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Author Topic: Electro-Voice 848 CDP Horns, remember these?  (Read 24385 times)

Dan Brandesky

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Re: Electro-Voice 848 CDP Horns, remember these?
« Reply #20 on: April 27, 2010, 05:26:13 pm »

Thanks Art, that's what I thought I should do but I wasn't sure how horns reacted to being in spaced pairs.

I found a neat way to mount these on stands using speaker stand mounts like this one. All I have to do is use a bolt and a wing nut to attach the horn bracket to the mount, and plop it down on a pole. If I really squeeze them together I can even get two on one mount.

I also found the perfect amplifier for them today, for the perfect price on ebay: $9.99.  Shocked It's a 60W University Sound 1808-60 amplifier. The peak power of the horns is 60W at 8 ohms, so if I connect both of them together in parallel I get about 30W per horn, which is nice and safe and should be plenty of power. It also has an interesting "trumpet protect" switch, which according to the schematic is a .01uF capacitor that gets connected in line with the audio to the output transistors. I don't really know what frequency this correlates to, so I'll have to try it out, but I imagine it should work pretty well. Even then I'll still have the fall-back 100uF capacitors connected to each horn. I'm actually wiring them in line with the input cords on the horns so they can't be goofed up. 100uF isn't an awesome HPF, but it at least helps; the corner frequency is about 200Hz at 8 ohms so that at least puts 100Hz at about -6dB, better than nothing. Depending on how this "trumpet protect" thing works I may revise my HP filtering later but I think I'm OK for now.

-Dan
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Why do I need cymbal overheads? I'll just use SM58s on the vocals.

Dan Brandesky

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Re: Electro-Voice 848 CDP Horns, remember these?
« Reply #21 on: May 07, 2010, 12:40:04 am »

Another update, and more questions...

I received the University Sound 1808-60 amp and it works great, the trumpet protect circuit seems to be the right low cut for these horns so I'll use that in lieu of my simple capacitor filters. I also found a spare 1828T driver on ebay for $40 so I picked that up as well. I took the transformer out when I got it since I don't plan on using these on 70V.

Now that I finally have 2 drivers and 2 horns, I got to do some playing around today, and discovered something interesting: it seems that there were two different drivers used in the 848 horns. The original driver appears under the "Drivers" section of the EV archives site as the "848HF". The EDS actually appears to be talking about the characteristics of both the driver and the horn at the same time, and doesn't give any specifics of the driver itself, but from visual inspection I can see that the 848HF has a larger diaphragm, and slightly different construction. Overall it is swappable with the 1828, as the threading and general mounting are all the same.

The really interesting thing is the audible difference, though. To my ears, the 848HF sounds more pleasant, at least with music playing. It has a little bit more midrange and less of the harsh upper mids that are typical of horn drivers, but it does have less high frequency response than the 1828. The 848HF also has more bass response (I know, bass response in a horn is kind of silly sounding, but it really does!). It really makes the 1828 in the 848 horn sound like a reentrant horn by comparison. The frequency plot listed on the 848HF is also markedly different than that of the 848A data sheet in the archives (under Horns, not drivers). Ideally I'd love to have a pair of the 848HF drivers, but it doesn't look like I can get replacement parts for them anyway, so it looks like I will need to get my other 1828 driver working so I have matching drivers in these horns. Still working on getting that stupid diaphragm washer I need. Darn $2 parts!

-Dan
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Why do I need cymbal overheads? I'll just use SM58s on the vocals.

Dan Brandesky

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Re: Electro-Voice 848 CDP Horns, remember these?
« Reply #22 on: May 07, 2010, 12:41:49 am »

Also, another thought I had that I wanted to ask the gurus here: do you all typically use any additional equalization on horn systems, or do you generally just run them "as-is"? I was thinking of hooking up a graphic EQ with the horns some time to see if I could make them sound a bit flatter, but I imagine that can quickly cut into the efficiency of the horn so it's probably a pretty fine line.

-Dan
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Why do I need cymbal overheads? I'll just use SM58s on the vocals.

