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Old 20th December 2007, 12:58 AM   #1
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Default Open-Baffle and Equalizer - why not :)

Bass loudness (not quality!) is a well known problem with OB implementation and to remediate this, large-ish woofers are required. But this morning I played around with foobar's equalizer and boost the lower frequecies to anything above +12db .... and it sounds good !

Click the image to open in full size.

I know there will be distortions due to signal change but honestly they were not audible. The OB + equalizer still sounded better than flat source + boxed speakers.

I wonder if it is reasonable to implement a 'bass correction' circuit such as low frequency parametric equalizer to compensate the bass.
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Old 20th December 2007, 01:21 AM   #2
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Every OB design needs ( or not !) it's own equaliser for the bass , be it a passive crossover or an active one.
It's not too hard ( though it might involve work and time ) to design a crossover for the system.
The bass driver performance also matters a lot . Drivers with very high Q like the Eminence Alpha 15A's can work well without any bass lift. Balancing the upper frequency driver to the bass unit can be tricky . Lot's of info on this forum. Suggest you search for OB speakers on this forum. Too much to explain in a single post.
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Old 20th December 2007, 01:41 AM   #3
ttan98 is offline ttan98  Australia
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my experience is that if your woofer has Qts<0.7 the bass will roll off very quickly,

you need,

1. equalizer, active or passive.

or

2. woofer house in U-frame cabinet

or

3. woofer house in H-frame cabinet

mine is housed in U frame the freq response improves dramatically, flat to 50 Hz. beware of resonance it generates. I use an elecronic x-over hence equalization is easy for me. I don't need it for mine.

if you want to build one then search the net lots of example around.
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Old 20th December 2007, 06:04 AM   #4
Pano is offline Pano  United States
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Default Re: Open-Baffle and Equalizer - why not :)

Quote:
Originally posted by gainphile
But this morning I played around with foobar's equalizer and boost the lower frequecies
Yeah, I did the same thing to get a feel for what an active EQ might sound like. It worked very well and sounded nice. Just be sure you don't overdrive Foobar or the sound card. All that boost can lead to clipping. The EQ has an Autolevel feature that helps average things out a bit. Mostly it just lowers everything.

It's a fast and easy way to get an idea of the boost you need.
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Old 20th December 2007, 06:07 AM   #5
owdi is offline owdi  United States
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FYI, foobars built in equalizer may not behave like you think it does.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

IMO, unusable.

Dan
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Old 20th December 2007, 08:21 AM   #6
Pano is offline Pano  United States
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That's a pretty sharp EQ! Looks like real WYSIWYG EQ.

Thanks for the info.

If you get a chance, please try a gentle slope up to about +16 at 55Hz starting at 156Hz. That is what I was using.

Are you looping back into the sound card, or using some sort of internal routing?
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Old 20th December 2007, 08:22 AM   #7
DAMIC is offline DAMIC  Seychelles
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Quote:
Originally posted by ttan98
.....

you need,

1. equalizer, active or passive.

or

2. woofer house in U-frame cabinet

or

3. woofer house in H-frame cabinet

.........
Hi,

Can anybody advise, wheteher U-frame or H-frame design is better for bass reproduction. Actually, I am in process to go for OB design with Eminence 12 inch and Gradient ribbon tweeter, from current bass reflex and want to have deeper response as much as possible.

Thanks
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Old 20th December 2007, 10:15 AM   #8
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OBs, U-frames, H frames, W frames, N frames, etc are all different forms of gradient woofers and all need eq. In addition, all but true flat baffles will usually introduce some type of resonance that may need to be damped. Here is a ling to my page on eq'ing gradiesnt woofers:

http://www.musicanddesign.com/Gradient_woofer_eq.html


and here is a discussion of u- and h- frames:

http://www.musicanddesign.com/u_frame.html

and the NaO II u-frame design:

http://www.musicanddesign.com/u_frame.html
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Old 20th December 2007, 10:29 AM   #9
DAMIC is offline DAMIC  Seychelles
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Thank's a lot
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Old 20th December 2007, 10:55 AM   #10
Rudolf is offline Rudolf  Germany
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Quote:
Originally posted by DAMIC
Can anybody advise, whether U-frame or H-frame design is better for bass reproduction. Actually, I am in process to go for OB design ... and want to have deeper response as much as possible.
If your equalising is done there is still the room to consider. How free are you in choosing your OB-to-front-wall distance? Have a look at two sims:

Click the image to open in full size.

Red is the response of a driver on OB (working in principle like a H frame) without any front wall. Green is the same, but with a front wall at 90 cm distance. You "win" some efficiency between 40 and 130 Hz, but you loose below 40 Hz and will have to cross over at 100-150 Hz.

By varying the front wall distance you can "tailor" this response a bit:

Click the image to open in full size.

Green line is the same as above, red line shows a front wall distance of 120 cm.

Since a U frame´s back wave is less pronounced it will have less influence on the end result.

PS: The simulations have been done with a now out-of-date version of MJKs worksheets. The trend will nevertheless still be valid.
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