515B cabinet

[Old Guy]

GM to the rescue- again.

[MERDY]

i have been using the split 210 for a while , i dont know how to post a pic here??
with the 515b it just is in another league , i prefer it to the a7 cab and 816 which really cannot fit and i had to modify the back , i also tried them in br cabs and did not enjoy it
using the 210 i also got the drivers aligned, having them in the horiziontal position with horn on top also helped a lot in crossover implemation,i use a electronic crossover as well as horn subs
they are perfect in the home if you have space ,sometimes it just reminds me that i am in a small club and the platform stage is the size of the speaker layout
all altec members are wellcome for a visit

[jnorv]

Well said. I have been chasing the ultimate LF horn for years. I am willing to dedicate my attic for a straigh horn but have yet to put one thru "Horn Response" that I was willing to invest in. It may be time to just start cutting wood. I did pick up a pair of the Lab Sub drivers to use in tapped horns but there is no reason that I cannot just straighten out the Lab in my attic.

Jim N

[GM]

Greets!

A variation of the theoretical ideal 515B horn is ideal for an attic app since the space is large enough for the 'compression' chamber Vb and there's plenty of room to fold it in half and dump it into a large enough mouth to pressurize a good size room up to where the Labs would kick in.

GM

[GM]

Greets, part deux!

The Imperial was designed for a much higher Qts/lower Vas driver, so is ill suited for the 515/416 series without some serious tweaking.

The 210 split suffers from the same parallel wall standing wave and poor mouth termination issues as most of the Altec mid-bass horns, so while they sound pretty good, they're hardly 'ultimate'.

A conical expansion will have the least distortion, but the highest F3 for a given path-length while a hyperbolic the opposite and due to the 515's front vent and specs, a fairly low CR is desirable, so the 825/828's ~1:1 seems the one to use since it's designed for a slightly higher HF cut-off than the 210's 300 Hz XO design point.

WRT to size, using the published specs the 'optimum' horn is a ~2.1 Hz BLH that's nominally flat to its ~290.6 Hz mass corner, but obviously it's not even remotely practical, so I guess it boils down to what you can fit through the narrowest doorway it must pass through.

Assuming a standard American entry way, this would be ~32.5" x 78" o.d.. This yields a ~56.5 Hz mouth cut-off sitting on a rigid floor and perpendicular to it and requiring a somewhat longer than 120" path-length plus CC depth depending on the flare factor to load all the way to Fc. Note that any shape other than round is a compromise and any other than square increases distortion with increasing aspect ratio, so if 'best' really is required, then it won't go low and get through a typical doorway without being built in a number of interlocking segments bolted together.

Problems with a 'best' low Fc alignment is the size/shape of the mouth termination required to keep reflections back to the throat from modulating the driver's response. Others are a too wide an acoustic gap to a typical 500 Hz system for them to sum well at the listening position and the increasing critical listening distance required with decreasing flare factor. Then there's the size/cost of a ~matching efficiency sub system...........

So, all things considered, a relatively narrow BW conical horn is 'best', with which BW depending on the HF XO point and/or how big and/or costly a sub system can be realized.

GM

[selmerdave]

Originally posted by MERDY:
all altec members are wellcome for a visit

<font size="2" face="Verdana, Helvetica, sans-serif">Hi Merdy,

I might be interested in taking you up on that, could you email me or PM whether that's possible and where you are? I'm in Brooklyn. Thanks.

Dave

[GM]

Originally posted by MERDY:
i dont know how to post a pic here??

with the 515b it just is in another league

sometimes it just reminds me that i am in a small club

<font size="2" face="Verdana, Helvetica, sans-serif">Greets!

You will have to open a Photobucket or similar photo sharing account to upload pics to, then post the image link(s) it generates.

I agree, the only other woofer that I've auditioned that can compete with it other than a few vintage ones is one of the TAD drivers, though I imagine the very expensive GOTO units can.

I agree, the 210/515Bs I had gave a live large venue type performance and I enjoyed it for decades, but for a variety of reasons I wound up getting rid of them and to my dismay found that I preferred the more open sound of dual 515Bs in my old large EBS tuned (~20 ft^3/16 Hz) sub cabs. Apparently the mild throat distortion of the 210s finally got on my nerves at some subjective level and why if I ever horn load them again it will be with a large conical one and accept the consequent narrow gain BW.

Frankly though, I've reached the point where I don't see the point unless only flea power is available since dual 515s have >100 dB sens. and close to an ideal polar response for most HIFI apps mounted either vertically or horizontally depending on the desired coverage angle.

GM

[LICORNE]

I found this . It's a good looking speaker box.




...........................

[selmerdave]

I think those are Exemplars? They are supposed to be "good sounding" too.

Dave

[Davidg]

WOW, I had to go and work for a couple days and while I was gone this thread took off!

Thank you all for the info and ideas! Hmmm where to start? I'm actually glad to hear the Imperial cab would be a poor choice, I wasn't looking forward to building those suckers!

GM, thank you for all the info. I understand most of your post A few things are pushing my brain and knowledge to the edge, lol, sounds like the proverbial "best" cab is gonna get really big really fast!

Thanks for the 210 split info. it actually sounds like a very good option as far as size etc. especially with regards to fitting thru a doorway.

What are your thoughts on angled side's as bowtie mentioned? They could be opened up from the approximate 17" width to 30" and still fit thu a doorway, would that help the standing wave issue or horizontal dispersion at all?

Also I'm a little confused about one thing, you mentioned "a relatively narrow BW conical horn is 'best' etc" I always thought the 515B was a fairly wide BW driver for a 15 so wouldn't a narrow BW horn limit it? What kind of freq. spread would be considered narrow and/or wide for that type of driver?

Merdy, I was searching 210 split info. on yahoo and stumbled accross a old post of yours and a pic of your system on another board, very nice! I would love to hear them but I'm in north Idaho so I probably won't get to anytime soon!

wow thank you all again for your help and info. I'm sure I've forgotten something and will have more questions!