[mor2bz]

I have studies the MJK 2way OB and Lampizator's site.  I don't get the p17 lampizator: the
woofer efficiency is only about 4 db greater than that of the midrange, and the mid is 5 ohm
as opposed to 8 for the woofer. this means that the mid will get almost double the power
of the woofer, making for almost equal efficiency of both drivers.  MJK spells out very
clearly the need for the woofer to be much higher in efficiency than the mid.

of course flat response is not everything, but still.   Ideas?

[panomaniac]

No - it's not. But tonal balance IS very important - so it's a good point and a good question.

The p17 uses a woofer that is 96-97dB/W (lets call that 2.83V).
I don't know the sensitivity of the Saba midrange - is it published?  But if it's given as say, 96dB/watt and 5 ohms, then at 2.83V it's going to be up a least a couple of dB. (1 watt into 5 ohms means 2.24V - an 8 Ohm driver at that voltage would be running 0.62 watts.)

So that gives you at least a couple of dB if the Saba if rated 96dB/watt at 5 ohms.  I've never tested a SABA greencone, but the vintage 8" alnico drivers I have tested were closer to about 92dB/watt. Still, the question remains.

[mor2bz]

Furthermore Lampizator recommends a low qts woofer, while MJK repeatedly
advises high qts (1.26 for Alpha 15).  This would seem to further undermine
bass for the Lampizator.   One problem I see (and have heard in the case of
the MJK 2 way OB) is the lack of integration between bass and treble caused by
the great distance between the woofer and the mid (not by any xover problem).

Does anyone have any more info on the JIBBOB design with a series xover?
Can anyone estimate the overall impedance of either the MJK or Lampizator
designs?

thanks

[xyr]

Right now i´m working on some 4 way project, using Tesla alnico woofers, altec biflex 420, saba greencone mid and tweeter.

I see Lukasz now has a 4way like this (only using Isophon instead of Saba).

So why do you need that Altec biflex for? Not happy with Tesla upper bass?

Can you share your planed crossover points?

Any news on your project?

[derik736]

I see Lukasz now has a 4way like this (only using Isophon instead of Saba).

So why do you need that Altec biflex for? Not happy with Tesla upper bass?

Can you share your planed crossover points?

Any news on your project?

actually i was. and still am. I sold biflex. It was ok but didn't bring much to the entire system. Tesla woofers are able to play very good up to 1500Hz. This weekend I will build new baffles with two 15" tesla woofes (each 8 ohm) a side, parallell connected will give 4 ohm to meet the rs of saba. Crossover points for tesla will be appx. 1000Hz.
I have good experience in crossing saba and tesla this way. I did cross saba down to 250Hz (1st and 2nd order) and to 1000Hz. At the end i stood by 1000Hz, since IMHO tesla did very good work playing this high.
I am also a fan of bass reflex enclosures for tesla, this is in my opinion the only option if you seriously think about getting everything that tesla is able to offer. But i will try open baffle anyway. My new room is a giant bass killer, and if OB won't help, than nothing will (except basstrap or electronic correction).

[panomaniac]

Furthermore Lampizator recommends a low qts woofer, while MJK repeatedly
advises high qts (1.26 for Alpha 15).  This would seem to further undermine
bass for the Lampizator.

Not if you do it right.  I ran a low Qts 18" at LSAF and it had no lack of bass or dynamics.
Shallow U baffle on the bottom for the 18" - Altec 15" coax on the top.  Qts was about 0.26 for the 18", similar for the Altec.

[Welborne]

new here.

I use a celestion ftr18-4080f 18" woofer with my Telefunken Oval 11 x 7 " fullrange and a rare isophon 13cm paper tweeter on a open baffle. Shallow u-frame for the 18" woofer and plain board for everything else.

I tried Lampizator's p17 xover. I had problem in matching the sensitivity of mid and woofer, so sometimes i use a VR to attenuate this. The sound is nice. Good thing about this is that I could use my wonderful Nuforce V3 integrated for everything. The bad thing is that there is no way i could add some bass boost that i could with my Reckhorn S-1 crossover when I go active.

