909-8A: 400Hz tractrix horn?

[adam_ecofan]

hi all,

my first post here, theophile suggested i move my
thread from lansing heritage to the altec board.

planning to use the drivers from a pair of 90's altec
A700's in a new project. hoping to draw on the
experience here to help guide the process.

have access to cnc routers and anechoic testing and
will be able to compare a series of horn flares.

i have a design/liberal arts background and can
understand the general principals but am limited in
my ability to penetrate the technical aspects of horn
building

however i have some very clever people to help
out at this end - so with your assistance i'm sure
an interesting speaker will result

cheers,

adam

[Alien_Shore]

Welcome to AUB, Adam.
Can you tell us a little more about what you're hoping to do? Is this for Hi-Fi? Are you just experimenting? What kind of cabinets, crossovers, etc.?

[adam_ecofan]

hi all,

for hifi; picked up a pair of A700's with matching
crossover and mosfet amps - have a thing for
triode amps so i thought it would be neat to use
the 515 and 909 in a 2 way for home listening.

have been reading around horns since i came
across 'gizmo' rosenberg in the nineties.

about time i got the dust flying and built a
speaker myself... can even make comparison
and measurements of different flares (should
be able to arrange both free air and anechoic
tests)

earl k at audio heritage has posted me a couple
of links to follow up - can't post a link directly yet
as i only signed on to the altec board yesterday.
he's recommending a radial horn - something that
the 'pi' speakers chap makes a good case for.

also, friend who's been in the speaker biz here
since the 70's has a good fat file of altec info -
box plans and such, will see what else is in there
and could scan any material of interest to the group.

kind regards,

adam

[bowtie427ss]

Temper your expectations with the number of systems that Altec used a tangerine equipped small format driver in crossed that low.

IMO&E, those drivers are best suited to XO points 1.2khz and above, YMMV.

[Altec Best]

Welcome to the Board Adam !

[adam_ecofan]

hi all,

thanks bowtie - i was wondering if a one inch throat could
really meet the woofer somewhere below 1k.

but how high can the 515 be crossed over and still sound ok?

not aiming for true fullrange - just whatever can be sensibly
achieved with the drivers to hand - best use rather than
ultimate system.

also, is there a plain english explanation for the operation
of phase plugs - jbl radial, altec tangerine, tannoy pepperpot?

same job - different geometry - how does it work?

warm regards,

adam

btw - had my ear up to a tannoy 15" in a canterbury enclosure
very smooth tweeter - even from an inch or two away...

[adam_ecofan]

hi all,

here is the link to the thread i started at audio heritage
on the same subject (before theophile recommended i
visit with the AUG); will keep both threads open with
info and pics - some pics already up at AH.

909-8A & 515-G - suggestions for horn and bass alignment please

warm regards,

adam

[Geekstar]

The simple and not-particularly-useful answer is to cut the 1" off as high as possible and the 515 as low as possible. I'll bet you already knew that!

I think you can "get away with" 800hz XO, especially on a 400hz horn, but Bowtie is right that your 1" drivers sound better 1200 up.

If you are going to go so far as to make horns, why not switch to a 288? Make the horn 1.4" capable with an adapter to 1" for now. A 288 on a 400hz horn will play down to 500 nicely.

The other thing I will say is that most round tractrix horns are like laser beams. Verrrry narrow. Yes, they image like crazy but the sweet spot is so narrow you can hardly fit two ears into it (only half joking).

If you want a tractrix, look to the Klangfilm/Siemens square tractrix for the Eurodyn as inspiration. It is a 2" horn, good to 600. One of the best small horns I have heard. It was nearly ruler flat 600-9k with a WE 594A when I measured it.

Here's a pic of the later plastic version. The older metal one is better.

Eurodyn Thomas Schick

see also ?????????????????ȡ??????ǥ????Ȳ???

You can see Eurodyn vids on you tube where a louvered diffuser is installed in front of the speaker to improve dispersion characteristics for theater use, but it is not too bad...subjectively no more directional than most exponentials.

The EH500 mentioned by Earl K in that Lansing thread is also a killer horn.

I don't know how many samples of either can be found in Kiwi Land, but these are the two small horns I would pick for models if I were looking to mill something out. These geometries work and if you could make either out of hardwood, that might get you to the top of the food chain in a hurry.

Here's a sweep of the Eurodyn horn with a WE594A (red trace). Man, that combo sounded great!

[adam_ecofan]

hi all,

here are a couple of altec pictures.

first is a two way hiding under the
stairs at the university acoustics
dept - hope to rescue it sometime.

the second is my friend matt at
clarry the valve tech's place.
mono stack with altec 605, vitavox
mids and a goodmans trebax for the
tops. leak monoblock for power - for
playing blues cuts etc.

clarry also has model 19's in his
front room now...

cheers,

adam

ps - is it better to link to photo
site than add images to post?

[adam_ecofan]

hi geekstar,

thanks for your input - will digest
and post again.

have the A700's to work with so
whatever solution will give best
results (am ok with compromise)

radial horns seem the easiest to
work with - turning a 3ft horn flare
looks like a 'major'. less material
and dispersion/reflection control too.

my friend who can negotiate
hornresp and leap quite keen to
make a series of flares and make
objective/subjective comparisons
- don't have to get it right first time...

nz has some great native timbers
if we go with that instead of ply. is
density the key? eg high pressure
laminate 1450kg/m3, keruing ply
about 800kg/m3 and aussie hoop pine
comes in at 600kg/m3.

anyhow,

cheers,

adam