My first horn experiments

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Charles, with 128 it looks like this: setup is both systems, A7 now crossover , horn 6,8uF + 10R parallel and 5.1R series.


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Hi Till

Did I get it right that post #63 is the whole VOT with the HF horn connected via 1st order crosover ?

In this case a measurement length of 128 samples is of course too short. What I wanted to say is that you should try to measure the HF horn alone (preferably outside, with the better mic preamp) with a measurement length of 128.

The fine peaks and throughs of +- 2.5 dB from the last measurementare look very good for a horn !! What bothers me is the "whole" around 4 kHz. But this could be caused by room acoustics and/or the large measurement window. It is always difficult to distinguish between irregularities of the drivers and such of the room/measurement setup ("Wer misst, misst Mist!").

Have you ever tried to feed the speakers any pink noise and looked at the "real time analyser" that Hobbybox offers ?


Yes, 63 is both speakers and first order. The last one i feed my mic preamp with more voltage and measured 1 meter distance. Horn and mic laying on the floor here, next wall about 2 meters away. My impression is in fact the room i´m working in at the moment is too small for measurements and its not so good with a unknowm mic. For outdoor measurement i need the right day (silent and dry) and time too cary all the equipment ouside. I will investigat if University provides my a better mic for this puposes or so.
Joined 2002
Hi Till,

I don’t know if your TAD’s are new or not but you might want to run them at volume for a few weeks and make your measurements again. I know when I put my 4001’s into service they only had a few hours on them and they sounded a little compressed and lacking in the high end making them sound closed and distant. After a few weeks of listening they seemed to break-in and became much more dynamic and open.

Rodd Yamashita
>The original should look like this (?) says the internet.
This is a 'doctored' early A7 published FR from the Badmaieff/Davis book "HOW TO BUILD SPEAKER ENCLOSURES" that's been smoothed to the point of near uselessness below 1kHz, so I wouldn't use it as a guide to judge your own measurements. Also, I didn't read the whole thread, but unless you're driving them with an OPT with ~4ohms output impedance you won't get much of a match with any early OEM Altec published specs.

Really, if you reverse engineer the 825/828 you'll see that your measurement is quite accurate.

Nice mid horns BTW, very professional. Are you a 'pro' audio and/or woodworker, or just an avid DIYer?

Thank You very much, this posting was very good for my working moral. I´m not professional in Audio or woodworking. I´m student for mechanical engineering at the moment, but had jobs in my life so far in every possible and not so possible kind of business... a lot was related to handcrafting. Because of this i´m, lucky to own a real lot of tools and machines. (to be honest its a kind of illness, i collect every kind of tool)

I´m absolutely not experienced in speaker measurement, so what i measured is no crap, but make sense? thats great!
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