[Ultralight]

Passive crossover often shifts the phase between drivers.  Does an 'air core coil' do that in the Omega 1.5 setup? 

Curious...

UL

[roscoe65]

A single inductor should give a 90 degree phase shift.  Coincidently, the Omni will give this same 90 phase shift by physically locating the secondary driver 90 degrees from the primary driver.  You usually don't have to worry about phase with first order crossovers.

[doggie]

This topic is of interest to me as I just purchased a pair of the new Super Alnico High Output (1.5) floorstanding speakers from a fellow AC member.

These speakers have both drivers run electrically in parallel and mounted in the same plane on the front panel. The speaker is rated for 99db at 4-6ohms. Additionally the lower driver is crossed over with a simple 6db inductor at 500hz. This x-over point seems like a pretty busy frequency, overlapping the range of a lot of key acoustic instruments as well as within the fundamental frequency ranges of both male and female voice. Perhaps the gentle 6db slope puts the actual second driver's contribution well below 500hz?

Louis I know that you are busy turning out speakers for hungry audiophiliacs but perhaps you could describe some of your design choices for these great speakers. I am also interested in how one calculates the 99db and if this relates in any way to where the speakers are crossed over or if it is a simple function of paralleling the two drivers and unrelated to the specific x-over point.

Thanks for any education sent our way...

[Louis O]

Hi roscoe65,

Many thanks for your post and clarification here as well as the other threads, much appreciated.

Hi doggie,

Thanks and my original design was at 200Hz. I went for 500Hz as I liked the bit of punch I got with it, but I'm revisiting it for the Alnico version.

The RS5 version will remain as they are.

I do agree with you about a lower point may be cleaner in the transition. I will have more very soon.

I went with the 3 dB increase and had a starting point of 95.6 and rounded up by paralleling the drivers. Maybe I should have been conservative and call it 98.

Thanks,
Louis

[roscoe65]

Hi Louis,

I am about to embark on some testing regarding the various configurations for dual-driver RS-5 based speakers.  I have a pair of original wide-baffle Super 3's with RS-5 drivers I purchased from you (Thanks!) as well as a spare pair I purchased from another AC member.  I had also purchased a pair of enclosures to repurpose the Fostex FE127e drivers I removed from the Super 3's.  The enclosures are built to the Fostex design, tubed to 60hz and area almost identical in size to the Super 3T's you sell.  To further complicate matters, I have a stereo pair of DIY sealed 8" subs (an "improved" version of the bucket subs).

My current resources:

1.  Wide baffle Super 3's.
2.  Narrow baffle bookshelf speakers similar to Super 3T's.
3.  8" sealed Peerless SLS subwoofers driven by 250 watts each.
4.  Single ended tube amp (4 wpc), Tripath amp (6 wpc) and NAD D3020 (30 wpc).
5.  Various stands, supports and the usual array of accessories.

This is a current list of potential configurations I would like to try:

1.  Single Super 3 wide baffle, with and without subwoofers.
2.  Single smaller enclosure, with and without subwoofers.
3.  Omni configuration, Wide baffle forward facing, smaller enclosure facing upward on top of main speaker.
4.  Omni configuration, Wide baffle forward facing, smaller enclosure facing upward on floor behind main speaker (LCS configuration).
5.  Omni configuration, smaller enclosure forward facing, wide baffle on floor behind main speaker.
6.  1.5 configuration, both speakers facing forward (smaller on top of larger).
7.  1.5 configuration, larger speaker facing sideways, smaller speaker facing forward (smaller on top of larger).
8.  Full range configuration, larger speaker facing sideways, smaller speaker facing forward (smaller on top of larger).

For 7. and 8.  I would experiment with lower driver facing outward vs. inward.  Due to my room limitations, I will not be experimenting with bipole/dipole configurations.

I plan on using an air core inductor to cross over the 1.5 way at 500hz as you prefer.  I'm assuming a nominal 2.5 mH inductor will do this.

I'd love to hear your thoughts on this.

R

[Ultralight]

Resurrecting a bit of an old query.  I am listening to a set of speakers (not Omega) that is technically really quite incredible and on paper, very impressive.  And doing critical listening, it really does impress.

However, after some hours, there's a bit of a fatigue - very slight. I wonder if it is due to phase.

Given that one of the selling points of full range speakers is their coherence, how does a 90 degree phase shift between the two drivers in a 1.5 system impact one's perception?  Does it not matter or does one now loose the purity of the phase coherence that is much touted for a full ranger?

I run a Omega bipole and just love it - but assume that the phase is still coherent on these....

