Cornscala using v trac Questions

[shepjk01]

Well I was going to use gregs vtrac in my lascalas but have decided against chopping up the front panels. Instead I'm thinking off putting together some cornscalas with the dual k-33's and use the vtrac in a custom speaker. Instead of using the bms drivers I have a pair of jbl 2485j's that I have had for a while that I'm going to mate to the vtrac. The tweeter will likely be either a beyma cp-25 or crities ct-125. I know alk has downloads for the cornscala using two k-33's. I need help with a crossover design for my proposed configuration. Here are the specs on the jbl 2485j. I would like to use a 12 db slope at 400 and 4500hz.

SPECIFICATIONS:

Nominal Impedance: 16ohms

Minimum Impedance: 12ohms @ 5 kHz

DC Resistance: 8.5 ± 10% @ 25°C

Power Capacity¹: 120 W continuous program above 300 Hz

Sensitivity: 111 dB SPL, 1 W @ 1 m on-axis on horn²

118 dB SPL, 1mW on plane-wave tube³

Nominal Efficiency: 30% (500 Hz to 2.5 kHz)

Frequency Range: 300 Hz to 6 kHz

Recommended Crossover: 300 Hz or higher, 12 dB/octave minimum

Diaphragm: .23 mm 10.009 in) phenolic

Voice Coil Diameter: 100mm (4 in)

Voice Coil Material: Edgewound aluminium ribbon

Flux Density: 1.9 T (19,000 gauss)

Throat Diameter: 49 mm (2 in)
BI Factor: 19 N/A
Positive voltage to black terminal gives diaphragm motion toward the phasing plug
Dimensions: 235 mm (911 in) diameter
330 mm (13 in) depth
Mounting Four ¼-20 threaded holes, 90° apart
on 101.6 mm (4 in) diameter
Weight: 13.8 kg (30½ lb)
Shipping Weight: 14.5 kg (32 lb)
¹Continuous program is defined as 3 dB greater than continuous pink noise and is a
conservative expression of the transduceis ability to handle normal speech and
music program material. Continuous pink noise power ratings are tested with pink
noise input having a 6 dB crest factor. with a high-pass filter set at the specified
lower limiting frequency for two hours duration.
²Sensitivity measured with 1 W input at 1 m distance on axis from the mouth of a
horn with a Q of 6.3 averaged in the 2 kHz octave band.
³As specified by recognized standards organizations, sensitivity is measured with the
driver coupled to a terminated tube. The JBL sensitivity rating represents the SPL
in a 25 mm (1 in) terminated tube, using a 1 mW input signal (0.126 V into 16
swept from 500 Hz to 2.5 kHz. The sensitivity rating with a I W input would be
30 dB greater.

Also can the box that houses each k33 be changed in size i.e. more depth than height and keep the same slot port dimensions as long as the overall volume stays the same?

Any help on this would be very appreciated

[jwc]

Yes you can. There are some good network designs for what you are contemplating.

http://forums.klipsch.com/forums/t/58314.aspx?PageIndex=19

jc

[shepjk01]

jc,

Thanks for the link to the thread. Also thank you for posting the plans for the bass bin design as that saves me alot of trouble. I went to alk's site and downloaded the crossover designs for the cornscala. My biggest concern is the attenuation of the midrange? Without testing it I'm not positive how much hotter it will run than the rest of the system. Did your crossovers designed by alk allow attenuation of the midrange?

justin

[jwc]

Yes you can.

There is one version that XO's at 600Hz, another at 450Hz and another at 500Hz. All of these have a transformer with a swamping resistor to allow you to adjust the attenuation of the mids on the fly.

The dbb's will run about as hot as a K77. I had mine running wide open with the mids (Altec 902) attenuated. You can use a 16 ohm or 8 ohm mid driver.

jc

[jwc]

BTW. Be careful that you don't use "single woofer" cornscala network. ALK's website offers no explanation of this. I attempted to have a thread that can be referred to for an explanation, but I later asked for it to be deleted as it became a PITA for me.

[shepjk01]

jc,

how was the bass ouput on the dbb compared to the lascalla. I'm still debating modifying my lascala to accomadate the vtrac or build the dbb's. The only reasoning behind the dbb was I'm curious if there is more bass output from them. Also I located the schematics on al's site and they are what I was looking for if I decide to go ahead with the build.

