Parallel driver interaction in a 4-way system.

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#141
jupiterjune said:


Excuse me for being not negative, but this will be very easy to do.
Click to expand...

😀


Good work and a quick question – the merits of sealed boxes for the woofers vs ported.
It seems that getting four 8 ohm 8” woofers to work to specification in a reasonably sized sealed box may not be so easy.
I would be willing to go as large (for the complete WWWWMTM speaker) as 300mm(W), 500mm(D), 1500mm(H).

Still a problem?

I’ve been looking at a few 8” woofers and I’ve noticed that the better performing and more expensive units have much higher Vas figures, but pretty reasonable recommended ported enclosure sizes.

Cheers,
Glen
 
#143
quasi said:
Hi Glen,

Somewhere I have an project article by ETI (or is it EA?) for a 4 way system. I think the thing was only rated for a 100 watts or so using now outdated drivers but the crossover details could be interesting.

Let me know if you have it otherwise I'm happy to find, scan and email it to you.

Cheers
Quasi
Click to expand...


Hi Quasi.

I've got that magazine too! Designed by David Tilbrook, it used Philips drivers and was part of the 4000 series of HiFi components. I also have a later mag which featured a cheaper 3-way version.

It was infact that very 4-way design article that got me started on 4-way speakers with this thread - it made going 4-way look like a really straight forward procedure.

Cheers,
Glen
 
#144
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Good service and prices are not outrageous, good discount for bulk (50+ )
http://www.soundlabsgroup.com.au/p/V-9041-W300S/W+300+S+-+8+Ohm
4 of these in parallel would give good power handling and good SPL, Q is a little high for closed box tho, James also has a nice 6inch mid bass
http://www.soundlabsgroup.com.au/p/V-1307-AL170A/AL+170+A+-+8+Ohm
but this still isn't the four-way you first asked about, but if you went WW-M-D-T-M-WW
where D= 2inch dome but the height of the tweeter is then a lttle far off seated ear height.
I like 4 ways, I just can't design them, 3-ways are hard, 4-ways are 4 times harder, and if you use cascaded topology for baffle step then DCR and associated impedance rises
 
#146
Eva said:


...

The multi-way loudspeaker of the future has several amplifier channels built in and all what it takes to produce sound is a line level signal and mains power.
Click to expand...

I'm off topic now, but if the typical AV amp is any indication, the above statement certainly isn't true. I think far more likely would be a rack of mono amps, each with its own power supply, carefully selected for the appropriate power, and combined together to create the multi-channel sections.

Most AV amps are quite atrocious musically. In a recent test, or so I heard second hand, a popular 100watt per channel AV amp was tested with two channels driven hard, and it mostly lived up to its power rating...mostly. But when all channels were driven hard, the power fell to 30watts per channel. (Again, overheard in a discussion, I didn't actually read the test.)

And that, is the very thing we are trying to avoid. That is why you want discrete high current amps.

Ask yourself why they can put 5 or 7 100 watt channels in an amp, and charge the same or less than an equal power rated stereo amp? It's because they are counting on you never needing all that power on all the channels at the same time. Because if you do need it, those AV amps aren't going to be able to deliver it.

Even now, those who do use active crossovers, are likely to use a combination of several discrete stereo amps, or a bank of mono-block amps.

No one that I ever heard of would consider using an AV amp for such a purpose. Or perhaps I should say an 'AV quality' amp since AV amps channels are not available for general use; but are dedicated to specific AV purposes. But none the less my point still stands.

I think active crossover loudspeaker of the future, and even of the present, are far more likely to use banks of discrete amps, than to use an all-in-one multi-channel amp.

An all-in-one multi-channel amp must supply everything from a single power supply, or most likely that's how it would be in a commercial consumer amps, and in my view, that just won't cut it.

However, if some one could conceive of and build such an amp with at least SIX high powered multi-channels built-in with fully adjustable active crossover, it would likely be out of the reach of 90% of consumers. Actually, more like 99%, but I want to be conservative about it.

If I can twist this back on topic, there is a real market for high current amps. There are several commercially available that are more than capable of sustained 1 ohm loads. They're not cheap though, and they are certainly WAY out of my price range.

