Bringing 828 cabs up to snuff...

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Originally Posted by alancohen

Thanks GM.

So if 75"^2 is the goal at .75" deep.........

I'm not clear on what a 'shelf' design is.

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You?re welcome!

We don?t know if it?s your goal until you try it and other tunings, though looking forward to what you wind up with.

Well, the way we typically experimented with different reflex tunings way back when was by blocking off increasingly larger portions of the stock vent with scrap wood clamped to it and once the desired tuning was found, then a proper vent large enough to handle high power was designed/incorporated, which just requires making a new baffle board to replace the existing one or two depending on whether it?s an 825 or 828 series, so no cutting into the cab required unless you just want the vent[s] on some other side[s].

After T/S became popular, folks tended to add a removable gasketed vent board with whatever size/number of tubes was required and make the tube[s] too long and shorten them as required. Others just left the baffle in place and slid the tubes in with a tight slip fit and not pushed in all the way, so that they could easily be removed, otherwise any loose fit could be temporarily sealed with cloth/whatever shims or with blu-tac or similar, i.e. no need to flush mount them for testing.

A shelf vent is one where a panel is used to box in three sides of a cab [AKA tunnel or slot vent]. As you can imagine, these are a bit harder to experiment with in existing cabs.

GM

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Originally Posted by Phil-G

i have 416 8Zs (from a set of 846b valencias), similar to the set in panomaniacs a7-500s http://www.hostboard.com/forums/f700...ey/index9.html and after reading this part of the thread it was pano who suggested the 8" x 6-7" port. but thats what i'm working with. when i get what i want. i'll go ahead and cut a new bottom panel and finish it.

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IIRC he has hybrid A5?s with custom XOs and 416s. Regardless, this vent puts tuning down around Fs [my preference for wall or corner placement] and if driven by a high output impedance, then making an effort to tune it exactly to Fs is normally the best overall performer.

GM

And thanks again, GM!

I just had a weird thought. Since I'm in the process of building crossovers for my 604s and getting my 828 cabs ready for their "close-up", I was wondering how my 604Ds would sound in an 828 cab. I'm sure someone has done this, drunk as they might have been at the time.

You're welcome!

Not too weird, a few of us thought the 604E sounded pretty good in an 825 plus these folks took the idea to a whole 'nother level of weirdness: 1979 STANLEY SCREAMER

The 'daddy' of this weirdness was the original A6 though and what spurred me into trying a mini-me version: http://www.voiceofthetheatre.com/ima...att1945.10.jpg

In this pic you can see how much bigger the A110 cab was Vs the 800 series:

GM

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Originally Posted by alancohen

And thanks again, GM!

I just had a weird thought. Since I'm in the process of building crossovers for my 604s and getting my 828 cabs ready for their "close-up", I was wondering how my 604Ds would sound in an 828 cab. I'm sure someone has done this, drunk as they might have been at the time.

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Somebody did it because I remembering them saying they did it...They said it wasn't too bad sounding either.

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Originally Posted by GM

You're welcome!

Not too weird, a few of us thought the 604E sounded pretty good in an 825 plus these folks took the idea to a whole 'nother level of weirdness: 1979 STANLEY SCREAMER

The 'daddy' of this weirdness was the original A6 though and what spurred me into trying a mini-me version: http://www.voiceofthetheatre.com/ima...att1945.10.jpg

In this pic you can see how much bigger the A110 cab was Vs the 800 series:

GM

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That's enough speakers to fill a small stadium.

Well, you know what this means...stay "tuned"...

Thanks!!

So I got my N801-8As the other day and finally got around to mounting my 515Bs in the 828s and hooking them up.

I get no HF from one crossover. The other seems fine. My question is, for $150, should I just send them back and build my own or are these worth fiddling with? I can probably repair it, but for $150 I shouldn't have to.

BTW, the 515Bs sound pretty darn good, even with the backs off!

So I think I'm going to return the N801-8As, I'll probably end up bi-amping these anyway. For the time being I cannibalized the N1285-8Bs from my A6s. I cut out a replacement rear panel and got some matching paint from HD. I might just have to sand them down and paint them since I had to buy a gallon to get the color. I used a floor paint low luster base. Looks pretty good.

I need new binding posts since the originals got snapped off somewhere in their travels.

http://www.hostboard.com/forums/hbmc...2013/06/27.jpg

Are you using your 300B OTLs with these speakers? Bi-amping and getting a good match could be problematic. A digital Xover and another amp in your future?



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Originally Posted by zelgall

Are you using your 300B OTLs with these speakers? Bi-amping and getting a good match could be problematic. A digital Xover and another amp in your future?

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Probably not and yes. I have a Behringer DCX2496 still in the box, but I think the 300Bs need to be on their own. I thought about using them to power the horns and my 15W OTL to drive the bass. But the bass is so sweet with the 300Bs, albeit not going to blow the windows out at 1.5W. It has astonishing peak power and feels more like 8W in the bottom than 1.5. Then again, 300Bs are known for their mids. I guess I can always try it. My 15Wer driving the 99dB 515Bs and 1.5W pushing the 109dB 288s crossed over around 500Hz might be a good matchup.

I have a nice 3W Cathode follower transformer coupled amp and the parts to build another. I was thinking about using the two of them to bi-amp the A7s. They're KT88 based and I like that tube. I would leave the 300Bs to play nicely with the 604s in another room. The A7s would be my home entertainment system for movies and some music. The 300Bs and 604s would be for "serious" dedicated music listening.

Then I guess if that works out, the 15W OTL would get moved to the BR or shop. The cathode followers have quite a bit of gain and don't really need a preamp. The 15W OTL likes a preamp.

Anyway, that's what swimming around in my head. All subject to change without notice.

That sounds great Alan. It sounds like you've got a well balanced system. I'll bet it sounds amazing. Nice work.
And a great description of what you did.
I'd like to hear more about the otl method you used.