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Open Baffle Epiphany!

dnewma04 said:
Many car speakers use high Q designs because of the leaky environments they reside in. Keep in mind that the drivers that work well are the ones designed to be installed in doors and package trays, not subwoofer type drivers.
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... and in the golden, olden days, many of the speakers were designed/intended to be installed in the rear deck under the back window), with the back wave radiating into the trunk (essentially an infinite baffle).

Fifteen or so years ago, the (cheap) Radio Shack car speakers (most notably the 40-1197, 40-1297, 40-1354, and a few others) had a cult-following in the early extended-range driver circles (e.g., James Melhuish's pioneering "Full-Range Driver Site" and forum) -- they're actually pretty capable drivers (especially given their modest prices and especially when they were on closeout from "the Shack" in the 1990s).
 
Ok, so I had to try it.

I took 2 pieces of plywood ( 30" w x 48" h ), cut a hole centered at 33" high. That's ear level from my Poang chair in the garage.

I installed some 6x9 coaxial Clarion speakers. I had them in small boxes in my work van for a while and they sounded ok.

I hooked them up to an NAD 7140 receiver, and a Rotel RCD 1070 Cd player. The results...well. I listened to a couple tracks off Phil Collins Face Value. Pretty underwhelming actually.

You could call it bad I suppose. Certainly not something I'd want to listen to given any other choice. On par with a clock radio basically, a thrift store one,, one that's been left out in the rain and kicked around a construction site,, and played wide-open all it's life. Terms like revealing, don't immediately spring to mind.

The good news: My curiosity has been satisfied regarding these speakers and a chunk of wood. I killed and hour. The plywood was scrap, so no cost and it's not as cold as predicted today. Only -33 c ( -27 F ) and the wind chill is not -50 c, it's only -44 c ( 47 F ), and the sun is shinning. I'm sure you guys in Tennessee and Texas have no concept of this reality.
 
At 33" up from the floor? You should try inverting them so the driver is closer to the floor because it may cause a bit of lift in the low end. It could make them listenable.

I can empathize with you about the cold. It was -23 yesterday but today we're going up to zero. I may go out with no coat to encourage the spring.
 
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noise gate said:
I'm sure you guys in Tennessee and Texas have no concept of this reality.
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Yeah...no thanks! I'll take three months of +100 F over that ANY day. Hot is uncomfortable....cold flat out HURTS. And chicks shed clothes when it's hot. :D

High will be 80 F today. Sorry.
 
kyle said:
At 33" up from the floor? You should try inverting them so the driver is closer to the floor because it may cause a bit of lift in the low end. It could make them listenable
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Actually I did turn them upside down. Center of the speakers then about 13" off the ground and it helped a lot. Not great by any means, but better. I put on "Corrine Beily Ray ". Female vocals, acoustic guitars, and a string section sounded interesting. I also pulled them away from the wall a bit too.

I'm big into Placement so I also tried them on their sides. Didn't sound as good as speakers on the bottom and with the oval speakers and silver cone material and the Coax centers it looked like some robotic eyes staring at me. Kinda freaky looking.

Interesting exercise, and no regrets. Other than the fact I may have ventured onto another one of life's slippery slopes.
 
Less than full range response can be odd sounding if you've not "enjoyed" it before.

Anybody with dual inputs on the back of their speakers with the strap between low and high sections should try this for themselves. Take out that jumper and listen to just the low side and then just the high side. Be sure and shut off the amp at each stage to be sure and you don't short something. :no:

If you've got even a computer "woofer" around to augment, try it. I had a friend playing around pull out some plastic box kind of woofers one time. Added them in below some small stand mounted 2-ways and the extra that gave it was pretty cool. Done with just enough, you wouldn't have guessed what we were using was so...uh....minimal. Not suggesting this for the long term...just as a learning experience.

