Tizman

The explanation I got was that because the crossover doesn’t pass the LF portion to the speaker, the current draw that would otherwise happen isn’t there anymore. In other words, the driver is the load, and if the driver isn’t drawing current for the LF that is filtered out by the crossover, the amp doesn’t need to supply the power to the missing LF portion. Again, this information is based on my questions about using small output transformers on an amp built for just the HF section of a horn two way. I currently own three electronic crossovers. I would love to use them, but I have found that every one adds too much noise for my very quiet listening room, and that passives just sound better. I wish it wasn’t so, because using an active crossover would simplify things greatly, but it is.

It seems likely that much of the perceived benefit of bi-wiring is, as you say, due to a better connection being made by the home user when they bi-wire. Perhaps I am missing something, but I can’t see how it would make a difference to attach two sets of wires to your amplifier’s output rather than splitting the power at the speaker. What’s the difference? That said, splitting a crossover into parts and powering each part with a separate amp does make a difference. The source is split so that two stereo amplifiers get the same signal. In the case of a two way, one amplifier is connected to the LF section, and the other amplifier is connected to the HF section. The amplifier responsible for the HF feeds a driver with far lower power requirements. This amplifier is not called upon to power the LF portion of the signal, and therefore HF reproduction is not affected by the work required to power the LF as when one amp feeds both LF and HF. The HF amp has an easier job, and avoids the modulation of its output by the needs of the LF section. This is based upon my online research a few years back. Basically, I was trying to figure out if a tube amp output transformer would be impacted by receiving the full signal from the source, and amplifying that signal into a passive high pass filter that kept the LF frequencies from reaching the driver. This was in order to build an HF tube amp with smaller, less expensive output transformers that also, in my experience, produce better quality HF response than that from large OPTs. The answer I got at the time was that if an amp powers an HF crossover, the LF portion of the signal that doesn’t draw power also doesnt affect the amps performance any more. It’s effectively not there. This may be entirely incorrect, but it’s what I got out of my questions at the time.

Using two amplifiers into a divided passive crossover, with the bass portion separate from the mid and tweeter section, has obvious audible benefits. When I do this, I use an RCA splitter on my source so that I can plug into two separate power amps. One amp powers the bass portion, and the other amp powers the mid and treble portion in a three way, or the single HF driver in a two way. At least one, but ideally both amplifiers should have a volume control. Using two amplifiers instead of one confers multiple benefits. This makes it possible, for example, to use a 45 amp on the highs, and a push-pull EL34 amp on the lows. Obviously, it depends on the existing crossover as the crossover needs to be split, but that should be doable in many cases using the parts in the existing crossover. For most of the Klipsch crossovers I’ve seen, it’s pretty easy.

Yes, T2As. The crossovers are newer than the bass bins. I replaced the capacitors for new ones of the same values.

I ended up with the stock AA crossover values for the capacitors. The KHorns sound muddled overall as compared to my La Scalas. I feel that the midrange could be louder as compared to the bass. Perhaps I'll try changing the autoformer tap so that the squawker is 3 DB up. Something is off. The KHorn has deeper bass, more bass and better quality bass, but the La Scalas sound much more cohesive in the higher frequencies.

Leaving the speakers playing music overnight greatly improved the sound. They sound much better. The ‘74 La Scalas still sound more cohesive in comparison, and more “real”. The Khorns have much more and better bass. Perhaps I’m just not used to the more full range character of the Khorns? I haven’t tried going back to the original 2uF/.245mH/2uF tweeter crossover section. I am using the higher Q 2.2uF/.16mH/6.7uF recommended by ALK. Any opinions on this modification to the AA?

I have three pairs of La Scalas. My daily drivers are a pair of ‘74s with AA networks. I also have two pairs from 1989 with AL-3 networks. I prefer the ‘74s. The Khorn is my first. I hope it’s not an issue with the match between bass bin and the HF section. I have switched the tweeter portion of the crossover from the original 2uF/.245mH/2uF to 2.2 uF/.16mH/6.7uF on the original board, and have an extra outboard tweeter section that uses the original values to compare. I am currently burning in the speakers as they haven’t been used for a long time. This may be part of the problem.

Well thank goodness it’s all tubes for me. I suppose the protection diodes can be safely omitted in my case.

