Stacking 511s

[edharbur]

I've been reading GM's comments about stacking 511s, and would like to give it a try. How do I hook them up? Series? Parallel? Second crossover? Different crossover? I have pretty limited electrical skills, so I'd prefer to stay with a "plug and play" approach.

Currently I'm using A7s with GPA 515LFs, 809-8a crossovers and 511 horns with 808-8a drivers in a 3200 sf shop. I'd prefer not to bi-amp or use active crossovers.

Thanks in advance-

[RonSSS]

Well, you have 2 choices then.
2 crossovers.
Or one crossover with 2 16ohm horns/drivers in parallel.

[Cal Weldon]

I am a believer in using the least number of drivers for the job. I have the 811 stacked on the 511 as they are mid and tweeter. What is it you are trying to achieve?

EDIT: I see the other thread and what GM was doing and the implementation. I say go for it, with the disclaimer YMMV.

[Phil-G]

i asked about this in another thread myself. i originaly asked about stacking 2 811s. gm replied

I?ve periodically posted about my success stacking 511s with two different drivers to create a pseudo- large format driven multi-cell except with a superior HF and a ?tighter? pattern control [especially vertically] to a lower frequency, so see no reason why stacking 811s with the 902 running ?full? and the other rolled off up high won?t work.

FWIW, Cal has been pleased with his stacked 511_811 combo.

All that said, if you will be sitting fairly close, then the extra pattern control might narrow up the 'sweet spot' too much.

GM

and also goodwill posted this pic,

Here's Cal and Pano testing it out...

now im trying to come up with a set like yours. i have a pair of decent 902 8As with an 811 horn. and i have a set of 511 horns that i'm pretty sure would go well with 802 8As.
so back to the OPs questian about crossovers, how do you have your set configured? also i was reading another post where GM stated that by stacking you effectively lower the xover frequency.

[edharbur]

I'm using the speakers in my cabinet shop. The room is approximately 50 x 65, with the speakers centered on the 50' walls, facing, more or less, each other. If I want to keep earning a living, there is not much that I can do about positioning. The men work on the front wall, my bench is centered on the back wall, about 35' from each speaker. Over the last couple of years, I've picked up Altec stuff here and there, and am now ready to put everything together. I'm using an old Denon receiver at the moment, but have a Mac 2105 and a Crown DC 300 waiting for me to complete a dustproof cabinet for them.

I started out with m19s with, I assume, original drivers and diaphragms. I will use these until I'm finished with the "standard" mods on my 828s. They sounded pretty good, but had a very small "sweet spot." Next, I put my 511s, with drivers freshly back from GPA on top (machinery layout prevents me from putting below, as suggested here) and hooked them up to the stock 1200 mhz crossovers. There was a world of difference. Larger sweet spot, crisper, very nice. This lead me to believe that I needed a pair of 1005s. I found a pair with throats and 288k drivers for a pretty good price. Having never seen a 1005 in person, they looked pretty good to me, and home I went. It wasn't until I got home, and with help from you guys, that I realized that I was sold 1004s rather than 1005s. Nobody's fault but mine.... I hooked one up, and it is definitely more "open" but not enough high end and a little less "punchy" than the 511s. Next step, if I choose to pursue the 1004 / 1005 experiment is to send the 288s off to Bill. I'll recap and start experimenting with my n-809 crossovers this week.

What am I trying to achieve? Trying to get the best sound, as determined by my tired old ears, that I can, over as much of the shop as I can. What I've read about stacking seemed pretty interesting, other than that the 511s shouldn't be splayed. This seemed like an interesting experiment that i could perforn with components I had on hand, or at least could round up pretty easily. I realize that stacking probably won't help with trying to get better sound to all corners of the shop, but "punchier" and "more high end" don't seem like bad things at all.

So, the questions are how do I hook it all up? Does "effectively lowering the xover point" mean I should be using xovers with a lower point (say 500) or does it take care of itself? Further, are my 1004s a reasonable substitute for 1005s, or does my search continue? If I go to 2 500 hz crossovers, do I wire them in parallel? If I go to 811/511, as per Cal, how do I cross them over as mids and tweeters?

Sorry to ask so many questions. Did I mention the Northeast Altec barbecue / tech session I was thinking of.....

Ed

[cradeldorf]

I'd get some grill cloth and make covers for them, just to keep sawdust out.

[GM]

Well, it lowers the LF corner frequency due to having 2x the driver piston, etc. and mouth area, so more power handling down near/at/below the XO point, so for a relatively low power app one can use up to a ? octave lower XO point if desired.

