FAST OR Foolish

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harvylogan

harvylogan

Member
Joined 2007
I have been considering a small bookshelf FAST design for a while now utilizing a driver like this for the bass because of the low extension that can be obtained for a small bass reflex box:

http://www.parts-express.com/pedocs/specs/264-917-tang-band-w5-1138smf-specifications.pdf

My original thought was to team it with somthing like this with a low crossover point of around 400-800 Hz.

http://www.parts-express.com/pedocs/specs/296-725-fountek-fr58ex-specifications.PDF

As I was pondering driver choices I remembered I have had a few of these around for many years that are not being used:

http://www.parts-express.com/pedocs/specs/277-307-focal-specifications-44432.pdf

My question to anyone who would like to comment is this:

With an efficiency of 93.5 db for the Focal and an efficiency of 82 db for the Tang Band I would have to pad down the Focal some 15 db (?) including BSC to get the drivers to match. Since I am padding the Focal down so much could the crossover be lowered to say 1200-1500 Hz without damage to the tweeter? Maybe using an LR4 as well?

Would there be other ill effects?

FAST or Foolish?

Thanks for any input.

Matthew
 
Greebster

Greebster

Member
Joined 2010
Most users have the TC120 no lower than 2.2k LR4. Xmax limited ±0.5mm. Crossover is normally 2x Fs min. and in this case is ~1800. As you go lower in frequency the distortion will rise dramatically.

Quite the mish mash of drivers I'd say. Reason for choosing the TB?
 
S

sreten

R.I.P.
Joined 2003
Hi,

The focal tweeter is a complete non-starter for such
a project, and not that easy to get hold of nowadays.
Sort of thing that can only go up in its selling price.

FWIW the TB with the PE BMR12 x/o'd 1st order
might be an idea, with passive line level BSC.

rgds, sreten.

Venting a Qts = 0.5 driver usually means you
can use a bigger lower Qts driver in the same
cabinet. The TB is for tiny, about 5L, sealed,
unless your into boombox vented / bandpass.

Box volume larger than driver Vas is always
bad, there are always better choices available.
 
Last edited:
harvylogan

harvylogan

Member
Joined 2007
Greebster said:
Most users have the TC120 no lower than 2.2k LR4. Xmax limited ±0.5mm. Crossover is normally 2x Fs min. and in this case is ~1800. As you go lower in frequency the distortion will rise dramatically.

Quite the mish mash of drivers I'd say. Reason for choosing the TB?
Click to expand...

I haven't yet. Just one of the considerations for a small bookshelf FAST. They are attractive because WISD says the will go much lower in a small box than a proper 5" mid/woofer. I haven't settled on them because although the sim says they will go low, it doesn't tell me anything about distortion. But lets face it. @ $28 each I cant really expect much or lose much to risk.

I haven't settled on the Fountek either. The Focals are extras I bought on sale for backups on a project from many years ago that I never needed.

I have however considered doing a proper 2-way bookshelf design utilizing the Focal and a 5" mid/woofer with a more conventional crossover frequency rather than the FAST design.

In either case I would like to keep the cabinet volume around 8-10 liters. For this volume a don't think I could realistically expect an f3 much below 50-60 Hz. The sim for the TangBand says the f3 for this volume is around 35-40 Hz.....which is what makes it attractive to begin with.
 
harvylogan

harvylogan

Member
Joined 2007
sreten said:
Hi,

The focal tweeter is a complete non-starter for such
a project, and not that easy to get hold of nowadays.
Sort of thing that can only go up in its selling price.

FWIW the TB with the PE BMR12 x/o'd 1st order
might be an idea, with passive line level BSC.

rgds, sreten.

Venting a Qts = 0.5 driver usually means you
can use a bigger lower Qts driver in the same
cabinet. The TB is for tiny, about 5L, sealed,
unless your into boombox vented / bandpass.

Box volume larger than driver Vas is always
bad, there are always better choices available.
Click to expand...

I have 4 of the Focal 120s. I bought about 10 of them from Elliott at Zalytron for $24 ea along with a bunch of other drivers for a big project back around 1985?

At any rate I am not sold on the TangBand driver for this application. I don't want to go over 8-10 liters. I would like to use the Focals because they are just laying around collecting dust and rusting.

I really like some of the designs I have seen from Paul Carmody (OS) and Jeff Bagby (Continuum) and would like to do a similar 2-way with the Focal. I am looking at some 5" woofers that may be a relatively good match. Its hard to find a mid/woofer that small that has enough efficiency. The original project I did with the Focal 120 was an Aria 5 which utilized 2 Focal 5k013 5" in an MTM. This helped the efficiency of the mids. Going to one driver in a smaller box makes it much more challenging.
 
S

sreten

R.I.P.
Joined 2003
Hi,

The Focal tweeters are now sought after and will sell
for a price that gives you plenty of tweeter choices.

Nowadays small 2 ways are clearly delineated. High
efficiency has no bass and is for use with a sub.
Low efficiency has bass but is limited in volume, and
still needs a sub for low bass and decent volume.

rgds, sreten.
 
S

ScottG

Member
Joined 2003

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j.michael droke

Member
Joined 2009
FAST Biamp

harvylogan said:
I have been considering a small bookshelf FAST design for a while now utilizing a driver like this for the bass because of the low extension that can be obtained for a small bass reflex box:.....My question to anyone who would like to comment is this:

With an efficiency of 93.5 db for the Focal and an efficiency of 82 db for the Tang Band I would have to pad down the Focal some 15 db (?) including BSC to get the drivers to match. Since I am padding the Focal down so much could the crossover be lowered to say 1200-1500 Hz without damage to the tweeter? Maybe using an LR4 as well?Would there be other ill effects?FAST or Foolish?Thanks for any input. Matthew
Click to expand...

Hi there h: Have you considered matching your speakers of choice using Biamp? ....regards, Michael
 
harvylogan

harvylogan

Member
Joined 2007
ScottG said:
Yeah, just found that out..

Better (for the gain in relation to baffle step loss) if a more expensive choice however:

The Madisound Speaker Store
Click to expand...

Interesting. That driver was one of the front runners I am considering teaming with the Focal in a conventional 2-way. I find it interesting that a driver with such potential has so little documentation as far as DIY builds are concerned.
 
harvylogan

harvylogan

Member
Joined 2007
j.michael droke said:
Hi there h: Have you considered matching your speakers of choice using Biamp? ....regards, Michael
Click to expand...

My current system is a 4-way active open baffle design of my own. I am very pleased with the audio capabilities and spend hours of listening enjoyment.

My motivation for this design is to take a minimalist approach and go the other way using one source, one amp and 2 speakers in stereo and see what kind of fidelity I can come up with. I would like to avoid using a sub and keep the speakers small enough to fit in say a medium sized office. I need to keep a bit of the emotion that a decent stereo system can generate. If i have to go with a small sub to achieve that because of the size limitation I have put on the mains I will......but i would rather avoid it. Experimentation will be required.
 
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