Dave's Speaker Pages

Welcome to my speaker pages.

Last Update: 21 Feb 2014

WinGraph version 1.0 released

WinPCD Forum at Meniscus Audio


Mensicus Audio has provided a dedicated sub-forum at their site for WinPCD. WinPCD is a Windows application program patterned after Jeff Bagby's very successful Excel spreadsheet, the Passive Crossover Designer (PCD). WinPCD is compatible with Jeff's session files and uses an identical schematic scheme. It also largely emulates the design methodology so that PCD users should be able to work with it without much difficulty. Go to the links farther down for more information.


My pages are mostly from the empirical aspect. There are many excellent pages that cover the theoretical basis, such as this one by John K. I started this site as part of a discussion on the Madisound Discussion board back around 2000. It just kept growing as I found new topics that were of interest to me. I never expected that it would expand as it has. It remains only a hobby for me and likely will always be.

One of the more useful pages may be a web-based version of an article of mine published in Speaker Builder magazine (ONE:2000) included. It describes a method for determining relative acoustic offset for drivers when mounted on a baffle.

The Speaker Builder article covers one aspect of CAD design that must be properly handled if direct measurements are not used. That is, if the drivers are modeled and the minimum-phase (Hilbert-generated phase) of that model is used instead of the actual phase response.

The diffraction section shows the predicted and measured impact of baffle edge diffraction on the driver raw response as well as an extensive set of measurements of baffles with felt applied for diffraction reduction.

You may find a couple of pages on CAD software to be of interest. One deals with phase error due to an inaccurate CAD model. An example using CALSOD is extensively documented. A second one deals with the Hilbert-Bode transform and the effects which can occur when the CAD model does not have enough range, as when the high end rolloff of a tweeter is too high for the measurent system.

One of my early forays was Tweeter Tweaks. This section shows all details of adding wool to the pole piece vent, but not just any wool. I found, quite by accident, a product which is very useful for tweeters. It is used to stuff the pole piece vent and has absolutely no negative effects, although moderate density cotton, such as that found in aspirin bottles, seems to be nealy as effective. The cotton used is clean and much more consistent in density. I wholeheartedly recommend either of these for tweeters for which access to the pole piece vent is possible. Some tweeters either prevent access and/or they already have a good filler from the manufacturer. Examples of the latter are the Vifa XT-25 and the Scan-Speak tweeters (probably all of them). I also have a section that shows results of the testing of changing rear-chambers.

The models section shows a couple of the electrical and acoustic models used to represent a driver and/or system. It is one frequently used in CAD software.

The raw measurements pages are now for those taken on what I call my "quasi-IEC" baffle. Raw measurement text files either exported from LAUD v3.0 or CALSOD (with Hilbert phase using CALSOD) may be downloaded by anyone interested. Be aware, though, that they will only be quasi-anechoic (no baffle effects), so you won't get what these show. You'll have to post-process them for baffle diffraction. Tweeters will have significant baffle effects, midranges will vary, smaller ones having more effects. Woofers will have baffle step loss, but little if nay other diffraction effects. These files must be considered as useful more for some testing and learning than for any final designs. The files can be imported into the tools at the FRD Consortium or other software such as the Passive Crossover Designer to get approximations. Some users have taken it the extent of designing from scratch using this method, but it takes some experience to get reliable results. It's always best to use actual measurements if possible.


Software:
Windows Passive Crossover Designer - Version 1.2
Windows Complex Data Graphing Tool - Version 1.0
WinPCD Forum at Meniscus Audio
WinPCD Blog - Intended for release information and user feedback (we'll see how the latter part goes)

General Articles:
Finding Relative Acoustic Offsets Empirically - Speaker Builder Article (ONE:2000)
Driver Model Accuracy and its Impact on Phase
Hilbert Transform Generated Minimum Phase
Impedance Compensation Discussion and Graphs

Diffraction:
Understanding Cabinet Edge Diffraction - by Andy Unruh
Diffraction Effects and Amelioration with Felt
Comparison of Felt Ring vs. Felt Blocks
Diffraction Doesn't Have to be a Problem - audioXpress Article (June 2005)

Measurements:
Windowed Measurements - Description and Graphs
Raw Measurements - Graphs and downloadable files (old page format, no longer updated)
Raw Measurements II - Graphs and downloadable files - Fully up-to-date

Midwoofer/Midrange Tests and Modifications:
Insignia Tweaks - Improve the woofer response
KEF F15 Mid-woofer Tweaks
Dayton Reference Series Midrange RS52NA-8 - A good, small, dome midrange

Tweeter Tweaking:
Tweeter Tweaking Methods - How to improve a tweeters response

Tweeter Tests and Modifications:
Dayton Tweeter 275-070 - aka Gen. I Silkie
Dayton Tweeter DC28F-8 - aka Gen. IV or New Silkie
Dayton Reference Series Tweeter RS28A-4
Morel Tweeters - MDT-20 and MDT-30
Scan-Speak 6600 Air-Circ™
Scan-Speak 7100
Seas DXT Tweeter

Models:
Acoustical and Electrical Models

Design Examples:
Designs

DIY Meetings:
DIY New England

My Background

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