A time-aligned top end - Part II

[Al Klappenberger]

Thanks Dave. That driver doesn't look to bad but I am not sure the P-Audio version will have consistent quality. We need to do a serious search for good alternatives. With the ease of expanding the Eliptrac correctly down to 1.4 inch drivers the field is much more open than just 2-inch possibilities too.

Here's one I think deserves a serious look at: http://www.greatplainsaudio.com/downloads/390series.pdf

AL K.

[Rudy81]

Al, why are you unsure about the P. Audio quality? Do they have a bad reputation or have you read about problems? The drivers I have, AFAIK, are exactly the K69 driver. I know they no longer make that style driver for retail sale and have not heard the new model. Just curious as to your experience.

In my personal experience, I am getting very good results with a little EQ.

BTW, here is an REW plot I took when I first got the P. Audio driver. I took the measurement with the P. Audio 4525 horn. Unfortunately I don't recall the details of the measurement. I do know I took some measurements outside when testing my DBB build and I am assuming this is one of them.

[seti]

Thanks Dave. That driver doesn't look to bad but I am not sure the P-Audio version will have consistent quality. We need to do a serious search for good alternatives. With the ease of expanding the Eliptrac correctly down to 1.4 inch drivers the field is much more open than just 2-inch possibilities too.

Here's one I think deserves a serious look at: http://www.greatplainsaudio.com/downloads/390series.pdf

AL K.

1.4 I wouldn't mind trying one with my B&C DE82TN.

Here is a crude measurement. I'm no expert. I was just trying for ballpark. This is raw with no crossover or eq on a modified tractrix horn.

[Rudy81]

seti, what is the price range of that driver? Impressive frequency range.

[seti]

seti, what is the price range of that driver? Impressive frequency range.

I think I paid a little over $500 a pair. I had to contact b&c to find them but they ha a few cases left. I think they have an updated model now.

I'd like to have a spare pair.

[Al Klappenberger]

The B&C drivers all look like they are intended to be crossed over much higher than 400 Hz. The DE82 looks like it starts down way above 400 Hz on the official curves. Just because it's response will go that low doesn't mean it will do it without distortion. I found that out the hard way with the 1-inch JBL 2426h. I would need to test one and I think there are more logical candidates to consider first.

I may have an unwarranted bias against the P-Audio driver. I think I heard talk about them being inconsistent.

Al K.

[Guest David H]

Al, why are you unsure about the P. Audio quality?

The PMD-750 tests good, but the talk of driver changes made recently leave me a bit sceptical as well.

There are two 2" drivers that really interest me, one is the Faital Pro HF-200, and the other is the Radian 750ND. Both of these drivers appear reasonably flat 400Hz - 6Khz

Edit, the 1.4 inch GPA 390 looks excellent as well.

I am aware that there is a plethora of good drivers available, but I would like to find easily attainable new drivers choices that meet the requirments needed for use in the Heritage line.

Dave

[seti]

The B&C drivers all look like they are intended to be crossed over much higher than 400 Hz. The DE82 looks like it starts down way above 400 Hz on the official curves. Just because it's response will go that low doesn't mean it will do it without distortion. I found that out the hard way with the 1-inch JBL 2426h. I would need to test one and I think there are more logical candidates to consider first.

I may have an unwarranted bias against the P-Audio driver. I think I heard talk about them being inconsistent.

Al K.

PWK picked 600hz to cross it over. Using your ESN makes it even safer crossover point imo.

[Al Klappenberger]

Well..... The first candidate I plan to test is the Faital Pro HF200. Dave has arranged to have one sent to me, The spec sheet is attached. It's only rated down to 500 Hz but Dave was told it will work well down to 400 Hz. I plan to test the IM distortion. I think that is going to be the main factor in the choice. Frequency response extremes up high on it look good, but for a 3-way system with it mounted on a horn big enough to go down to 400 Hz, it's not very important!

Al K.

faital_hf200.pdf

[Rudy81]

Al, that seems like a nice choice, another driver with a very ample FR. Why does the spec sheet recommend a crossover of 900Hz minimum? I see it seems to be able to go well below that.

I will be closely following your testing.

I wish the e-mail notification system on this forum would start working again. Anyone else not getting e-mail notification of a response when you are subscribed? Used to work for me, but for the last few days it has not been working at all.

[BE36]

Of course I will need to keep the review samples.

I see you have done this before.

I used to love writing reviews, after about 5 year it became one big blur.

Dave Harris

No, I have not done this before, just read enough reviews. . .

