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Old 20th July 2015, 01:06 AM   #1
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Location: Raleigh
Default Help w/vented box?

I have a pair of Eton 11-581, can you help me choose a vented box?

Znom 8 ohm
Re 5.2 ohm
Le@1kHz 0.69 mH
fs 23 Hz
Qms 8.80
Qes 0.31
Qts 0.30
Mms 58.5 g
Sd 366 cm2
BL 12.12 Tm
Vas 151 ltrs
Xmax 5.0 mm peak
VC 50 mm
Sensitivity 1W / 1m 91 dB
Nom. Power DIN 150 W

Some ideas...
1. Madisound (BassBox Pro) suggests 2 cu ft (57 liter) with Vd=3", Vl=9.7", Fb 28Hz. Port airspeed sims ~0.16 mach, iirc
2. WinISD Beta optimal is 2 cu ft (57 liter) with Vd=4", Vl=14.2", Fb 31Hz. Port airspeed 0.08 mach
3.I have a 85 liter sealed box already built that I used with this driver in sealed alignment. I'd like to use it if possible. I can reduce the volume if necessary, but I thought bigger volume is usually better? WinISD sim of 80 liters, Fb=28Hz, Vd=4", Vl=12" also looks good, with extended bass shelf type FR.
4. Your suggestion???

I want very natural, low distortion, clean bass for acoustic instruments like symphonies, string quartet, jazz bass, etc. I want to avoid that punchy ported sound. I want just natural sounding "invisible" kind of bass. That's why I picked sealed at first, to get the slower rolloff, less group delay, and avoid the fake punchy sound... but this driver is not so happy in sealed.

I previous owned some speakers that used these drivers in a vented box and they sounded much cleaner and tighter in vented, and they were not too punchy. I don't know the alignment specifics of those commercial speakers, Usher Be20, which used two of these drivers per side. I think I remember that they might have been ~3" Vd (x2 for two drivers) and rather longish Vl, but I'm not sure.

Thanks
Rich
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Old 20th July 2015, 01:22 AM   #2
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There is a port calculator here:
Port Length Calculator
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Old 20th July 2015, 01:42 AM   #3
sreten is offline sreten  United Kingdom
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Hi,

FWIW 85L tuned to 20Hz looks good to me.
Far better than circa 28Hz tuning in rolloff.
It optimises the -9dB point, room friendly.

rgds, sreten.
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Last edited by sreten; 20th July 2015 at 01:50 AM.
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Old 20th July 2015, 02:52 AM   #4
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Thanks Nigel. I am happy with WinISD beta simulator, just not sure where to aim it.

Quote:
Originally Posted by sreten View Post
Hi,

FWIW 85L tuned to 20Hz looks good to me.
Far better than circa 28Hz tuning in rolloff.
It optimises the -9dB point, room friendly.

rgds, sreten.
Thanks sreten, I was hoping you would comment here, because you always recommend larger cabinet. Why is the slower rolloff of 20Hz better than 28Hz tuning which has a sharper corner? Is it smoother sounding, less punchy?

My box is actually 80 liters after subtracting bracing and driver volume. I'd have to place the port on the outside. I can't fit the whole 24 x 4.5" port on the inside of the box. I can fit 12" inside and 12" outside. That would make the working volume of the box ~78 liters, which requires 27" Vl to make 20Hz. If I tune to 21Hz, I can keep the Vl down to 24" which is easily available pipe length. Does this sound OK? Do I still flare the ends even if it hangs out of the box?

EDIT: I can do 2 ports 12" long 2" diameter instead of 4", same mach. and fit them all inside. Sound good?
Thanks
Rich

Last edited by Richidoo; 20th July 2015 at 02:57 AM.
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Old 20th July 2015, 04:51 PM   #5
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In this old post by GM:

Calculating an EBS alignment

He says:
"Where Qt is the total Q of the system:"


Does his term "Qt" mean the Qts of the driver?
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Old 20th July 2015, 05:35 PM   #6
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by Richidoo View Post


Thanks sreten, I was hoping you would comment here, because you always
recommend larger cabinet. Why is the slower rolloff of 20Hz better than 28Hz
tuning which has a sharper corner? Is it smoother sounding, less punchy?

Rich
Hi,

The slower rolloff is more transiently correct *, tighter,
deeper and more punchy, but less weight and warmth.

Assuming its for a pair of speakers the slower rolloff allows
the speaker placement to interact with the room gain more.

rgds, sreten.

* The faster the response changes, the worse the transients.
So I like a bass roll with a smooth increase, and no kinks.
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Old 20th July 2015, 06:01 PM   #7
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Cool, Thanks. I am planning to try it.
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Old 21st July 2015, 03:06 AM   #8
Zero D is offline Zero D  United Kingdom
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@ Richidoo

Hi, though that driver might look ok initially on paper, unfortunately i think certain things have been overlooked !

See my sims with WinISD v 0.7.0.900 in 80L @ 20Hz fb

Also a 2" D port isn't really suitable.
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Old 21st July 2015, 01:07 PM   #9
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Thanks for checking it out, Zero D!

My WinISD Beta does not show excursion or power. WinISD website has only the old versions, but I found your 0.7 version on Facebook. Thanks!

I was planning to use two vents, @Vd=2" each, in order to reduce the vent length to fit inside the box. But that won't help with bottoming out! I assumed the port would limit excursion above resonance, but I guess that is more true of max flat alignment with smaller box.

I'll install the new WinISD then check the power at Xmax to see if it is enough for my normal listening, at least until I can build smaller boxes.
Thanks again!!
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Old 21st July 2015, 01:30 PM   #10
S4m is online now S4m  Germany
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The driver is a very well-known type by a german DIY-community.
It is used for the lower end part of the "Duetta" of Udo Wohlgemuth.
An english article with a drawing of the used enclosure can be found under following link:
Duetta - April 2012 - Loudspeakermagazine 2012 | Loudspeakerbuilding
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