[Ultralight]

Quick question. I had asked this a while back on another forum but could not quite understand the answers in terms of whether there's an actual impact or not.

So Moderator, hope it is OK to post here.

One of the reason for full rangers is that everything is in phase.  I think that matters.  However, to fortify some of the lower frequencies, some full rangers run in 1.5 format where the 2nd drive runs with a high frequency cutoff such as running from 400hz and below.   I'm told that the 2nd driver runs 90 degree out of phase with the top full range.

Why does this not ruin the point of a full ranger which includes its music being in phase? 

Thanks in advance for educating my ignorance....

Thanks.

[FullRangeMan]

I had asked this a while back on another forum but could not quite understand the answers in terms of whether there's an actual impact or not.
The 1.5 way is in true an crossover or part or it, as a inductor etc to cut the mid freq apart from the woofer. So it have a deleteric effect on the bass freqs harmonics, which become poor, less rich in harmonics mainly in acoustics music.
However, to fortify some of the lower frequencies, some full rangers run in 1.5 format where the 2nd drive runs with a high frequency cutoff such as running from 400hz and below.
The 2ºdriver should not be a FR driver but a woofer based on the brother FR as this first 2 drivers FR8 & MW8:
http://www.hempcone.com/hemptone.com_new/hemptone%20website_003.htm

I'm told that the 2nd driver runs 90 degree out of phase with the top full range.
Never heard about this effect but its possible, it is consequence from an inductor, use air core inductors avoid cheap iron core inductors at all costs.
Only use a Inductor if really need, otherwise use nothing, just connect the drivers in parallel for 4 ohms.
Why does this not ruin the point of a full ranger which includes its music being in phase? 
With an inductor the drivers emit different freq ranges of music, the woofer emit just bass, no mid&treble sound.

[DaveC113]

We're really not that sensitive to phase at those frequencies, imo it's not an issue.

[JLM]

Don't like the 1.5 design concept.  Like FRM stated, if you need a woofer, use a woofer.  Omega offers both 1.5 and subwoofer options.  Unfortunately Louis doesn't offer many insights to the internals he uses.

Running the mid-woofer out of phase (180 degrees) would be in effect creating an 'electric dipole' and would add a midrange crossover, pretty much destroying the idea of using a single driver.  Not sure what effects running an overlapping driver 90 degrees out of phase would do at midrange frequencies, but obviously many subwoofer manufacturers offer fully adjustable phase control (but subs can be remotely located from the mains and crossover much lower).

[roscoe65]

I own both single driver Omega's and 1.5 way versions.

I can say that the second driver is not 100% transparent.  Whether this is due to the characteristics of the speaker or a psychoacoustic effect.  In the single driver version, the speaker is much more prominent in the midrange, and may sound "purer" than the 1.5 way version.

I haven't cracked open the speakers, but according to Louis the only component is an air-core inductor in series with the lower driver.  Phase shift should be 90 degrees, though as other posters have asserted, it is unlikely to be detectable at those frequencies (<500hz).

My feelings about the 1.5 way are similar to my feelings about 2.5 way speakers:  they offer additional midbass reinforcement without going full three way.  The alternative in Omega's case is to use a larger helper woofer, but this starts to look like a full-on multiway.

The key in single driver speakers is that the main driver - the one working across 90% of the audio range - runs without any crossover components at all.  This is not new; Dynaco ran the A25 midwoofer open, as did JBL in the L100, Reference 3A with the Royal Master Control, and a number of guys are doing the same thing  with Altec 414's in two-way applications.

One aspect of the 1.5 way speaker vs. the one-way speaker is that while is is technically more efficient, it is also a bit more demanding on the partnering amplifier.  I have found that my SET amp (on the 8 ohm tap) is not has happy in the bass with the 1.5HO Monitor.  Perhaps if I switched to the 4-ohm tap I would have better success.  On the other hand, my RWA Signature 16 doubles power from 8 ohms into 4 ohms.  The addtional driver below 500hz and the reduced impedance in that same range has a twofold effect:  the additional bass driver increases sensitivity in the bass range and the reduced impedance in the same range draws more power from the amplifier.  I would make the strong case that the 1.5 way speakers are really happier with amps that are more tolerance of a 4-ohm impedance.

One option I have yet to try is putting my big Dennis Had amp (PSE of 10-24 wpc) in the system.  The word is that this amp puts out about the same amount of power from 2 ohms to 12 ohms from its single output tap.

[Ultralight]

Thanks everyone.

Helpful. 

Roscoe - is the slightly less transparent 0.5 driver quite apparent?

I ask because not matter what system I tried including a 40+ watt  SET tube amp I tested, the full range driver just offers a musicality that is very moving that I've not encountered in any multi driver system.  (It really shone with that SET amp!)  In part, the drivers I have are very fast which I value. But I do hanker for a thicker midrange.  One way I get around it is to EQ the mids and bass more, and play at lower level which I normally do anyway so as not to over drive it.  I am already running bi-pole so the load of more bass production is shared across two drivers.  So I am thinking of just using two drivers on top of each other driven full range on each face of the speaker which makes FOUR speakers full range. (at 8 ohm - 2 parallel, and then two in series). 

