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two leslies Mashup project finished.


WynnD

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It's a one-way trip if I do. Would like some thoughts from others on this. I have an 825, no horn rotor, and an 860, known for a very weak bottom end. Pretty sure the reason the 860 has no grunt is the very small size of the bass portion. The 825 doesn't have that problem and they both look to have the same drivers. (Should verify that.) So slice off the very top of the 825 and remove the bottom of the 860, accounting for the sloped horn mount. Put them together so the volume of the 825's cabinet remains the same, recover the tolex and it should look like a shrunken 760. (I have one of those too.) I'd use the 860's amps and controls. The results would be a shorter, narrower leslie that sounds good. (And the 825 is due for a recover job anyway.) I got the 860 fairly cheap and it did need a small amount of TLC. (Damaged 11 pin plug that made removing the cable a PITA. Also, my organ is a Roland VK-77 with an 11 pin leslie connector.

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Let's see. If I sell the 860 and 825, I might get $600. Not enough to purchase the leslie I want. And definitely not enough to purchase a 125 watt bi-amped Leslie smaller and louder than a 145. Admittedly I do own a 2014 Sienna van and can haul either one. (Though I still think the 760 won't fit in upright. the blended 825/860 might.) I frequently need to provide PA too. If I really wanted to buy a brand new Leslie? Naw, I'm too cheap for that. I've had the 825 since 1971 and the 760 since 1980 and I got the 860 for about $300. (Plus the fake internal rotary sound on the Roland is pretty good.) I'm leaning towards the blended cabinet. If I do this, I'll be taking lots of photos to document it. I've built a bass guitar. (All the woodwork is mine, including the neck. It's the one in my avatar.) Modified almost every bass I've ever owned. I do most of my own repairs. I've got the tools needed and it seems well within my skill set. Will probably make the final decision this week.

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I definitely "would not" attempt to combine them. The prices on Leslies are through the roof and you'd essentially be throwing one in the trash to make one good one (even if it worked).

 

You can buy all kinds of spare parts for them. If ones missing something or lacking something I'd definitely look at modding one up vs cannibalizing one.

 

If one lacks balls its either the amp or driver. Both can be repaired or replaced. New tubes in the amp and have the amp serviced would be an important item. Many have a gain pot somewhere on the chassis too. It may be turned down for a clean sound or maybe the input impedance can be tweaked to give you a hotter input sound. There are probably many devices you can use between the keyboard and amp to EQ and gain the head up too.

 

Of course this all depends on what kind of shape the woofer is in. The original speakers in some of those cabs are not the best by todays standards. If the cab is old it may be an original Jensen or Utah speaker and the speaker cone may be rotting. It would be an easy task to find a good replacement that's highly efficient and easily double the volume from the originals.

 

If the horns are working, I'd leave them alone. No sense messing with something that's working well unless you have too. The horns are likely mid drivers and are a key element in making those cabs sound great. Even stationary keyboard cabs can be greatly improved by adding a good mid horn and proper crossover.

 

There are several sites that have all kinds of parts available for them depending on the cab model. EBay often has parts available too.

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All of my Leslies work just as intended. The 825 isn't loved because of it's lack of a horn. The 860 isn't loved because of it's lack of bottom end. I've used the 825 in small clubs and in low volume bands, but then I don't really have a problem with that leslie. It clearly a different sound then my 760. (And the 12" drivers in both 8xx cabinets are the OEM Jensens. 4 inch voice coil, cast frame. Very good speakers.) I'm leaning towards a mind meld of them. It will leave me with a bottom rotor and motor, speaker, and 70 watt amp. I've seen 825s used in music stores for about $300 with a combo II preamp. (The Combo II is really a poorly built unit.) There really isn't much love for either of these units and used together just stacked, they are taller than my 760. I like the idea of smaller and slightly more powerful. (Good club level for any band I'd want to play with. And I refuse to bring them if the sound guy insists on mic'ing them.) Thanks for your input. I really think I'd be making more out of the blend than I currently have. (Note, I'm not even thinking about touching the 760. I like it just the way it is.)

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I couldn't find many of the 825'a out there. I read they were originally made for guitar players which makes sense because of the lack of a horn. They would up being a budget alternative for a keyboard player and were replaced by 820's.

