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In the Forum: Audio Discussions
In the Thread: The ULF cannel for my new listening room.
Post Subject: Some initial thoughts...Posted by Romy the Cat on: 7/29/2018
All thinking about ULF are usually centered on 3 subjects:
drivers, topology and amplification. Even though these 3 subsets very much intertwined
I still would like to talk about it separately. We do presume that we have the proper
drivers for proper topology with proper amplification. When wrong type of
driver used for a given topology or wrong amplification applied then there is truly
noting to talk…
The absolute majority of ULF solutions out there today are different
variations of ported enclosures. It is know that I hate any ported bass, including
is super expensive implementations. Still, in most of the cases implying bass I
am taking about auditable bass that always to my taste has some foreign vowels in
it. It is a valid presumption that is a ULF channel is crossed under 20Hz then
the auditable port accent might not be heard. Years back Wilson Audio made the XS
model with two 18” in a ported configuration that meant to run under the large
Grand Slamms. That would be sub 20Hz setting and it something that might be aligned
with what I am looking. Still, the large ported implementation similar XS takes
a very large box and I do not want to invest my listening room with such a monstrosity.
Also, I need to admit that I have no skills to make a ported
design to sound better. Sure I can load the T/S in spreadsheet and circulate
the necessary detention and to invest money into better peripherals but my hunch
suggests me that it is not how good sound archived. I do not see myself to
dedicate much efforts to learn about ported design decisions and its sonic consequences.
Well, there is direction to buy a ready to go bass sections,
so call subwoofers. Here is the problem. There is practically no products out
there that might be used for ULF application. Most subwoofers meant to be used
for auditable range. Let to look at the good commercial subwoofers. JBL for instance
use to have a very good driver 2245H with resonance frequency 20Hz, QMS 2.2 and
BL21. You can makes a very good sounding ported subwoofer with it serving very
nice 30 or 40Hz. As you driving it harder or go lower in a larger room then with
xMax 9 mm it is not so useful. JBL replaced 2245H with modern version 2269H, it
has FS 28Hz more BL and xMax at sub 20mm. You can drive this beast much harder
and JBL made number of new LB section around the driver: MD7, Sub18 and a few
others. All of them are ported at low 20Hz and they can handle “some” power abuse
at transition slope. This type of solution is also big and I would need to be
very careful to enter an auditable range as the Fs is to close.
The seals enclosure are foe sure the kind in my view but
having 10-20dB lower out at RS you need a lot of drivers to get some SLP and
VERY large box to avoid problem in case internal volume compression kick in.
The horns also out if picture foe me. It might be a good
idea to go for midrange horn and use my current LF section for midbass but I do
not have in me stamina to unleash myself on another Midbass horn project.
There is a direction
that I am looking now – the Infinite Baffle (IB). It was almost a cream de la cream topology, superbly
hard to implement and very had to implement. The funny part is that my new listening
room almost made foe IB. I have a very cool second sealing above my listening
room and I am considering to put IB in there. With IB drivers need to be able
to handle high exertion and a lot of power. I have in my storage 8 Aura 1808
drivers. They are 96dB sensitive, tunes for 25Hz and under 18mm Xmax, the most important
is that 1808 undehung! So, I am considering to put 2-4 per channel, in IB
configuration, loaded into an open triangle. There are some other options. The AeSpeakers
have cool driver IB18HT. It is not underhang but with Apollo update it might be
useful. It tuned for 18Hz, 18mm eversion, slightly less BL and less sensitivity.
I will be exploring more IB options during the ways and
weeks to come…
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