Fullrange + helper bass

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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 said:
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
 
ozziozzi said:
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
 
Hmmmm....

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

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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?
 
Thanks again guys for your interest, especially Scottmoose for the computations. You see what I meant about "ridiculous" size for BR design-about the size of a refridgerator!!

Nuuk, I have liked your design for "stealth" TL hidden behind OB baffle since I first saw it. Unlike you, I do have a significant other to please so every little bit of concealment of technology helps. I am trying to make my designs look more like furniture or modern sculpture rather than industrial equipment. See my latest effort below which uses 70's SEAS units-2X 16ohm mid/woofers + 38mm dome mid/tweet XO at about 1.5kHz. Woofers are U-frame open back. Bass is there to ~35Hz and smooth, but down in level, so I am considering activeXO and two amps.
SEAS drivers have good Xmax so can stand a bit of a boost at low freq.

Is there any reason why I couldn't Nuuk's design 90degrees and increase the TL width to achieve area suitable for 10" driver instead of 8"? That would hide more of TL enclosure behind the front baffle--especially from the side. BTW I love the glass side panels to increase baffle width without optical bulk. V nice.
 
Thanks again guys for your interest, especially Scottmoose for the computations. You see what I meant about "ridiculous" size for BR design-about the size of a refridgerator!!

Nuuk, I have liked your design for "stealth" TL hidden behind OB baffle since I first saw it. I have a significant other to please so every little bit of concealment of technology helps. I am trying to make my designs look more like furniture or modern sculpture rather than industrial equipment. See my latest effort below which uses 70's SEAS units--2X 15ohm mid/woofers + 38mm dome mid/tweet XO at about 1.5kHz. Woofers are U-frame open back. Bass is there to ~35Hz and smooth, but down in level, so I am considering activeXO and two amps.
SEAS drivers have good Xmax so can stand a bit of a boost at low freq. The wooden "waveguides" are an attempt to time-align mid and tweeter physically with woofers. The wooden trim rings (photoshopped on, but now real) are my wife's idea to improve design.

Is there any reason why I couldn't turn Nuuk's design 90degrees and increase the TL width to achieve area suitable for 10" driver instead of 8"? That would hide more of TL enclosure behind the front baffle--especially from the side. BTW I love the glass side panels to increase baffle width without optical bulk. V nice. Scottmoose, I would probably go with non-tapered TL, but would like to fold it a bit. Are there any serious consequences of folding, esp if I keep input below 200Hz?
 

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Couldn't attach two pics to one reply-don't know why. Here is the SEAS driver box--a sort of test mule.

Front baffle ~260mm wide and sides about 280mm each for a total equivalent to flat baffle width of about 820mm wide. Top and bottom panels also 280mm wide and height between about 500mm so equivalent to baffle height of about 1080mm. If that makes sense. Front baffle is jointed blackwood planks 30mm thick. Side panels 25mm Tasmanian oak hardwood, top and bottom panels veneered MDF. I have easy option to fit different mid or fullrange in centre position and tweeter in top position and to go totally OB for FR driver and woofers.

Back of woofers is stuffed with a roll of polyester fill with rubber-backed carpet tiles glued to side, top and bottom walls to dampen panels. I have the option to convert present U-frame to sealed or aperiodic enclosure by screwing on a back and fitting vents.

In this present for I can't detect any midrange resonances due to cabinet standing waves or panel resonances. The sound is open and uncoloured, but bass levels are a bit low and require boosting of bass tone control on amp.
 

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The reason that I didn't make my woofer TL vertical was that it would have obscured the rear of the open baffle driver(s). However, there is this commercial design that uses a vertical TL woofer placed a little way behind the main baffle.

Moving to the Hawthorne Audio Augies, I got the same performance in a fraction of the space, so the TL's sadly went to the recycling centre. :cannotbe:
 
Nuuk said "so the TL's sadly went to the recycling centre."

Dear Nuuk, what a strange coincidence, the recycling centre is where I source most of my drivers. But that's another thread...

Thanks for all helpful suggestions. Back to the workshop to start my OB + helper TL.
 
No, there's no real issues with folding a damped LF TL as the wavelengths involved are too long to be concerned about corners etc. Everything higher up which would be concerned about bends isn't wanted for your purposes & will be killed by the stuffing.

Re the width, a TL's cross section has nothing per se to do with the driver's cone area, so, for example, a simple increase in width of an existing cabinet won't really work very well (especially if the existing box was designed assuming the line area had something to do with Sd). It'd need designing from scratch based on the driver's parameters, like the one I did above.

I assume we're still talking about the Jaycar units here? The TL I did above is about the smallest you're going to be able to get away with, although as an alternative, GM suggested this one, based on the same math, but with a different nominal tuning frequency which will give similar results (actually, a touch more gain at the lowest frequencies).

L = 80.426"
CSA = 144.352"^2
1.152 lbs/ft^3 stuffing, end-load the driver for flattest impedance

Volume is similar to the one I did above, as you can see, but it might be a bit more practical for you to fold up as being longer, its cross section is somewhat smaller & it requires a lower stuffing density as a result.
 
I think I will go with Scottmoose's first suggestion "Max flat impedance TL. 52.328in long, 228.17in^2 CSA, Zdriver 21.23in. Stuff 1.568lbs ft^3 of dacron or similar".

Scottmoose Can I please just have a reality check on quick calc of box dimensions

228.17inches^ CSA (Cross Section Area Yes? eg 15" x 15" is 225inch^ about right - Yes?)

Using that CSA, I end up with a box about 27"H x 30"D X 15"W (internal dimensions) with a partition down the middle that is approx 12" high. This gives a folded TL length of approx 54" with a CSA of 225 square inches. Would I then put a vent of the same dimensions in the back of the box- ie 15" x 15"?

The total volume of this box is about 6.7cuft or 190 litres less driver, partition and bracing.

Does all that sound about right?
 

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