14 replies to this topic

[Bon]

i'm planning on building a set of 3 way tower speakers for my room (i know not car related, hopefully someone can help anyway ), but i don't know what i should do about the crossovers.
i'm thinking of using an 8inch woofer with a set of 6.5 inch splits for the mid and tweeter.
i was going to use a jaycar crossover with xover points at 800hz (LP) and 5000hz (HP), but was told it may not sound as good as if i built my own. i haven't built xovers before so i'd like to aviod this.
the speakers i planned to use were these:
http://www.soundlabsgroup.com.au/pc/V-4720/Visaton-8/Sound (woofer)
http://tinyurl.com/zsr9v (mid/tweeter)
before you knock the prosonics, i have a set of their lower market ones and they sound great. i like mostly rock AC/DC type stuff, and they play it really well, so i thought the competition ones would be even better. what xover points do you think suit these speakers? would 800/5000hz be good for it (i can't tell i'm new to this) or would something more like 1200/5000hz be better? should i look at different speakers?

i thought of using the standard prosonic crossover like this, adding an inline LP filter for the 8in woofer.
i don't know if this would overload it though or sound off.
i will be running them off a home theatre amp, so they need to provide a 6-8ohm load. how can i wire up the 4ohm drivers to do this? i think i heard if they are in series it doubles the ohms, parallel halves it.
how can i do that and wire them up to the xover? if someone could find or make me a wiring diagram that would be much appreciated.

thanks in advance

[~thematt~]

A few comments by myself, then Ill leave the floor for someone more experienced. The diagram you have shown wont be effective, and no-one can really comment on the Xover points either. The problem is, crossovers are designed around the speakers and their characteristics. A Xover point takes into account the drivers natural roll-off, how and where the smoothest frequency response is, and how compatible it is with the other drivers.

For a three-way, the woofer and the mid both need to be bandpassed. In your picture, only your woofer is. Which means your mid and your woofer will both be playing the same frequencies up until the woofer slopes off. This gives two point sources of sound, which can ruin your imaging and staging, as well as sound rightfully dreadful if you dont manage to mate your speakers perfectly. Also, a 6.5" of that calibre wont be able to reproduce the mids very well, as its more of a midbass itself. You should be looking more around the 3 to 4" range.

Honestly, there arent many people around that can build a good passive. You would be best either choosing an active setup, which would still be difficult but allows you to have all the fiddle factor you need to perfect the sound yourself, or simply getting a 3-way set with a factory Xover.

If you are not careful, and in this case very careful, you can ultimately make everything sound very bad indeed. Just my two cents though!!

Also, in your case, you need to get home stereo speakers rated at 6-8ohms. Car and home stereo speakers are built differently given their different applications, and putting car speakers inside a house, in an environment it isnt designed for, just isnt doing it justice. Some people have managed to incorporate home speakers in their cars, but these people are highly skilled and know what they are doing and how to compensate.

Hopefully someone else can shed a bit more light er?

[gooki]

Don't use crossovers, wire all the drivers together and use appropraite sized caps wired in series with the mid and tweet to create the correct 6db/octave filter.

[Bon]

~thematt~ said:

For a three-way, the woofer and the mid both need to be bandpassed. In your picture, only your woofer is. Which means your mid and your woofer will both be playing the same frequencies up until the woofer slopes off. This gives two point sources of sound, which can ruin your imaging and staging, as well as sound rightfully dreadful if you dont manage to mate your speakers perfectly. Also, a 6.5" of that calibre wont be able to reproduce the mids very well, as its more of a midbass itself. You should be looking more around the 3 to 4" range.
Honestly, there arent many people around that can build a good passive. You would be best either choosing an active setup, which would still be difficult but allows you to have all the fiddle factor you need to perfect the sound yourself, or simply getting a 3-way set with a factory Xover.
If you are not careful, and in this case very careful, you can ultimately make everything sound very bad indeed. Just my two cents though!!
Also, in your case, you need to get home stereo speakers rated at 6-8ohms. Car and home stereo speakers are built differently given their different applications, and putting car speakers inside a house, in an environment it isnt designed for, just isnt doing it justice. Some people have managed to incorporate home speakers in their cars, but these people are highly skilled and know what they are doing and how to compensate.

