Altec A7 from 800hz to 500hz

invalidbuffa

invalidbuffa

Super Member
My A7's are currently configured with a 416A woofer, 802C CD, 811B horn, and N800D crossover. I'd like to try the speakers crossed over at 500hz and am picking up a set of 511B's today. What is my best crossover option? I was thinking about cloning an N500G and modifying if with an HF l-pad, but wanted to see if there were any better options.
 
Hiraga's crossover, as shown in Sound Practices, was for the A5 and if so it might not directly transfer properly to A7 drivers.

Were I the OP I'd use an electronic crossover with EQ and bi-amp. If not that I'd clone whichever 500hz passive crossover Altec used with his drivers and add the Altec compensation EQ circuit to extend the highs. Or build a simple second order crossover to the nominal impedence of the drivers, as Altec often did, and add the compensation circuit.
 
Thanks, that's definitely a step in the right direction. His crossover design appears to implement a notch(?) filter designed to compliment the 288 HF driver. Will I want to modify/remove the circuit for use with the 802?

For now I'd like to stick with a passive XO. I actually have really good results using the A7's with the audyssey EQ on my receiver
 
Last edited:
Any time you lower the crossover freq of any Altec driver diaphragm combination you are increasing displacement of the diaphragm in the gap to such an extent it will fail physically before the coil fails due to over heating. The 802 with the original diaphragm power handling will drop from from over 30 watts to below 15 watts rms continuous. Changing the slope from second or der to 4th order will only help marginally. If you just swap horns you will be matching the Q or the LF box with the 500 hz horn giving a much smoother transfer from the horn of the woofer to the HF horn making off axis reproduction m ore uniform at 800 Hz. I don't like the sound of the 511 horn below 1000 Hz, but thaT'S ME. I much prefer 3 way systems. with the mid covering fron below 300 to above 3000 hz. I do find 604E very pleasant.
 
I have an altec 1203's 811 horn and an 807 driver with a 825 hz XO but I have a 421 woofer. I also have a 511 lying around with a cabinet I will be prepping to take either horn with a front baffle swap out.

Anyway, I was thinking of going the other way, crossing over as high as 2k if it sounded better. Of course the 421 works well to even 2400 - its rated 102 db/watt 600-2400 hz.

I think the horn will work fine lower, there have been 500 hz XO's in some VOTT series - but the trade off is that the horn starts to trail off by 12k, in fact it starts to really give up after 16k. I'm going to experiment with an active XO and when I find where it works best, I'll try to see what horn driver I can use (B&C or other) that will give me a good outcome from that XO to 20k.

So the question is - why you want to get the XO lower ?

Cool.
Srinath.
 
I remember Zilch concluding that the 511 was really an 800 or 1kHz horn, and the 811 a 1200 Hz horn. If I could remember where, I'd post a link to it. It might not have been on this forum. I use my 811s active at around 1200.
 
Many Altecistas think crossing at 500 gives a little extra clarity and incisiveness to the sound compared to crossing at 800. It's well worth playing around with.
 
I built some Z19 crossovers (1200hz) too use with the A7 / 511b horns. Thought they sounded great.
Now have 805b & using a Altec processor crossing around 500hz with 24db slope.
Sounds awesome!
 
Costs you in the highs

Tom Brennan said:
Many Altecistas think crossing at 500 gives a little extra clarity and incisiveness to the sound compared to crossing at 800. It's well worth playing around with.
Click to expand...

That is pretty true, and the horn is higher spl than any of the woofers they were coupled with. so not only will it be cleaner, it will also be ouder. The trade off though is the high freq and the limitation isn't the horn, its the horn driver.
Anyway I am yet to even get it fully functional, so I have no first hand info.

Cool.
Srinath.
 
It's mostly about the beamwidth of the mid-bass horns(816, 817, 825, 828). All of them are already below 90 degrees in the horizontal by the time you get up to 500hz. The higher you push the XO, the more the midbass begins to beam, and roll off as you step out of the sweet spot.

The 511 and 811 acoustically "unload" when approaching the lower end of their claimed usable BW. This creates 2 problems, the first is over excursion of the diaphragm, and the second is that the acoustic center of the horn/driver moves as you approach cutoff at 500hz making truly clean phase alignment impossible.

These are probably fairly moot issues for home/hifi applications. But, for SR apps and high level monitoring/critical listening it creates an unacceptable haze over the system, IMO.
 
Last edited:
Thanks for the input everyone. I did come across some of Zilch's test plots with the 511B which confirms it's better suited above 800Hz. Looks like I'll continue using the 800Hx XO until I (hopefully someday) grab a set of 803B horns and 288 drivers.

Has anyone here tried the tangerine phase plug?
 
Last edited:
invalidbuffa said:
I did come across some of Zilch's test plots with the 511B which confirms it's better suited above 800Hz. Looks like I'll continue using the 800Hx XO until I (hopefully someday) grab a set of 803B horns and 288 drivers.
Click to expand...

I wouldn't let another's notions stop me from trying something lots of people did (including the manufacturer) and were quite pleased with.
 
Tom Brennan said:
I wouldn't let another's notions stop me from trying something lots of people did (including the manufacturer) and were quite pleased with.
Click to expand...

Yeah, try higher and lower Xover points and see what YOU like. I would recommend going with an active Xover and 4 amps at a minimum. Makes adjusting your crossover points way easier and sounds better.
 
It's the one thing I really like about the Altec 1285-8A,B crossover.. It easily changes between 500,800,and 1200 Hz crossover points making these comparisons quite easily..

The N500G is a 16 ohm 80 watt max crossover.
 
twiiii said:
Any time you lower the crossover freq of any Altec driver diaphragm combination you are increasing displacement of the diaphragm in the gap to such an extent it will fail physically before the coil fails due to over heating. The 802 with the original diaphragm power handling will drop from from over 30 watts to below 15 watts rms continuous. Changing the slope from second or der to 4th order will only help marginally. If you just swap horns you will be matching the Q or the LF box with the 500 hz horn giving a much smoother transfer from the horn of the woofer to the HF horn making off axis reproduction m ore uniform at 800 Hz. I don't like the sound of the 511 horn below 1000 Hz, but thaT'S ME. I much prefer 3 way systems. with the mid covering fron below 300 to above 3000 hz. I do find 604E very pleasant.
Click to expand...

I tend to be in this camp. Even just changing the horn, you should improve the midrange quality of the system, by making the dispersion more uniform, and by improving the LF response of the horn itself.

I'd be inclined to try just changing the horn to the 511, with the original crossover, first. Listen to that combo first- you may find you don't want to go further. But, if you do, then changing the crossover is a pretty easy next step...

Regards,
Gordon.
 
You must log in or register to reply here.

Similar threads

G
Altec A7 crossover recomendations
Replies
7
Views
211
twiiii
twiiii
Dukiedook
Taking A7 mountain by strategy
2
Replies
26
Views
2K
Dukiedook
Dukiedook
Aptone
My first horns: Altec A7
2 3
Replies
57
Views
3K
Tom Brennan
Tom Brennan
gogofast
Question: active bi-amping Altec 414a & 804a.
2 3
Replies
50
Views
7K
Zilch
Zilch
SgtBilko
Looking for some Altec A7 VOTT speaker system suggestions
Replies
12
Views
2K
rooferben
rooferben
Back
Top Bottom