Depends on how you define a BLH. They won't be ideal for very long ones, as they don't appear to have sufficient motor-power to overcome the horn's damping (which will cause HF losses). But you might get away with something more reasonably sized. Depends on what compromises you can live with. One interesting phenomenon frequently seen with high-end FR drivers is that owners may have a very specific philosophy, so aren't especially concerned if there are issues elsewhere that might drive someone else, who doesn't share the same approach, spare. YMMV.
rcdaniel said:
Actually, the lower voltage settings are typically ideal for BLH loading due to the need to keep the horn/driver acoustic XO below 250 - 400 Hz (Fh) depending on who you ask (FWIW I prefer the lowest practical) to keep out of phase comb filtering below our acute hearing BW, so Qes = 2*Fs/Fh, ergo for a 85.2455 Fs in this range, Qes = 0.682-0.426 is desirable. If the VC tends to run warm during normal playback, then this will further lower these values, so ideally the design should be based on them. There's a reason the pioneers of audio used either wide cabs or corner loading rather than today's typically pencil thin ones, it was necessary to support a low acoustic XO point.
Folks in recent decades measured early horn drivers and assumed that since they had powerful motors and low moving mass (Mms), this was demanded for horn all design, but they didn't look at the rest of the sound system, which either used impedance matching amps or ones with up to 20 ohms of output impedance, either of which dramatically increases Qes, Qts.
WRT to design efficiency, best to use the calc'd value since it's the one the box math is based on:
n0 = 9.6352*10^-10*Fs^3*Vas(liters)/Qes
SPL = 112.018+10*Log(n0)
So using these:
Revc= 14.8465 ohms
Fs = 85.2455 Hz
Qes = 0.4718
Vas = 7.1865 L ( 0.2538 ft^3)
Efficiency = 0.9096 %
Sensitivity= 95.5885 dB @1W/1m
I get 0.90915%, so factoring in I use a different SoS and air pressure than most software designers the 0.9096% 'measured' is spot on. At a calc'd ~91.6 dBa/W/m Sens though and factoring in this is nominally a 16 ohm driver, the voltage sensitivity the amp will 'feel' is only ~88.59 dBv/2.83 V/m making the 95.5885 dBa/W/m spec nonsensical to me.
GM
Thanks very much GM, Scott, and Chris for clearing up my misunderstandings - much appreciated. 
I look forward to the day when I can dedicate more time to learning and understanding (some of) the science behind 'speakers and amplifiers. Until then (and even then), I am very glad that you guys take time out of your busy lives to contribute here.
Cheers
I look forward to the day when I can dedicate more time to learning and understanding (some of) the science behind 'speakers and amplifiers. Until then (and even then), I am very glad that you guys take time out of your busy lives to contribute here.
Cheers
I'd say "I'm not even in the same league as Scott & Greg where loudspeaker design knowledge is concerned," except that it would be more accurate to say I'm not even in the same sport. They're on the playing field whilst I'm peddling beer and hot dogs in the stands. But I do have a bit more time these days, thanks to the effects of the subprime loan crisis sending my industry into a serious downturn, so I'm glad to be able to pass on bits and pieces of information from Japan when I can. I get a lot of vicarious pleasure from seeing what others are doing, both with Feastrex and other products.
-- Chris
-- Chris
rcdaniel said:
You're welcome! Unfortunately in my haste to post before having to deal with a bill some medical office is trying to erroneously hold me accountable, I didn't do a good job of editing or completing some thoughts:
Actually, the lower voltage settings are typically ideal for BLH loading due to the need to keep the horn/driver acoustic XO below 250 - 400 Hz (Fh) depending on who you ask (FWIW I prefer the lowest practical) to keep out of phase comb filtering below our acute hearing BW, so Qes = 2*Fs/Fh, ergo for a 85.2455 Fs in this range, Qes = 0.682-0.426 is desirable. If the VC tends to run warm during normal playback, then this will raise these values, lowering 'Fh' further, so ideally the design should be based on them, though of course with field coil drivers you can just dial up the voltage. There's a reason the pioneers of audio used either wide cabs or corner loading rather than today's typically pencil thin ones, it was necessary to support a low acoustic XO point.
Folks in recent decades measured early horn drivers and assumed that since they had powerful motors (low Qes) and low moving mass (Mms), this was demanded for horn all design, but they didn't look at the rest of the sound system, which either used impedance matching amps or ones with up to 20 ohms of output impedance, either of which dramatically increases Qes, Qts.
