A time-aligned top end - Part II

[sfogg]

Dave,

"Using a single driver for the top end is basically the same premise as
as a time aligned top end. In a time aligned top both drivers are same
distance from the listener or a delay has been used so the sounds from
the individual drivers reach the listener simultaneously."

Not quite the same. When you electrically or physically time align two drivers you are still aligning them for only one plane in space. Anywhere not on that plane is still not time aligned and will therefor comb.

What you hear at the listening position is a composite of what occurs on-axis as well as off-axis. It is why some designers work very hard on the power response of the system. If you are combing off axis that still will alter what you hear at the listening position.

When you replace two drivers with a single driver you are eliminating that combing everywhere in the room.

Shawn

[Rudy81]

Al, the P. Audio horn I have been using with my current driver likely has some of the distribution issues you allude to. However, in my listening room, I really have not noticed any major issues other than the fast rollof of my current driver around 13kHz. In your average home listening room, do you think the horn distribution anomalies are large enough to be noticeable in such a 'small' environment?

[pzannucci]

Bob,

You torture tested the drivers but many may not really fall apart with this testing. The key is, how do they sound? Clean and realistic?

I've found that some of these drivers that do go to 18K just don't sound realistic at higher frequencies. They still need a tweeter to give clean and natural highs.

It would be great if this this driver can do that.

[BEC]

Bob,

You torture tested the drivers but many may not really fall apart with this testing. The key is, how do they sound? Clean and realistic?

I've found that some of these drivers that do go to 18K just don't sound realistic at higher frequencies. They still need a tweeter to give clean and natural highs.

It would be great if this this driver can do that.

My contribution to the testing so far was just to take the risk of crossing to these HF-200 drivers at 400 hz and see if they performed well crossed that low with a rather quickly put together 2nd order crossover. They passed that test very well. I am also working throught my test tracks that consist of a wide range of different music compiled on 4 CDs to see how these drivers sound compared to how I know these tracks should sound.

So far I am pleased with the sound. I am very sensitive to how the highest frequencies sound. These HF200 drivers are the best sounding 2 inch drivers I have yet heard with the possible exception of the TAD 4002. I wish I had a TAD 4002 to compare to these, but even if I did, not sure I would risk trying it at the 400 hz crossover frequency I am using for the HF200.

Tomorrow, I should have a different, more sophisticated, and hopefully better crossover to try on these.

Bob Crites

[Rudy81]

I spent some time today comparing the published response curves of my current driver (http://www.usspeaker.com/paudio%20bmd750-1.htm) and the HF200 (http://www.faitalpro.com/img/products/schede/CD/HF200/HF200_datasheet.pdf). After carefully looking at the results, the drivers are not all that different. The HF200 seems to perform better near 400Hz, which is what Khorn owners need. However, they seem rather similar in the higher frequencies.

In my case, I have been considering the HF200 for what I thought was its better top end performance....but the graphs are deceiving when just looking at them. Close examination of the results shows both drivers to be close in high end performance. So, I will have to keep looking into this issue before I change drivers since I am not as concerned with performance near 400Hz since I use the DBB bass bin.

Am I way off here, or does that seem reasonable?

[Rudy81]

So far I am pleased with the sound. I am very sensitive to how the highest frequencies sound. These HF200 drivers are the best sounding 2 inch drivers I have yet heard with the possible exception of the TAD 4002. I wish I had a TAD 4002 to compare to these, but even if I did, not sure I would risk trying it at the 400 hz crossover frequency I am using for the HF200.

Tomorrow, I should have a different, more sophisticated, and hopefully better crossover to try on these.

Bob Crites

Bob, have you had a chance to do a similar comparisson with the K69 (or P. Audio BM-D750)?

[BEC]

I don't think I have ever heard the K-69 without EQ. With EQ, it can do a respectable curve. Looks pretty rough raw.

By the way, the only reason I am testing at 400hz is to see if the Faital Pro HF200 is practical for use in the Khorn. I will probably be crossing higher than that for the Cornscala. No reason to run it that low for the Cornscala.

Bob

[Rudy81]

Bob, I fully understand why the testing is focusing on 400Hz. One driver I use is paired with a La Scala bass bin and the others with the DBB bass bins, which cross higher as well.

I'm just trying to decide if the HF200 will make enough difference in my setup vs. the P. Audio driver to justify the investment.....I'm sure tradeoffs like everything else....sure is tempting though.

