View Full Version : BIG monitors
08-21-2003, 07:27 PM
As posted elsewhere, I am building big monitors on the line of 4350/5's, but with 2245H's (18" inch), as far as the tweeters, on the thread 2404 vs 2405, the 2405 seems the best idea, I'll try both anyway.
I would like Your valued opinion on using 2311's with 2308 plastic lenses, or 2382's, I have the former, but have not found the 2382īs in cheapbay.
The speakers will be about 12', 4 meters for us metrics, away from my ears.
Tomorrow I'll go to the cabinet maker and take pics of progress. He only started 2 months ago so maybe He'll have the inside perimeter, they are being built from the inside out, bracing first.
08-21-2003, 10:11 PM
Hey alex - you bought some stuff on ebay from me awhile ago..
Instead of using the 244(X) drivers on the 2311/2308 or 2382 I would suggest the 1.5" driver 2451J with the 2332 90 degree horn.
This will take up little baffle area, have BOATLOADS less distortion, and since you already *have* 12's underneath and slots above, the horn can be real small.
It is ALMOST time aligned with the original 2311 horn...:)
Sure beats the 1/2 mile long distance from phaseplug to horn flare on the 2382....!!
08-21-2003, 10:29 PM
You meet the nicest people on the LansingH country club.
Wouldnīt the 2311/08 have more lateral coverage?, the distance is real short, I know.
08-22-2003, 07:14 AM
Well the 2311 / 2308 is supposed to be 90 or 100 wide depending on what jbl print you read and the 2332 ( used in the DMS-1 and Array series, is 90.
So it's a tossup there but given the choice, an immediate horn flare on the phase plug ( vs at least 7" of throat ) and the absence of obstructing plates makes for a less distorted/less obstructed pathway for the critical high-mid region and no "lobing" effect from the plates.
But I would do an A-B on this - perhaps the older diaphram / lens assembly has that warmth that makes the monitor so nice sounding!
BTW - you could use the 2450SL diaphram ( coated 2445 titanium ) to mimic the aluminum rolloff and REALLY smooth out the resonance peaks. This is the driver in the DMS-1 and ARRAY.
08-23-2003, 04:15 AM
I use 2332 horn with new 2430 compression driver.
08-23-2003, 05:06 PM
I've not the experience with CD's and differing throat/horn configurations that some do here in the LansingH Country Club ;) - specifically Giskard, Widget and Earl K to name but a few - but this Link: JBL L300 vs 4343 Link (http://www.audioheritage.org/vbulletin/showthread.php?s=&threadid=350&highlight=2421) will take you to an interesting discussion on the 2421 CD and its Al diaphram that is worth a read.
As well, you might try the "underused" Search button for your CD and throat/horns, and see what is unearthed.
10-09-2003, 04:59 PM
3 images of the project, which by now should be called "decade", that's how long itīs taking.
First we built the bracing out of 40mm pine, it now has more than the pics show, and You can barely make out the cutouts glued and screwed to the rear side of the 18" cabinets, then the sides built from 1/8" plywood glued to 1/2" thick slats, glued and screwed from the inside out, so as not to bother covering the screw heads.
The corners are solid wood, and everything was clamped while the glue dried.
I put holes for binding posts for each driver; the x-overs will be on the outside; I have 3pr of 3107īs, so I can fool around using them: as they come, caps bypassed, and charge coupled; I also have electronic ones, so I can really complicate my life.
I will post more pics later.
10-09-2003, 05:02 PM
10-09-2003, 05:03 PM
10-09-2003, 05:19 PM
Looks nice Alex !
regards <. Earl K :)
10-09-2003, 05:26 PM
Wow, you've got a good looking project there. It's clear you're committed to puting together a very nice set of speakers!
