Nelson Pass: The Slot Loaded Open Baffle Project

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#541
CLS said:
I've tried a similar one, with 2 problems:

1. the deep slot forms a strong 1/4 W.L. resonance, deep notch filter is needed if you play it up to midbass.

2. the cone (and air load) moving up and down, causing strong vibration to the whole base, efforts on isolating that from floor and other part of the speaker would be needed.

I dropped that eventually.
Click to expand...

I think the reason to go for a 15 inch driver rather than an 18 inch one is specifically to minimize the 1/4 WL resonance's effect on overall response, since the 1/4 WL resonance is dictated by the depth of the cavity which in turn depends on the driver's diameter.
In the case of a 15 vs 18 inch driver this would give a resonant freq of 215 hz vs 172 hz (when total slot depth is taken at 40 cm for the 15 inch and 50 cm for the 18 inch driver)
This 38 hz difference plays a big role when trying to match woofer to FR driver, especially at the 180hz crossover frequency chosen by NP.

Hope I'm making sense

Nick
 
#542
markus76 said:
Qts should be about 0.5. With the right parameter set one probably can get away with a simple low pass filter. Let's wait and see how the SLS-12 Ripole turns out.
Click to expand...

Here's the frequency response at the front chamber (24dB lowpass @ 150Hz, no EQ):

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That's what the Ripole looks like:

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#544
Sometime ago there was a patent for an old speaker shown in one of the forums. I did download it at the time but it is in an older computer which I don't have access to. Part of the design was a circular disc, about the same are as the speaker spaced out from the cone and leaving a gap all round. If this was done on an OB and spaced out so that the area between the disc and the baffle was 30 - 40% of the cone area, would this work? If it would it would have the advantage that the disc could be made out of a nice hardwood and turned like
a shallow bowl shape on the outside and nicely stained good looks and good sound maybe. I realise that it would not have to be turned for bass frequencies to flow round it but it could look good!!!

l
)
l The bowl would be flat where it faces the speaker. Speaker on left of baffle. Bowl shape would really be same size as speaker opening and the gap would be annular.
jamikl
 
#545
InDiBA 16.2 a different Slot Loaded OB Project

pengesluk said:
Work in progress...
Click to expand...

Nearly at the same time I presented my version of SLOB with high WAF in a small cabinet.
I'm totally astonished to see this thread working with same principle, collecting chassis area by arrays of chassis in a slot.

I think we are invented to combine all our KnowHow to go ahaed.

Some more words.
My InDiBA 16.2 started as a low cost event but went to a concept of scalable SLOB.
What's new ?
InDiBA is a synonym for Integrated.Dipol.Bass.Array and it means something similar to a W-Frame but with an array of chassis in a special arrangement.

First I want to have a small box/baffle, so I need to compress the chassis as close as possible and I did.



16 x 5" Sub plus COAx-Tangband >> 18,5 x 94 x 34 cm³

Later on I did some homework in Germany: Sorry, search for:
DE202012008642U1

It's only to be shure no one will earn money with my ideas.

wr
Wolfgang
 
#548
I wish I had room for an OB, but I just can't have my speaks a meter into the room, while I was still fantasizing about it I found this site that has surplus Infinity, Cerwin Vega and Sony speakers all with high Qts. from 6"-10". The 6" CV are 6.00$, the 10" 150 watt Infinity 12.50$.... Ohhhhh, maybe I'll build them on casters and roll 'em out just when I'm listening, I just LOVE this design!
 
#550
I finally finished one of the bass unit for my Lowther horns(PM7A). I'm using the horn full range to about 150-160hz, and using mindsp for Xover and EQ for the bass unit. I'm not sure if the JBL 2226J is a good match for the design with a Qts of .31 and Fs of 40hz. But I have 4 lying around , and they are efficient with good power handling capabilities. So far with preliminary test and listening with only one unit ... They sound very natural and is usable to about 35hz and matches my horns well. I need to build the second one and start tweaking
 

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#552
It was suggested to me to use 1/6 to 1/8 of woofers SD, I'm currently using the slot opening area of 1/3 of SD of the woofers. What are the pro and cons of using a smaller opening ?
I'm guessing:
Pros: Higher pressure at opening
Cons: Possible damage of drivers due to higher pressures ?

