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slxrti
01-02-2006, 11:15 AM
Hi for the New Year I would like to build a great center channel for my home theater system. The mid bass driver (pairs) options are 2218H, M203H, 2123H or a pair of 8” morel drivers, for midrange a single 2416H and maybe a single 2404 for the ultra high freq’s. The speaker configuration could be either a MTM or MT, depending or each merit's.





Before I let the wood chips fly I have a few questions:



What sonic qualities create a great center channel?



What should the low end freq response (-3db) to shoot for?



Which mid bass would you choose (why)? And what would be your crossover freq (why)?



My current center channel (Citation) requires vertical placement for producing a narrow sound field for dialogue. Can a rectangular cabinet/MTM configuration, but horizontal placement achieve the same results?



As far as cabinet shape, rectangular is ok, but I prefer the mid bass drivers to be angle

inward. What are the liabilities with such a design? Is there a range of angles to stick to?



The horn I’m using has a very wide dispersion, what are the repercussion for center channel usage?



More question’s on the way,



Thanks, Slxrti

edgewound
01-02-2006, 11:45 AM
In a 5.1(7.1, 10.2...) all the speakers should be identical in response....so anything different will be a compromise. Other than that try to design your center channel to be as close a match as possible to your left/right channels.

Probably not the answer you wanted to hear, but that's how it's done in the movie theater.

Don Mascali
01-02-2006, 11:48 AM
I am using 2, 2123J and a 2426H on a 2342 horn in a horizontal MTM. They are crossed over at 1600 hz.

Some opinions;

What ever you use should be a match in "Timbre" (Damn I hate to say that and sound like one of them Golden Ear types) for your front speakers. Three of the same accross the front would be ideal. Even Pro installations don't use all identical on the surrounds.

I don't run mine below 80 hz because they sit almost on top of two 4546C subs. I don't feel that extreme highs or lows are that important.

They do mostly dialogue on movies. When the action pans across the screen, it is obvious where the sound changes as each speaker picks up the sound, IF they are too different in Timbre. I use a projector wih an 108" screen and this requires some continuity to make it flow smoothly.


A good system should image well enough to fill in the center in stereo mode. I use Pro Logic II 7.1 for music and the center helps. A lot of people find that heritical but it sounds good to me and that's the whole point isn't it ?

Good luck in whatever you decide,

Don M

slxrti
01-02-2006, 12:19 PM
In a 5.1(7.1, 10.2...) all the speakers should be identical in response....so anything different will be a compromise. Other than that try to design your center channel to be as close a match as possible to your left/right channels.

Probably not the answer you wanted to hear, but that's how it's done in the movie theater.

I did not consider front speaker matching. Realizing that I don't design loudspeaker for a profession, I may have to lower my expectation to a
good center channel.

Slxrti

Robh3606
01-02-2006, 12:36 PM
What are your mains??? Don't skimp on the center channel it's over 50% of your movies audio content. Match it as close as you can to your L/R. If you go horn try to keep the horns on the same plain vertically so the pan doesn't dip or go up. Try the 2342 alone and see if it works for you. If you drop a 2404 over it you will have to deal with integration issues like comb filtering. On the low end make sure your F3 is low enough so you can get through the crossover region without a drop in level caused by to high an F3. Depends on your slopes and what choices of frequencies you have in your processor.

Rob:)

slxrti
01-02-2006, 12:39 PM
I am using 2, 2123J and a 2426H on a 2342 horn in a horizontal MTM. They are crossed over at 1600 hz.

Some opinions;

What ever you use should be a match in "Timbre" (Damn I hate to say that and sound like one of them Golden Ear types) for your front speakers. Three of the same accross the front would be ideal. Even Pro installations don't use all identical on the surrounds.

I don't run mine below 80 hz because they sit almost on top of two 4546C subs. I don't feel that extreme highs or lows are that important.

They do mostly dialogue on movies. When the action pans across the screen, it is obvious where the sound changes as each speaker picks up the sound, IF they are too different in Timbre. I use a projector wih an 108" screen and this requires some continuity to make it flow smoothly.


A good system should image well enough to fill in the center in stereo mode. I use Pro Logic II 7.1 for music and the center helps. A lot of people find that heritical but it sounds good to me and that's the whole point isn't it ?

Good luck in whatever you decide,

Don M

The 2123 is one of my options, what type of enclosure did you use?
As far as shape, is the enclosures a rectangular box?

