- Welcome to North Reading Engineering HiFi Forum.
An Open Forum for Audio Enthusiasts and Professionals
News:
Only forum members can post to threads. To become a member, click the sign-up button in the upper left-hand corner and register. Create a username and provide and email address. You're required to answer three (3) HiFi related questions to register, the responses are not case sensitive. If you're having trouble becoming a member, have a suggestion or wish to report a problem email to forum@northreadingeng.com. Usuallly takes a day or two to respond.
Recent posts
#1
Vintage McIntosh Amplifier Repairs, Restorations and Modifications / C20 Preamplifier
Last post by nre - Apr 15, 2025, 10:35 AMA recent job, C20 preamp. New power supplies, Bumblebee caps replaced, electrolytics replaced. SOmetime i the past it was serviced, poorly. Those areas were cleaned up and restored.
No message is associated with this attachment.
No message is associated with this attachment.
#2
Unofficial Klipsch Forum (the "UKF") / Re: Registration
Last post by nre - Feb 27, 2025, 04:49 AMQuote from: Oilyboy on Feb 24, 2025, 02:23 PMDone!
Did you announce this on the other forum? i came across this by google.
Yes, made a mention of it.
#3
Unofficial Klipsch Forum (the "UKF") / Re: Registration
Last post by Oilyboy - Feb 24, 2025, 02:23 PMDone!
Did you announce this on the other forum? i came across this by google.
Did you announce this on the other forum? i came across this by google.
#4
Unofficial Klipsch Forum (the "UKF") / Re: Circling the drain
Last post by nre - Feb 14, 2025, 09:46 AMTwo weeks of time-out errors on the Klipsch forum means there's no interest at their end in fixing the issue. It's an odd way to terminate a community that existed for over 25 years. If the company has made the decision to end support, one suggestion would be to have the museum assume responsibility for its maintenance. That would however require financial support plus continued moderation. IT support is also required.
The forum format isn't one the younger folks use. For those of us engaged in the early internet (USENET) forums are a natural way to communicate.
The forum format isn't one the younger folks use. For those of us engaged in the early internet (USENET) forums are a natural way to communicate.
#5
Vintage Solid State / Bose 1801
Last post by nre - Feb 11, 2025, 06:30 AMAn early production unit with C-core power supply transformer (seen in the 1800 Series I amp). This unit is a little over 50 years old and needs a going over. Quasi-complimentary design typical of the early 1970s. Very heavy and difficult to manipulate on the bench.
#6
Unofficial Klipsch Forum (the "UKF") / Re: Active net for Klipschorn
Last post by nre - Feb 08, 2025, 07:17 AMThis is the filter board:
And installed in a Crown XLi-1500:
And installed in a Crown XLi-1500:
#7
Unofficial Klipsch Forum (the "UKF") / Active net for Klipschorn
Last post by nre - Feb 08, 2025, 07:13 AMFrom where I'm parked, the crossover network of the Klipschorn, or any 3-way horn-based system, is best tackled with an active network and, to keep things as simple as possible, the implementation is limited to the bass section of the horn system.
Implementing complex elements in a passive net, for example, notch filters or band-pass elements with so-called "steep slope" low and high-pass side bands add all sorts of artifacts and distortions that are apparent when a side-by-side comparison, to an actively filtered unit, is made.
That said, the sound quality of the Klispchorn can be significantly improved by implementing and dedicated bass horn amplifier that sends a 4th order, bandpass filtered audio signal to the horn woofer. When compared to a stock Klipschorn using a passive AK-6 network, the difference is stark and determined to be quite improved, even for old ears.
My approach (first in 1984 and then again in 2017) was a bit complicated, I first designed a "universal" active filter that provides for a range of band-pass filter topologies and then designed the a PC board of just the right size to be "shoe-horned" into a relatively low-cost Crown stereo amp (an XLi series). The design will work for any bass horn and, I'd propose, or something like it, for every bass horn.
The amplifier with the filter installed and working across an 8 Ohm power resistor is shown below. This is what a 4th order, band-pass looks like:
This is the amplifier at a few different output levels:
This is the acoustic response of the Klipschorn bass unit with and without the filter operating:
The filtered response makes the transition to the mid-horn much better and it's without the weird artifacts associated with a passive.
Implementing complex elements in a passive net, for example, notch filters or band-pass elements with so-called "steep slope" low and high-pass side bands add all sorts of artifacts and distortions that are apparent when a side-by-side comparison, to an actively filtered unit, is made.
That said, the sound quality of the Klispchorn can be significantly improved by implementing and dedicated bass horn amplifier that sends a 4th order, bandpass filtered audio signal to the horn woofer. When compared to a stock Klipschorn using a passive AK-6 network, the difference is stark and determined to be quite improved, even for old ears.
My approach (first in 1984 and then again in 2017) was a bit complicated, I first designed a "universal" active filter that provides for a range of band-pass filter topologies and then designed the a PC board of just the right size to be "shoe-horned" into a relatively low-cost Crown stereo amp (an XLi series). The design will work for any bass horn and, I'd propose, or something like it, for every bass horn.
The amplifier with the filter installed and working across an 8 Ohm power resistor is shown below. This is what a 4th order, band-pass looks like:
This is the amplifier at a few different output levels:
This is the acoustic response of the Klipschorn bass unit with and without the filter operating:
The filtered response makes the transition to the mid-horn much better and it's without the weird artifacts associated with a passive.
#8
Vintage McIntosh Amplifier Repairs, Restorations and Modifications / MAC1700
Last post by nre - Jan 18, 2025, 08:03 AMThis unit was in a sad state of affairs, covered in dust, pet dander and hair, human presumably. It appears to have been sitting for years. When the hardware is in this condition, just start tearing it down, don't even bother with trying to spool it up.
I enjoy restoring hardware, the worse the better. In this case, underneath all the debris was a MAC1700 chassis in near perfect condition. And most of the bits and pieces are still available. A complete tear-down was in order. The way I proceeded here, first > power supply, second > output section and third > preamp then spool it up on the Variac after all resistance checks evidence nothing's shorted to the chassis (say, for example, the output transistors shorting to the heat sinks).
I enjoy restoring hardware, the worse the better. In this case, underneath all the debris was a MAC1700 chassis in near perfect condition. And most of the bits and pieces are still available. A complete tear-down was in order. The way I proceeded here, first > power supply, second > output section and third > preamp then spool it up on the Variac after all resistance checks evidence nothing's shorted to the chassis (say, for example, the output transistors shorting to the heat sinks).
#9
Unofficial Klipsch Forum (the "UKF") / Re: Registration
Last post by nre - Jan 18, 2025, 05:57 AMRegarding Registration
the forum receives between 200-300 requests/wk to join. Virtually all of it spam.
Activation requires admin approval, the IP address used at registration is examined and, if it's a known garbage machine, the registration request is rejected. It's done automatically.
That said, if you're a real human being with an interest in discussing audio, send me note at:
forum@northreadingeng.com
and I'll register you.
jw
the forum receives between 200-300 requests/wk to join. Virtually all of it spam.
Activation requires admin approval, the IP address used at registration is examined and, if it's a known garbage machine, the registration request is rejected. It's done automatically.
That said, if you're a real human being with an interest in discussing audio, send me note at:
forum@northreadingeng.com
and I'll register you.
jw
#10
Unofficial Klipsch Forum (the "UKF") / Re: Circling the drain
Last post by Sprinter 1104 - Jan 17, 2025, 07:41 PMThanks John for keeping it alive, at least for now. Hopefully it will gain some traction.