Fast, fun, Inexpensive OB project

[auplater]

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







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.

[Pano]

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!

[MJK]

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.

[Pano]

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.

Originally posted by BWRX
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!

Originally posted by auplater
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?

[Pano]

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.

[Nanook]

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

[peterbrorsson]

Originally posted by Nanook

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!

[Pano]

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?

[peterbrorsson]

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

[MJL21193]

Originally posted by panomaniac
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.