I had a second livingroom - or a
dedicated hifi-room, these panels would be there.
View pics below. The JA8008/TW034 combo helped by
the 15" Eminence bass drivers will probably
never come closer to projecting a live feeling.
In that respect they even beat the DTQWT by a
small margin. But... it comes at a price, a
serious price: Panel size, a suitable room, an
electronic crossover + extra amps - and not least
Whether your room can accommodate these panels is
the first thing to consider. 20 square meters is
probably minimum for these speakers to breathe
properly and if your room does not allow for
experimentation with placement, look elsewhere.
Our livingroom is 24 m^2 and the panels were
placed on the longest wall. As discussed in the
OB7 file, a more optimal placement would probably
be like this:
What's seen above to the right is
well on accordance with Gilbert Briggs'
recommendation for the SFB - way back in the
What I almost hate to
admit is the quality of the sound coming
from the JA8008/TW034 combo after passing
countless operational amplifires in the dbx
electronic crossover + not to forget some
off-the-shelf interconnects. No wonder
professionals sometimes shake their heads hearing
NFB triode nerds praising their trade.
getting into details, here's the recipe:
- 1 x JA8008/TW034 kit (= a pair),
available from Jantzen Audio, mail for quotation here.
- 2 x Eminence Deltalite II 2515 bass drivers,
available from here.
- 1 x electronic crossover, 24 dB L/R with
variable point of crossover
- 2 x stereo power amps, anything from 20 watts
and up will do. Small SET amps can easily run the
- A decent clone of the beautiful vintage
Wharfedale SFB speaker.
- Liniarise Deltalite II impedance from 15 uF +
10 ohms across terminals.
- Add baffle step loss compensation to the bass
drivers from 8.2 mH bypassed by 4.7 ohms.
- Hook it all up, set point of crossover between
80 Hz and 160 Hz to your liking.
- Make coffee from freshly ground Arabica beans,
pour a decent cognac, sit down in your favourite
chair and enjoy the concert!
After numerous experiments
with passive crossovers between bass and mid
drivers, I gave it up. Having a pro dbx
2-way/Mono 3-way 24 dB, L/R electronic crossover,
I inserted this between bass and mid and set the
point of crossover at 80-120 Hz.
The 4th order electronic crossover makes a smooth
transition between bass and mid and I suggest
point of crossover at 120 Hz, but take your time
and try vocal recordings @ 80-100-120-140 Hz and
make your choice. Going higher draws vocals
towards the floor and it starts sounding a bit
Some other time I'll get the passive crossover in
place. I want it simple, but this ECN set-up
works darn well.
The current set-up
makes a really big speaker and and it can play
immensely loud with low distortion, so take care
of your hearing!
There's an excellent live feeling to the
presentation and I won't hesitate to recommend
the current system for main speakers in recording
studios, built into the walls in front of the all
the mixing gear. With 220 liter cabs to the
Eminence drivers and a port tuning of 32-35 Hz we
will have response down to around 30 Hz. The
8008/TW034 could do with 25-30 liters. Well,
Those who do open baffle
studies may wonder why a relatively
low-Qt (0.38) bass driver was chosen here. The
Eminence 2515 will produce some 97-98 dB/2.8
volts and I simply wanted some extra sensitivity
to play around with, and it's easy to tune the
bass driver down to 94-95 dB, which is needed to
match the 8008 driver. The Deltalite has a speedy
and punchy bass response and from my OB7 baffle
the main problem is identifying all the things in
your room that starts rattling! What the
Deltalite does on this baffle is making the music
not only emotional, but also physical. Upright
bass players will love the sound from these
panels. Two 15" drivers hardly move driven
even to very loud levels, i.e. distortion is as
low as can be.
Left: The JA8008 and TW034 drivers. Right: Eminence
Deltalite II 2515 bass driver.
Click Deltalite for large image.
The finished speaker will resemble the legendary Wharfedale
SFB. But until then, the OB7 baffles will be
Tilt baffle 5-7 deg. depending on listenning position.
crossover. Yes, the bass driver needs a passive crossover
before the ECN.
The C-coil by-passed by 5 ohms takes the sensitivity down
to 8008 level and provides baffle step compensation as
Use 24 dB L/R ECN between bass and mid-tweeter section.
and complete crossover kit available from Jantzen Audio:
OB9 in our livingroom, hard to overlook!
Rotel amp in control of the bass drivers and Audio Mirror
amps for the mid and tweeter.
dbx electronic crossover hanging on the right speaker
There won't be a whole lot of measurements
on this construction as the upper part very much can be
seen in TQWT and DTQWT files. What's interesting here is
the performance of mid and bass driver around point of
crossover - and unfortunately it's pretty hopeless to
present frequency response graphs in the bass region as I
do not have an 8,000 cubic meter anechoic room like
B&O. And even if I had, it wouldn't represent what's
going on in our living rooms. Open baffles and the room
they are placed in are so much an integrated system that
any frequency response graphs will only reflect what's
going in that particular room - at that particular
location - and from that particular measuring point.
Impedance of Eminence driver on baffle. Driver not broken
Right: Red = SPL @ 2.8 volts, 1 meter. Blue is from
filter applied (1/3 octave smoothing).
This is an excellent response from a 15" driver.
Smooth response up to 3-4 kHz from where it rapidly
Response of all driver on baffle.
Right: 8008 response @ 2.8 volts. Around 94 dB in the
midrange, which is slightly less compared to measured
response in TQWT and DTQWT, but here we have a dipole,
thus we have to take rear radiation into account.
JA8008/TW034 set-up. Huge Eminence Deltalite II 2515
Grid preamp and dbx 223XL electronic
view with JA8008/TW034 crossover and equaliser on the
bass driver. These 15" bass drivers barely move,
even at loud playback levels.