What crossover slope did you use and why did you chose 1600hz as the crossover Freq?

btw, people should be allow to make choices without
criticism especially if it impact no one else, Enjoy what you have.

slxrti
01-02-2006, 12:58 PM
What are your mains??? Don't skimp on the center channel it's over 50% of your movies audio content. Match it as close as you can to your L/R. If you go horn try to keep the horns on the same plain vertically so the pan doesn't dip or go up. Try the 2342 alone and see if it works for you. If you drop a 2404 over it you will have to deal with integration issues like comb filtering. On the low end make sure your F3 is low enough so you can get through the crossover region without a drop in level caused by to high an F3. Depends on your slopes and what choices of frequencies you have in your processor.

Rob:)

My main are 4430's, but in the future they will be replaced.

To make sure I understand matching, does this implied only to freq
response? If it does not, are there any other major design considerations?

My thought was is to allow the natural roll off of the driver to determine the low end response. The slope would be either 12 or 24 db, depending on box type. If response below 100hz is not needed, than a close box maybe appropriate.

The crossover to the horn would be handled passively, slope and crossover
Freq have yet to be determined.


slxrti

edgewound
01-02-2006, 01:25 PM
btw, people should be allow to make choices without
criticism especially if it impact no one else, Enjoy what you have.

My apologies to you for my expedient post....I wasn't intending any criticism of you or your abilties....rather, it was a quick guide on how HT systems are designed for the most pleasing theater experience in your home. You're right....you should use whatever you have available to you to complete your project. Maybe we can save you a little time and frustration by leading you down the right path for your center speaker to better integrate with what you currently have....others would rather do it their own way and learn along the way and have a never finished...or should I say " never ending".... project.

And lately, some members just want to fight....whatever....

Happy New Year to all.

slxrti
01-02-2006, 01:41 PM
My apologies to you for my expedient post....I wasn't intending any criticism of you or your abilties....rather, it was a quick guide on how HT systems are designed for the most pleasing theater experience in your home. You're right....you should use whatever you have available to you to complete your project. Maybe we can save you a little time and frustration by leading you down the right path for your center speaker to better integrate with what you currently have....others would rather do it their own way and learn along the way and have a never finished...or should I say " never ending".... project.

And lately, some members just want to fight....whatever....

Happy New Year to all.

Oh Gee, I agreed with you!!! I didn't take what you wrote personally.
I'm open to suggestions, thought's and word's of wisdom.





btw, I read several other threads before posting this, they were to personal for my taste.



Take care, Slxrti

Robh3606
01-02-2006, 02:21 PM
Hello Sxrti



I understand what you are saying about the roll off due to the box design however when you set a surround processor for a “small” center channel you have an electrical crossover that overlays the box response. If you don’t know where this is and the slope you can design in a nice hole into your system response. So at the very least you need response below where your processor does the crossover. If you can select the crossover point your fine. You don’t want the set point 20 hz below where the F3 knee on the box is. What are you replacing the 4430’s with???

Match as in driver types as well. Don't mix domes and compression drivers. I have tried it and certainly didn't work for me. You want systems that have similar frequency response, which room placement will affect anyway, and transient characteristics. Movies are all about dynamics and good deal of it is front and center in the center channel. You don't want a slacker as the main event in your HT system. A good center can make or break an HT set-up. It should also have excellent powerhandling and enough power behind it to reach THX levels where you sit and not clip the amp.

Rob:)

Don Mascali
01-02-2006, 03:44 PM
Please don't get discouraged or overwhelemed by this task. We all started somewhere and I have never heard a speaker sound better than one "I" designed. Some of them were total crap but I loved them anyway. Kind of like children. http://audioheritage.org/vbulletin/images/smilies/smile.gif

Some of the guys here think they are geniuses and some of them really are! The group here will see you through it and you will enjoy the most important part, DIY like the forum says.

Any manufacturer who can't design a good speaker with all the resources available to them won't last long. We get to have the all the joy of creation and if we miss the mark we can start over. No big deal, it will still sound better than "Worst Buy" ect.

It would help to know what you are going to change to. As for the 4430s match, Zilch has a thread bigger thn "War and Peace" with tons of options. Start reading that and you will think of something. The drivers you mentioned are all a good start.


Remember, "It's a Journey, Not a Destination", enjoy the ride.

slxrti
01-02-2006, 05:02 PM
Hello Sxrti



I understand what you are saying about the roll off due to the box design however when you set a surround processor for a “small” center channel you have an electrical crossover that overlays the box response. If you don’t know where this is and the slope you can design in a nice hole into your system response. So at the very least you need response below where your processor does the crossover. If you can select the crossover point your fine. You don’t want the set point 20 hz below where the F3 knee on the box is. What are you replacing the 4430’s with???

Match as in driver types as well. Don't mix domes and compression drivers. I have tried it and certainly didn't work for me. You want systems that have similar frequency response, which room placement will affect anyway, and transient characteristics. Movies are all about dynamics and good deal of it is front and center in the center channel. You don't want a slacker as the main event in your HT system. A good center can make or break an HT set-up. It should also have excellent powerhandling and enough power behind it to reach THX levels where you sit and not clip the amp.

