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Author Topic: Homebrew speaker  (Read 6963 times)
KJ6ZOL
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Posts: 389




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« on: December 01, 2012, 03:15:09 AM »

I just realized that my Elmer forgot to give me a speaker for my Kenwood. He included a speaker for the Heathkit SB-102, but it has an RCA jack (as opposed to the Kenwood's 1/8") and it's attached to a bulky HP-23A power supply. I'm thinking of simply buying a 8 ohm speaker and a 1/8" jack, hooking the two with speaker wire (of which I've got plenty), and plugging it in. An external speaker is basically a speaker in a box, so this would be a speaker sans box. I'm not the type of guy to care about looks. My question is, will it work? Did anybody do this when they were a young, broke newbie like me?
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KA4POL
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« Reply #1 on: December 01, 2012, 03:37:24 AM »

It should work.
You did not say what the 'Kenwood' is, but the output impedance for the speaker should be fine.
Of course there is a reason to put a speaker into a box. It is protected against damage of the membrane and to a lesser extent short circuiting. So at least put some cover on the membrane outlet.
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K1CJS
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« Reply #2 on: December 01, 2012, 04:49:56 AM »

There are speakers and there are speakers.  Yes, it will work, but probably not as good as a 'communications' speaker would.  A communications speaker has its greatest response in the middle portion of the audio range.  It isn't as responsive in the high portion--as a 'tweeter' speaker would be, nor in the lower portion--as a 'woofer' speaker would be.

In short, any speaker that is labelled as a 'mid-range' speaker should make a pretty good comm speaker.

Added--Of course, there are purists and audiophiles that would disagree with that.  Just as an example of a personal nature, I made a comm speaker enclosure out of five squares of plywood, a perfboard, and some framing wood.  It wasn't built/made to any sort of plan or research, wasn't fancy or even good looking--but it worked as well --or even better--than some store bought speaker that was made and marketed as a communications speaker!
« Last Edit: December 01, 2012, 04:53:57 AM by K1CJS » Logged
KJ6ZOL
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Posts: 389




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« Reply #3 on: December 01, 2012, 04:59:06 AM »

It should work.
You did not say what the 'Kenwood' is, but the output impedance for the speaker should be fine.
Of course there is a reason to put a speaker into a box. It is protected against damage of the membrane and to a lesser extent short circuiting. So at least put some cover on the membrane outlet.

Sorry. TS-130S. 1980s vintage.
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KA4POL
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« Reply #4 on: December 01, 2012, 07:58:26 AM »

The output impedance is 4 to 16 Ohm according to the manual at 1.5 W for 8 Ohm. So you will definitely be fine.
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WB6BYU
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Posts: 13341




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« Reply #5 on: December 01, 2012, 08:34:04 AM »

If you don't care about the cabinet matching, most speakers will work.  You
can get (or make) connector adaptors as needed.


When I read the title of a "homebrew speaker" I though you might be looking
for plans for a resonant speaker enclosure that acts as a CW audio filter, or
even a build-it-yourself speaker like this:
http://www.intio.or.jp/jf10zl/speaker.htm
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K0JEG
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Posts: 670




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« Reply #6 on: December 01, 2012, 08:43:16 AM »

I just realized that my Elmer forgot to give me a speaker for my Kenwood. He included a speaker for the Heathkit SB-102, but it has an RCA jack (as opposed to the Kenwood's 1/8") and it's attached to a bulky HP-23A power supply. I'm thinking of simply buying a 8 ohm speaker and a 1/8" jack, hooking the two with speaker wire (of which I've got plenty), and plugging it in. An external speaker is basically a speaker in a box, so this would be a speaker sans box. I'm not the type of guy to care about looks. My question is, will it work? Did anybody do this when they were a young, broke newbie like me?

While a bare driver will produce sound, I wouldn't call it a speaker. Drivers are designed to be put in an enclosure, usually just a simple air-tight box will suffice. The main reason is because the air in the enclosure acts like a spring or dampener for the driver's cone, making it much more efficient and also increasing the linearity of the frequency response.

You really don't need much of a box to make drivers work better either. An old Pringles' can might work for small drivers, a disposable plastic container, just about anything that can be sealed tight will work.
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K8AXW
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« Reply #7 on: December 01, 2012, 09:14:42 AM »

In my earlier years of hamming I used speakers sans box.  I found early on that a speaker in a box, any box, sounds much louder than a speaker without a box. 

The speaker in a box brings out the lower frequencies.... not only sounds better but also seems to increase the volume.
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KE3WD
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« Reply #8 on: December 02, 2012, 02:14:04 PM »

The box is a functioning part of the loudspeaker. 

It is actually called a BAFFLE.

Speaker with no baffle will not sound as loud because the air being pushed at front is having to deal with an equal amount of air being pulled from back at the same time, and vice verse when the cone moves in the other direction.  This can create Phase Cancellations, which not only robs energy, but also can cause frequency shifts. 

For Ham Radio use, a baffle on the speaker can make weaker signals more easily readable. 

