Pics Altec Open Baffle Bass 'horn'

atilsley · 2013-02-24 4:14 am

Current project is a 3-way 'Altec' horn system, featuring a radical mid bass open baffle 'horn' (wave guide) from Bert Doppenberg (of Oris fame).

http://forum.bd-design.nl/index.php?id=17004

Bert's design uses x4 15-inch woofers each side and is 9 feet tall...mine is the half version.

http://forum.bd-design.nl/index.php?id=17095

I will use x4 Altec GPA 416's (I already have two).

At this stage, mid horn will be the Eliptrac 400Hz, DIY with MDF. Driver likely Altec GPA 390.

Eliptrac 400

http://www.greatplainsaudio.com/downloads/390series.pdf

Tweeter horn is the Visaton TL16.

All fun stuff.

Pano · 2013-02-24 4:26 am

That's going to be a big speaker! :up:

POOH · 2013-02-24 4:49 am

How low does the horn load? It looks like around 200 HZ? What will you use for bass?

atilsley · 2013-02-24 8:50 am

Bert is surprised to get good response well below 100.

Earlier, I built dual tapped horns from volvotreter design....so I can re do those again.

Main goal....best mid bass attack from any speaker.

atilsley · 2013-02-24 9:07 am

POOH said:
How low does the horn load? It looks like around 200 HZ? What will you use for bass?

http://forum.bd-design.nl/index.php?id=17043

See bert's comments re bass.

Also, 150hz@ 112dB not bad.

POOH · 2013-02-24 4:20 pm

150 is probably where the horn unloads so probably it is 88db at 75 and 64 db at 37.

POOH · 2013-02-24 4:37 pm

POOH said:
150 is probably where the horn unloads so probably it is 88db at 75 and 64 db at 37.

Best mid bass attack I can come up with is a single horn loaded 10" covering 100 to 1.5K at around 107 db/w to 1k and 3 db down at 2k. Has lots of SNAP and power

atilsley · 2013-02-24 8:38 pm

POOH said:
Best mid bass attack I can come up with is a single horn loaded 10" covering 100 to 1.5K at around 107 db/w to 1k and 3 db down at 2k. Has lots of SNAP and power

Yeh...I built a Jon Inlow 100hz horn using B&C 12 incher...good response alright.

See DIY audio link of that horn build here...

http://www.diyaudio.com/forums/multi-way/213849-pics-new-4-way-horn-rig-underway-2.html

For this project, though, I need speakers that don't protrude 100cm into my room....which happens to be family/lounge room. This is why this wave guide is 120cm wide, but only 55 deep.

puppet · 2013-02-24 10:27 pm

Can you do something like this with say a sealed four way design?

POOH · 2013-02-25 1:12 am

atilsley said:
Yeh...I built a Jon Inlow 100hz horn using B&C 12 incher...good response alright.

See DIY audio link of that horn build here...

http://www.diyaudio.com/forums/multi-way/213849-pics-new-4-way-horn-rig-underway-2.html

For this project, though, I need speakers that don't protrude 100cm into my room....which happens to be family/lounge room. This is why this wave guide is 120cm wide, but only 55 deep.

It's tough to back to boxes after using horns, NICE horns you built, but with limited room maybe a line array with the Altecs would be good without the front horn and in a box? I imagine it would still be pretty sensitive without the front horn and without an open back wave screwing with the bass response?

atilsley · 2013-02-25 5:38 am

POOH said:
It's tough to back to boxes after using horns, NICE horns you built, but with limited room maybe a line array with the Altecs would be good without the front horn and in a box? I imagine it would still be pretty sensitive without the front horn and without an open back wave screwing with the bass response?

Yeh, struggled quite a bit with ideas...but there's something quite nice about the concept and look of this large wave guide. I'm pretty comfortable with the specs...and I understand I'm trading a little bass depth for bass attack.

I've built heaps of speakers before, Tannoy GRF, Cornscala, Bill Fitzmaurice horn subs, Lowthers...plus designed my own radical C-Horn. I'm also a licensed builder for the Carfrae Little Big Horn. Have also built large bass horns for US GOTO rep, Ming Su.

See pics attached.

New C-Horn Released | Hi-Fi

Carfrae Little Big Horn from Creation Audio | Hi-Fi

At the moment, I'm just taken by Atltec and front horns.

Cheers.

atilsley · 2013-02-25 5:42 am

Here's a modern take on the Jensen Imperial I developed using my CNC'd method.

SAC · 2013-03-20 12:47 am

Any update on this build? I am wondering if Alpha15 drivers (3 per side) would work in this configuration, albeit with a much shortened wave guide.

atilsley · 2013-03-20 1:24 am

SAC said:
Any update on this build? I am wondering if Alpha15 drivers (3 per side) would work in this configuration, albeit with a much shortened wave guide.

Sorry, SAC, not a lot more on the project. In fact, I'm building an Altec 620/Shindo style cabinet to house my Altec 416's. I'll revisit the Open Baffle again though.