Rob:)



Hi Rob, I just checked my preamp, I have two choices. The "small" limits the low freq range to a f3 of 100hz, 18db slope. The large setting pass's full
range info to the center.

Using LSPCad I plotted the freq response of the 2123 and 2218. The response of the 2118 is down ~3db @ 120hz and the 2123 ~3db @ 170hz.

What is the freq range necessary for a center channel?




In the future I plan to replace the 4430's, with a 4 to 5 way system.
Subwoofer's: 1500
Lower Midbass: 2217
mid base: 2123
middle range: 375
ultra high: 2404 or 2405.

When I was younger I thought I would double up on the 2123 and 2404.
I since scale back, one of each driver should be enough!!

But, before I begin the 4/5way project I thought I should have at least one loudspeaker under my belt.

slxrti

Robh3606
01-02-2006, 09:25 PM
Well 70Hz seems to stick in my mind but obviously fullrange would be the best option. Have you looked at the 2118 spec sheet?? Run them in .5 cubic Ft tuned to 70Hz. With that tuning the knee is down but at 70hz and with room gain it may work out OK.

http://www.jblpro.com/pub/obsolete/2118.pdf

Are you stuck on these drivers??? I would look real hard at what your mains will be and use that to determine the driver set for the center channel. Do you really need 2217 and 2123??? Seem's the 2217 could cover the gap just fine between the 1500 and the 375. Don't make it any harder than you have too. Using the same drivers in the same ranges as the L/R is a good thing.

http://www.jblproservice.com/pdf/Discrete%20Sales%20Models/2217HPL.pdf


Have Fun:bouncy:

Rob:)

Ian Mackenzie
01-03-2006, 01:55 AM
slxrti,

Many people get worked up over the centre channel..I am not convinced it works all that well for music DVD's but might be impressive on Terminator 3.

Another member is considering a similar idea in progress with 4 way sides and so he is using dual 2122H for the centre with a 2307/2308 horn/Plate assembly and a 2405. The sides will be the same with single 2122H mid cones crossed over at 300. You could opt for a LE14 woofer for the centre woofer.

This is basically the mid / horn and top end of a JBL 4344..the dual 2122H should in theory have sufficient oomp down to 100 hertz or a bit lower due to its X max and heavier cone than the 2123.

The hard yards on the crossover have already been done (some modification of the centre will be required) so you would have a good proven design and don;t have to start pioneering there.

The 2235 or 2245 would round out the design for the bass in the left and right front channels and everything would match.

Done properly this system would stand the test of time and play not just movies but music very nicely!

Ian




Hi Rob, I just checked my preamp, I have two choices. The "small" limits the low freq range to a f3 of 100hz, 18db slope. The large setting pass's full
range info to the center.

Using LSPCad I plotted the freq response of the 2123 and 2218. The response of the 2118 is down ~3db @ 120hz and the 2123 ~3db @ 170hz.

What is the freq range necessary for a center channel?




In the future I plan to replace the 4430's, with a 4 to 5 way system.
Subwoofer's: 1500
Lower Midbass: 2217
mid base: 2123
middle range: 375
ultra high: 2404 or 2405.

When I was younger I thought I would double up on the 2123 and 2404.
I since scale back, one of each driver should be enough!!

But, before I begin the 4/5way project I thought I should have at least one loudspeaker under my belt.

slxrti

matsj
01-03-2006, 11:11 AM
Hello i have one 2446j 2" driver + 2382a horn and 2 2226h 15" in a horisontal MTM config. The box is 2,4 meter wide :) . Crossover is 700 and 40 hz.

2 closed chambers 140 liter each.

regards mats

Don Mascali
01-03-2006, 07:36 PM
Hello i have one 2446j 2" driver + 2382a horn and 2 2226h 15" in a horisontal MTM config. The box is 2,4 meter wide :) . Crossover is 700 and 40 hz.

2 closed chambers 140 liter each.

regards mats


Damn, thats what I call a center channel! :spchless:

slxrti
01-03-2006, 09:27 PM
Well 70Hz seems to stick in my mind but obviously fullrange would be the best option. Have you looked at the 2118 spec sheet?? Run them in .5 cubic Ft tuned to 70Hz. With that tuning the knee is down but at 70hz and with room gain it may work out OK.

http://www.jblpro.com/pub/obsolete/2118.pdf

Are you stuck on these drivers??? I would look real hard at what your mains will be and use that to determine the driver set for the center channel. Do you really need 2217 and 2123??? Seem's the 2217 could cover the gap just fine between the 1500 and the 375. Don't make it any harder than you have too. Using the same drivers in the same ranges as the L/R is a good thing.

http://www.jblproservice.com/pdf/Discrete%20Sales%20Models/2217HPL.pdf


Have Fun:bouncy:

Rob:)

Thanks for the info on the 2218, I should have checked the data sheet first.
The issue with the 2123, is that it may not extend low enough for my application.

