The 311's are large format.You would need the 21216 adapter to use the 802.IMO you aren't doing the 311's justice with a small format driver on those big horns.They need 288's,299's,etc....
Not OT at all. The 311s are highly prized - you got an obscene deal.
Especially the 311-90's They sell for $1200 a pair or more all day long !
I am in the lower mainland. I have Altec stuff but it can only be listened to when the weather is nice as I have them stored right now.
I have 210 cabinets (A4) but not Altec drivers
825 cabinets (A7) but not Altec drivers
811 and 511 horns but not Altec drivers
1803B horns with 288 drivers
1233 speakers (sort of pro version of the Valencia with 421 woofers and 808 tweeters)
604 8H drivers in custom boxes.
A7's can be a bit wieldy for home use, I think the model 19 is one of the better indoor units but the Valencia can hold it's own.
Cal and you are an Altec fan with no Altec Drivers !!
I know you have some lurking there somewhere ! And they are !
Hey Cal how goes it ?
I have read somewhere...that the horn typically has ~10% of the distortion compared to a dome.
Arne K
A compression driver/horn will generally have less distortion at a given level than a dome tweeter, though at low levels it probably would not be difficult to find examples of dome tweeters with slightly less THD than a compression driver/horn.
Horns are generally used in hifi for a desired dispersion pattern, high sensitivity and SPL capability, a 1" dome tweeter will burn up at a far lower level than a real trombone, trumpet , cymbal etc., while a compression driver/horn can reproduce that level using about 1/10th the power.
811-511
Both have their fine points. I rather like the 811 crossed around 1200 Hz... that said the 511 can be crossed down around 750 Hz.
The 511 might not sound quite as good as the 811... but at 750 Hz it's easier to match up with a 16" woofer (mid-woofer).
Given the physical size of the typical woofer used with these things, it's difficult to get a 416 or TAD 1601 close enough to the horn for a 1200 Hz crossover freq.
How low will they go..... call it 50 - 55 Hz..... but in the end you may just not care.
Cyclotronguy
Both have their fine points. I rather like the 811 crossed around 1200 Hz... that said the 511 can be crossed down around 750 Hz.
The 511 might not sound quite as good as the 811... but at 750 Hz it's easier to match up with a 16" woofer (mid-woofer).
Given the physical size of the typical woofer used with these things, it's difficult to get a 416 or TAD 1601 close enough to the horn for a 1200 Hz crossover freq.
How low will they go..... call it 50 - 55 Hz..... but in the end you may just not care.
Cyclotronguy
Look at the graph in post #44, the stock tuning appears to be above 100 Hz, Tom Danley retuned the box around 50 Fb, getting an octave LF extension.
The higher Fs (and sensitivity) 421A would have more "bass" in the stock A7 box than the 416, to get LF extension with either type of speaker requires a lower Fb.
There certainly is plenty of room in the A7 for large ducts to tune low.
Art, no need for me to doubt your listening experience. Since I have yet to hear a recent example of the Danley designed horns, I can't comment on how they might sound.
The early Unity horns seemed if I remember correctly to have a rather abrupt transition from the outlet of the compression driver to the 4 walled conic section. An invitation for diffraction, and a pressure discontinuity... I have no way to know what the present transition on Tom's newest Synergy horns looks like today.
Also the angle of out from the driver's throat plays a role in what the expansion can look like. That angle is important. Some of the newer drivers with neodymium magnets manage a very short section inside the driver, permitting more rapid expansions outward, getting better HF dispersion. This is more or less independent of the type of expansion, since at the outset almost every horn except for the newest Geddes waveguides and other similar designs look very much like conic sections.
Wrt to the LP "filter" at the output of the mids, due to the entry hole, fine, but this is not the issue. It may well be that Tom has worked this into his design and has eliminated the problem, but the air between the entry holes of the mids and the throat of the compression driver is certainly pressurized at mid frequencies! Unless there is a HP acoustic filter at the input to the compression driver the full pressure of the mids would appear to be present on the diaphragm of the compression driver. And this (if this happens) would cause IM in the compression driver.
Anyhow this is a thread on the A7 not the Danley horns...
_-_-bear
Driver response is often shown in a large sealed box or an infinite baffle.
Those responses typically roll off at about 12 dB per octave from some upper point.
When the same speaker is placed in a bass reflex box of the correct size, it will have a generally flat response down to Fb, then will roll off at 24 dB per octave.
Different alignments, that is different box size and tunings, will result in different response curves.
One can choose extension in favor of sensitivity, or more boom with less bottom.
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