High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place.

---

[ Follow Ups ] Thread: [ Display  All  Email ] [ High Efficiency Speaker Asylum ]

---

[ Alert Moderator ]

---

Re: Pi speaker design and measurement

Posted by Wayne Parham (M) on September 30, 2002 at 02:42:52

In Reply to: Re: Pi speaker design and measurement posted by hancock on September 30, 2002 at 00:17:39:

John -

I think it's best to leave it to the reader to interpret Dr. Toole's words. I'm sure that he wouldn't appreciate the inferrence that you know him so well that you can speak for him.

You've implied that my design principles and Dr. Toole's aren't in agreement. But these are some of the things I understood from this article, and where we're in perfect agreement:

• Dr. Toole describes the difficulties in measuring subjective performance

• Nevertheless, he shows evidence that certain qualities are liked by a majority of listeners and others are disliked by a majority

• He finds that listening tests are made more accurate when the participants don't know what they are listening to

• He also finds that listeners with poor hearing make poor test subjects and skew test results

• Dr. Toole speculates that there is a correlation between subjective listening tests and measurable objective factors

• Dr. Toole finds that frequency response is the largest determiner of speaker quality

• He shows that the most offensive quality is resonance, which is an anomaly in the frequency domain.

• He shows that measurement systems using gated time response have limited frequency resolution, and that anechoic chambers are preferred so that high resolution data can be obtained

• Dr. Toole suggests that several samples of high frequency resolution should be taken in an anechoic space, and that post processing be done for spatial averaging to help identify resonances

• He suggests that this step be taken because seeing response in the time domain and seeing response in the frequency domain are looking at the same thing in two different ways, but that the audible issue is resonance, which is a frequency domain issue

• Dr. Toole indicates that several measurement samples should be made at several different locations, and they need to be averaged for results to be accurate

• He further indicates that this spatial averaging requires data aquisition and post-processing, and that it cannot be done with several microphones arranged in an array and fed into a mixer

• Dr. Toole makes the point that spatial averaging is used to find frequency domain issues, i.e. problems in frequency response, and that spatial averaging be used to leverage the data so that it provides useful information about resonances

• He suggests that wide bandwidth resonances are more troublesome than narrow ones because there is more audio bandwidth that is able to excite the system into resonance

• Dr. Toole minimizes the importance of time-domain performance or measurements, except where they express themselves in the frequency domain as resonances

• He describes time-domain measurements such as waterfall charts as potentially misleading and "highly ornamental"

• Where the room/speaker system is considered, Dr. Toole indicates most people prefer speakers with wide dispersion over those with narrow dispersion for use in stereo systems, because of the richly charged reverberent field

• He further indicates that the opposite is true when multiple sound sources are used, such as in multi-channel systems

• Dr. Toole suggests that above 300 to 500Hz, real-time measurement analysis in-room is "almost certainly doomed to disappoint," and he reccomends that no EQ be added to correct for room anomalies

• He also suggests that speaker placement is largely responsible for its performance under 300 to 500Hz, and that proximity to boundaries is addresed most adequately with "broadband" tone control

• Beyond that, Dr. Toole indicates that most room "mode" resonances should be identified and considered separately from peaks and dips caused by acoustical interference from the interaction of many reflected sounds within the room

• He suggests that these room resonances be separated from interference effects, just like in the case of loudspeaker testing, and that the room resonance is usually found to be a very simple resonance and not troublesome

• Dr. Toole indicates that several measurement samples should be made at several different locations, and they need to be averaged for results to be accurate

• Dr Toole indicates that filters introduced to solve a problem in the frequency domain will not adversely affect the time domain, if the filter is used simply to counteract the effects of another filter

• Dr. Toole indicates that several measurement samples should be made at several different locations, and they need to be averaged for results to be accurate

• However, he cautions against misidentifying issues and adding filters that may not correct a problem frequency domain

These are some of the things that I interpreted from this document, and they are all consistent with arguments I've proposed to you in the past. Perhaps you see other things in this article, I don't know. But to say that these comments were "taken out of context" or that they aren't the things that Dr. Toole meant when he presented this paper seems a bit of a stretch.

Wayne Parham

This post is made possible by the generous support of people like you and our sponsors:

Sonic Craft

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---