The entire crossover is not first order, but the crossover to the woofer is just a 2.5mH inductor. Isn’t that by definition first order?

That would be great. Thanks.

I have limited measuring equipment, so I’m not certain if my “close to spec” measurements are close enough. I am currently using a DMM, an LC meter, and a cheap LCR-T4 component tester. My Klipschorns definitely have potential. Their bass response is much deeper and better sorted than my La Scalas. That said, they don’t sound right overall. The speakers don’t image well and sound confused in the treble as compared to my La Scalas. Something is amiss. Old film caps that I have measured with my limited equipment have been mostly good. If the caps are good, what is causing the problem? The drivers seem to be in good shape, and are wired properly. The speakers are in the corners, and the corners are two block walls. The room is partially treated with sound absorbing panels and sounds good with the La Scalas. If not the caps, what?

John A has posted that including a .35 to .4mH inductor between the T2A and the squawker helps to take out a hump in the K-77 squawker’s response at 9K Hertz. Is this something I should include?

I am using extra long probes that add .2 Ohms or so, so I’m probably actually at .8 Ohms. That is .5 Ohm above the stock inductor. The other associated issue with the extra .5 Ohms is that I use mostly single ended triode connected tube amps, which have a high output impedance. Perhaps not a great idea. I’m not too concerned about the losses created by the additional .5 Ohms, as the Klipschorns in my room are a bit bass heavy, but the decreased damping might be an issue. I’ll try both and see.

I also have several .51mH air core inductors that I could parallel to get a .255mH value. Is that close enough for replacing the .245mH value in the schematic?

Sounds like a plan.

I checked the resistance across the 2.4mH inductor with a DMM set to resistance, and it is 1 Ohm. It is reasonably beefy.

I’m going to keep the original caps so I can return the crossover to original for any future sale. I will let you know if I change my mind though.

Thanks for all the replies. I’m going to replace all the caps, check for the brass screw and keep the rest for now. I have a bunch of Solen caps in the correct values, including 13uF, taken from a stack of three way crossovers I bought from a theatre redo. I also have a bunch of inductors including 16 gauge 2.4mH ones. Would these be close enough to replace the 2.5mH ones in the AA?

Hi All. I picked up a pair of Klipschorns! They are bass cabs from the 50s with K-33-E in them, k-400 horns with K-55-V drivers and square magnet K-77 tweeters. They sound a little off as compared to my La Scalas and sound flat with fuzzy imaging. I was about to switch out the capacitors, but measured the ones that could be measured in circuit, and they measured reasonably well. I haven’t seen these caps before in a Klipsch crossover so I was hoping on getting your opinions on switching them and the need for it. Please have a look at the attached photos.

Just wondering if you took them out and had a chance to look at them. I read somewhere that they don't use an autoformer anymore. Any details you may have would be much appreciated as I can't find anything about them online.

Thanks!

For the purposes of speaker design, are the effects on the driver parameters significant enough to keep me from using the normal K-48 parameters?

Interesting. What impact to parameters is normally expected when adding a magnet like this? My intended use is in a large horn subwoofer.

Hi All. I picked up this woofer last week and was hoping someone could help me identify it. It came with a couple of drivers that the seller identified as being Klipsch in origin. The lot included a K-48-KT. This driver has a cast frame and looks most like a K-45. The ribbed spokes on the basket are the same, and the rear vent and cone look the same. The big difference is the extra magnet attached to the back. Any insight would be much appreciated.

Here are a couple of REW screenshots comparing the bass response of my La Scalas to my two ways with Eminence Kappa 15C in a Peavey FH-1. The two speakers were measured in the same position with the microphone at the same height and pointing at the mid horn for the La Scalas, and the HF horn for my two ways. The microphone was 4' from the speakers. I understand that the 15C gives up a few DB at the bottom in exchange for better performance at the top of its range, but this measurement shows a drop of more than a few DBs. Subjectively, my two way is obviously bass shy compared to the La Scala. My question is whether this is normal, or not? Is this due to my improperly installing the 15Cs in the cabinets, or is this the missing "few DB at the bottom" that is normal? Any insight would be much appreciated. La Scala is red and 15C in FH-1 is green.