Small 3-way vs 2-way

[stoc005]

Does it make any sense to design a small 3-way to replace a 2-way monitor-type speaker?

It would be for a small to medium room but no bigger. Not looking to hit 140db......

Drivers: 6.5 or 7 inch bass driver - ported, 2 or 3 inch cone midrange and a 3/4 or 20 mm dome tweeter.
Crossover around 300 Hz. or so for the bass to midrange. Midrange to tweeter - 3K-5K Hz. or so. Similar to almost any other 3-way.
Speaker form factor to be small, almost bookshelf size. Not a tower or anything that tall.

It would be more expensive than most 2-ways because of the more complex crossover(s) and the drivers aren't necessarily cheaper either. I'm not a fan of minimalist crossovers so I'd probably use 2nd order at least, and the parts won't come cheap for quality.

Does doing this make any sense? It does minimize doppler distortion, which I can hear every time I listen to my 2-ways. Are there any examples of small DIY 3-way like this?? How do they sound?
Does a well designed 3-way speaker better sounding than a well designed 2-way?? It seems to all boil down to that question.

[tomewing]

Hi,

I'm building small 3 way floors standers at the moment, using a 1 in dome tweet, 3 in mid and 7 in bass. Some thoughts:

Another advantage of a small 3 way of the type you described is that the mid will probably have good off axis performance at the crossover point and beyond. If you decide on a tweeter with good off axis performance such as the seas dxt, the transition can be very nice indeed. There are examples of 2 ways that do this too, but not with the xo at 3k.

The other advantage is the ability to seal the mid and port the bass, giving good transient response in the midrange where it is arguably the most important, while maintaining the power handling. Designing good crossovers will be the main challenge I think, at least that is my finding.

Tom

[bobodioulasso]

It sounds to be a good idea. Specialised drivers can be choosen. The woofer can be a plain woofer (havier cone, lower Fs). The small midrange driver will not suffer of early cone breakups and will benefit of a lighter cone.
The tweeter may be cheaper (higher Fs).
I can't find any drawback.

[Richard Ellis]

Couple of issues...Ported with a 6 1/2" might get your box too big for the bookshelf, depending on how far down in Fr you can get. Sealed will get you that small box. To go three way is really dependent on how far up your woofer can get to overlap the tweeter. Six & a half inch drivers usually will reach up that high, 10" usually not & 8" maybe. Then there is the boo-koo phase shifting going on with three ways. Myself, I like Two-ways with De Appolito twin drivers, imaging is great..........I dunno, crunch some numbers for a variety of configurations & see what peaks your interest.


__________________________________________________ _______Rick.........

[AllenB]

Originally Posted by stoc005

It would be more expensive than most 2-ways because of the more complex crossover(s) .....

Cost of the crossover won't be as much of an issue as the complexity in designing it, assuming it can be made as good.

What is your reason for wanting this, is it directivity, power handling, bandwidth, dynamics...or is it just the cool factor?

[EngelholmAudio]

The general idea of multi way is that every increase in "number of ways" gives the theoretical possiblity to ease the job description of each driver. Look at it this way; a 1 way fullrange must with one driver produce from 20 to 20'000 Hz and with good directivity pattern.

Increased number of ways, makes easier working condition for each driver but increases complexity in cross over, baffle design, etc.

Once on 3 way, interesting opportunities comes. For instance, if you x over between bass and midrange at ~400 Hz you can easily adjust tonality by LPad's (attunators) in the three ranges, bass/mids/high. This is powerful and very important to get right.

If you by monitor also mean near field listening, directivity is less of an issue.

[AndrewT]

Hi,
I like the idea of 3way.
I only have one pair and they cross @ 400Hz and 6kHz (210bass, 135mid, hd-3p treble).
All my others are 2way.

Be prepared to tri-amplify (passively) or even go to fully active, at least for the lower crossover.

[sreten]

Hi,

The answer is not really for a small two way. If you can get a good tweeter
that can cross over low there is not a lot of point going for a small 3-way
with a single 6.5" bass driver IMHO, if budget / complexity is an issue.

Compare :

Zaph|Audio - ZA-SR71 and Zaph|Audio - ZDT3.5

Generally 3 ways make more sense with doubled 6.5"ers or 8"+ bass units.
And even with doubled 6.5"ers a 2.5 way may be simpler / work better.

Here is a small 3-way : Statements_Monitor

rgds, sreten.

[bobodioulasso]

As the OP stated, intermodulation distortion (dopler effect) is the main drawback in 2 ways.
Also, midwofers are kind of compromised drivers as they have to go low and high.
I think a three way, provided it is well implemented, is superior, whatever its size.

[Michael Chua]

My latest 3-way. A small 25L BR tower. F3 = 37HZ

Woofer = USHER 8137A
Mid = Vifa 3" Dome D75MX
Tweeter = Vifa XT25SC90