bass drivers is bad so I am looking to purchase a replacement driver. If anyone has one that they are willing to part with , please send me a personal message. I would buy one, or a pair or possibly even 2 complete M1 speakers if necessary. Thanks Dean

Just reread my response above and realized that I referred to the AR 3 with "the phenolic tweeter " a couple of times which is obvious since I think that all of the AR 3 versions may have had the phenolic tweeter in common. What I meant to say was phenolic midrange since this was the topic of concern. Probably most folks understood the intent but I wanted to clarify just in case.

Hi Cropper, as Roy has pointed out in other discussions , a late model AR 3 with the factory approved later cloth midrange and the appropriate crossover mod is still an AR 3 speaker but it may not sound identical the the AR 3 speaker with the phenolic tweeter. However, this is always subjective but it stands to reason that the changes could be audible to some listeners. Personally, my AR 3 speakers with the cloth mid sound very good to me but I have not directly compared them to the earlier model with the phenolic tweeter. But, they are still an AR 3 sold as an AR 3 by AR so I am not as worried about the cloth mid so much. Probably the bigger issue with reselling AR vintage speakers is whether for not they are original as replacing crossovers, refinishing cabinets , and so forth often are issues with buyers who want everything to be original. Once again, I restore my speakers with new crossover components, cabinet restorations and other changes to meet my approval and not necessarily to keep them original. I do not believe that the later cloth mid necessarily made the late production AR 3 inferior to the original as this would once again be subjective to the listener but certainly AR was not concerned as the evolution of the AR 3 to the AR3a was never considered a step back . My AR 3s do sound different compared to my AR 3a speakers but I enjoy both. I am sure you will also like the sound of your restored AR3s. Sometimes we get concerned about issues which seem to be really important to the final sound but in reality, contribute less to the final sound than a lot of things that we have no control over since the adhesives, compliance, and other physical characteristics of these decade old drivers have changed since they were new. However, it is amazing that they still work and also still provide a lot of satisfaction to those of us that like to fool around with them. I am sure others have their own opinions and may chime in as well, but I try to not take this hobby too seriously and just enjoy the whole vintage audio experience. Just my 2 cents worth!

Thanks Chris. Any chance you would be willing to just remove one of the mids from your AR 3a speaker and replace it for one of the phenolic mids in one of the new AR3 speakers ( with the correct xover mod of course) and then you could compare a single AR3 with the modified cloth dome to your other AR 3 speaker with the original phenolic dome mid. Although you would only be comparing essentially mono AR 3 speakers with different mids, it would most likely give you some idea what the AR3 speaker with the cloth dome sounds like in comparison to the AR 3 speaker with the phenolic dome mid . Just an idea. Dean

Hi Chris, now that you actually have a working original phenolic 3 dome midrange, it would be great if you could compare it with the 3a midrange dome for sonic comparisons. I have been very impressed with the cloth 1.5 dome and actually have it in my pair of 3s ( with the crossover mod) since I have not had the luck of finding an original, properly working phenolic mid. Would be great to get your impressions of the 2 different midranges and how they do or do not affect the final sound of a 3 speaker. If no negative difference is detected , then using a more durable, modified, 3a cloth mid in a 3 speaker might be a good thing in the long run IMO . Thanks Dean

Also wondering about the square cutouts for the Altec drivers. I am not very familiar with the AR-1 speaker, but I have never seen square cutouts behind the Altecs before. Almost looks like the cabinets are open as there appears to be damping material showing behind the drivers in the cutout corners. Does not look quite right to me, but again, I am not that familiar with all of the model changes for the AR-1speaker.

Thanks Pete. Yes, I have revision 2 (later Original Large Advent crossovers) as per your baselaudiolab info. Dean

Hi folks, over the years I have accumulated several pairs of Large Advent ( Original series not the New series) drivers including tweeters, bass drivers and of course the crossovers. As you all are aware, the Double Advent system was simply running a pair of Large Advents in parallel on each channel ( also referred to as stacked Advents) with each speaker sharing the crossover with the other speaker and the amp. I am currently building a Double Advent system from scratch and want to place the drivers for each channel in a single cabinet ( compensating for the correct volume for the doubled up bass drivers) but would like to have the appropriate crossover values for the dbl system (not separate crossovers for each single system in parallel as per the original design). I am going to rebuild the crossovers with better components eliminating the frequency switch so looking for some help on what the inductor, and cap values would be appropriate for such a system. I seem to recall that the single Large Advent had a 1.6 mh inductor in series with the bass driver ( 1st order slope) and a 16 uf cap in series with a 3 ohm resistor with a 0.45 mh shunt on the tweeter ( 2nd order slope). If I remember my basic speaker building principles, a change from an 8 ohm system to a 4 ohm system doubles the inductor value for a 1st order crossover ( in this case for the bass drivers) and halves the inductor and doubles the capacitior values for a 2nd order crossover ( tweeters). So, can anyone ( Pete or Carl, or?) give me some guidance - would simply applying the basic 8 to 4 ohm principles outlined above be appropriate for my Double Advent rebuild? And, if not can anyone supply the correct values for a single crossover in a Dbl Advent system? Thanks Dean

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