Fast, fun, Inexpensive OB project

Simple cheap OB's

Built these over the summer for my daughter's bff...

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


total cost was ~ $120 each... they DO have midrange presence, and pretty reasonable bass response... woofers are modified 10" 20 yr old infinity drivers... since refoamed and weighted... awaiting milled cherry trim (when weather improves)

more info if anyone's interested (driver specs, etc.)
John L.
 
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Martin! Thanks so much for the sims. They're very nice.

I don't think the top end is quite that recessed in room, at least it didn't sound that way to me. Could be room dependent.

The sim with the Zobel and lower tweeter R is cool, will have to report back on that. Certainly easy to do.

Just got a measurement on the Qts of the Peerless 12 on baffle. It's up around 0.6, so that changes things. Less efficient than spec, too.



To answer a few other questions..

Yes, you could use another bass driver, maybe the Peerless 15, I haven't heard it. I may try a similar concept with the Seas tweeter and a pair of Selenium 15s I have.

Putting the Peerless 12 in a box is a fine idea, I'd love to mate it with the SS 3800 in a ~3ft aperiodic box - but that's a whole other speaker.

Using 2 woofers would be cool. You get +6dB at the same voltage and you can use an inductor 1/2 the size. But I just don't know how well that second woofer would couple with the tweeter. You would need to roll it off sooner, as Rudolph suggests. That means a more complicated crossover. Remember the title of the thread! :cool:
 
Just got a measurement on the Qts of the Peerless 12 on baffle. It's up around 0.6, so that changes things. Less efficient than spec, too.

Maybe the lower efficiency of the Peerless is why the 25 ohm resistor works well, then the two drivers would be closer in SPL output. I think the Zobel will also help with the crossover and may mitigate the dustcap break-up described above by better rolling off the woofer as shown in the second set of plots.
 
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Re: Simple cheap OB's

Something I forgot to mention;

Felt rings on the tweeters.
If the link does not work, go to www.madisound.com and search for "felt". These are rings to help diffraction issues if you can't flush mount the tweeters.

If you look at Martin's sims, you'll see a lot of "Sputter" in the FR graphs. Most of that is due to the square, sharp baffle edges. A big round over will help smooth out a lot of that. Same goes for flush mounting the tweeter, or using a felt ring.


BWRX said:
An active crossover version of this would be interesting to compare to the passive version.

Yes, it would. I think a simple 1st order PLLXO in front of the bass amp would do the trick. Put the XO frequency at about 100Hz. You should end up with a similar response to Martin's sim with the Zobel.

Going to be harder with the tweeter, as the passive does some phase tricks and curve tapering that a textbook 2nd order does not. Worth a try, tho!


auplater said:
Built these over the summer for my daughter's bff...


Yeah, those are cool, love 'em! I've seen them in some of your other posts. Are you happy with the clear drivers? And how do the twin mids treat you?
 
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Just so you don't think I'm kidding you about these simple speakers, here is an article about their appearence in Dallas earlier this year at the Lone Star Audio Fest. Some more photos here. They don't look pretty, but they sure do sound pretty.

Lone Star

After Dallas, there was a lttle run on parts for the Manzanitas at Madisound. :)
 
"welcome to the nightmare"...

or so goes the Alice Cooper song.

so I did a little "reverse" thinking (I'm good at thinking backwards...:) )

if the speakers are mounted on the (approximately) 10 degree "rear" side of the external brace, at 12' ( typical listening distance for many I think), then the result is an on axis (to the woofer) listening position of about 37.5"... a typical listening height. The benefit is as the "JE Labs style" open baffle--quite spectacular bass from an open baffle. A reverse polarity tweeter could tilt it's rsponse 15 degrees or so lower...

As Mr. King points out, this design has some merit. And who cares if it is a little ugly?

Actually, I 've seen floors done in OSB. Basically stained and covered with epoxy. The look marvelous. And the use of some dampening material , although perhaps not absolutely needed, may help with reflections of the rear wave back onto the rear of the cone.

Every day I see and learn something new here. Or at least something interesting....

Now mount the tweeter co-axially and it could get more interesting yet.

stew
 
Re: "welcome to the nightmare"...

Nanook said:
Actually, I 've seen floors done in OSB. Basically stained and covered with epoxy. The look marvelous. And the use of some dampening material , although perhaps not absolutely needed, may help with reflections of the rear wave back onto the rear of the cone.

stew [/B]

Hi!
Apply a black stain directly on the board (sanding before of course)
Then tint clear lacquer with a black dye. Dye is important as it is more transparent than a pigment. Of course if more hiding power is required, by all means, mix pigment in lacquer also.

If a high gloss lacquer is used, you will have a look of polished marble or simular stones. I've done a lot of work in my occupation
with board producers but with a different angle.
We tinted the glue, black, blue or whatever colour, in the manufacturing process to save time in the staining process of the board. Then lacquer tinted in finishing process, resulted in quite a nice look despite the crappy chipboard.

Just a suggestion....

Peter

Of course, spraying ecquipment obligatory!
 
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Good ideas on the chipboard finishes! I've heard that it can look really nice, but never seen it.

As for the dye tint for the lacquer, is that something easy to find? Will one find 2 different types of of tint - dye and pigment?
 
Hi,
Well, if you got to a retailer, who sell lacquers and paint to joiners, they must know the difference between dyes and pigments.
In order to have more depth or transparency, it's better with dyes. Black dye has a violet tone. Look at Dave-Planet10's "black" coated FE127. I'm 99% sure it's a dye involved. Correct me if I'm wrong, Dave!

