Old Jaycar speakers CW2108 - What to do with them

[konman]

Hey guys

I am aware this has been covered before in a previous post,

What to do with these drivers?

but unfortunately I am not too clear on the final application as I am pretty new to pro audio.

Ive built countless sealed sub enclosures for car applications, so my woodwooking skills are not too bad, but I have only grasped the theory of advanced box design for hifi. I have been reading this forum for a long time.

So... in my possession I have 8, yes.. 8 of these cw2108 jaycar drivers. I would like some advice on what enclosure design would best suit this speaker, possible volume and port sizes etc. I plan on using them for home theatre hifi and music (well obviously) mainly electronica like infected mushroom etc.

I plan on buying some soft dome tweeters from Altronics, as they are relatively cheap

[URL=http://www.altronics.com.au/index.asp?area=item&id=C3005A[/URL]
(hopefully not too nasty) but im mearly matching the quality of the woofers :-)

Anyhow, i was looking at this design
[URL=http://www.humblehomemadehifi.com/LBS.html[/URL]
i like the look so long as these woofers can handle a bass reflex design. I am not an audiophile by any means, but I do appreciate good overall sound from a system. PLus this box looks easy to make.

Oh and ill be attempting my own crossovers too..any quick advice on that would be great also

Any help is greatly appreciated

Kon

[Moondog55]

Hi Kon, unfortunately the links don't go to the tweeter you picked, BUT- most of those cheap Altronics tweeters have quite high resonant frequencies (Fs) and crossing to a 6inch should be done quite low.
8 midwoofers YES? so 4 in each box?

Have a quick read through Joe Rasmussens thread on the "Elsinores"

General rule of thumb is to cross the tweeter at least 1 1/2 octaves above Fs and 2 octaves is better.

Looking at my 2003 catalogue, that drive has a dip of about 6dB at 1K, and rolls off sharply at 3K, so a first order with a zobel at around 2.5/3K should work. but if you use a cheaper tweeter you'll probably need a third order XO high pass.

High Qts driver ( 0.558 ) but low Vas 15.2litres

Please note these are Jaycar specs and therefore fuzzy.

You can get a pair of tallish boxes using the full width of a 1220 sheet of chipboard or MDF with a total internal volume between 60 and 100 litres, and then stuff loosely with your choice of fill/ fibreglass or polyester

[PeteMcK]

I used the CW2108s paired with CW2142s as a 2.5 way in 50L cabs tuned to ~40Hz (I'm at work, so numbers are only ballpark...)

CW2108s - respond nicely up to ~4KHz and fall off rapidly, like a good polycone should; In fact I'm running these without any crossover parts on the CW2108s

at the low end Fs is higher than Jaycar's specs (surprise surprise) but they model well in an EBS alignment; downside is they can't handle low end power very well at all, but if you've got 4/side they may be OK, depending on how loud you play. Otherwise I think they're a good mid driver.

I'll look out my measurements tonight if I remember when I get home

pics & more details here:
Cheap 6.5" drivers

[Moondog55]

Peter is right if you want to cross over that high.
Alternatively, you could buy some decent cheap eight inch or ten inch woofers and possibly go 3-way, using the 6 as the mid-bass, or possibly a transmission line but I have no experience with that implementation.

Electronica does contain some serious synthesizer bass notes though, so the power handling down low probably isn't going to suit your particular needs.
High Qts such as those Jaycar drivers are usually used in either infinite baffle or TL speakers, but if Peter has had success with EBS ported alignments you can certainly try using a ported box

[PeteMcK]

my measurements:
Fs 52.6, Qe 0.65, Qm 5.96, Re 7.1, Vas 13.5 L, Sd 112 cm^2

[konman]

Thanks for you all your responses guys..

So from what Ive gathered, possibly getting an 8" driver would solve the lower frequency hole that these drivers have.

Now, please forgive me as im not as cluey as most of you guys on here,

so if I go for a 3 way system, as Moondog55 suggests, then will I need a zorbel filter arrangement just for the cw2108, and a normal 1st order crossover for both the woofer and tweeter? Or is a Zorbel style crossover the way to go for everything. I quickly read up these XO networks, so this is for smoothing out the resonate frequency of the particular driver and to keep the impedence curve constant?. What type of windows program can i use to work all this out..

Ive seen tables of data in which there are values of inductors and capacitors to marry up the crossover points. Is this the correct way in determining the crossover network?

Lets just say i go for two cw2108s in each cabinet, in a ported enclosure, (MTM ?) what would be the ideal volume of each enclosure, (these drivers are probably not meant for bass reflex) but could yield better bass response as compared to sealed.

Im sorry but I am a little over my head but i am willing to learn the details. Sorry for the torrent of questions.

From what ive read on here my knowledge level is at around 1/10

Thanks

[Moondog55]

That's OK as I'm probably only a 2/10 on that scale, very steep learning curve for me.

If you are talking about the mid-range cavity then a small sealed box is all you need for the CW2108, if it is being used as a mid-range.

3-way systems are harder to get right but offer better power handling, and IMO, a clearer mid-range.

While I like 8inch woofers, I usually use them in pairs, all I can say is for bass: bigger is better ;-)

Zobels ( also called conjugate circuits ) are used to flatten the impedance curve of the driver so that the components used in the XO work correctly, as you have surmised correctly.
Crossover slopes need to be worked out for each combination of drivers, there isn't a single rule that works for everyone with every combination of drivers.

Perhaps, as a general rule though , the louder and longer you play your music, the steeper the XO slopes need to be to protect the mid-range and tweeters from over excursion.

If this is your first speaker perhaps getting some chipboard and making a pair of sealed boxes of about 15 litres, using one of those cheaper Mylar tweeters, and just play with various XOs.

Use two binding posts on the box and make your crossovers on a big bit of peg-board outside of the box.

[Moondog55]

I'd suggest a well stuffed box with a target of 8L to 10L effective volume per driver, Qtc = 0.9 to 0.95, which should combine well An AV 80Hz filter, or a hifi first order bass filter.

That is from Sreten in response to Peters original query on these drivers.

So 3-way should be feasible using a single inductor of the right value if you can find a driver with a smooth roll-off, or as an alternative use a plate amp for the woofer and run as sub + mid/tweeter.

[PeteMcK]

Re:" need a zorbel filter arrangement just for the cw2108, and a normal 1st order crossover for both the woofer and tweeter? Or is a Zorbel style crossover the way to go for everything.
I quickly read up these XO networks, so this is for smoothing out the resonate frequency of the particular driver and to keep the impedence curve constant?. '
No, you don't need a zobel, and they aren't for smoothing out the resonant freq (that's a car audio myth...), The basics (You've got to understand the rules before you can break them :-)
http://sound.westhost.com/lr-passive.htm


"Ive seen tables of data in which there are values of inductors and capacitors to marry up the crossover points. Is this the correct way in determining the crossover network?" No, you need to use actual impedance values at your xover freq, calculators here will help:
http://ccs.exl.info/calc_cr.html#second


"Lets just say i go for two cw2108s in each cabinet, in a ported enclosure, (MTM ?) what would be the ideal volume of each enclosure, " - download Winisd and use that to figure it out:
http://www.linearteam.dk/default.aspx?pageid=winisdpro

'Sorry for the torrent of questions.' - don't be, ask heaps

[gainphile]

Hi Konman,

My idea would be to run thosw 8 drivers as OB, with 6.5" midrange.

Now, just in case you can't make up your mind... I'm happy to buy them