I was surprise to find that most center channels are rated as full range speakers. Driver complement can range from 3" to 8" drivers with some type of tweeter. As a ref KEF’s were rated there F3 between 50 to 60hz using ~6.5" drivers.

Base on the above, an F3@50hz should have more than enough extension.
I decided on the 2123 for the mains, because after I compared it to the other drivers in my inventory it sounded the best period, clean, dynamic, smooth and authoritative. The 2235 makes it to 1.6k, but the 2123 as a midrange can bring it to the next level. The 2217 will cover what the 2123 can’t.


If the 4430’s were designed with a 2123 as a mid range driver, it could have become a statement speaker. Without it, it’s better than most current designs, but not as good as the best of today.

slxrti

slxrti
01-03-2006, 09:31 PM
Hello i have one 2446j 2" driver + 2382a horn and 2 2226h 15" in a horisontal MTM config. The box is 2,4 meter wide :) . Crossover is 700 and 40 hz.

2 closed chambers 140 liter each.

regards mats

WOW :applaud:, where the PIC"S. How do you like it?

btw, that won't hang on my wall.

Slxrti

duaneage
01-03-2006, 10:10 PM
I would focus more on the crossover design than the low frequency cutoff. OF primary concern are the lobe patterns from the two mid-bass drivers and the tweeter in the middle (if that is what you decide on doing). The crossover point will need to be carefully selected so that it is seemless between the drivers. laying a MTM on it's side changes the pattern altogether. I would opt for 18db/oct crossovers at a point determined by the distance between the midbass drivers where you have 1/2 f wavelength or less. I think you will end up tweaking the crossover a bit so mounting them externally at first will make changes easier.


Testing should really be done at different points in the seating area with white noise and sine sweeps followed by spoken word tests. It is worth noting that dual midbass drivers are not necessary for a center channel. Vertical arrangement would work fine and even a horizontal 2 way with 2 drivers only works if the drivers are close together. A coaxial driver would work well too.

The best part of a center channel lies in the crossover design in my humble opinion.

Hamilton
01-04-2006, 08:58 AM
Messing with center speaker crossover, you mean like this?

toddalin
01-04-2006, 09:31 AM
My center channel:


http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/center-2235-w15gti.jpg
The center channel shares a cabinet with one of my two subwoofers, in a separate chamber. Components include a W15GTI (sub), 2235 (center woofer), LE175, 075. New crossovers are under construction. The cabinet has a total volume of 10 cu ft.

Originally the cabinet was designed to hold my 45" table top Mitsubishi, so all alnico components were used to reduce color aberations. We now use an LCOS front projector system, and my Stewart Firehawk sits atop the cabinet on a custom made stand that I had a metal artist weld up for me.

Zilch
01-04-2006, 10:44 AM
Messing with center speaker crossover, you mean like this?:rotfl:

TWEAKER!! :p

andresohc
01-04-2006, 08:25 PM
I agree, the crossover is like a good sauce. Its a combination of craft, skill preparation, knowledge, theory, intuition and execution. It makes the meal. I can make a good sauce but not a good crossover. Ian was referring to my attempt at a center channel methinks. I am using the MTM with dual 2122Hs in order to try and push the output down to the top end of the SUB1500s which I hope to biamp. I started out with perfectly good 2123s but had them reconed by OCS to 2122Hs to get that little bit of lower extension. I am aware of the lobbing problem and will experiment a bit. If I pull this off I will have a system with similar SPLs as the 4345 and about one third the size package. I will see how bad the hole is between the subs and the 2122hs and if the elements can handle eq and power. If I dont like it I have other options for the sub.
I would focus more on the crossover design than the low frequency cutoff. OF primary concern are the lobe patterns from the two mid-bass drivers and the tweeter in the middle (if that is what you decide on doing). The crossover point will need to be carefully selected so that it is seemless between the drivers. laying a MTM on it's side changes the pattern altogether. I would opt for 18db/oct crossovers at a point determined by the distance between the midbass drivers where you have 1/2 f wavelength or less. I think you will end up tweaking the crossover a bit so mounting them externally at first will make changes easier.


Testing should really be done at different points in the seating area with white noise and sine sweeps followed by spoken word tests. It is worth noting that dual midbass drivers are not necessary for a center channel. Vertical arrangement would work fine and even a horizontal 2 way with 2 drivers only works if the drivers are close together. A coaxial driver would work well too.

