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View Full Version : Adding a tweeter to Altecs



rloggie
11-19-2004, 11:02 AM
I have a pair of VOT Magnificents that I would like to add a tweeter to. The speakers are in remarkable condition and I would prefer to leave them intact and use an externally mounted tweet and crossover. I've looked at the JBL 075's as a canidate, but would like to hear any sugguestions. Thanks to all.
Robin

GordonW
11-19-2004, 11:09 AM
The 077/2405 slot definitely goes higher in frequency than the 075/2402... I'd be inclined to do that.

Otherwise, the Fostex FT17H horn would be a good choice. Very efficient, very flat out to like FORTY KILOHERTZ! Now, THAT'S a SUPER-tweeter!

Regards,
Gordon.

rloggie
11-19-2004, 07:43 PM
The 077/2405 slot definitely goes higher in frequency than the 075/2402... I'd be inclined to do that.

Otherwise, the Fostex FT17H horn would be a good choice. Very efficient, very flat out to like FORTY KILOHERTZ! Now, THAT'S a SUPER-tweeter!

Regards,
Gordon.
How would you crossover the highs? Can I just tap off of the existing horn? What vintage crossover could I use to best benifit or is there a better way?

GordonW
11-19-2004, 09:21 PM
Anyone see any problem with him just hooking up something like an N8000 BEFORE the speaker cabinet, and just sending the low pass into the Magnificent and the highpass into the 075/077? It'd be staged in reverse to the normal way these are used, but as long as the crossovers are made to be cascaded (which I know an N8000 is), it shouldn't matter much which order, right? I'd not expect the Magnificent crossover to have any wild impedence issues, right?

If this is do-able, then the Altec wouldn't have to be modified at all... it'd just be a "black box" receiving the low pass of the external crossover...

Regards,
Gordon.

rloggie
11-19-2004, 10:02 PM
Thanks for the input! I'll look around for the components. The 075's and the 077's seem to bring about 450 on Ebay. (I have an extra pair of N500-e Altec crossovers I'd like to sell or trade for something that would work.)

Todd W. White
11-19-2004, 10:20 PM
If your Altec MAGNIFICENT's are working properly, they go way up there by themselves. Is there a particular problem you're having with them that would make you want to add supertweeters?

rloggie
11-19-2004, 10:27 PM
No problems at all and they sound terrific! I have had some Khorns in the house and thought the highs might have been somewhat better. That was the only thing that was better though. I just though that the VOT speakers were said to benifit from the addition of a "supertweeter". Call it a test. Obviously I don't want to in anyway alter the speakers I have, therefore the external setup so that I can revert to the way they are now. :D

Robin

Todd W. White
11-19-2004, 10:38 PM
Well, if they sound great, why mess with them?

The 802 in the MAGNIFICENT, particularly if it has the original diaphragm (not available at this time - maybe soon), has excellent frequency response to the upper limits of human hearing. Inaudible upper harmonics notwithstanding, I never used a supertweeter with them, as I found that all of the music that I could hear (my last test had me out to 17.5 kHz - I'm 44) was there with the standard driver/horn combo.

The only things I would do is firm up the cabinet, make sure the speakers are performing up to spec, dampen the horn, calibrate it properly, and ENJOY!

Saves money too - supertweeters and their related paraphanalia can get expensive...why buy stuff that you can't hear?

rloggie
11-19-2004, 10:44 PM
What exactly would I do to calibrate the horn? Any easy test to see if they are performing up to spec? I'm 57 and, of course, have high frequency hearing loss. If I could determine that the speakers were performing to their max I'd be less anal about tweeking. I'll will be damping the horns.

John Sheerin
11-20-2004, 05:15 PM
Otherwise, the Fostex FT17H horn would be a good choice. Very efficient, very flat out to like FORTY KILOHERTZ! Now, THAT'S a SUPER-tweeter!

Regards,
Gordon.
Gordon,
Have you actually measured that? If so, maybe I have a dud - mine starts rolling off above 10k. Sensitivity is also only spec'd at 98dB iirc, so not really in the same range as some more expensive items.

John

pat_altec
12-29-2004, 06:14 AM
Robin

I can suggest you to use as tweeter an electro voice ST350A or B

Patrick

Maron Horonzakz
12-29-2004, 06:59 AM
The EV st350 due to its phenolic diaphram do not do mutch above above 15k.. I would recommend JBL 2404 or 2405 good to 21.5k

Robh3606
12-29-2004, 07:38 AM
Hello rloggie

You have any test equipment?? I use an RTA to set things up and balance out the drivers in my speakers. You could purchase something like a Behringer 8024 or go the PC route with software. Either way will work well and give you the tools you need to take some basic measurements that won't cost you an arm and a leg. I will post a link for software. If you go that route you need a measurement microphone and a phantom power source. You could just get a battery source like a Crown PH-IA. You see them on Ebay or an inexpensive mixer will do nicely too.


http://www.trueaudio.com/

http://www.behringer.com/ECM8000/index.cfm?lang=ENG

http://www.crownaudio.com/pdf/mics/103292.pdf

Just examples there is lot's of stuff available just start looking.