[mikebse2a3]

In my case, I have been considering the HF200 for what I thought was its better top end performance....but the graphs are deceiving when just looking at them. Close examination of the results shows both drivers to be close in high end performance. So, I will have to keep looking into this issue before I change drivers since I am not as concerned with performance near 400Hz since I use the DBB bass bin.

Am I way off here, or does that seem reasonable?

Rudy I think you are right in being cautious based on the fact that the graphs aren't of sufficient resolution and the other variables that have been mentioned before.

Now if you get a chance to hear one with the option to return it then the risk isn't so great.

mike tn

[Rudy81]

mike, agreed. What I need to do is to wait and see what the reviews on sound quality say. Also, I'm sure there will be further testing in the near future. However, patience has never been one of my virtues.

[Guest David H]

I'm just trying to decide if the HF200 will make enough difference in my setup vs. the P. Audio driver to justify the investment.....I'm sure tradeoffs like everything else....sure is tempting though.

We'll have a bit more info soon. JWC is going to run the curves on the K-69 with the Eliptrac 400. I am anxious to see how it does.

Dave

[Guest David H]

I have this set of horns going out to a forum member using I believe a Beyma CP-800 with Jubilee's.

[ClaudeJ1]

Nice piece of work here, both gentlemen.

[ClaudeJ1]

How about the K-69... or the EV DH1A

From what I understand the K-69 and the P-Audio BMD750 is that they are virtually the same driver.

I only listed drivers readily avaialble for retail purchase. Are the EVDH1A avaialbe?

I am sure there are alot of capable drivers I missed, the ones listed are just ones I thought might be capable for 2-way use.

Dave

I have JBL 2446 drivers ($till available new) and some mint DH1A, one of which was tested by Roy Delgado at a Pilgrimage in Indy. He said those were really good drivers.........unfortunately you can only get them used, and often times, after they have been overdriven in churches with live bands instead of just orators.

[Rudy81]

I'm just trying to decide if the HF200 will make enough difference in my setup vs. the P. Audio driver to justify the investment.....I'm sure tradeoffs like everything else....sure is tempting though.

We'll have a bit more info soon. JWC is going to run the curves on the K-69 with the Eliptrac 400. I am anxious to see how it does.

Dave

I sure hope JC publishes his results on here.

[Guest David H]

I'm just trying to decide if the HF200 will make enough difference in my setup vs. the P. Audio driver to justify the investment.....I'm sure tradeoffs like everything else....sure is tempting though.

We'll have a bit more info soon. JWC is going to run the curves on the K-69 with the Eliptrac 400. I am anxious to see how it does.

Dave

I sure hope JC publishes his results on here.

I got message from JWC yesterday that he had to get different mounting hardare for the drivers, I suspect we will see some curves as early as this weekend.

Dave

[Al Klappenberger]

The Faital Pro and B&C drivers are both made in Italy. They require metric hardware. The HF200 needs studs about two Inches long and nuts that are provided with it. B&C isn't that nice. You need to provide them yourself, but they are just simple metric screws.

Al K.

[Chris A]

Not quite the same. When you electrically or physically time align two drivers you are still aligning them for only one plane in space. Anywhere not on that plane is still not time aligned and will therefore comb...What you hear at the listening position is a composite of what occurs on-axis as well as off-axis. It is why some designers work very hard on the power response of the system. If you are combing off axis that still will alter what you hear at the listening position...When you replace two drivers with a single driver you are eliminating that combing everywhere in the room.

FYI: Note that this discussion is along the lines of a single-driver thinking such as a "one-way" Fostex driver mounted on a back-horn enclosure. The obvious tradeoff is largely increased FM distortion due to increased motion of the diaphragm to cover the entire lf range, the limiting effects on the output SPL, and the built-in backwave delay problem that really cannot be compensated.

Tannoy mounts two or more drivers co-axially. The down side is the dramatically increased driver expense (apparently) and driver design tradeoffs required in order to package a tweeter coaxially with a midrange/woofer driver. Tannoy mounts their hf section inside a cone that has horn-like loading characteristics, but this means that you will be stuck with a non-horn-loaded woofer with its attendant 25 dB increase in THD (quoted per PWK interview with Bruce Edgar...), the FM distortion effects of the woofer cone/horn moving in relation to the mf/hf driver, and the built-in backwave delay problem that really cannot be compensated.

