diyAudio Full Range Reference Project

[planet10]

estimate -6dB @ 50Hz and -3dB @ 70 Hz.

70 Hz was about what i was gonna guess before i saw your chart -- not bad for a 5" ... try lengthening the port a bit.

dave

 

[planet10]

Have you compared a bipole version( 2 opposite drivers in phase) vs dipole(2 opposite drivers out of phase). Friends and I just put together a 2 pairs of Coral Flat 8 in a BR box and the result was most interesting. The bipole had good bass and midrange was a wee bit cloudy and slight boxiness. In the dipole, wow huge soundstage but centre fill wasn't that good. Maybe because of the almost isobarik type loading the clarity and highs also improved quite a bit. We then tried reducing the high frequency from the rear driver, the centre fill did improve quite a bit and btw the dipole version had less bass.Still experimenting but dipole with subwoofer seems like a good solution.

You are confusing me here... 2 drivers wired out of phase in the same box?

Are the magnets of the 2 drivers mechanically connected?

dave

 

[Variac]

So a folded trans line would allow the driver to be at the top?
Seems a lot more practical.

Whoops, maybe that's my wants being expressed. I was thinking that the best form factor is small towers about 40" tall with the driver up near the top centered at about 36", deep , but narrow.

Ids this what otheres want?

 

[planet10]

"Elegantly folded"? I like the sound of that. What sort of bass are we expecting? I'm imagining a rather deep, narrow box that's only about 18-24" tall sitting on it's own matching sub for a stand. Go ahead, tell me the sub won't be necessary.

The narrow deep box isn't the perfect fold, but i'm still noodling it. Folding it for wide & shallow is a bit more elegant fold wise -- it ends up being wider & shallower (which with the monopole could push the baffle step low enuff that reasonable proximity to real wall would deal with baffle step.

dave

 

[Variac]

Well, 2 somewhat wide and shallow boxes placed back to back for the bi-pole would make a square section tower. They could be built as one box or they could be literally 2 separate boxes that could be screwed together back to back. As you mention, if you just use the front box with one driver, then you have something you MIGHT be able to put close to the wall

So I guess I'm thinking that we could make one box design with one driver that could be doubled and placed back to back for a dipole, or use just one box per channel for use with a BSC filter or against the wall.

I still prefer a narrower form factor if possible, but I see the advantages of wide....

Personally, as I already mentioned, I prefer towers to boxes, but the idea of placing them on a sub to form a tower is an interesting option.

 

[Timn8ter]

I recommend tuning the cab at 50Hz+. Going any lower may cause loss of cone control. It can be surprising how much satisfaction is gained with quality of bass vs. quantity.

 

[Timn8ter]

Assuming that Zport = 28.5 in and a density of 0.3 lb/ft^3, I get the attached response.

I would estimate -6dB @ 50Hz and -3dB @ 70 Hz.

Is it possible to get a little more out of the low end?

Gio.

It appears that you've modeled the drivers wired in parallel. Are you sure you want to do that?

 

[planet10]

Assuming that Zport = 28.5

Set Zport to 30" -- a port out the bottom would work too.

dave

 

[planet10]

It appears that you've modeled the drivers wired in parallel.

I'd be wiring mine in series...

dave

 

[planet10]

I'm imagining a rather deep, narrow box that's only about 18-24" tall sitting on it's own matching sub for a stand. Go ahead, tell me the sub won't be necessary.

1st draft of the narrow folded box... (using guess & by golly method)

Sub not necessary to enjoy the music... only if you want to shake the room.

dave

 

[gmilitano]

It appears that you've modeled the drivers wired in parallel. Are you sure you want to do that?

I'd be wiring mine in series...
dave

I guess that depends. I was hoping for a tube friendly design. In series, the efficiency would only be about 90. However, the less than 4 ohm load may be problematic.

Gio.

 

[BTW]

You are confusing me here... 2 drivers wired out of phase in the same box?

Are the magnets of the 2 drivers mechanically connected?

dave

Hi Dave,

Sorry for not being so clear, the magnets of the 2 drivers are connnected together just like the bipole speaker in your drawing. We had 2 seperate terminals for we could try different ie bipole, dipole, series, parallel connections.

 

[planet10]

I was hoping for a tube friendly design. In series, the efficiency would only be about 90. However, the less than 4 ohm load may be problematic.

Wired in series is particularily tube friendly. Wiring in series doesn't effect the efficiency. If you have a solid state amp, you'll; have a happier amp with 3 dB less power, less distortion & more balls. With a tube amp you won't lose much power (none if you have higher Z taps), and less distortion.

Besides series seems to sound better.

dave

 

[planet10]

the magnets of the 2 drivers are connnected together just like the bipole speaker in your drawing. We had 2 seperate terminals for we could try different ie bipole, dipole, series, parallel connections.

OK.

Loading into the box you would have no output at all at levelengths smaller than about 2 x the average cabinet dimension. I think you'd be way better off just mounting the 2 drivers in an actual open baffle.

Separate connectors is what i put on them -- but mostly to play with series/parallel.

dave

 

[BTW]

OK.

Loading into the box you would have no output at all at levelengths smaller than about 2 x the average cabinet dimension. I think you'd be way better off just mounting the 2 drivers in an actual open baffle.

Separate connectors is what i put on them -- but mostly to play with series/parallel.

dave

Thanks Dave, think I'll get out my OB baffles and do some comparisons.

 

[gmilitano]

Well, I need to get into the fun. Here is what I have come up with. It is a little larger than the v0.1.

I'd appreciate it if someone could look over my model to see if there are any errors.

I chose the internal dimensions 6.5" X 10" so that the enclosure could be built with standard 1"X8" and 1"X10" boards which should have a nominal 3/4" thickness.

I'll have to check, but I think a 3" OD pipe has an internal radius of 1.414".

Regards,
Gio.

 

[Variac]

a nominal 1x8 would be .75"x 7.5" I believe.
A nominal 1x10 would be .75"x9.25"
1x12 = .75"x11.25"
Maybe finish material is different but I don't think so
Shelf boards might be different also

 

[Timn8ter]

Gio
BL is not doubled when wiring in parallel. Also, because of the larger size of the cabinet LF begins rolling off prematurely.Modeling two drivers in Martin King's MathCAD worksheets

 

[planet10]

Tim,

If you were to put a rebate into the baffle to flush mount the front of the 127, out deep would it be?

dave

 

[planet10]

Here is a 1st draft of a bi-pole folded version... for a monopole the cabinet is sliced at the red line. I've drawn it round topped but it could be square with reflectors.

dave