Though I suspect that the previous posters may be correct that the new horns are cleaner, I've found that the classic JBL round horns, like the 2312 and 2307s, when loaded with the 2420s and fitted with the 2308 slant lenses, sound great! I find the dispersion quite wide and even and don't have any problem listening to them for extended periods. Aparently JBL liked them too, because they used them on numerous studio monitors for quite some time. They were standard on their most expensive Pro studio monitors...so I don't think you'd go too wrong if you chose to use these.
I think I'd use the "Dolly Partons", before I'd go to the CD horns in a home listening or small studio situation.
Just my opinion.
10-09-2003, 07:49 PM
WOW!! :shock: I'm thrilled with what (I think...) you're doing. Twin 2245H's each side? What are you, nuts!?? :nutz: Or, is that a single "center" ULF section...?
Interesting linear array of the "high-end", and your deciding to put the 2405 atop the 2445, rather than side-by-side. What was the decision tree for that?
The wood grain looks like it will finish gorgeous. Any money in the budget for a roadtrip by Audiobeer? :rotfl:
10-09-2003, 08:24 PM
Youīre thrilled (You think that I think I know what Iīm doing, the shadow knows)
Total per side:
2 2245H's, separate 280 liter enclosure each 20-200Hz (letīs see)
1 2202H 35 liter enc. 200-1100Hz
1 2445J, 2311, 2308 I'll try 2446 and 2451? diaphs. 1.1-9 KHz
1 2405H 9^^kHz
1 channel of Crown K2 for 2 2245H's
1 Sony N77ES bridged one side and 1 N80ES, the other, they are almost identical.
X-overs 5234īs, M553, whatever sounds best. Iīll need Your help later.
3107īs as described before.
Nuts??, of course.
Since the smaller cabinet is aimable, I guesstimated the vertical array would give me better position, at the expense of being too "focal" Weīll see, The 2245īs cabinets will not be very "aimable", I have enough friends though; From previous advice from these revered pages, I can put the ports up or down, (more sixpacks, or cases of Tequila or both).
The finish will only be prepped linseed oil, no lacquer, but already coated inside with Pentaclorophenol, great for debugging, kind of Hazmat.
I donīt think I can afford Audiobeerīs work, He should be making Paragons, and ship them west, so they'll get east.
All ideas very welcome.
I second the recommendation for the JBL 2430 Aluminum compression driver. This is about as close as you will probably get to the driver used in the new K2 speakers and it is supposed to be one of the lowest distortion compression drivers that JBL has ever built. The 2430 is available for around $220 and I saw that the 2332 is available for $68. Just a diaphragm for a 2445 or 2441 costs almost as much as the complete 2430 driver.
I'm thinking about a similar 4355 project with a pair of 2235H, a 2020H, and a BMS 4590 coaxial compression driver. I have a pair of 2380 horn but I may go with a smaller horn. One of my 2020H was damaged in shipping so I'm waiting for a UPS check.
10-10-2003, 07:36 AM
I already have all of the stuff, including the diaphs., I also have NIB TOA 2" throat, 2.8" VC drivers, they will be tried, at the risk of being defrocked here; I can get as loaners Altec 288īs and 511 horns, but I do not like the idea.
If I run into 2430 and 2332's, like on cheapbay, I'll get them.
10-10-2003, 08:47 AM
Originally posted by Alex Lancaster
Since the smaller cabinet is aimable, I guesstimated the vertical array would give me better position, at the expense of being too "focal" Weīll see, The 2245īs cabinets will not be very " aimable.
"Aimable" is a smart idea - that will give great flexibility in room placement. Nice. :thmbsup: And, the 2245H's aren't very directional, so this will be a great design. How high with the 2405's be off the floor?
The finish will only be prepped linseed oil, no lacquer, but already coated inside with Pentaclorophenol, great for debugging, kind of Hazmat. I donīt think I can afford Audiobeerīs work... You might hit him-up for a holiday visit - he's favorably inclined to road trips! :scoot: :smthsail: :scoot:
10-10-2003, 09:43 AM
The center of the 2405īs, will be about 42" from the floor, adjustable with encyclopaedia tomes.
