why would genelecs have a 500hz bump?

[xy]

i remember Mr. Dorsey saying genelecs typically have a frequency rise
at 500hz, likely due to porting issues.

and then other people agreed as if it is a known, matter-of-fact
issue.

i'm "baffled" why such a highly-regarded company would let this kind
of design anomaly exist in their product line. any ideas?


and as a side note, what is an "infinite baffle"?

[Scott Dorsey]

xy > wrote:
>i remember Mr. Dorsey saying genelecs typically have a frequency rise
>at 500hz, likely due to porting issues.

That's a really narrow Q thing, and not all of the Genelecs do it.

>and then other people agreed as if it is a known, matter-of-fact
>issue.
>
>i'm "baffled" why such a highly-regarded company would let this kind
>of design anomaly exist in their product line. any ideas?

Because it's not really a problem. It's an organ-pipe resonance, and
if you know it's there, you can listen around it. I wouldn't consider
that acceptable for mastering work, but it's typical of studio speakers.

>and as a side note, what is an "infinite baffle"?

Imagine a speaker with a baffle and an open back. The lowest usable
frequency is directly related to the size of the baffle. Now, make the
baffle bigger and bigger.... and at some point you're dealing with a
speaker that is enormous but has good low end. Very popular in the
days before the Theile-Small work made it possible to design good boxes.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[xy]

so a speaker that is soffit-mounted perfectly to a giant hard wall is
something like an infinite baffle?


"organ pipe resonance". i can't even stand the thought of it! an
expensive speaker should not require a work-around like that, imho.
that's what cheap speakers force us to do!

[Peter Larsen]

xy wrote:

> so a speaker that is soffit-mounted perfectly to a giant hard wall is
> something like an infinite baffle?

Yes. And for this reason it requires a cross-over that is different from
the one used with a free standing loudspeaker or at the very least a
different equalizer setting.

If you design for free standing then the cabinet width becomes a factor
in how you choose x-over because you want to make it easy for yourself
to equalize the baffle diffraction step, some 4 to 6 dB shelving
acoustic high end Eq that must be counteracted in the x-over.

You can omit those concerns if you design for wall integration, in which
case frequency selection is only about loudspeaker unit diameter and Fs.

Those that make very narrow loudspeaker fronts do not necessarily make
it easier for themselves because they move the correction issue up in a
frequency range where it is much more audible in case the correction is
not correct, just my opinion.


Kind regards

Peter Larsen

--
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[xy]

tusen takk, Peter.

so if you soffit-mount a big mains system into a large wall, you need
to adjust the crossover. or if the wall is big or small it's mounted
in, that could affect the crossover.

never knew that. i only knew about the bass-boost effect. i learn
something new here everyday.

[Peter Larsen]

xy wrote:

> tusen takk, Peter.

> so if you soffit-mount a big mains system into a large wall, you need
> to adjust the crossover. or if the wall is big or small it's mounted
> in, that could affect the crossover.

Nah ... not really, you have to see this in the context of half a
wavelength, if the cabinet front is wider than about 1 meter, then other
effects start to matter more.

> never knew that. i only knew about the bass-boost effect. i learn
> something new here everyday.

Already the bass boost will cause unlinearity, because it tends to
shelve below 150 Hz. One is imo best off maximizing it, i.e. going close
to the corners of the room with the bass unit/cabinet so as to at least
get it as uniform as possible.

This too can rapidly become "of interest" when selecting where the
lowest cross-over frequency should be located. But please do understand
that cross-over math has to consider all units, one can not always move
single cross-over frequencies in a multiway system freely because they
also influence summing at the next cross-over frequency.


Kind regards

Peter Larsen


--
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* \\\\\\\ Quality Ascii handcrafted by Peter Larsen /////// *
* \\\\\\\ My site is at: http://www.muyiovatki.dk /////// *
************************************************** ***********