But then someone mentioned in another thread the dreaded comb filter effect when two small drivers are put on top of each other. I don't have a clue how to figure which frequencies are affected by the comb filter.

So it is a learning experience... You guys are great!! Thanks.

[FullRangeMan]

But then someone mentioned in another thread the dreaded comb filter effect when two small drivers are put on top of each other. I don't have a clue how to figure which frequencies are affected by the comb filter.

Comb filter effect are in the treble range, over 3kHz or even lower according the driver.

[JLM]

Why not just add a subwoofer (or powered midbass speaker) and avoid all these issues?  Plus you can locate the sub/midbass speaker where it does the most good.

[mboxler]

One of the reason for full rangers is that everything is in phase.  I think that matters.  However, to fortify some of the lower frequencies, some full rangers run in 1.5 format where the 2nd drive runs with a high frequency cutoff such as running from 400hz and below.   I'm told that the 2nd driver runs 90 degree out of phase with the top full range.

I'm no expert, but...

If we treat a driver like a resistor, then the voltage thru the full range driver is always in phase with the source voltage. Yes, voltage thru an inductor leads the source voltage by 90 degrees.  However, if we put a resistor (driver) in series with an inductor, at the frequency when the impedance of the inductor equals the impedance of the resistor, the voltage thru the circuit will lead the source voltage by only 45 degrees. 

A 3.1831 mH inductor, at 400 hz, has an impedance of 8 ohms.  Assuming the driver is 8 ohms, you can plug these values into this calculator and get the result.

http://keisan.casio.com/exec/system/1258032600

If you double the frequency, you will notice that the phase increases.  Likewise, if you halve the frequency, the phase decreases.

As stated earlier, though, as the frequency increases, the voltage across the driver decreases, and you only hear the full range driver.

At least I think this is right.

Mike

[FullRangeMan]

The phase not would be 4.5º?  instead 45º
Impedance Z 100.31736890515 Ω
Phase φ 4.5587556360199 degree

[mboxler]

The phase not would be 4.5º?  instead 45º
Impedance Z 100.31736890515 Ω
Phase φ 4.5587556360199 degree

Odd.  I get, with 8 Ω resistor, 3.1831 mH inductor, 400 Hz...   

             11.313710521673 Ω
Phase φ 45.000010243457 degree

Which makes sense.  10 volts thru a 11.313710521673 Ω circuit draws 0.8838833184606939 amps.
                               
0.8838833184606939 amps thru an 8 ohm driver equals 7.071066547685551 volts, or -3db.

[roscoe65]

The actual phase angle of the low passed portion will vary with frequency, ranging from 0 degrees at DC to 90 degrees at an infinite frequency.  An 8-ohm, 500hz helper driver would need a 2.7mH inductor in series.  This will give about 45 degree phase angle at the -3dB point.  This phase angle will decrease with frequency.

However, drivers are not resistors, and their impedance does not remain constant with frequency.  If we assume that the driver impedance doubles by 100 hz relative to 500 hz, we would expect the phase angle to be 6 degrees instead of 12 degrees.  The phase angle above 500hz will also be lower than expected dur to rising speaker impedance, but will only be about 10 degrees less than an 8 ohm load.  We are also seeing increasing phase angle above 500hz while impedance in increasing (reducing phase angle) and output from the helper driver is falling at 6dB/octave.  That means for out speaker we would expect to see the phase angle at 1khz to be the same 45 degrees as 500hz, only now the output of the driver is 6 dB down.  By the time phase angle starts to really creep up the output from the driver is almost nothing.

If phase angle is important, it would appear that it's effects in this application are minimal in the bass range, and appear to be most prominent in the midrange (500hz to 1,500 hz).  I don't know how important phase is in this range, but I could see it having a muddying effect in the midrange.  At  a ten-foot listening distance, a 45 degree phase angle will equate to a 3 millisecond delay at the listening position.  The underlying question is how much does this 3 millisecond delay matter at each frequency?

[planet10]

There are 2 ways to do this.

1sr, to answer your question, During most of its range the 2nd FR is in phase, but no matter how you do it the rolled off driver transitions thru 90° as it rolls off. So at some point it is 90° out of phase but well down in level by then.

The “normal” way is to run a 2nd driver in parallel with a series inductor to roll it off at higher frequencies. Assuming the typical voltage amp this means 3 dB of gain due to the 2nd driver and another 3 dB due to the doubling of the input power (due to the halving of the resistance) equal 6 dB.  This can be used as baffle step compensation but in room a speaker rarely needs that much. Even if it did you gain 6 dB to flatten the on-axis FR but get a 6 dB increase in the power response.  This last bit of the analysis only works if you carefully choose the turnover frequency to be where you have the baffle step.