so doing it like the pic means it would be like having a <800hz lowpass on the woofer, but no >800hz highpass at the same point for the mid? would a 3 way crossover have this kind of setup built in?

how would i build an active setup? am i right in saying thats when you split this signal before the amp?

i was told by another person on this site that there isn't a huge difference in car or home low priced drivers, it only matters when you get to the high end stuff.

gooki, would it sound as good as using a properly built xover? i'd imagine if its all in line the tweeter would have a bit of delay, right?

what are the xover points set at on an average home stereo 3 way system? obviously they wont be exactly the same, but are they close?

[ProClass]

Right, home audio XO point are very different than those used in a car.
Most common XO points in home speakers are
3000Hz high pass to the tweeter
250HZ to 300HZ high pass and a 3000Hz low-pass for the mid
250Hz to 300Hz low-pass for the woofer.
As Matt said, it is very critical to know the speakers T/S specs to build a proper crossover for your speakers.
{In anser to your question abou tmid woofer wiring, no both the woofer and the mid would be playing the same frequency range.}
I strongly suggest a minimum of 12DB slope for the tweeter but prefer 18DB slopes.
You can get away with a 12DB for the mid and in home audio a 6DB for the woofer oftne works very well.
I can not stress enough that building a passive net wrong can cosue serious damage to tweeters and possibly damage your home amp.
If possible, post the T/S specs for your tweeter, mid and woofer and I can post the components you need based on simple XO point selection.
I will be starting a detailed thread on XO design and application very soon. Perhaps you can wait til that thread starts. It will be in the General Audio section.
Cheers
Andreas

[Pulse-R]

I would have thought 5kHz for the tweeter, 800Hz for the mid and sub-sonic ~30Hz for the woofer (<8").

[Juls]

Considering the midbass is 6.5"

I'd use something like
2-4khz mid/tweet
150-300hz Woofer/Mid

Keep in mind the midrange needs to be bandpassed IE bass and treble cut off.

Make Sure you build a separate enclosure in the box for the midrange,

a 12DB per Octave Crossover in 3 way shouldn't be too hard to achieve,
just remember to wire the outgoing speakers Out of Phase. (since a 12db octave crossover will put the speakers 180 deg out of phase)

Regards
Juls

[Bon]

i emailed the guy who owns the site (sound labs group) and he said an off the shelf XO should be fine for the speakers i was looking at. the XO i found was a jaycar one with XO points at 700hz and 3.5khz, and the speakers i'm getting are now going to be other soundlab group ones.
i found an 8in woofer, 5in mid and 1in tweeter that would suit the 8ohm load i need.

[Bon]

if i was to use a 4ohm woofer, then 8ohm mid and tweeter (or alternatively 8ohm woofer and 4ohm mid/tweet) what load would it provide to the amp?

also, is 700hz to high a XO point for a woofer? i saw a graph that said this was in the midrange somewhere.

[Pulse-R]

unless your midbass (6.5") is pointing almost toward you (on-axis) then I'd avoid going much over 450Hz, or you will notice a muffled sound from the side closest to you.

[Bon]

why will it make a muffled sound?

the woofers will be angled upwards, tweeters neutral at about ear level and the mids will be pointed down.
like this: http://img160.images...kersdone2ee.jpg
they'll be on stands, so all the speakers point approximately at ear level.

woops. link didn't work.
here's the url for the pic:
http://img160.imageshack.us/my.php?image=speakersdone2ee.jpg

[ProClass]