[Al Klappenberger]

Rudy,

"Why does the spec sheet recommend a crossover of 900Hz minimum? I see it seems to be able to go well below that"

This is the key to what this is all about. A lot of these drivers will specify the crossover with an asterisk * footnote. When you read it, it will tell you something like 12 dB / octave minimum filter. This is telling you that it can't handle even moderate low frequency energy without distorting. The alternative is cross it over higher with a gentle slope filter or use a steeper slop if you need to go down in frequency. The fact that it will have good response down to 400 Hz doesn't tell you what will happen when a sound at 200 Hz (an octave down) that is 12 dB down the filter slope hits it! It can even crash the diaphragm into the phase plug! Most likely it will just generate distortion consisting of harmonics that don't belong there that you can hear. Not everybody is going to run the driver down to 400 Hz with a filter that nails 350 Hz by 20 dB like my ES400. A typical 2nd order filter (12 dB / octave), the filter in the stock Khorn AK-3 network for example, won't hit 20 db until you get down to 130 Hz! That is why drivers that seem to go low in frequency really can't be used very low. They will just distort.

Other drivers, like the 1-inch JBL 2426h that I use on my Belles will distort even at 400 Hz. This is what I will be testing for. It needs to be clean at 400 Hz to even be considered. That means it will operate down to 400 Hz with a better chance of handling the extreme lows. A steeper slope filter my still be required, That is the reason I recommend the B&C DCM50. It is designed to go down to 400 Hz with a 12 dB / octave filter.

Al k.

EDIT: I just remembered that I made up a series of overlaid computer plots showing the relationship between filter slope and how low a driver can be operated. It's below.

[Guest David H]

THE FAITAL PRO HF200 2" HF DRIVER HANDLES A POWERFUL 80 WATTS RMS @ 900HZ & 160 WATTS PROGRAM POWER @ 900HZ FEATURES A LIGHTWEIGHT NEODYMIUM MAGNET SYSTEM THAT WEIGHS 7.05 LBS. TITANIUM DIAPHRAGM FOR A CRISP HIGHS AND STRONG MIDS LOW DISTORTION & FLAT FREQUENCY RESPONSE FROM 700HZ UP TO 20KHZ

This driver rated at 900hz for its power handling capabilities, expect the max power rating at 400 hz to be less than half it's rating at 900hz.

Ok, ALK's answer is better...

I would like the Faital pro driver will work well for this application, but I am certainly not getting my hopes up.

Dave

[Rudy81]

Al. Thank you for that explanation, it makes total sense now. I currently use my Ashly crossover at the steepest slopes of L-R 48dB. I am currently crossing my DBB mains pretty high, around 700Hz, but will now look at the P. Audio driver specs again just for fun.

I hope you guys can find a suitable 2" driver, reasonably priced, that can dow what we all want.

[SSnyder]

Q- has any one of you run DBT for time alinegment or just theoryiezing???? I'm am very skeptacil

THERE IS NO TIME ALINGEMENT IN CONCERT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[Guest David H]

Q- has any one of you run DBT for time alinegment or just theoryiezing???? I'm am very skeptacil

The B&C DCX-50 is a coaxial driver, meaning the Tweeter is located inside the midrange therefore the sources are the same distance from the listener. Therefore yes it is time aligned.

Good info here. http://www.gain11.com/ConsumerAudio/TimeAlignmentPartI/tabid/177/Default.aspx

THERE IS NO TIME ALINGEMENT IN CONCERT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I am not sure what you are getting at here, but there is a difference between production and re-production. Unless you are Milli Vanilli.

Dave

[Coytee]

I am not sure what you are getting at here, but there is a difference between production and re-production. Unless you are Milli Vanilli.

[Y] Good one.

I might ask a rhetorical question.... are we "time aligning" or "signal aligning"? How does one "align time"?

[6]

I'd suggest that we are really trying to align the signal in time, no?

This has always caught my eye, much like someone who says "this item costs TEN TIMES LESS than that item!"

Really?

[]

[Guest David H]

I might ask a rhetorical question.... are we "time aligning" or "signal aligning"? How does one "align time"?

Ok

First things first, the term “time alignment”, is a trademarked term owned by renowned speaker designer Ed Long (E.M. Long & Assoc.). Sometimes referred to as signal alignment, “time alignment” has stood the test of time as the most commonly associated and accepted term when discussing the topic of alignment as it pertains to speakers (or audio in general). It’s simply more intuitive as we are contemplating the physical alignment of two or more signals in time. In part I we will discuss exactly what “time alignment” is and how it applies to system design. In part II we will explore the many ways in which you achieve proper alignment.

[Al Klappenberger]

I received the sample Faital Pro HF200 driver a while ago. I'll be starting a new thread about it.

Al K.

[Arkytype]

Al, et al----

Perhaps a little math will help us understand the problem with trying to use a mid or tweeter driver below its low frequency design limit.

Let's say one measures 100 dB SPL 1 meter from a mid driver/horn combination fed with a 1,600 Hz sine wave. At 800 Hz for the same acoustic output of 100 dB SPL, the driver diaphragm excursion will be?

a) the same

halved

c) doubled

d) quadrupled

The answer is d. For every halving of frequency, the excursion quadruples. So, going from 1,600 Hz to 400 Hz would require the driver diaphragm to move 16 times farther!

An extreme slope network will go a long way protecting a mid or tweeter driver from low frequencies which are outside the bandwidth of the respective driver.

Lee