Decent Floor standing Speakers for Home use

By Vivek Mehta
04 Apr 1996

Introduction

I moved into sunny Dubai in the United Arab Emirates in 1985, when I took up the offer to work as a Technical Support engineer for Hewlett Packard, looking after their technical workstations and CAD solutions. This was my first job after completing my Engineering degree in India.

As technical computing was an enjoyable hobby of mine at University, I was so excited that somebody was willing to pay me for "work" I would have willingly done free. As I thought I was earning easy money, I decided to treat myself to something really special with my first pay, which obviously translated into a high powered music system.

I love Rock and Roll, Heavy Metal and other music that was meant to be played out really loud. This is music that has to be "felt" as much as "heard".

I therefore bought a Nakamichi 505 two head Cassette player, a pair of Bose 501 Direct/Reflecting speakers and some cost-effective Technics 75Wrms amplifier. I am of the opinion that frequency response and distortion of a complete music system depend only on the Speaker and the input source. The electronics in the middle like the Amplifier and the Active Equalizer are so good these days that the distortion they normally produce is totally inaudible.

To my ears, the Bose 501 is a good enough speaker and gave me years of listening pleasure while listening to Audio Cassettes. Bose’s Direct/Reflecting technology of pointing one of the two Tweeters at an angle so that it reflects from a wall does create a realistic large auditorium type of sound.

However recently I was gifted a complete set of Classical CDs by a friend. This tempted me to purchase a Kenwood CD player which instantaneously made me realize how much I was missing out on earlier. The first thing one notices while making the shift to CDs was the much clearer highs. And then you notice the thundering bass (atleast on the friend’s music system). I then decided it was time to change my Loudspeakers to better reproduce what the Electronics was capable of now.

Though America seems to have more loudspeaker manufacturers and hobbyists than Europe, I found it really difficult to even get a quotation from the larger shops. They might have thought that a small order for two Woofers was not worth the effort to work out the cost of freight to Dubai and the problems of exporting it here.

In the end, I located a reputable manufacturer of High powered speakers in Britain. Warfedale/ McKenzie Acoustics makes a wide range of Woofers, Tweeters and Special speakers (for the sixty’s guitar sound).

I chose the mkC15-400lr, a15 inch, 400 Watt RMS, 800 Watt peak driver meant for Woofer and Woofer/Midrange applications. The specifications of the mkC15-400lr are:

fs 29.0 Hz
Qts 0.23
Vas 175 ltrs
Sensitivity 98 dB 1W -1M
AV Cost 170 Pounds

For the tweeters, I decided to use two Motorola Piezo Electric Wide Dispersion horns per channel in the same box as the mkC15-400lr. According to the specifications, they are capable of reproducing upto 40Khz at low distortion levels below 0.5%. Though many enthusiasts feel that Piezo Electrics might not be up to the mark, I was confident of the Motorola name and the three page technical literature they give with the Tweeters.

I intended to drive the mkC15-400lr with a new 150Wrms per channel amplifier. From past experience, I had found that my Bose 501 would distort Bass at loud volumes if I turned up the Bass control on the Amp. This was so even though the Bose 510 is rated at 150 Wrms while my old Amplifier was just 75W rms. I now know that Loudspeakers do not have the same power handling capability at each frequency. I also thought that I would get lower overall distortion if I used a high powered speaker and drove it to a f raction of its capability.

I had originally intended to build the "recommended speaker cabinet" that would come with the speaker and get it over with and enjoy the music. But as luck would have it, I received two differing recommended designs.

The Distributor in UK had a drawing of a 200 Ltr box which claimed an f3 of 30 Hz while the Manufacturer claimed that the best box was 95 Ltrs and gave an f3 near 35 Hz. This got me confused. I then spoke to a "Speaker Guru" who worked something out on his HP calculator and told me that Keele’s alignment dictated a box of only 35 Litres. It was then that I decided to take matters in my own hand and started reading up on Loudspeaker design theory.

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