Justin

[jwc]

I've had la scala 1 and 2's, dbb's, Cornscalas, Cornwalls, chorus, jamboree, jubilee clones, and KPT-904 dual 15" woofer bins all auditioned from the same corners. I can easily say that my dbb's had more bass impact than any of the others. I've contemplated building them again. There are pros and cons of bass reflex vs horn bass and I don't want to go there.

jc

[shepjk01]

jc,

Thanks for the help and suggestions on the cornscala. I have decided to not go ahead with the project mainly due to the cost of the components for the steep slope crossover which would be the only one I would want to use in the cornscalas. I'm just going to modify my lascalas to fit gregs v-trac and be done with it.

[mowntnbkr]

JC,

Where do you recommend getting the crossover parts. This looks like something I want to build. I would be using Gothovers Fastrac midhorn and Bob's tweeters. Any advice would be greatly appreciated. My wife actually likes the footprint of the Khorn bettern than the cornwall, I just didn't have the right corners for Khorns and this is right up my alley.

Sam

[jwc]

For the low pass, I typically use air core inductor solens and solen fast caps.

For the HF portion of the filter, I use Auricaps and Solen Litz inductors (which are a little challenging to solder). If there is a cap in the HF filter that is parallel to the circuit, I will use a solen fast cap.

Sutoformer from crites either 3619 or 3636. Mills resistor for the swamping resistor.

Some of this may be overkill.....I'm am firm on the auricaps that are in series with the HF filter.

I have some of Gothovers fastracs too. They will either go on a Cornscala or another dbb. Haven't decided.

Are you interested in Cornscala or dbb?

jc

[mowntnbkr]

JC,

I bought the fastrac's with the intention of building cornscala's, but once I looked at the DBB I knew that was the route I wanted to go. I was going to buy some Tannoy DMT 215's, but they just have too big a footprint and this works perfect for me.

[jwc]

For 3 way with the fastrac....my preference would be the ESNdbb600Hz. The swamping resistor 3.6 ohms (10 watt).

I used the sonicaps when I made them. I would use Auricaps where the Sonicaps are.

jc

[jwc]

HF....I didn't use Litz inductors on this one.

[jwc]

LF......

[jwc]

So for three way, you would need the ALK ESN5800 or something similar. One additional resistor would be needed if you went this route. No biggie.

That is a lot of network....but so are the other three options for three way ESN with 450Hz or 500Hz. All with three boards to complete the network.

There is a ALK non-ESN option too that XO's at 400Hz for the mids. This is like the ALK Universal A but for the dbb.

That one is listed on ALK's website. I have it somewhere on my hard drive if you want it. It is a one board option.

There is another option that is not ALK approved but a Hack job of a Dean Super A combined with an ALK Universal A. This worked fine really for low volumes. But cranking it........the bass was all over the place. Needed a steeper slope I think. The two woofers together played way out there.

These were the "castles" seen on the thread.

jc

[jwc]

Here is a complete set for a 450Hz three way version, You can see there is a lot of board there.

jc

[dkalsi]

Hey JC,

Any comments on why the bass impact of the DBBs will be greater than the Jamboree? - They both include the same woofers except one is horn-loaded and the other is vented. I would imagine the DBBs to have better low end extentions, but to have better overall bass impact than the much more difficult to build Jamboree is somewhat surprising.

If you could please share your thoughts on the aforemetioned bass bins, I would greatly appreciate it.

Thanks,

Dhar

[jwc]

I'm trying not to start a war here. I think it all comes down to preference.

Good question....and I guess you would have to experience both for comparison...which is hard.

I'll start by making the analogy of the scala bass bin with the same woofer as a cornscala. Some choose cornscala or cornwall do to the love of the bass. Is it better......some would say yes...some would say no.

The jamboree will go lower than the scala obviously. But same type of analogy. Same dual woofers.....bass reflex vs horn.

I listen to a lot of funk and metal. For some reason........the bass reflex fit this bill for me. So I don't want to say horn bass isn't as good. Don't want to go there. So currently...I listen to a lot of that style music on a non horn system in general.

Take a look at this curve. Now this is outside both loaded in a corner. Now...I was making modifications to the jamboree in a ton of different configurations. So this curve wasn't necessarily the best one.

I have contemplted building the dbb's again with a slight change.......but who knows if I will get to it anytime soon.

jc

[shepjk01]

Jc,

Are two of the boards of the three shown for the esn-600 could they not just be put on one board as al does in the extreme slope networks or did you do it for size purposes. Also what is the point of using two 3619 autotransformers isn't only one needed for the sqwaker?

[pzannucci]

If you are going to try and use two k-33 woofers and they are basically 4ohm woofers, how ugly is the impedance going to be with the two together in the bass? Will typical amplifiers be happy driving that impedance? I haven't measured the k-33 woofer alone myself yet.