The best part of a center channel lies in the crossover design in my humble opinion.

duaneage
01-04-2006, 09:58 PM
I use this:

http://www.vidsonix.com/vx3/vx_aud4ind.html

Really flexible and you can use two together for a 4 way network. It doesn't have to be a science project, you can dial up some values and go with it. Once your happy with the results buy the 12 dollar caps and the 25 dollar inductors and make it permament. I like the external feature that lets you use any value you want.

I bought mine a few years ago and have used it a lot. Not that cheap but cheaper than buying a ton of crossover parts just to test with.

And no I don't work for them or get a cut. Just thought it would be interesting to show it.

slxrti
01-04-2006, 10:18 PM
I agree, the crossover is like a good sauce. Its a combination of craft, skill preparation, knowledge, theory, intuition and execution. It makes the meal. I can make a good sauce but not a good crossover. Ian was referring to my attempt at a center channel methinks. I am using the MTM with dual 2122Hs in order to try and push the output down to the top end of the SUB1500s which I hope to biamp. I started out with perfectly good 2123s but had them reconed by OCS to 2122Hs to get that little bit of lower extension. I am aware of the lobbing problem and will experiment a bit. If I pull this off I will have a system with similar SPLs as the 4345 and about one third the size package. I will see how bad the hole is between the subs and the 2122hs and if the elements can handle eq and power. If I dont like it I have other options for the sub.

Hi, it seem that we have similar projects, If you don't mind me asking, which drivers are you using, what are your crossover freq.’s and the distance between each driver?

If I understand correctly the main cause of loping is the over lapping response between driver’s two drivers. Since two drivers share the same pass band loping will be inherent in this topology, Is this the case?

Can I assume the crossover will minimize the problem, but not eliminate it?


thanks slxrti

duaneage
01-04-2006, 10:28 PM
Lobe problems are caused by a few things. Directivity of the drivers at certain frequencies. Crossover action and pass charactoristics. Diffraction at the edge of the cabinet and against any protruding object.

In general you want to use a steeper slope to minimize the overlap between the two drivers ( I will call the dual midbass a single driver for this example) so that sound comes from one source as much as possible. The crossover can "work" with the driver arrangement to compliment or cancel lobe patterns as needed. Sophisticated software like LEAP can calculate much of this but at the end of the day your going to have to test it.

Try and crossover as high as you can. Reversing the phase of the tweeter will "tilt" the response and in some cases remedy a problem.

It is tempting to use a crossover network someone else has or that JBL produced in the faith that it is correct, tested and approved but really at the end of the day your going to have to breadboard it sooner or later.

Ian Mackenzie
01-04-2006, 10:54 PM
Because the 2212H will be horizontal in this arrangement there will tend to be a lobe with increasing frenquency b/n the two drivers. To what extent will depend on the drivers centre distances and the highest frequency in the passband of the 2122H.

I doubt if this will be too much of an issue but some practical assessment will be needed. The crossover slopes are 18 db.

The advantage of horizontal placement is however that there should be few lobes in the vertical plane other than the transition over to the 2307/2308 and its vertical polar index.

The baffle is sloped as I recall so this shoudl not be too much of an issue if you are seated watching a movie

duaneage
01-05-2006, 12:20 AM
I doubt if this will be too much of an issue but some practical assessment will be needed. The crossover slopes are 18 db.


A kind way of saying your going to have to start with 18db/oct slopes and tweak some things. Not just the crossover but driver position on the baffle, distance between them ( try and butt the woofers against each other and put the tweeter above them), maybe even slope the two midbass drivers outward at an angle to change the radiation pattern. Measure the distances for these tests and record them When changing the crossover network values record at what distance between drivers they were used. If moving the drivers keep the crossover values the same. If you change too many things looking for the quick answer your going to be disapointed with the results.

Center channels are Glorious Mono. Since stereo came along the idea of making a single speaker is strange today.

slxrti
01-07-2006, 12:36 AM
I agree, the crossover is like a good sauce. Its a combination of craft, skill preparation, knowledge, theory, intuition and execution. It makes the meal. I can make a good sauce but not a good crossover. Ian was referring to my attempt at a center channel methinks. I am using the MTM with dual 2122Hs in order to try and push the output down to the top end of the SUB1500s which I hope to biamp. I started out with perfectly good 2123s but had them reconed by OCS to 2122Hs to get that little bit of lower extension. I am aware of the lobbing problem and will experiment a bit. If I pull this off I will have a system with similar SPLs as the 4345 and about one third the size package. I will see how bad the hole is between the subs and the 2122hs and if the elements can handle eq and power. If I dont like it I have other options for the sub.w

Which midrange driver are you using? What is the spacing between the drivers? Have you had any luck with the crossovers?

slxrti

sl

Ian Mackenzie
01-07-2006, 04:47 AM
I appreciate your thought but are you asking or telling me what I should be doing?

