Something stirs in the Undergrowth

Dedicated to those large boxes at one end of the room
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IslandPink
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#1111

Post by IslandPink »

Good effort, Chris. Post up a picture if you like . I must get up to Blackburn(?) some time . I assume from your comments you're getting really nice bass tone from that unit as well as power ?

Thanks Lynn, another valuable posting.
I will try to check out a good TQWT though, as James felt the recent designs were, if anything, a touch more natural and uncoloured than a TL , if at the expense of a little bit of extension. So, I'll ask Scott if he can put me in contact with anyone who has a decent-sized TQWT project, eg. 8" driver.Of course the T-lines in the Ariel are rather more sophisticated than other TL's.
I will know a bit better over the weekend whether the sealed-box solution has 'legs' for the project. The 8PE21 has better tone than the Fane, in isolation.
I will also add, to both Chris and Lynn, than the problems in matching any cone driver in any configuration to something like ( even ) a 288H with a Le Cleac'h horn are very much non-trivial . The performance of the Vifas in the Mk. 6 Ariels I built , in that midrange area, is not a match . The level of speed and tonal clarity needs to exceptional . The only things I've heard so far that were definitely in with a chance are James's AER's in the perspex open baffle, and 8PE21's and FE167E ( from a few years ago ) played without any mounting or enclosure .

Ps. this guy's site is superb :
http://www.troelsgravesen.dk/Diy_Loudsp ... ojects.htm
Check out this page on female vocal reproduction for instance :
http://www.troelsgravesen.dk/vocals.htm
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chris661
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#1112

Post by chris661 »

Was waiting on figuring how to get photos out of my phone, and into my laptop.
Bluetooth wasn't for working, then it occurred to my that I can just put the memory card in...

Anyway, yes. Tone's very good. It'll do all the texture of a double bass, with all the dynamics you can ask for. Wonderful combination, puts my old sub into a bad light to be honest.
I haven't heard anything quite like it. The low-distortion motor system seems to make this something special.

It looks like you missed it Mark - I'm studying at the University of Sheffield.
If you're passing by on your way to/from Owston, feel free to drop in for a demo.

Anyway, here's a photo. Sorry about the picture quality - phone camera's not fantastic, and then had to compress a lot to get down to allowable file size.

Chris
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BudP
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#1113

Post by BudP »

This started to confuse me, so then I went upstairs for a bath, to relax.
Then the voices started again, in a different way. They started to say "transmission-line bass ... transmission-line bass" .

So this adds another potentially useful permutation to the matrix : transmission-line ( vertical tower - good ) to 2-300Hz , then OB with wide-ranger 8" from there to 700-800Hz, then ... you know the rest .
yes yes yes! You might investigate the slant line TL that Dave Dlugos has been working with. Easily able to keep up with the Lowthers, or much smaller Fostex and Mark Audio drivers in Fonken cabinets. Also allows the use of two smaller long throw woofers. The schema for the ones I have is below, but you want to converse with Dave about where he has gone from here. The audible quality of the bass is superior in texture support to any other bass driver/box combo I have come across. Not equal to Gary Pimms cardioid open baffle for impact, but if you aren't into equaling outside thunder storms with inside ones, that would be a moot point. I have yet to hear Gary Dahl's solution, but I suspect it is in the same category, a tympani master is not going to have a lethargic bass system.
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Lynn Olson
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#1114

Post by Lynn Olson »

IslandPink wrote: I will know a bit better over the weekend whether the sealed-box solution has 'legs' for the project. The 8PE21 has better tone than the Fane, in isolation.

I will also add, to both Chris and Lynn, than the problems in matching any cone driver in any configuration to something like (even) a 288H with a Le Cleac'h horn are very much non-trivial. The performance of the Vifas in the Mk. 6 Ariels I built, in that midrange area, is not a match. The level of speed and tonal clarity needs to exceptional. The only things I've heard so far that were definitely in with a chance are James's AER's in the perspex open baffle, and 8PE21's and FE167E ( from a few years ago ) played without any mounting or enclosure.