 

I couldn't find many being sold on line. maybe because they are a heavy item best sold locally but even with heavy guitar and PA gear, you find local listings. The few places I did find selling them were getting between $500 and $700.

http://philadelphia-pa.americanlisted.com/19111/music-instruments/leslie-825-cabinet-wleslie-speaker-control-pedal-9-pin-cable-600_26902749.html If you ever do sell it, market it to guitarists. Its an ideal cab for them and you'd get top dollar, and at least the list price they sold for new.

 

Many of the original Jensen speakers had good tone but their SPL was lame at best. They were all over the place on loudness because the really didn't have much competition in their price range and is you told people about SPL back then they'd say "What the Heck is that" Compared to the newer speakers available today the Jensen's were low output. Many were lucky to have an SPL in the upper 80's or lower 90's. I had a cab back in the 70's with a pair of Jensen's and a pair of Altecs. The Altecs were at least double the perceived volume and I'd guess they had an SPL 15db higher then the Jensens. That's like doubling the wattage of the amp or more to achieve the same results

 

 

A high SPL speaker can easily boost the bass volume you're getting. It would be the first thing I'd try before anything else. A speaker with and SPL of 100~110db would blow the doors off that Jensen and with the right frequency response curve make your keyboards sound allot better too. Wouldn't cost you all much either if you know what you're looking for. There are great deals available every day for good high quality speaker used.

 

Choosing the right one would be important. You need to know what the crossover point between the horn and woofer is then compare the older Jensen response curve to what you're looking for. You wouldn't want a speaker that over emphasizes any frequencies. Keyboards can produce very low notes on the bass end and you'd want them as strong as your upper lows. I'd think a speaker designed for PA or Bass would do better on the lows then a guitar speaker which would roll off at around 100hz. The cab has allot to do with the bass resonance too. Jensen's have a resonant frequency of around 100HZ. Notes below that are going to sound weaker then notes above it.

 

It sounds like you have your mind made up though. If you do swap things around, just be sure you can swap things back if you don't get the results you expect. I'd likely set thing up temporarily before cutting and mounting stuff and test things for a week and evaluate it. The Newness of the change can easily be perceived as being better and sleeping on it for a few days, trying it again when the newness has worn off can reveal whether the actual results are better or not.

 

The thing with specialized cabs is the components are "Tuned" to the cabs. When you swap amps or speakers you can easily find the speakers fart out or have weird resonant peaks with a change in air volume. The 760 looks to be twice the size and anything used in the 825 was designed to drive a smaller air chamber. The speaker in the 825 doesn't have a crossover and likely provides a full range frequency response (probably up to about 6K) which is why it sounds louder. The 760 likely has a crossover somewhere between 2~4Khz and the horn produces those frequencies. You'll just have to try it and see what happens. I'm a bit skeptical on the results being better in any way but you'll have to decide for yourself.

 

Be careful and Good Luck.

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I was looking for a serious reason to not do it. Haven't seen one yet. I have to admit that I have a history of modifying equipment and this would just continue that. Note that I haven't considered any changes to my 760. (And that is a Leslie that gets some love from most. Me included.)

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I dunno. You've already got a Leslie you like, so why ruin two you don't like making them effectively worthless? Sell 'em and buy some nicer gear.

 

Sounds like you want to do it more for the fun of it than anything else, which is fine. But not sure what "serious reason not to do it" anyone would have been able to offer you. Outside of loss of money and probably won't sound as good as you hope, what else could someone else have told you? Don't do it because they'll blow up?

 

 

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Already know what they sound like together. The bass speaker in the 860 isn't worth much in that cabinet. I've got about $700 total invested in the two and used the 825 for quite a few years prior to 1980 when I got the Hammond X5 and 760 Leslie. Turns out that the 760 and 825 are both viable leslies for the X-5. (9 pin pre-amp built in organ's pedalboard.) I really like the idea of a smaller leslie that I can plug right into my VK-77 Roland organ. (11 pin.) I have a 1197 adapter kit for connecting the 760 and 825 to the organ. (Gave up on fixing the combo preamp II again. That is such a crap circuit board.) 760s are running from $800-$1400 used. You're right. At this point, I've pretty much decided to put them together. Only thing I'm losing is the non-horn 825 leslie. The 860 is fuctionally getting an enlarged bass cabinet with casters. Sounding like a win to me. the two hard issues will be how to blend the removable back panel and where to mount the handles. (My 825 didn't have side handles ever.) The resultant cabinet will need new tolex, but the 825's is pretty beat up anyway. Got a plunge router for the handles and to cut a groove to make the glue bond better.