For the next project I will contact Audiobeer.
I forgot to mention, that in preparation for this, I put in direct #4AWG cables, from the mains, which the power co. thoughtfully had provided with #2AWG, so I have a direct circuit with a 50 Amp breaker; We (my index finger and the electrician), sank a 10' copperweld rod in the garden for the physical ground.
10-14-2003, 05:49 PM
I don't want to be the rain on your parade,but you would really,really benefit from cross braces running from side to side,top to bottom and front to back.(even doubling the wall thickness)of the speaker chambers. ESPECIALLY if you are going to run big horsepower to those 18's. Getting rid of cabinet resonance is huge to insure really tight, accurate low end. If you feel the cabinet vibrating when you are playing program material,that is energy wasted that you would rather want to be traveling foreward off of the cone. Also, think of it as the cabinet vibrating is acting as a transducer,cancelling out some of what the speaker is trying to produce..it is especially noticeable at lower frequencies.
10-14-2003, 08:15 PM
An example of some factory JBL bracing................
10-14-2003, 08:45 PM
Agree 1000% with Tim R, re: bracing.
The good thing is, that it is pretty easy to add cross-bracing at any stage... just take some 2x2 wood stock, cut it for a relatively tight fit across the span in question, and use something like 5-minute epoxy on the mating surfaces of the brace ends and the cabinet walls, to bond it to the walls. No screws required, IME. Works like a champ.
It's amazing what careful bracing will do for even totally s#!^^y cabinet construction, IME. I've braced up some pre-fab RCA rack-system and Pioneer cheap speakers, and was just amazed how strong you could make a cabinet, even one that was hot-melt glued together in some offshore mass-production line! With a GOOD cabinet, like the one Alex is building, it'll make it like almost utterly bullet-proof, if he braces it right! Heck, with the right braces, you could probably drop it off of a building, and dent the concrete! :D :D :D
10-15-2003, 01:44 AM
Something tells me that the vents for the 2245īs are way to small...
10-15-2003, 05:52 AM
Good point Niklas, one would definitely hear those chug.
I usually use dual 6" ID ports for the 2242 and 2245.
10-15-2003, 06:19 AM
Yes, or ONE 10" vent.
Those small vents may sound bad, one would hear the
air moving in and out the vent ..
I like Neriks vents, they are big, and if played loud the
black foam blows out on the floor.. itīs not glued..
Can you see the black foam in the vents..
important to have big vents indeed
if using two big 18" drivers.. (2242)
10-15-2003, 07:35 AM
As I said, since the pics, more bracing has been added, 40mm sq., x-y-z about the center, more or less.
About the vents; as You can see, they are very short 2", 4" dia. PVC pipe; I did not want to weaken the baffle board, If I hear any blowing, out comes the router and hole saw.
I wonīt use foam, I like the holes to spray bug killer every so often.
Pls keep Your opinions coming, Thanks.
10-15-2003, 08:21 AM
Originally posted by Tim Rinkerman
If you feel the cabinet vibrating when you are playing program material,that is energy wasted... That quote just slayed me! This weekend, testing those DIY modified L65's I'm working on, I got pretty thrilled with the LF response (finally!!) and had the cabinet up maybe to 90db. Well, sitting on those new wooden floors, the cabinet began a slow left-hand rotation, all by itself. Definately clockwise - sorta a Coriolis affect. I laughed really hard when I realized if Ian was doing at this, it would be rotating anti-clockwise in his hemisphere... :rotfl:
Definately need some of those cabinet - floor spikes... :yes:
10-15-2003, 08:32 AM
:rotfl: "and if played loud the black foam blows out on the floor"
Those little bonuses make life such a joy :)
10-15-2003, 11:50 AM
Yeah Cool Bo,
Last time I did that everything in the apartment moved about 90 degress anti clockwise at about minus 10 dba @ FB with the 2245's on the 700B.
