Tweeters to match those Altecs

Altec Open Baffles, etc.

Tweeters to match those Altecs

Postby vintage_dog » Sun Jan 23, 2005 12:23 am

i love the 403A OB, but, on some passages i wish i get a little more extension on the highs. i'd like to experiment with a few tweeters. any suggestions on tweeters that will match the Altecs?

any tips on placement (of tweeter) on the OBs?

thanks
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Re: Tweeters to match those Altecs

Postby setup1 » Sun Jan 23, 2005 1:49 am

vintage_dog wrote:i love the 403A OB, but, on some passages i wish i get a little more extension on the highs. i'd like to experiment with a few tweeters. any suggestions on tweeters that will match the Altecs?
any tips on placement (of tweeter) on the OBs?
thanks


Here's a list of what I've tried and lived with in my system in the order of preference. Applicable not only on OBs but also in any 2-way horn/BR woofer combo that needs help on top.

Expensive vintage horns:
1. Altec 3000
2. Electro-Voice T35
3. Pioneer PT3K

Expensive alternatives I've heard in other systems.
Modern - Fostex T90, T925 and T900
Vintage - Jensen RP302 and JBL 2405

Budget stuff I tried in my system
modern horn - Fostex FT17H
Vintage cone - Jensen P35VH

Cheaper possibilities are 2"-5" vintage Japanese cone type tweeters with alnico magnets hacked from old consoles, TVs or department store speakers sold with 'compact systems'. Cone type tweeters from old German radios have great following they can be cheap or expensive depending on the seller. Likewise, don't overlook cheap horn or cone tweeters from Dai-Chi or Micro. Who knows maybe they are good.

Joel is experimenting with cheap Chinese OEM ribbon tweeters on his 755C maybe he can offer some insights. Expensive ribbon tweeters might work too but given the price and fragility due to their impedance characteristics [not good for SE amps] I'd go for vintage horn tweeters or Fostex.

I've never used a cap greater than 1 uf [paper is my favorite] and a variable L-pad is mandatory to season it to taste or else one goes crazy changing resistors or finding exact values. Check my speaker building tips page for a crossover calculator link and other info: http://members.myactv.net/~je245/spktips.htm. There are several pages of information on speakers at my website that can be helpful too so please check the other links I posted in this forum.

On the OB I always place the tweeter on the top shelf which sounds fine because I'm at least 2 meters away. If you sit closer the tweeter might not integrate as well. In this case, once you've chosen your tweeter, you can mount it as close as possible to the fullrange driver just like a conventional two-way system to simulate a point source.

JE
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Postby vintage_dog » Sun Jan 23, 2005 11:09 am

thanks Joseph. i got a loaner vintage horn from john poscablo and will experiment with it. will check-out your site for more info.
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Postby setup1 » Sun Jan 23, 2005 2:05 pm

vintage_dog wrote:thanks Joseph. i got a loaner vintage horn from john poscablo and will experiment with it. will check-out your site for more info.


IME, for super tweeter duty you have to use a very small format horn for best results like the 3000A at the center of the Altec 601 pic posted by Arnold for Tony M. Anything larger than a Jensen RP103 is more like a midrange or upper midrange horn and depending on quality will normally roll off around 13khz. As good as Altec 811/802D combo is dispersion is a bit compromised @ ~ 15-18khz. That's the reason I use a 3000H or T35. Try a Fostex if you have access.

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Postby Audioboy » Mon Jan 24, 2005 6:33 pm

guys,

please recommend a local store where i can get l-pad for this project.
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Postby Audioboy » Sun Feb 13, 2005 7:29 am

Audioboy wrote:guys,

please recommend a local store where i can get l-pad for this project.


already got a pair.

Here's a pic of horn (Dai-ichi PT-6) installed on my OB.

Image

L-Pad and 1uf siemens porcelain cap (from john p.)

Image
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Postby setup1 » Tue Feb 15, 2005 2:13 am

Audioboy wrote:already got a pair.
Here's a pic of horn (Dai-ichi PT-6) installed on my OB.


Congratulations! This is the DIY spirit I've been waiting for. That is the Dai-ichi tweeter I saw during my last visit, could you share some comments on the unit?

L-Pad and 1uf siemens porcelain cap (from john p.)


In case you experience some harshness that can't be tamed by the L-pad, try using a .5-.75uf cap instead. Better yet if you have 4 of those Siemens, connect a pair in series. Joel and I have been exchanging notes about cap values and so far we agree that .68uf seems to be a good value for super tweeter duty for FR drivers that go up to over 10khz. But if you're happy don't mess with it.

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Postby Audioboy » Tue Feb 15, 2005 11:14 am

setup1 wrote:
Audioboy wrote:already got a pair.
Here's a pic of horn (Dai-ichi PT-6) installed on my OB.


Congratulations! This is the DIY spirit I've been waiting for. That is the Dai-ichi tweeter I saw during my last visit, could you share some comments on the unit?