EV3
 
I have been fascinated with the OB concept for some time now, but afraid of all the warnings. You know, room placement, baffle size, driver selection, bass issues etc. So I decided to do a quick and dirty proof-of-concept to see for myself. My goal was a simple, inexpensive project using materials and components mostly on hand, except for the drivers. If I liked what I heard I would upgrade the components for the next go round. I bought the cheapest drivers from PE I could find that I felt were suitable for OB. I like 4 ohm drivers. Don't ask. I chose the Goldwood 210/4 10" woofer. It has a sensitivity of 90.6 and a Qts of 1.06. For full range duties I picked the Visaton fr13-4 5" driver. It is basically a car audio speaker but with a Qts of 1.25 I thought it would work for my purposes. It's sensitivity is 88 db. My listening room is my 10' by 12' bedroom so size of baffle was a big consideration. Two small tables and materials dictated a resulting baffle of 17" by 23". I don't have table space for "wings", but I did add half sides to each unit. Construction is mostly pine because that's what I had in the shed. For you serious types, MDF or something similar would be a better choice. Knotty pine is not the best for resonance. I have limited power tools: a screw gun/drill and cordless jigsaw. No router. I would be unable to inset the drivers for this test. All wood parts are glued and screwed together. The finished baffles less the drivers are pretty quiet when I banged on them with my palm. Now for electronics. I'm and old school 2.0 guy. I like lower-wattage receivers. My units that see daily use are either a Vector Research VRX-3500A or Concept 2.5. We talking about 25-35 watts here. It's not been and issue for the size of my listening room by I was concerned that they would be enough for this project. I had two 1.5mh 18 ga. air-coil inductors that were bought for another project but never used. The are not nearly large enough to maximize the fs of the woofer but I had them. They provide a cross of 400 Hz for the Goldwood. I wasn't about to spend $35 apiece for inductors when the woofers cost $17 each. The Visaton has an fs of 100 hz. I tested it out of the box and thought I could detect the beginning of breakup while playing heavy bass notes. So I crossed it with simple electrolytics at 150 Hz. I cut it all out, sawed the holes, and slapped on two coats of poly-u. Installed the goodies and placed them in the bedroom. The sweet spot is propped up in bed. The baffles are against side walls (12" or so away) resulting in a listening triangle of about 8.5' wide and the same deep. They are about 3.5' from the farthest wall. Been very worried about this placement. Oh well, it's a test. Hooked them up to the Vector. Been crapping my pants ever since. Reverb or transients off side walls don't exist. Maybe because these are low-excursion drivers? The sound stage is large. They completely disappear when I close my eyes. Everything is soundstage. Best of all is the imaging I so worried about. It is detailed and consistent from the get go. Vocals come from head-sized heads. Some of you will know what I mean. Bass is tight and more than adequate for me. Vocals from the Visaton are delightful. Cymbal roll-off has to be heard to be believed. Triangles, wood blocks, snares, cymbals all marvelous. The little Visaton is a sleeper. The 150 Hz/400 Hz cross is working beautifully. I can't hear any separation of the two drivers. They are seamed beautifully. This is not the typical result of any of my former projects by the way. I've spent countless hours with toe in/out. Add Polyfill. Subtract Polyfill. Stuff the port. Unstuff the port. I've played with Polyfill more than I've played with.....you know. I realized today that I'm no longer fighting my music. What a relief. Detail is unbelievable. I'm reborn. After a little break-in I began to increase volume. At 1.5 they fill the room and the rest of my house. I can't say that for most of my box speakers. Ported or acoustic suspension. At 3 or so on the volume knob you need to start turning your hat backwards. Clear as a bell. Jesus, Mary and Joseph. By the way, these are not toe or sweet spot sensitive. I don't know why. I did incorporate a Zobel network and a little baffle step compensation for the GW. Delighted. All genres sound good to me with these. That's enough ranting. Just wanted to share a little here. Try some of these folks. A warning, however. You may find yourself regretting the time and money you spent chasing the dream like I have. My box speakers? In the closet(s). I think I can hear them weeping at night. I took a couple of pictures outside for better light. I need a new camera. The left and right units are identical except they are mirrored. Enjoy....Spookerbaffle proto 1 and 2 001.jpg

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I'm happy for you and intrigued, but good god man give us a paragraph space now and then. Just a double tap on the enter key is all it takes.
 
Spooker,

Thanks for taking the time to write up your journey. Fun to hear your success going with what you had available! And it's pleasing to look at even.

It's such a pleasure to hear something go beyond the expectations....rather than the other way around.

EV3
 
Spooker,

I love reading about other folk's OB epiphany as it only re-enforces what I've experienced over the last few years. Thanks for the affirmation.
 
i just picked up 2 h-frames w/ eminence alphas built by a nice guy on audiocircle. thinking i might try the plate amp trick with them.

i see this nice price on PE: http://www.parts-express.com/technics-req0251-1-100w-subwoofer-plate-amplifier--309-046

my question is the wiring. i see the input for the line signal from the preamp but how do i rig up an output to the driver?

for now i'll use my little BR with fostex fe167 drivers for the top end, http://www.audiokarma.org/forums/showthread.php?t=573903 , but looking at building a top module for a another FR driver.
 
OK, here's my first foray. I just mounted these to some leftover OBX that I had lying around and plucked a simple 1-st order 2-way crossover from a bookshelf pair that I had lying around with no drivers.

The drivers here are Morel Integra 12. 12" treated paper woofer and the classic Morel 1-1/8" dome tweeter, horn loaded, and mounted coaxially with the woofer cone. The woofer is a dual magnet, as is the tweeter. The crossover point is somewhere around 2500 Hz I believe with the woofer running full range with no choke.

Rudimentary, but it actually sounds quite good! Need to be within 8 feet of the speakers or the bass drops off like crazy, but within range, the sound is full and very appealing.

With some tweaks, this could be a nice experiment. THANKS ALL!

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So you added the tweeter to make it a coax?

I just ordered a minidsp plus measuring microphone. Will try that in my current OB rig. I'm eager to try out the eq functions in the minidsp.
 
rogerfederer said:
So you added the tweeter to make it a coax?
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No, this was a line that Morel made in the 1990s and 2000s. They added the tweeter. They still sell the Integra Series 5" and 6" via Renaissance Audio.
But the bigger woofer versions are no longer made (they used to make 8, 10 and 12" varieties in both 8 ohm and 4 ohm configs.)

The woofer design is actually very modular. Some of their auto subwoofers use the same components as the standard MW line of woofers, but with a double magnet mounted where the tweeter is seen here and a second voice coil to make a DVC version. Clever.
 
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