Two different drivers in the same box

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Tyimo

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Joined 2002
#1
Hi!
I saw sometime that two different drivers (in size and Qts) was built in the same box volume. I saw it in Bass reflex,TQWT and BLH boxes too.
- How can I calculate such a speaker?? With average Ts parameters??

Another question:
- Is it possible that two different drivers in a BLH speaker share in the same horn section? (The back chambers has different size, but the horn lenght in a section or the mouth is the same.)

Tyimo
 
#3
Here's the guts of it, without the waffle:
For the parameters of a compound driver,
Add the Vas and Sd of both Drivers,
The new Fs, Qes, Qms, becomes the geometric mean of the two drivers values, (square the actual two values, add them up, divide by two and then take the square root).
The Voice Coil DCR (Re) are paralleled. (Unless you decide to put them in series)
 
#5
For the parameters of a compound driver,
Add the Vas and Sd of both Drivers,
The new Fs, Qes, Qms, becomes the geometric mean of the two drivers values, (square the actual two values, add them up, divide by two and then take the square root).
The Voice Coil DCR (Re) are paralleled. (Unless you decide to put them in series)
Click to expand...
Thanks! This I thought.
Now only one question is remained:
-Is it possible that two different drivers in a BLH speaker share in the same horn section? (The back chambers has different size, but the horn lenght in a section or the mouth is the same.)

Tyimo
 
#6
There were a couple of Speakerlab systems with dissimilar woofers. The S7WA with a 10" and 12" driven in parallel electrically in a single chamber. The model 30 which used 10" and 8" woofers in a single chamber, but with a patented Nestorovic coupling network which decouples the 10" woofer at lower frequencies.
Low range loudspeaker system - Patent 3984635
This discussion about Vandersteen speakers also mentions that patent:
Vandersteen 2C: Room for improvement? [Archive] - AudioKarma.org Home Audio Stereo Discussion Forums
 
#7
Different sensitivity drivers connected paralell

Hi!

Another question:

What happens when two different sensitivity drivers connected paralell? For example 88 and 92dB. Do I get the +3dB sensitivity???

Greets:
Tyimo
 
#8
River757 said:
Years ago, many designers felt comfortable having drastically different drivers share the same volume (more sensitive hobbyists may not want to view the photograph in the following thread 😉): scroll down to post #15 😱 The good ol' days weren't always all that good............
Click to expand...

The designers may not have been so keen, but the accountants & salesmen probably thought it was an excellent idea.
 
#15
Hi,

Two very different drivers can share the same volume, but average
parameters are a very clueless approach, which gets worse the
more the drivers differ in size and parameters.

If you get it all right it can work very well, though it has to said in
reality, if you split the rear volume in the correct ratio, in the end
it would make next to no real difference, it would make no real
difference as to the suitability of running the drivers in parallel.

If they are well suited the partition is not necessary. If it
is necessary they are not well suited to be run in parallel.*

rgds, sreten.

*Disregarding seperate active power to each driver.

A low Qts low excursion driver can work in parallel
with a higher Qts higher excursion driver. A high Qts
low excursion driver hasn't a prayer of working well
with a low Qts high excursion driver in parallel,
whether or not the volume is separate or shared.
 
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