Parallel driver interaction in a 4-way system.

[GK]

G’day.

In the not too distant future I’m going to have up and running an amplifier that can deliver huge amounts of power into a very low impedance.

I’m going to need a pair of HiFi speakers to go with it. I have elected to build a fully sealed 4-way 12db/ octave system starting with a 12” woofer.

However, in order to handle the power output of my amp, I’m going to need parallel drivers – two in parallel for each frequency band should do just fine and dandy.

My knowledge on speaker building is rather limited and I have yet to pick up and read a good text on the topic, so I’m just throwing around ideas at the moment with respect to cabinet design and driver placement.

Attached below is a pic showing a few ideas. Shown at A is a conventional 4-way, with B,C and D being different layouts for twin parallel drivers. I’m going for D at the moment mostly because it would look really cool and the box isn’t too high.

What I basically want to know at this stage is if I am heading in the right direction or if there are any problems with interaction between parallel drivers, which would make these deviations from the conventional 4-way either a failure or waste of time.

Cheers,
Glen

 

[tinitus]

"A" is the only one that makes sense, but I would "limit" to 3way, its hard enough

With your designs there is a bit of issue with the listening-height

 

[tinitus]

Or like this

 

[GK]

Or like this

Ok, but that's not too far away from my "D". I still want to do a 4 way though. I like a challenge.

Why the offset of the smaller drivers?

Cheers,
Glen

 

[GK]

G’day.
I’m going to need a pair of HiFi speakers to go with it. I have elected to build a fully sealed 4-way 12db/ octave system starting with a 12” woofer.

Edit: I meant 6dB (1st order) crossovers. The 4 drivers I'm looking at have plenty of overlap.

Cheers,
Glen

 

[sumsound]

Making a two way behave nice with 1st order is not so easy,

Trying to to a 4 way is going to be rough.

Having even (linear) amplitude response is going do be difficult.

You would need some sophisticated measuring tools, and prediction programs.

You will probably have issues with the Voice coils of the drivers interacting with the capacitors, and causing resonances that, maybe a zoeble, on the driver will help.

Making a good passive xover, requires more than the basic math to make the circuits. There is no 1 size fits all passive xover, technique.

Normally Multiple tweeters is a bad thing, as they will interfere with each other, and cause a lot of comb filtering.

With most decent drivers you should be OK running 2X RMS if you don't clip your amps.

I have a question:

Do 1st order filters actually sound good? Theres so much overlap, I would imagine a lot of smearing, and overworking of smaller drivers.

Anyhow Go for it if you think you got what it takes. I would go all active xovers and use multiple amps.

 

[sumsound]

Oh PS

I think a Diapollito greater than a 2 way is not normally advised.

Too many xover lobes/nulls.

 

[BlueWizard]

Let's establish an easy and common convention for discussion speaker designs. W=woofer, M=Midrange, and T=tweeter.

Next there are 2-way and 3-way systems, but there are also half-way systems as in 2.5-way and 3.5-way.

MTM is a common design in which the M stands more for MidBass than just Midrange.

WMTMW is also common and is similar to the Tinitus's design in post #3.

WWMTM is also popular and is similar to the Tinitus's design in post #2.

There are also WWMT designs in which the two 'W' are either running in direct parallel (a 3-way system), or are running in a 1.5 setup where you have one full time bass and one low bass. In a sense, the 1.5 is like a 3-way with a built in Subwoofer. So, actually, the last example would be referred to as a 3.5-way system.

Look at this design -

http://www.zaphaudio.com/ZDT3.5.html

This is extremely popular right now and many people have produced it with good results.

If you are willing to go with one of these more conventional designs, you can get complete design plans for free from the many speaker building sites on the Internet; Zaph Audio being one of the best.

This is built around the reasonably affordable Dayton Reference series, and the crossovers are all designed down to the last detail (and a lot of details it is).

As much as you want to do the design yourself, it is far more difficult than you can imagine, especially for what will end up being sophisticated speakers.

Look at the designs at -

Zaph Audio -
http://www.zaphaudio.com/

Humble homemade HiFi -
http://www.humblehomemadehifi.com/

Troel Gravesen -
http://www.troelsgravesen.dk/Diy_Loudspeaker_Projects.htm

Zilla Speakers -
http://www.zillaspeak.com/zillaspeakspeakers.asp

I know there are many others, but I don't have them bookmark.

