Wavecor FR070WA01

[planet10]

Originally Posted by soundaatma

How would you compare this situation to using a crossover point ABOVE the critical hearing range (guess above 4-5 khz). All your points favoring a low crossover point would be mostly against using a higher than 4Khz XO... I am intrigued by the offerings from Zu , Tekton and Decware Mini, that use a high XO point employing a "helper" tweeter with an extended range woofer.

A good question. What follows may be a bit "stream of conscious"

10 years ago there wer efew if any "full-ranges" that reached above the highest octaves. If you were missing the air, you needed to fill in with a super-tweeter (ST). We did a lot of experimenting with this. An example.

To make these systems truly full-range you still needed to add a woofer (the so-called mostly FR system). In this situation, the ST usually had just a single cap on it, with the FR XO being its natural roll-off. This is still a common approach. A recent example that has had lots of positive comment is Steve's FF225wk/FT17 Metronome (the thread takes a while to get there)



This concept has been used lower down in frequency ever since people started adding tweeters to speakers. One of the most enjoyable conventional speakers i owned was a small set of Royds with a single cap as an XO.

Due to the physical size of the drivers, the tweeter can never get close enuff to the driver below, so you'll have combing. Fortunately the ear is not so sensitive up this high and the brain expects combing so the sonic effect is not nearly as bad as the graphs would suggest.

As well adding the ST doe not give an improvement in performance for the other driver. In a FAST relieving the FR of heavy lifting improves its mid-top performance -- this at the cost of a reactive component (althou this can be turned to advantage when it is a cap on the imput of a separate MF/HF amp).

Now if you want to have a system with a ST do bass without making it a 3-way, then the FR needs to be large. And these, in general, just don't have the DDR of a small driver. Often these big drivers also have a whizzer, which is its own can of worms.

Let's examine the sharing of the work load. If we assume the goal is 20-20k, we have to cover 10 octaves.

In terms of work sharing the tweeter at best covers 2 octaves, an octave or less is common. So that larger driver has to cover the rest. It is actually unlikely that this driver will actually reach 20 Hz without compromise, so if you want true FR you need a subwoofer for the bottom octave of so.

For the equivalent load share on a FAST the FR would XO at 80 Hz, the woofers (which could be subwoofers) doing the bottom 2 octaves. Since this likely still means a fairly large FR (or a limiting of dynamics or ultimate loudness) which often won't reach as high. More common is an XO 150-300 some Hz. At 300 Hz the woofers handle the bottom 5 octaves, the FR the top 5. If XOing this high, the woofers -- if they blend well with the FR -- likely can't actually reach 20 Hz, so add that subwoofer back in for the lowest octave. At 150-160 the woofer does 4 octaves, the FR 6. That is practical. Also in that consider that, in average, 300 Hz is considered the point where half the energy is below & half above. If one isn't doing movies, and we consider Low E on the bass is 42 Hz, a target LF of just under 40 Hz is nor unreasonable.

Both Tysen, and the EL166 MTM FASTs we have done, have exceeding out expectations.

What is heralding a surge in interest in FAST is that in the last 10 years, due to both a resurgence of interest in FRs, and to the development required for computer multimedua systems, we now have a growing number of FRs that reach 20k and above. Couple that with all those midbasses designed to XO to a dome or ribbon tweeter, we have a rich environment for the development of FASTs.

Compromises are a fact of life... you picks the ones that least compromise your situation and needs.

All that said, one of the projects high on our list is the EmKen, a 12" Eminence extended range with a helper tweeter. Originally conceived for light duty PA work with hifi pretensions, it is getting good press from the sole beta builder.

dave

[soundaatma]

That was certainly a very insightful and experienced reply. Thanks Dave. I just spent most of the night looking at threads on your Tysen and MTM.

From what I gather, irrespective of speaker sensitivity, generally speaking, a design requirement of high max SPLs in larger listening environments would gravitate towards using high power handling wide-range PA drivers with helper horn tweeter and high XO . While OTOH, intimate small environments asking for detail and nuanced sound and not high max SPLs, would be better served by paper-light and fast FR drivers components with helper woofers and a low XO point.