The vibration likened itself to Pink Floyd "Welcome To the Machine..."
"the vent noise was a sorta shuddering gyration, like the sound of a whale humping...drove all the woman in the building bonkas"...muhahhahahaha.
Later realised all the mechanical Clocks stopped right on 12.00 Pm, it was like a "Warp Worm" on Star Trek.
Thank God for kitty Litter.
Unibox is a freeware program that you can use to model different size boxes, ports and drivers and it has a great feature that allows you to model air speed for different size ports at different power levels. This way you can determine how big of a port you need to reduce turbulence depending on how much power you are going to provide for your subwoofers. Here is the link for the download. http://www.danbbs.dk/~ko/ubdwnld.htm
After playing around a little bit, the program recommends a minimum port diameter of 12.56cm (5 inches), for a single port, to keep air speed below 5% of the speed of sound, down to 20Hz with 300watts of input, with 25Hz tuning. There is probably a way for me to post a link to the excel file that shows this, but I'm not sure how to do it.
10-29-2003, 11:27 AM
Finally!, the cabinets got home, I pulled out a scale, the big ones weighed 61.5 Kg, about 135.3 lbs bare, not even fiberglass; the small ones about 22 lbs, please see pictures above.
Will post pictures later.
10-29-2003, 12:06 PM
very nice looking indeed!
I thought I was the only one who used Mortite as a sealing gasket! Good stuff.
10-29-2003, 12:58 PM
What is mortite?
10-29-2003, 01:09 PM
Mortite is the reason I live in Korea.:D
10-29-2003, 01:20 PM
You see in Niklas Nord,s picture where you see the 2242 woofer face down, and hes putting that grey putty around the backside of the speaker rim, that mounts to the cabinets baffle? That is Mortite. Its a sealing putty that comes in a roll from any hardware store, and I use that stuff instead of the cork gaskets for my 2240 loaded scoops!
Not only is it an airtight seal, but when you go to take a woofer out, you need a screwdriver to pry the woofer off! We have been using this stuff since the 70,s!
11-28-2003, 08:58 PM
Finally Iīll have some time to finish this project, some of my Audiofiend friends told me NEVER to use fiberglass, instead a 1/2" felt type material, that is used -get this- for saddles where they meet the horse, as the best; I think they ate too much of the felt, but I need Your opinions.
11-30-2003, 08:20 AM
No replies, maybe the thread gotmarked "read", with the move?
11-30-2003, 10:42 AM
Somewhere in this forums archives is a thread with a discussion about the use of different damping materials inside a cabinet. I don't think that thread ever discussed the use of felt . Some audio parts stores sell damping pads ( some soaked in a permanently viscous goop ) . These pads reportedly work well - I've never used them . The horse-blanket felt, sounds like the basis for one of these hitech pads.
If horse-blanket felt is available to you - then , try it and measure its ability to change Fb vs the more tradional 1 to 2" fiberglass AND most importantly - listen to its effects .
If I was in your place , I'd try it tightup against the cabinets walls ( maybe glue it ) with another layer of Dacron right up against the felt. Dacron ( polyester stuffing ) isn't as effective for Fb lowering as plain old fiberglass - but used in conjuction with something else ( horse-felt ), one should likely extract good performance ( with some tinkering about ).
It would be nice to find a cost effective creation, just as effective as fiberglass .
Just my best guess .
<. Earl K
11-30-2003, 11:30 AM
Since the 18" boxes are 280L each, what about 1" fiberglass, glued with silicone, and then stapled with card stock; I expect to cut them off at 200Hz, and of course try higher frequencies, I want to get as close to 20Hz as possible.
For the sealed 2202H boxes, I guess the other combinations would be worth a try, I already have boards made to try other CDīs and tweeters.
Suggestions are very welcome.
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