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Date: Mon, 09 Jun 1997 20:01:54 -0700
From: William Eckle <wmeckle@primenet.com>
To: Lsrtwo@aol.com
Cc: bass@mcfeeley.cc.utexas.edu
Subject: Re: Radio Shack/Optimus Pro-LX5 upgrade

At 06:24 PM 6/9/97 -0400, Lsrtwo@aol.com wrote:

When reading an on-line article about a DIY computer speaker project, I noticed a reference to one of your designs for a small speaker system using the Tonegen 458 mid-bass and the Linaeum tweeter. Is there a web site to visit and view this design?

Not that I know of.

I am interested in upgrading a friend's Radio Shack Pro-LX5 speakers that use the Linaeum tweeter with about a 5" mid-bass. My brother in law has the NHT Super Zeros that use the Tonegen 458 mid-bass and their midrange sounds great. I would like to locate the specs for the tonegen drivers, including the dimensions, to see if they will physically fit in the cramped rear mounting area in the original radio shack cabinets, and work well in the box volume. Do you know of a source for the Tonegen 458 bass-mid?

I built two pairs of 458/Linaeum dipoles in 3 liter sealed boxes, using a .30 mH, 14 ga. coil on the woofer and a 6.0 mfd cap on the tweeter. Was extremely happy with the results.

458 info follows. Hope this helps.

NHT 458 4.5" Paper Cone Shielded Woofer as used in the Super Zero. NHT part #P-1-11-015-1 (Retail for $37 ea. in May 1996).

Supplied by Ken Kantor         Measured by "LEAP" in real world
From NHT factory               #1        #2        #3       #4

Znom=   8.000   Ohm             -        -         -        -
SPL=    85.6    dB           85.8672   85.7169   85.1383  85.6941
Revc=   6.820   Ohm          6.9       6.9       6.9      6.92
F0=     72.6    Hz           71.5742   73.2651   70.0414  78.9581
Sd=     0.0067  m^2          .0066     .0066     .0066    .0066  
Qms=    1.960                2.0413    2.1419    2.1065   2.2133
BL=     3.832   Tm           4.0162    3.9713    4.1925   4.1562  
Qes=    1.023                .9287     .9781     .9468    1.0114
Vas=    6.247   liters       6.3359    6.0103    5.8278   4.9388  
Qts=    0.672                .6383     .6722     .6532    .6942
Cms=    994.8   um/N         1024.29   971.649   942.144  798.427   
Pmx=    100     Wrms (nom)      -         -        -         -
Mms=    4.827   gram         4.8273    4.8566    5.4804   5.0888    
Hvc=    8.10    mm              -         -        -         -
Mmd=    4.515   gram         4.5190    4.5483    5.1721   4.7805    
Hag=    4.25    mm              -         -        -         -
Le=     0.463   mH @ 1KHz    .5376     .5059     .5039    .5516   
Xmx=    1.925   mm (nom)
Le=     -----   mH @ 20KHz   .1969     .2107     .2006    .2085

Leakage Flux:   <2 Gauss at any point beyond 70mm from 
                any surface of the driver.
Typical Use:    2-3 liter sealed enclosure operating from 100 Hz
                to 4 KHz.

Note: Driver #4 looked like the suround had been pinched (maybe in shipping ?), which may account for the _off_ specs.