Initally the system will be triamped.

As far as a passive crossover goes the starting point is the mid range aspect of the JBL 3145 network of the 4345 monitor and it will evolve from there. The more fundermental issues are match of the drvier sentivities and getting the 2122's to work properly down to the desire crossover point to the subs and get that crossover point working properly.

The rest is fine tuning. If necessary the baffle as to be modified we can screw around and get a nice peachy response curve latter on.



I doubt if this will be too much of an issue but some practical assessment will be needed. The crossover slopes are 18 db.


A kind way of saying your going to have to start with 18db/oct slopes and tweak some things. Not just the crossover but driver position on the baffle, distance between them ( try and butt the woofers against each other and put the tweeter above them), maybe even slope the two midbass drivers outward at an angle to change the radiation pattern. Measure the distances for these tests and record them When changing the crossover network values record at what distance between drivers they were used. If moving the drivers keep the crossover values the same. If you change too many things looking for the quick answer your going to be disapointed with the results.

Center channels are Glorious Mono. Since stereo came along the idea of making a single speaker is strange today.

4313B
01-07-2006, 07:06 AM
Hi for the New Year I would like to build a great center channel for my home theater system. The mid bass driver (pairs) options are 2218H, M203H, 2123H or a pair of 8” morel drivers, for midrange a single 2416H and maybe a single 2404 for the ultra high freq’s. The speaker configuration could be either a MTM or MT, depending or each merit's.Ick! All those components are old and ragged. :barf: Soooo last century...
Just take $1,700, order the PC600 and you're done dude. It's soooo easy!:applaud:
If you need a bit more for a perf screen installation go with the SK2-1000.
The new Project Array is really nice too. :cheers:

4313B
01-07-2006, 07:28 AM
IOW, eBay that obsolete stuff and make it someone else's problem, then get something that kicks hell out of that obsolete stuff. ;)

Hope this helps! :)

MJC
01-07-2006, 07:56 AM
slxrti, I just thought I would give you a heads up on a problem I had.
I built my HT and center around the L212 system, which has the 112A 8" mid-bass driver. I built a horizontal center using two of the 112A, one on each angled side baffle, with the 066 and 2105 mounted vertically on the center baffle. The resulting problem was way too much bass. A lot of center speakers use a smaller mid-bass driver than the matching L/R speakers, such as in the Performance Series HT system. Unfortunately JBL never made a 5 or 6 " driver that had the same sonic tone as the 112A.
So I scrapped the horizontal for a vertical 3 way, identical, to the main L212s, using only one 112A. But to get to fit below the rptv screen I didn't use a 13" tall base that the original L212s have. I made a 3" tall base that tilted back, so the 066 tweeter would be shooting to ear level, when seated.
The result is a perfect matched front end, which is what you want.

slxrti
01-07-2006, 08:25 AM
Ick! All those components are old and ragged. :barf: Soooo last century...
Just take $1,700, order the PC600 and you're done dude. It's soooo easy!:applaud:
If you need a bit more for a perf screen installation go with the SK2-1000.
The new Project Array is really nice too. :cheers:

Just a little, I noticed a few other center channel's have the tweeter in a vertical alignment and the tweeter is of small size.

A 2404 is a option for the high end, since it is smaller, thus reducing from lopping.

At this point, the use of two large drivers spaced 12" apart does not seem
like a good ideal. If were to use the 2123, I would position them similar to the SK2-1000.

thanks for the input, Slxrti



slxrti.

slxrti
01-07-2006, 08:37 AM
IOW, eBay that obsolete stuff and make it someone else's problem, then get something that kicks hell out of that obsolete stuff. ;)

Hope this helps! :)

I could sell my 375's for $3000 and my new in the box 2235 for 700 and new 2123's for 400, then just purchase 10 to 20 pair of north;)ridge.

Si:bouncy:nce I have LSPCAD design software, and my custom radio shack SPL meter (yet to be calibrated), I might as well use them.

btw, it is kind's fun to learn about the subject.

Slxrti

andresohc
01-07-2006, 10:24 AM
I am using two 2122Hs, a 2425j/2307/2308 and a 2105H. A primary design concern for me is WAF, I attempte to place the woofers together as closely as poossible and still acommodate the 2308. I juggled them on a baffle and try and package as compactly as possible. I will intitially I guess Quad amp if you include the separate sub1500s on the side (my reciever has a mode to put center channel info though the sides subs) and will follow the Xover freqs of the 4345 (I dont remember off hand). I considered angling the 2122s away but decided to keep it as simple as possible initially and if I dont like it I will try again. I had all the stuff to build these cabs laying around and thought I would practice on my mdf speaker cabinet building with my intitial center channel. I have photos of the in progress boxes (just stuck on the veneer, didnt realize that contact cement would melt my paint:( ). Lobbing will be an issue and if I cant live with it I may try and modify the front baffle and or the crossover.
Hi, it seem that we have similar projects, If you don't mind me asking, which drivers are you using, what are your crossover freq.’s and the distance between each driver?

