"Crossover Design for New Project"

[Earl K]

John,

Here's an overlay ( within REW ) of your 288 drivers, #s 1 & 2 .

The correlation in the FR between the two is very very good/uncanny even ( excepting of course the suckout at 8300 hz ) .

Are you sure they aren't FRs of the same driver ( but at a different axial point ) ?
- It wouldn't be the first time that a "cataloging malfunction" muddied the waters .

<> cheers

PS : hope the missus is alright

[Earl K]

Here's the predicted FR of your 288-8E unit #1 ( accomplished from within REW by tweaking the active EQ module) .

The net result, is very smooth / & ( IME ) would sound great even without a tweeter .

<> cheers

- A clever filter designer could transpose these active filters into their passive equivalents and accomplish something very similar, ( after first attenuating the midrange some ).

[Altec Best]

John,

Here's an overlay ( within REW ) of your 288 drivers, #s 1 & 2 .

The correlation in the FR between the two is very very good/uncanny even ( excepting of course the suckout at 8300 hz ) .

Are you sure they aren't FRs of the same driver ( but at a different axial point ) ?
- It wouldn't be the first time that a "cataloging malfunction" muddied the waters .

<> cheers

PS : hope the missus is alright

Thank You Earl she is doing fine it was caught very very Early I've been doing a rain dance for the past few days !


Let me first say that these were some of the nicest 288's I ever seen.I bought 2 pair from a lawyer who was handling the estate of Altec engineer he said who passed away in Feb. 09 Unfortunately RIP.They were upgraded he said so when I got them one pair had the 288G diaghram 23763 and the other pair had a 299 diaghram 25584 Take a look.With these labels on them that is covering the original 288C label.

WRT the same driver no I used the same 511E horn but unbolted one mounted the other.The plots are Drivers 1 & 2 Thanks for your very,very Gracious help Earl

I'm doing the off axis of the T350's started yesterday I sent Michael a room dims because he has some sort of software for modeling best location.I also did the T/S of the new 416's I just received.I sent them to Michael too but he doing a gig today.Here are the new ones.










Thanks Again Earl !!!!!!!!!!!!!!!!!!

[Altec Best]

Are you sure they aren't FRs of the same driver ( but at a different axial point ) ?
- It wouldn't be the first time that a "cataloging malfunction" muddied the waters .

I could always measure them again while I got the test gear set-up.As I'm doing the off axis of the T350's I could measure the 511/288's again

[Panomaniac]

I was actually on the phone when as the measurements were done. I heard John take one 288 off and install the other. At least I think it was the other.

I've been working on a passive for this. Thanks Earl for your version, it will help mine.

[Panomaniac]

I've been running some speaker and room simulations of the rig in a software called CARA. It a room sim program, not speaker, but it does allow you to build a custom speaker and test it in the room. So I've been trying to see what difference a horizontal and vertical woofer layout might have.

Below is the calculated polar response of the 2 options near the crossover frequency. Two 15" woofers side by side or over-under. You can see that the shape is mostly just turned 90 degs. Not exactly, because driver spacing was not quite the same on the 2 different layouts. Red =100dB and green is =70dB. Looking straight into the cones.



Next I'll run the room sims for each.

[Altec Best]

Hey Michael to these eyes the Horizontal layout looks slightly better.Very Interesting ! The off axis measurements of the T350's didn't look so good either they roll off quickly they need to be pointed directly at seating position which is what would do anyway.But maybe I could use these NOS 802-8G's.What do you think.

[Earl K]

Hey John,

How goes the ( woofer boxes ) building project ?

Got any pictures to share ?


<> cheers

[Altec Best]

Hey Earl, How are you ? I got the wood Baltic Birch, man that stuff is heavy.I'm working on Room gain measurements I've slowed down a bit Unfortunately, as life has it's surprises around every corner.

GM had asked for room gain measurements to see how my listening room would respond to the woofers as they (woofer motors) measured a little disappointing.My NOS 416-8B's are the only ones at or near spec.So I'm trying to decide what to do with drivers 1&2 and 5&6 drivers 3&4 are the good ones(NOS) but we were trying to match them.Which left the best woof out of the equation which I didn't want to do.

So I'm going to measure one of my Klipsch Cornwall II's outside with ports plugged up and then inside to measure the gain.I'm using the Cornwall because it will be much easier to throw over my shoulder than a 19.

[Earl K]

Hey Michael to these eyes the Horizontal layout looks slightly better.Very Interesting !

Well, you get to chose your own poison here .

Horizontal alignment of the woofers obviously sends much less energy into the walls ( & you are in the corner if I remember correctly ) but this choice will also send more energy ( relative to a vertical alignment of the woofers ) into the floor & ceiling .

Vertical alignment of the woofers flips these energy transmission ratios .

Since most of us have rooms that give different sonic signatures of walls vs ( floor & ceiling ) the choice of vertical or horizontal alignment will result in different voicings from the speaker ( since the 2 choices interact with the room quite differently ) .

<> cheers

FWIW, I have twin woofs vertically aligned quite near walls & situated near corners and don't hear any negative contribution from, "too much energy" bouncing off the walls .
- Mind you , I do use a few acoustic treatment panels (2'x4' auralex foam ) to control "mid-band bloom" .

The off axis measurements of the T350's didn't look so good either they roll off quickly they need to be pointed directly at seating position which is what would do anyway.But maybe I could use these NOS 802-8G's.What do you think.

I suggest that you get ( or build ) a small 60 by 30 degree horn ( I'd buy one with an elliptical mouth with an exponential flare ) mated to your driver and see if you can make the relative gains work between the ( lower output 8K to 16K) UHF of the 802 versus that of your 288-8E . Your bound to learn something about relative sensitivities if you do this .