JohnA

I use a Meterman 27XT. https://www.tequipment.net/WavetekMeterman27XT.html

A few old Macs has a derived center channel out at preamp level. Does either of yours? If not, Mr. Paul sketched up a line level box to derive the center channel and that could feed your 5100 to control the center. I would link to the Dope From Hope had I found it. I will also recommend you rework the Heresy's crossover to be as much like your La Scala crossovers as possible and drop the taps of the squawker and tweeter on the autoformer one step to flatten the Heresy's response curve. I have done both on my HT center channel Heresy.

Do these chip amps more or less double/halve power then the impedance changes by 2 like a transistor amp? I notice the Toping is rated at 125 watts into 4 ohms.

They appear to be what we have termed Heresy 1.5s. That is, Heresy 1 woofer and tweeter and Heresy II squawker. The caps are original Klipsch. wait until you get your quality electronics back before final judgement, and check each driver to be sure all are working with matching output before replacing the caps. However, they are likely to be the problem. Use high quality film and foil caps for replacement. They will be expensive, but you don't have to spend $200 each. Audiocap PPT The gas at Parts Express ought to do. Go with better if you can. Avoid metalized caps as they sound a little brittle and edgy and Heresies don't need that. Look on the back edge plies for letters and numbers. They will be the serial number and/or the builders stamps. A quick repair for the hole in the woofer is a small piece of cigarette paper on each side of the cone glued with Somers. Smooth the edges of the hole first. you can get a replacement or that one reconed later. I'd just leave the dust cover alone, but there are some tricks with duct tape and vacuums to pull it out.

Heresy IVs are configured for bi-WIRING, not bi-amping. That means 2 pair of wires from one amp channel to each speaker. A dubious benefit if your wires are large enough. Bi-amping, actually for a Heresy, tri-amping, should bypass any passive x-over should be bypassed (short of a capacitor protecting the horn drivers) and then the electronic crossover can contour the driver's response, minimize the overlap between drivers and time align the drivers. This has a verifiable benefit.

Importantly, those '70s receivers have the correct cosmetics to make a 2-channel system look right. Since they sound pretty good, I get both things.

I bought an Alesis RA-150 for the church a few years back. I sounded "rather decent".

100 to 200. Switching from a SS amp with a 40 damping factor to one with 200 was a noticeable change very nearly obvious to a disinterested female. 😁

You might/should have serial numbers for your Heresies stamped into the edge plies on the top rear edge. If your Heresies have front mounted horns, they are II, III, or IVs. We can id the difference by components.

You could do it, but dropping the xover point to 4500 Hz and keeping the 6k - 9k EQ on the K-77-? will be tough. At 105 to 106 dB, the K-77s are a little hot, too. I believe you would need to double the attenuation of the Type AAs 21 dB/Oct to protect the tweeter. The literature indicates the lower crossover point results in nearly equal horizontal dispersion between the squawker horn and the K-77 at that crossover point.

More like 21 dB/Oct because of the built in EQ.

If you will adjust your load impedance, you'll get more accurate results. Woofer - 6.3 - 6.5 Squawker - 12.5 at 400 Hz Tweeter - 8 ohms (7.2 DCR) Your model does show the EQ built into the tweeter filter.

Each speaker needs its own amp channel.

Look at Acurus, Parasound and Rotel integrated amps. Note that you rarely/really don't need more than 50 watts/channel.

The easiest way to improve/restore the sound of 30 y.o. LaScalas would be to replace the capacitors in the AL-3 crossover. The AL-3 is a good crossover, designed for the K-55-M squawker. Consider replacing the autoformer and any inductors it the cores or windings are loose. A Type AA crossover of any kind is not a happy match to a system with a K-55-M squawker because the -M has, on average, 1 to 1.5 dB greater output than the K-55-V depending on frequency (but also within the output tolerances of the -V driver). Al Klappenberger's Universal crossover is VERY good and can be adjusted to account for the -M's output. Though the sound was clean and clear, I found them to be too bright because they run the tweeter at 105 dB, and higher at some frequencies, while the woofer and squawker run at 104 dB. Al has addressed this, but that adds even more cost. Your room may vary. As to bass horn resonances, they are there, but are only audible at pretty high volume. If you find a pair that needs some professional cosmetic help, have them add braces from the sidewalls to the doghouse, otherwise, enjoy them and don't worry. I had mine finished before I got an amp if enough to hear the resonance. Now, they are too pretty to modify.

BC, How old are your Heresy IIIs?

I'm pretty much with the rest. The cost of the amp/preamp is set by your checkbook. Pick an amp setup that does what you want and sounds good. You want phono? Streaming built in? Plays digital music? FM? I'm powering my H IVs with a refurbished Technics SA-300 receiver (35 watts). It works great and sounds good if you don't clip it. I have a Yamaha CR-820 (55 watts) on the shelf waiting to be refreshed. (I detest black components.) I'd suggest you look in the 50 to 100 watt range, with an emphasis on quality, low noise, high-ish damping factor and a relatively large power supply (high 4 ohm ratings). That should net a good sounding set that will comfortably drive your Heresies.

Put them back together and enjoy them until you can order a new diaphragm. The wrinkles won't be good for frequency response, but probably not fatal, either.

!981 should mean they came with square-magnet K-77-Ms and solder-terminal K-55-Vs, making them the best sounding of the Heresy Is.

https://www.coolerguys.com/

LOL1 No, they were made the way they are.

there is no visual evidence those capacitors are "dried out". In fact, those likely have no fluids at all and cannot dry out. Your speakers may well sound better with new, good film and foil caps, but you won't know until you listen for a while. Heresies of that era should sound forward and crisp, even bright. If they do, you don't need new caps.

There are a few slightly better drivers (is that what you mean by CD? that normally means "Constant Directivity.) for the K-400. You can try John Allen's A-55G; it has demonstrated lower distortion. You probably want to change to a Type AA crossover, or modify your AK2, a little for it. Your K-55-M is 1 to 2 dB hotter, depending on frequency and driver tolerance. The K-55-M is a good driver, with few problems. A driver with a 2" throat is not a good match to a horn with a 0.7" inlet/throat, regardless of the adapter. The advantage of a 2" driver is lower distortion at a given dB, outside the likely design and construction precision improvements. Are you really playing your Klipschorns so loud you can hear squawker distortion? It is often described as "frying bacon".

You need to upgrade! To this: https://classicreceivers.com/marantz-4400

If you had a multimeter, I think you'd have used it already. Since you likely don't, disconnect the bad tweeter from the crossover. Use a 1.5 volt battery, hold one wire to the negative terminal and stroke the positive with the other wire. You will hear scratching if the tweeter is good. If you don't, the bad tweeter needs a new diaphragm. Replacing a diaphragm is a precise, but not difficult job. It you hear scratching, the problem is in the crossover and we will need more data to pinpoint the failure.