Melon Head's State of the "DUMB" Open Baffle Design

Status
Not open for further replies.
Jump to Latest
#281
Hi Melon Head,

Yeah, the idea is to perhaps rebuild OB's since I've made Mishmash with them trying different things. Then I could perhaps try a set of narrow wings (with piano hinges). Maybe transparent wings made of plexiglass? Just an idea..

On the other hand, since you have already tried various Open Baffle combinations, I would beg you to try one more, if you have the time and willingness (and because I can't 🙁 ).
So, try to build a baffle like Nelson Pass Slot Loaded Open Baffle, albeit smaller (say 60 cm wide 120-130 cm high). Use two AN15's in a slot loaded configuration, and AN10's on top of a baffle. I'be very curious to find out how this sounds...
 
#283
push pull slot loaded ?
yes it helps above 100hz but............

The width of the plenum determine how high it will catch the harmonic distortion.

"In order to work you must be within 1/4W of the second harmonic of the highest frequency to intent the box to work at."

Norman
 
#285
Vix said:
:worship: 😎 🙂

Hint: Try using different crossover points. You can get surprising results. For example: On a SLOB, try this: Low pass 80-100Hz 2nd order (+bass boost), Hi-pass 150-200 Hz 2nd order (+EQ network if needed). All features doable with B4 crossover 🙂
Click to expand...

I will try all of those options and measure it.
If the slot doesn't sound nice above 100Hz then I could low pass at 100Hz and just eq the response of the AN10 to get a flat response. It won't need too much EQ so I think it will work

So you want a flat baffle 60cm wide with no wings correct?
 
Last edited:
#286
I'm thinking the 100hz xover plus boosting low end of an10 would work better.

Using my active crossover, 24db LR sounded bad crossing at 200hz to a full range driver. I couldn't cross much lower due to a hole in the response (no eq and zero baffle step). I have better luck running my little 2 way wide open alongside a sub than crossing in the woofs at 200hz.

But try it all, your ears may disagree, and that's fine too.

Norman
 
#289
buzzforb said:
I have found that listening to and working with FR drivers makes one sensitive to phase issues.
Click to expand...

so, so true.

But they have phase issues also (and don't get me started on the whizzer). Check this out.

DECWARE - Audio Paper - Understanding high efficiency full range drivers

"Phase Response

You might find it interesting to know that because of the resistance and capacitance and inductance created by moving the voice coil inside the magnetic gap (also known as Impedance) there is a phase shift that manifests itself across the frequency response of the driver. For example, if you started at 100 Hz and moved up the scale you would find that absolute phase does not exist. By the time you reached 5 or 6 octaves the output of the driver can be delayed in time by as much as 180 degrees or more. Boy that sucks, you think to yourself, and yea it sorta does. The trick is to make it work for you rather then against you but that’s another paper. You wonder why it wouldn’t be possible to make a driver that maintained at least a nearly flat phase angle across its bandwidth, and actually some companies do. The problem is this – on a linear phase angle as you go up in frequency the efficiency follows. That means that a driver designed with linear phase response would get louder and louder as it travels into the midrange and treble frequencies. This of course wouldn’t sound too good, and it certainly doesn’t look attractive on paper so manufactures design a phase shift into the drivers to prevent the efficiency from rising too much at higher frequencies, or put another way - the keep the frequency response relatively flat.

In a perfect world, such a linear-phase driver would be used in a full size straight horn where the horn itself would exponentially raise the efficiency as the music goes down in frequency. This can nicely offset the response of the driver and end with a result that has both flat frequency response and a minimal phase shift. When you start downsizing and or folding (usually both) the perfect horn you open a can of worms that will include phasing problems. I think I’ve just outlined a substantial reason for why Lowther drivers in particular sound the way they do."

and here

Forums - Understanding Phase Degree Angles Relative to Sine

or check out here where 6moons liked a 6db crossed speaker than fostex 126e in the horns.

Time Aligned design better than fostex 126e ?????? (Page 1) / FullRangeDriver Forum / Fullrangedriver Forum

anyway, back on topic, just remember that full range drivers aren't perfect phase either. I wish I didn't know that.

Norman
 
#290
While I was on the toilet I had a few more ideas. :rofl:
In Australia they sell wood sheets with dimensions of 8 feet x 4 feet. I would like to see what is possible with smaller style PHY baffles and see the feasability of trying to make a pair of OBs from a single piece of nice thick bamboo ply
Just need to get cardboard to start experimenting
 
Last edited:
#293
SO, I got a dumb thought. THinking about the PHY baffle asnd what it does, I remembered a question I had for Dave @ Planet 10, about his dMarKen enclosure for my FR driver. I was trying to figure a XO point and was going to start with the natural baffle step point. TO do this i needed to figure baffle step on his box, but was unsure whether to use the actual baffle width, or the total cabinet width(corners are chamfered/45'ed). He said i had to use the total width. SO with his design, you get both a greater baffle width due to box shape, as well as improved baffle diffraction due to baffle shape. THe only shape that does better than a chanfered cube is a circle. Well, if you think of the PHY in these terms, then what you have is a baffle that is in reality much larger than the main baffle that the driver is mounted to, due to the additional width added by the wings. It would be interesting to measure the total width with wings and make a flat baffle thta matches that width and see what you get. Now truthfully, I expect a difference, but not because of the baffle width, but because the PHY also gives you some bass loading where as the OB will give you actual cancellation in the lower registers. SO it seems to me thta the PHy is nothing but a variation on a BIB like speaker with much wider baffle.
Shoot away.
 
#294
Melon Head said:
give me a bit of time
Click to expand...

As much as you want/need. 🙂

I was scratching my head about this since I read Nelson's SLOB article, but couldn't afford multiple woofers just for a test. But since I tried slot loading, I saw that "There's something our there", and this approach seemed preferred to my ears. Bigger is better, but, due to space constraints and a few WAF orders, I have set a baffle size of 120x50cm to be the maximum allowable. I can try all other tricks to get the bass (sound) I want, but the baffle must not get bigger than that. Slot loading was a nice "trick". But as one always want more, I was imagining a narrow and tall baffle (say 50x140 cm-stretching it a bit) and using four (2 on each side) 15" woofers in a slot loaded configuration and a FR of choice on top. Now that would be nice...:drink:😎
 
#296
Since this is an active thread and slot loading has come up multiple times, I have a few questions for those who have experimented with the concept.

1) By "loading" the driver are you also protecting it from possible over excursion by changing the compliance or springiness of the driver? Is this another possible advantage?

2) Some seem to suggest that by increasing velocity from the front of the driver, you now have less cancellation occurring as the front wave is no longer such a close reciprocal of the rear. But isn't the speed of sound a constant, regardless of the speed in which a driver pushes air?

I'm still trying to wrap my head around this concept so thanks for any comments.
 
Status
Not open for further replies.
Top Bottom