 

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The serious consideration you have to deal with is the speaker cavity dimensions. If you're changing the cavity size the cab will no longer be tuned and it can shoot your bass response all to hell. Cabs are designed to have the correct air mass for the driver to produce a flat bass response. If you increase of decrease that air volume without using a calculator to figure your dimensions the speaker can easily be out of phase with the air its moving. This can lead to rogue resonant peaks and dead notes that just sound awful.

 

You may get lucky and just happen to get it right. Many guitar cabs were built based on ascetics, not science, but guitar cabs push only midrange and you can tweak the tone stack circuitry of the head to overcome its shortcomings.

 

Bass cabs, PA cabs, Hi Fi, and Keyboard like those leslies are a different story. If you want a linear output with the wide range of frequencies they produce you have to crack the calculator out and make the air volume calculations based on the drivers being used or you can wind up with a piece of junk. Believe me I spent a good 40 years building plenty of cabs and it wasn't till I was getting my electronics degree I understood why the cabs I built sucked for tone.

 

Luckily the ability to do the computations have never been easier. The internet has provided the speaker specifications and on like specialized calculators needed to find the exact cab dimensions you need.

 

I highly advise you use them before you just start ripping the cabs apart. I'd make the calculations first to see if its even possible,

 

There's dozens of calculators like this one. http://www.diyaudioandvideo.com/Calc...rBoxEnclosure/

 

You need to find the speaker specifications and plug them into the calculator. The results will vive you the exact air volume needed for the speaker to produce the correct fidelity and maximum efficiency. Since "Bass Growl" is your objective, its essential you use the correct dimensions or you can forget about getting that.

 

I used the specs from a New Jensen speaker here: https://www.jensentone.com/vintage_ceramic/c12k

And keyed the values into the calculator here: http://www.diyaudioandvideo.com/Calc...rBoxEnclosure/

Then selected a sealed box for the dimensions and got these dimensions.

 

Sealed Box

 

Vas = 27.6 ft3

fs = 104 Hz

Qts = 0.65

Qtc = 0.707 [TABLE]

[TR]

[TD]sealedBox.gif[/TD]

[TD]Dimensions


Vb = 150.76 ft3 = 4269 lts

= L x W x H

f3 = 113.14 Hz

fb = 113.12 Hz[/TD]

[/TR]

[/TABLE]

[TABLE]

[TR]

[TD]Vb: Speaker Box Internal Volume

f3: 3dB Cutoff Frequency

fb: Enclosure Resonant Frequency

 

If you make the cab larger of smaller its going to cause bad things to happen.

 

The only thing it doesn't factor in is the drum cavity resonance and additional porting in the cab which can change the speaker response. It may not be a factor so long as the back side of the speaker has the right amount of air volume. I'm sure Leslie uses some kind of calculations to factor those additional parameters. I'd have to dig deep to find that and it may not even be a factor.

 

The air volume for that 100W Jensen is 150.75. You have to use some additional math or a different calculator to figure the Length, width and height dimensions of the cavity. This will let you determine if the final cab dimensions will produce the proper sound.[/TD]

[/TR]

[/TABLE]

Like I said, you just go ripping the two up, chances of you getting it right isn't going to happen. A cab can have drastic bass issues with only a few inch changes in height or width that can make the results.

 

Here's another cab calculator. http://www.mh-audio.nl/ClosedBoxCalculator.asp

 

I keyed in the info and got the dimensions of : 53.22W X 86.12H X 32.89L

 

I found the response curve using another calculator.