P.S. this guy's site is superb:
http://www.troelsgravesen.dk/Diy_Loudsp ... ojects.htm
Check out this page on female vocal reproduction for instance :
http://www.troelsgravesen.dk/vocals.htm
Well, Gary Dahl's success with the GPA 416 Alnico's in compact closed boxes ... with the AH425 and the Radian 745NeoBe ... is a useful data point. Gary's very pleased with the match between HF and LF sections, and he's a picky listener.

My simple-minded take on the larger question is what you really hear, regardless of the enclosure (which is really just a sound modifier when you come down to it), is the sound of the driver itself. Enclosures extend bass (mightily in the case of a TL), or magnify dynamics in the case of horns, but you're always left with the sound of the driver itself. There's no way around it, and I suspect that all drivers have a characteristic "sound" thanks to all the complex properties of the magnetic system, the cone, and the spider and surround.

That said, I'm speaking of the sound of the driver on a very large baffle, more than a meter across, an approximation of the infinite-baffle condition. Low Qts drivers will sound thin, so that has to be ignored in favor of overall tonality.

The little Vifas sounded pretty much the same on the baffle as they did in the finished speaker ... they just had more dynamics, much better bass, the usual things. But the tone character remained the same. Similarly, the GPA Alnico drivers have the hallmark Altec sound ... sparkly mids, vivid tonality, and really good piano tone. That seems to be there regardless of enclosure. When my friend Thom Mackris was experimenting with a small-format Lowther in a simple box versus a custom-made 1-meter LeCleac'h horn, it sounded the same tonally ... just much bigger in the horn. It still sounded like a Lowther either way.

So ... entirely aside from OB, closed-box, TL, horns, what have you, the sound of the driver will be there. OB will ask much of excursion, TL will take maximum advantage of what the driver can give, and closed-box is in a middle ground. Horns magnify dynamics in a very useful way, but driver colourations are magnified as well, and there are potential time-domain issues with horn colourations.

As for me, I'm considering dual 416's in WWT, side-by-side, or WTW configurations. A WTW layout would be ugly and truly massive in scale, and the hassles with the MTM in the Ariel were a lot of trouble to resolve. WWT has subtle time-alignment issues due to the floor reflection enhancing the lower driver but not helping the upper driver much (this problem is much worse in WTW layouts that are large). I may settle for side-by-side and angling the front panel into two sections.

By the way, many thanks for the pointers to the Fane 15BX and 18BX drivers. These look really interesting, with dual spiders, which are a rather uncommon feature. The dual spiders not only prevent unwanted rocking motions, but if one spider is reversed, a lot of transient spider nonlinearity is cancelled out. Very slick feature.
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g3dahl
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#1115

Post by g3dahl »

So ... entirely aside from OB, closed-box, TL, horns, what have you, the sound of the driver will be there.
I agree completely. The mid-bass/lower midrange success in my system isn't so much due to the closed box as it is to the sound of the 416, which (surprisingly) happens to work beautifully in a sealed enclosure.

Gary Dahl
So many tubes, so little time...
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IslandPink
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#1116

Post by IslandPink »

I agree entirely - driver choice is crucial . I just have some practical difficulty that I haven't explained , with a 16" mid-solution . I just don't think I have the space for a 70L box and a decent-sized bass solution underneath ; or if I have the space , then I get too much light blocked at eye-level ( the whole speaker system is fitting in the bay window area at the front of the room which is already North-facing ) .
Then the connundrum becomes : smaller mid-driver ( & enclosure ) , less efficiency ( eg. 93dB ) unless I lower Qts .... then low-end rolloff of this unit is 150 or 200Hz instead of 100Hz ; tapped horn can't reach that far ; have to design another sort of bass solution that goes to 200-250Hz .
So, that's where I find myself currently .
With some clever packaging it might be possible to get a TL or TQWT bass solution down mostly below window-level ; providing a platform for a smaller mid-enclosure or a perspex OB ( transparent ) .
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chris661
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#1117

Post by chris661 »

If it were mine, I'd work on a bass solution that'll go up to the compression driver.
40Hz-1kHz (or so) isn't impossible, but would require some thought and careful planning.