I am still in the middle of fine tuning my crossover point. Though I want to follow Lampizator's p17 all the way, I just don't have the same woofer so the safer bet for me would be to go active for the woofer. So most of the time I drive the Telefunken oval (sometimes the gold color Grundig 9") with my Nuforce v3 and put a series 200uf cap to protect the fragile telefunken oval from deep bass below 150hz. Then I drive my 18" open back woofer with Hypex UCD700, crossed around 150hz @24db/octave, with 10db bass boost added to 40hz. My baffle is 50cm wide and 120cm tall.

I am happy with the sound so far. But i think i can still fine tune the xover a bit. I am waiting for Nelson Pass's OB-oriented active crossover B5 to come through.

[Welborne]

a peep from the back.  Qts for the 18" celestion is around 0.3.

Pano, nice to see you here. About woofer qts, correct me if I am wrong on one of my impression:

usually...low qts ----> powerful motor system------> better control----------->better transient------>lower Fs

higher qts -------> smaller magnet------> lower sensitivity ----------------> weaker control --------------> poor transient------>higher Fs

seems most high qts woofers are the cheaper lot...dont' know why

[Morfeus]

I don't know the sensitivity of the Saba midrange - is it published?  But if it's given as say, 96dB/watt and 5 ohms, then at 2.83V it's going to be up a least a couple of dB. (1 watt into 5 ohms means 2.24V - an 8 Ohm driver at that voltage would be running 0.62 watts.)

here we go:





Sensitivity is 95db at 5 Ohm, tweeter is 105db at 5 Ohm:

[panomaniac]

Hey Welborne.  Well kinda-sorta.  The low Qts drivers have a strong motor which means the cone does not "flap around" - so to speak.  That flapping around can be useful as it tends to create a hump at the low end of the driver's range.  That hump or peak can be used to bust the bass and overcome the OB losses.

The trade off being that the high Qts drivers don't sound as tight or dry as the low Q woofers.  Well, they aren't.  But they can have a better tonal balance without heavy EQ or crossover tricks.  That's why people like them.  Easy to use.  The low Q drivers need more EQ to keep the bass in balance.  But you often end up sending the same amount of power to either style driver.

A medium Q driver (~0.7 Qts) works well for me on OB.   Not too loose, but doesn't need huge EQ, either.  You can make it all work, as long as you are aware of what needs to be done.

Getting much response below Fs on a reasonable size open baffle is hard to do.  So low Fs drivers are welcome.

[fivestring]

Absolutely agree with panomaniac, it is the system Q (damping characteristic) that defines the overall sound quality, but only among other things like voice coil travel linearity.
If you don`t know what you`re doing (if you can`t verify the overall frequency response by taking measurements), you can easily end up boosting the bass too much and then even low Qts driver becomes a high Qts one, so to speak.

If you have two different woofers (same size), both of the same Fs, but one with high Qts, the other with low Qts, for the same SPL at certain frequency, say 30 Hz, both will require the same electrical power, there is just no way around it.
As with crossovers, where it is not only the electrical XO slope, but the overall slope (driver fall-off + XO order) that determines the acoustic quality, so with dipole woofer systems it is the end damping characteristic (woofer + boosting/attenuation) that determines what we perceive as "tight" or "loose".

If you work with active systems, you can use the boost at lower frequencies or midrange attenuation of the woofer to linearize the overall system linearity, while in passive systems you can use only midrange attenuation, but even with the active systems I prefer the latter, as it doesn`t affect the corner frequency cut-off slope.

What puzzles me however, is that the only driver that enabled me to clearly hear (in a natural balanced manner) the lowest note on the piano (A2 - 27,5 Hz), was the extremely high Qts Carver Amazing woofer (Qts < 3), which sounded great with all other bass material too.

I can get deep bass with woofers of 0,5 - 1 Qts, but the lowest note on the piano is somewhat weak, so I guess it`s all compromises.

These woofers performed nicely, but the overall build quality was very low:

http://www.dynavox.com/dynavox/Carver.htm

[Welborne]

Hi pano, thanks for answering my question.

so can you recommend some qts ~ 0.7 15/18" woofer that you find good?

I notice Lowther America uses Altec 416a (great plains audio version) to match the Lowther PM5a in open baffle. The qts is around ~ 0.3. but they are over my budget.

Anyone using Azzolina's basso woofer on open baffle?