Does 0.5 way always imply 6dB of BSC ?

[sreten]

Hi,

Well it generally does, you get 6dB of correction, but if the drivers have
a rising response (into 2pi) then the overall response may not be 6dB.

However I have seen MMT 2-ways which off axis should be worse than MTM.

It begs the question : Instead of completely rolling off the 0.5 way driver,
why can't you just reduce its output by say 3dB to 5dB in the midrange
compared to the to driver driven fullrange (up to any c/o point).

I was thinking about this due to another thread regarding dual Aura NS3's.
0.5 way will work but might sound overall too bass heavy. Running them
in parallel requires some BSC, about 4dB according to Zaph, and you'll
get inevitable vertical lobing issues with two drivers.

However if the lower driver still runs full range, but at lower level, you
will get variable BSC, and reduced lobing nulls as the other dominates.

Just food for thought, I don't think 0.5 way has to be the full 6dB.

rgds, sreten.

[planet10]

What you get also depends on amplifier output capabilities. My amplifier puts out ~ the same power into 4 ohms as in 8 ohms so i get about 3 dB from a 0.5.

dave

[sreten]

Originally Posted by planet10

What you get also depends on amplifier output capabilities. My amplifier puts
out ~ the same power into 4 ohms as in 8 ohms so i get about 3 dB from a 0.5.

dave

Hi,

No. The voltage frequency response steps by 6dB in the bass for 0.5's
at any / all powers. What your saying relates to maximum bass SPL for
your amplifier, not the response, and is generally true, not many amps
double real power into 4 ohms compared to 8 ohms.

The issue I'm discussing is the frequency response, at any level.

Consider 2 FR's, 16 ohm each if you want, and manipulating the amount
of BSC of a 0.5 way with a variable resistor in parallel with the inductor.

rgds, sreten.

rgds, sreten.

[speaker dave]

I've gotten various amounts based on the starting curve of the first woofer.

At LF there will always be a gain of 6dB (assuming large choke is similar in DCR). Ideally you will have a 6dB rise for mid frequencies so that you can rolloff the "lower" woofer the maximum amount. If you have less than 6dB rise (in free space, I assume) then you can shelve down the lower woofer a little less to make the midrange level flat with the bass.

You probably know that you can only rolloff at less than 6dB per Octave to keep the phase rotation between the two woofers minimized. Also, there will be vertical polar response issues if the lower woofer isn't reduced enough by the right frequency. In the end you need to make the best tradeoff between those factors.

Getting bass and mid levels equal is always the overiding concern.

Regards,
David S.

[wg_ski]

Originally Posted by planet10

You are making the fallacious assumption that i have a constant voltage amp.

What? Those funny looking glass transistors with the orange glowing thingy in the center?

[planet10]

Originally Posted by sreten

True, but if your talking about a high impedance amplifier then
its your responsibility to say so, rather than be obtuse. That
aspect has not much to do with the point I'm trying to make.

Why? I stated how if performed, that is sufficient. I could equally well say that of you are talking about a CV amp that it is your responsibility to state such, but it is implicit in what you said (althou newbies might miss it)

dave

[planet10]

Originally Posted by wg_ski

What? Those funny looking glass transistors with the orange glowing thingy in the center?

Largely, but there are also a couple SS variable transimpedance amps around here where the output impedance can be dialed in to what is most appropriate for the speaker.

dave

[sreten]

Originally Posted by planet10

Why? I stated how if performed, that is sufficient. I could equally well say
that of you are talking about a CV amp that it is your responsibility to state
such, but it is implicit in what you said (althou newbies might miss it)

dave

Hi,

You know as well as I do that newbies (and not so new) will assume a CV amplifier.

Nevertheless if we are going to be pedantic, your claiming that your amplifier has
exactly the right output impedance such that power into 8R and 4R is the same.
(For a given input voltage and fixed amplifier gain, which is still not necessarily true
depending on the feedback (or not so it can be) topology of any given amplifier).

I can't be arsed to work out the implied output impedance because speakers are
not constant impedance, and 0.5 way will give you +6dB at a sealed boxes Fs of
the two drivers for example. This is just smugness regarding unusual amplifiers at
the same time not getting the actual technical details right. Its not on topic.

rgds, sreten.