My argument for that would be the simplicity: if one driver can cover that range properly, there's no need to split the range in two and try to integrate two different drivers.


Alternatively,

If the TH would be placed elsewhere in the room, an 80-1kHz solution would be do-able. A nice 12" PA midbass would fit the bill perfectly.

I'm not talking about guitar speakers. They're designed to introduce their own sound - look at the 3kHz peaking of most guitar speakers!!

Something like this:
http://www.usspeaker.com/beyma%2012p80Fe-1.htm

Note the flat response through the region you'll be crossing over.
A quick Hornresp simulation looks pretty good: in 22L (including port volume), you can get almost ruler-flat from 80-800Hz, at which point port resonances start kicking in (shouldn't be a problem if the cabinet is lined). So yes, 97dB@1w from 80Hz to as high as the response charts say you can go.

I see no reason to use anything more complicated.

Chris
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slowmotion
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#1118

Post by slowmotion »

And, depending on what you like, a large low Q driver on an open baffle go together well with midrange and tweeter horns.

In my very humble opinion ( :D ) what you like is the most important here.
- Jan -
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IslandPink
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#1119

Post by IslandPink »

Very true, Jan, thanks for your support ! :D
The paradox here is that one of my reference points for midrange tone was a speaker Chris brought to Owston a few years ago : small boxes ( not sure what type ) with Enabl'd FE126e units, driven by a low-power 6EM7 amp. That had some of the best female vocal rendition I've ever heard.
Integration of the bass to midrange shouldn't be too difficult as the mid-unit either way will have low phase change and a natural roll-off at the lower-end. Might have to control excursion with a high-pass somewhere below effective crossover, for the OB option . The bass option ( driven from an SS amp ) can probably be 1-st order low-pass with some impedance correction at the speaker.
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#1120

Post by chris661 »

Hi Mark,

The cabinets were folded Voigt pipes by Planet10.
They go to 100Hz, just. The drivers themselves had phase plugs, and a notch filter centred around 7kHz, attenuating around 3dB.

They did sound good, though. Just not fantastic at rock music, hence my moving on to larger multi-way systems.

I might revisit those Fostex drivers some time, maybe make some dinky desktop speakers with them.

Chris
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IslandPink
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#1121

Post by IslandPink »

Interesting - thanks Chris ...and, I do remember you're at Sheffield, it was just my brain on a Thursday evening which had run out of 'swap space' after the working week .

I still cannot ignore OB for the bass, still - after more reading of Troelsgraven's site, given the huge number of interesting speakers he's made , I come across comments like :
" If I had another and larger living room, the OBL-11s could be my one-and-only speakers as they can do things none of the other speakers including Jenzen D and ATS can do. They're easy to drive, they have the low-end dynamic only a 15" on an open baffle can manage - and they can play vocals louder than any other speaker I've ever made. "

It appears he is very happy with the Eminence Deltalight 2515, with some passive EQ . James has also threatened to post an updated list of 'interesting OB bass drivers' soon.
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#1122

Post by Ali Tait »

Hope he does, I'd be interested in something better for my OB's. Still, might try what I've already got in acrylic baffles instead of the birch ply I have at the moment.
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#1123

Post by Lynn Olson »

Thanks for the info on upper size limits, Mark. That and the subjective goals pretty much define what's possible with any technology.

My experience with the Fostex drivers is they sound more open and crisp, but not quite as dynamic as an Ariel, much less an Altec 416 or large-format compression driver. I think of it in terms of max headroom for a given driver: would it work in a 500-seat theatre, for example? Or a large listening room?

A single 5.5" Vifa is a minimonitor driver, suitable for nearfield use, and not enough for the living rooms I've had over the last twenty years. A pair of them raises the headroom by 6 dB (3 dB efficiency gain combined with doubled power input), and runs out of steam around 100 dB at a 3.5 meter listening distance. A single Fostex widerange driver has roughly the same headroom, based on considerations of cone area, paper-cone breakup levels, and linear excursion.

