Adding Super Tweeters to 604s?

[lhgin]

Hi guys,

I've once read in this forum that the 604's HF attennuates after 15kHz to -10dB at 20kHz. I'm thinking of adding a super tweeter to it on to of the cabinet to enhance the HF response for my system.

Could you please recommend me a HF driver and the crossover network/point? Have you tried adding one before and how's the results?

Many thanks in advance!

Rgds,
lhgin

[AL-TEC]

Hi ihgin.

I really do not feel that the Altec models of 604's starting with the ones that used the 802 series HF driver coaxially mounted with the "all aluminum" music diaphrams rolled off that much at 20 hz. We once did a test of the black model 802-8G circa early 70's. It was unprecedented in it's response to above 20 khz! I do not remember the details, but this driver was to be utilyzed for a special application that required great HF response capability to that extreme frequency range!
There is not a WHOLE lot up there above 15 to 17 khz to really hear. There are however, upper instrument harmonics up to 20 khz, plus, or so, to expirience possibly that could make a difference in the HF sound....... if your ears are that good.

I feel in my opinion as an audiophile, and listener/user of Altec 604 series coaxials from many years back, that trying to add a "super-tweeter" to a 604 is totally unnecessary. The 604 C/D/E/K....ect, allready has it's "super-tweeter" in it.

To add an outboard tweeter to a good "point-source" design coaxial with it's "inherit" design attributes might cause a phasing interference problem, or something similar that would de-grade the Altec coaxial.

The latest models of 604's such as the 8K models and newer with the "Manteray" HF horns utilyzed had unbelievable clear detailed highs! All you have to do is listen to one, and you could tell right away that an additional tweeter of any kind would not help anything.

AL-TEC

[Todd W. White]

I totally agree with the above post - adding a super tweeter to the 604 is a waste of time and money.

If you are not getting the high's you think you should, try checking other areas in your system - unless your 604's or their crossovers have something wrong with them, THEY are not the problem.

Todd W. White, Owner & Webmaster

Altec Lansing's (unofficial) Homepage

[lhgin]

Hi guys,

I got to know about the attenuation on HF from Don on the post in this forum, as follow:

http://www.hostboard.com/cgi-bin/ult...=3729&t=35&p=2

As my upgradigitis itched, therefore, I thought of adding a supertweeter to spice up the HF as I'm not sure myself whether am I getting enough HF or not.

Thanks for the informative responses!

Rgds,
lhgin

[Don McR]

To AL-TEC

The 802-8G measures out to 20khz because that was the first Altec compression driver to use the Tangerine phase plug. Altec states quite plainly that the reason they developed the radial phase plug was to increase high frequency bandwidth.

If you look at Altec's own measurements for pre-tangerine drivers, you will see that response drops rapidly after 10k. With specific regard to the 604, there is a 1971 604-8E response curve at the following link that shows this very clearly.

604-8E Frequency Response

[David Deratany]

AL-TEC,

Where you said: "The 604 C/D/E/K....ect, allready has it's "super-tweeter" in it", is there a reason the "B" is not included, or was that just an oversight?

[AL-TEC]

Reply to dderat, and Don Mcr:
No I really did not leave out the 604B as an oversite. I was mentioning the Altec 604's that were an improvement over this early original 604, in that it had a lower crossover frequency, and somewhat different little multi-cell horn, and the brochures plainly state that the 604B's freq response was "30 t0 16,000 cycles". Where the improved versions of this Duplex starting with the 604C stated an overall wider freq resonse of "30 to 22,000 cycles". The HF dispersion pattern of the older model 604B was: 60 X 40 degrees. The HF dispersion pattern for the 604C and newer was usually stated as 40 X 90 degrees. Of course I know there were no tolerances given for any of these specs, and can be argued as to correctness. The older 604B however is a favorite among some collectors, but many of these models were updated through the years to be almost a 604E with improved bass cone, and networks ect.......
The main premise of the question was whether a "super tweeter" is needed with a 604. I still say .......NO.

[joyspring]

To all:

I'll have to agree with Don R on this one.

Yes, older Altec literature states "20-22000cps" frequency response yet, as I mentioned in another thread, these optimistic specs do not have a qualifier or limit (i.e. - +/-3dB, etc.). Without that addition to the spec, Altec could make the 20-20k claim.

I've certainly measured 22000hz output on older Alnico 604s yet it was >20dB below their relative output at 8khz on-axis...

The Tangerine phase plug does significantly increase output above 15Khz all the way out to 20Khz but I've noticed that the >15Khz output is never consistent between drivers.

It must be understood that even 15Khz is truly beyond the abilities of a 1" throat, >2" diaphragm compression driver. In fact, constant impedance tube (plane wave) measurements show a -6dB/octave decrease in output above 6Khz; flat on-axis response is obtained from the increasing directivity index of common horns (and why constant-directivity horns need the +6dB/octave equalization).

Now back to the question: should one add a `supertweeter' to a 604-based system? Now that's a matter of personal preference.

Adding one would certainly assure response to 20Khz.

But considering that the 604's greatest attribute is accurate stereophonic imagging due to its coaxial design, adding the supertweeter would probably degrade that attribute depending on the crossover frequency chosen.

Some commercial monitors in the 1970s added a supertweeter to 604E-based systems. Whether that helped the engineers/producers create better product is another consideration altogether.

That said, my preference would be to leave the supertweeter out and live with the limited output above 15Khz.

BobR

PS - Sorry for the long quote but just one more issue: if many in the `retro-' audiophile movement (LPs, analog magnetic tape) and modern high-sample-rate/high-bit-depth advocates malign 44.1K/16-bit digital audio on the basis of limited output above the Nyquist (22Khz), what are they doing listening on loudspeakers that have very limited output at those frequencies in the first place?

[AL-TEC]

BobR:
If listening to LP Vynil records, and tape, whether reel to reel, or high quality cassette decks:..... It is up to the listener/audiophile's preferences as to the music they like to hear! CD's are the best. If the music is CLEAR, and selections that the listener wants to hear, then don't be so "persnickety"....! If you uytilyze an equalizer , then the "highs" that you say are not there ......really are there with ALL ALTEC HF drivers ....Coaxes, or individual HF drivers.!

AL-TEC

[Jim D]

While it is true that mathematical formulas show all small format drivers rolling off over 6K, the tangerine phase plug of the later ALTEC's actually doe not match this model as it holds up pretty flat to about 10K. After that it does roll off, near the mathematical rate. In a real sense this is an increase in usable high frequency, not intangible HF up at 20K. What is up there anyway, mostly distortion. How many people really can hear beyond 15K? If you have 20k response, beware of annoyed nasty neighborhood dogs, and very annoyed quite local female humans (who usually hear much better than us males). Anyway, the small and large format ALTEC drivers, especially the tangerine models are equal or better than all of their competitors. I side with the people who say do not add a supertweeter. Jim