Pigments, in general; has a more "dirtier" look but has more hiding power/covering.
You can use black + a bright violet pigment(=expensive) to make a good pitch black effect with more hiding power if required. Often used in car industry.

Cheers

Peter
 
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panomaniac said:
Good ideas on the chipboard finishes! I've heard that it can look really nice, but never seen it.


This is a ridiculously bad photo but...It's a dual 10" sub that I built a couple years ago. It is 3/4" plywood with 1/2" OSB on the outside. I painted it black then sanded it ( black stayed in the crevices and pits). I then gave it a coat of a mixture of clear gloss solvent based urethane, red oil paint and black oil paint. I got a kind of "candy apple" look.
A neat finish, quite different.
 

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Hi

BWRX said:
Thank you guys for sharing the design and the subsequent analysis with us. Cool stuff :up:

An active crossover version of this would be interesting to compare to the passive version.


BWRX, here it is....

-----------

Panomanic, thanks for documenting this nice project of John Bush here.
As I had a Peerless at hand I thought I give it a try. Good bang for the buck indeed.


As I didnt have the " right " tweeter for the Manzanita 12, I built it with the Seas Millenium ( and an old ScanSpeak to the rear )



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Built in half a day.



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Total frequency response. Just white noise averaged 50 times at a distance of roughly 1m



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The XO is basically the same as in passive.


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FR of the Peerless SLS12 alone


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EQ1 was done for flat FR – and FUN ;)
+6dB / 28 Hz Q=2 will be plenty for normal listening though


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EQ2 shows the need of high shelving. The notch at ~ 50 Hz is to equalise my room resonance.



Its fun to build and fun to listen at !

Greetings
Michael
 
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Hey Michael - that's great!

I'd love to hear your version, but the hills of Austria are just a little too far from the hills of Hawaii. =)


Nice work. And thanks so much for the graphs and measurements - they go a long way to explaining what is going on. What is the crossover software you use?

I'm suprised at how flat you got it. Just seems to be a peak at 3Khz. Cone break-up? Baffle nasties?

My main question would be this:
Given that your measurements show flat (more or less) at 1M in front of the baffle, do they not sound too bright in room? Is there a lot of mid energy coming off the back of the Peerless and filling the room?

The original pair have a big midrange dip in the crossover to counter the midrange energy coming from the back. I see that your soft crossover does the same thing, but the resulting FR looks a lot flatter than I would have expected!

Thanks for pursuing this fun little speaker. Maybe it will encourage others to give it a try.
 
mige0 said:
Hi

Total frequency response. Just white noise averaged 50 times at a distance of roughly 1m

Its fun to build and fun to listen at !

Greetings
Michael

Hi michael, could you (and others) comment on this please. I'm curious about using white/pink noise when setting up speakers to be flat.

Basically, when do we use which?? They are very different sounds, and so when we make the speaker flat on each, well they will sound very different won't they??

Additionally, what is the difference again if we use a swept signal?




panomaniac said:
Thanks for pursuing this fun little speaker. Maybe it will encourage others to give it a try. [/B]

I have this thread bookmarked for a later date Pano!! I doubt (at the moment) I would go passive with it, but hey the network is so simple that why not?? ha ha.
 
panomaniac said:

Oh, just looked at the graphs again, it's a 300Hz peak, not 3Khz. My mistake. That points to the baffle edges, I suppose.

I was curious about this too, and your guess is spot on. Would experimenting with baffle edge (making it progressively narrower, to a point) help, or should we attack it differently (moderate Q anti resonant LCR targeted at 300Hz) ? I'm extremely intrigued by this development as I still like the idea of multiple SLS's on a large-ish baffle as bottom end of a Arvo/R909 like 'clone'.

Bratislav
 
panomaniac said:


Oh, just looked at the graphs again, it's a 300Hz peak, not 3Khz. My mistake. That points to the baffle edges, I suppose.

Bratislav said:


I was curious about this too, and your guess is spot on. Would experimenting with baffle edge (making it progressively narrower, to a point) help, or should we attack it differently (moderate Q anti resonant LCR targeted at 300Hz) ? I'm extremely intrigued by this development as I still like the idea of multiple SLS's on a large-ish baffle as bottom end of a Arvo/R909 like 'clone'.

Bratislav

I do not believe the peak at 300 Hz is generated by the baffle or the sharp baffle edge, my guess is it comes from the driver or is an artifact in the measurement equipment/set-up or input signal.
 
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MJK said:
I do not believe the peak at 300 Hz is generated by the baffle or the sharp baffle edge, my guess is it comes from the driver or is an artifact in the measurement equipment/set-up or input signal.


Is 300Hz too low to be caused by this size baffle, or is it the shape of the peak that points elsewhere?

Really, the FR looks very good. Just wondering about the little bump.
 
Is 300Hz too low to be caused by this size baffle, or is it the shape of the peak that points elsewhere?

I believe it is both. If I model the biggest possible baffle size, include the rear wings as part of the front baffle, the contribution to the response from the baffle peaks at about 400 Hz and produces a broad hump that spans 150 Hz to 700 Hz. A smaller baffle representation will shift this hump higher in frequency. The relatively narrow and sharp peak at about 300 Hz just does not look like anything generated by a baffle, it looks more like a driver or room resonance of some kind.