soundhound:

Your main’s short horn woofer versus center’s JBL woofer, won’t that cause any mismatch? I guess not, otherwise you wouldn’t have set it up that way. Just wondering how it works.

For front L/R I'm running an old pair of homemade (about 1970) bass reflex speakers (originally Altec 416As but went to JBL2226Hs) with Altec 511 horns and 808-8A drivers. I'm using a dbx Driverack PA electronic crossover (originally homemade, then Marchand, then dbx.) I'm using 4 channels of an Outlaw 7100 for amplifiers. Surround L/R speakers are Altec Model 19 driven by 2 more channels of the 7100. Front center is phantom. Subwoofer is an 18 inch Velodyne. The whole thing is driven by a 950.

For Soundhound: Do you need 2 15 inch woofers for the center channel or is it for balance/symmetry? Did you build your center channel?

regards, Jim Roy

>>>For Soundhound: Do you need 2 15 inch woofers for the center channel or is it for balance/symmetry? Did you build your center channel?<<<

It is for symmetry and the two 12" woofers can keep up better with the main's 15" ones. The horn is the same 511/802G combination as on the mains but the crossover has been raised to 800Hz to better integrate with the tonality of the mains. The matching is actually extremely good between the mains and the center. The 511 horns all have about 20 pounds of Aquaplas applied to the exterior of the horn to make them completely inert - the metal horns have a tendency to "ring" when rapped with your knuckles otherwise. The center 12" woofers are modified JBL 4412 cabinets.

[This message has been edited by soundhound (edited July 23, 2004).]

>>>Holy smokes SH! You could give THX a whole new meaning!<<<

The four JBL 2245H/4645 18" subwoofers are THX certified, as are my surrounds, but nothing else in my room is (the tube amps would undoubtedly flunk THX tests - I feel so bad....). I did not buy them becasue they are THX certified, but they just happened to be the ones I wanted (and I worked at JBL at the time). The subs are THX certified for commercial cinemas and there is also a version for home use as part of the K-2 system. I modified the tuning of the cabinets so that I get flat response down to 10Hz, while in stock form they go down to 20Hz.

[This message has been edited by soundhound (edited July 24, 2004).]

Soundhound,

When you say your x-over frequencies are 50Hz and 500Hz, what are your actual highpass and lowpass frequencies?

They are at 60Hz and 500Hz. A high pass and a low pass at each.

Soundhound,

I have been advised by some that the highpass and lowpass poles be staggered a half octave to ameliorate an "in phase notch". I am thinking that there are "real world" inefficiencies given the different drivers and electronics that results in less than a unity in the crossover octave. But I am also thinking that if the frequencies are staggered, there should be an additive amplitudinal change (a spike rather than a notch) in the doubled over region. What is your opinion on this?

I am just bouncing ideas at you before I order more frequency modules. I have not had a chance to measure the speaker output as a whole yet. I've only worked on individual drivers so far with truRTA.

With a 24 db/octave Linkwitz/Riley crossover network, the point between the low pass and the high pass sections is 6db down if both filter sections are at the same frequency. A 6db voltage dropoff, when summed, equals flat response through the crossover point. Assuming that the speaker drivers themselves physically have their voice coils on the same vertical plane, the frequency response in-room should be flat through the crossover region if the filter sections are at the same frequency.

With a Butterworth filter, the point between the crossover sections is only 3db down. When summed, this will yield an excess of energy through the crossover point. This might be what you are hearing about, but it is not an issue with the Linkwitz/Riley crossover network.

[This message has been edited by soundhound (edited July 28, 2004).]