Once place I do know with a wide assortment of proven designs is -

HT Guide - Mission Possible DIY (for discussions)
http://htguide.com/forum/forumdisplay.php4?f=6

HT Guide - Mission Accomplished (for completed projects)
http://htguide.com/forum/forumdisplay.php4?f=39

Pay attention to the -

- Dayton RS WMTW Center & TMWW Mains
http://htguide.com/forum/showthread.php4?t=15323

- DA Khanspire - An RS150/225 WMTMW
http://htguide.com/forum/showthread.php4?t=26309

Here is a link to a final Dayton WWMTM tower design -

- http://htguide.com/forum/showpost.php4?p=203855&postcount=537

Those are somewhat similar to what you propose. Also, don't be intimidated by the exceptionally long threads, as some point, usually near the top, the final design is posted - box dimensions, crossover schematic, and frequently photos of the crossovers and completed designs. Also, frequently complete parts lists with prices

I know how strong the urge is to conceive of a pair of speakers and build them, and if you want some economy speakers, you can throw them together a little easier. But, if you want some good speakers you can be proud of, copy an existing and proven design. Especially for a system as complex as you've conceived.

If you search the internet for the Zaph ZDT3.5, you will probably find links to several forums (including this one) where people have done a spectacular job of reproducing this system.

A good 4-way system is difficult, especially the crossovers, but a 2.5-way or 3.5-way system is easier, with fewer complication, and both are popular proven designs with several choices to pick from.

I don't want to be discouraging, but if you are just starting out, it is much too big a job to tackle without help, and the best help is a proven design. Then with each subsequent design you make, you will become better and more informed, and able to take on more of the task yourself.

I know that's not what you want to hear, but if you want good results your first time out, then you need to do it this way.

The next important thing is your budget, even if this is still just in the fantasy stage. If it is $100 to $300, that requires a completely different approach, than if your budget is $500 to $1,000, which in turn is completely different if your budget is over $1,000.

Generally, the lower you budget, the simpler and more uncomplicated the design can be, but also, the more limited the results will be.

Does any of this help?

Steve/bluewizard

 

[GK]

Thanks for the replies!

WMTMW is also common and is similar to the Tinitus's design in post #3.

OK, this is along the lines of what I wanted to know.
If the 3-way WMTMW arrangement is common and works well in proven designs, then is there any theoretical reason why a W-M1-M2-T-M2-M1-W would not also work well in an appropriately engineered 4-way system?

Since two tweeters are bad due to interaction, I guess I can use a high power / high sensitivity horn tweeter to compensate???

Cheers,
Glen

 

[sumsound]

Thanks for the replies!





OK, this is along the lines of what I wanted to know.
If the 3-way WMTMW arrangement is common and works well in proven designs, then is there any theoretical reason why a W-M1-M2-T-M2-M1-W would not also work well in an appropriately engineered 4-way system?

Since two tweeters is bad due to interaction, I guess a can use a high power / high sensitivity horn tweeter to compensate???

Cheers,
Glen

Major Polar issues, depending on where you cross over, as well as inherent polar issues from Xover lobes in a (Hyper Di Apolito?).

 

[GK]

Major Polar issues, depending on where you cross over, as well as inherent polar issues from Xover lobes in a (Hyper Di Apolito?).

Ok, but how "major" are these polar issues and how "major" are they in a 3-way version, which seems to have some degree of popularity?

BTW, I'm not in the least bit fazed at attempting a 4-way. If in the end it doesn't work to satisfaction, I'll just scrap the cheap MDF prototype box, either flog the excess drivers off on ebay or keep them for a future project, and then attempt a 3 way. 🙂

Cheers,
Glen

 

[Brett]

I guess I can use a high power / high sensitivity horn tweeter to compensate???

Most are not rated all that high. 150W is about the biggest and the better sounding ones, typically a lot less.

 

[BlueWizard]

I modified my post above and added a new link to a final WWMTM design.

As to your question, it is possible to do this, but is complex.

I'm assuming by -

W-M1-M2-T-M2-M1-W

you are referring to your drawings labeled 'C' and 'D', of which I think 'D' is the more workable design because the tweeters are in a vertical line.