I have a mate who needs a good mid bass to improve his Avant Garde Duo's. He has a height restriction of 70cm...so I may convert my version into either a single driver version, or a standard front loaded horn, not unlike Volvotreter, attached.

Midbass Horns

The mouth would be quite wide, eg 95-100cm, with the height 70cm. The depth would be retained per the existing flare, which is about 55cm. The 416 would work very nicely in this config...but I'd have to close in the horn and build a back chamber.

Spotted the attached pic recently, which shows a small horn placed inside/at the top of an open baffle....nice.

I think your x3 Alpha's would be great...but your min height would be around 130cm, no?

SAC · 2013-03-20 9:58 am

Thanks for the reply. I've never heard horns in home audio so can only imagine. Skills and knowledge are limited so its being either full range driver sealed or four way open baffles (PLLXO).

I have squeezed my three drivers into 1220mm height - you ask due to listening height issue I suppose. I am hoping to keep my higher frequencies dipole in a Nao Note clone setup (John Krekovsky upper panel design - 8", 3" and tweeter). Since the drivers will be all or mostly in an independent baffle they can be tilted downwards for listening height allowances, or mounted completely independently even (think Stigerik setup; H-frame subs and those big BG brand planars).

To make use of all my drivers but keep the height down I am considering making the bottom driver a push-pull pair (two 8ohm drivers in parallel), the one above will be the 4ohm I have, and the third hole above can house my 8" drivers.

Admittedly I use these by a projector screen in a narrow room, so it would be a really small waveguide - 50cmX20cm depth - perhaps pointless in this design. Should I just make some h-frames instead?

That picture must be the A820i.
A820i 'Design' Model 2 | Wolf von Langa

Sean

picowallspeaker · 2013-03-20 10:11 am

SAC said:
That picture must be the A820i.
A820i 'Design' Model 2 | Wolf von Langa

Sean

From that page

As far as I know there never has been a (DIY) loudspeaker in this quality and amicability.

...the fool on the hill

GM · 2013-03-20 12:22 pm

atilsley said:
I will use x4 Altec GPA 416's (I already have two).

Any particular reason why you're apparently not using Altec's many decades long proven mid-bass horn alignment for this series driver?

GM

atilsley · 2013-03-20 9:17 pm

Sean. Yes, pic of Wolf's field coil rig.

GM, not quite sure how to answer. Altec hasnt really dabbled in open baffle, so we're in new territory. Are you saying bert Doppenberg doesn't know his stuff...?

GM · 2013-03-20 10:12 pm

When did he start using Altec/GPA woofers? All the 15" designs I've seen for many a moon now all use his BD15, which historically has a somewhat different set of specs, break-up modes BW than the 416, though his original was similar to the 515-8G IIRC.

WRT the design concept, I wish I still had the files from a looong thread on the Decware? forum back the better part of a decade ago where I 'walked' 'johninCR' through a dipole front/rear WG loaded 'FR' driver build and he was so pleased with it after trying all manner of cab alignments including MLTL, Jensen BLH, Karlson and a strange hybrid that caused me to suggest it that he quit experimenting and left the forums completely soon after AFAIK.

I guess my point is that when sufficient space, budget is available, why 'settle' for ugly, so-so efficiency 'H' frames when one can make an elegant 'statement' with superior performance to boot?

Frankly, I'm surprised it's taken so long for them to be [re]'discovered' yet again as I can't claim any originality either.

GM

atilsley · 2013-03-20 11:50 pm

GM said:
When did he start using Altec/GPA woofers? All the 15" designs I've seen for many a moon now all use his BD15, which historically has a somewhat different set of specs, break-up modes BW than the 416, though his original was similar to the 515-8G IIRC.

WRT the design concept, I wish I still had the files from a looong thread on the Decware? forum back the better part of a decade ago where I 'walked' 'johninCR' through a dipole front/rear WG loaded 'FR' driver build and he was so pleased with it after trying all manner of cab alignments including MLTL, Jensen BLH, Karlson and a strange hybrid that caused me to suggest it that he quit experimenting and left the forums completely soon after AFAIK.

I guess my point is that when sufficient space, budget is available, why 'settle' for ugly, so-so efficiency 'H' frames when one can make an elegant 'statement' with superior performance to boot?

Frankly, I'm surprised it's taken so long for them to be [re]'discovered' yet again as I can't claim any originality either.

GM

I hear you. I guess, though, there's something still quite appealing about the OB design...I think the aesthetics are very much a statement...just take a look at Bert's full 4-driver/side verison. Besides aesthetics, I would suggest little/no coloration from the design would be worth persuing....certainly that's the logic behind most people's OB goals. (Remember, the goal of this project was max mid-bass attack.)

As to the 416's vs Bert's woofers, yes, I accept the differences...but I'm confident about the outcome, as the 416 is such a versatile driver, and the flare is not dissimilar to the A5/7. For bass depth, either an EQ'd approach or separate dual tapped horns will be used.

What do you have in mind when you say, "an elegant 'statement' with superior performance to boot?"

Kindly

Pics Altec Open Baffle Bass 'horn'

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