Is the 2.5 way speaker the ideal home speaker?


Time for what I hope is another fun thread. 

One type of speaker which is actually pretty common but which gets little press / attention here on audiogon is the 2.5 way. 

A 2.5 way speaker is almost a 3-way, but it isn't. It is a speaker with 3 drivers, but instead of a tweeter, midrange and woofer (TMW) it lacks a true midrange. The "midrange" is really a mid-woofer, that shares bass duties with the woofer. Often these two drivers are identical, though in the Focal Profile 918 the midwoofer and woofer were actually different drivers with the same nominal diameter (6"). 

The Monitor Audio 200 is a current example of the concept, but I am sure there are many others. It's also quite popular in kit form. One of the most high-end kits I know of is the Ophelia based on a ScanSpeak Be tweeter and 6" Revelator mid-woofers. I haven't heard them, but I am in eternal love with those mid-woofers. I believe the original plans come from the German speaker building magazine Klan Ton. 

However many other kits are also available

But regardless of kit, or store purchased, are you a 2.5 way fan? Why or why not? 

Best,


Erik 
erik_squires
I would have to say that the 2.5 way speaker is the least common of speakers. I have owned a 2.5 way Spendor and it was real nice. There is only one 2.5 way Spendor that is still in their line.
http://store.acousticsounds.com/d/94325/Spendor-Spendor_D7_Stereo_Speakers-Speakers
What advantage would a 2.5 way have over a true 3-way?  I'd think a real dedicated midrange driver would be better than a midwoofer that also has to handle bass frequencies.  I suppose you could have a more simple crossover with a 2.5 way, but plenty of 3-way speakers have well designed crossovers.  

KEF uses 2.5 ways in some of their Q and R series lines, and the Paradigm Prestige series is 2.5 way.  I haven't heard the KEFs, but the Paradigm Prestige is a very nice sounding speaker.  
Possibly,, as long as the bass driver is in its own enclosure?
I think a 2.5 way is an interesting concept. I prefer a 2 way with a subwoofer, which provides options in tailoring the lower frequencies. 
The only example I have seen had a level bypass circuit at so one did the mid to high and the other the mid to low. From memory the enclosures were fairly complex with each mid/bass driver ported differently. The brain has had too many dinner wines to remember their brand.
+1 @rlb61 - This is also one of my top methods for exactly those reasons 

amg - I think you have to separate the enclosures, to avoid having the lower woofer interact in weird ways with the upper woofer. 


I think one of the main benefits of a 2.5 way is foot print vs. bass extension and dynamic range as well as overall speaker sensitivity.

2.5 way speakers tend to be made with 6" drivers, so you end up with a rather narrow speaker overall.

there are some close variations, like a T - M - W - W, true 3-way speaker, but with two woofer.

It may have been a 80/90s Duntech design when John Dunlavy was building in Canberra. They could be the PCL-25.

Isn't the Joseph Perspective a 2.5 way?
I think they certainly can be. Look at the Dali Epicon 6 speakers.

The EPICON 6 relies on a 2½-way system. It features an additional woofer kicking in below 600Hz. However, for the highest frequencies the EPICON 6 also incorporates a ribbon tweeter as part of the hybrid tweeter, in reality turning the speaker into a ‘2½ + ½-way’ construction.

This is a nice sounding speaker that also fits well in most home spaces. Close to full range also.

One benefit can be they have more of that “voice of one” coherence compared to a three way. 
The Perspective has two midrange/woofer units. That appears to be different from the 2.5 way described by the OP, which has one midrange/woofer and one full woofer. So, is the Perspective a true 2.5 way or some hybrid variation?
Hi @rlb61 - Sorry for the confusion!

Whether or not a speaker is a 2.5 way is characterized by the crossover, not the woofers.

In a 2.5 way, the two woofers have low pass filters ONLY, but set to different points and slopes. This can be implemented with identical drivers (like the JA Perspective and Klan Ton Ophelia) or like the Focal Profile 918 which used different drivers for each.

The missing 0.5 in the equation (2.5 + 0.5 = 3 way)  is a high pass filter on the top woofer.  This would reduce the bass the mid-woofer plays, relegating it all to the bottom woofer. Without this, both woofers play the deepest octaves.


Best,

E
@erik_squires ... thanks for the info. I really have learned a lot from your insights. 
Since I own Joseph Audio Perspectives, and I like them a lot, I guess that makes me a fan. I do run my Perspective speakers with two subwoofers and have them integrated with the mains via a DEQX Premate. IMO it is a powerful pleasing combination. FWIW I heard the Joseph Audio Pearl 3s at AXPONA this past Sunday and I thought they were terrific too. Same family; fuller presentation than the Perspectives running without subs. Yet I suspect that if I owned Pearls I would still run the stereo subwoofers and simply recalibrate the subs via the DEQX to integrate properly. @erik_squires are you of the opinion that the 2.5 provides the opportunity to "outperform" a "full range" because a sub (or subs) can more than compensate for what the full range otherwise provides? This is of some interest to me. I would hate to "upgrade" to the Pearls only to find I already created a more complete combo with the Perspective/subs/DEQX combo. Your thoughts please.   
hi @astewart8944 !