So, this amp under discussion is actually a pretty common amp, though I think Glen took it to an extreme as something of an engineering challenge. Now that he has this high current amp, it only makes sense to use it.

We are...he is... now trying to find the best way to use what he has. And, he does seem to be narrowing it down nicely.

As a general point of interest, your ideas are good. But, as to solving the problem at hand, telling him he should have built a different amp, isn't really helping.

Though, to be fair, many of your comments were positive and helpful.

Hope that wasn't a little too personal.

Steve/bluewizard
 
#147
Moondog55 said:
Try modelling these if 8 inch will do

http://www.soundlabsgroup.com.au/p/V-1340-TIW200XS/TIW+200+XS+-+8+Ohm

4 in parallel will give an extra 6 db, speciffically for small sealed box WW-M-T-M-WW
1500mm is a little small/short 1800 would place the tweeter in the centre at seated ear height
Click to expand...


Thanks for the info and the links! I've been pretty much scared away completely from a 4-way now. I'm also off the Di Apolito (or whatever it's called) arrangement.

Four 8 ohm 8" woofers WWWW with either a MT or a MTM top seems to be a nice straight forward way to go.

Suppose I have an enclosure for the four woofers 0.9 m high.
My seated ear height is ~1.2m. So with either an MT or an MTM on top, the tweeter height would be pretty much right.

That 8" woofer is much better than some others I've looked at. Supposing that it is not too sensitive, if used my speaker box would only need to be ~0.4m deep for the required 100L volume. Very manageable 🙂

I reckon I'd be satisfied with the bass output of such an arrangement.

Cheers,
Glen
 
#148
one of the 6inch mids would be plenty I think, but pick a tweeter that can be "happy" working from 2500 and up.
Be mindful of the fact that I haven't used Visaton drivers myself, I'm only going on third-party recomendations, I like big drivers myself, somehow they sound more natural and realistic when reproducing bass.
I like the directional characteristics of D'Appolitto and it usually adds 3dB for the extra woofer/mid which is ALWAYS useful.
At $99- those 6inch Visaton did look like value for money and the cone break-up should be easy to control ( but don't ask me I use active because passive x-overs are SO HARD )
 
#150
I've been thinking, HURTS!!! but if I was building this tower I'd only use 3 of the Visaton 8 inch; power handling would still be adequate, still gain 6dB to bring them up to the level of the mid-bass and it's a nominal 8/3 load which would place much less stress on your amp.
I followed the thread and while I know you are confident in your predictions and the amps capability the specs of most solid state amps are simply cleaner into higher loads.
Just ran some numbers;
2.8R nominal
100 litre box
Fc 44hz F3 44Hz F6 34Hz
113dB at 200 watts and run out of excursion
125 litre box
( 100 plus fibre glass and polyfill )
Fc 41.8Hz F3 41.8Hz F6 32Hz 113 dB
again 200 watts and you run out of excursion these drivers are just not efficient but that is seriously loud
 
#151
Moondog55 said:
I've been thinking, HURTS!!! but if I was building this tower I'd only use 3 of the Visaton 8 inch; power handling would still be adequate, still gain 6dB to bring them up to the level of the mid-bass and it's a nominal 8/3 load which would place much less stress on your amp.
I followed the thread and while I know you are confident in your predictions and the amps capability the specs of most solid state amps are simply cleaner into higher loads.
Just ran some numbers;
2.8R nominal
100 litre box
Fc 44hz F3 44Hz F6 34Hz
113dB at 200 watts and run out of excursion
125 litre box
( 100 plus fibre glass and polyfill )
Fc 41.8Hz F3 41.8Hz F6 32Hz 113 dB
again 200 watts and you run out of excursion these drivers are just not efficient but that is seriously loud
Click to expand...


Nah, I still like the idea of four of ‘em better. A crazy amp needs crazy speakers 🙂


BlueWizard said:
So, this amp under discussion is actually a pretty common amp, though I think Glen took it to an extreme as something of an engineering challenge.
Click to expand...


Pretty much. For this highly versatile toy (just think of all the parallel combinations I'll be able to play with, with as many assorted speakers as I can convince others to lend me) dedication to a single pair of speakers is not something I'm remotely interested in.

