Fullrange + helper bass

[ozziozzi]

Dear members, I love the sound of small fullrange drivers, especially OB, that I have experimented with over a few years, but I miss the little bit extra bass that a 10" to 12" driver can provide. I have been experimenting with helper bass drivers, but most have not worked well on OB. So I have decided to build sealed, ported or TL as a base for my open-baffle full-range experiments. I mostly listen to jazz combos, but some big-band music. I am thinking range 35Hz to ~200Hz as suitable, meaning that i will not need sub(s).

I recently acquired an almost-new pair of the following drivers used as replacements in a pair of thrift-shop ~ 50L BR 3-way JVC boxes. I have tried a few online box calculators, but none seem to agree on sizes for sealed or ported boxes for these drivers. Can someone please run these parameters through a *trusted* box design program and/or recommend a good speaker box calculator that will run on my Mac OSX PC. Pointers to any suitable existing designs would also be appreciated. Many thanks in advance.

Specifications: JAYCAR CW-2119 paper cone, rubber roll surround woofers
- Nom impedance: 8ohms
- Power handling: 40watts RMS
- Frequency range: 31Hz - 3kHz
- Sensitivity: 87dB 1watt 1metre
- Voice Coil Resistance (Re): 7.4ohms
- Resonant frequency (fs): 31Hz
- Mechanical Q factor (Qms): 2.898
- Electrical Q factor (Qes): 1.057
- Total Q factor (Qts): 0.775
- Equivalent Volume (Vas): 115Lt
- Cone Area (square metres): 0.0346

Typical Application: (According to JAYCAR Catalog)
Sealed Box
- Box volume (litres): 40 Lt
- Tuning Freq (Hz): 61Hz
- - 3db Frequency (Hz): 42.3Hz (would like to get this value lower!!! edit Ozzi)
- Qtc1.59 (does this mean over-damped design???? edit Ozzi)
- Inside Cabinet Dimensions:W: 275mm; D: 345mm; H : 437mm
- Speaker dimensions: OD(A) 258
- Mounting holes B 245mm , Cutout C 231mm

[Fuling]

Hi,

I can´t help you design a box, but I´m a big fan of the "small fullrange + woofer concept". Fullrange drivers usually sound much better when they don´t have to reproduce bass.
IME sealed bass boxes integrates better with the FR´s than BR boxes.

[LineArray]

Originally posted by Fuling
Hi,

I can´t help you design a box, but I´m a big fan of the "small fullrange + woofer concept". Fullrange drivers usually sound much better when they don´t have to reproduce bass.
IME sealed bass boxes integrates better with the FR´s than BR boxes.

Hi Fuling,

i share Your liking of the Fullrange & Woofer/Subwoofer concept.

Preventing the fullranger from large excursion by
active or PLLXO highpassing is very advantageous for most
fullrange drivers, due to reduction of distortion and an increase
of dynamic headroom.

But i would say the subwoofer has not to be sealed one
necessarily, maybe this is a little different when using a
woofer with higher XO frequency ... don't know.

I see no problem in integrating a BR subwoofer, as long as it
is properly aligned in matching the listening room and its
particular fullrange - now wide range - partner.

Kind regards

[LineArray]

Originally posted by ozziozzi
Can someone please run these parameters through a *trusted* box design program
(...)

Hi ozziozzi,

dunno if WinISD is recognized "trusted" but for those
tasks the results have been OK so far.

Your Driver has fairly high Qts and Large Vas so
WinISD comes up with

418 liters -3dB around 30 Hz Qb 0,88
150 liters -3 db around 32 Hz Qb 1,03
100 liters -3db around 34 Hz Qb 1,14
80 liters -3 db around 35Hz Qb 1,21


To me all these alignments are not useful.

Qb far above 0,7 will result in a hangover bass response
and a hump in frequency response thereby increasing the
range where you normally get roomgain too.

What JAYCAR proposes is a "boombox" , Qts over 1,5 is
not worth discussion.

If the Xmax of the driver would be very large (dunno) then
an open baffle design would be possible.

This driver is more suited for a transmisionline or
maybe aperiodic box design.

Kind regards

[sreten]

Hi,

They are not good drivers for boxes, according to the specs.
They are typical of old 3-way boom-box bass parameters.

/sreten.

[Scottmoose]

Hmmmm....

Max flat impedance TL. 52.328in long, 228.17in^2 CSA, Zdriver 21.23in. Stuff 1.568lbs ft^3 of dacron or similar.

[ozziozzi]

Thank you all for your comments. It looks pretty conclusive that sealed box ala Jaycar is a disaster and best avoided. (As I suspected) My options in order of easiest tried out:

OB - high Qts seems to be suitable according to many OB fans on this forum - agreed? I could take care of differing efficiencies of woofer and FR by activeXO or PLLXO and two amps which I have already. I imagine big as possible solidstate amp for woofer and tube or classA SS amp for FR-does that sound about right?

Aperiodic - something like AR or WD aperiodic designs could be good start.

TL - I like TL and have built Konus Essence/Jordan VTL semi-clone with good results.

LineArray, did you model BR box? I got ridiculously large box when I tried.
Scottmoose, do you recommend straight TL or tapered for my driver? Z is distance of driver from closed end of line right?

[Scottmoose]

Correct.

The one above is untapered. Tapering like anything is a double edged sword -gain some advantages, loose out elsewhere. For these, I'd make life simple for yourself.

[LineArray]

Originally posted by ozziozzi

LineArray, did you model BR box? I got ridiculously large box when I tried.

Hi,
i havent even tried, you won't find a usable alignment
for that driver.

Best

[Scottmoose]

Right. Think 29.3ft^3 for BR.

Two sealed boxes.