Well, I think of 2.5 way as full-range. I meant, that for the slim form factor a 2.5 way can offer a lot of benefits compared to a more traditional 3-way with a large diameter woofer.

In all cases, the ability to use a separate amp with EQ and proper room tuning for the bass is absolutely magical, and (when properly set up) will always outperform a full-range speaker without them.

As an audiophile, I spent a lot (for me!) of cash on my DAC, and pre. I don’t want an EQ in most of my music, BUT, if I can run the EQ for the bass only, it’s heaven.


Best,

E
@rlb61 

 thanks for the info. I really have learned a lot from your insights.

What a terribly kind thing to say, thank you. 

E
HI @astewart8944 - Not sure if I was clear.

With the Pearls, I’d be tempted to run the bass units via your EQ and separate amps.

The trouble area is 16 to 60 Hz. In that range, dragons lurk. This is why smaller speakers may sound "faster" or "more musical" - They avoid the dangerous areas, and why a sub with good EQ can totally outperform them.

But since you are already happy with your perspectives and 2 subs - I'd suggest you stick with what you have. :) If you must upgrade, room acoustics are always a good place to work on. Contact GIK Acoustics for great advice. 

Best,

E
We never "must" upgrade. : ) Frankly, the DEQX is present precisely to deal with room acoustical issues. I understand physical treatment is distinct from room correction, but my family room isn't going through any GIK Acoustics treatment that a designer doesn't approve...and she won't be approving any...ever. So we work with the tools we have.
FWIW I truly enjoy your posts; I learn stuff.
Thanks
Al
Erik, my previous speakers were 2.5 ways (Paradigm Studio 60/2).   In reality it is two way design with extra speaker for the low frequencies.  My new 3 way speakers have much better bass - not by extension, but rather by very natural attack and decay of the bass notes.  Disadvantage of any 2 or 2.5 way design is "bending" at the higher midrange. 
@astewart8944 - Then I'd suggest keeping what you have. 

Dialing in a new pair of speakers like that will get complicated. 

@kijanki - Could you explain what you mean about bending at the upper midrange? 

Best,

E
@astewart8944  - The one thing, I would encourage you to play with room acoustics. Throw some blankets between and behind the speakers on the floor. See if you find something there you like. Of course, this is temporary!!! 

Best,

E
Erik,  Two sides of midrange driver membrane produce the same sound only when you face it straight.  At the angle there will be reduction because of the phase shift (longer distance).  At certain frequency and the angle it will  cancel the sound completely. 
I have the Spendor A5r 2.5 speaker. If it has 2 crossovers, 900 HZ and 3.2 HZ. I still don’t understand why this is not called a 3 way speaker? BTW, the bass is outstanding on the s 5 inch woofers!
Hi Erik, fun post!
The most truthful, most honest, most excellent answer is...

The IDEAL SPEAKER is the one you most enjoy listening to, be it single-driver, 2-way, 2.5-way, 3-way, whatever-way.

I am glad and honored to be able to provide this Public Service Announcement.

Tom
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Hi @kijanki - I think you are confusing an open baffle and beaming.

Open baffle speakers behave like you describe, with a complete null at the sides. Boxed speakers do not.

The issue with frequency vs. angle is not related to delays, phase shifts or comb filtering, since the sound is coming from a single surface there cannot be any (unless it breaks up and stops acting like a single surface).

The reason you have "beaming" where the frequency response rolls off to the sides is due to the surface area. The larger the driver, the lower it will beam. This has more to do with the waveform. At very low frequencies, the wave is like a semi-sphere. It radiates in all directions, but at high frequencies it is flat, and mostly travels straight ahead.
 
Hi @donvito101 -

The term 2.5 way is a term of art. The difference is in the filters on the upper woofer. Here it is:

2.5-way : Has NO high pass filter.
3  -way: Has both a high pass and low pass filter.

What is confusing is that in both a 2.5 and 3 way there are 2 crossover points.
Erik - why you ask if you already know the answer?

Let me get a little more basic. Typically when you read about a "crossover point" in a speaker, you are actually talking about 2 filters:

A low pass
A high pass

So a 2-way speaker has a crossover point of 3 kHz. That means there’s a high pass filter that goes to the tweeter tuned to 3 kHz, and a low pass filter that goes to the mid-woofer that is also tuned to 3 kHz. I should point out that reality is even messier than this, but let's stay away from that.

A 3-way speaker has 2 crossover points (say 300 Hz and 3kHz) and 4 filter sections.

1 - HP to the tweeter
2 - HP and LP to the midrange
1 - LP to the woofer.

This adds up to 4 sections.

