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Old 7th June 2014, 08:21 AM   #1
tilroh is offline tilroh  Australia
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Default 1st box design - fail

A friend bought a couple of Celestion 5" from the bay of E. link

I had a go with WinISD and we build 16 liter boxes with 38 x 38mm vents. The result was not good... very tinny, no bass. They're powered by a Sure 50w/ch D amp. Input by various laptops using iTunes/FooBar, mp3s/FLACs

Can anybody offer a suggestion as to other enclosures might be less worse?

I'd love to build a pair of Karlsons

Below are somebody's actual test results of the drivers.

fs=131Hz
Re=6.45 Ohm
Le=0.68 mH@1kHz
BL=4.72 NA
Vas=2.86 L
Qe=1.024
Qm=2.05
Qt=0.68
SPL=89.9dB/W/m

Any advise or observations greatly appreciated and from now on I'm sticking to designs done by people who have a clue 'caus I don't seem to.

Cheers, Mack
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Old 7th June 2014, 09:22 AM   #2
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Did you try BSC?
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Old 7th June 2014, 09:35 AM   #3
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Yes, look at BSC.

Also, have you compared the impedance curves of the simulated box with what you actually measure? Tuning too low can often cause a perceived lack of bass.

Quite frequently I find that simulated port length is far too long, and to get the appropriate tuning you'll need to shorten it, (sometimes by up to a third). The easiest way of checking this is by impedance sweep, as you can see where the peaks are.

edit: We all learn by making mistakes and sorting them out, so this is much better for you than just getting it right first time.
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Old 7th June 2014, 09:50 AM   #4
Zero D is offline Zero D  United Kingdom
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Hi, those test results of the drivers are different from the ones in the link you gave, which i presume they got from here Celestion Neodymium 5" Full-Range Woofer 8 Ohm They missed off the following important info !

Quote:
Flat frequency response from 200 Hz to 6,000 Hz - for professional audio applications as a midrange - Note: For even greater maximum power handling, a 150 F capacitor for a 1st order crossover point of roughly 125 Hz is recommended.
For guidance, these would have been better http://celestion.com/product/76/ntr061705d

******

To the other posters. Do you think he knows what BSC means, without explaining ?
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Old 7th June 2014, 09:53 AM   #5
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Quote:
Originally Posted by Zero D View Post
...To the other posters. Do you think he knows what BSC means, without explaining ?
Good point.

Baffle Step Correction
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Old 7th June 2014, 02:12 PM   #6
tilroh is offline tilroh  Australia
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Quote:
Originally Posted by pinkmouse View Post
Thank you, I've built BSC devices per speaker plans but thought they were for peaks caused by the speaker, not the enclosure's front. Several more things now make sense.

Looks like I've got the wrong driver to user for full range.

Thanks, Mack
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Old 7th June 2014, 02:20 PM   #7
tilroh is offline tilroh  Australia
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Quote:
Originally Posted by Zero D View Post
......For guidance, these would have been better http://celestion.com/product/76/ntr061705d
Indeed, 70-7000hz would have been preferable to 200hz to 6000hz.
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Old 7th June 2014, 04:15 PM   #8
Bare is offline Bare  Canada
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Perhaps you might try powering your speakers with a 'different' amplifier ..Before deciding their fate ?
I found that my Cheap Chinese 'Fake tripath chip' amps (all 3 of them) was the reason my speakers sounded rubbish. Easy enough experiment.
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Old 7th June 2014, 04:30 PM   #9
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No bass from anything with an fs that high. The efficiency might become horrible, but maybe you could add some mass to them to drag the fs down?
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Old 7th June 2014, 04:35 PM   #10
GM is offline GM  United States
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Some more useful BSC info here: General Speaker Related Articles

Hmm, with no construction dims, I simmed a golden ratio T/S max flat 0.565 ft^3 [16 L] alignment using a round vent area = 38 mm^2 x 18 mm long vent, assuming a 0.5 ohm wiring resistance for an effective 0.717 Qts. Note that I calculated driver [Sd] = 76.41 cm^2.

With a ~60 Hz Fb, its little wonder theres no [mid] bass [1st sim], though tuning it up to the calculated T/S max flat ~80 Hz Fb with a 2.5 i.d. diameter x 1.25 long vent [2nd sim] its flat enough that it might not need any BSC in a near-field app and certainly a lot less if in the far-field.

Like you say though, its no FR driver unless you only listen to AM radio, pre early 50s source material.

GM
Attached Images
File Type: gif Celestion PE B_O 5' neo 'FR' BR [tilroh].gif (6.7 KB, 150 views)
File Type: gif Celestion PE B_O 5' neo 'FR' max flat BR.gif (6.7 KB, 151 views)
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Last edited by GM; 7th June 2014 at 04:40 PM.
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