Lab12 - Tapped Horn -

[weltersys]

Originally Posted by AndrewT

the electrical resistance of the driver generates heat when signal passes.
That heat limits the maximum power that the driver can handle.
If you have a speaker that is 1% efficient then when you apply 100W to the speaker 1W comes out as acoustic power and 99W is heat in the VC.

Now consider a driver that can handle 400W.
In a normal speaker it may be 2% efficient. i.e. 8W of acoustic power and 392W of heat.
Put that driver into a horn and passband limit the signal such that over the whole passband, the efficiency of the horn loaded driver is 50%.
The speaker can take 392W of heat and output 392W of acoustic power. 50% acoustic output for 784W of input.
Put two of those drivers into a dual driver horn with a measured efficiency of 50% and the Horn speaker will handle 1568W

If the efficiency is lower then the power handling capability is lower. 1200W to 1400W seems credible.
And amplifier ratings of around 2kW to 3kW for unclipped music reproduction is also credible.

Andrew,

The increased sensitivity of a large FLH means more acoustic power is produced per power run through the voice coil compared to a small bass reflex cabinet, but in no way reduces the heating of the voice coil at some ratio of output vs. power used.

The impedance of the voice coil determines the power absorbed for a given voltage supplied. If an enclosure design raises average impedance, the voice coil will draw less power for a given voltage.

Large voice coil movement in a vented speaker such as the Lab12 increases cooling, a horn load such as the Labsub decreases movement at a given voltage compared to a bass reflex, the net cooling may actually be worse for a FLH than a BR, so the horn loaded speaker in a small compression chamber may burn with even less actual power than a BR.

By the way, 100 acoustic watts generates 140 dB SPL, for a speaker to generate that level from 400 watts input would require a one watt one meter sensitivity of 114 dB, over an order of magnitude greater than the LabSub is capable of.

Art

[m R g S r]

I never posted the sub in its home....I'm using it as a TV stand. Tucks away nicely, hides its size!

[DrDyna]

Originally Posted by m R g S r

I never posted the sub in its home....I'm using it as a TV stand. Tucks away nicely, hides its size!

Very nice...hey I've seen that lid before!

[m R g S r]

^you mean you copied me? . I had my box finished a while before you started yours hehe

[David McBean]

Originally Posted by weltersys

By the way, 100 acoustic watts generates 140 dB SPL,

To be strictly correct, 100 acoustic watts generates 140 dB PWL (acoustic power level) not 140 dB SPL (sound pressure level).

SPL is dependent on radiated acoustic power, distance to the measuring point, directivity of the source and solid angle into which the source radiates.

PWL is dependent on radiated acoustic power only.

PWL = 10 * Log10(W / Wref) dB

Where Wref = 10 ^ -12 watt

If W = 100 then PWL = 10 * Log10(100 / (10 ^ -12)) = 140 dB

Kind regards,

David

[DrDyna]

Originally Posted by m R g S r

^you mean you copied me? . I had my box finished a while before you started yours hehe

Haha, yeah...its a great place for the lid...low pressure area, plus you can lift the driver right out easily.

[kees52]

It is old topic but I did find a woofer in holland who is almost a perfect replacement and it is cheap.

I do use this one with some small changes in the box, I have to learn how the folding is done, and of the hornresp is cm or inches..

http://ch.infinitysystems.com/tl_fil...260W_PI_EN.pdf

[j.michael droke]

Originally Posted by kees52

It is old topic but I did find a woofer in holland who is almost a perfect replacement and it is cheap.

I do use this one with some small changes in the box, I have to learn how the folding is done, and of the hornresp is cm or inches..

http://ch.infinitysystems.com/tl_fil...260W_PI_EN.pdf

Hi there k: HR dimensions are in metric. Ater using HR awile I found that I got use to visulizing dimensions in cm, although I wish the metric users would always note whether they are dimensioning in mm or cm (maybe there is a convention that: "if not denoted, all dimensions are in mm") ....Michael

[blossom]

Originally Posted by j.michael droke

"if not denoted, all dimensions are in mm") ....Michael

Thats the way we do it down here. Can't speak for elsewhere though.

[AndrewT]

When the UK converted to metric back in 1975 the adopted linear measure was and still is the metre (m). We also work strictly with 1000 as a multiplier and divider. But many are not aware of this.
As a result it was convention for all technical drawings in our office to be dimensioned in either m or mm and we did not append the unit. It was obvious which was being used, whether it be a manhole or a gas main or a roadway or a bridge support.
I believe we still work with that convention.