Due to the long dims, it ?sounds? like you need to first draw out both a scaled floor plan and side view of your room showing how much cab toe-in, downward tilt is available [if any], ditto if laying the cabs on their sides is an option.

Next, draw lines out to show each horn?s on axis alignment [note that the mid-bass horn has a slight vertical downward tilt, but can?t find/remember the number of degrees at this point].

Finally, draw out equidistant lines from each horn mouth?s axis line that ?best? covers the desired horizontal and vertical ?sweet spot? [seated/standing at the various work stations] to give us an idea what, if any, horn and/or stacked combinations might work well enough within the other constraints.

Wiring scheme will depend on how much measuring, tweaking, EQ you?re willing to do and whether it will be active, passive or a combination of the two.

FWIW, mine were series connected to get better the damping, lower current draw and increased inductance of the nominal 16 ohms and would have used 32 ohms if the old SET amp?s power supply could have handled it.

For SS, I?d still try series first, but it may require too much CD horn EQ for the amp?s voltage rails unless rated for 16 ohm systems.

Whether or not one horn will need to be rolled off up high will depend on how ?tight?/?sharp? the combined HF is to one?s ears, but my SWAG is that the distances are long enough that the two horns will appear as a coherent enough point source, at least for the 511, 811 or similar size.

GM

[Alien_Shore]

I'm using the speakers in my cabinet shop.
What am I trying to achieve? Trying to get the best sound, as determined by my tired old ears, that I can, over as much of the shop as I can. What I've read about stacking seemed pretty interesting, other than that the 511s shouldn't be splayed. This seemed like an interesting experiment that i could perforn with components I had on hand, or at least could round up pretty easily. I realize that stacking probably won't help with trying to get better sound to all corners of the shop, but "punchier" and "more high end" don't seem like bad things at all.

So, the questions are how do I hook it all up? Does "effectively lowering the xover point" mean I should be using xovers with a lower point (say 500) or does it take care of itself? Further, are my 1004s a reasonable substitute for 1005s, or does my search continue? If I go to 2 500 hz crossovers, do I wire them in parallel? If I go to 811/511, as per Cal, how do I cross them over as mids and tweeters?

I did much the same thing (goal-wise) in my garage. I wasn't trying to stack horns, but was trying to get the best sound out there with sub-optimal room treatments and speaker placement. It was a long process to get there, but what I wound up doing is using an active crossover to narrow down the XO points, XO slope, attenuation levels, etc. Then using what I learned with that, I built custom passive crossovers. I have old 416A (16-ohm) woofers in the 816 horns, and 802-8G drivers on 511B horns for the HF. Part of the challenge was getting a XO design that accounted for the different Z plots of the two drivers, and allowed some manual adjustment (via variable resistor in the HF notch filter). This is a parallel 2-way configuration. They sound amazing, considering that from a time-alignment perspective the positioning of the speakers is horrible.

If you are going to go with one woofer/two HF drivers per channel, a lot depends on your choice of amps as to how you wire everything up. You may want to bi-amp (woofers/HF) - probably a good way to go. Or, you can get creative in series/parallel wiring methods to manage the impedance profile of the load. For example, if you wire the two (8-ohm) horns up in series, the amp will see 16-ohms of impedance which will attenuate them down, which may be desirable if they are considerably more efficient that your woofer. If you put 16-ohm frams in the horns, you can wire them up in parallel, and the amp will see an 8-ohm load.

If you didn't want to Bi-amp, a series/parallel kind of thing could be done. Assuming all your drivers were 8-ohm nominal, you could series-wire the HF horns, then parallel wire those with the woofer, which would yield ~5.3 ohm load to the amp.

There's all kinds of things you can do here, and then adding in the crossovers, changes this around as well.

[Cal Weldon]

If you wire them in series you won't notice an attenuation so much. You gain 3dB sensitivity having two drivers but lose it by halving the current so you're back at square one when running a passive XO.

Oh, and just to clarify for those who don't know, that handsome, well trimmed and well fed person with his back to the camera is me. The shaggy, freaky looking dude that you wouldn't let near your daughter? -that's Pano.

[edharbur]

Sorry for the delay in getting a floorplan together; here's the link:

http://i.imgur.com/eXMKRVK.png

I'll try to get to a vertical section tomorrow. GM - I hope that this is what you were looking for.

Thanks again for the help I've received so far.

Ed