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222.166.2.28
This speaker is using expensive drivers. But I wonder why choose 2.5 Way design over a 3 way design.
This 2.5 way will be just as expensive as a 3 way.
Any thoughts ?
Follow Ups:
A 2.5 way lets you use two small drivers to move air at low frequencies without getting interference affects in the mid range from widely spaced double drivers. But a D'Appolito design will do similar things with better controlled dispersion and it will save one low pass filter for rolling of the bass only driver.
I have a pair of KEF 103.2's and a pair of ADS L710's. They both sound good EXCEPT the midrange(voice) are clearer with the ADS's. That is no surprise since the ADS speakers have a midrange driver. I guess this is the reason shy I think a 3 way design SHOULD be better. One other thing...the midrange is a 2" soft dome driver. The speakers have a metal grill cover. It probably was pushing in on that 2" dome for years. I took it off and was ready to pull it out and I noticed it came back out on it's own after 1 minute or so. I think it is a good design..
One of my favorite speakers used a Morel 2" soft dome midrange. I really miss those speakers.
Trashed by mold.
charles
The final speaker sensitivity is limited, in most cases, by the sensitivity of the midbass driver(s). In this case, the 2.5 way allows for an 89db sensitive speaker because the "0.5" driver does a boost below the baffle step compensation frequency, where in a conventional 3-way you instead do a cut above using a BSC compensation or "shelving" filter.
So, if say 4db of BSC equalization was implemented, to do the same thing in a conventional 3-way would have resulted in a 85db sensitive speaker.
With a 2.5 way active system you get the benefit of a higher (more conventional) nominal impedance (compared to 2.5 passive), but you now have speakers you need to plug into the wall, which some people try to avoid for their own audiophile reasons.
I like 2.5 way designs. I also like designs where you have a three way that provides baffle step compensation inherently without the use of a BSC equalization circuit but by other clever means to get the required boost below the BSC frequency! ;)
Cheers,
Presto
No advantage, just design trade offs. From what I understand,
typically a 2.5 will use multiple woofers and tweeter. One woofer (can be ported / passive radiator assisted) will be cut off lower in frequency leaving only one woofer, usually closest to the tweeter to continue up to the tweeter crossover point. This allows for augmentation of the bass frequencies because the bass requires a larger (more displacement) moving area without messing up the midrange closer to tweeter crossover. The cutting off of this second woofer lower minimizes the problems with distance and the likelihood of muddiness of sound due to the second, farther away woofer's timing consideration and local at tweeter crossover.
PeterZ
Good question-
I have often wondered about a 3.5 and 4 way speaker myself...
Much better than "Tower" and why do hear a German accent when reading words I don't understand?
2.5 vs 3 way is more about a designers preference, than one being better than the other in a particular speaker.
A "2.5 way" usually refers to a design that utilizes one tweeter, one active woofer, and one passive woofer. It mimics a true 3-way in appearance and in performance, at least to a degree.The addition of a passive woofer increases bass output without substantially increasing the complexity of the crossover or the power requirements - as true 3-ways almost always do. The crossover design in a 2.5 way is basically the same as in a 2-way system, and when the crossover circuit is simpler and only two drivers need to be driven, the efficiency rating of the speaker is usually higher. Also, because the overall parts count is kept lower in a 2.5 way than in a 3-way, the price of the 2.5 way speaker might reflect that.
2.5 way speakers are not always cheaper and/or more efficient than 3-way speakers, though. The parts used, the design, the construction quality, etc.., can affect their final cost and/or the electrical efficiency rating.
Edits: 12/12/14
The speaker you are describing is not a 2.5 way but a 2 way. You never count the passive radiator as a driver(unless you are a manufacturer trying to make a 2 way look like a 3 way for sales purposes). A passive radiator is simply a port substitute(which usually has slightly poorer transient response than a port). Almost the same speaker could be designed with a port and it would probably save a little money.
Both midbass drivers are driven by the amp, but lowpassed over at different frequencies. The "upper" driver goes all the way up to meet the tweeter, crossing over usually around 2kHz. The "lower" driver is for baffle step compensation, and is rolled out (usually first order) to be down -3dB at the frequency, corresponding to a wavelength equal to 3x baffle width, where the on-axis response in 4-pi space is "up" 3dB due to off-axis energy losses. Below this, both midbass drivers are operating in tandem. This yields an on-axis response that is not weak in the bass when the speaker is operating in free space.
From my experience with PSB, 2.5 way are usually employed with tower speakers and the driver closet to the floor is usually cutoff before 300Hz to eliminate floor bounce. The second driver overlaps the bottom driver in the bass but not all the way down. There is no passive driver scenario, at least not with PSB.
Seems the term 2.5 has undergone some changes over the years to me several different things. passive radiators, double woofers, even two ways with subs have been referred to as 2.5 at some time.
So what would it really mean "now"?
charles
If I misused the term "passive" here, I apologize to all.My old triple driver Klipsch KG 4.2 speakers were sometimes referred to as "2.5 way" speakers, back in the day. In reality, they were "2-way" speakers that employed one passive radiator for bass reinforcement. I also remember that my old triple driver B & W DM-603 S3 speakers were sometimes referred to as "2.5 way", when in fact they employed a passive woofer design. So, I guess it depends on who you talk to...
Edits: 12/12/14 12/12/14
None with my experience either. The layout PSB uses is the most common form of 2.5 way.
And yet despite the look on my face, you're still talking.
:)
One less crossover and one less crossover point.
Jack
Not really.
A typical 2.5way uses two identical mid-woofers one of which is crossed at the crossover point normal for a 2way while the other only operates in the bass and rolls off in the 300Hz region to account for baffle step.
Still requires two xover points just like a 3way but the mid has no lo cut.
Probably not the best configuration for impedance-sensitive valve amps.
So HP's influence extended beyond the anglosphere.
...except WAF.
I could see an advantage to a 2.5way if one woofer was close to the floor to reduce floor bounce and better integrate the system to the room.
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