BTW, just zipped out for some Thursday evening late night shopping. Picked up some bed time reading material to supplement my insomnia. Contains "Everything you need to know...." 🙂

Cheers,
Glen
 

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#153
OK CRAZY SPEAKER COMING UP, make the box a little bigger, about 275 litres, just make it deeper ( Any how it should be deeper than it is wide ) use 6 of these wired in groups of 2, thats going to increase Q because of the series resistance which will let it go a little lower, but it will still run out of steam at 116dB but the F6 is 1.5Hz lower and make it WWWMTMWWW add 4 more woofers and another pair of midrange drivers firing to the rear (di-pole)at 1800mm high thats not a statement it's a declaration of war
 
#154
G.Kleinschmidt said:


😀


Good work and a quick question – the merits of sealed boxes for the woofers vs ported.
It seems that getting four 8 ohm 8” woofers to work to specification in a reasonably sized sealed box may not be so easy.
I would be willing to go as large (for the complete WWWWMTM speaker) as 300mm(W), 500mm(D), 1500mm(H).

Still a problem?

I’ve been looking at a few 8” woofers and I’ve noticed that the better performing and more expensive units have much higher Vas figures, but pretty reasonable recommended ported enclosure sizes.

Cheers,
Glen
Click to expand...


Hi,

Vented versus sealed ?

a) Maximum output of a vented box near the port frequency
is equivalent to four sealed identical drivers.

b) Assuming the port is tuned low output in the higher bass
is similar to a sealed box.

c) A vented box is nearly always ~ twice the size of sealed box.
i.e. you could use two sealed drivers in the same box.

d) Drivers with ideal parameters for sealed are : High Vas,
low Fs, low Qts. What really matters is cone mass and the
magnet system. Box volume dominates over Vas, setting
Fbox and Qbox.

e) Drivers with ideal parameters for vented are different.
Vented boxes overload rapidly below the port frequency.
Due to the vent Vbox has no effect so sub port rejection
depends on Vas only, consequently very high Vas and
low Fs is not ideal. Box volume should still be the major
control of the alignment but you want Vas to be around
2 to 3 times larger than the box.
For sealed Vas can be many times larger.

f) For a well designed driver the major cause if distortion
in the bass is suspension non-linearity and they are all
non-linear. Poor ones are also assymetric. Vbox vs. Vas
linearises the behaviour, Vbox approaching Vas or in
some cases I've seen Vbox > Vas is not good practise.

g) Vented boxes are much more efficient (upto 6 to 10dB)
than sealed at low frequencies, this only really matters
with valve amplifiers.


So we are talking up to a foot wide, 5ft tall (?), 1+2/3ft deep.
Assuming 1" walls this gives ~ 6 cuft / ~ 170L.

For a domestic hifi speaker a bit of a monster ......
Why so big ? efficiency ? bass extension ?
(Needs to be that big for 4 8" drivers .........)

🙂/sreten.
 
#155
Hi,

some further notes :

JJ's simple simulations show a 3-way with the BSC in the bass section.
My example shows a 3-way with the BSC in the MTM.

These are two extremes and there is a whole family of possibilities
in between which is why 3-way design is so complicated.

The difference between the two extreme approaches is 4 to 6dB sensistivity.
The higher approach requires bass/mid drivers for the bass section.
The lower approach requires bass drivers more like subwoofers.

Depending on the bass / mid crossover point and BSC implementation
the midband senstivity can be set to any point between the extremes.

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

At some point you are going to have to get your head round.

🙂/sreten.

4 drivers in parallel = +12dB sensitivity (not 6dB).

http://www.zaphaudio.com/
http://www.rjbaudio.com/projects.html
http://www.troelsgravesen.dk/Diy_Loudspeaker_Projects.htm
http://www.humblehomemadehifi.com/
http://htguide.com/forum/forumdisplay.php4?f=39
 
#159
G.Kleinschmidt said:


BTW, just zipped out for some Thursday evening late night shopping.
Picked up some bed time reading material to supplement my insomnia.
Contains "Everything you need to know...."

Glen
Click to expand...

Hi,

FWIW judging by some of the posts inspired by that tome it also
contains a great deal of "what you do not need to know". That
is, stuff that is good to understand but if you do understand it
properly you also understand it is not the way to do it.

🙂/sreten.
 
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