need help with altec 515 (mid)basshorn....

chaos

Member
2006-09-11 11:04 am
hi everybody, maybe somebody is willing to help me!
right now i listen to a scaled down version of the living voice air partner.
(if somebody is interrested in the dimensions, sorry, i promised to the guy who helped me years ago not to publish it. please dont even ask)
bassdriver vitavox mm300, 12".
midrange vitavox s2 with rh330.
treble jbl 2405.
500hz, 10khz

source:buff III, s&b tx103 transformer, choke loaded 5842, diyhihisupply 300b, lady day(310-300b)
no phono at the moment, working on the dac and needed the stepup.

room is small, 3,5m x 5m x 2,5m.
ft:10 x 16,5 x 6,5.

one thing:never trust somebody who says you cant listen to a horn like this nearfield, its sounds wonderfull!(3m, 10´away).
i´m quite shure it would sound better in a larger room, but even in my listenining room it is fantastic!

you may wonder why i would change the bass horn:

got 2 gpa 8hp woofers for a very good price and searched the web and of course this forum.
515 midrange should be very good.
my horn is folded, a straight one like the exemplar horn could be better at higher frequency?
listening mainly to acoustic blues and jazz, sometimes 70s rock.

something like the exemplar would bring the rh330 down 6-7", would be good i think because i am listening that close. the rh330 would be on ear-height and this sounds definitly better in my room.
the horn should go down to around 40-50hz, low enough in my room. i have 2 m&k 5000 subs, but they are not connected, dont integrate well.
tried the subs with active xover and software, did not like it.
(btw, i dont like to touch the data anywhere, convert pcm to dsd or something like this.... for me it sounds best as it is, playing pcm as pcm and dsd as dsd)

i´ve build the "air partners" but i had a plan.
just downloaded hornresponse, but i have no plan:eek:

IS IT WORTH EVEN TO THINK ABOUT A CHANGE?



thx, klaus
 

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you may wonder why i would change the bass horn:

got 2 gpa 8hp woofers for a very good price and searched the web and of course this forum.
515 midrange should be very good.
my horn is folded, a straight one like the exemplar horn could be better at higher frequency?

the horn should go down to around 40-50hz, low enough in my room. i have 2 m&k 5000 subs, but they are not connected, dont integrate well.
tried the subs with active xover and software, did not like it.

IS IT WORTH EVEN TO THINK ABOUT A CHANGE?
Klaus,

The Exemplar horn looks like it may be a better match for time aligning the compression driver to the cone driver.

Straight horns are generally a bid better in the upper mid range, but you certainly won't convince anybody that has heard a spiral horn like the classic Western Electric horns that they did not have a good midrange.
Those horns used one driver, which eliminates the time alignment and crossover filter issues that multiway systems need to address for accurate sound reproduction.

If the horn outputs don't line up in phase at the acoustic crossover points, they simply will lack the coherency that is possible.

The wavelength of 500 cycles is about 69 centimeters, to be within 1/4 wavelength requires the path length difference to be no more than 172 mm.
Have you tried moving the 511s back so they are in time alignment with your present mid horns?
Acoustical time alignment also may require a polarity swap depending on your crossover, and may not exactly correspond to the physical path length difference.

The reason the subs did not integrate well could also be a time alignment issue.

Anyway, unless you are just itching to make some sawdust, I'd suggest working on time alignment before you EVEN THINK ABOUT A CHANGE in cabinets.

One other detail- if the unused subs terminals are not shorted, they may presently be acting as bass traps, further reducing the output of the folded horns.

Art
 

POOH

Member
2010-10-05 9:06 pm
Ohio
Straight horns can sound better (you say high frequency but i think you mean midrange?) but why not just raise your chair 6" and listen on axis if that's what your goal is. The Exempler horns are too short to be worth pursuing in my experience with them and they have weak bass. They are a step up from the Altec horn bass reflex combo cabinets but are otherwise not worth the wood and time to build them. What would work well maybe to build some proper subwoofers (biamp) that will "keep up" with your present bass horns and maybe upgrading the mid horns for the compression drivers.
 

chaos

Member
2006-09-11 11:04 am
time aligning...this is a major reason to think about it(btw, polarity is swept between midrange and bass). i played around with the 2405 and s2 for a long time, height, distance, the whole thing is VERY sensitive to this, each mm counts.
of course the midrange-bass is not that problematic, but....
the subs...they are no longer in the room and i dont miss them. maybe i try tapped horns later...
there is some itching to try the 515´s in a straight horn.
i did not measure my horns, but i think they go a little lower than an a7. not much.but they sound way better to me,cleaner, not like a paper box. 1,5" plywood on the sidewalls, sand...rounded also on the inside of the horn. heavy.