GM
Well, I have to admit it's been a while since I listened to the D5nf Gold with the PB9 passive, but, since I had a customer who wanted to hear them, there was nothing to do but set them up. We actually did our listening session ***-backwards as we began with the D5e Type II, which I admit is not a fair thing to do to a customer, but guess what, the D5nf/PB9 more than held it's own. What an awesome speaker this is. I cannot find any fault. It is clean and smooth, very well balanced top to bottom, with a strong visceral impact on the bottom end. Voices are as natural as can be.
So what do you get for around four times the money? Hairs standing up on the back of your neck and that Oh My God!! factor, but, and this is an important but, D5nf/PB9 is a speaker that I could easily live with and not feel in the least deprived.
Well, o.k., maybe a little.
An externally hosted image should be here but it was not working when we last tested it.
So what do you get for around four times the money? Hairs standing up on the back of your neck and that Oh My God!! factor, but, and this is an important but, D5nf/PB9 is a speaker that I could easily live with and not feel in the least deprived.
Well, o.k., maybe a little.
Below is a link to a blast from the past -- a complete loudspeaker system from Exact that is currently being auctioned online in Japan. You can see what a big difference there is between Exact and Feastrex with this loudspeaker. I don't have anything against the acoustic lens (I liked the way they worked with Exact and did not feel that they detracted in any way) but I don't feel any need for such a thing with Feastrex. The EL Control and dual voice coils represent an effort to get additional extension and tighter voice coil control at both ends of the frequency range, and it definitely has some good things to recommend it. But it also has its downside -- while not as bad as a multiple driver system with a passive crossover, the reintroduction of passive electronic components in the EL control has, to a lesser degree, some of the same negative effects. If I had this system, I would be using the EL control for some music, and bypassing it for other music. (There is a bypass switch setting.) The voice coil also has a strip of iron foil in it that is supposed to pull the voice coil back into the center, neutral position of the VC gap. All good and well, but having a bifilar voice coil and an additional strip of iron there all means that the VC gap needs to be that much larger, and it also means that square wire cannot be used. So there is a downside there too. Nevertheless, it is a wonderful sounding system.
http://www.diyaudio.com/forums/showthread.php?postid=1536157#post1536157
-- Chris
http://www.diyaudio.com/forums/showthread.php?postid=1536157#post1536157
-- Chris
Once again I have to admit I'm no speaker cab designer, but there is just something that seems so right using the D5nf with that passive. It would seem to almost be a perfect way to use the driver as you get the benefit of the extra help with the same paper cone with the passive, and no possible port noise or other loading probs, more $$ but very nice... Dave
Well, from both a technical POV and my own 'adventures' in PR vent loading experiments as well as numerous other folk's experiences voiced on various PR threads, the consensus typically was that while there is the benefit of no port noise and the ability to easily tune to alignments that would otherwise require TL size vents, a PR's much higher group delay (what many folks claim is why vented sounds so 'bad') due to its 5th order (4th for vented) deep notch ~an octave below tuning relegates it tunings to well below our acute hearing BW for high SQ playback, so typically < 18 - 24 Hz depending on the person and the driver being loaded.
Considering the relatively high Fs of all the Feastrex drivers, this begs the questions of what is its tuning frequency and is there any 'sub' chamber, i.e. double bass reflex (DBR) that it tunes instead to isolate the driver from it somewhat? If so, what type internal vent coupling is used?
GM
Considering the relatively high Fs of all the Feastrex drivers, this begs the questions of what is its tuning frequency and is there any 'sub' chamber, i.e. double bass reflex (DBR) that it tunes instead to isolate the driver from it somewhat? If so, what type internal vent coupling is used?
GM
Feastie Boys World Tour
First stop, Singapore, en route to India. The D9e-III bronze frame drivers (literally, handled ONLY with gloves on!) were placed in boxes originally built for the Coral Beta 8. Probably the boxes are too small, but in a pinch you use what you have on hand, right? Alson enjoyed was the NF5ex in a 30-liter enclosure originaly built for the D5nf. This is also probably a bit smaller than ideal but I imagine it was a lot of fun listening to both. Hopefully BTW will give us some impressions later . . .
