Radio Shack RS 40-1271 8" Full Range Driver

[gmilitano]

I visited a small authorized Radio Shack Dealer (small town) and I came across two drivers in the clearance bin for $5 each. The list price was $30 each, so I figured I would pick them up for the hell of it. The drivers are Radio Shack 40-1271. These are 8" full range speakers with a dual cone (it is hard to see the smaller cone in the picture).

The specifications on the box are:

Impedance: 8 ohms
Magnet Weight: 81 g
Freq. Response: 75 - 20,000 Hz
Sensitivity (SPL): 88 dB
Power Handling (RMS): 5 W
Power Handling (MAX): 10 W
Cone Material: Paper

I listened to them a bit, and the mid-range sounds good, However, I don't think the driver really gets down to 75 Hz. The magnet also seems a little on the small side. I didn't buy the driver with any plans in mind, so I am looking for suggestions. I figure the worst case is that I can use them as ceiling speakers in the kitchen or some place silly.

Does anyone have any information (specifications, response curves, projects ...) for these drivers? What is a good way to break in the drivers? Is listening to music good enough?

I have been playing around with Speaker Workshop a little bit and I guess I could try measure the drivers myself, however I am a little reluctant without some hands on guidance. It would be really great if there were someone in Winnipeg who could give me hand with Speaker Workshop.

I'm looking forward to any infomation, comments or suggestions.

Regards,
GM.

[ralph-bway]

Hi GM,

I bought similar RS (40-1288) 8" full range speakers on clearance almost two years ago. After looking at the specs (similar to yours) and playing around with box sizes on WISD, I just didn't think they were worth the time & effort to build a cabinet for.

I think I'll just puzzle coat them and stick them in the shed/workshop in a quick & dirty box with a couple of the PE 24 cent Onkyo tweeters (the 3/8" jobs which I have a few of).

There are a lot of folks here who know much, much more than me and I'll keep a look on this thread to see if someone comes in with a better idea.

Good luck.

Ralph

[GM]

A pity the Fullrange Forum's archives are inaccessible for now since this driver, as well as many of the other discontinued RS drivers are discussed at length. Anyway, here's the specs for the 40-1271:

83Hz Fs
1.16ft^3 Vas
9.45 Qms
3.3 Qes
7.9 ohms Re
6.5" diameter
0.04" Xmax (assumed)
2.1mH Le
89.4dB/w/m

As you can see, OB or aperiodic combined with a LF driver are best. They also need the usual cheap driver tweaks for best performance: damping the basket, gluing the motor to the frame, the $0.98 whizzer tweak, mass loading the driver, etc.. Basically though, they are 8" mid/tweeters of limited output/dispersion.

GM

[gmilitano]

Hi Ralph,

Thanks for the input. I lisented to the drivers a little bit, and they sound like they need more low end help as the midrange seemed good. A tweeter may help a bit on the very hi end.

What is puzzle coat?

Cheers,
GM.

Originally posted by ralph-bway
Hi GM,

I bought similar RS (40-1288) 8" full range speakers on clearance almost two years ago. After looking at the specs (similar to yours) and playing around with box sizes on WISD, I just didn't think they were worth the time & effort to build a cabinet for.

I think I'll just puzzle coat them and stick them in the shed/workshop in a quick & dirty box with a couple of the PE 24 cent Onkyo tweeters (the 3/8" jobs which I have a few of).

There are a lot of folks here who know much, much more than me and I'll keep a look on this thread to see if someone comes in with a better idea.

Good luck.

Ralph

[gmilitano]

Hi GM,

Thanks for the specs, that is a good start for me. Are response curves also available for this driver?

I guess I will have to wait for the Fullrange archives to come online as I imagine most of my questions have already been answered.

I'm not familiar with the cheap tweaks you are talking about. IS more information available regarding these tweaks?

With those high Q values I guess I should be looking at an open baffle system. I will have to do some more reading.

Regards,
GM.

Originally posted by GM
A pity the Fullrange Forum's archives are inaccessible for now since this driver, as well as many of the other discontinued RS drivers are discussed at length. Anyway, here's the specs for the 40-1271:

83Hz Fs
1.16ft^3 Vas
9.45 Qms
3.3 Qes
7.9 ohms Re
6.5" diameter
0.04" Xmax (assumed)
2.1mH Le
89.4dB/w/m

As you can see, OB or aperiodic combined with a LF driver are best. They also need the usual cheap driver tweaks for best performance: damping the basket, gluing the motor to the frame, the $0.98 whizzer tweak, mass loading the driver, etc.. Basically though, they are 8" mid/tweeters of limited output/dispersion.

