Building new speakers!

[FelixAUS]

Hi, sorry if this is in the wrong area of the forum, move around as you please =)

A few months ago I bought a set of home theatre speakers (8" splits) from a garage sale for $10, one worked the other didn't (Get what you pay for I spose).

I pulled my dad's old Luxman L-30 out of the garage and set the one up, sounded great (drivers are AKAI).

However since only one of them worked I went into Jaycar and bought two new drivers (http://www.jaycar.com.au/productView.asp?ID=CW2196).

They sound really good, except with the new driver's I have realised one of the speaker box's is stuffed and is letting air out somewhere it shouldn't as deep bass through them sounds disgusting (however the other box is beautiful).

So then that leads me to building new vented box's for them!,

I've been reading a lot of stuff on the internet about speaker box design's etc, but thought I should ask for a specific opinion given my case...
Okay here's the questions:


1. For the boxes MDF or Marine Grade Ply? 18mm? 22mm?
2. Should I stay with a 2 way setup? or is 3 way better? I could buy the 4" of the same speaker. (I listen to all sorts of music, but do love bass, so getting low dirty amounts would be good.. )
3. I have put it all into WINISD and it gives you a recommended box size and port length, gain, phase plot etc, what should I be looking for on those graphs? or any good websites to explain it all?
4. If I chose a 3 way setup, and given they are all 8 Ohm speakers, and my amp is a 2x50w (4 ohm) or 2x40w 8ohm, What would be the best way of wiring it? Would running a 3 way crossover in parrallel damage my amp (by dropping it to 2 ohm) or because it is a crossover is this not a problem?

Any help will be appreciated since I want to do a proper job and build some speakers that will last a long time!

If you need anymore info to help please ask
Cheers,

Felix.

[lowpoke]

Hi Felix,

I'm assuming the home theatre speakers you have comprise of two drivers, an 8" woofer and a tweeter? (The term 'splits' is a very Australian term and may not be understood by many of the forum members outside AU. I've only ever heard it used in car audio circles too.)

Anyway, this speaker enclosure contains a passive crossover? If so this crossover will have been designed specifically for the two Akai drivers. By swapping the woofer, unless it has exactly the same specs as the one it replaced, you may not get optimum results.

To be honest, the first thing I would do is simply repair the leaking enclosure. This way you can use your amp at 8 ohm. You said the one that works sounds good.

If you really want to build new speakers because you're up for a challenge, I would seriously recommend a tried and true design where somebody else has made all part selections and calculations for you. There are plenty of great examples on this website, or on the web in general. This way your results will be MUCH more predictable!

[FelixAUS]

Lowpoke, yes 8" driver and a tweeter (I've only ever had a bit of dealings in car audio )

Yes the current ones have a passive crossover and AKAI tweeter, which is one of the reasons I was thinking of starting from scratch (new tweeters, crossovers, and boxes).

In terms of fixing the box, that was my original thought, and it seems everything I have done just won’t fix it! I've even gone way overtop with screws, hot glue etc at every possible place where I suspect it is losing compression and it still puts out this nasty muddy sound! It’s not the drivers either since I have swapped them, and it’s not the amp. They also look a little less than average so I think I will start again...

Thanks for the tip about pre-tested designs, I will look into it!
Although considering I have already bought the new drivers wouldn't it be better taking the box specs out of WINISD?
I am using the downloaded one and that has calculated optimum enclosure and port size/length for my drivers. Should those measurements be correct?

Seeing as this is my first attempt at boxes should I stick to a 2 way speaker? or are the extra complications a 3 way that much more work?
I do want to do a good job which will hopefully last many years. I had my last exam today (YAY!) so time and resources for building boxes are not a problem as I have access to a tablesaw, timber, router, jigsaw etc so I dont mind putting in a lot of work if I get a fantastic speaker out of it!


Also any good audio websites which explain gain, phase plot curves etc would be appreciated! I have done pre-tertiary electronics and physics so I think it shouldn't be too hard to get and understanding of once I know the basics =)


Thanks again - really appreciated!

Felix

[PeteMcK]

Felix, I used these drivers 2/side in a 3-way, search this forum for details. IIRC, you'll need 24- 30 Litres per driver, & IMHO, these are really only suitable for use in a 3 way, they sound a bit nasty high up (I think I crossed them over ~ 400Hz 2nd order).
Sorry this is a bit breif, got do actually do some work today!!!

[sreten]

Hi,

See the links, sometimes you are lucky and the new drivers
work with the box and crossover, in that case repair the
duff box and count yourself lucky, otherwise start from
scratch, keep the AKAI boxes c/o and tweeter, with
some experience you may be able to find suitable,
i.e. very similar bass drivers, I have done this.

rgds, sreten.

http://sites.google.com/site/undefinition/diy
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
Click below to go to
Quarter Wavelength Loudspeaker Design
The Frugal-Horns Site -- High Performance, Low Cost DIY Horn Designs
Linkwitz Lab - Loudspeaker Design
Music and Design

[PeteMcK]

My build thread, note measured specs are quite different from Jaycar's:
Jaycar CW2196 8" woofer

some reading on crossovers:
Passive Crossover Network Design

[PeteMcK]

Looking up my old Unibox sims, I used 24L/ driver tuned to ~40Hz; If you want a smaller box, 18L @ 48 Hz looks good, 13L @ 50Hz is the point below which where there isn't quite enough low end for me...

[Moondog55]

Can we see pix of the dud boxes and drivers??
Have you checked all of the connections inside, I have been given "Broken" speakers before and once or twice he problem was simply a broken wire caused by dropping the box ( which also leads to air leaks etc)

[FelixAUS]

Originally Posted by PeteMcK

Looking up my old Unibox sims, I used 24L/ driver tuned to ~40Hz; If you want a smaller box, 18L @ 48 Hz looks good, 13L @ 50Hz is the point below which where there isn't quite enough low end for me...

Pete, thanks for your thread! So you would reccomend running these just for lows and buying a separate midrange? Maybe the 5" of the same style? The tweeter you used, is this the RSN1005 Piezo Tweeter?

In terms of box sizes WINISD "Optimum" is a 44L tuned to 35 Hz? Is this a little exessive then?


Sreten, thanks for those links, I will begin trawling through them today

Moondog I will post some pics up soon!

Cheers,

Felix.

[PeteMcK]

'So you would reccomend running these just for lows and buying a separate midrange?' yep; 'Maybe the 5" of the same style?' - No, this would be much better :5.5" - 4 Ohm - Ferrite - WF138WA02 - Soundlabs Group

'The tweeter you used, is this the RSN1005 Piezo Tweeter?' - well, it's the old Motorola version, pretty much the same I think

'In terms of box sizes WINISD "Optimum" is a 44L tuned to 35 Hz? Is this a little exessive then?' - yes, Jaycar's 'parameters' are notoriously dodgy. Mine will be closer, but these drivers need a few hours break-in before Fs settles down. FWIW, Unibox is a bit better than Winisd.