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Multi-Way Conventional loudspeakers with crossovers

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Old 9th April 2008, 08:57 PM   #1
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Default First time advice

Hi, first post on the loudspeaker forum.

Just a quickie really, im right at the start of planning a pair of loudspeakers and before i invest too much money in books
(im going to need a few months desinging and reading 'd'appolito-testing loudspeakers' + 'loudspeaker design cookbook') id like some advise.
Ive never built speakers before, i have built amps and am on an a masters EE degree at moment so i have maths and a bit of audio experience on my side.

Id like to built a 2 way design with a 12" / 15" bass speaker (why that size you may ask..? just because id like to feel some deep bass for once!) and a good tweeter.

Is this reasonable?
will i likely be lacking mids?
is it a big step up to go with 3 way designs?
Cabinet will be nothing fancy, just a rectangle with a port probably.. i have little woodworking experience but access to a good workshop facility and experienced people!

p.s. my post is probably full of ignorance in this field, and i do apologise if ive said somthing really stupid already!
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Old 9th April 2008, 09:19 PM   #2
MaVo is offline MaVo  Germany
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Alot of 1 inch compression drivers can handle 1-20khz. If not so loud and with a sharp crossover, 500hz may be possible. So i think a 12-15 inch is a good mate for those. If you design the crossover and compression driver horn to match the on and off axis frequency response of the woofer so that you avoid sharp transitions between the two polar plots, a good integration should be possible. But i have to add, even a 15 inch could struggle with frequencies below 40hz or so, allways depending on listening volume. So maybe your next step will be the subwoofer forum
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Old 10th April 2008, 09:10 AM   #3
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Cheers Mavo,

compression drivers eh? all add that to my list of dome tweeter, ribbon, tweeter and horn tweeter and maybe a fullrange driver for highs and mids.
I guess bass below 30hz doesnt concern me, i know thats subwoofer domain and i dont think i really want one of those yet. Just a good full range set will do me nicely i reckon.

Much research to do!

Anyone else have comments?
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Old 11th April 2008, 04:14 PM   #4
sreten is offline sreten  United Kingdom
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Hi,

2-way 12" or 15" speakers are generally PA speakers that generally
play far too loud for a domestic environment and generally have no
real deep bass to speak of.
A "hi-fi" 12" or 15" for 2-way does not exist ......

The cabinet does need to be internally fancy unless you like colouration.

http://www.rjbaudio.com/Audiofiles/FRDtools.html
http://www.geocities.com/woove99/Spkrbldg/

http://www.zaphaudio.com/
http://www.rjbaudio.com/projects.html
http://www.troelsgravesen.dk/Diy_Lou...r_Projects.htm
http://www.humblehomemadehifi.com/
http://htguide.com/forum/forumdisplay.php4?f=39

/sreten.
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Old 11th April 2008, 05:29 PM   #5
MaVo is offline MaVo  Germany
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Well, i had something like gedlee's summa speakers in mind. They are probably not very hifi in the usual "little drivers with fancy membranes and esoteric descriptions" way. But they seem to be a good design using 15/1 inch drivers.

"Far too loud" allways depends on where you dial in your amplifier. Nothing wrong with a little headroom.
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Old 11th April 2008, 09:02 PM   #6
tomcat9 is offline tomcat9  United States
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Here is a 3 way design with the big woofers you wanted. I think these would do just about right.

http://www.partsexpress.com/projects...=MagnaCumLaude

t
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Old 11th April 2008, 10:36 PM   #7
ttan98 is offline ttan98  Australia
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Quote:
Originally posted by MaVo
Alot of 1 inch compression drivers can handle 1-20khz. If not so loud and with a sharp crossover, 500hz may be possible. So i think a 12-15 inch is a good mate for those. If you design the crossover and compression driver horn to match the on and off axis frequency response of the woofer so that you avoid sharp transitions between the two polar plots, a good integration should be possible. But i have to add, even a 15 inch could struggle with frequencies below 40hz or so, allways depending on listening volume. So maybe your next step will be the subwoofer forum
I use an moderately priced compr driver, B&C DE250($120 retail) recommend x-over around 1.6Khz(with notable audible differences at lower x-over), I use a horn which recom min x-over at 800Hz.

When I use the combo the min x-over I get is about 1.6-1.7KHz, you say 500Hz, highly unlikely for my combo, unless you want to spend big bucks on comp driver and horn/waveguide combo.
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Old 11th April 2008, 10:46 PM   #8
ttan98 is offline ttan98  Australia
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Quote:
Originally posted by sreten
Hi,

2-way 12" or 15" speakers are generally PA speakers that generally
play far too loud for a domestic environment and generally have no
real deep bass to speak of.
A "hi-fi" 12" or 15" for 2-way does not exist ......


/sreten.

I disagree, go to commercial Hi-FI system from Emerald Physics which received good response listeners, the CS2 model uses 1 compression driver and 2*15" woofer in open baffle configuration, TWW via digital x-over, x-over at 1Khz 4th order(not ideal I think).

For more details go to this site:
http://emeraldphysics.com/

I have built something similar and gets very good result. The bass goes low, flat to 40-45Hz.

cheers.
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Old 11th April 2008, 11:12 PM   #9
DougL is offline DougL  United States
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Good Discussion so far.

From my point of view, the compromises to create a 2 way conventional box speaker with a 12" or larger woofer are not something I would do.
The 1' dome tweeters that are used in 2 way speakers have minimum crossover frequencies varying between 2 kHz and 1.2 kHz, depending on the model, the crossover slope, the max SPL required and the amount of distortion desired.
Most Drivers over 8 inches are Subwoofers, not mid-woofers.
The major difference is a Subwoofer is optimized for long excursion, at the expense of high frequency response, due to the high inductance voice coil.

As I see it, you have 5 options:
1 Use drivers such as horns that will play lower.
2 Use an 8 inch (or smaller) woofer and 1" tweeter and add a subwoofer.
3 Use a wide-range driver and a 12" or larger woofer.
4 Build a 3 way.
5 Accept the lower SPL and High Distortion mid-range and build a 1" tweeter / 12" woofer.

The 10" woofer from the Dynaco A25 Was available from Seas until quite recently. Might be something you could work with.

Here is a design with a wide range that might appeal to you.
http://www.quarter-wave.com/OBs/OB_Design.pdf

By the way, 3 way passive designs are generally considered more challenging for a beginner.

Good luck on your studies.

Doug
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Old 12th April 2008, 12:10 PM   #10
MaVo is offline MaVo  Germany
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I use this driver: http://www.bmspro.info/index.php?sho...10278&id=54364

With a big enough horn and in a not-pro environment, it could do 500hz. Obviously you need a crossover with at least 4th order slope, better higher. You can drive it with 80 watts using a 1000hz xo, reaching 132db of output. You can easily lower the xo point somewhat if you do not push 80W into it. Since noone needs 132db at home, this does work.

Also, the normal 12 or 15 inch pro driver is designed to work up to 1000hz. No problem at all. Overall, you get a high sensitivity, high maxspl, high directivity, low distortion system, which will work in multiple environments ranging from simple homelistening, to monitoring, even small partys can be done.
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