A large-format compression driver, combined with an adequately large horn, is good for an astounding 20 to 25 dB more headroom at the same listening distance. That's why large-format compression drivers and horns have been the MF/HF device of choice for movie theaters for the last seventy years. Small-format moves the required crossover up an octave (or more), extends the HF limit by a half-octave or more, and gives up 6 dB (or more) of headroom (based on considerations of diaphragm area). This is why small-format is rarely used in movie-theatre applications.

Based on the early prototypes I heard in Dallas, the Altec/GPA 416 Alnico has less headroom than the AH425/Radian 745NeoAl. At a guess, about 5 to 10 dB less. It has a native efficiency of 97.5 dB/metre, and is linear up to 50 watts or so. It's not a modern PA/theatre driver, unlike the JBL 2226, but does really well at 1-watt input levels, where the JBL sounded didn't sound good at all.

This is why I'm considering a pair of 416's; it won't quite get to large-format headroom levels, but an improvement in headroom of 6 dB is very noticeable, even at 1-watt listening levels. My only guess this has something to do with a VC that doesn't get hot and changing parameters, and low IM distortion.

An OB has good headroom around the octave of baffle peak, but that drops off in the bass at a rate of 6 dB/octave. In effect, the diaphragm shrinks. Equalization actually makes the headroom problem worse, not better, since power in being pushed into the low-efficiency self-cancellation region.

I'm pretty sure a widerange Fostex (or Lowther) combined with the AH425/288 will sound just fine at low levels (after equalization), but will fall apart pretty badly once 90 dB is passed. The Fostex paper-cone drivers, like Lowthers, have an abrupt-onset breakup region. Things are clean until they aren't. Fostex, Lowther, AER, and Feastrex sound pretty grim once you hit the the acceleration limits of the cone. Horn loading helps, but once the whizzer starts breaking up, it's all over.

If you want to come close (within 10 dB) to matching the headroom of the AH425/288, there isn't much choice. Multiple 15" drivers, or single drivers that are horn-loaded. OB with large-format drivers will headroom-match at crossover, but not a decade lower, where they will sound more like 8" drivers ... but this is where a subwoofer can come in, easing the load of the OB array.
Last edited by Lynn Olson on Sun Apr 20, 2014 8:03 pm, edited 1 time in total.
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#1124

Post by Lynn Olson »

Check out the 90~700 Hz bass horn over at:
http://www.diyaudio.com/forums/multi-wa ... -horn.html

Based on the simulation, it looks it would work with the AH425/288 just fine, and is optimized for the superb Altec/GPA 515 Alnico driver. Here's a thought: what about making the bass horn out of perspex?

Unlike a TL, it won't need internal damping, so it could be clear all the way through.
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IslandPink
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#1125

Post by IslandPink »

Thanks for the link . It does look like a less sophisticated version of Martin's horn though - not entirely convinced how it will sound ; although the construction method is useful for ref. It's basically conical or even parabolic in expansion for the first part, and this shows in the simulation (ripple ) . Good point on perspex - I have thought that a sealed box speaker could be made from perspex too, but the surfaces would have to be 'frosted' or painted to conceal the stuffing !

Meanwhile, a bit of preliminary data from some tests this evening .
I must admit I'm not clear on the basic protocol of the test here - for instance time of sample that's sufficient, settings for FFT on Audacity, so it's very tentative .
Pics below show example 1 test of Fane 8M on 30L box , distance about 1.85m ( it's all about wire length - speaker situated in typical location , microphone as close as I can get with computer in normal location ! ) . Anyway, 20 sec of white noise from CD player ; transformed by 'Audacity' into FR plot. FFT performed using 2048 ...something ... ?
Perhaps Nick can comment ?

The unit has a zobel filter at the terminals, and a 720Hz low-pass in the supplying amp .

The next plot shows the horn with the same amp supply and zobel; but this time measured from 1.5m .

Neither of them look all that impressive, and the bass rolls off earlier than I expected from the sims ; however the number of data values below 250Hz is pretty sparse in both data sets, for some reason .
I will send the data from these and more ( repeat ) sets to work and tidy-up in Excel tomorrow .
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