Something stirs in the Undergrowth

[Dave the bass]

....as an aside, full marks for over the top.

Totally agree, one of Robert Calvert's finest moments with the Sonic Assassins.

[IslandPink]

(a) I'm quite familiar with what's in the system, both this and the Vox Olympian
(b) The thing that gets me is how he made the bass/mid horn and integration work so well - Nick is correct here in my meaning. Everyone talks about the great tone and the vocals being superb. This thing is pretty aggressively folded and uses a bigger more heavy-duty driver than any I've been trying to coax sound out of in my horn. Also the path length difference from the lower horn to the bi-radial horn is 2 wavelengths at 500Hz, so it's not anywhere near physically time-aligned. I still don't understand how he got everything to work so well - also he has no back-volume on the Vitavox 15" - amazing ....

The Basso bass does seem to be a bit smaller than the more expensive Elysium so maybe it's based on more conventional sub design, though I'm sure with LV it won't be a badged version of anything else.

[chris661]

Sounds like you know more than the website lets on. What's in the midbass horn? If you can provide a rough sketch that'd be great.

A 15" with a light cone can make it up to 2kHz smoothly (see Beyma 15P80Nd), so crossing at 400Hz seems entirely reasonable, even for a driver that large. Not saying they can all do it, but with the right one, it seems easily possible. Using the phase plug would help to extend the upper bandwidth, too.

The path difference between midbass and midrange is a conundrum. The rest of it does appear time-aligned, though.
Perhaps asymmetrical crossover slopes make up the phase difference - from the 36dB/oct slope on the subwoofer, it's clear they're not afraid to use them when needed.

Chris

[IslandPink]

There are a few reviews and interviews around with more info and some other historical LV stuff.
The internals of the folded Vox Olympian horn are based on the Air Partner & Tone Scout which are based on the Vitavox Oracle and Thunderbolt designs :
http://website.lineone.net/~empson/feat ... tavox.html
It’s not so much of a question that a good 15” driver can work up to 500Hz or even 1kHz as a direct radiator – agreed - it’s the low level tonal aspect on a horn that has bothered me. Because of the very high efficiency on a horn like this , these drivers are barely moving, so they are ‘down in the mush’ of the mechanical hysteresis effects of the spider and surround. I found out of the three drivers I used, only the one with the lowest Rms ( ~ 0.5 ) and very light cone , the FE208Ez, was giving me what I wanted at normal HiFi listening levels.
There’s something odd about the expansion of the Vox folded horn that’s bothering me. It’s descibed as a compound exponential, and the cross sections from the construction …
http://www.infoaudio.pl/artykul/295,liv ... -show-2015
( See pic of four lower horn cabinets, near the end of this page )
…seem to show a very slow expansion at the start, near the driver – possibly below 50Hz effective. I’m wondering if this has something to do with the ability to get the driver loaded properly over the 70-500Hz range without using a back-chamber.

1.The rest of it does appear time-aligned, though.
2. Perhaps asymmetrical crossover slopes make up the phase difference - from the 36dB/oct slope on the subwoofer, it's clear they're not afraid to use them when needed.

1. Yes
2. No don't think so - this is about 1.4m difference btw ! if like the Air Partner then it will be aligned normally at 500Hz accepting the two-wavelength path difference. You can then expect ripples in the response above and below as the paths fail to match. The Air Partner I believe uses either a 1st or 2nd-order HP on the bi-radial horn, and a 2nd-order LP on the folded horn which will be more like a 1st-order when you consider the driver's rising response from 300Hz to 1.5kHz.
Bear in mind a speaker like the Tannoy Westminster has about 3 wavelengths mismatch at 300Hz between the front and rear output of the 15" !

[IslandPink]

Ok on the modified Faital driver, I did two more shorter cuts in the cone and glued back together with PVA. I also made an adaptor ring to help mount the thing onto the Perspex OB. So now I have it playing and also with the Yuichi horn brought in.
Here's a pic from the front with flash :

The second set of cuts actually helped the sound a little, but I still think it went a bit far on the first set - I compromised the integrity of the cone and perhaps lost a bit of the upper mids to a breakup. So I'm missing a bit of tone in the upper mids and some dynamics esp on pianos.
Anyway it still sounds close to excellent when combined with the Yuichi - just playing some of the usual suspects at the moment. The Faital reaches down towards 100Hz so it shouldn't be too difficult to bring in some bass.
I am using the amp crossover with 3dB down at 700Hz , plus a 0.6mH choke on the driver to roll off a bit more steeply above 1500Hz. Female vocals sound clean and non-aggressive with this.