Drivers are JBL 2226J with MiniDsp as Bass Xover.
 
#553
CLS said:
Hi, long time no see. Here are my recent works for bass units of the 3-channel system.

All 3 are slot-loaded, with 18" woofers. The central one has 2 drivers and arranged as push-pull. It's actually more like a pair of face-to-face shallow U-frames. That's for adapting the very-close-to-the-rear-wall positioning (for practical reason, no other option for the central sub). The rear lobe of the dipole is, I guess, more or less splited in 2 and becoming side-firing.

DSCF4558.jpg


DSCF4560.jpg


On the left side, the smaller baffle is more like an ordinary OB (shallow U-frame), just with a slot shape baffle hole and rear mounted driver.
DSCF4556s.jpg

(the taller one is fiddled mid array, the lower 'slot' type hole on it is not for loading but dispersion and, simply maintaining the strength of the slim baffle)


On the right, it was originally used at center which I posted here. This unit was later modded to have a cardoid response, well, sort of. (The trick is simply a cardboard with some punched holes at the back. ) So, why difference between the left and right? The space itself is asymmetry, I need more bass energy at the emptier right side. More output of the cardiod could be good.


Overall view with the whole system:
DSCF4555s.jpg



These 3 bass units are wired as Linear Matrix. The new build is partially for the matrix which tends to be center-heavy. So I need more output at the center for such character...
Click to expand...

Hello CLS and all those interested in this set of speakers.

can anyone articulate the effects the "lower 'slot' type hole" on the smaller sub (or bottom driver of the OB mains) to the left most of the picture has on the bass delivery?

Love the looks but wonder what impact it has on the wave form?!? CLS states its for dispersion but does not explain what exact effect it has.

many thanks,
Rich
 
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#554
rmeinke said:
Hello CLS and all those interested in this set of speakers.

can anyone articulate the effects the "lower 'slot' type hole" on the smaller sub (or bottom driver of the OB mains) to the left most of the picture has on the bass delivery?
Click to expand...

(the taller one is fiddled mid array, the lower 'slot' type hole on it is not for loading but dispersion and, simply maintaining the strength of the slim baffle)

Rich,

I think the looks and the baffle strength is the main objective...

The look superb... If I had a warehouse flat I'd be looking at something similar.

John
 
#555
Hello John,
You and I both. LOVE the look of these speakers. I have a small room as well and will never have a system this size. I have a pair of Acoustic Elegance Dipole15's on the way and would like to build the smaller subwoofer with the slot.

I too read the same comment explaining why he specifically chose to implement the slot on the mid array but I'm more interested in the actual effects the slot on the bass frequencies... especially on a subwoofer.

I'm tempted to build it with the slot being removable... in case it doesn't sound good. It could act like a grill when not in use.

Regards,
Rich
 
#556
Earlier on it was mentioned that the set up at burning amp used a Eminence Definimax with a total Q of 0,5. I would like to know if this is a critical parameter?
I can locally pick up several used 15 inch woofers but they al have lower total Q. 😕


I want to use these in a slotloaded bafle to help out BL horns containing 8" fostex fullrange. In the futere Im foreseeing many other experiments where they will have a similar task.
 
#557
A slightly higher Qts is usually sought after when ussing a passive crossover as it takes advantage of the driver's Fs to boost the frequencies around Fs.
If you're using a good active crossover or a DSP, I personally think that a lower Qts driver is actually preferred as it gives better defined bass...

Edit: pairing BLH and OB is tricky; phase issues arise...
 
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#558
Fostex horns are my first full range experience and this to me seems realy the way to go.
Wanted only the fostex units to experiment with FR, and do the whole openbaffle thing but with them came some very nice build horns Which I want to use for the time being.

Concerning phase issues:

My idea was to take some woofers in a slot loaded baffle and hook them up with an active cx3400 crossover from Behringer which Ii have laying around (but never used) . This crossover has a 20 ms adjustable phase correction.

I have nothing ( no notchfilter) in between the fostex loudspeaker and the amp and want to leave it that way.

So any comments or advise on how to do this is welcome
 
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