What is your purpose in these proposed designs?

Is it to have a certain final impedance in each section?

Is it simply to move a lot of air?

Or, do you just think they look cool?

There are a few elaborate design similar to this, but they take a great deal of engineering. When you start modifying an already complex design like an WWMTM, and make it more complex, it becomes ...well, you know...very complex.

I mean really, if all you want to do is make loud party music, try this for about $500 each -

http://cerwin-vega.com/CLS215.php

These will kick some serious butt. But, they have their drawback, though very few for that price.

Also, look at these speakers -

http://www.overstock.com/Electronic...orstanding-Speaker-Pair/1581770/product.html?

Very similar to what you propose, note the array or cluster of 4 mid, and the two horizontal tweeters. You and I may be impressed, but everyone else here is rolling on the floor laugh because, impressive as they may look, the speaker are violating SOOOOO many design rules.

These are virtually 'white van' speaker, meaning all show and no go.

Check out this thread to also see some fantastic grand designs by ShinObiwan -

'LGT' Construction Diary -
http://www.diyaudio.com/forums/showthread.php?s=&threadid=93218&highlight=

Shin did actually make a variation of this design, as can be seen later in the thread, but trust me it wasn't cheap or easy. Shin is an expert in all aspects of speaker design, construction, and finishing.

So, again, what is your real objective. Just to design some cool looking speakers? Is it to move a lot of air? And is there a reason why you need to move so much air? DJing? PA? Party?

And, and this is important, what is your budget, even if this isn't at the point of realization yet, you must have a general budget idea?

Even fantasy budget will tell us a lot. If the budget is low, then we have completely different approach.

I've even conceived of some 4-way-ish system, even low (somewhat) budget systems. But there are practical considerations that make it difficult.

Well, that enough for now. I'll check back later after you looked at some of the links.

Steve/bluewizard

 

[terry j]

never heard a good four way yet.

not sure why you're so set on it, esp if it's your first build. (I mean by all means do what takes your fancy, but don't discount some of the excellent advise given so far)

Out of your designs above, the only possible one that could work would be one, I'd forget about the rest.

I simply cannot see any advantage of a four way over a properly designed three way, and a heck of a lot more potential problems.

not least using first order x-overs. if you're gonna do a four way surely you'd better start getting some decent slopes on them?

(not a first order guy...and not really an mtm guy either!)

 

[sumsound]

Ok, but how "major" are these polar issues and how "major" are they in a 3-way version, which seems to have some degree of popularity?

BTW, I'm not in the least bit fazed at attempting a 4-way. If in the end it doesn't work to satisfaction, I'll just scrap the cheap MDF prototype box, either flog the excess drivers off on ebay or keep them for a future project, and then attempt a 3 way. 🙂

Cheers,
Glen

Download EVI array show, and make your w m1 m2 t m2 m1 w array.

Figure out what the spacing between your drivers.

You will have to try and simulate driver attenuation in relationship to Xover points and you' will see very quickly what happens.

Driver spacing will start causing polar beaming if the drivers are spaced greater than 1/4 wavelength from center to center.

Di Apolitos (Don't know if a 3 way can still be called that) Have polar issues at xover, with just a 2 way. You are going to have bad lobes. And a really narrow "sweet spot".

 

[GK]

never heard a good four way yet.

I have.

not least using first order x-overs. if you're gonna do a four way surely you'd better start getting some decent slopes on them?

My understanding (from the little I've read) is that the crossover order requirement is relaxed in a 4-way design as each driver is only used over a limited frequency range and the frequency responses of the drivers overlap by a greater amount.

From here:
http://www.lalena.com/Audio/FAQ/XOver/

"Some people believe that it is best to use a low order crossovers when possible, preferably only 1st order. This does have some benefits. With the greater frequency overlap, voices will not seem to jump from one driver to another as quickly as they would with a steep crossover. It also follows the minimalist approach where the simpler the circuit, the less distortion and modification of the signal is introduced. The problem with 1st order crossovers is that the frequency overlap in the drivers would have to always be at least 2 octaves (or more) in each direction from the crossover point. It would probably require at least 4 drivers.

Another belief is that even order (2, 4, 6...) order crossovers should be avoided. Even order crossovers tend to have spikes or dips in the frequency response around the crossover point. These spikes can be as bad as -30db, but can easily be solved by reversing the polarity of only one of the speakers, limiting the spike to about +- 3db. "

?