 

closedBoxFrequency.php?Fb=92.29&Qtc=0.577&gSize=1

 

If I change the cab Air Volume This curve can change "allot"

 

 

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Very good points. My plan was to leave the bottom cabinet volume exactly the same as prior to the modification. Cutting the 825 cabinet at the bottom of the top plywood panel. Then cutting the 860 around 1/2 way up the bottom of the horn mount sheet of plywood. That sheet is mounted in the 860 at an angle so the horn didn't make the cabinet deeper front to back. (Horn size is the same as normal leslies.) This should leave the 825's volume the same as before even though the top will be sloped. I know enough about speaker cabinet design to not want to change or redesign the bass portion. That's probably the reason the 860 lacks a bottom end grunt. (The biggest reason for this mod.) Now I'm assuming that I can't find the edging new, so I'll have to remove that prior to the work. (It's only held in by friction and staples on the bottom of the cabinet.) I plan to recover the modified cabinet, so I need to get some new tolex or something similar. And I had already changed the 825's grill cloth and while it's very similar to the original, it doesn't quite match the original that's on the 860. I'm also not sure if the 825 and 860 have similar rotor speeds on the 12" speaker. Might have to move the 860's rotor motor parts to the 825. (Need to do some research on that.) the two cabinets motors adjust differently so I'm hoping to not have to do that. (Might have to get into more woodworking if I need to change the motor.) I'm already aware the installation differences between the power supply/ motor controller. (860 is totally functional and better for production. Single screw holds it in place.) I will need to build a new back for it. (Probably just put the two backs together after adjusting for the shorter height. May have to drill a few new holes for screw access.)

 

If you have some more ideas, I'd love to hear them.

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One other thing about the 825. It's not a sealed cabinet. It's a bass reflex with two ports but no tubes. The ports are actually just corner cuts in the speaker mounting plywood on the left bottom (Looking at it from the front.) There is sound absorbing material stapled to the plywood separating the speaker from the ports. Kind of a curious way to deal with internal reflections. The top of the cabinet being sloped after the modification, will probably help with reflection issues anyway. I used to have a 136 Acoustic bass combo amp. Sloped internal panels never gave that cabinet any problems. (I'm expecting the same here.) Will also be mounting strong handles to the left and right side, but won't deal with that until I've put them together and tested the results. Don't want to mount them below the center of gravity but don't want them much above that point either. (Will make it easier to load and unload with help.)

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There is also a slight possibility that the results might weigh more than my 760 even though it's smaller. (The 860 is a heavy little beast. Don't think much of that is in the bass speaker rotor motor portion.) Still expect the results to be less than 125 pounds. (the 760 is about 95 pounds.)

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If you keep the same air volume you should be good. I wasn't sure if that cab was vented of not so you can disregard those dimensions which were based on a sealed cab. I would think the drum would sound better is it was the only place for sound to escape, but leslies are a weird animal to begin with. Not having the back pressure likely adds to the bass response and speaker growl.

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I'm not adding speakers. Only changing the bass speaker from the one in the 860 to the one in the 825. (They look like identical Jensen drivers. 12", 4 inch voice coil, cast frame and crinkle black paint on the frame. I know the 825 is a 6 ohm speaker. Haven't checked out the 860's yet. If they DC test to the same resistance, I'll assume they are totally interchangeable.)

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I'm wondering if I should use a circular power saw to make the cuts or if I should use my Table saw. Got control over depth in either case. Just not sure about an 80 pound box on the table saw. I'm also a bit concerned about straight cuts with a power hand saw. I would use a 2x4 for a guide on each side cut. (Got lots of clamps to hold it in place.)

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Thought you guys might like a peek of a photoshop that shows the end result. I'd probably make the grill cloths match in width. Did some calculating and the result would be about 30% smaller by volume compared with my 760. Stacking the 860 and 825 results in a volume that's just about the same as the 760. Now I need to find a place to create some sawdust. (That's volume as in cubic feet.)

 

 

fetch?id=31661105fetch?id=31661106

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This forum doesn't process photos and I'm a bit reluctant to have to change every single picture just so I can post it on this website. Current photos of the project are on my facebook page as well as under the same moniker on the organforum.com site as well. Their website fixes pictures automatically. Current status is the rotor motors are lubed and in place. I swapped out the bass rotor motors. Fabricated a mount for the horn driver and lubed the horn. Just marked the location of the rear powersupply mount from the 860. (bi-amped amp that will drive the FrankenLeslie.) So I'm almost ready to mount the amplifier. After that, I've got internal bracing to deal with and creating a new rear panel for the bass speaker. Will report more later.

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