Tim Padrick

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Re: Electro-Voice 848 CDP Horns, remember these?
« Reply #23 on: May 07, 2010, 10:15:05 am »

Try Madisound for those capacitors.

Art Welter

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Re: Electro-Voice 848 CDP Horns, remember these?
« Reply #24 on: May 07, 2010, 02:29:18 pm »

Dan Brandesky wrote on Thu, 06 May 2010 22:41

Also, another thought I had that I wanted to ask the gurus here: do you all typically use any additional equalization on horn systems, or do you generally just run them "as-is"? I was thinking of hooking up a graphic EQ with the horns some time to see if I could make them sound a bit flatter, but I imagine that can quickly cut into the efficiency of the horn so it's probably a pretty fine line.

-Dan

EQ has nothing to do with efficiency.
EQ in moderation can compensate for the frequency response of the horn /driver.

Attempting to EQ in top and bottom frequencies that the horn is lacking can use up your available amp headroom and cook the voice coil.

Why haven't you simply made those shims you need out of card stock or thin plastic?
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Dan Brandesky

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Re: Electro-Voice 848 CDP Horns, remember these?
« Reply #25 on: May 07, 2010, 03:39:14 pm »

I haven't made the "shims" because I would have to cut out a donut-shaped piece out of the material, and I would want to find a material that wouldn't compress (like cardboard) or get brittle (like cork), so I really think my best bet would be to get the correct part.

-Dan
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Why do I need cymbal overheads? I'll just use SM58s on the vocals.

Art Welter

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Re: Electro-Voice 848 CDP Horns, remember these?
« Reply #26 on: May 08, 2010, 02:26:52 pm »

Dan Brandesky wrote on Fri, 07 May 2010 13:39

I haven't made the "shims" because I would have to cut out a donut-shaped piece out of the material, and I would want to find a material that wouldn't compress (like cardboard) or get brittle (like cork), so I really think my best bet would be to get the correct part.

-Dan

Card stock won't compress at the torque you would use for a diaphragm. You would strip the screws before compressing plastic.

Draw the circles with a compass, cut out with a sharp knife, takes about a minute per shim.
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Dan Brandesky

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Re: Electro-Voice 848 CDP Horns, remember these?
« Reply #27 on: May 08, 2010, 06:13:57 pm »

Good to know! I might have to try that once I find the right combination of cardstocks to get the right height.

-Dan
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Why do I need cymbal overheads? I'll just use SM58s on the vocals.

Dan Brandesky

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Re: Electro-Voice 848 CDP Horns, remember these?
« Reply #28 on: October 18, 2010, 09:36:32 pm »

I'm resurrecting this thread for an update, and another question. I finally got the second 1828 driver reassembled with the correct shim and everything, and both drivers sound fine. Interestingly enough, it really didn't need any alignment as far as I can tell; the assembly fits together very snugly as it is so it didn't seem to have any leeway to get misaligned.

Anyway, I put both drivers back in the horns, and noticed the two horns sounded somewhat different. Before, I thought it was because one of my drivers was a modern 1828, while the other was the older 828, which had a larger diaphragm. However, now I have identical 1828 drivers in both horns, and the older horn still sounds different; it seems to have a little bit more in the low to low-mid range. I can only guess one of two things: either the newer horn has something odd in the tube leading to the back of the larger part of the horn, or there's some difference in material between the two horns that causes a tonal difference. The older horn is made of a more grey fiberglass, while the newer one is more tan, but other than that they look to be the same. However, looks can be deceiving...

Anyone have thoughts here? I swear I'm not crazy this time...

-Dan
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Why do I need cymbal overheads? I'll just use SM58s on the vocals.

Kristian Johnsen

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Re: Electro-Voice 848 CDP Horns, remember these?
« Reply #29 on: October 19, 2010, 03:55:36 am »

Dan.

I have no experience with the exact horns you are using, but I have experience reworking old "finds" like this and made the rather interesting experience that the horns sound different based on how far into the magnet gap the voice coils are located.  I read something about new shims further up in the thread?  What happened to me was that I got the shim/gasket thickness wrong at first and had to experiement with several ones to get the voice coil just far enough into the gap.
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