Radio Shack RS 40-1271 8" Full Range Driver

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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.
 

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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

Member
Joined 2003
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
 
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.

ralph-bway said:
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
 
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.

GM said:
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
 
Open Baffle Design

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

Member
Joined 2003
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/tlinespeakers/TLS/downloads/Xlbaffle.xls.zip

For everything else: http://www.linkwitzlab.com/index.htm and his archives: http://web.archive.org/web/20030601163528/linkwitzlab.com/

All this ought to keep you occupied for awhile. ;)

GM
 
More 40-1271 Specifications

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.
 
GM said:

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.

For so-so accurate sims: http://homepage.mac.com/tlinespeakers/TLS/downloads/Xlbaffle.xls.zip

Hi GM,

I have done a lot of reading and tried out that spreadsheet. I just pruchased a 2050 radio shack SPL meter on eBay, so I am looking forward to using it when it arrives.

From the spreadsheet, I got about +/- 4dB with dimensions of:

Baffle Hight (mm) 900
Baffle Width (mm) 350
Hight above floor (mm) 900
Dist. rear Wall (mm) 100
Dist. side Wall (mm) 300

You mentioned your baffle was about 34" (860 mm) across. What height did you use?

Would adding a small cheep tweeter such as the onyoko buyout crossed over at bout 4k help out the high end reasonably?

Do you have any pictures of you 1271 in an open baffle?

Cheers,
GM.
 
You mentioned your baffle was about 34" (860 mm) across. What height did you use?

Hmm, I was going from memory for what the width was at the driver mounting, but the baffles were tapered. Here's the write-up I did at the time:

I took a 4ft x 8ft sheet of plywood and ripped it at
an angle to get two large tapered open baffles,
mounted the drivers at ear height, glued some baffle
stiffeners on, and tilted them back a little. It took
about a pound of modeling clay mixed with fishing
line lead, and bonding the magnet to the frame to
cure most of its ills. They still need clamping
though.

Measure 59-5/16" from one end, and the same on the
other side from the opposite end. Connect the dots
and saw. :^)) You should get two baffles ~ 48"h x
59-1/4"b x 36-5/8"t.

Lay them out so they are mirror image with the slopes
to the outside. Place the cutout centerlines at
38-1/8" up/14" in from the perpendicular side. I
didn't bother to route them out for a flush fit,
instead I covered the area around the driver,
overlapping the driver's flange/gasket/1/2 surround,
with 3/4" open cell foam from the top down to 9-7/8"
below the centerline. It's attached with velcro for
easy removal.

Make adjustable tilt stands, brace and decorate to
suit. If you don't like their Q, experiment with
different thickness fiberglass or acoustic foam
'blankets' stapled over the rear of the driver to
lower it.

Would adding a small cheep tweeter such as the onyoko buyout crossed over at bout 4k help out the high end reasonably?

AFAIK, you are the first person I know of who felt they needed a tweeter. ;) All of us on the FR forum that discussed them considered them more like wide BW 8" tweeters than FR drivers. At most, all they should need is a little top end 'air' if it is a well damped room, so any tweeter that can get to 20kHz with decent efficiency can be capped off super high, 20-30kHz. I believe if you tame its whizzer 'shout' and comb filtering with the diaphragm it will sound balanced enough that you will not feel the need for a super tweeter.

Do you have any pictures of you 1271 in an open baffle?

Sorry, no functioning camera. Anyway, these were just one of several experimental designs to see what performance could be quickly achieved with them, so they are long gone.

GM
 
baffle sizing

GM said:


Hmm, I was going from memory for what the width was at the driver mounting, but the baffles were tapered. Here's the write-up I did at the time:
GM

Tapered! Now you are scaring me. I dunno if I messed somthing up in my calculations. I have attached the frequency response I calculated using these dimensions:

Baffle Hight (mm) 900
Baffle Width (mm) 350
Hight above floor (mm) 900
Dist. rear Wall (mm) 100
Dist. side Wall (mm) 300

It looks reasonable to me considering they are $5CDN drivers. If it wasn't for that dip between about 500 and 800 Hz, I would think it is pretty nice. Have I missed something?

The dimensions of 900X350mm is something that I could work into a room.
 

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Tapered! Now you are scaring me.

Why?! It just averages out the baffle step for a more gradual transition from half to full space.

I dunno if I messed somthing up in my calculations. I have attached the frequency response I calculated using these dimensions:

Baffle Hight (mm) 900/35.43"
Baffle Width (mm) 350/13.78"
Hight above floor (mm) 900/35.43"
Dist. rear Wall (mm) 100/3.94"
Dist. side Wall (mm) 300/11.81"

It looks reasonable to me considering they are $5CDN drivers. If it wasn't for that dip between about 500 and 800 Hz, I would think it is pretty nice. Have I missed something?

Hmm, baffle height and driver height the same, with half the driver hanging off? Not a good plan. Baffle width is OK considering its proximity to the wall/corner, but the dip out around 500Hz makes no sense to me since the driver is already radiating in half space, so from ~539Hz - up will be narrowing with increasing frequency.

My baffle was for placement out into the room a bit, so not suitable for a near wall/corner placement. Still, tapering it should help with smoothing out the dip somewhat down near Fb.

GM
 
GM said:
A pity the Fullrange Forum's archives are inaccessible ...

I feel your pain. I used to visit that site often. There was a wealth of info there. It's mostly all gone now. I wonder if there's a way to find archives of it on some "wayback machine" site.


[Added later.] This just in. There are now zipped up copies at http://fullrangedriver.com/archive/.
The zip files are humungous. I haven't figured out how to make the links work, but it's probably not too hard. Maybe some kind soul could volunteer to host them on the www as HTML with working links?
 
GM said:


Why?! It just averages out the baffle step for a more gradual transition from half to full space.

Hmm, baffle height and driver height the same, with half the driver hanging off? Not a good plan. Baffle width is OK considering its proximity to the wall/corner, but the dip out around 500Hz makes no sense to me since the driver is already radiating in half space, so from ~539Hz - up will be narrowing with increasing frequency.

GM

I don't like the look of a taper. My thinking was to have the driver at sitting ear level, about 900 mm above the floor. So I am not sure if Height above floor refers to the bottom of the baffle, or the location of the driver, I assumed it is the driver location, and therfore the bottom og the baffle would be 450 mm above the floor. If this is not the case, then the response gets all messed up.

I'd like the speaker to look something like the PHOENIX

http://www.linkwitzlab.com/builtown.htm

Regards,
GM.
 
FullrangeDriver.com Archives

Dave Jones said:

[Added later.] This just in. There are now zipped up copies at http://fullrangedriver.com/archive/.
The zip files are humungous. I haven't figured out how to make the links work, but it's probably not too hard. Maybe some kind soul could volunteer to host them on the www as HTML with working links?


Hi Dave,

I downloaded all the zip files and unziped them all into one directory. Then go in that directory using explorer and search the files for whatever text you are interested in. Then, all you are left with are the files that have the text you searched for. Open up one of the files and you are off to the races. All of the links worked for me.

There is a lot of info in there on the 40-1271! :)

Cheers,
GM.
 
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