Seas U16RCY/P

After modeling what feels like a hundred mid-woofers, I have decided on the drivers for a new active two-way speaker. It will, of course, use a miniDSP as crossover, but this time I am going to use it in “preamp” mode, and furthermore add the miniAMP module. The aim of the project is to see what I can come up with that is along the lines of a “lifestyle” system but which also satisfies some fairly demanding “audiophile” requirements. The idea is that it isn’t going to have to be placed out into a room – as many of you probably know, the reaction yourRead More →

Weston Thunderbird parts

The Weston Acoustics Thunderbird is a kit amplifier from Earle Weston. This is a single-ended amplifier that by default uses two KT88 tubes, but can be biased (by changing the cathode resistor) to several other tube types. I first encountered the amp a couple of months ago at Terry Jones’ get-together in Bathurst, and took a couple of photographs of it. Since I already own one of Earle’s amps (the Trinity Signature), I decided to order and build up the Thunderbird kit as a complement. The topologies of the two amps are quite different (the Trinity is push-pull and valve-rectified whereas the Thunderbird is single-endedRead More →

miniDSP balanced audio DSP

I’ve been reading a bit about the use of multiple subwoofers to improve bass response and/or to reduce spatial variation in the response. In particular, the paper “Low-Frequency Optimization Using Multiple Subwoofers” by Todd Welti and Allan Devantier shows how placement of multiple subwoofers can be used to optimize response or spatial variation. They document the results from running a search algorithm over a multi-dimensional space defined by: The particular combination of subwoofers selected (two or four out of eight, in the most interesting part of the paper) The gain of each subwoofer The delay of each subwoofer The frequency and cut of a singleRead More →


Here is an option for the mid-bass unit that makes this an even more sensitive dipole than the initial proposal. And that is to use a Lambda Acoustics TD15M woofer. Here is the modeled response of this driver in infinite baffle, with 55W input power: With the higher rolloff frequency, the subwoofers will definitely be required for this version. However, with a nominal sensitivity of 97 dB/W/m, we gain a lot of transient capability in the 100 to 600 Hz region (or wherever the crossover ends up being). The gradual rolloff is because of the driver’s relatively low Qts – it’s not ideal for dipoleRead More →

Box dimension calculator

Here’s a little spreadsheet that helps to figure out the dimensions of a speaker box. What you do is enter a bunch of dimensions, and it tells you the actual internal volume. I’m sure someone must have done this before but I couldn’t find one. Here’s the file: Box dimension calculator Here’s a screenshot: Here’s how to use it. In the Enclosure section, enter the best-guess dimensions, and the thickness of the wall material. In the Round Port section, enter the diameter and length of the port as calculated by your box design program. If it’s a sealed box, enter 0 for the length. If youRead More →

6PEV13 Frequency Response

This project is aiming to build a dipole with more sensitivity and higher output than the Francesca prototype. Again, this is going to be a learning exercise and not the final product! Starting with the tweeter – upgrade to the regular (non-PDR) Neo3. This has about 3 dB more sensitivity, and a narrower dispersion pattern, which is actually what we want for a dipole. Also, I’ve read some comments online that it sounds better (in “naked” dipole configuration) than the Neo3PDR. So, worth a try then. Since the crossover to the tweeter is now at 5 kHz, I’m also thinking about trying a small compressionRead More →

Here are some ideas for a 6-channel amp that can be used in / tailored to a number of applications. The overview block diagram: The input gain trim can be one of the following. The one on the left gives about +/- 12 dB of gain. I found it in a schematic for a “Sub-bass processor kit” and someone has posted a scan of it here. It’s a variant (much simplified) of the circuit used in parametric and graphic equalizers, where a bandpass filter is insert in the feedback loop. If only attenuation is needed, and a relatively small amount at that, then a potRead More →

When the Virtue Audio amps are used with “high current” power supplies, a delay is needed before allowing full current from the power supply to flow. The first batch did not aw sufficient delay, so Seth Krinsky sent out update kits to those able to install them themselves. Here are a few pics of the process. Removing the cover requires that the volume knob be pulled off, and then a 2mm hex key to remove four screws: You need to pry apart the two sides of the cover and then slide it off the amp: Before you wrench the cover off though, make sure thatRead More →

Completed magnet wire interconnects with Eichmann bullets

I have in the past made interconnects with “magnet wire”  – this is a solid copper conductor insulated with a thin layer of enamel, so also search for “enameled copper wire” when looking for it. It is used for making the windings of transformers and motors, and is therefore plentiful and cheap. My earlier efforts involved wrapping magnet wire in a spiral around various type of core, like teflon tubing. But I was never all that happy with them and ended up putting my efforts at the time into the cable recipe devised by Jon Risch, involving the cores of Belden 89259 and 89248 twistedRead More →