John Reekie
Technologicality, at work and play

Projects and measurements

Information about projects and speaker measurements, usually for forth-coming Hifi Zine articles.

How to make a 90 degree calibration file

Sometimes, a 90 degree microphone calibration file is useful. When measuring speakers in my home theater, for example, I find it a lot easier to just point the microphone at the ceiling with the 90 degree cal file loaded, then moving the microphone to point in the general direction of each speaker. If you don’t have a 90 degree cal file, here is how to make one.

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iPad Measurement Mics

I was curious about how the internal iPad microphone fared for measurements, and what else could be used. There are a few twists and turns here, so if you’re in a hurry, feel free to jump straight to the conclusion. Note: these measurements are not intended to be authoritative or definitive. I took them to […]

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The Convertible active loudspeaker – revisited

Some time ago. I wrote a proposal for an active loudspeaker called the Convertible, using an 8″ woofer and a tweeter with a waveguide. Since then, I came up with the Mini Convertible (additional articles still in preparation) project, which is a more compact speaker. Having now ordered and received some waveguides from Dave Pellegrene, […]

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SB29RDC on Pellegrene waveguide

In the original Convertible proposal, I wanted to use a waveguide on the tweeter. Towards to that end, I’ve now bought a pair of SB Acoustics SB29RDC from Dan Archer and suitable waveguides from Dave Pellegrene. (I also have another project in mind for the SB29/waveguide combo, which is a larger speaker using a high […]

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Mini Convertibles get their first showing

The Mini Convertible speakers got their first showing last weekend at “Bathurst,” an audio get-together hosted by Terry Jones. This is still the sealed monitor version, and Terry produced a pair of stands for them from somewhere. The cables coming out to the front of the picture are to subwoofers on either side of the […]

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The Tandem subwoofer

Updated 27 Oct 2013. I never thought I’d get excited about a plate amp. But, while waiting for the drivers for the Mini Convertible active speaker project, I was wondering how best to add a subwoofer to the sealed/monitor version of the speaker. After working through a couple of options, the completely obvious hit me: the […]

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The HifiZine Mini Convertible active speaker project – proposal

This is an alternate proposal to the HifiZine active 2-way loudspeaker project proposal using the miniDSP ICE-PWR125 two-way plate amp. This time, though, we’re looking at a smaller speaker – miniDSP told me that they designed the PWR-ICE125 plate amp to be as compact as possible, so I decided to get into the spirit of things […]

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The HifiZine active loudspeaker project – a proposal

Please note: this proposal for an 8″ two-way active loudspeaker project has been superseded by the following articles: The Mini Convertible, a 6″ two-way active loudspeaker project The Convertible active loudspeaker – revisited Introduction I’ve wondered for a while if it might make sense to publish some “HifiZine projects” – fully-documented DIY projects that supplement the many […]

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Room EQ Wizard SPL Calibration – without an SLM

DRAFT – not fully tested yet. SUBJECT TO CHANGE. The conventional method of “calibrating” the SPL (sound pressure level) in Room EQ Wizard is to use an external sound level meter (SLM). This procedure, documented in the REW online manual, basically means playing a signal through the speakers, measuring the result with a separate SLM, […]

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Room EQ Wizard on the Mac – an input workaround

[Update September 2014. As of REW Beta 21, 48 kHz operation is properly support and so the LineIn input workaround is not required for the miniDSP UMIK-1. Please note that it may still be required in other cases: A soundcard with more than two inputs and/or when you need access to inputs other than the […]

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