FE208S + BD-15

Hallo Bert,

Do you have good article (or references) on the design of open baffle systems? You seem to suggest that it is a matter of trial and error. Since I have no measuring equipment this would become a very difficult task with a lot of waisted wood, i am afraid.

But the main question of my previous entry remains unanswered. Does the BD-15 sound different in a Quasar compared to a reference enclosure in terms of how bass instruments sound. What I miss with my Etons, and every other reproducing system I heard up to now, is the life-like sound of bass drums and electric bass guitars. The speed of the attack as well as a lot of overtones appear to be missing. In which cabinet do you think the BD-15 will perform the best regarding these aspects. By the way, I often have the idea the sound engineers deliberately filter out high frequnecies on bass instruments. Can anyone comment on this point?

Reaching 20 Hz is not a goal in itself. The lowest resonance frequency of my listening room is 29 Hz anyway. But I really like the deep sound that my Etons produce on CD's such as "Medulla" by Bjork.

Yours sincerely,
Eddie

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Do you have good article (or references) on the design of open baffle
systems?

Try this:

http://www.prijsindex.net/tmp/room%20acoustics%20and%20eq.html
-Thorsten Loesch

Niels

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Hello Niels,

Thanks for the information. I do not want to go into equalizers and it appears that Thorsten Loesch agrees with Bert on dipoles, I quote from his article:

"Dipoles and Omnipolar Speakers create way more problems than they solve, by radiating energy over a very WIDE frequency range and also a very wide area. Think simply of a naked lightbulb in a room. THis is your omnipolar speaker and to a lesser degree your dipole. this makes the frequency response in room within the reverbrant range maximally dependant on the room symetry, absorbtion etc. and thus will require major efforts on room treatment to correct for the problem. Of course, a notable minority of listeners actually likes the presentation of omni's and full range dipoles and they by all means are welcome to their preference."

I also agree with Thorsten's last remark, we listen to music for our pleasure and this is in many ways a subjective impression. This makes discussions on what is "good" and "bad" very difficult. I like the way in which Bert tries to approach his ideal of music reproduction. Another fascinating part for me is that it is still impossible to measure what makes a system sound really good, like it is impossible to make a copy of a Stradivarius violin that sounds like the original. On this point discussions are also often weird or impossible because a lot of people really do not understand the complexity of musical sound and the qualities that our ears have in analysing these signals. This is one of the things that keeps life interesting to me.

Eddie

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Thanks for the information. I do not want to go into equalizers and it
appears that Thorsten Loesch agrees with Bert on dipoles, I quote from his
article:

"Dipoles and Omnipolar Speakers create way more problems than they solve,
by radiating energy over a very WIDE frequency range and also a very wide
area. Think simply of a naked lightbulb in a room. THis is your omnipolar
speaker and to a lesser degree your dipole. this makes the frequency
response in room within the reverbrant range maximally dependant on the
room symetry, absorbtion etc. and thus will require major efforts on room
treatment to correct for the problem. Of course, a notable minority of
listeners actually likes the presentation of omni's and full range dipoles
and they by all means are welcome to their preference."

I also agree with Thorsten's last remark, we listen to music for our
pleasure and this is in many ways a subjective impression. This makes
discussions on what is "good" and "bad" very difficult. I like the way in
which Bert tries to approach his ideal of music reproduction. Another
fascinating part for me is that it is still impossible to measure what
makes a system sound really good, like it is impossible to make a copy of
a Stradivarius violin that sounds like the original. On this point
discussions are also often weird or impossible because a lot of people
really do not understand the complexity of musical sound and the qualities
that our ears have in analysing these signals. This is one of the things
that keeps life interesting to me.

Thorstens remarks there are on the reverbrant range; reed the article more carefully.

Also see: http://www.diyaudio.com/forums/showthread.php?postid=538997#post538997

+ the rest/start of the thread

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Hallo Bert,

Do you have good article (or references) on the design of open baffle
systems? You seem to suggest that it is a matter of trial and error. Since
I have no measuring equipment this would become a very difficult task with
a lot of waisted wood, i am afraid.

But the main question of my previous entry remains unanswered. Does the
BD-15 sound different in a Quasar compared to a reference enclosure in
terms of how bass instruments sound. What I miss with my Etons, and every
other reproducing system I heard up to now, is the life-like sound of bass
drums and electric bass guitars. The speed of the attack as well as a lot
of overtones appear to be missing. In which cabinet do you think the BD-15
will perform the best regarding these aspects. By the way, I often have the
idea the sound engineers deliberately filter out high frequnecies on bass
instruments. Can anyone comment on this point?

Reaching 20 Hz is not a goal in itself. The lowest resonance frequency of
my listening room is 29 Hz anyway. But I really like the deep sound that
my Etons produce on CD's such as "Medulla" by Bjork.

Yours sincerely,
Eddie

Dear Eddie:

The best reference I've ever found on open baffle speakers is the various web pages of Seigfried Linkwitz. The URL of his home website is:

http://www.linkwitzlab.com/index.html

Especially read the pages on theory and driver selection.

Don Reid

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Hi Eddie,

In my opinion the best performance related to your description is to use them in a well designed BR where the driver has to work less hard.

Not all will agree with me though and will say that the open panel is better...

Ciao,

Bert

--
BD-Design - Only the Best!

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Hi Bert, Eddie.

Are we talking about the Fostex 208 SIgma ? I've tried this same driver in a QW, and in a BR (about 1.5-1.8 cu.ft, I think), and they don't sound very well IMHO. The best, again IMHO, for these drivers is a rearload horn

Brady

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Are we talking about the Fostex 208 SIgma ? I've tried this same driver
in a QW, and in a BR (about 1.5-1.8 cu.ft, I think), and they don't
sound very well IMHO. The best, again IMHO, for these drivers is a
rearload horn

Hi Brady,

No we're talking about the enclosure for the BD15. The FE208 Sigma will then be used for the mid and high frequencies in another enclosure (closed, reflex or open panel). Used as full-range driver without additional bass system you're absolutely right...!

Ciao,

Bert

--
BD-Design - Only the Best!

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Hello Brady,

Bert is correct, but you do have a good point here. The rather poor match that I have between bass and midrange is more probably due to the weak bass response of the FE208Sigma in a closed box (of 30 ltr) than to the impuls quality of the Eton woofer.

Last weekend I found an additional explanation for the mismatch. I accidently saw the phase response of the Eton woofer. To my surpise its acoustical ouput was -140 degrees from 30 Hz up to 1 kHz, this means that it is almost out of phase! Unfortunately I do not have data of the phase of the Fostex.

That evening I reversed the polarity of both woofers and found that the matching was somewhat improved. The fact that the difference is not large indicates to me that in both polarities the two units are not really in phase whichs results in a dip in the frequency respons. Bert suggested this test to me a long time ago when I had Peerless XLS-10 woofers. At that time the overall sound was clearly better with the woofers in phase, so I never thought of the test again until now.

I am now thinking of a radical solution. If it succesfull I will probably report on it (this summer?).

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