Rob:)

GordonW
12-29-2004, 09:29 PM
Yeah, the 802 have output that goes to around 20KHz... but it's kind of like the EV T35 that was mentioned before- it's THERE, it's just that it's DOWN IN LEVEL a bit compared to the stuff between 5 and 10KHz. Once you get to about 10KHz, the 802 starts a "tilt-down" in the curve, and it's down 3 dB or so by the time it gets to 20KHz, if I remember the last time I measured one.

Also, no, I haven't measured the Fostex... so it's entirely possible that we're dealing with "specification inflation" with the '17H. I would be interested in seeing the graph for ANOTHER one... if it's taking off THAT severely above 10KHz, it may indeed be grenaded or defective...

I still say, for level matching and overall extension, that either the 2404 or 2405/077 would be the cat's meow here. With a simple crossover to bring it in at like, 10-12KHz or so, it should do the trick handily. Heck, you could probably just put a 2405 in there, and put like, a .68uf cap and an L-pad on it, and parallel it with the VOTT input... I'd bet it would work.

Oh, and BTW: Oftentimes, supertweeters, even if they don't add that much extra treble energy, ARE QUITE AUDIBLE in their effect. This is, partly, because a system that is linear to higher frequencies, suffers less from group delay in the upper frequencies, between 8 and 20Khz. This can help wavefront integrity- the leading edge of transients are more faithfully reproduced. I've even heard a supertweeter improve the apparent quality of BASS and MIDBASS- it's all about the timing of the leading edges of those wavefronts, even those with very low frequency fundamentals...

Regards,
Gordon.

sfogg
12-30-2004, 08:34 AM
". but it's kind of like the EV T35 that was mentioned before- it's THERE, it's just that it's DOWN IN LEVEL a bit compared to the stuff between 5 and 10KHz."

I don't know about the 802 but my 902s have more top end then the Klipsch K77 (EV T35).

This is a K77

http://forums.klipsch.com/idealbb/files/t35alk.JPG

My 902...

http://forums.klipsch.com/idealbb/files/902-8b.JPG

Shawn

GordonW
12-30-2004, 09:38 AM
That K77 very likely needs regaussing. No reason it should be THAT far down at 20KHz! Couple of dB, yeah... but 15 dB down? Something's wrong...

Regards,
Gordon.

Steve Schell
12-30-2004, 02:01 PM
Going after those highest frequencies is a real challenge. I built some field coil ring radiator tweeters a while back and got a feel for what is involved. I couldn't get the moving mass much below 200 milligrams, and that starts looking like a brick to the motor above 10kHz. Although the sensitivity was up around 110dB 1W1M, a downsloping power response above 6kHz. resulted in a disappointing curve. The sound was very clean and sweet, just a bit dull for a tweeter. The first breakup response peak was out around 35kHz, possibly annoying to the neighborhood bats.

It is not too surprising that the 802 might out-tweet the T-35, especially in an on axis measurement. If the 802 is on something like an 811 or 511 horn, the high frequency beaming will bring the highs way up on axis. Also, the tangential suspension of the 802 will have a real dance party above 10kHz., with the resonances adding to the response. The phenolic dome of the T-35 is pretty well behaved and is probably past the mass break point by 10kHz. The important thing is the quality of the sound; which makes a cymbal or audience clapping sound most real? So many drivers today achieve response up high with break up modes, creating that hissing-tweeter sound. A downsloping response can be equalized, but breakup modes are there for keeps.

rloggie
12-30-2004, 10:14 PM
Rob,

My test equiptment consists of a db meter and a multi meter. Thanks for the recommendation. I would like to pursure a pc based tester as I keep a laptop in the listening room next to my chair to catch emails and visit this forum. I've sold the magnificents in favor of trying a pair of Olympus SR8's. The highs are there. The bass is there. Yet being able to quantify what I'm hearing and tuning the room is very appealling.
I tried downloading the free program from trueRTA, but was unsuccessful in getting it to run on my (xp home) OS. Just an inital try though, and I'll take some time tomorrow to get it going. Thanks again for the direction, it's just what I wanted.
Robin

Hello rloggie

You have any test equipment?? I use an RTA to set things up and balance out the drivers in my speakers. You could purchase something like a Behringer 8024 or go the PC route with software. Either way will work well and give you the tools you need to take some basic measurements that won't cost you an arm and a leg. I will post a link for software. If you go that route you need a measurement microphone and a phantom power source. You could just get a battery source like a Crown PH-IA. You see them on Ebay or an inexpensive mixer will do nicely too.


http://www.trueaudio.com/

http://www.behringer.com/ECM8000/index.cfm?lang=ENG

http://www.crownaudio.com/pdf/mics/103292.pdf

Just examples there is lot's of stuff available just start looking.

Rob:)