Help designing an LF cabinet.

[Panomaniac]

I thought that the 1000+ years of combined Altec experience on this board might be able to guide me in the right direction for an LF cabinet to match my 811/806a in a passive 2-way system.

After much research, reading, calculating, looking at driver specs, speaking with gurus, consulting of crystal balls, etc. I have narrowed my ideas to two choices.
Perhaps you can help steer me in the right direction, or even offer a fresh perspective.

Number One:
The 12" solution.
A 414 driver in 3 cubic feet. An imitation of the Altec 614 Utility cabinet. Maybe not the same proportions, but the same volume and tuning.

Number Two:
The 15" solution.
A 416 driver in a ~7 cubic foot cabinet. Basically an imitation of the trusty Model 19, but turned on its side, so that it is taller than wide. Horn on top, natch.

My living room is small, the listening position about 10 feet from the speaker fronts.
The sound I want is big, full, dynamic, live. The bottom octave or so is not important, the range of 50-500Hz is much more my concern.
From a pure sonic standpoint, Solution 2 is likely to do what I want, but might overwhelm my living room. And it would be a tight squeeze to fit the big boxes in. The 416 is likely to sound bigger, but the 414 might mate better with the 811 horns.

The cabinets will be built to look like an entertainment center or console. Perhaps not a one piece unit, but there will need to be a center unit to hold TV, amps and other gear. Left, Right and Center will all match for high WAF. I already have the wifey seal of approval. Smaller would be better (and more affordable) of course.

This idea is only in the early planning stages, so I'm open to ideas. No hurry, either. Other drivers are welcome, but I do like the Altec sound. Dynamic and highly efficient is the goal.

[Old Guy]

With the 811 horns I'd recommend the 12"

You could always add a sub later if needed.

[GM]

Greets!

The need for controlling directivity increases with decreasing room size if considerable room treatment isn't an option, so the lower the XO point, the larger the woofer must be and the lower its required usable HF extension. For 800 Hz, the 9844's dual 414 baffle layout is a 'good enough' match as is of course the M19's 416/1200 Hz layout, so any other combos will either need to be with multiple smaller drivers to get the desired beaming directivity and/or with a short WG attached to ~match them to the 811/'y' XO point. Considering 'throw' issues Vs listening distance and limited room width, Altec's choice of a higher XO point seems the better choice, though from a resolution POV, using four wide BW 8"/channel seems a better choice than a single large driver that's deep into its break-up mode BW through the XO BW. Unfortunately, I don't know of a suitable driver unless you're willing to do a three way or add a sub system.

GM

[Panomaniac]

Thanks for the info.
GM
So you don't think the single 414 would cross well with 811? Need duals? Don't think that will fit in my room, but maybe.

I have heard systems that were wonderfull with a 15" crossed to a horn at 700Hz. The 811 won't work that low, but 900Hz should be a realistic point, right? And you're saying that an Altec 12 or 15 won't play well that high?

Or is it simply a matter of beam pattern? I'm a bit confused here.

[Old Guy]

I don't see why a single 12 should be a problem.

[GM]

Originally posted by Old Guy:
I don't see why a single 12 should be a problem.

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

I'm surprised that someone with a prosound background doesn't feel the need for controlled directivity (~flat power response) over as wide a BW as practical in a HIFI app as in a live venue, especially in a relatively small room/close listening position, but without either a WG on it or significant room treatment we'll have to agree to disagree.

GM

[GM]

Originally posted by Panomaniac:
Thanks for the info.
GM
So you don't think the single 414 would cross well with 811? Need duals? Don't think that will fit in my room, but maybe.

I have heard systems that were wonderfull with a 15" crossed to a horn at 700Hz. The 811 won't work that low, but 900Hz should be a realistic point, right? And you're saying that an Altec 12 or 15 won't play well that high?

Or is it simply a matter of beam pattern? I'm a bit confused here.

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

You're welcome!

It will, just at a high frequency, defeating much of the point for using an 811, though a single 12" would be preferred if using a 1st order XO. Unfortunately, there's still the room interaction issue. Obviously, you can XO the 811 as low as 800 Hz/2nd order, but without a WG to control its polar response (beam pattern) through the XO BW, you'll ideally need room treatment for best performance.

Greets!

You're welcome!

It will, just at a high frequency, defeating much of the point for using an 811, though a single 12" would be preferred if using a 1st order XO. Unfortunately, there's still the room interaction issue. Obviously, you can XO the 811 as low as 800 Hz/2nd order, but without a WG to control its polar response (beam pattern) through the XO BW, you'll ideally need room treatment for best performance.

As 12"/15"ers go, Altec's do an excellent job in their TL BW, just that smaller is better since it will transition out of its pistonic BW at a higher frequency, ergo all else being equal, it will be more accurate and with greater resolution over a wider BW.

GM

[Old Guy]

Hi GM- you may well be right. It's been a long time since I worked in a 12 foot wide room.

[Panomaniac]

Thanks for the link to the Model 19 clones, very nice.

Sorry GM, I'm not getting it. You're going to have to back up and try again, it's not getting thru to me. Hit me on the head a few times, maybe that will work -it's not getting thru. There is a piece missing that I'm not understanding.

So if we take the example of a 614 utility cabinet in my room, it won't work well because of the polar pattern? Too wide? Too much room interaction?

Then what about the Model 19? Is it going to have a more narrow polar pattern that will work better in the small room?

[GM]

Greets!

Too far to reach to smack you up side the head to get your attention! Sure wish I could afford a vacation to the 'paradise' where you live though!

Cab width only affects the frequency where the FR transitions from half to full space in-room and it's also very speaker position in-room dependent, so beyond the scope of this thread other than to note that in most rooms, if the cab is at least 30" wide, then no baffle step compensation (BSC) or digital EQ is required to tonally balance (flatten) the mids/HF to the LF and I assume why the M-19 is this width. http://www.trueaudio.com/st_spcs1.htm http://www.trueaudio.com/st_diff1.htm

What I'm referring to is ~matching the polar response of the horn with a point source radiator (cone driver) at the crossover point, so let's assume the 811 will horizontally control beamwidth down to 800 Hz into 90 deg (its included wall angle) before suffering baffle step (diffraction) loss to an increasingly wider angle with decreasing frequency (sound power rolling off like when outdoors). Ideally, we want a cone driver that will do the same, so to keep it simple, let's assume that its diaphragm has a 90 deg included wall angle too, ergo doesn't it seem reasonable that its diameter has to be the same width as the 811's terminus (mouth)? This equates ~to an 18" driver, so from this we see that as the driver diameter decreases, the XO point increases.

Unfortunately, it's not so simple since a horn projects its pattern further than a cone driver, which usually has a complex curve profile that requires both to be measured to find the 90 deg/whatever point. Altec has given us some guidelines though with the 9844/M19 for the 811/414/416, so those that don't learn from history are doomed to repeat it.

Or you can ignore all this and build whatever 'floats yer boat' knowing that there's been lots of folks over the decades with either Altec manufactured or DIY speakers that don't conform to any of this and thought they were the best sounding speakers ever.

GM