[el`Ol]

Hello all!

I saw this FR graph of the Hawthorne Augie in a Visaton Nobox baffle:
http://www.enjoythemusic.com/magazine/equipment/0107/diy_loudspeaker_project.htm
I wonder if the peak at the bottom is due to the wings. Does anybody have measurements on a plain narrow baffle? Till now I think it is not possible to design a driver, whose rise due to high Q gives an even response corrected by the baffle loss, but I am prepared to learn.

Oliver

[tubamark]

Hello all!

I saw this FR graph of the Hawthorne Augie in a Visaton Nobox baffle:
http://www.enjoythemusic.com/magazine/equipment/0107/diy_loudspeaker_project.htm
I wonder if the peak at the bottom is due to the wings. Does anybody have measurements on a plain narrow baffle? Till now I think it is not possible to design a driver, whose rise due to high Q gives an even response corrected by the baffle loss, but I am prepared to learn.

Oliver

Reading is nearfield - baffle not in play.  Curious to note that the rise is nearly 6db/octave
The rise is due to mass-plug cone loading, and is intentional, as Dipole response rolls-off @ 6 db/octave (until driver resonance reached -drops like a rock below Fs).
Once dipole effect in play (meter or so away) the result is near-flat response, depending on exactly what effective baffle size is used.

One could likely get similar effect by taking a low-Q, medium Fs, jumbo-magnet (high-Xmax, yadda, yadda) woofer and simply adding mass until similar behavior is achieved.  (Somebody correct me if I'm off here).

--Tubamark.

[el`Ol]

Would the following also work: Take a sub with Mms 300g or more (e.g. JBL) and add a series resistor?

[tubamark]

Would the following also work: Take a sub with Mms 300g or more (e.g. JBL) and add a series resistor?

Every driver recipe is different, but I doubt it.  You would need an obnoxiously high Qts (far more than the Augie's .92) in order to get a 6 db rise, and the rise would probably be too quick and narrow = boom.

Technically the mass on the Augie creates an acoustic lowpass filter - a rolloff above resonance, at the expense of some efficiency.  At some point of adding mass, the Q and efficiency would suddenly become unacceptable.  For the Augie, that point of diminishing returns must have been somewhere just below the 27 Hz they wound up with.

The Carver Amazings, otoh, went the high-Q route.  The bass on those was to be too soggy-muddy-boomy for many (most?) audiophiles.

If one has said JBL or similar lying around, it would be harmless to try for kicks.

-- Mark

[D OB G]

Am I right in thinking that the lowest graph in Dick Olsher's article, showing a hump at 40 Hz, is not a near-field measurement?

David

[tubamark]

Am I right in thinking that the lowest graph in Dick Olsher's article, showing a hump at 40 Hz, is not a near-field measurement?

David

Olsher: ". . . the measured frequency response, which is shown below. These are in-room measurements (with the EAR 834T amplifier) at 1 meter for both the right and left channels."

-- I'd call that pretty close for a large dipole, yet under conditions that will include other real-world effects.  The 40 Hz bump is likely from some variable(s) like summed channels, combing/lobing, or room effects.  The bump was absent in the Augie-only graph which was definitely nearflield.

Anyway you look at it, it's fantastic response for a dipole woofer with no EQ assistance!

-- Mark

[Vapor Audio]

Anyway you look at it, it's fantastic response for a dipole woofer with no EQ assistance!

I'm just looking at 200hz up, since it's an in-room measurement ... and still the FR looks like a roller-coaster to me.  A nearly 10db variance isn't exactly smooth.

[opnly bafld]

Anyway you look at it, it's fantastic response for a dipole woofer with no EQ assistance!

I'm just looking at 200hz up, since it's an in-room measurement ... and still the FR looks like a roller-coaster to me.  A nearly 10db variance isn't exactly smooth.

Hawthorne Audio designed it as a bass augmenter to be used below 200hz with fullrange OB speakers.
I used two with a pair of Visaton B200s on a 20"w flat baffle with decent results and I have heard them on a small baffle (maybe 18" x 18" flat) paired with Hawthorne's own SI 15" coax OB drivers .

Lin

[stereogeek]

Here is a copy of the Augie FR graph straight from Eminence.It is probably aneohic chamber responce and not open baffle.

http://www.hawthorneaudio.com/photos/albums/userpics/10003/Scan_Augie_15.jpg

Steve

[el`Ol]

A similar hole can be seen in the FR graph of the Hempacousics OB bass. How that?
http://www.hempacoustics.com/SW15OB_-_Hemp_Spec_Sheet_ready.pdf

[stereogeek]

Like I said about the Augie,it's aneohic and not OB.Could it be that the back wave fills in the "holes" and the responce averages better on OB?????

Steve

[D OB G]

Could it be that there is not just a hole in the response, but also an underdamped Qts of 0.92 induced hump?

Yes the hump equalises the baffle cutoff from say 30 Hz or so to 70 Hz or so, but above that wouldn't we expect a falling response from the baffle cutoff, as shown in both graphs, and in keeping with IEC type measurements which, if I am not mistaken, are taken on an open baffle, at one meter?

This suggests to me that for the flattest response the baffle needs to have a turnover frequency of 80-90 Hz.  Larger I think than conventionally used, to equalise the baffle loss between 70 Hz or so and 140 Hz or so as demonstrated on the graphs?

In any case, it would be good to see someone with a flat Augie response graph to clarify the matter.

David