Jericho horn speakers with Audio Nirvana Super 8" - diyAudio
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Old 23rd April 2009, 01:47 PM   #1
hagr is offline hagr  Norway
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Default Jericho horn speakers with Audio Nirvana Super 8"

Hi!

Soon I'm going to start building my pair of Jericho horns, and I'm wondering: How will it be if I use the Audio Nirvana Super 8" drivers instead of Fostex FE206E/FE208? I haven't heard any of them yet, but i have read that the AN's are better! I also hope to avoid use of correction filter.

Hope you can help me

Harald

(Sorry for my bad English)
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Old 23rd April 2009, 03:27 PM   #2
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Greets!

Your English grammar is better than many (most?) American's thanks to our pitiful government school system, sorry to say.

Based only on comparing published specs (which is probably worthless since A-N specs are apparently pure fiction), the cast version of the Super 8 MIGHT can be tuned 'close enough' (rear chamber, throat not optimal), but the basic Super 8 requires a much bigger rear chamber, throat, ergo much larger horn for a given cut-off.

Since typical 'full-range' ('FR') driver back loaded horns (BLH) are just extreme bass reflex (BR) alignments, the quick way to tell if a driver will work in a given BLH is to compare it's max flat alignment (typical box design default simulation) and the closer the box volume (Vb) and box tuning (Fb) is to the horn design's driver, the better chance it can be made to work, though best if the driver you want to use has a slightly smaller Vb and higher Fb since it's better to reduce rear chamber Vb and damp down any excessive HF band-width (BW) than use a contour filter to flatten any excessive mid-bass/lower mids and still probably have an audible dip in the acoustic XO BW (transition from horn to driver output).

Note that if driven with a high output impedance, then the impact of its series resistance on driver Qts (raises it) must be accounted for before making any comparisons.

GM
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Old 23rd April 2009, 04:31 PM   #3
hagr is offline hagr  Norway
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Thanks for answer

When do you think the roll-off will be with the AN driver, then? deepbass is really not that important to me, and if I only need to sacrifice a couple of Hz's, it's probably worth it

Have read some reviews on the AN drivers, and I am in love!

I'm also going to build a couple of small floorstanding speakers, using the Super 6,5 drivers

Harald
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Old 24th April 2009, 03:43 PM   #4
GM is offline GM  United States
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You're welcome!

Don't know, haven't reverse engineered it, but its response shouldn't have much, if any, audible difference than with whatever driver it was designed for if you use a similar spec unit.

GM
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Old 26th April 2009, 10:18 PM   #5
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You said something about bigger rear chamber. The jericho horn is pretty easy to modify like that. How much bigger will it need to be? It's also simple to tighten the throat a bit

I'd really like to use the AN drivers in this construction!

Harald
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Old 26th April 2009, 10:18 PM   #6
hagr is offline hagr  Norway
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I sent an e-mail to Commonsense Audio asking if the AN driver would be suitable for the jericho-horn, and here is what they replied:

Hello,

The free air resonance of Audio Nirvana and Fostex drivers are almost the same, so they work in the same cabinets.

In any event the Fostex FE206E has too much excursion (or Xmax) for most horns. It is plus or minus 1.5 mm.

For comparison, Lowther drivers are plus or minus .75 mm and Audio Nirvana are plus or minus 1.0 mm.

And the midrange and highs of Audio Nirvana are many times superior to Fostex.

Regards, David

Harald
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Old 26th April 2009, 11:01 PM   #7
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Speaking strictly as a newb, Fs is just one parameter. For two drivers to be comparable, you have to look at more than just Fs. What about Vas, Qts, the frequency response, the impedance curve etc.?

Also, I don't think a driver can have "too much" excursion, especialy when that excursion figure is already somewhat miniscule.

But let's see what others say! This is definitely an interesting undertaking, Harald, and I look forward to reading more.
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Old 27th April 2009, 10:17 AM   #8
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I'm afraid David's reply indicates little other than his ignorance WRT basic principles of horn theory and design, which can probably be extended to other box design too, judging from what I've seen of the CSA BR cabinets.

Quote:
The free air resonance of Audio Nirvana and Fostex drivers are almost the same, so they work in the same cabinets.
Utter nonsense. They might fit, but that's about as far as you can take it. You drop one into a box designed for the other, it's not going to be optimal. Two little facts:

1/ Fs, as pointed out, is but one aspect of a driver's performance or behaviour. If you judged solely by that, then the Visaton B200 (measured Qt about 0.9, 130 litre Vas) would work just fine in the Jericho. Which naturally it won't -the response will be so bad, I prefer not to think about it, and shall have to go and lie down quietly after typing this. And

2/ For the sake of interest, once you get to ~optimal horns, Fs really isn't a matter of concern anyway; you can take a little 3in FF85K (Fs of around 130Hz) down to 30Hz if you've got the space. Quite why you'd want to is another matter entirely, but you get the idea.

Quote:
In any event the Fostex FE206E has too much excursion (or Xmax) for most horns. It is plus or minus 1.5 mm.
Rubbish, and true, respectively. Most BLHs like the Jericho are simply extreme BR boxes (as GM has pointed out above), and therefore, a reasonable amount of linear travel is both acceptable, and actually rather useful to have. The 206 does, however, have a 1.5mm Xmax each way, so at least that's a correct piece of information. More of which in a minute.

Quote:
For comparison, Lowther drivers are plus or minus .75 mm and Audio Nirvana are plus or minus 1.0 mm.
Duff gen (again). Lowther drivers have 1mm travel each way (I was talking to someone from the factory about this very point a few months back); exactly the same as the ANs. However, we're talking Xmax here, i.e. the linear travel of the driver, not the limit of mechanical travel; in the latter case, the Fostex & AN are much of a muchness, in the Lowther's, a little less. All are rather more than their Xmax, which is neither here nor there in the context (I presume) David is talking about.

Quote:
And the midrange and highs of Audio Nirvana are many times superior to Fostex.
Oh yeah? Says who? Ahhh, of course; the man selling them, who has a financial interest in the matter as they are 'his' drivers. Not exactly an objective party, wouldn't you say?

Caveat emptor!
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Old 27th April 2009, 02:12 PM   #9
hagr is offline hagr  Norway
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The Vas and the QTS of the two drivers are pretty different, but I've been told that in a BLH, the frequency and the Fs is the most important, and since those are pretty equal, I hope the AN drivers will work fine. I'm probably going to start with a pair of the Super 8's, and if they don't give good enough results, I buy a pair of FE206E's too.

I can always build a set of 2.8 enclosures for the Super 8 drivers as well

Harald
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Old 27th April 2009, 02:30 PM   #10
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I don't know who told you that, but as I pointed out above, if you followed that logic, you could just stuff any driver into a horn and expect it to work if it happens to have an Fs near that of the unit it was designed for. It doesn't work like that I'm afraid. Look at the attached for sake of example. This is the modelled FR of a horn with three different drivers fitted, all of which have roughly the same free air resonant frequency (disregard everything over 250Hz BTW). The top shows the response with the design driver. The middle plot is with another unit, with somewhat higher Q & Vas. The lower plot is for a driver with a still higher Q and Vas. What do you think?

The cast frame AN might work passably, but the LF will be weak compared to what it should be. The other AN units will be worse. I know you don't want to hear it, but you can't circumvent the laws of physics, and hoping that something might work in the face of basic principles isn't going to do you any favours, although it will potentially waste a lot of your time and money for no good reason. BTW, the Jericho, IIRC, was designed for the defunct Fostex FE208Sigma (not the 206, or the current FE208ESigma).
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