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Old 14th March 2011, 02:58 PM   #1
mrc6064 is offline mrc6064  Australia
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Default Combining 2 speakers together.

ok let me make this simple. i have 4, 3 way loudspeakers. they are rated 150watt 'MAX' RMS 8ohms @ 91DB. they arnt the best speakers in the world but they'll do for now. so basically wat i want to do is combine a each pair of speakers together as 1. each speaker has 1x 12inch woofer, 1x 5inch mid, 1x 1inch tweeter. i am going to make cabinets with 16mm MDF. my first thorts were to shove all the speakers in 1 cabinet. so having 2 crossovers, 2mids, 2 tweeters etc. and then running the speakers in parralel to my receiver. or is there another way?. i honestly dont know where to start. ive never built a speaker b4. i understand a little bit about ohms etc. but this will be my first build ever. should i go sealed? or ported?.

ok ive given alot of Questions there. hopefully someone can point me in the right direction or give me a good reply. ill upload a pic of my speakers. NOTE. i have 4 of these speakers. they owe me 300 for all 4. Click the image to open in full size.
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Old 14th March 2011, 10:07 PM   #2
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it would help a lot if you would tell why would you do this in the first place.
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Old 15th March 2011, 06:48 AM   #3
rabbitz is offline rabbitz  Australia
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Better off leaving them as 3-ways otherwise you could end up with a mess combining 2 sets of drivers.

If you really want to play with them in another box then you could:
1. Make a 3.5 way (TMWW) by using another 12" woofer (with a 3.9mH to 4.7mH inductor) in parallel to the existing crossover.
2. Make a 3 way (MTMW) using an extra mid.
3. Make a 3 way as above (MTMWW) but with dual woofers (a 3.5 way can also be done).
4. Make a 3 way (WMTMW).
5. Make a bipolar 3-way with same drivers front and back.

There are other options but gives you an idea. The impedance on all these would drop to half the value with drivers in parallel so would be around 4 ohm nominal and even less so you have to be sure the amp is able to drive the lower impedance loads.

All these except #1 would require extensive crossover redesign.
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Old 15th March 2011, 07:05 AM   #4
AEIOU is offline AEIOU  United States
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Why don't you just save yourself a lot of trouble and stack one loudspeaker on top of the other? With the upper one upside down.

You really don't have the slightest clue as to what you are doing, but go ahead and make a pair, have some fun, maybe you'll learn something.
Have you considered reading up, getting some books on the subject first?
If I had 4 loudspeakers like the one in your picture, I'd sell them all and use the proceeds to build something better. If you are really intent on building your own, I suggest you build from a kit or a published design.


Quote:
Originally Posted by mrc6064 View Post
ok let me make this simple. i have 4, 3 way loudspeakers. they are rated 150watt 'MAX' RMS 8ohms @ 91DB. they arnt the best speakers in the world but they'll do for now. so basically wat i want to do is combine a each pair of speakers together as 1. each speaker has 1x 12inch woofer, 1x 5inch mid, 1x 1inch tweeter. i am going to make cabinets with 16mm MDF. my first thorts were to shove all the speakers in 1 cabinet. so having 2 crossovers, 2mids, 2 tweeters etc. and then running the speakers in parralel to my receiver. or is there another way?. i honestly dont know where to start. ive never built a speaker b4. i understand a little bit about ohms etc. but this will be my first build ever. should i go sealed? or ported?
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Last edited by AEIOU; 15th March 2011 at 07:11 AM.
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Old 15th March 2011, 12:15 PM   #5
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Unless you can measure the speaker drivers or otherwise get their T/S parameters, you won't be able to make anything that is worth the time and hassle.