The second way is to run a 2nd driver in series with a shunt capacitor to roll it off at higher frequencies. Assuming the typical voltage amp this means 3 dB of gain due to the 2nd driver and the loss of 3 dB due to the halvling of the input power (due to the doubling of the resistance) meaning no change in level. With no level change where you place the turnover frequency is much less critical.

Now if you have a current amp (not many of those) everthing flips around. Tube amps — particular SE tube amps are typically voltage amps but some get pretty close to the transition point so things aren’t quite as black & white.

This document covers things in a more analytic manner with diagrams & formulas.  http://www.planet10-hifi.com/downloads/Dual-Driver-Wiring.pdf

dave

[FullRangeMan]

Thanks Dave for clarify

[Ultralight]

Juuuust checking back in and grateful to see so many more responses. 

So.... given that there are phase shifts, but varies at different frequencies and different decibels, what is the bottom line - do you guys think that  it make an obvious difference to the listener?  I realize this is going to vary from listener to listener but wonder if there's a general concensus.

Roscoe65 notes that his 1.5 is not as transparent and I wonder if the phase is the reason.

Again, thanks.  I think we're pretty close the end of this thread's life....

[JLM]

Have never understood why designers double up (or more) on drivers for in-home speakers (other than they can get them cheap).  Better to start with a more robust driver that better fits the job.  If your extended range driver can't reach say 30 Hz, why add another?  Baffle step compensation can be done with simple circuitry or helped with a wider front baffle. 

As I mentioned above why not just add a subwoofer?  Oh I know, because a good sub isn't cheap and without DSP can be hard to properly integrate with the mains.  Deep bass is hard to do correctly.  According to Duke LeJeune (AudioKinesis and someone I respect) it takes a swarm of subs to do it right (his swarm sells for $3000 USD).

[roscoe65]

Please take my comments regarding 1.0 vs. 1.5 way Omega speakers in the context of my system.  My Omega 1.5 way speakers are wired with an inductor on the helper driver.  This results in a lowered impedance from the lower midrange down.  The amp I have been using most in evaluating these speakers is a RWA Signature 16, which doubles in power from 8 ohms to 4 ohms.  That means the 1.5's can yield an additional 6 db in the region below 500hz as compared to a single driver model.  When using the SS amp, the bass muddied the sound a bit, but only in contrast to the single driver model.

I then switched over to my 4wpc SET amp.  When the speakers were completely unbroken in, the bass sounded too thin with this amp.  Now, however, I find the bass to be perfect with the tube amp and the sound to be more like the single driver model.  However, the single driver model still sounds more "pure", but is likely due to a more prominent midrange that makes some vocals "pop" more.

The point is that the amp-speaker relationship is important.  In case of my Omega 1.5 way speakers, the BSC starts around 500hz, with the second driver adding 6dB when using a SS voltage amp and 3dB when using my SET.  I agree with Planet10 that we are really trying to achieve +3dB BSC, and that when using a SS amp the midbass become a bit too much.  That being said, when Louis created the 1.5 way models he was using the Decware Zen Triode (2wpc SET (triode-connected EL84)), which has a single output tap at 6 ohms and which allegedly like lower impedances than most SET's.  The helper driver in this case flattens the impedance below 500hz a bit, increasing the bass output.  I can confirm that when using a SET, the 1.5 way Omega does not lose an appreciable amount of transparency, beyond reducing the vocal prominence.  I feel that if one were using SS voltage amp the bass would be too much.

Juuuust checking back in and grateful to see so many more responses. 

So.... given that there are phase shifts, but varies at different frequencies and different decibels, what is the bottom line - do you guys think that  it make an obvious difference to the listener?  I realize this is going to vary from listener to listener but wonder if there's a general concensus.

Roscoe65 notes that his 1.5 is not as transparent and I wonder if the phase is the reason.

Again, thanks.  I think we're pretty close the end of this thread's life....

[Ultralight]

Thanks Roscoe.  Much appreciated!

[PeterKK]

Hi,

I recently got hold of a pair of single driver speakers. Each speaker has 2 identical drivers so I think it’s a 1.5 design. What I find interesting is that despite each speaker having 2 identical drivers with no crossover the two drivers don’t sound the same (ie the bottom driver clearly doesn’t play higher frequencies). Initially I thought this to be a defect but based on the discussion I understand that’s actually normal, correct? Or are there different designs and it depends?

[FullRangeMan]

Hi,

I recently got hold of a pair of single driver speakers. Each speaker has 2 identical drivers so I think it’s a 1.5 design. What I find interesting is that despite each speaker having 2 identical drivers with no crossover the two drivers don’t sound the same (ie the bottom driver clearly doesn’t play higher frequencies). Initially I thought this to be a defect but based on the discussion I understand that’s actually normal, correct? Or are there different designs and it depends?

If each driver has a separate enclosure, the bottom driver may be well stuffed which will decreased treble and enhance bass, no electric component is need.