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Posts Tagged ‘Soft Dome’

Monitor 1 by Keith Kinnear

May 20, 2010 1 comment


High Performance Studio Monitors

The main objective of this design was simply to create the most accurate, high precision studio monitors possible. The speakers were able to meet that objective in almost every way thanks to some key components of the design.

One of the most influential aspects is the cabinet construction, including the unique six-sided shape and complicated panel and joint structures. They help these speakers avoid a whole host of problems traditional box designs usually have to deal with. Panel vibrations, internal cabinet standing wave resonances, and most of the effects of edge diffraction did not pose a problem with these speakers in the least.

Multi-layer cabinet construction (MDF, Baltic Birch Plywood, mass loaded vinyl, masonite)

An equally important element of the design was the choice of high quality transducers – and believe me, no expense was spared when it came to choosing the right drivers to fit the design criteria. Both the tweeters and woofers are low distortion, high bandwidth drivers that are known for their smooth, un-colored sound. Both of them are also great performers and made it easy to implement them into this, and likely almost any other, design.

The crossover is the last piece of the puzzle to be mentioned since it connects everything together and literally shapes the sound of the signal being presented to the drivers. Many hours of testing and very careful manipulation of the passive circuit elements produced a crossover that reacts with the drivers in such a way that the on-axis frequency response only varies by 2 dB across a spectrum from 50 Hz to 18 kHz. Now that’s something that anyone can be proud of.

In all, the design was a success and the speakers have proven to do exactly what they were designed for – be highly accurate, high performance studio monitors.

Creative Commons License
Monitor 1 by Keith Kinnear is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.

Design Objectives

  • Highly accurate studio monitors for precision mixing and mastering
  • Relatively low crossover point to preserve vocal presence range
  • At least 103 dB SPL max output
  • f3 = 45Hz

Key Features

  • Full range two-way design made possible by the use of wide bandwidth, low distortion drivers
  • Unique cabinet shape and construction designed to eliminate many of the common diffraction, vibration, and resonance problems found in traditional box designs
  • Exceptionally flat frequency response from 50Hz to 18 kHz
  • Excellent impulse and step (time domain) responses, indicating a lack of time smearing and greatly improved clarity and transient accuracy
  • Outstanding horizontal off-axis response
  • Sturdy handles on the sides to make movement possible

System Tests

Frequency Response

Driver Response

Reverse Polarity Response

Harmonic Distortion

Left/Right Difference

Impulse Response

Step Response

Minimum Phase Response

Tweeter Tests – Scanspeak D3004/6600-00 AirCirc

Tweeter Frequency Response

Tweeter Horizontal Response

Tweeter Distortion

Tweeter Impulse Response

Tweeter Step Response

Tweeter Phase Response

Woofer Tests – Seas L22RN4X/P  H1208

Woofer Frequency Response

Woofer Horizontal Response

Woofer Distortion

Woofer Impulse

Woofer Step

Woofer Minimum Phase

Two Towers by José Cordero-Medina

April 20, 2010 Leave a comment

Unfinished Loudspeaker

Left-Right speakers capable of full frequency range and meeting Dolby standards for cinema playback. Designed to provide a cheaper replacement to the current sound system in Walker 134. Center channel also designed, not yet built.

Overall Design Goal:

Provide Dolby standards for cinema playback to Walker 134. System capable of outputting 85dB SPL at audience distance with a 20dB headroom and an additional 10dB for the Low Frequency Effects unit.

Cabinet Construction:

5-sided box removes parallel surfaces reducing resonance in particular frequencies while also providing directional sound for maximum even coverage. 3/4 in layer of 13ply plywood outer layer and 1/2 in inner layer of MDF combine to provide rigidity to the cabinet as well as support for its size of 5’5″.

Drivers:

Each of the drivers were first and foremost chosen for its sensitivity and secondly for its compatibility with each other. Unfortunately, not all have perfectly flat response, reducing the overall frequency response balance, thus not making them suitable as professional mixing speakers. They do offer great sounding playback worthy of cinema speakers.

Cross-Over:

Very simple design with some additional parts for driver attenuation. The tweeter has a 1st order Buttersworth at 1.8kHz crossing over to the midrange with a 3rd order Buttersworth at 1kHz. The tweeter has a baffle step correction above 4kHz of -5dB, the midrange has a -3dB pad and the entire cross-over has a -6dB pad. The midrange rolls off naturally at the bottom end. The woofers have an interesting testing error cross-over that ended up working. As testing and tuning went by, I was changing the crossover from a 3rd order Buttersworth at 150Hz to 100Hz. I changes the capacitors, but not the inductors. Not sure what kind of cross-over it really is now, but it did what I needed it to, so I left it. It also has a notch filter at 200Hz to get rid of an overlap with the midrange driver.

<a rel=”license” href=”http://creativecommons.org/licenses/by-nd/3.0/us/”><img alt=”Creative Commons License” style=”border-width:0″ src=”http://i.creativecommons.org/l/by-nd/3.0/us/88×31.png&#8221; /></a><br /><span xmlns:dc=”http://purl.org/dc/elements/1.1/&#8221; href=”http://purl.org/dc/dcmitype/Sound&#8221; property=”dc:title” rel=”dc:type”>Michigan Tech Transducer Theory Dolby Speakers</span> by <span xmlns:cc=”http://creativecommons.org/ns#&#8221; property=”cc:attributionName”>Jose Miguel Cordero Medina</span> is licensed under a <a rel=”license” href=”http://creativecommons.org/licenses/by-nd/3.0/us/”>Creative Commons Attribution-No Derivative Works 3.0 United States License</a>

System Tests:

Frequency Response

Driver Responses

X-Over Responses

Harmonic Distortion

Horizontal Frequency Response

Step Response

Minimum Phase Response

BB 2-Way Loudspeakers

April 20, 2010 1 comment

A well balanced speaker with a low x-over by Ben Boeshans

The primary design goal of the speaker is all-purpose music speaker for everyday listening.  The speakers require good low-end extension, good clarity, and low fatigue.   The crisp highs were obtained through crossover points calculated to be 900 Hz for the woofer and 1.2 kHz for the tweeter.  The goal was met, as exhibited by the several peer reviews some of which commented, “extremely clear,” very accurate,” and “sounded really clean.”  I really like the sound of plucked guitar played on the speakers.  If one closes their eyes they can believe the guitar is being played in the same room.  Part of that effect is also attributed to the reverberation in the cabinets.  After experimenting with a few different types and amounts of damping materials a balance was found between the openness of the speaker and eliminating resonances.

Design Objectives

  • All-purpose Music Speaker
  • Tight Low-End Response
  • 97dB SPL Max output
  • f3 = 50Hz

Key Features

  • Soft-dome tweeter for mellow yet clear highs.
  • Low crossover point for fast transient response.
  • 2” Port for bass extension.
  • 8” Woofer for solid, defined low-end.
  • MDF/Plywood layered cabinet for reduced resonance.
  • Smooth frequency response 60Hz to 20 kHz.
  • Accurate off-axis response.

Technical Reports

Tests

Tweeter & Woofer Response

Step Response

Minimum Phase Response

Harmonic Distortion