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Old 31st March 2014, 01:38 AM   #1
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Default La petite Onken

Hi everyone,

I'm actually motivate to build a new pair of speakers. My recent reading from the old L'Audiophile magazine make me developed a special interest for the petite Onken as described by Jean Hiraga (Audiophile n. 25, september 1982):

http://www.asrr.org/biblioteca/Revue%20 ... ONKEN.html

Considering the Altec 414-8B associated with them, do you guys think it's better to find a used pair or buy a 414-8B reedition from Great Plain Audio?

http://www.greatplainsaudio.com/downloa ... 0Sheet.pdf

At this time, the main challenge for me seems to decide with which horn driver I will design it. A member on French forum Elektor use a TAD TD2001 in a two ways design, a design which I like. But the TAD is VERY expensive. So if some of you could suggest other options, I'm willing to read them. I imagine that the cross-over will held at around 650 Hz. So, I'm looking for a horn driver with a good linearity between 500 Hz to 20 000 Hz.

Thank you,

Sébastien
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Old 31st March 2014, 06:52 AM   #2
DrBoar is offline DrBoar  Sweden
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Faital Pro LTH142 horns and one of their 1.4" drivers. Their compression drivers are supposed to be really really good. One such iteration at
Cornscala Style D | Critesspeakers.com
Crites refer to the TAD TD4002 in the text...

an other scaled down to 12" and 1"
Beyma 12″+Faital 1″+horn |
There are more places around the net with people that have good things to say about those horns and drivers.
With a sharp active crossover analog or digital the horns can be used quite low in a domestic setting. If you use a passive crossover you have to be more careful.
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Old 31st March 2014, 04:32 PM   #3
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Hi DrBoar, hi everyone,

I think that I found an interesting path with some Radian compression drivers. Some folk comment that the 475PB is pretty similar to a TAD TD2001, but for a far cheaper price.

Plus, some other Radian also present a good linear frequency response from 600 Hz to 20kHz.
That's the case with the Radian 745PB and the 850PB.

Sébastien
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Old 1st April 2014, 04:13 AM   #4
GM is offline GM  United States
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Greets!

Unless you or a knowledgeable friend knows the history of a pair and they are original used in a HIFI app or at least recently been re-coned, remagnetized by GPA with documented T/S measurements, then buy new as there’s too many ignorant and/or disreputable folks trying to capitalize on the Altec name and even GPA has been known to do way out of spec re-cones.

AFAIK though, GPA’s new drivers have been very close to spec [or arguably better in some cases] and when adjusted for inflation, no more expensive than the originals, so all things considered, I consider them a relative bargain by today’s standards.

That said, plugging its published specs into Hiraga’s formula yields a 106.91L/40.14 Hz alignment, so ~1/3rd smaller and tuned a bit lower than his 155 L/45 Hz, so some cab fine tuning may be required.

WRT horn/driver choice, I don’t know what the original mini-Onken used, but the ‘sweet’ spot for a wide BW 12” in general for a 90 deg horn [-6 dB] is ~1356 Hz and ~1500 Hz for the 414 in particular based on their own polar mapping of various 12” drivers, so to my way of thinking, a lower XO point is kind of a waste of much of the 414’s ‘magic’.

At ~1 kHz, its response is still ~ ‘setting’ on the baffle [~160 deg/-6 dB], so any lower XO point is basically just a waste of a pair of excellent wide BW drivers, not to mention limits one’s HF driver choices.

I queried the late JMMLC some years ago WRT the Altec 802-8G [the best overall performing 1” driver I’ve used] Vs the TAD TD-2001 Beryllium after he had mentioned doing some comparisons on his own system and he considered the latter’s better HF performance differences were subtle at best, so I concluded that it’s probably a waste of $$$ unless ones hearing is still youthful/undamaged.

Note that this was before GPA released its Series II version though, which if its published response plot is accurate, maybe reduces the already subtle differences to the point where only a child’s or young adult female’s keener mids/HF hearing might make the extra cost worthwhile.

Assuming at least a 1 kHz XO, DIYing an original ~212 Hz Unity WG [less mids holes, mounting of course] would be my choice or at least a 500 Hz expo horn.

GM
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Old 2nd April 2014, 12:17 AM   #5
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Hi GM, hi everyone,

GM, your post is of great interest and contains a lot of informations. Meanwhile, I had the chance to talk to a member on Elektor which build the petite Onken and he told me that in its design, the Altec 414 goes up to around 800/850 Hz at 6 dB/oct then the TAD TD2001 covers all the way upper.

Regarding the cross-over freqency, I don't have any problem to set it between 800 Hz and 1000Hz. Plus, you are right, there is a lot more choice in that range in the intention of a two ways design. I think that I stick on the cross-over suggested by Jean Hiraga in L'Audiophile magazine back in the days.

When you talk about cab's fine tuning, you mean that all of it would have to be redraw do you? On my side, I was looking for a project with the plan already available.

Regarding GPA, I couldn't find any graph with frenquency response. If anyone could oriented me to get them, I'll be happy. I already send them an email yesterday but no answer yet...

Finally, there are few things in your post that I don't understand. What do WRT, WG and expo horn mean?

