audio-talk

In his small SLOB design Nelson Pass used Eminence Definimax 4015ULF bass units but these have now been discontinued and the only way I can get a pair is by paying rediculous shipping and import costs to get them from the US. As a result I've started to cast around for an alternative.

Browsing the Blue ran site I spotted these;

https://www.oberton.com/en/products/fer ... ?showall=1

If the FR graph is to believed they're flat down to about 50Hz (in fact they've got a slight rise at the bottom, which might be useful?). They're broadly similar to the Definimax units. QTS is a bit lower but Nelson Pass says that's not something to be overly concerned about in a slot loaded scenario.

I guess there's one way to find out but any observations up front will be appreciated.

I should have said they'll be crossing over to the full-range driveat about 80-100Hz.

It's worth noting that the frequency response posted for that driver is when it's used in a 120L ported box, tuned to 56Hz.


That Oberton unit looks like a reasonable high-power 15" PA sub driver. I've used others, and my observation has been that, at high excursions, there's often a lot of wind rushing noise from the motor. They're typically operated at high power (peak inputs >1KW), and all that heat has to go somewhere. Turbulence is probably designed into the air flow.

For OB use, you need plenty of excursion, but thermal power handling doesn't need to be high. Something that's nice and open behind the spider etc will probably be quieter than the PA units.

Chris

From memory the Eminence Beta 15 was supposed to be a good OB bass unit.

That's what Nick used on his original OBs, and I liked the way they sounded.(the way they were set up that is, other implementations may sound different)

chris661 wrote: ↑Sun Dec 26, 2021 10:14 am
For OB use, you need plenty of excursion, but thermal power handling doesn't need to be high. Something that's nice and open behind the spider etc will probably be quieter than the PA units.

Chris

good points one and all, but......is the bass part of slob really OB?....I came to look at it as front loaded....I may be well wide of the mark, but I'm hoping Ray investigates in the true spirit of diy...and reports back the results. It won't alter my approach though cos I'm just using what's on the shelf gathering dust.

chris661 wrote: ↑Sun Dec 26, 2021 10:14 am It's worth noting that the frequency response posted for that driver is when it's used in a 120L ported box, tuned to 56Hz.

Cheers Chris, yes I picked up on that this morning too when I wasn't semi-somnambulant from too much Christmas indulgence.

Thanks for your steer. Here's another possible...

https://www.beyma.com/speakers/Fichas_T ... /15G40.pdf

ed wrote: ↑Sun Dec 26, 2021 11:36 am ...is the bass part of slob really OB?...

I find myelf asking that very same question Ed. Perhaps it's why Nelson says he doesn't think QTS is someting he worries about?

Does it need to be a 15” - a 12” driver with more linear travel will move the same air. I have played with slot loading in the past with the Ripole sub, sacrifice more distortion for bass extension. The slot loaded SLOB arrangement will have some chamber resonance your need to avoid too, usually in the 200-300 hz range, a 4th order x-over crossed low normally avoids any issues. What about this just going for a convention OB? https://www.soundimports.eu/en/sb-acous ... 75-16.html

The Link is from another Forum where Ripole Sub Woofers are under discussion.
The Link has been presented as these Drivers are claimed to be very useful in OB's.
The Calc' Aficionado's can determine if the claim has an accuracy, I will carry on getting excited about the Manila Pulp


https://www.madisoundspeakerstore.com/s ... le-woofer/

So, I have bitten the bullet; this morning I placed an order for a pair of these on the basis that, spec wise, they're a reasonable approximation of the Eminence Definimax 4015LF (now discontinued) units that Nelson used in the orignal;

https://faitalpro.com/en/products/LF_Lo ... =151060150

excuse my ignorance, what is a SLOB?

Paul Barker wrote: ↑Sun Jan 09, 2022 6:49 am excuse my ignorance, what is a SLOB?

Slot-Loaded Open Baffle

Ah, I should have realised. Steve’s been doing that for years without giving it a fancy name.

Ray youre small driver has a huge motor. Is that. Faital too? looks expensive!

Paul Barker wrote: ↑Sun Jan 09, 2022 12:28 pm Ah, I should have realised. Steve’s been doing that for years without giving it a fancy name.

Thats true Paul, what I find interesting is that there's no colouration in that design, when I've tried mine without damping I've not liked what I've heard.

Maybe that design does not have any effect on the sound. I would love to hear those speakers as is, but to date I've not been lucky enough to..

Same with the ripole sub, they look a similar concept, but again I've not knowingly heard them, but do I remember Scott not being very enthusiastic about them after he heard them.

Paul Barker wrote: ↑Sun Jan 09, 2022 12:28 pm Ray youre small driver has a huge motor. Is that. Faital too? looks expensive!

Paul, the pictures aren't of my speakers, they're by Nelson Pass from the 'Burning Amp' event nearly a decade ago.The full-range unit is a field coil Lowther.

http://www.tnt-audio.com/shows/burning_amp2012_e.html

There's an article by Nelson about his slot loaded experimentation here

https://www.firstwatt.com/pdf/art_slob.pdf

My own full-rangers are currently Aurel Bryan FR8DFe



but I would like to experiment with the Lowther that Nick is using in his quasars (and maybe some others too).

Ray, thanks, and it occurred to me after I asked about the full range unit, you might have used an existing picture. Crazy how long the field coil motor and so pole piece requirements to get necessary efficiency. I dream of making my own field coil motor for existing magnet speakers, but stumbled at pole piece, as it is. Cobolt is a stupid price, so it would certainly have to be iron at that length. So might be thats the pattern, longer pole piece to get the efficiency required.

Steve, youve worked away at this for years and its working out from my last trip to youre house. A lot better than the horns.