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[Peter Morris]

I got slightly higher frequencies - probably different interpretation of the cabinet. Seems to me like it wouldn't keep up with modern subwoofers if deep bass is required. Given the weight and size of those boxes, I'd take a decent 2x18" ported box every time.

Chris

Initially I got slightly higher frequencies, but then I found a spec that said it had a flare rate of 44Hz, so I adjusted my guess to have a 44Hz flare rate - it went a bit lower and matched EAW specs a bit better.  These boxes are extremely efficency, around 107 dB w/m, and with 4 boxes its more like 112 dB/w/m

[Tim Hite]

why not call EAW ?   I had an early set of the bent horn 18's from them in the early 80's.  They were RCF loaded.   Which RCF I couldn't tell you...

You would likely be better off calling over to VUE Audiotechnik and asking Ken Berger about the old boxes. EAW doesn't really like to deal with legacy gear, in my experience.

[Sam Saponaro Jr]

I don't think you will find a driver to match that, but you should be able to find a driver to work in that box.

Make a model of the horn in HornResp and test some drivers - You just need the fold/box dimensions - EAW says it has a flare rate of 44Hz (I assumed exponential 1500mm long - just a guess)

When I did that with a VERY ROUGH GUESS it looked like a B&C 18RBX100 or 18PZB100 would work and match the frequency response of the L18- 851  - with the 18PZB100 being the loudest, and the RBX having slightly less Xmax issues ... the original 851 seems to run out of Xmax easily.

FWIW a block of 4 Sim-ed to be -3dB at 43Hz ... one box about -3dB at 58 - 59 Hz

Peter Morris, Yea B&C recomended the 18pzb100 as a replacement for the RCF driver in an email to them and the 18rbx100 was one of the ones I thought woulda been a good match based on spec sheet. So maybe we are onto something.
They also recomended the 18ps100
 
Tim Hite, I will try them. I emailed EAW but no response yet.

Yea the BH800 has a 44Hz flare rate...prolly shoulda mentioned that. They don't go as low as 2x18 front loaders but there is something about the kick drum sound they do that I like,its got a cool punch to it.

[Uwe Riemer2]

Peter Morris, Yea B&C recomended the 18pzb100 as a replacement for the RCF driver in an email to them and the 18rbx100 was one of the ones I thought woulda been a good match based on spec sheet. So maybe we are onto something.
They also recomended the 18ps100
 
Tim Hite, I will try them. I emailed EAW but no response yet.

Yea the BH800 has a 44Hz flare rate...prolly shoulda mentioned that. They don't go as low as 2x18 front loaders but there is something about the kick drum sound they do that I like,its got a cool punch to it.

Completely agree about the kickdrum sound.
 
If you are using DSP and enough amp power, you could go brute force and use a driver with more excursion capability,
something like 18TBW100, if it fits in the rear chamber.
EQ to taste and limit of driver/amp.
The low end of a too small horn is governed by lambda/4 resonance and then closed box behavior, the only way to get out more low end is more displacement.
The 18TBW100 has almost triple Xmax compared to the 18/851.

Correct or similar TSP only make sense, if you are using the correct number of stacked horns.

[Sam Saponaro Jr]

Completely agree about the kickdrum sound.
 
If you are using DSP and enough amp power, you could go brute force and use a driver with more excursion capability,
something like 18TBW100, if it fits in the rear chamber.
EQ to taste and limit of driver/amp.
The low end of a too small horn is governed by lambda/4 resonance and then closed box behavior, the only way to get out more low end is more displacement.
The 18TBW100 has almost triple Xmax compared to the 18/851.

Correct or similar TSP only make sense, if you are using the correct number of stacked horns.

Makes sense,but what I worry about is lossing the "Bup" kick beater thud sound they have in the not so low/lows in exchange for more meat in the low/lows,which below 44Hz would only be off the cone anyways,to my understanding.
And if I start cramming too much air through the horn throat it may introduce/increase distortion also.Correct??
If I had drivers to try I'd try um,but trying to make a one off purchase it may be safe to stick close to the original design as much as possible.While i could make um better...I could make um worse is my fear.

[Uwe Riemer2]

Makes sense,but what I worry about is lossing the "Bup" kick beater thud sound they have in the not so low/lows in exchange for more meat in the low/lows,which below 44Hz would only be off the cone anyways,to my understanding.
And if I start cramming too much air through the horn throat it may introduce/increase distortion also.Correct??
If I had drivers to try I'd try um,but trying to make a one off purchase it may be safe to stick close to the original design as much as possible.While i could make um better...I could make um worse is my fear.

There are always a lot of ifs and thens, the more I learn the more of these.
The only way to find out is trying.
The real fun in DIY starts  as soon as you can afford to invest a couple of dollars.
Another funny thing: If you had brought up this topic 3 months ago, I would have had two 18/851 in pretty good condition for you, but these are already gone now.

[Peter Morris]

Makes sense,but what I worry about is lossing the "Bup" kick beater thud sound they have in the not so low/lows in exchange for more meat in the low/lows,which below 44Hz would only be off the cone anyways,to my understanding.
And if I start cramming too much air through the horn throat it may introduce/increase distortion also.Correct??
If I had drivers to try I'd try um,but trying to make a one off purchase it may be safe to stick close to the original design as much as possible.While i could make um better...I could make um worse is my fear.

I think all of these drivers will work, the 18pzb100 from my sim looks like it will match the 851 response the closest and the18RBX100 is not much different.  The 18TBW100 that Uwe mentioned has the highest Xmax and power but slightly less efficiency around 200Hz (-2.5dB) ... but these are VERY ROUGH.

[Sam Saponaro Jr]

There are always a lot of ifs and thens, the more I learn the more of these.
The only way to find out is trying.
The real fun in DIY starts  as soon as you can afford to invest a couple of dollars.
Another funny thing: If you had brought up this topic 3 months ago, I would have had two 18/851 in pretty good condition for you, but these are already gone now.

Ah man that sucks Oh well whatcha gonna do Id have bought um too.
Yea as of right now I cant invest a ton in driver swaps to try,I'm going through allot of upgrades to my setup and need to funnel my limited funds in multiple directions. Maybe down the road but hoping I can get um right the first time around and move on to other projects.

[Sam Saponaro Jr]

I think all of these drivers will work, the 18pzb100 from my sim looks like it will match the 851 response the closest and the18RBX100 is not much different.  The 18TBW100 that Uwe mentioned has the highest Xmax and power but slightly less efficiency around 200Hz (-2.5dB) ... but these are VERY ROUGH.

Ah and being as I'd be crossing onto MH102s in the 200-250Hz range that could make a dip in the system response. Allthough I plan to add 100-250Hz bins in later on. Did the TBW have much different curve besides the 200Hz dip from the PZB? Was it -3db at a lower freq than the PZB was?

[Peter Morris]

Ah and being as I'd be crossing onto MH102s in the 200-250Hz range that could make a dip in the system response. Allthough I plan to add 100-250Hz bins in later on. Did the TBW have much different curve besides the 200Hz dip from the PZB? Was it -3db at a lower freq than the PZB was?

This is what the responses looke like with my SIM .... this may not be the response you get (it was just a guess on the box design) but I suspect it may still be useful for comparison

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