Thanks again,

Sébastien

Last edited by SebastienL; 2nd April 2014 at 12:26 AM.
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Old 2nd April 2014, 01:52 AM   #6
kevinkr is offline kevinkr  United States
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WRT = with regard to

WG = wave guide

expo horn = exponential horn (I think)

I run full sized Onkens and am very pleased with their overall performance. I would recommend you get the new GPA 414-8B for all the same reasons GM mentioned.

I would cross closer to 1kHz than 800 were I you..

The Petite will be a lot of fun to build and listen to.

OT: Son et Image was interesting.
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Old 2nd April 2014, 04:05 AM   #7
GM is offline GM  United States
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Quote:
Originally Posted by SebastienL View Post
I think that I stick on the cross-over suggested by Jean Hiraga in L'Audiophile magazine back in the days.

When you talk about cab's fine tuning, you mean that all of it would have to be redraw do you?

Regarding GPA, I couldn't find any graph with frenquency response.

What do WRT, WG and expo horn mean?
Greets!

You're welcome!

What XO did Hiraga recommend?

Well, the cab could be redesigned, but not a good plan unless you use actual measured specs of the drivers you buy; otherwise in the case of a fixed vent design such as the Onken, one normally will either use some form of EQ and/or stuffing density to smooth it out and/or block off one or more of the vents to tune it lower.

Haven’t seen a GPA response plot for the 414 and no longer have any originals, though the 802-8G SII has one in its specs pdf: http://www.greatplainsaudio.com/down...ec%20Sheet.pdf

I see Kevin has already defined my [audio] 'net lingo’ that I’m notorious for.

For the non-audio related ones such as 'WRT', these are all listed here: NetLingo The Internet Dictionary

GM
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Old 2nd April 2014, 12:59 PM   #8
Eldam is offline Eldam  France
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Quote:
Originally Posted by SebastienL View Post
Hi everyone,

I'm actually motivate to build a new pair of speakers. My recent reading from the old L'Audiophile magazine make me developed a special interest for the petite Onken as described by Jean Hiraga (Audiophile n. 25, september 1982):

http://www.asrr.org/biblioteca/Revue%20 ... ONKEN.html

Considering the Altec 414-8B associated with them, do you guys think it's better to find a used pair or buy a 414-8B reedition from Great Plain Audio?

http://www.greatplainsaudio.com/downloa ... 0Sheet.pdf

At this time, the main challenge for me seems to decide with which horn driver I will design it. A member on French forum Elektor use a TAD TD2001 in a two ways design, a design which I like. But the TAD is VERY expensive. So if some of you could suggest other options, I'm willing to read them. I imagine that the cross-over will held at around 650 Hz. So, I'm looking for a horn driver with a good linearity between 500 Hz to 20 000 Hz.

Thank you,

Sébastien
You can also had a little 5" in OB like the good maid one by EMS speaker (they also without electric magnet) between the Onken and the horn for a faster and more realistic mid-bass to mid-tweet (let say around 200 to 1200 Hz) but maybe more a little more with the High pass because the OB and the small area.... but these one at EMS Speaker was maid if I remember for mid OB use with a very low QT < 0.20.

The plywood is important for the cabinet of the Onken, maybe some fellows at Melaudia.net could help you, they maid many Onken.

Last edited by Eldam; 2nd April 2014 at 01:02 PM.
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Old 2nd April 2014, 02:43 PM   #9
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Quote:
Originally Posted by kevinkr View Post
WRT = with regard to

WG = wave guide

expo horn = exponential horn (I think)

I run full sized Onkens and am very pleased with their overall performance. I would recommend you get the new GPA 414-8B for all the same reasons GM mentioned.

I would cross closer to 1kHz than 800 were I you..

The Petite will be a lot of fun to build and listen to.

OT: Son et Image was interesting.
Hi Kevin,

Thanks for the explanations regarding the terms. I was not used to them.

It appears that the GPA 414 should be the right way to go. Only, I'm not equiped to make some mesures and I'm more interested to build the cabs and the cross-over but to follow a design already tried. This said, the Petite Onken seems to be a really nice speakers and I'd really like to move to a compression driver for mids and highs.

Unfortunately, it's the first time in 3-4 years that I choose not to go to the SSI. I went to the Montreal's DIY day in the beginning of March. That was it for this month. :-)

I presented there my AMA 3x100 speakers. You can see them there:

AMA 3x100 (3 voies, 100 dB) - Page 14

Have a good day,

Sébastien
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Old 2nd April 2014, 04:13 PM   #10
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Quote:
Originally Posted by GM View Post
Greets!

You're welcome!

What XO did Hiraga recommend?...

GM
Hi GM, hi everyone,

Finally, I realized that the cross-over frequency of 600-650 Hz I had in my mind was more from Francis Ibre's Bien entendu, itinéraire d'un audiophile book than in Hiraga's article in L'Audiophile. My mistake. Ibre suggest that with such a design in two ways with a 12" woofer, the cross-over to the second way is aroud those frequencies. He says after that it's hard to find a good compression driver that could do the job. Hence the TAD TD2001.

After my reading, I realized that the member on Elektor's forum with the Petite Onken with TD2001 have a cross-over set at around 800-850 Hz, inspired by Hiraga's one applied to the VOT as described in Sound Pratices magazine number 11.

Have a good day,

Sébastien
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