If I understand correctly the main cause of loping is the over lapping response between driver’s two drivers. Since two drivers share the same pass band loping will be inherent in this topology, Is this the case?

Can I assume the crossover will minimize the problem, but not eliminate it?


thanks slxrti

Zilch
01-07-2006, 11:03 AM
Center channels are Glorious Mono. Since stereo came along the idea of making a single speaker is strange today.Center channels are a WAY fun DIY project. Just finding a configuration that physically mates with the video setup is a challenge.

In this one for Hamilton, I just grabbed the classic D'Appolito MTM alignment and used BB6P for the box calculations. It makes a shallow-profile (6") box that can be wall mounted, or in the installation shown, mounted under-screen with a bit of upward tilt toward the seating area:

http://audioheritage.org/vbulletin/showthread.php?t=7004

In retrospect, since we adjusted the crossover frequency a bit, studying the actual performance might reveal an optimized woofer spacing.

Hamilton's mains are 4430's, so the 2342 biradial seemed a good match. He went on to construct two-way surrounds using them and LE14A's, which also worked out:

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L200t3%20ts.pdf

I've done some subsequent work with various drivers on 2342's, and concluded that 2416H-1 sounds better than the cheaper 2418H-1. Working with 2426H on them now, what Hamilton used, I may have some recommendations for crossover tweaks soon.


I could sell my 375's for $3000 and my new in the box 2235 for 700 and new 2123's for 400, then just purchase 10 to 20 pair of north;)ridge.

Si:bouncy:nce I have LSPCAD design software, and my custom radio shack SPL meter (yet to be calibrated), I might as well use them.

btw, it is kind's fun to learn about the subject.We've already had several suggestions here in the new DIY forum that we should just sell this old stuff and buy professionally-designed systems. I kinda like Toddalin's response, if I may exercise license to paraphrase:

"I KNOW there's better systems out there to buy. I have what I have, tho, and I just want to make it work its best...."

Somehow, buyin' plastic models was never as satisfying as building 'em from scratch.... :p

Andre gets it, apparently. Is there anywhere but here to purchase that smile?

4313B
01-07-2006, 11:21 AM
btw, it is kind's fun to learn about the subject.I suppose...

You guys definitely have a fascination with the old stuff. I did too, and not that long ago either. :)

andresohc
01-07-2006, 05:32 PM
Its an opportunity to practice my cabinet making skills as well. I got to reveneer one end this afternoon, 1/32 short on one cut. Overlapped and cleaned up with a router this time. The smile is from my boy. He loves to hang out in my shop (when its not dangerous) and help when possible. For me the point is taking stuff others have passed over and celebrate what it can do when properly nurtured. Just like restoring old Honda MCs for me. Others think they are junk but when I was 14 they rocked the world and changed the face of motorcycling. I couldnt afford Hondas then now I implicitly understand the design of a 75 CB400F by dissassembling it to its smallest components and rebuilding it. Similar with my 4345 project. I would build it full sized and like the original if I didnt have a 1000 square foot house. Instead I am arrogantly trying to combine old and new technology (use what I have and make it work) I realize I am likely to fall flat on my face but at least I am up and moving and doing something. My goal this year is to spend at least as much time up and doing things each day as on the computer.

Hamilton
01-07-2006, 10:49 PM
You guys definitely have a fascination with the old stuff.
Sometimes it's not by choice...old house painters don't make a whole lot of money. http://audioheritage.org/vbulletin/images/smilies/cryingsmiley.gif

slxrti
01-07-2006, 11:45 PM
Center channels are a WAY fun DIY project. Just finding a configuration that physically mates with the video setup is a challenge.

In this one for Hamilton, I just grabbed the classic D'Appolito MTM alignment and used BB6P for the box calculations. It makes a shallow-profile (6") box that can be wall mounted, or in the installation shown, mounted under-screen with a bit of upward tilt toward the seating area:

http://audioheritage.org/vbulletin/showthread.php?t=7004

In retrospect, since we adjusted the crossover frequency a bit, studying the actual performance might reveal an optimized woofer spacing.

Hamilton's mains are 4430's, so the 2342 biradial seemed a good match. He went on to construct two-way surrounds using them and LE14A's, which also worked out:

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L200t3%20ts.pdf

I've done some subsequent work with various drivers on 2342's, and concluded that 2416H-1 sounds better than the cheaper 2418H-1. Working with 2426H on them now, what Hamilton used, I may have some recommendations for crossover tweaks soon.

