Thanks Altec Best. It has a black surround. I wonder why they would put a 16 ohm speaker in my A7's?Originally Posted by Altec Best
Thanks Altec Best. It has a black surround. I wonder why they would put a 16 ohm speaker in my A7's?
I had changed my post ,you must have quoted me before I could change it.The 803B was a hammertone green and not the flat green of your 416.So I was correcting my post when you quoted me.
For your question they wouldn't if it's an 8 ohm speaker.IME someone must have thrown a replacement in it not knowing to keep them all 8 ohm.It wouldn't have come that way from the factory unless, it a dual woofer con-fig cabinet, speakers wired in parallel to acheive an 8 ohm load.For your A7, who knows ? I would assume that it was just a replacement, albeit the wrong replacement.
Both woofers are the same. These were bought brand new. Next weekend, I will verify exactly what crossover, horn and driver is also in these. Curious, That must be why I was abe to crank up the DC300A so high. What's it going to sound like when I hook these up in parallel with the 8 ohm Peavey T300s. I also wounder how I wire up the 8-8ohm Piezos.
Last edited by VolvoHeretic; August 7th, 2011 at 02:00 PM.
I'm still working with the sealed box, but may try to go ported soon. And hope the port will boost the bass response some. As it is, I have a pretty big shelf that drops under about 140Hz. I can make up for it in my crossover (active or passive) but it would be nice to make up for it acoustically. I suppose a combo of sealed box, baffle step and horn loaded woofer conspire to create the shelf. With proper crossover EQ, it all sums well and sounds good, but takes a bit of power.
The main problem I'm having now is a lot of energy around 220Hz, or a few notes below middle C. Can't see it on the frequency response chart , but sure can hear it. And it shows up pretty as you please on waterfall and sonograph charts. "Ringing" right around there. I tried Dominique's curtain trick by putting a big, fluffy pillow hanging down below the woofer. It had some effect, mostly smearing the ringing or reducing its Q. That makes it a little bit less noticeable. Once I figure out where the ringing is coming from and fix it, I'll be super happy. The system should then be super clean.
Again, this is the horn 'ringing'. It's a half size ~55 Hz expo, so a ~110 Hz 1/4 WL F0 and since a horn must be a 1/2 WL long before it gets up 'on the pipe' [to use 2 stroke tuning jargon], this means ~220 Hz; but with too small a mouth this sends huge initial reflections back to the throat, so either the mouth must be larger [wings] and or some damping around its mouth perimeter and/or adding an acoustic band stop filter and/or pre-loading the driver more by tuning the cab much higher. IIRC both baffle boards have to be off, making it a crude ~80 Hz BLH, then an acoustic screen is required to critically damp it/attenuate unwanted harmonics off the back of the driver. The latter of course severely rolls off its bass output.
Another option that might help, though never tried it on an 825/828 is to tightly cover the rear of the driver with damping material, experimenting with increasing thickness to find the best compromise. The key here is ?tightly? since what you want it to do is acoustically lower Qms/Qts, i.e. make it more suitable as a horn driver like the cab was originally designed around.
Anyway, good luck with it, I've got to get back to trying to salvage as much molding, siding as I can since pricing has gone ballistic since the housing construction slowdown. My 34 yr. inflation adjusted materials budget has proven woefully short of reality.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Thanks GM, I'll experiment with wings. I tried a pillow in the gap between the top of the bass horn and the bottom of the 1005 horn - all that did was give me more junk below 200Hz. It's easy to see the results in the measurement. Real wings on the sides should be a different story.
Good luck with the house stuff!
With that big mid range horn you really need to splurge and just build the big mid bass horn.
That will be the only way to make that big altec mid range horn happy.
Two altec 515s and a mouth bigger than Rosie O'Donnell's.
But isn't those 1505's too big for a room that narrow ? Even with the treatments IME there would be a tremendous amount of room reflections due to the narrow aspect of this room ? The treatments would have to be 360 degrees meaning all 4 surfaces walls,ceiling,and floor to even come close in damping the reflections ? IMHO I think a 311-60 would be perfect for that room. Dunno whadda ya think guys ?
Horns IMO are all about mating them to the correct application.
What a thread!!! some real knowledge here....
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