A third approach is to mount the drivers in one horn - like the Danley Synergy series using a rectangular conical horn profile with several horn entry points that are non-axial. The Danley horn mountings result in driver crossings that are < 1/4 wavelength at the crossing frequencies. This doesn't eliminate the diffraction issues (a.k.a., "comb filtering"), but it minimizes the effects on the resulting system performance, especially when used with active or passive crossovers that supply appropriate attenuation, driver delay and phase compensation.

A fourth approach is a conventional 2-way horn-loaded arrangement with the crossover below about 550 Hz (thus minimizing the effects from a psychoacoustics standpoint - i.e., less than 1/4 wavelength of the separation distance of binaural hearing) with digital delay compensation using an active crossover... []

Chris

[ClaudeJ1]

Not quite the same. When you electrically or physically time align two drivers you are still aligning them for only one plane in space. Anywhere not on that plane is still not time aligned and will therefore comb...What you hear at the listening position is a composite of what occurs on-axis as well as off-axis. It is why some designers work very hard on the power response of the system. If you are combing off axis that still will alter what you hear at the listening position...When you replace two drivers with a single driver you are eliminating that combing everywhere in the room.

FYI: Note that this discussion is along the lines of a single-driver thinking such as a "one-way" Fostex driver mounted on a back-horn enclosure. The obvious tradeoff is largely increased FM distortion due to increased motion of the diaphragm to cover the entire lf range, the limiting effects on the output SPL, and the built-in backwave delay problem that really cannot be compensated.

Tannoy mounts two or more drivers co-axially. The down side is the dramatically increased driver expense (apparently) and driver design tradeoffs required in order to package a tweeter coaxially with a midrange/woofer driver. Tannoy mounts their hf section inside a cone that has horn-like loading characteristics, but this means that you will be stuck with a non-horn-loaded woofer with its attendant 25 dB increase in THD (quoted per PWK interview with Bruce Edgar...), the FM distortion effects of the woofer cone/horn moving in relation to the mf/hf driver, and the built-in backwave delay problem that really cannot be compensated.

A third approach is to mount the drivers in one horn - like the Danley Synergy series using a rectangular conical horn profile with several horn entry points that are non-axial. The Danley horn mountings result in driver crossings that are < 1/4 wavelength at the crossing frequencies. This doesn't eliminate the diffraction issues (a.k.a., "comb filtering"), but it minimizes the effects on the resulting system performance, especially when used with active or passive crossovers that supply appropriate attenuation, driver delay and phase compensation.

A fourth approach is a conventional 2-way horn-loaded arrangement with the crossover below about 550 Hz (thus minimizing the effects from a psychoacoustics standpoint - i.e., less than 1/4 wavelength of the separation distance of binaural hearing) with digital delay compensation using an active crossover...

Chris

this is a very good summary of many trade offs being made in the horn world. Yet, this new effort with the Elliptical Tractrix looks promising as another good choice on the carousel, eh?

[pauln]

Just a few question about time alignment and measuring the distance correction between two horns...

Doesn't the horn operate by tranforming high pressure high velocity at the throat into low pressure low velocity at the mouth?

Is the velocity difference because the driver sees the small throat as a confined volume and thereby delivers into high pressure?

Is the velocity a real elevation in the speed of sound within the high pressure end of the horn that is normalized at the mouth?

Does this mean the wavefront is spending all of its time traveling the length of the horn at supersonic speed, slowing to match normal sonic speed at the mouth?

If so, won't this make the alignment distance shorter than simple driver to driver length, and vary also as a function of amplitude?

In a typical mid horn/tweeter set, wouldn't virtually all of this shortening be occuring in the midhorn?

Does this allow the midhorn wavefront to catch up somewhat to the tweeter?

Reason I ask is that I see a lot of mention that the tweeter driver is for example 20 inches forward of the mid driver... implying that length of 20 inches is the correction to be made by repositioning for time alighnment, but I'm wondering if that length is overstated because of the time the wavefront in the mid horn might be going supersonic. If one knew how much faster initially and the rate of deceleration through the horn it might be that the corrective length was "exponentially" less?

In other words, if sound within horns is supersonic, wouldn't time alignment need to synchronize wavefront departures from the horns' mouths rather than geometric alignment of drivers?