improved scans of the 40-1354
Oct 12, 2001 at 3:08 AM Thread Starter Post #1 of 18
Budgie

Budgie

Never looks a gift amp in the jackhole.
Joined
Jun 22, 2001
Posts
2,158
Likes
31
I scanned the frequency response graph and the parameter printout for the 40-1354 driver for your viewing pleasure. (You can actually see it, now.)

PS. the driver was not broken in for these measurements, and will change with break in.

http://spiritone.com/~bdg/
 
Oct 28, 2001 at 7:41 AM Post #6 of 18
In my small bookshelf-sized sealed box, based on the measured perimeters of that RS 40-1354 speaker, I wound up with a design that's "optimally" flat in bass response for a sealed acoustic-suspension design (remember, Q rises in an enclosure); that is, the Q of the 1354s in my homemade box is 0.71! If you are going to build a sealed acoustic-suspension speaker system, try to get the actual Q of your design between 0.7 and 1.1 for best results (however, some woofers just won't work well in a sealed box of a reasonable size due to their relatively high Q - especially if the Q of an enclosed speaker goes above 2).
 
Oct 28, 2001 at 10:27 PM Post #8 of 18
Budgie: The volume was just a guess... 285.75x177.8x120.65 mm = 6.13 liters, or 11.25x7x4.75 inches = 0.216 cu. ft
wink.gif


If I went with a smaller box than what I used, the Q will actually be higher than the "optimal" 0.71, which will result in a response peak in the upper bass, and bass extension that doesn't go as deep as it should. The total sealed-enclosure speaker system Q of 0.71 is the best compromise between flat bass response and bass extension; a lower overall Q means that the bass will be too flat (and sometimes too weak, as well).
 
Oct 29, 2001 at 2:09 AM Post #9 of 18
but a lower Q will also mean better transient response. so it's a matter of whether the priority is bass or transient response.
 
Oct 29, 2001 at 2:19 AM Post #10 of 18
Right. What I'm trying to say, skippy, is that an overall sealed-box speaker-system Q of 0.707 (rounded to 0.71) is the best balance between bass and transient response. But a very large sealed-box system that I had built (3.02 cubic feet!) using a "made-in-USA" RatShack 40-1026 12" poly woofer (discontinued) gave me an overall Q of 1.6! ARRRGH! That's because that 1026 was a fairly high-Q woofer (Qts=0.665 and Vas=15.5 cubic feet, according to the specs). No wonder - though that large system has plenty of bass extension, it has a flaw in the mid-bass which an "enthusiast"-level music listener will notice. That's almost as crappy as the bass on those Sony MDR-V700DJ headphones that I listened to a couple of weeks ago! And based on the *Fs / Qes* formula, the 1026 works best in a sealed enclosure - and a REALLY huge one, at that!
mad.gif


BTW, I just checked the Qes and Fs specs of the 40-1354A, and found out (using the *Fs / Qes* formula) that it works best in a vented bass-reflex enclosure. The approximate internal dimensions of that vented bass-reflex box that delivers "optimally" flat response from the 1354's (not including the thickness of the cabinet material) are:

H=15.5 inches/393.7mm
W=9.5 inches/241.3mm
D=5.75 inches/146.05mm
Vent/port tuned somewhere between 55Hz and 57Hz
Volume=0.49 cu. ft./13.87 liters

Heheheh... That's almost the EXACT actual internal volume of that Hawaii 5.0 box for that 40-1354A full-range speaker!!! You guys are nuts trying to extract that last ounce of bass extension by putting those 1354's in a WAY too big voigt-pipe box!
eek.gif
You'll end up with that speaker being forced to reproduce frequencies that it normally can't do! Face it, build that 1354 in that Hawaii 5.0 box - and settle for bass extension down to only 50Hz. DUH!
tongue.gif


And another thing, here are two new-model RatShack full-range dual-cone speakers someone should try in an oversized voigt pipe box (though I haven't heard either speaker): the five-inch 40-1041 and the six-inch 40-1042. With a relatively large cone area (for a full-range speaker) and "only" an eight-ounce magnet (for the 1042) or a 3.5-ounce magnet (for the 1041), its Qts should be somewhat on the high side.
 
Oct 29, 2001 at 5:58 AM Post #11 of 18
hawaii5.jpg


i've got a set of hawaii's sitting in my room now. they're pretty nice, but i'm not to keen on the sound. i should have just bought a pair of psb's or something instead. i just guess fullrange isn't for me.
 
Oct 29, 2001 at 6:47 AM Post #12 of 18
Multi-way speakers are not only difficult to design properly, but are all too easy to screw up as well! In that "vented" box whose internal volume is 0.541 cu. ft. (15.32 liters) I have the original RatShack 40-1024 8" poly woofer and a Linaeum dipole tweeter is on top. Huh? When you put that 8" woofer in a vented box whose internal volume is smaller than the "optimally flat response" volume, the system's overall Q goes waaaaaay up! Its Q is, in fact, greater than 2!!! (That same woofer, in the same size box that's sealed rather than vented, has an overall Q of 1.2.) And the frequency response is screwed not only because of that fact, but also because RatShack's 8" and larger woofers don't even reach into the upper mids - let alone the lower treble! That makes a proper 2-way system extremely difficult to design! That tweeter would have to be crossed over at a lower frequency than is desirable just to get into the upper reaches of the woofer! I get recessed upper mids from that system! (Sure, I could design a 3-way system, but that would have increased the enclosure size beyond what I had wanted to be with that woofer at the time I built it.)

BTW, that 40-1024 woofer's "optimally flat response" vented-enclosure volume turned out to be 7.02 cu. ft. (198.78 liters) - which will result in a much bigger enclosure than that used in the average 15" 4-way system!
eek.gif
 
Nov 2, 2001 at 3:08 PM Post #13 of 18
I found out that in my "optimally flat bass response" sealed box with the 40-1354A speakers, the bass response is down -3dB somewhere between 90Hz and 100Hz - and the bass response rolls of at -12dB/octave below that -3dB point. However, in that Hawaii 5.0 ported box, the -3dB point is about 51Hz - but the response falls off at -24dB/octave below that point!
eek.gif


With my sealed-1354-box combo and my Pioneer SX-2600 receiver from 1990, I actually have some use for the 100Hz band of the receiver's 5-band equalizer: I boosted that band +2 clicks (out of +5), which delivers a +3.2dB boost (out of +8dB).
 
Nov 2, 2001 at 3:58 PM Post #14 of 18
RS (accidentally) makes some good speakers sometimes. I have a set of the Old Pro LX-4 matched from 10 sets my brother had. These came before the LX-5 and had a small vented wooden enclosure. The drivers are a Linaeum dipole tweeter and a special 4" Kevlar woofer. This is one of the finest speakers I have heard when combined with the proper subwoofer. Actually sounds great with the old Advent passive sub.
These have become a cult classic worth many times the original price.
Dan
 
You must log in or register to reply here.

Users who are viewing this thread

Total: 2 (members: 0, guests: 2)
Back
Top