I have ordered another 8FE200 driver though. Once I get it I will first check the relative efficiency of the two drivers to see if I lost something with the mods. Then I will do some mk.2 mods which at the moment I reckon will only involve painting on some diagonal stripes from 50% to 100% of the cone radius in about 6 or 8 places.

[IslandPink]

Got the new 8FE200 yesterday. Will do some tests over the weekend when I get back from a business trip.

I think my plan will be to test the Mk.2 treatment on one of the Fostex FE103e drivers in my MLTL's , first .
In the meantime check the difference in sound/output from the unmodded vs. modded 8" drivers.

[Daniel Quinn]

Perhaps doping the driver as was . may have been better , than cutting it and doping it in 4 strategic places ?

[IslandPink]

No the analysis showed where things were happening and I had a specific aim to work only on the 2.5-5kHz region. That certainly succeeded but it looks like I went a bit far and weakened the cone - you live and learn. I'm reluctant to do a more generally & heavy doping of the cone as per the Doc Mods because I don't want to reduce the sensitivity of the unit or alter it's lower midrange behaviour ( which is excellent ) .

[Daniel Quinn]

fair enough .

[cressy]

I think the faital range is pretty good over the entire range, abit of a sleeper.
Dont really see them mentioned much anywhere. As good as the usual suspects

[IslandPink]

Yes I've been looking through their small lower-power drivers and there are some ones that are very smooth in the mids and with low mechanical damping, like the 3FE22 , the 4FE32 and the 5FE120. Some of the line-array builders on DIY Audio are on to them. Prices are very low ( £17 to £ 22 ! ) .

Meanwhile I did some extra mods on one of the FE103e drivers in the little towers, to test the idea of just using paint stripes to break up some HF peaks on the outer cone.
See below. After about an hour of listening today using various tracks from Don Juan's Reckless Daughter, going back & forth ( with stereo summed to mono ) I can say there is a small but useful effect. The one with the extra diagonal stripes ( of acrylic paint ) is about the same efficiency but smoother in the upper mids, ie. female vocals and overtones. There is a slight loss of sparkle at the top end on guitars and cymbals so for a FR application it's swings vs. roundabouts, but for a midrange-only driver application I think this could work enough - so can be trialled on the second 8FE200. May need 2 or 3 applications on the bigger driver.

[IslandPink]

Last week, tested the Faital drivers ( stock and modified ) and got very minor differences on the FR plots ( 2D FFT from white noise ) that basically failed to show up the fairly significant audible differences.
Likewise same result on the FE103e drivers - one with Enabl alone, one with Enabl + diagonal stripes.

Anyway since Owston, fired up for more hands-on work.
Took the second ( un-modified ) 8FE200 and dug out the Microscale gloss coat that Bud recommended as the first stage of the Enabl. did a 30% dilution and painted this over the cone and dustcap. This initial coat as I remember from the Fe103e took away some of the papery overtones and smoothed out the treble a little bit, so hopefully will have some effect on the Faitals. In the process I noted that the dustcap was pretty lively and harsh when brushed. This is good, because one of the key things I have planned it to create a second phaseplug ( 'project teardrop') as used on the horn throat, to place in front of the Faital dustcap. I am encouraged to think the masking & 'blending' of the output from the dustcap by the phase-plug will do something quite useful.

[IslandPink]

OK here is 'Project Teardrop' mounted up and in place in front of the stock Faital 8FE200 driver on the OB. Playing as of yesterday 10.30pm with the Yuichi and the amp crossovers. It sounds bloody nice to be honest, think we have the makings of a great midrange driver here. I will still do a bit of cone treatment with paint plus a little bit of the bison glue in the trough between dustcap and cone ( to be tested on the 'slashed' driver first ) . This driver is still running-in, I am noticing more tone and low-level detail coming through in the last hour. The music just expands into the room.

(OK, let's not talk about the quality of the plywood)

[Ali Tait]

Looks like you nicked off the front of a Studebaker.

[Daniel Quinn]

You appear to have put a model aircraft propeller in front of your driver and this is giving you more tone and low level detail .