-- Chris
First stop, Singapore, en route to India. The D9e-III bronze frame drivers (literally, handled ONLY with gloves on!) were placed in boxes originally built for the Coral Beta 8. Probably the boxes are too small, but in a pinch you use what you have on hand, right? Alson enjoyed was the NF5ex in a 30-liter enclosure originaly built for the D5nf. This is also probably a bit smaller than ideal but I imagine it was a lot of fun listening to both. Hopefully BTW will give us some impressions later . . .
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
-- Chris
cdwitmer said:
Hi Chris,
Thanks for helping me post the pictures ... we had a long day and I'm not good at linking pictures..
Just a short report...
Mr Teramoto was on a very hectic schedule.. as he need to catch his plane to India later in the evening. So I managed to slot in a time period of 5 hrs. What a wonderful 5 hrs it was..
.. DDriveman , another Feastrex user and my good audiobuddy was there ... when Mr Teramoto started taking out the Feastrex drivers one by one.First up was the D9eIII... What a beautiful drivers it was..I straight away told Mr Teramoto that pictures cannot do justice to the drivers.. If you look at the first picture you can see the reflection of my ceiling partitions reflecting off the back driver. Mr Teramoto only uses gloves to handle this drivers..
My D9e spks box is still at the carpenter's work shop so I had to make do with a old trusty Coral Beta 8 box.. luckly the D9e fits will into the box. IMO this box is a bit on the small side.. Feasterx's orginal box will be a better match..
Sonically, this D9e III driver is a sonic jaw dropper.. It simply brings you so much closer to the recording and performance that when you switch to another different speakers.. suddenly you will notice information loss, or in other words it make other speakers sound broken..
We tried the Sheffield Drums... very very impressive in terms of scale , speed, details and ability to start and stop.. The D9s do have very good bass.. We played some Chinese Singers like Tsai Ching... and although these are normal recordings .. The singers just simply sound like they are standing in front singing just for you.. For me what I found most stunning was music although presented with such clarity, inner detail... was also presented in the most natural and life like manner... In other words, you will soon forget to evaluate the audio aspect of the speakers.. and instead you will relax , enjoy, appreciate, be startled by details you never head before.. Singers, performers.. just simply sound like they are performing just for you.
DDriveman and myself both have the D9e I and I told Mr Teramoto darn... we have been "posioned" by the D9e III and now need to figure out how to own a pair...
.... The D9e III is such a magnificent driver.Mr Teramoto also had the D5e II, unfortunately I didn't have a suitable cabinet, so we decided to try the D5nfEx instead... The D5nfEX obviously does not move as much air as the D9eIII so soundstage was smaller ... No it didn't have the ultimate resolution and make you forget you are listening to the spks like the D9e III but it have the Field coil clarity, speed, resolution.. All of us agreed that the D5nfEX is definitely a class above the standard D5nf.
The D5nfEX is a great introduction to the Field Coils type sound, IMO beats all other non Field coild drivers hands down.
rjbond3rd said:
Hi,
The drawings/plans for that box can be downloaded from the Coral EastMarine website.. It has 4 ports, with 2 different port lengths, so probably not so easy to figure out the tuning frequency. I built this box according to the plans when I first got my Coral Beta 8. It's a nice box but it don't think it's tuned very low.
Samuel Jayaraj said:
NO! ABSOLUTELY NOT!
You will need to go to Tamil Nadu . . .
They are in Tamil Nadu right now, and I am pretty sure Tamil Nadu is to be their permanent home.
AND they will no doubt be in some very wonderful enclosures, that are able to do justice to them.
I'm assuming that eventually opportunities will become available to hear these drivers in Tamil Nadu (and possibly elsewhere), as their new owner plans to do business with Feastrex drivers in India.
Just be forewarned -- they are SERIOUSLY addictive. Seriously.
I gave that same warning to "BTW" in Singapore, and I meant it as a joke, but he wrote back to me after hearing them, and I quote verbatim, "I know you were kidding when you asked me not to let Mr Teramoto demo the speakers . . . But in actual fact you were spot-on . . . these drivers are spell-binding. Such clarity and details with naturalness that every other speaker pales in comparison." A few people who went to hear the speakers believing that they were going just to satisfy their curiosity and they would never actually buy those speakers for themselves ended up buying the speakers, in spite of the extremely high price. So . . . hang on to your wallet very tightly! Or seriously consider not even listening to them in the first place . . .
-- Chris
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