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Some questions about the Lii Audio F15 please ...
Some questions about the Lii Audio F15 please ...
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Old 15th August 2020, 02:06 AM   #1
ernie000 is offline ernie000  Australia
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Default Some questions about the Lii Audio F15 please ...

Hello all , I have some questions about this driver from Lii Audio in China :

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I am considering building this enclosure posted on their website :

Click the image to open in full size.

I only have this 6.5W single ended tube amp :

Click the image to open in full size.

Is this tube amp sufficient to drive these speakers ?
( I don`t play very loud )

Could someone more knowledgable on speaker design give their opinion on this design , or alternatively , know of a similar enclosure plan suitable for this driver ?

( I don`t have room to correctly place any open baffle speakers ), so I`m only really interested in a large bass reflex cabinet.


Would I need a sub ?

Thank you .
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Old 15th August 2020, 12:36 PM   #2
waxx is offline waxx  Belgium
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If that amp can deliver 3-4 watt or more, it should be enough in a typical livingroom situation. 97dB is already very loud in a typical living room, and 4 watt theoretically adds 6dB to that, and then add an other 3dB if you have a pair of speakers. But you never play full power with tube amps (or they distort to much). Most of the time i guess you won't even send 1w to the speaker, it will be more a few dozen to a few hundred mW...

And a sub is needed if you need a real deep bass, This driver has an FS of 49Hz and the box tuning should be similar i guess (but we lack that info) and in most cases that is deep enough. But if you listen to music with a very deep bass or a lot of bass a sub may be needed. A typical commercial bookshelf cuts way higher than that (60 to 100Hz) and most floorstanders are in that region (40 to 60Hz) so...
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Old 15th August 2020, 01:13 PM   #3
ernie000 is offline ernie000  Australia
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Default Great

Great waxx , i was hoping to hear that.

This is my first tube amp , and it`s all a learning curve for me.
I think I will commit to buy these drivers then.

Many thanks for the great advice.

Last edited by ernie000; 15th August 2020 at 01:18 PM.
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Old 15th August 2020, 04:33 PM   #4
Richard Ellis is offline Richard Ellis  Argentina
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Crunching the numbers on the WinISD simulator, the program wants to select a sealed enclosure since it derives its EBP from resonant frequency, (Fs) and Qes, its ability to control the cone by electrical means. The 63.78 value of Qes is shockingly low, very very little electrical control...the bulk of control via the mechanical suspension, (Qms).
A sealed enclosure models out to 600 plus liters in internal volume...EG 700 liters sealed gets an F3 of 50.06 hertz at -3.02 Db.
Switching to a ported enclosure, the volume is well over 1000 liters in size, and those extra 25 hertz at the bottom can be obtained.




------------------------------------------------------------------------Rick..........
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Old 16th August 2020, 12:28 AM   #5
GM is offline GM  United States
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Right, the factory cab is so acoustically small I just did a 'close/good enough' sim = ~278.5 L, ~38 Hz Fb with a +3 dB/70 Hz mid-bass 'bump'.

100 dB/m/3 W/2pi/2 mm limit from ~32 Hz-up, so factor in the amp's high output impedance and it will have an even more 'robust' low corner and of course even more up against a wall and especially a corner, so short of low B pipe organ, low C piano or true infra/sub-bass special effects, no sub needed.

All assuming published specs being accurate of course, so caveat emptor!

In short, its specs 'screams' sealed or some form of compression loaded TL/horn.

GM
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Old 16th August 2020, 01:30 AM   #6
ernie000 is offline ernie000  Australia
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Hi GM

Thank you for the help.

I`m trying hard to understand all this , are you saying that I could use sealed box around 278 L ?
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Old 16th August 2020, 02:19 AM   #7
GM is offline GM  United States
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Greets!

'Sealed' in the sense that with such a high Qts that will be much higher coupled to your amp it ideally needs to be an infinite baffle [IB] of at least 10x [measured] Vas, though in reality could be as little as [measured] Vas/1.44 and lossy vented [~aperiodic] to bleed off its excess 'Q'ness, though of course the bass goes with it to a greater or lesser extent depending on how much the amp increases it by tracking the speaker's impedance.

The pioneers used stuffed pipes of varying tapers to acoustically 'squeeze' it out or when the marketability of high price/size was available, a large back loaded horn such as EV's ~ 35 Hz, 30 ft^3 Patrician.

Frankly, having recently auditioned dbx's latest relatively inexpensive pro speaker system management [DSP], my training/recommending solving acoustic problems with acoustic solutions has pretty much gone the way of the Dodo bird, especially now that the 'world' of available audio room 'real estate', quality time is shrinking at an alarming rate for all but the relatively wealthy.

In short/short [or not as it turned out], when going low at high SPL isn't a primary goal because of a lot of room gain or using a separate [sub] bass system, then going as high as a 3.0+ [effective] Qtc' [not a misprint, I've built speakers with measured 2.85 Qts + 8 ohms tube amp output impedance, so know it's doable acoustically] and DSP this 'one note' boom box flat over the desired BW and call it a day as life's getting shorter/more hectic with each new politician it seems.

GM
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Old 16th August 2020, 02:54 AM   #8
ernie000 is offline ernie000  Australia
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Thank you so much GM.
I have further reading to do.

In awe of your knowledge , it almost feels intimidating !
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Old 16th August 2020, 03:31 AM   #9
jjasniew is offline jjasniew  United States
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Some questions about the Lii Audio F15 please ...
I have a set. Mine are in OBs. I assist the low end with a pair of 18s. Crossed at ~100Hz, using DSP. I played with REW and made a EQ and got the response, shown, one time. Then I changed the whole amplifier system to something different, sans mini-DSP.

They sound really good on piano music, which is what was said that caused me to buy them in the first place. I really like 'em!
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Old 16th August 2020, 04:17 AM   #10
ernie000 is offline ernie000  Australia
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Hi Joe

Could you tell me please , how far from the wall do your OB have to be ?

This is the main reason why i don`t think I can go OB.

I just can`t get back far enough .
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