BUT:: maybe the gpa 515 can do more? in a horn like the exemplar?

the we horns: never heard one of these, i love them anyway, they look just great!!! i thougt about building one of these, the folding is more "gentle" and if i use the space behind my speakers....
time alignment ;-(
 

chaos

Member
2006-09-11 11:04 am
Straight horns can sound better (you say high frequency but i think you mean midrange?) but why not just raise your chair 6" and listen on axis if that's what your goal is. The Exempler horns are too short to be worth pursuing in my experience with them and they have weak bass. They are a step up from the Altec horn bass reflex combo cabinets but are otherwise not worth the wood and time to build them. What would work well maybe to build some proper subwoofers (biamp) that will "keep up" with your present bass horns and maybe upgrading the mid horns for the compression drivers.

crossover frequency, 500hz at the moment:D
the bass.... this is the question!
if something like the exemplars are as good as mine(50hz???), fast, at least as good, and i get better midrange it will be an upgrade.
my speakers are also bass-reflex, but i think it works by accident:eek:
if i can get a compareable bass and better midrange...thats it!
its just a feeling...a straight horn should be better at 500hz.
thats why i ask:)
 

POOH

Member
2010-10-05 9:06 pm
Ohio
They are fake, they only horn load to about 150 cycles. I've heard them in different rooms and find they are better than altec short horn/reflex combos like A7 but are no where near as interesting as a fully horn loaded bass system. The reflex part is the compromise in the tucker exemplar, as is the tractrix flare, as is the short path length. A straight bass horn as long or longer path than your present horn with a larger mouth (not tractrix for bass) is where I would look for improvements in the whole entire pass band
 

steve71

Member
2007-11-12 6:01 pm
I'm starting a project for a straight horn (GPA 515G) to cover down to 60hz with matching polars where it crosses to the an Altec 1003 horn.

Right now I'm using a 80hz conical horn (front loaded) that works well, but I think it can be improved at least in theory.

Shame you don't live close by so we could compare notes. :)
 

chaos

Member
2006-09-11 11:04 am
I know you may think it blasphemy but just removing the cells in the 311 horn will help the on axis sound more than you can imagine. I have done this long ago and it will clean up the on axis sound and not really do much for the off axis response. The 311 horn is thick enough that you will not cause any ringing in the flare.

hm.HM HM this is not the main problem. i will leave the s2 with the rh330 as it is right at the moment. i know that a lecleach may sound better, but i find the round horns in combination with a bass like mine butt-ugly!:drool:
and when i listen to it i also can see it.....
if i change this, it will be made of carbon-fiber anyway.
my 1st thougt was this: build a horn for 80hz, more is not possible in my room and add a sub, all done one the software side.
then i saw the exemplar horn and thougt.......
i was really dissapointed when i tried a software crossover, i was always an analog freak.
i listen to a buff dac, exa u2i usb, perfect, and expected to go along...no way:confused:
i would have liked a software crossover, time delay, equalizing and so on, but it does not work. for me.
 
Chaos,
I understand not wanting to change the 311 horns, but they really do sound better without the cells. On the other point about the crossover I would look at an active crossover in your case. With a proper design you can not only pick your crossover points you can also add time delay if you want to do that and not try and do that with physical alignment that has other problems. If you move the multicell far enough back to time align the two devices you have to remember that then you will have a very reflective surface, the top of the bass enclosure, that will play havoc with the vertical dispersion. I have built many large format bass enclosures though they were for professional sound applications. An 80 hz 1/4 wave mouth size is rather large but I have had up to a 75 hz mouth size horn in my house. Forget about adding any reflex port, they just can't keep up with the horn flare unless you are using an active eq that can overcome the differential and then the power amp requirements will be much greater or you will have problems with excursion playing with not only the lower end but will modulate the horns output. If you are going to use a sub enclosure to fill in below the 80Hz cutoff frequency of the horn then a sealed back of very small proportions is the way to go. This will lower the usable low frequency cutoff of the horn cutoff by a usable amount. If I remember correctly the cutoff becomes 1.2 times lower with this method. The volume of the rear enclosure will be slightly larger than the driver will take up itself. With an exponential flare the volume become V=2.9 x A/R A= the area of the throat and R=the effective flare rate. This equation was developed by Paul Klipsch many years ago and it does work. For what you are doing a curved horn will work just as well as a straight horn and can be much shorter in depth which in a room comes in handy.
 

chaos

Member
2006-09-11 11:04 am
maybe i will try something like an iwata horn on the midrange later?hm, i´m shure i will:D
you describe exactly what i was thinking about, the reflections with a time-aligned midrange horn,and as i understood the whole thing,its not about physically aligning the horns when a crossover is involved.
i also think, an active xover will be better.
so you think, this would be the way to go?:


i played around on horn response, got the results in the attached pics(maybe somebody could the check the input parameters for the 515-8hp?)

i have no equipment to measure my speakers but i listened to some test tones last night.my speaker rolls of earlier than the horn in the simualtion, but the rolloff is not that steep(the open rear chamber?). 50hz is way down, maybe i can get the same lf-response with a straight horn(and it should be way better between 70-100hz)?

thanks a lot for your help!
 

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Chaos,
one thing to remember is that all horns have a downward slope to the curve above a break point in the response curve. Depending on the curvature of a bent horn this will come about earlier in the response curve than a straight horn but if it is a simple smooth curvature it shouldn't be a severe difference. I can't comment on how much a difference there is between a conic horn and an exponential horn in this regards, but because of the improved loading of an exponential horn at lower frequencies it could be greater with this type of design.

I would definitely go with an active crossover, it will be easier to get things right and a delay function should be easily implemented with that type of design. The only problem is you will need multiple amplifiers rather than a single amplifier using passive crossovers.
 

Scott L

Member
Paid Member
2008-12-27 12:32 pm
Knoxville, TN
515 8G

I'm starting a project for a straight horn (GPA 515G) to cover down to 60hz with matching polars where it crosses to the an Altec 1003 horn.

Right now I'm using a 80hz conical horn (front loaded) that works well, but I think it can be improved at least in theory.

Shame you don't live close by so we could compare notes. :)

Steve, Please update us on your progress of your new mid-bass horn design.
I [also] have a pair of 515 8G. I'd love to be able to use them down to 60 Hz, horn loaded.