Look at my new babies...Altec 846Bs w/EV Tweeters!

[Zilch]

The filter is compensation, and only minimally mitigates the spike.

It's more like 8-10 dB, actually, though I don't have time to check that now 'cause I'm about to dunk a driver and horn in a tub of water to determine the displaced volume.

[I ain't sayin' WHOSE driver it is, tho.... ]

[VTUBE6]

The filter is compensation, and only minimally mitigates the spike.

It's more like 8-10 dB, actually, though I don't have time to check that now 'cause I'm about to dunk a driver and horn in a tub of water to determine the displaced volume.

[I ain't sayin' WHOSE driver it is, tho.... ]

Making somebody's day, eh.....

[Zilch]

Horn and driver (front mounted) displaced 10 cups = 2.5 qt. x 57.75 cuin./qt. = 144.375 cuin. = 0.0833 cuft.

I was kinda far off on that one.

Using Moldy's T/S parameters (which BB6P liked) and VTUBE6's port dimensions, the stock tuning virtually superimposes with BB6P's suggested optimal for that driver in that size box.

Gross volume is 5.469 cuft., 5.288 cuft. net, tuned to 35.8 Hz.

An apparent EBS (Extended Bass Shelf) tuning. I leave it to the box-tuning experts to opine as to how good or bad it is.

It'd be good if someone confirmed this result in a different box modeling program.

Edit: For potential discussion, some driver substitutions, bottom: 2225H, green, BB6P retuned, violet. 2235H, cyan, BB6P retuned, blue.

[moldyoldy]

Horn and driver (front mounted) displaced 10 cups = 2.5 qt. x 57.75 cuin./qt. = 144.375 cuin. = 0.0833 cuft.

...It'd be good if someone confirmed this result in a different box modeling program.

In an old Altec forum thread,, on a query of optimum use of his 416-8A/511s, GM ran that dog to the ground, scratched its' belly, and made it drool.. A classic (copied) post by a classic dude;

"A T/S max flat alignment with an SS amp is 6.65ft^3 net/37.5Hz Fb. Pushing it to ~7.25ft^3 net (~8ft^3 gross) at this Fb or a little lower looks good also. If this size was chosen and driven with various amps of differing output resistance, then to keep it from sounding boomy will require tuning lower to suit each one.

If we assume a worst case scenario of 4ohms, then the T/S max flat alignment cab size goes ballistic to 25.95ft^3 net/24.9Hz Fb! Shrunk to 7.25ft^3 net requires you to seal it up since you can't tune it low enough to get rid of the underdamped response.

Obviously, any series resistance value in between requires a longer vent to tune it lower with increasing resistance, so I suggest mounting the vent tube on a separate little baffle that can be removed and resealed so you can insert different lengths. Even small leaks, like around a screw, destroys cab tuning so be forewarned.

Anyway, I tend to like my horns above my head angled down, with the 15" at ~face height since a 15" is beaming in the 500Hz XO BW and accept the floor bounce issue, while some prefer the horns at face level, or a little below, with the driver close to the floor to reduce floor bounce and get some LF/midbass boost.

That said, assuming the specs I'm using are relatively close, driven with an SS amp the driver wants to 'feel' a rather squat cab, with a 22"id height, requiring the other dims to be 31.5"id/19.95"id. As series resistance increases, so does height. The worst case scenario bumps it up to 34.66"id tall, so I compromised on an acoustic ratio cab with two dims close to these and averaged cab tuning WRT driver/vent placement since this is a *****hoot anyway:

35.75"id h
15.5"id d
24.88"id w
driver 16.5" down from top
vent 6"dia. x 1.25"L (for SS driven) 6" up from bottom

Line one wall, top, and back with fiberglass or equal to damp lower mids, and I assume you know how to make a rigid cab/mass load the driver.

If you prefer more floor gain/HF horn lower, then of course you can lay it down with the horn relocated.

Cab Vb was chosen by factories based on the driver's Fs/Cms/BL product (very similar to T/S) and tuned by damping the in-box impedance peak."



GM was also the source of the T-S data.

Not much of any reason left to hunt that dog.

Just so you don't have to dunk anymore doughnuts;

[Zilch]

Thanks, Moldy. Maximally flat ain't very with this driver, looks like. Even with variable cabinet size, BB6P's suggested "High Fidelity" tuning is pretty close to Valencia stock. "Extended Bass," it jumps to 12 cuft. and isn't much flatter.... :dont-know

Honestly, that may be the best we get with this model.

That's certainly what it's looking like; it'd take swapping out the driver to improve it. I've never heard one, so I can't speculate as to whether something that radical would be warranted.

[VTUBE6]

In an old Altec forum thread,, on a query of optimum use of his 416-8A/511s, GM ran that dog to the ground, scratched its' belly, and made it drool.. A classic (copied) post by a classic dude;




GM was also the source of the T-S data.

Not much of any reason left to hunt that dog.

Just so you don't have to dunk anymore doughnuts;

Moldy, lots of great info here. When it's all said and done, I'm not willing to mess with the baffle in order to get maybe a couple of Hz lower, if that. I think with your and Zilch's info (and I really thank you both for your time and brains!) I think Zilch probably has it right; change the driver. I'll wait a bit on that since I want to take in room measurements with the new BMS HF driver. On a side note, was going to do a quick change on the x caps (21uF, 8uF only), but may wait till Zilch gets back to this xover and after the 1st annual speaker shoot out. BTW, is that on for this weekend?

[Robh3606]

I think Zilch probably has it right; change the driver. I'll wait a bit on that since I want to take in room measurements with the new BMS HF driver.

So what are you going to call your speakers when you replace the other driver??

Rob

[VTUBE6]

So what are you going to call your speakers when you replace the other driver??

Rob

If I change them: the Valencia "Special Eds."

[louped garouv]

Anyway, I tend to like my horns above my head angled down, with the 15" at ~face height since a 15" is beaming in the 500Hz XO BW and accept the floor bounce issue, while some prefer the horns at face level, or a little below, with the driver close to the floor to reduce floor bounce and get some LF/midbass boost.

I also tend to like the 15"s at ~face height, with the horn above the head angled slightly downward as well....

but i am normally standing when listening....

FWIW
I've also read several altec guys state that of the 515 series woofs, the 515B seems to be able to go a bit higher than the other family series designations....

[VTUBE6]

Horn and driver (front mounted) displaced 10 cups = 2.5 qt. x 57.75 cuin./qt. = 144.375 cuin. = 0.0833 cuft.

I was kinda far off on that one.

Using Moldy's T/S parameters (which BB6P liked) and VTUBE6's port dimensions, the stock tuning virtually superimposes with BB6P's suggested optimal for that driver in that size box.

Gross volume is 5.469 cuft., 5.288 cuft. net, tuned to 35.8 Hz.

An apparent EBS (Extended Bass Shelf) tuning. I leave it to the box-tuning experts to opine as to how good or bad it is.

It'd be good if someone confirmed this result in a different box modeling program.

Edit: For potential discussion, some driver substitutions, bottom: 2225H, green, BB6P retuned, violet. 2235H, cyan, BB6P retuned, blue.

Honestly, that may be the best we get with this model. Designers may have figured it was fine for the amps of the era. Maybe the same rationale as the UHF. I think I can increase cabinet volume with more attention placed to acoustic material placement. A thicker gauge hook-up wire may help too. That fishing line thick wire is pretty thin for a bass driver.