New Heathkit AS101 owner - First post.

[alancohen]

I also have these:






Similar to University HF-206s?

Worth a try before dropping the cash?

[Earl K]

Alan,

(A) I just reread this thread . A couple of things stick out .

(i) It seems you have a DCX2496 available for biamping .

(ii) It also seems you have available another amp that you can commit to the HF circuit if you actually do biamp .

(iii) Your AS-101 have 8 ohm components loaded into them .

(B) Upon review ( for you to get more HF ) I would simply biamp these 101(s), using your available electronics ( & not buy any new drivers or diaphragms ) .

(i) Build up the HF portion of the midrange suppression circuit ( that I posted above ) , put it inline with the horn-driver , turn up the HF amp to make up for the lost sensitivity and then take a listen .

(ii) The new balance ( between mids & HF ) should be more to your liking .

(iii) This is cheaper & faster to do when compared to trying to integrate a tweeter ( & should sound better ).



PS ; Forget about those Ovation horn drivers ( they'll be dying by 8K for sure ) .

AS-101 Schematic

[alancohen]

That makes perfect sense, Earl, but it might not be a good option in my case. The amp(s) I plan on driving my HFs is a pair of 1W 300B OTL monoblocks. At 1W I need as much of the efficiency that a HF CD can afford. If I'm toning down the mids almost 14dB then I think I'm shooting myself in the foot.

FWIW, once I build the 300Bs I will have 3 amps available for tri-amping. That would allow me to boost the above 14KHz range through a tweeter without muting the 800-14Khz mids through the 811.

But that might defeat the gloriousness of the 300Bs by chopping them off at 14Khz and not allowing them to reach higher. And I'm not building 4 300Bs!!

I think the 802-8Gs might be the answer. It will allow the 300Bs to play all the way up, I won't be disturbing the imaging by adding another component and I'll be able to maintain the high efficiency Altec horns are known for.

[voice of the theater]

I think the 802-8Gs might be the answer. It will allow the 300Bs to play all the way up, I won't be disturbing the imaging by adding another component and I'll be able to maintain the high efficiency Altec horns are known for.

I think you hit the nail on the head here. Not to mention, your rationale is very much in keeping with Altec's philosophy regarding the 802-8g/tangerine phase plug....

[Earl K]

That makes perfect sense, Earl, but it might not be a good option in my case. The amp(s) I plan on driving my HFs is a pair of 1W 300B OTL monoblocks. At 1W I need as much of the efficiency that a HF CD can afford. If I'm toning down the mids almost 14dB then I think I'm shooting myself in the foot.

FWIW, once I build the 300Bs I will have 3 amps available for tri-amping. That would allow me to boost the above 14KHz range through a tweeter without muting the 800-14Khz mids through the 811.

But that might defeat the gloriousness of the 300Bs by chopping them off at 14Khz and not allowing them to reach higher. And I'm not building 4 300Bs!!

I think the 802-8Gs might be the answer. It will allow the 300Bs to play all the way up, I won't be disturbing the imaging by adding another component and I'll be able to maintain the high efficiency Altec horns are known for.

A couple of things to make note of ( before you pull the trigger on any new drivers or tweeters ) .

(i) You're repeating verbatim ( as if it's somehow gospel , info that can't be substantiated ) that your current drivers are somewhat flat out to 14K .
- I can assure you they are not flat out to 14K / ( almost 15db down at 14K compared to 1K, is not my definition of the word "flat" ) .
- I guess the message contained within this Zilch graph ( that I posted earlier ) simply didn't register with anyone here .
- The existing curve ( on your 811/806 combo ) won't be that much different from the following red trace .
- If you want to use tweeters, you'll want to cross-over in the 6-8K region ( if you go with a raw 811/806 response ) .
- Here's that graph again ;



(ii) If you do get some 802-8G drivers, you'll need to tone down the mids 10 or 11 db to be somewhat flat out to 14K ( according to some testing that I just did with a 802-8T loaded with a 34647 diaphragm / I'll post pics sometime later today ) . The 806 requires even more midrange attenuation .

(iii) I'd suggest you get some measurement gear before buying anything like other drivers or tweeters.

- FWIW, REW is still free & it works well on a Mac ( under some strict conditions that dictate what sort of external soundcard you can use ).

- Also, a USB based test-mic is in the works ( from the MiniDSP people ) which will come with a unique calibration file ( for each & every device sold ) making the mic useful for measurement purposes. It'll be @ $100.00 ( from what I've read ) making the entry cost for getting serious data, cheap as Borscht !

[alancohen]

That is certainly a sober recommendation, Earl.

I have a USB-based Samson Go Mic. It might do the job well enough. I also have a Macbook Air. I downloaded REW, but I don't have the patience at the moment to set it up or figure out how to use it. Can these programs play a pink noise signal through the headphone output and record it back though the USB mic?

[Earl K]

<<<<<<<snip>>>>>>>
Can these programs play a pink noise signal through the headphone output and record it back though the USB mic?

Yes ! ( REW has a great signal generator built into it )

[Alien_Shore]

I did some horn compares that you might find interesting:

Here is a modern HF driver (B&C DE250) on three different Altec horns:


And here is the same driver compared to an Altec 802D on an Altec 511B horn:


All of these are "barefoot" driver measurements (no XO, EQ, etc.)

I also have some 902 and 802-8G graphs here somewhere....

[Altec Best]

Mic should be a little closer IMHO also pointed at the speaker and roughly in the center of the High frequency driver and the woofer.This photo your Mic is pointed at the ceiling. You should be using a Mic stand as well.

Take a look.

http://www.troelsgravesen.dk/measurements.htm

Place mic like this pointing with the stand parallel to the Mic

http://www.bksv.com/doc/BO0102.pdf

You may want to try and remove any reflections as well,like floor bounce.

http://www.synaudcon.com/site/author...-equalization/

And some basic stuff on Wikipedia.

http://en.wikipedia.org/wiki/Loudspeaker_measurement

It's not easy to measure loudspeakers in a room with lots of furniture,etc... due to all the reflections it may produce. Measuring outside isn't always practical but does help quite a bit.

This is the stand I bought for my setup.. Not too expensive.Also bought a 25' cord for the Mic.

http://www.parts-express.com/pe/show...number=242-743

[Altec Best]

FWIW do you have your sweeps set to 20 Hz - 20Khz ? If your starting you sweeps higher say 500 Hz and up it won't show much bass in your response curves. Like the ones you posted here Alan..

Even if they are tired (416's) you should still see some kind of bass response..More than your seeing.