L-Pad and 1uf siemens porcelain cap (from john p.)


In case you experience some harshness that can't be tamed by the L-pad, try using a .5-.75uf cap instead. Better yet if you have 4 of those Siemens, connect a pair in series. Joel and I have been exchanging notes about cap values and so far we agree that .68uf seems to be a good value for super tweeter duty for FR drivers that go up to over 10khz. But if you're happy don't mess with it.

JE


the horn is rated at 94db sens while my 403a at 95db. i think i made a mistake in getting a pair of horn rated below the sens of my 403a. the l-pad has somehow lost its purpose in attenuating the horns. i have set the L-pad to maximum because it is in that level that integration of the horn and the driver is attained. however, i experience a magnitude of harshness whenever i set the l-pad to maximum. i'm glad you have mentioned a cure for the harshness. I will try that soon and give you a feedback on this regard. perhaps, a comment about the horns will be in order once i am through with the caps.

thanks for the support!
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Postby ichabod » Tue Feb 15, 2005 4:15 pm

My question should get an answer later. Just wanna know how well both drivers integrate as point sources. Thanks.
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Postby Audioboy » Wed Feb 16, 2005 12:46 pm

i was able to get from john poscablo a pair of .68uf caps which i immediately installed last night. the result was great, indeed the harshness was tamed.

i had a brief time listening to the horns with the newly installed caps but will try to give impressions about them.

i tried comparing them with the tweeters of my epos 14 and found out that the horns somewhat lack extension and have the tendency to present imaging smaller in size. the midrange overshadows a bit the HF. This i believe is caused by the lower effeciency of the horns than the 403a speakers. the discrepancy however is not too bad. 1db or 2db plus on the horns could have made the combi almost perfect.

i've asked dai-ichi if i can return the horns and get another with higher db. they have answered in the affirmative but will have to inspect them if they are still in good condition. i am having second thought though of getting those 10 1/2" by 4" horns. masyado atang malaki!
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Postby setup1 » Wed Feb 16, 2005 11:22 pm

Audioboy wrote:i was able to get from john poscablo a pair of .68uf caps which i immediately installed last night. the result was great, indeed the harshness was tamed.

i had a brief time listening to the horns with the newly installed caps but will try to give impressions about them.

i tried comparing them with the tweeters of my epos 14 and found out that the horns somewhat lack extension and have the tendency to present imaging smaller in size. the midrange overshadows a bit the HF. This i believe is caused by the lower effeciency of the horns than the 403a speakers. the discrepancy however is not too bad. 1db or 2db plus on the horns could have made the combi almost perfect.

i've asked dai-ichi if i can return the horns and get another with higher db. they have answered in the affirmative but will have to inspect them if they are still in good condition. i am having second thought though of getting those 10 1/2" by 4" horns. masyado atang malaki!


A few things:
1. When I use a super tweeter, I don't try to "overlap" as in a typical crossover. I try to "fill in" the top end missing from the natural falling HF response of the fullrange driver. The super tweeter's duty is just to add a bit of an "airy sheen" like the decay of a brushed cymbal. The effect should be subtle and many times you shouldn't even notice that it's there. Thus IMHO, comparing the HF characteristics of the OB/403A + super tweet [x/o ~ 11khz] to a traditional 2-way Epos14 [x/o 3-5khz, my guesstimate?] is like apples and oranges because from 3khz to 11khz you're hearing mostly the 403A against the Epos tweeter.
2. I don't think the 1-2dB discrepancy in sensitivity/efficiency is that significant since at the natural mechanical roll off at the top end of the 403A, it's response in terms of sensitivity/efficiency @ 9-11 khz is probably much less than the 95dB spec.
3. It's possible that the PT-6 just looks much better than it can perform. Do you know what type of diaphragm it uses? [Mylar, phenolic or aluminum?] Is the horn metal or plastic on this model?
4. You can experiment further by changing to an even lower value cap as well as fiddling with the L-pad. If this doesn't help then the driver is probably not up to task.
5. I will not use a larger horn even if the specs look better because as the mouth of a horn gets larger the HF tend to get more diffused. This is the reason why I add a super tweeter on top of the 811/802.

James, I think I answered your question in #1.

JE
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Postby ichabod » Thu Feb 17, 2005 8:09 am

Thanks for doing so. My concern really stems from the fact that I've been going away from the effects (tendencies to sound thin and unnatural) of tweeters. I'm okay with the full range range because I still hear the high frequencies (just enough for me maybe in the manner you have described it here but of course that's me) just as I want them.

I read someone yesterday someone asking questions about a siemens speakers at the Klangfilm site what else does he need to do and know about full rangers. And the swift answer was it had enough range for most hifi listening, and one only need put them on OBs.

