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jwc

Dual 15 inch Corner Bass Bin - Cornscala dbb

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Yep. #17

I'm real curious if the fabric will cause any change in sound for the top section.

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I'm real curious if the fabric will cause any change in sound for the top section.

Yes, and you will notice it immediately. There will be a slight drop in output, you will lose a bit of the crispness in the treble, and the image will sound more diffuse. You can relax though -- I'm sure it's all just in my head.[;)]

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I'm real curious if the fabric will cause any change in sound for the top section.

Yes, and you will notice it immediately. There will be a slight drop in output, you will lose a bit of the crispness in the treble, and the image will sound more diffuse. You can relax though -- I'm sure it's all just in my head.[;)]

The top section grill addition does look better. Wife definately agrees. I will have to listen for awhile to make sure there isn't a loss of "crisp" sound.

post-16499-1381927174729_thumb.jpg

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Other angle. Flash goes right through the fabric. Can see the port and some of the woofer. Not visible in regular room lighting.

post-16499-1381927174788_thumb.jpg

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Those are outstanding! You DESERVE to feel proud of your accomplishment.

I sure wish that I could hear them! Congrats on a great looking design.

DM

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I need a consensus regarding the sensitivity of the bottom half of this thing. Right now, I think it's about 104dB.

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jw,

That's a serious looking speaker you've built.

Is the crossover for it waiting for the 1.6 mHy inductor I just adjusted? I'll be shipping it back to you tomorrow BTW.

Al K.

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I need a consensus regarding the sensitivity of the bottom half of this thing. Right now, I think it's about 104dB.

Dean. My opinion is that it is 104db. If one wants to consider that the Cornwall is REALLY 101db then you could argue that my dbb bass bin is 107dB. I think the Cornwall realistically is 98db...at least the lowend.

I posted a graph earlier of what this speaker did with TrueAudio RTA and the low end was almost "flat" with the highend. This is with the Type A network so you would have to think the bass bin is close 104 dB.

When I run plots with WinISD of the K33 in a Cornwall cabinet, I get that the low end is really about 98dB as opposed to the published 101 db. Here lies the descrepancy.

I will tell you that the the speaker now has a "balanced" sound in my room. Even the JBL tweeter doesn't come across "hot". It is unattenuated. It is rated at 105dB.

Al

Yes, that Crossover you and Dean came up with is for this speaker. Even right now it is the best sounding speaker I have heard in a long time. I can't wait to try the ALK version network on it. I'll post a pic of the network so far. I'm just waiting on the inductor you have. There isn't a BIG rush for it so finish the testing and such since you are doing me a favor.

jc

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Well the K-33 is a 4 ohm driver so if they measured sensitivity with

2.83V (or watever it is) then it would be getting fed 2 watts and be

101dB. So I think it's 98dB too when getting 1 watt of power.

Btw, did you wire them in parallel or series? If in series, then you only get a 3dB gain.

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Well the K-33 is a 4 ohm driver so if they measured sensitivity with 2.83V (or watever it is) then it would be getting fed 2 watts and be 101dB. So I think it's 98dB too when getting 1 watt of power.

Btw, did you wire them in parallel or series? If in series, then you only get a 3dB gain.

Doc, they currently are in parallel. I agree with you statement.

Al and Dean came up with a network that is a constant impedence design and with a bandpass. They designed it with the intention to leave the K33's in parallel. I will have to let one of them explain to you that the estimated overall impedance of the speaker will be about 3.5 ohms with this network.

jc

post-16499-13819276657042_thumb.jpg

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Here is the network w/o a few connections to the autoformer and w/o the 6 ohm resistor and 1.6mH inductor. Will be able to biwire in future if needed. Due to size, did a break out for the low pass.

post-16499-13819276657662_thumb.jpg

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Who,

Yes, 3.5 Ohms is simply an estimate. It's based on my measurements of the K33 complex impedance in the Belle. I have two vintages of Belles. My set of two are from 1976 or so. Those measure as 6 Ohms in sereis with 1 mHy inductance. My later Belle, made around 1985, measure around 7 Ohms in sereis with 1 mHy voice coil inductance. With two in K33 parallel, that comes to about 3.5 Ohms in sereis with 0.5 mHy. The network design utilizes the inductance and leaves the resistive part. IN any case, the K33 is NOT 4 Ohms. It only seems to become 4 Ohms if you stick a "Zobel" on it. I don't use that trick unless I haved no other choice.

Al K.

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What's wrong with Zobels?

Where did 101dB/2.83v come from? I just see a K-33 loaded in a Cornwall sized box putting out roughly 98dB/2.83v (probably at some given frequency and not across the whole range) and how much wattage it's taking to do it is up for debate. Tied to the low pass section of a network it's closer to 6 ohms -- so I'm going to go with that -- we'll call it 98dB/1.34 watts. You add a second K-33 and you're at 104dB/2.67 watts (3 ohms). This particular network pushes you close to 4 ohms at 3.75 and so we end at 104dB/2.13 watts. This is the way it works with solid state where output is doubled when impedance is halved. Who wants to take a stab at how it works with a tube amp?

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The Cornwall II is rated at 101dB...which is using the K-34E which I have been told is just a cosemtically updated K-33.

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Interesting, I never knew that. So, the Cornwall II has a tweeter that's 3dB less sensitive than the original, and a woofer that's supposedly the same as the K-33 -- yet they somehow managed to squeeze an extra 3dB of sensitivity out the Cornwall II over the original Cornwall -- which was 98.5dB. LOL, I give up!

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According to my tables the K33 and K24 drivers are both rated 92 dB. I built a big bass reflex enclosure for the K24 and I got 92 dB! I think with two K33's in a box you will probably get about 95 dB. Even my Belles with a horn woofer I bearly get 100 dB.

BTW: Jw, your inductor is on its way by postal prioriety mail.

Al K.

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JW,

Man I have to say this is one of the greatest threads I have ever had the joy of reading. It took me a few hours last night and then again this morning. Excellent job! I do have one question pestering me though. What made you decide to make the speaker a corner placemnt type similar to the Khorn rather then makeing it some other dimension? Or did you just want the corner horn look?

Craig

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The corner design was to accomidate the most space w/o having a monster of a speaker. Terry Cruse and I belabored this idea.

Each K33 is in 6.15 cubic cabinet so there is 12.3 cubic feet for the bass bin only. If you look at the earlier pictures of the bass bin by iteslf, it doesn't appear that large. The back end is a trapezoid shape that can fit flush with the corner. HOWEVER, it doesn't have to be in the corner. In fact mine is toed in a little to adjust to the size of the room and listening position. The trapzoid configuration also prevents a large cabinet from having large side panels potentiating resonance.

If I were to build the cabinet to accomidate both woofers and make it a cube, It would look rediculous. It would be like a refridgerator shape.

The sided ports sound better than I had predicted. Much better than my Cornscalas which have the ports identical to the Cornwall. The dbb have a port like a 77 Cornwall that is split and turned on Their side.

I'm glad you chimed in because I built this to get the Cornwall bass I like and be at the dB of a Khorn. My final plan was to get the best network I can (in the works) and then go to a tube setup.

I just purchased A Music Hall MMF-5 TT. My preamp is a McIntosh MX119. I eventually will need a tube amp.

jc

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