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The Boston Acoustics BA7500 Speakers


Introduction

The name Boston Acoustics dredges up faint memories of that ever popular company of years gone by. I remember their strong market force and listened to many of their home speaker products in the 1970's. Decades later, BA has exploded onto the computer speaker scene with a dizzying array of products. This time, we'll thoroughly examine their higher-end effort, the BA7500. Touting a 6.5" subwoofer, what seems to be four flat panel radiators and built in Dolby digital surround sound decoding, will the newest member stand up to TargetPC's most rigorous objective and subjective testing? Keep reading for the latest BA scoop.

Factory Specifications
The BA7500's
  • Power Output: Not Specified
  • Frequency Response: 45Hz-20KHz ±3dB
  • AC Adapter: 36 VA
  • 4-ch w/Dolby Pro Logic
  • Total Output: 107dB SPL
  • Warranty: 1 Year
  • List Price: $299 USD



http://www.bostonacoustics.com

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Description & Specifications

Boston Acoustics chose a very unusual subwoofer design. The 6.5" driver is both front and rear loaded as the picture (right) shows only a large front port hole. The speaker is mounted at the inside rear almost in a folded horn configuration of 1930's. The entire low frequency output is carefully controlled via the inside cavity and the shape and size of the external wide mouth port. My hand slips all the way inside and I could feel the surround of the paper woofer.

The rear panel unscrewed easily and with a small push, popped out to reveal, much to my horror, a design quality that should be far beneath a system in the $300 price class.

My first complaint is the heatsink arrangement. The heatsink for all six amplifiers is the entire rear panel of the sub box. Informal heat tests raised my concern about general UL safety. UL is Underwriters Laboratories which ensures a product's safety in the case of total failure. Searching frantically in the manual, on the outside of the shipping container and on the sub itself produced no UL reference number which means that the 7500's haven't been tested to UL's standards.

This greatly disturbs me as the entire rear panel heated up to at least 90ºF when merely idling (no output). Running the sub at maximum boom levels for over an hour made the metallic panel too hot to touch. Irregardless of the UL outcome (if and when testing is complete), I have serious concerns about placement on carpet or any potentially flammable surroundings.

Moving on to the the flat panel satellites, it should be noted that these are not flat panels. Yes, they appear the be to the naked eye, but the midrange driver contained inside is just a slimline conventional unit. However, BA made another goof as they ported the panels. Well, the port isn't directly the problem, rather the non-symmetrical nature of them. To save $$$, BA chose to manufacture all four satellite enclosures exactly the same. What's so unusual about that you ask? The problem is that the port for the front set of speakers faces to the right. That means sound will be abnormally emphasized for the left front speaker (if placed near a monitor) and the right front speaker receives little or no reinforcement at all in most environments. The result is a skewed sound stage and frequency response.

Objective Measurements

Data acquired and reported of this type is done without any opinion or bias whatsoever. For a quickie brush up course on audio terminology and measurements, point your browser to the Audio Reproduction Systems article.

Subwoofer

Woofer Impedance
Frequency (Hz)
Voltage (mV)
Current (mA)
Impedance (Z)
75
227
28.9
7.85
100
230
24.7
9.31
125
230
20.2
11.4

 





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