Fast, fun, Inexpensive OB project

[Pano]

Originally posted by PeteMcK
Love the simplicity of this, my only concern is the efficiency, but you can't have it all....

Yeah, the low effciency is the monster in the closet. But trade offs always have to be made. That is why many open baffle speakers start with very efficient pro drivers. Trade off there is usually higher FS.

Still - these things come out to about 83dB/watt at 8 ohms. Maggies only get that at 4 ohms. A 20W tube amp does just fine on the Manzanitas.

Talked to JB, the designer. He says 25 ohms on the tweeter is correct. Why? Just because that's what worked! And I can tell you first hand the tonal balance was right, tweeter not MIA.

"You have to remember this is a DIPOLE, so there is a substantial rear contribution up to over 2K . [don't forget the] first and second harmonics that the woofer produces and the rear radiation of which is bouncing all around the room reinforcing the total presentation." Says JB.

If in doubt, buy yourself a big varible resistor and dial it up and down to find what works for you. 25R would be your starting point. At least that's what I think.

[lousymusician]

I had the chance to hear the Manzanitas at the NCDIY meet on Saturday. JB was very articulate in presenting the design. They do indeed sound good, though they were handicapped by the room which was way too big for them.

Here's a pic of the speakers and their builder:

[andrew01]

I might be a bit *slow* in understanding , but , how would these have decent midrange ?

[Patrick Bateman]

big kudos for posting such an extensively detailed project!

[grantnsw]

Hi Pano! I'm still intrigued with the Manzanitas...
Although I 'think' I have learnt a lot in this forum...maybe I still know zilch..or 'diddley-squat'?

The 830669 breakup still seems (to me) very difficult to control even with a 12mH choke. I've just been looking at the Peerless 8 Ohm 15" paper cone 830670 -->
http://www.tymphany.com/datasheet/printview.php?id=51

seems better behaved? I wonder if they would be feasible? Or even 2 by the 4 Ohm 830671's in series?

So many parameters to consider here, haha. I thought Qts > 1 was required for OB? Maybe this is why some OB designers opt for the Eminence Alpha/ Beta drivers?

[Rudolf]

Putting the SLS that high in the air sacrifices a lot of (possible) floor gain. On the other hand the tweeter needs to be near the woofer because the crossover frequency looks like anywhere between 1-2 k Ohm.
I would like to see the baffle reaching to the floor with a second SLS connected in parallel and mounted as low as possible. That one may be low-passed first order @100 Hz. May be Martin could have a look at it when simulating the Manzanita.

Rudolf

[Pano]

Originally posted by andrew01
I might be a bit *slow* in understanding , but , how would these have decent midrange ?

Psychoacoustic Jedi mind tricks? I don't know.
Maybe the room fills in the mids via reflections.

Honestly, all of us who heard them answered "No" the the following question. "Do you find them too recessed in the midrange, too laid back?"

After listening to far too much, too many full range drivers, these came as a breath of fresh air. No, they do not have the most refined midrange in the world, but they also don't shout and bite your head off like a lot of "articulate" speakers do.

The proof of concept was that CDs were coming out with cries of "play this one, let me hear this one." A real fun speaker to listen to. Makes you want to listen to music.

Don't over think it. Just accept it for what it is. An easy speaker to build that will give you a lot of musical pleasure. Basta.

Originally posted by Rudolf
I would like to see the baffle reaching to the floor with a second SLS connected in parallel and mounted as low as possible.

Absolutely! And I'm working on a project like that to be a low end "helper" for a fullrange driver. But that's a whole other story.
The concept of the Manzanita is "Most Bang for your Buck" They do it beautifully.

[jamikl]

Hi Pano. I like the look of this one too. Maybe it is time to just listen to the music. I do agree with idea of a second 12" as a bass helper but was wondering about mounting this one in an enclosure to get it lower.
jamikl

[MJK]

As promised, here are the simulation results for this design. The first page is the baseline calculations using the data above and the picture showing the speaker on a stand. The second page is a simulation with a Zobel added to the woofer and decreasing the series resistor for the tweeter from 25 to 10 ohms.

http://www.quarter-wave.com/Simulation_Results.pdf

I think that the design has some real potential. Basically, a passive crossover is possible by reducing the effective tweeter efficiency to 5 - 10 dB below the woofer efficiency. This is conistent with my OB design method article of a few weeks ago. I think more improvements in the response are possible by tweaking the crossover values a little bit.

Study completed, back to what I was working on a few day ago,

[BWRX]

Thank you guys for sharing the design and the subsequent analysis with us. Cool stuff

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