Again, curious.

[FullRangeMan]

Passive crossover often shifts the phase between drivers.  Does an 'air core coil' do that in the Omega 1.5 setup? 

Curious...

UL

Crossovers are not passive component, either DSP or discrete all they modify the musical signal, inductors attenuates the high signal to the woofer and capacitor attenuates the low signal to the tweeter.

[mboxler]

Given that one of the selling points of full range speakers is their coherence, how does a 90 degree phase shift between the two drivers in a 1.5 system impact one's perception?  Does it not matter or does one now loose the purity of the phase coherence that is much touted for a full ranger?

I thought that an inductor's phase changes with frequency.  At low frequencies, the current lags the voltage by 90 degrees, but at the -3dB point it was 45 degrees.  From there, it approaches 0 degrees.  The two drivers are not always 90 degrees out of phase.

Am I incorrect?

Mike

[DaveC113]

I thought that an inductor's phase changes with frequency.  At low frequencies, the current lags the voltage by 90 degrees, but at the -3dB point it was 45 degrees.  From there, it approaches 0 degrees.  The two drivers are not always 90 degrees out of phase.

Am I incorrect?

Mike

Been a while since I looked at it and did xo math, but I think you're right, 1st order xo is 90 degrees but phase and attenuation vary with frequency as you approach the xo point.

IMO phase isn't an issue <700 Hz or so, my speaker is 400 HZ 1st order / 4th order and I've done a good bit of testing and phase at that frequency is not audible. I've also done a good bit of measuring and the measurements back this up. >7-800 Hz or so you can get audible and measurable destructive cancellation and this extends to 4-5 kHz or so.

I've talked about this with several other speaker designers and let's just say there's a lot of questionable information out there as a result of ideas that don't correlate with reality and the desire of a speaker company to have something to talk about wrt marketing.

[FullRangeMan]

Some CDs are recorded w/phase inverted 180º also some musical instruments have strange phase patterns.
There is a Fi phase recording by label but I fail to find it.

[FullRangeMan]

Had to upload it:

[BobRex]

Sheffield admitted that their early recordings were phase inverted.  It's printed on the Grusin jacket IIRC.

[Goosepond]

I thought that an inductor's phase changes with frequency.  At low frequencies, the current lags the voltage by 90 degrees, but at the -3dB point it was 45 degrees.  From there, it approaches 0 degrees.  The two drivers are not always 90 degrees out of phase.

Am I incorrect?

Mike

Hi Mike,

Well, I not only had to remove the dust from my EE books in college but also the cobwebs in my old brain. Here is what I recall.

Just for an inductor, current ALWAYS lags voltage by a 90 degree phase angle. But impedance is what varies with frequency.

Gene

[FullRangeMan]

Add a serial connection on some drivers and you will get a big mess.

[pstrisik]

Is this why 4th order is considered to have no or minimal phase problems?  (4 x 90 = 360 degrees).

[DaveC113]

Is this why 4th order is considered to have no or minimal phase problems?  (4 x 90 = 360 degrees).

Yup, but then you're not time aligned... My preference is to avoid speakers where this is critical because it so rarely works out even if the speaker is technically perfect. Ex, dome tweeters never sound great and rarely blend perfectly.

[FullRangeMan]

Musical signal before the XO are time & amplitude aligned, the less damaging XO is the 1ºorder, 4ºorder are 24dB/octave its the less musical XO, rarely used also more expensive than the 6dB.

[pstrisik]

Musical signal before the XO are time & amplitude aligned, the less damaging XO is the 1ºorder, 4ºorder are 24dB/octave its the less musical XO, rarely used also more expensive than the 6dB.

What about if the filtering is in the low level signal?  For example, my system has a Marchand active xover that uses 24db slopes with each output going to its own power amp.

[FullRangeMan]

What about if the filtering is in the low level signal?  For example, my system has a Marchand active xover that uses 24db slopes with each output going to its own power amp.

Electronic XO are all about ease of use and multiple freq cut options in one chassis, some say the sound is better than a regular discrete XO, but I never listen one.

[DaveC113]

Musical signal before the XO are time & amplitude aligned, the less damaging XO is the 1ºorder, 4ºorder are 24dB/octave its the less musical XO, rarely used also more expensive than the 6dB.

Actually 4th order are super-common and they work well with woofers, hard-coned drivers and more.

Almost all subwoofer amps have 24 dB xos built in, the Crown XLS has only 24 dB xos. Having a woofer, especially a subwoofer, playing audibly into the lower midrange is generally undesirable.