Cornwall crossover help

[MoparBob]

I was just sweeping my room after making some changes to the room. I don't like what I saw. I should have done this years ago but was working to much and now I have time. I used Stereophile test disk #3 and a Radio Shack SPL meter.This would be my 84 Cornwalls, a dip of 11db at 400hz and a peak of 12db at 6.3k and it falls off fast after 10k. It's 21db down at 16k. It also has a peak of 14db at 25hz, but that is the room. So I need to make some changes

[MoparBob]

Sorry I was running stereo with RSW15 sub

[djk]

"a dip of 11db at 400hz "

400hz is a floor-bounce dip, can't be helped.

" falls off fast after 10k. It's 21db down at 16k"

Buy a Crites tweeter.

"and a peak of 12db at 6.3k"

Change the crossover to have a low-pass filter at 4.5Khz and an 18dB 4.5Khz high-pass for your new Crites tweeter.

[hklinker]

I agree with djk, the Crites tweeters will take you out way past the K-77. They should be crossed at 4500 Hz. The K-77 was so susceptible to blowing that they crossed it higher to protect it. But the APT 50 driver will go down to 3500, no problem. A much smoother sound too! []

Herb

[MoparBob]

The floor is carpeted concerte, so that's not helping. I also have the left side Corn 1 in. from the side wall. I do have Sonex that wall, but that is not helping at 400hz. I have been looking at Bob's tweeters, but I need 7 "ouch". or 3 for the fronts. That peak at 8k needs to be looked at first.

[Guest David H]

I was just sweeping my room after making some changes to the room. I don't like what I saw. I should have done this years ago but was working to much and now I have time. I used Stereophile test disk #3 and a Radio Shack SPL meter.This would be my 84 Cornwalls, a dip of 11db at 400hz and a peak of 12db at 6.3k and it falls off fast after 10k. It's 21db down at 16k. It also has a peak of 14db at 25hz, but that is the room. So I need to make some changes

I agree the Crites tweeter is a good upgrade, I personally do not care for crossing 4.5 khz, but with the stock metal K-600 it may be an improvement.

Using the Shack SPL meter, did you use the calibration chart? That meter is a valuable tool, but it varies.

http://www.audioxpress.com/magsdirx/ax/addenda/media/koya2811.pdf

Dave

[Guest David H]

Got this from AVS.

This is apparently the accepted response for the radioshack 33-4050 analog meter (and the 33-2055 digital meter as well).
(Taken from Home Theater Shack forum / REW RADIOSHACK-33-2055_4050.cal file.) I am just posting this for quick and easy reference...

Hz dB (so, for example, add 16.91 dB to a meater reading taken at 10Hz to obtain the actual level)
7 -27
8 -22.55
9 -19.37
10 -16.91
11 -15.27
12 -13.74
13 -12.42
14 -11.33
15 -10.28
16 -9.28
17 -8.53
18 -7.86
19 -7.12
20 -6.56
21 -6.18
22 -5.77
23 -5.41
24 -5.1
25 -4.9
26 -4.54
27 -4.27
28 -4.03
29 -3.73
30 -3.53
31 -3.25
32 -3.04
33 -2.84
34 -2.61
35 -2.54
36 -2.44
37 -2.28
38 -2.13
39 -1.97
40 -1.8
41 -1.75
42 -1.6
43 -1.54
44 -1.51
45 -1.43
46 -1.34
47 -1.23
48 -1.12
49 -1.02
50 -0.9
51 -0.82
52 -0.68
53 -0.64
54 -0.58
55 -0.5
56 -0.46
57 -0.38
58 -0.37
59 -0.36
60 -0.35
61 -0.34
62 -0.33
63 -0.32
64 -0.31
65 -0.31
66 -0.31
67 -0.22
68 -0.22
69 -0.23
70 -0.23
71 -0.19
72 -0.19
73 -0.17
74 -0.1
75 -0.1
76 -0.07
77 -0.06
78 -0.03
79 -0.01
80 0.00

And from 80 Hz out to 200 Hz (in 1 Hz steps) the values are all listed as 0.00.

[MoparBob]

Thanks GotHover This meter has been stitting in my shop for years. I use to use it for 1k speaker match in the 80' and 90' for a 5.0 setup. I always used a tone gen and spectrum analyzer, but I no long have use of them. I no longer work there. Even with that the dips and peaks are still there not as big. I have a lot of time but not money at the moment so I will try some things for the lows.

[MoparBob]

Ordered 3 CT125 tweeters and cross over parts today. If I like the CT125's I will buy the for my 4 Heresy's so all 7 speakers voice the same.

[MoparBob]

Rebuilt the crossovers in the Cornwalls. I now have better bottom end, a little flatter and the volume went up by 2db. The CT125's were a great upgrade. More detail and a little more open than the K77's. I need to add the CT125's to my Heresy's. The mids still need some help. I'm looking at Bob's Cornscala crossover with a cap change so I can us it with my stock Cornwall horn.

[hklinker]

Rebuilt the crossovers in the Cornwalls. I now have better bottom end, a little flatter and the volume went up by 2db. The CT125's were a great upgrade. More detail and a little more open than the K77's. I need to add the CT125's to my Heresy's. The mids still need some help. I'm looking at Bob's Cornscala crossover with a cap change so I can us it with my stock Cornwall horn.

As an alternative you should check with GotHover about switching to his Fastrac horn. I changed mine out and what a difference! I thought it would be difficult changing the motorboard for the bigger opening, but he provided me with a template and it took literally 10 minutes to cut the hole and mount the horn. All you need is a router with a flush trim blade and a little black paint. It actually took longer to clean the sawdust out of the box!

You can change the crossovers too, but it will set you back almost as much as the horns if you use good caps. For the money you will get the biggest bang for your buck by upgrading to a good squawker horn.

Good Luck!

Herb