Tell me about the 816

[rghinton]

Jeff, You about have me convinced to build 817's, instead of 1/2 size 817's, so as to avoid the resonance frequency problem of the parallel sides. I do not know the formula on how to determine the resonance frequency for the parallel sides of the horn. If I build the 817's and cross over at 500 Hz, will the resonance frequency problem be out of the usable range of the 817's? Thank you so much. I am glad that we had this conversation before I had the 1/2 size 817's built. Reed G. Hinton

[dennis gilliam]

I have used a pair of 817A's for years in my roadshow portable(!) system. They are loaded with 515C's, and have always come through with flying colors (or music or anything good of your choice).

They are teamed with a MR64/291 horn each. I'll have to get some jpg's and post if I can do so.

Sonically, they are much easier to excite over an 828 or 825 cabinet, and do not seem to have a "peak" resonance below cutoff (1kHz).

Folks love the sound on location, and always ask just what it is I do different from the usual music manglers with their Renkus or Peavey or Yamaha junk.

[jmarkwart]

Reed,
The fundamental frequency is calculated by dividing 565 by the length between the parallel sides (in feet). The 817 doubles that length to 32.35 inches over an 816, and thereby halves the standing wave fundamental from 420 Hz to 210 Hz. Doesn't matter if you use one driver or two. This would probably sound more acceptable than an 816's standing wave, that is in the lower midrange, as the 817's wave is an octave lower and is just above where the 817 comes out of horn loading in the 125 to 175Hz range.
Jeff

[rghinton]

OK! Now that we have decided that I will build 3 - 817 enclosures for my home theatre L-C-R, I am thinking about putting them on a 1 foot high stand and setting them on their sides. The horn would flair down and up. This would be kind of like 3 mini 210's. I will still use my 805b horns and 288K drivers and crossover at 500Hz.

I want to use corner enclosures for my rear surround. I have been looking at the plans for the Altec 606A bass reflex cabinet. I will be much closer to the rear surround and I don't think that horn systems would be good that close.

Any thoughts on the 817's on their sides and the 606A cabinets?

Reed G. Hinton

[rghinton]

Addition to my last message:

I would be using a 515E in the 606A cabinet and on top of the cabinet would be a 511E horn with a 288K driver crossover at 500 Hz. I would probably build the cabinet high enough for a horn cavity. I would use one of these systems in each rear corner.

Thanks for your thoughts.

Reed G. Hinton

[marcuswilson]

Reed,

The 817 is basically set up to direct sound over a 90 degree arc horizontally and 40 degrees vertically. If you put it on it's side you will be putting a lot of sound at the floor and a lot at the roof. In 99% of rooms it will sound better the normal way.

Be careful of comparison with the 210 cabinets as they were designed to join with each other side to side for more power. Also, large cinemas have balconies etc so there needs to be sound projected upwards. Not likely in your situation.

Rule 1) Avoid putting sound where it is not required.

Like conelrad, I also use 817s for PA, I have 8. As 2 way they sound amazing with 515 woofers and 291 HF on Mantaray MR94s.
Mostly I use them with subs below 80Hz and fit 421-8LF drivers. I get much more SPL with a QSC PL-4 on the mids giving up to 800 watts into each 421 (rated at 125 watts)! The 421s disintegrate after a year or two of this treatment, but I never burn out the coils!!!

Touring sound guys who normally use Turbo, JBL, etc often comment how much they enjoy using my system. Interesting.

[Steve Burger]

I asked Jim D about the parallel side the other day and he mentioned that with the larger 817 it is easy to modify the flares to completely eliminate any of the problems that may be associated.

[rghinton]

Did Jim D. mention how to modify the flares? Would this be something that I would do during the construction of the 817's? You guys are really a big help and I appreciate it. Thank you.

Reed G. Hinton

[rghinton]

The Altec 816VI enclosures parallel horn sides are 17.75" apart. My calculations indicate that the resonanent frequency would be approx. 382 Hz. This would be well below the 500 Hz crossover frequency. Hmmm ???????

[ckdf]

I?m currently building them too, but are not done yet. For mine the parallel sides are 16.14" apart which would yield 420 Hz. I plan to try some options to address this resonance. First would be some RLC notch network. Second I would like to try to put an additional board into the horn that would kind of split it into two halfs. The first resonance then would be at twice the original frequency i.e. 840 Hz in my case. Has anyone tried that? Last but most challenging to construct would be to add tilted sidewalls that extend to the outer edges of the cabinet on the front side and end at the speaker cutout on the speaker board. I think the A7?s should have the same problem only to a lower extend as due to the one board being tilted the "Q" of the resonance should be lower (instead of one pronounced resonance frequency you now have a certain "range" where standing waves can occur)