A baffle can also increase the amount of time you can listen without Ear Fatigue setting in.

Put the speaker in an enclosure of some fashion.


73
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KD0REQ
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« Reply #9 on: December 03, 2012, 10:09:56 AM »

back in my first job, radio program studio work, the monitor in the control room was a ceiling panel job like you'd find in the airport or a restaurant.  put an open cardboard box over it, and some moderately heavy piece of crap on top of that, and while it wasn't the Sentry 1 in the studio, it was now tolerable.

many times since then, if I had a random speaker and I wanted to build an enclosure, I'd put a source on the speaker, and take sheets of cardboard and some masking tape, and fiddle them around until I got a reasonable bandwidth at low volume.  play with porting a little bit, make adjustments, and then measure and cut the wood.  if you don't have the Thiele parameters, and just want a decent smooth result, it's fine.
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KE3WD
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« Reply #10 on: December 03, 2012, 11:26:41 AM »

That's the spirit! 

Years (decades, actually) ago this kid found out that a naked magnetic loudspeaker sounded not so efficient and discovered quite by accident that even adding a single board with hole, mounting the speaker to it, created enough baffle to make the thing sound much better. 

This because I was setting out to build an entire wooden baffle enclosure for my little 3-4 ohm speaker with Alnico magnet that had been removed from some old TV or Radio, to use with my then new Heathkit HR-10 receiver. 

Well, not having access to power tools other than an old 1/4" hand drill, I set about the task of hand sawing the square frontboard, then laid out the big circle for the speaker in the center area and spent time with the coping saw to cut out the circle.  By the time I had that part done, my free time for hobbies was almost exhausted for that school day, but I took the time to screw the speaker to that newly cut front plate and took that assembly back upstairs with the intention of finishing the rest of the open-back baffle box on a later date. 

Evening came around, homework got finished and there was some time left over to do a bit of shortwave listening, so I connected that speaker and board to the old HR-10 and immediately noticed a much better and fuller sound to the thing than previously, plus a bit more low-mid to low end response. 

Propping the speaker on the board up to an almost upright slanted angle between the real wall of my desk and the top of the receiver created the rest of my ersatz baffle. 

Worked so well that it was months before I got around to  making the sidewalls for the box. 

Since that day of learning, have pressed many things into service for use with old speakers on receivers and other audio things around the shack. 

**There was the time I had a nice 12" fullrange speaker with no cabinet and simply stuffed some rags down into a plastic wastebasket, laid the wastebasket on its side and propped the naked loudspeaker up in front of and slightly leaning on those rags.  On the AM band, the bass response increase was incredible.**

No, my wastebasket baffle was NOT Theile aligned.  <g>


73
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KD0REQ
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Posts: 972




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« Reply #11 on: December 04, 2012, 10:01:29 AM »

theoretical designs of speaker enclosures, I have been told at some point in the past, have a base on the "infinite baffle..." namely, the speaker mounted in the center of an infinite board.  KE3WD just never finished his Wink
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KE3WD
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Posts: 5689




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« Reply #12 on: December 04, 2012, 05:38:39 PM »

theoretical designs of speaker enclosures, I have been told at some point in the past, have a base on the "infinite baffle..." namely, the speaker mounted in the center of an infinite board.  KE3WD just never finished his Wink

Actually, the terminology is the other way around. 

The "Infinite Baffle" is when the speaker is entirely enclosed in an airtight box, no porting whatsoever. 

The Infinite Baffle is a very efficient design, pushing the midrange is the reason, but lacks low frequency efficiency. 

The Infinite Baffle takes advantage of air pressure to return the cone to center with a bit more energy than available from just voice coil vs magnet action, as would happen in any baffle that has an opening in it, be that open back or ported. 

Infinite Baffle is often a good choice for Communications Speaker, for the above reasons are sometimes rather desirable. 

73
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WB2WIK
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Posts: 20612




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« Reply #13 on: December 06, 2012, 10:32:05 AM »

I just realized that my Elmer forgot to give me a speaker for my Kenwood. He included a speaker for the Heathkit SB-102, but it has an RCA jack (as opposed to the Kenwood's 1/8") and it's attached to a bulky HP-23A power supply. I'm thinking of simply buying a 8 ohm speaker and a 1/8" jack, hooking the two with speaker wire (of which I've got plenty), and plugging it in. An external speaker is basically a speaker in a box, so this would be a speaker sans box. I'm not the type of guy to care about looks. My question is, will it work? Did anybody do this when they were a young, broke newbie like me?

Of course it will work, but it may not sound as good as the speaker that's already in the TS-130S.

Why would you want an external speaker? Wink

If you want to "hear stuff better," cheap headphones are usually better for hamming than any kind of speaker.
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AB2YC
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Posts: 53




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« Reply #14 on: December 06, 2012, 11:22:27 AM »

When I was a kid I built a number of speaker cabinets out of cardboard boxes.

Some actually sounded fairly decent.





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