I'm not trying to tell audioboy what he feels he needs on those altecs for extensions if he finds the sound rather bland and rolled down. Most of us coming from super tweeters (extended ones in modern speakers) will have to contend with that fact when listening to full range speakers I think. For some I know that's where the fun begins!

I know a guy who listens to maggies and say in the end he's beginning to like the OBs because he thinks it's the more natural sounding in quite the same vein as the LS 3/5a. He likes the sound of the piano (three blind mice recordings specially) on these ceramic altecs 403As.

Someone has to go figure that.
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Postby setup1 » Thu Feb 17, 2005 9:29 am

Hi James,

I assure you we are talking the same language here and agree with everything you pointed out. I've graduated from most sizzly and sibilant dome tweeters which project most of their energy in the 5-13khz range which we've come to know as "high-frequency". However to clarify a point, the DIY/SET/Hi-efficiency crowd definition of super tweeter is different from most high-end credos. Its application is to add harmonic richness to the top-end that is very subtle. It's hard to use words to describe the sonic effect but for instance when I listen to a Bill Evans trio recording on my OB/755C + 3000 or the Altec 2.5-way horn, without the 3000, the brushed cymbal decay will be shorter and drier, adding the 3000 will give it a bit more vibrancy and atmospheric air. OTOH if the highhat isn't playing it's as if the 3000 isn't there at all. It's that subtle.

Another tip to potential super tweet experimenters, if you notice added sibilance on male and especially female vocals the super tweeter is cutting in at a much lower frequency than it is supposed to. I'll never endorse the use of a super tweeter that messes up the midrange that's why I recommend starting with a cap value of 1uf and working your way down in conjunction with a variable L-pad. You'll be surprised that when you plug in a nominal 8 ohm tweeter with a 1uf cap the a 1st order 6dB/slope x'over design calculator will give you a 20khz crossover point which from my experience can still potentially yield a harsh sound depending on driver quality even with suitable L-padding.

But as James pointed out, if you are already enjoying your system even with a slightly rolled off top end why mess with it.

JE
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Postby ichabod » Thu Feb 17, 2005 10:06 am

Enjoyed reading your comments there JE.

I can see and "hear" Joel's set-up (2) in your explanation of that "richness," "atmosphere" and all that verve.

Guess what? I've been doing comparisons lately between my LS and the OBs on that "extension" issue. And to be honest, I can live with them OBs specially on a majority of CD recordings that are quite revealing on my LS 3/5a. If anything is missing at my nearfield listening position, it's just a little of that harshness caused by the tweeters. But I've found the right amp for the LS 3/5a without losing that hi frequency clarity while managing to downplay that tweetery chirp. My altecs may or are just a little less on the top, but it's midrange clarity and "rightness" are more than enough to tell me all about the music.

I guess a friend was correct telling me that altec don't make tweeters. The idea about extensions and the human hearing is best served in areas where "subtlety" is more important than mere extensions.

Fire away. I'm with you.
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Postby red76 » Thu Feb 17, 2005 12:28 pm

Hi Audioboy,

Lovely OB's. Those Dai-Chi's look like diffraction horn tweets. Try to mount one vertically (as opposed to how it's mounted now) and compare how it sounds. Also try to lower the the cap value to 0.47uF oilers if you can find 'em. You can also try removing the L-pad in the network, just to hear if the harshness/grittyness would still be present... Just some suggestions for tweaking. Happy listening.

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Postby arnoldc » Thu Feb 17, 2005 12:48 pm

audioboy, benta mo sa kin L-PAD mo :)
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Postby Audioboy » Thu Feb 17, 2005 1:22 pm

arnoldc wrote:audioboy, benta mo sa kin L-PAD mo :)


sa phasetron mayron. :)
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Postby Audioboy » Thu Feb 17, 2005 1:26 pm

red76 wrote:Hi Audioboy,

Lovely OB's. Those Dai-Chi's look like diffraction horn tweets. Try to mount one vertically (as opposed to how it's mounted now) and compare how it sounds. Also try to lower the the cap value to 0.47uF oilers if you can find 'em. You can also try removing the L-pad in the network, just to hear if the harshness/grittyness would still be present... Just some suggestions for tweaking. Happy listening.

fred


thanks fred. will try your suggestions.
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Postby arnoldc » Thu Feb 17, 2005 1:30 pm

audioboy, mag Aurum Cantus G2si na kaya tayo? :twisted:
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Postby setup2 » Fri Feb 18, 2005 3:53 am

Audioboy, nice OB set-up and I like the vintage looks of those Dai-ichi PT-6.

Like JE, in adding the super tweeter, we are just trying to add a little air... I have been experimenting with the 755C and some vintage horn tweeters and JE have mentioned my findings...

As for JE's statement, 'harshness... can't be tamed by L-pads', I think it can be explained by the descriptions stated at the 'Xover Calculators' site for L-pads, they are just to attenuate and doesn't affect frequency response...

Hope you can find the right combination to enjoy the music... trust you ears...

Regards,
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