A 2.5 way also has 2 crossover points, but is missing 1 filter section:

1 - HP to the tweeter
1 - LP to the upper woofer
1 - LP to the lower woofer

That missing HP filter allows the upper woofer to play all the bass.
It is Beaming and not Banding - sorry.  Please read "Speaker horizontal directivity" in the link I provided.

Skeptical: 3 drivers are cheaper than 4.

Positive: only dealing with 2 different makes/models of driver, easier to integrate overall sound; no double "hand-off" from the mid-range.

Hi Kijanki!

You say beaming is a disadvantage? I disagree! :)  A speaker with tight dispersion can sound better in the sweet spot, especially with an acoustically messy room. 

It all depends on your listening style and location. 

Some of Magico's smaller speakers are very wide dispersion. Great stereo imaging no matter where, but the trade off is they need a lot of room or great room acoustics. 

Best,


E

Hi Erik,

Are there challenges in designing a crossover for a 2.5 way given that a large portion of the frequency range (bass) is shared by two identical drivers, but another large portion (midrange) is handled by just one driver?  I was thinking in terms of level matching due to that transition from two drivers to one driver.  

Thanks!
Erik, please read at the link I provided.  You might not care about size of the sweet spot,  but you asked about "ideal home speaker".
A speaker with tight dispersion can sound better in the sweet spot
Different speaker - not the same one.  It appears that you like 2.5 design and not listen anymore.
I really don't think there's any reason to be insulting. Everyone likes what they like, and one person's preference is no more valid than another's.
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@kijanki - 

What I mean to say is, there is no 1 ideal dispersion pattern. From ESL's to open baffles, to traditional multi-way speakers, some with horns. All have very different radiating patterns, and all have ardent fans.

Beaming is not, by itself, bad. It may not be ideal for you in your listening room however.

For the record, my current speakers are traditional 2-way designs, with subwoofer for music. I still like 2.5 ways though. :) 

Best,


Erik 
@Cedargrover 

Indeed, but this is what crossover designers must do anyway. In any multi-way system there is almost always some level matching that must occur, in this case that as well as the dimensions of the upper woofer enclosure must be carefully balanced. 

Best,

E
Thanks Erik. I had assumed (perhaps wrongly) that in a 2.5 way, only the woofer physically closer to the tweeter plays up to the crossover frequency of the tweeter (say 3 kHz), and the other woofer has its low pass set to a lower frequency (say, 500 hz). I thought that was done to prevent lobing, but defer to you.

In such an arrangement, the level matching seems a bit complicated because some of the frequency range up to 3 kHz is covered by two drivers and some of it by one.

EDIT:  According to this article (http://www.bambergaudio.com/technical/2pt5.php) this complication can be taken care of by not adding baffle step compensation.  Pretty cool!
@cedargrover I think you have it backwards.

The top two drivers are just a traditional 2-way.

The treble covers above 3kHz.

The midrange is only covered by the upper woofer. Say it has a low pass at 3 kHz.

Up to here, this is a normal 2-way. The added 0.5 is the lower woofer, which  cuts off at 500 Hz (for example).


Think we're saying the same thing.  But thanks for reminding me that I know just enough to be dangerous....  :)
What I mean to say is, there is no 1 ideal dispersion pattern. From ESL's to open baffles, to traditional multi-way speakers, some with horns. All have very different radiating patterns, and all have ardent fans.
It is not a dispersion pattern for particular speaker but for the group of them.  Speakers that have large membrane (2.5 way) will suffer.

Erik, I think you might be onto something. I couldn’t be happier with the sound and size of my 2 1/2 way Epos M16i’s. They sound good at both low and high volumes and with all types of music. I also currently own ML Monti’s and Harbeth Super HL5+ and as much as I really like them both, if forced to choose the Epos just might win out as it’s just a really good all purpose speaker. 


It is not a dispersion pattern for particular speaker but for the group of them. Speakers that have large membrane (2.5 way) will suffer.

@kijanki - In what way? For me to believe this, I have to agree that

wider = better

at all times. I do not agree with this assessment at all. 

Best,

E
Hmm...seems no one pointed out the real advantages of 2.5-ways (at least well designed examples). It's the same advantage of 2-ways: the high crossover point and resulting coherency. In a well designed 2-way, it's often difficult to make out the separation of drivers, whereas I rarely encounter a 3-way that achieves the same feat. I can usually hear that there's 3 or more drivers doing the work.

A midwoofer and tweeter crossed over at say, 3.8kHz, benefit from coherency and lack of crossover distortions where the meat of the music lies: in the midrange. This is largely why speakers like Harbeths and Spendors can produce vocals that rival some electrostats. 

Of course there can be disadvantages to a high crossover point, but I find they are insignificant or inaudible in most high quality 2/2.5-ways.
I'm not sure I follow, @helomech - 

Usually higher tweeter points are achieved with 3-way systems which use a "true" midrange. 

Best,

E
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