Cheers,
Glen

 

[GK]

Download EVI array show, and make your w m1 m2 t m2 m1 w array.

Figure out what the spacing between your drivers.

You will have to try and simulate driver attenuation in relationship to Xover points and you' will see very quickly what happens.

Driver spacing will start causing polar beaming if the drivers are spaced greater than 1/4 wavelength from center to center.

Di Apolitos (Don't know if a 3 way can still be called that) Have polar issues at xover, with just a 2 way. You are going to have bad lobes. And a really narrow "sweet spot".

Thanks!
Will do. I'll start with some established WMTMW designs first.

Cheers,
Glen

 

[GK]

I modified my post above and added a new link to a final WWMTM design.

As to your question, it is possible to do this, but is complex.

I'm assuming by -

W-M1-M2-T-M2-M1-W

you are referring to your drawings labeled 'C' and 'D', of which I think 'D' is the more workable design because the tweeters are in a vertical line.

What is your purpose in these proposed designs?

Is it to have a certain final impedance in each section?

Is it simply to move a lot of air?

Or, do you just think they look cool?

There are a few elaborate design similar to this, but they take a great deal of engineering. When you start modifying an already complex design like an WWMTM, and make it more complex, it becomes ...well, you know...very complex.

I mean really, if all you want to do is make loud party music, try this for about $500 each -

http://cerwin-vega.com/CLS215.php

These will kick some serious butt. But, they have their drawback, though very few for that price.

Also, look at these speakers -

http://www.overstock.com/Electronic...orstanding-Speaker-Pair/1581770/product.html?

Very similar to what you propose, note the array or cluster of 4 mid, and the two horizontal tweeters. You and I may be impressed, but everyone else here is rolling on the floor laugh because, impressive as they may look, the speaker are violating SOOOOO many design rules.

These are virtually 'white van' speaker, meaning all show and no go.

Check out this thread to also see some fantastic grand designs by ShinObiwan -

'LGT' Construction Diary -
http://www.diyaudio.com/forums/showthread.php?s=&threadid=93218&highlight=

Shin did actually make a variation of this design, as can be seen later in the thread, but trust me it wasn't cheap or easy. Shin is an expert in all aspects of speaker design, construction, and finishing.

So, again, what is your real objective. Just to design some cool looking speakers? Is it to move a lot of air? And is there a reason why you need to move so much air? DJing? PA? Party?

And, and this is important, what is your budget, even if this isn't at the point of realization yet, you must have a general budget idea?

Even fantasy budget will tell us a lot. If the budget is low, then we have completely different approach.

I've even conceived of some 4-way-ish system, even low (somewhat) budget systems. But there are practical considerations that make it difficult.

Well, that enough for now. I'll check back later after you looked at some of the links.

Steve/bluewizard

Well of course I don't want to build these speaker just because "they look cool". I did state the objectives in my opening post and nothing is set in concrete.
If any of these designs with parallel drivers are just too much of an elaboration over the WMTMW (for example), break too many design rules and are likely to be more show than go, then I'll drop 'em like a hot potato.

Thanks for the links, I'll have a good look through them after dinner.

Cheers,
Glen

 

[AndrewT]

Have a look at the Wilson front panel layouts.
Why are they so complicated.?
I suggest to get a physical time alignment of the various drivers.
I further suggest he has gone this route because the resulting sound from physical alignment is better than electrically compensating (time delay) for physical non alignment.

I would look at WWMlowMhTMhMlow, with the possibility that the WW could be side mounted to allow a very narrow front face. And offset the drivers from centre line, bringing the treble and Mh towards the central mono image.

I would also consider using 16ohm, or higher, driver impedances for all except the WW.

Finally,
spend much time deciding on whether the sound between single pole and two pole filters is audible and which is preferable, even to the extent of building a prototype MhTMh to test how each filter type works.

 

[tinitus]

There is one option where a 4way could make just a bit of sense
That would be to actively cross the woofers below 100hz, where the midwooofers roll off by themselves
But you would be looking at 24/12db slopes, or if you design something yourselves 12/12db would be possible
AND fore high SPL you would need some very tough midwoofers

Its a kind of brute force