We've already had several suggestions here in the new DIY forum that we should just sell this old stuff and buy professionally-designed systems. I kinda like Toddalin's response, if I may exercise license to paraphrase:

"I KNOW there's better systems out there to buy. I have what I have, tho, and I just want to make it work its best...."

Somehow, buyin' plastic models was never as satisfying as building 'em from scratch.... :p

Andre gets it, apparently. Is there anywhere but here to purchase that smile?

Hi Zilch, I would be very interested in your findings regarding the classic D'Appolito MTM alignment, before I let the wood chips fly.

If Giskard was word's of wisdom, I'm all ears :).

Slxrti

4313B
01-07-2006, 11:50 PM
Andre gets it, apparently. Is there anywhere but here to purchase that smile?Oh I get it Zilch. You're just about where I was maybe 25 years ago.

If Giskard was word's of wisdom, I'm all ears :).I don't know what you mean.

Sometimes it's not by choice...old house painters don't make a whole lot of money. http://audioheritage.org/vbulletin/images/smilies/cryingsmiley.gifYeah I hear you. I've posted quite a few times how irritated I get that people think all the old stuff is worth so much because it isn't and I'd like to see you all be able to pick it up for what it is really worth and enjoy playing around with it. It really shouldn't cost you a whole lot to pick up an old pair of L300's or what not and give them a spin, etc.

Ian Mackenzie
01-08-2006, 12:56 AM
Oh I get it Zilch. You're just about where I was maybe 25 years ago.


The context here might better be phased one years experience 25 times over....by 2031:barf:

4313B
01-08-2006, 12:59 AM
The context here might better be phased one years experience 25 times over....:barf:I don't get it.

Zilch
01-08-2006, 12:59 AM
I don't know what you mean.I used horizontal MTM woofer spacing per D'Appolito: woofs are centered one wavelength at crossover frequency each side of the tweeter centerline, in this case a 2342 horn.

I believe Slxrti is inquiring if you have any thoughts on the suitability of this alignment for DIY center channel construction....

4313B
01-08-2006, 01:03 AM
Oh. No, I don't have any thoughts on it. I use dual concentric drivers for center channels. Or I simply use three of the same across the front if they are using the requisite perf screen.

slxrti
01-08-2006, 01:05 AM
Oh I get it Zilch. You're just about where I was maybe 25 years ago.
I don't know what you mean.
Yeah I hear you. I've posted quite a few times how irritated I get that people think all the old stuff is worth so much because it isn't and I'd like to see you all be able to pick it up for what it is really worth and enjoy playing around with it. It really shouldn't cost you a whole lot to pick up an old pair of L300's or what not and give them a spin, etc.

I followed many of your other post, if you would not mind sharing your wisdom that would be nice.

slxrti

Hamilton
01-08-2006, 11:34 AM
It really shouldn't cost you a whole lot to pick up an old pair of L300's or what not and give them a spin, etc.
Cool! I'll save up some bucks, and keep the radar on! http://audioheritage.org/vbulletin/images/smilies/smile.gif

Ian Mackenzie
01-22-2006, 04:16 PM
I am using two 2122Hs, a 2425j/2307/2308 and a 2105H. A primary design concern for me is WAF, I attempte to place the woofers together as closely as poossible and still acommodate the 2308. I juggled them on a baffle and try and package as compactly as possible. I will intitially I guess Quad amp if you include the separate sub1500s on the side (my reciever has a mode to put center channel info though the sides subs) and will follow the Xover freqs of the 4345 (I dont remember off hand). I considered angling the 2122s away but decided to keep it as simple as possible initially and if I dont like it I will try again. I had all the stuff to build these cabs laying around and thought I would practice on my mdf speaker cabinet building with my intitial center channel. I have photos of the in progress boxes (just stuck on the veneer, didnt realize that contact cement would melt my paint:( ). Lobbing will be an issue and if I cant live with it I may try and modify the front baffle and or the crossover.

I' ve basically replicated this center channel enclosure now and will start some analysis of the next few days and then post some results.

Ian Mackenzie
05-20-2006, 09:20 PM
I am not sure where you are at Andre but my project has really dragged on!

I will have the final coat of JBL Blue on by Tuesday and then will try it out.

My intent is to first play with 5.1 with and without the centre channel (using an L100 to fill the hole) using a 5.1 Kenwood wonder box that I have on loan. At the moment on movies and DTS music DVD's I get goof imaging with the centre "off".

My plan is to attempt to make the centre channel box as close to the sides in voicing and see how critical that is and also see where I can put it..above or below the screen. If it works and I think it is benifical I will then decide if I make the centre a small centre with a sub or a large one..another 4345.