GM

[ralph-bway]

Puzzlecoat is like Elmer's glue. A thin coating stiffens the speaker cone while remaining very flexable. I found out about it from posts on different threads.

[miguel2]

Puzzlecoat

Isn't that going to affect the high frequency characteristics of the driver?

Anywas, I am interested too in more information about the tweaks mentioned

damping the basket, gluing the motor to the frame, the $0.98 whizzer tweak

Miguel

[gmilitano]

I have decided that I will try these in an open baffle system. I will use them with a small 8" sub to pick up the low end.

Are there any good websites or software that can help me with an open baffle design? Given that this driver has an Fs of about 83 Hz, I guess I should look at a baffle tuned to about 80 to 90 Hz. I found a chart on the single driver website:

http://melhuish.org/audio/baffle.html

Based on that chart, if I want to tune to a frequency between about 80 and 90 Hz, I need a baffle length of about 35 to 40 inches. However, there are no comments with regards to the baffle width? So, how is the width determined?

Any info would be appreciated.

Cheers,
GM.

[GM]

Hi GM,

Thanks for the specs, that is a good start for me. Are response curves also available for this driver?
=====
Digging around in my old posts, I published this:

To get a general idea of it's FR I used an RTA/pink
noise/peak hold feature (best I can do for now), with
the raw driver (no mods other than damped frame)
suspended 4ft off the floor in the middle of a 16ft x
27ft room, and the mic at 1/4" from the whizzer
(further away and the room starts affecting it):

25Hz = 0dB
40Hz = +6dB
63Hz = +12dB
100Hz = +14dB
160Hz = +10dB
250Hz = +8dB
500Hz = +8dB
1kHz = +10dB
2kHz = +8dB
4kHz = +6dB
8kHz = -2dB
16kHz = -4dB

As you can see, the ultra high Q causes a
considerable peak spanning the <63 - >160Hz BW, so
this particular driver needs a baffle that averages
~34" across, which is a hair smaller than what I
tried awhile back that seemed to work so well. This
should give ~ +/-3dB to ~2.3kHz, where it should
begin to beam.
====
>I'm not familiar with the cheap tweaks you are talking about. IS more information available regarding these tweaks?
====
Well, if you rap on the frame you'll see it rings, so it needs to be damped with Ductseal, oil based modeling clay, or similar. Ditto the motor. Stick some on the inside as best you can to reduce reflections back through the cone. The motor isn't attached very securely so I fill the gap with epoxy, though some folks just fill it with the damping material. Here's the $0.98 tweak: http://www.mindspring.com/~darmah/lowther/mods.htm Here's the bracing/mass loading scheme, though you'll have to adapt it for use on an OB: http://melhuish.org/audio/images/press-screw.gif Doping with Dammar to damp and/or shellac to stiffen is for fine tuning, but you need to experiment, which of course means you run the risk of ruining them, so save this for when you tire of them.
====
>Are there any good websites or software that can help me with an open baffle design?
====
For so-so accurate sims: http://homepage.mac.com/tlinespeaker...baffle.xls.zip

For everything else: http://www.linkwitzlab.com/index.htm and his archives: http://web.archive.org/web/200306011...nkwitzlab.com/

All this ought to keep you occupied for awhile.

GM

[gmilitano]

For those interested, I have found some more specifications which match closely to the ones than GM posted.

===
Source: http://melhuish.org/audio/parameters.html#radioshack

Radio Shack 40-1271C drivers after break in (from John Wyckoff). Three samples:

Fs 84 81.7 83.1 Hz
Vas 1.1 1.2 1.17 cu ft
Qts 2.4 2.45 2.43
Qes 3.3 3.3 3.3
Qms 9.5 9.4 9.45
Mms 7.5 7.46 7.5 g
Bl 3.1 3 3 T/m
Re 7.75 8.1 7.9 ohm
Le 0.18 0.21 0.2 mH
Eff (SPL) 89.5 89.47 89.45 dB 1W/m

These drivers are finding a following among the "cheap-n-cheerful" fans of Radio Shack drivers, some people liking them better overall than the 1197 and 1354. Due to the high Qts, use these in an open baffle arrangement.
===


It sounds like this driver was discussed in detail on the single driver forum. I am looking forward to the archives becoming available.

Cheers,
GM.