Rocky Mountain 2-Way

April 22, 2011 Kenny Stahl Leave a comment

The Life That I Have Been Waiting For

Rocky Mountain 2-Way Loudspeaker System

Overview:

The Rocky Mountain 2-Way Loudspeaker System was designed to be used as mixing monitors.

Features:

Flat Frequency Response (1.5dB variation)

Sealed Box Construction Providing Accurate Low Frequency Reproduction

Low Frequency Extension: F3= 55Hz, F6= 45Hz, F10= 40Hz

Active Crossover With Computer Controlled DSP that allows for the maximum control of the speaker system

Absorbent Foam Baffle that combats MF Diffraction and Makes the HF more directional.

Capable of 90-98dB Continuous, 110-115 Peak

1 1/4” Cabinet Construction (13ply Baltic Birch/MDF Composite)

2 1/4 Cubic Foot Volume

Custom Made Grill

Made Proudly In Michigan

Drivers

Woofer: Seas Prestige 10″ H1411

Tweeter: Seas Prestige 27TDFC, 1″ Silk Dome Tweeter

Enclosure

Exterior: 3/4″ 13-ply Baltic Birch

Interior: 1/2″ MDF

Documents:

Block Diagram:

Block Diagram

Testing Results:

Speaker 2 All Drivers

Speaker 1 All Drivers

Speakers 1 and 2 Differences Pt.1

Speakers 1 and 2 Difference Pt 2

Speaker 1 Polarity Flipped Tweeter

Horizontal Off Axis (Black 0*, Green 30*, Red *45, Blue *60, Red *90)

Vertical Axis Frequency Response (Black 0*,Blue *30, Orange 45*, Green 60*, Blue *90)

Tweeter Horizontal Off-Axis Purple=0*, Orange=30*,Red=45*,Green=60*)

Woofer Horizontal Off-Axis (Blue=0*, Orange=30*, Green=45*, Red=60*)

Tweeter Vertical Axis (Purple=0*, Green=45*)

Woofer Vertical Axis (Blue=0*, Red=45*)

Full System Speaker 2 Step Response

Full System Speaker 2 Impulse Response

Tweeter Step Response

Woofer Step Response

Full System Minimum Phase Response

Woofer Impedance Compared with 8Ohm Resistor

Tweeter Impedance Compared With 6Ohm Resistor

Cross-Over Response

Rocky Mountain 2-Way Loudspeaker System by Kenneth G. Stahl III is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
Based on a work at kennystahlrock.com.

Categories: 60-90lbs, Active, Bookshelf/Stand Mounted, Uncategorized

Wharfdale W90 project

This project was intended to refurbish a set of Wharfdale W90 “six” way speakers. These speakers were old, had poor frequency extension, a lot of distortion, and a frequency response curve that looked as if a pice of spaghetti had been thrown at the spl chart. Despite this there was some unique concepts that went in to the design of these speakers originally and to be honist studying the designs of this old set of hi-fi speakers was more educational that building the speakers themselves. These speakers featured a rear baffle that was filled with sand in between two layers of wood this clever dampening design if implemented more fully though out the cabinet design process could be a useful tool in making enclosures that are both ridged and dampened. The 12 inch woofers had a unique design as well. Each cab used two woofers in a separate enclosure. This was done for the purpose of tuning one of the enclosures differently. To achieve this Wharfdale filled one of the cones with Styrofoam, this changed the moving mass of the piston (the cone of the driver) it also decreased the surface area. I suspect that this was done to even out the low end frequency response by filling in gaps that the normal woofer had ether in the low end or the high end of its range. these speakers also had a strange mid range and tweeter design. The tweeter and mid range drivers were not placed in a sealed enclosure as most cone mid range drivers and tweeters are rather they were placed in an open box(see pics below). this open box design created a lot of positive and negative summation due to the reflections off of the rear baffle and the sides and tops of the box. these reflections were severely detrimental to the frequency response and over all clarity. After the speakers had been finished I ran in to the same problem; how ever it was nearly as dramatic as in the original design. Due to the fact that cloth dome tweeters and mid range drivers were selected only the reflections off of the sides of the boxes that caused summation issues. I plan to experiment with this later to see how much moving the front baffle forward improves the frequency response. There is no doubt in my mind that the amplitude of summation is directly related to the depth of the open box. Over all the goal of improving the quality of these speakers was accomplished; the frequency response was improved and the F3 was increased to about 70 Hz from an original extension of about 100 Hz. However the comb filtering effect caused by the cab design makes these speakers sound boxy and dated. In the end these vintage Hi-Fi cabs retained a vintage tone but with greater detail and frequency extension while having flatter frequency response.