Right
First the cabinet design.
There are a few reasons to use this design. First we will deal with phase.
The source of all sound is at the voice coil.
I am about to discuss this in the passive XO design thread.
What the design is trying to do is align the voice coils vertically. The science is called, Acoustic Summations, The speakers acoustic centre and ZDP of zero delay plane. This concept is often discussed as Group Delay. I’ll cover the details of this in the passive thread soon.
Second, of axis response in woofers is almost always smoother a response curve at lower frequencies. For me I like slightly off axis response below tweeter frequencies. The tweeter, I like them on axis.
Now, crossover points! Under no circumstance would I suggest an off the shelf passive net. There are simply far to many variables to suggest any one point. If can post as much of the T/S param’s for each speaker, enclosure volumes and I will model it for you and then I can provide accurate information. Having said that, I might pick a 3K and 250 for starting points. Keeping the lower XO point 300 with ensure the mid range image come from only one speaker. Remember no stereo effect below 300Hz.
Cheers
PM me when you post please.

[Bon]

i'm going to sound like a twat now. i don't know what T/S specs are to begin with
i have the spec sheets of the speakers i'll probably use though (now 6.5in woof, 5in mid and 1in tweet)

WOOFER:
Specifications:-
Nom impedance: 8ohms
Power handling: 80 watts RMS
Freq range: 39Hz - 3000Hz
Sensitivity: 87dB 1watt 1metre
Voice Coil Resistance (Re): 6.9ohms.
Resonant frequency (fs): 39Hz
Mechanical Q factor (Qms): 6.027
Electrical Q factor (Qes): 0.466
Total Q factor (Qts): 0.433
Equivalent Volume (Vas): 20.9Lt
Cone Area (square metres): 0.0133. 
 Typical Applications:  
Vented Box.- Box volume (litres): 26Lt
Tuning Freq (Hz): 37Hz- -3db Frequency (Hz): 35Hz
 Two Vent Options
Vent dia: 50mm Length: 133.75mm
Vent dia: 66mm Length: 239.25mm
 Inside Cabinet Dimensions W 237mm; D 297mm; H 378mm
 Sealed Box- Box Volume (litres): 10Lt
Tuning Freq (Hz): 68.56- -3db Freq (Hz): 64.09 Qtc: 0.76 
Inside Cabinet Dimensions. W 220mm; D 175mm; H 278mm

MIDRANGE:
Technical Data:
Rated power 40 Watt
Maximum power 60 Watt
Nominal impedance 8 Ohm
Frequency response (-10 dB) fu - 12000 Hz
(fu: Lower cut-off frequency depending on cabinet) .
Mean sound pressure level 86 dB (1W/1m)
Maximum cone displacement 15 mm
Resonance frequency fs 83 Hz
Magnetic induction 1 Tesla
Magnetic flux 250 µ Weber
Height of front pole-plate 4 mm
Voice coil diameter 2 cm
Height of winding 0,55 cm
Cutout diameter 11,3 cm
Net weight 0,34 kg
D.C. resistance Rdc 7,7 Ohm
Mechanical Q factor Qms 3,52
Electrical Q factor Qes 1,56
Total Q factor Qts 1,08
Equivalent volume Vas 7,4 l
Effective piston area Sd 86,5 cm2
Dynamically moved mass Mms 5,1 g
Force factor Bxl 3,6 T · m
Inductance of the voice coil L 0,75 mH

TWEETER:
Technical Data:
Nominal power handling with high pass 50 Watt (12 dB/Okt.; 3000 Hz)
Peak power handling with high pass 80 Watt (12 dB/Okt.; 3000 Hz)
Nominal impedance 8 Ohm
Frequency response (-10 dB) 1000 - 20000 Hz
Mean sound pressure level 90 dB (1W/1m)
Resonance frequency fs 1500 Hz
Magnetic induction 1,3 Tesla
Magnetic flux 210 µ Weber
Voice coil diameter 2,5 cm
Cutout diameter 8,5 cm
Net weight 0,55 kg
D.C. resistance Rdc 6,9 Ohm
Effective piston area Sd 5 cm2
Dynamically moved mass Mms 0,1 g
Inductance of the voice coil L 0,04 mH

hope that helps.

[~thematt~]

They ARE the T/S parameters mate

[ProClass]

I'll model this over the weekend and post back.
Cheers