:)ensen.
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Old 15th March 2011, 11:04 PM   #6
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Some good, practical advice has been given, mrc6064. Only thing I would add...
If you don't think the speakers are that great as-is, why don't you focus on where they are lacking? If the low bass is absent, run them with a sub. If the midrange is dull, find a better driver that fits. If the highs aren't there, find a good pair of tweeters for replacement. This would be good experience without jumping into the deep end.
And to give my honest opinion, if those drivers don't sound good in the box they're in now, they probably won't sound better "doubled up" in another box.
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Old 15th March 2011, 11:14 PM   #7
AEIOU is offline AEIOU  United States
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Quote:
Originally Posted by sofaspud View Post
Some good, practical advice has been given, mrc6064. Only thing I would add...
If you don't think the speakers are that great as-is, why don't you focus on where they are lacking? If the low bass is absent, run them with a sub. If the midrange is dull, find a better driver that fits. If the highs aren't there, find a good pair of tweeters for replacement. This would be good experience without jumping into the deep end.
And to give my honest opinion, if those drivers don't sound good in the box they're in now, they probably won't sound better "doubled up" in another box.
Woofers that big will usually get you plenty of bass, albeit thick and muddy bass if not done properly.
More than likely the enclosures are lacking in that they look to be thin, flimsy and probably quite resonant. With that type of loudspeaker you usually don't get much in the way of a crossover either. I wouldn't be surprised if the crossover consisted of only cheap NP electrolytic capacitors (high pass) for the midrange and for the tweeter.

Last edited by AEIOU; 15th March 2011 at 11:17 PM.
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Old 15th March 2011, 11:23 PM   #8
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Ummm... thick muddy bass = absent bass in my book. Guess I should have made that clearer. But my point was that a lot of that muddiness and resonance could be alleviated using a sub (running just the higher frequencies to the 3-ways). I can't really comment on crossovers, just from an external pic. But I'd think the OP would gain more from better drivers than better capacitors. YMMV.
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Old 15th March 2011, 11:35 PM   #9
AEIOU is offline AEIOU  United States
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Quote:
Originally Posted by sofaspud View Post
Ummm... thick muddy bass = absent bass in my book. Guess I should have made that clearer. But my point was that a lot of that muddiness and resonance could be alleviated using a sub (running just the higher frequencies to the 3-ways). I can't really comment on crossovers, just from an external pic. But I'd think the OP would gain more from better drivers than better capacitors. YMMV.
My point about the crossovers is that I wouldn't be surprised if there was no low pass crossover (inductor) on the woofer and I kind of doubt that the midrange has been band passed properly either. But you never know until you open them up and take a look inside. I wouldn't just simply replace the capacitors, I'd redesign the crossovers completely.
With inexpensive loudspeakers you often get a large woofer more for looks more than for performance. If the woofer magnet is small then the enclosure shouldn't be ported, but they would still port the enclosure anyway, to provide plenty of additional (boomy) bass.
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Old 15th March 2011, 11:44 PM   #10
sreten is offline sreten  United Kingdom
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Hi,

Its a very bad idea for your first "build", your unlikely to improve anything.

FWIW its a fair bet the crossovers in those speakers are very minimal.

They are very likely designed like speakers were in the 60's and 70's.
(Find some details in Troels site, but note good drivers used, but e.g.
see the issues here http://www.troelsgravesen.dk/JBL_L100.htm ).

So what do you have ? Basically IMO two pairs of speakers of the type
favoured by amateur DJ's and the like. Pretty loud as a pair and a stacked
pair (the sensible option) they will go even louder if the amplifiers up to it.
The mid and treble level controls allow some sort of sensible balance* but
its very likely a very simple crossover causes all sorts of issues, and that
simply put the drivers are simply not very good quality in the first place.
(* might work best with only using the mid and treble from the stacked
inverted top speaker, i.e. turn the mid and treble from the bottom off.)

As home hifi speakers how loud they go is no good if they don't sound good.

For your first build go for something smaller, high value, and high quality.

A good big speaker is necessarily expensive, it simply can't be done cheaply,
FWIW this http://zaphaudio.com/SB12.3/ is essentially from another planet.

Lots of choices in the links below. Leave the above as is, is best.

rgds, sreten.

http://sites.google.com/site/undefinition/diy (see FAQs)
Zaph|Audio
FRD Consortium tools guide
RJB Audio Projects
Speaker Design Works
HTGuide Forum - A Guide to HTguide.com Completed Speaker Designs.
Humble Homemade Hifi
DIY Loudspeaker Projects Troels Gravesen
Quarter Wavelength Loudspeaker Design
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Last edited by sreten; 16th March 2011 at 12:03 AM.
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