I look forward to your Emken project. BTW, given the uneven high frequency response of the Beta 12LTA, likely due to the whizzer cone, is it worth trying the 12LCX which is essentially the same driver without the whizzer and an acoustically transparent dust-cap for a coaxial tweeter.

[planet10]

Ladies & Gentlemen - The Emken

dave

[tuxedocivic]

Another reason to use a FAST rather than cross over high, is a more uniform horizontal directivity match. Dave alluded to it, but I feel it deserves a highlight.

[fakeout]

HOLY CRAPOMOLY! No one told me this existed!

http://www.diyaudio.com/forums/1833349-post32.html

Good grief, now if someone wanted to use say a Fostex FF85WK, what kind of subwoofer or woofer would you use?

By the way, is there any advantage to having the sub or woofer pointing in the other direction? Do you have them pointing toward each other or in opposite directions?

What kind of power of amp would you need?

[planet10]

Originally Posted by fakeout

Good grief, now if someone wanted to use say a Fostex FF85WK, what kind of subwoofer or woofer would you use?

That one specifically for SDX7. Tysen uses close to the max sealed volume for the SDX7 0.5<Q<0.58, this stubby version shrinks the volume for the woof to butterworth Q-0.707

By the way, is there any advantage to having the sub or woofer pointing in the other direction? Do you have them pointing toward each other or in opposite directions?

Side mounted woofer allows narrower baffle. Mirror imaged woofs in or out depends on what works best in your room. With the XO in Tysen, on the outside with heavy toe-in.

What kind of power of amp would you need?

2 stereo amps + PLLXO. Good ones prefered.

dave

[zman01]

Originally Posted by tuxedocivic

But then you should still expect to use a subwoofer to handle the 20hz stuff typical of modern movies.

Do many of the cheaper commercial subs even do <20 Hz??

Originally Posted by tuxedocivic

Currently I use a single 8" subwoofer under my couch (seriously compromised due to space restrictions, soon to change hopefully). A typically movie like Inception absolutely pounds it, even on mild LFE parts. I constantly bottom it out. Constantly. It's laughable really. It'll be no different for a FAST that uses a couple 6.5" woofers or something.

What's your SPL? You think it's a bad design or the driver that's causing bottoming out so frequently?

[planet10]

Originally Posted by zman01

Do many of the cheaper commercial subs even do <20 Hz??

No, probably none of them.

dave

[tuxedocivic]

Very few commercial subs do 20hz. They employ a high pass below tuning I imagine. They also tune high and use small cabs. This gives them power handling and sound "boomy" in order to attract customers. Higher ends subs, true subs, can do it. See the Submersive for example.

The sub is DIY, but it's an 8" in a 40L cab tuned to 22hz. So there is lots of woofer travel right around 30hz and absurd amounts of travel below 20hz. It's poorly designed because it can't handle lots of power, the kind a movie like inception requires, but it's well designed in that at moderate levels it's a suitable box and tune for that driver (ie. fairly flat). My listening SPL is probably peaks of 90db at the LP. But consider that a Dolby track would demand the subwoofer produce 100db peaks at the LP for that. That's pumped up, but not crazy. But there aren't many 8" drivers that can produce 100db peaks below 40hz. Lots of movies do. Dolby's reference is 115db peaks at the LP down to below 20hz. That takes a lot of subwoofer.

My sub is fine for most any music. I have a disc (Brooklyn Funk Essentials) which causes my sub to have a fit. Worse than a lot of movies. Tons of 30hz content.

[fakeout]

lol, what kind of sub does it take then to watch movies with a full ranger? Assuming someone wanted to use a Fostex FF85WK or other "competent" full ranger, which sub would you use? Would it be 10 inches or more? Is there a happy medium in sub size, 12 inch, 15 inch?