Backyard box building.

[macaroonie]

Hi all I'm about to start my speaker project. This has been brewing for some years and I am about ready to start. The speaker will be a reduced size L300.
If there is any demand I will post a step by step of the process in a way that
anyone can follow. The methods will be applicable to any box construction.
I am aware that many folks just dont think they can do this BUT my way its easy.
There will be an absolute minimum of fancy tools , no shop etc.
As I said if there is some takeup I am more than glad to post it up here .
Feedback please :)

[Zilch]

Yes. Backyard, I've got.

[Garage is full of you-know-what.... :p ]

[richluvsound]

Mac,

great timing . I just stripped the components out of my 4333a's.
My other Projects are on hold for parts . It would be really useful for me if you post your build.
Rich

[89-300ce]

I'm very much interested in seeing your build.

Jorg

[Thom]

How reduced?

[macaroonie]

OK guys This is for the folks who dont think they can do it. Rich you more than know the process.
Tools will be no more than a circular saw and a good quality 1/2" router plus a few hand tools.
Scaling down about 20% by volume wrt the original.

[spkrman57]

I mean as far as drivers and crossover are concerned?

Ron



OK guys This is for the folks who dont think they can do it. Rich you more than know the process.
Tools will be no more than a circular saw and a good quality 1/2" router plus a few hand tools.
Scaling down about 20% by volume wrt the original.

[macaroonie]

You will have to follow the thread as it evolves but the plan is to run fully active with a JBL m553 x/over. The main aim is to provide a tutorial for amateur cabinetmakers. No CAD no bench saw real bare bones stuff but with quality at the end.
I will start another thread as a continuous process with lots of pics n stuff and keep this one aside for comments and enquiries.

[macaroonie]

Sorry girls and boys I have been having broadband armageddon. I will post as soon as my connection is sorted out Mac:(

[macaroonie]

Please go to the other thread ' Backyard Box Building -- The Build'

[macaroonie]

just movin this up

[Duffinator]

Mac,

I'm watching your threads with great interest as I contemplate building my own cabinets. Got any opinions whether or not the Baltic birch can be finished and look nice? Maybe with just some tung oil? How about routing the corners and have a smooth finish?

Thanks

[pablol]

I'm always looking for new ways to build on the cheap, I for one would be interested. I keep thinking that a cabinet maker for my cut list is my only real option, because I live in an apartment. ***Opps, I didn't realize that the post on the bottom of the page was the first post, heheh

[macaroonie]

Sac eh the great Tomato. I lived there for nearly three years on H st at 28th took beers at The Fox and Goose down on R at 10th and various other haunts.
Birch comes in many grades qualified by the standard of A. the lamination quality ( up to no voids at all ) and B. the exterior quality. The best exterior quality will have no visible repairs on either surface and no surface defects in the top veneer.
You can get some sweet sheets that will take a spirit dye and color up nicely and then varnish or lacquer to finish. I would think twice about oiling to be honest as birch is not a hardwood and the oil will make it swell rather than harden.
Keep watchin:D

[macaroonie]

You can do this in your car park if you pick your time. You can hire the tools.
Does your home depot have a cutting facility and if so the just follow the guidelines. Remember to add the little bit extra on the cut it really is important.
M.:)

[macaroonie]

There have been some speakers over the years in plain birch cabs and they were fine if you wish to tolerate end cut ply. Klipsch did some as basics and some Euro company probably from Sweden or Finland. It works fine as long as you have good grade ply and can keep the tolerances of your work.
No reason not to in my opinion.

[loach71]

Just add some MacEwan's Scotch Ale and you are good to go...

:cheers: staggering happily :cheers:

[Chas]

Mac, great idea for a thread, especially for the wood-working dysfunctional folks, i.e. ME!

May I also suggest the use of hearing protection when using these machines of mass destruction?

[macaroonie]

Just lifting:blink:

[hjames]

It may be wet but hopefully you didn't get all the flooding I saw around Fripp's place in Dorset or Bredonborough.

http://www.dgmlive.com/diaries.htm?artist=&show=&member=3&entry=7303

and

http://www.dgmlive.com/diaries.htm?artist=&show=&member=3&entry=7297

[macaroonie]

No we get more of a continuous drizzle. It probably amounts to more water overall but then we need it for making whisky:)

[Russellc]

Say, Macaroonie,

I sent you a pm, but also decided to post a shorter version of a question I had that others might also see it as well. When you "true" the panels using the router table
contraption, I dont quite understand a thing or two: First, you left a couple 1/16ths or so to allow for this truing. You said to take it off "a little at the time" and you also mentioned it taking a few passes to true a side, then flip the board and true the other side, etc. What confuses me is it seems like when you push the panel between the cutter and the "fence" you clamped to guide the panel with, doesnt it remove all the material in one pass, or do you continually "tighten" the clamp/guide after each pass/side of panel? same question for when you true the other side of the panel, does the guide need to be adjusted in?

Thanks,

Russellc

[macaroonie]

Yes to your question the 'fence' moves in incrementally untill youi get the correct size. Pardon me I missed that one:o:

[macaroonie]

:)

[Russellc]

:)
This is a great thread! Thanks for all the trouble, and for answering my post. I have every intention of following this out to completion with my next project, and have a few more questions about your latest posts. I will post them as soon as I have them "put them into words." I am trying to understand each step so I can clearly see them in my mind. Then, I should be able to proceed to sucessful completion.

thanks again,

Russellc

[macaroonie]

Anything you think I missed chime in - it is really hard to publish what you carry in your minds eye plus all that piccy taking and editing makes the mind wander from the task at hand.
I started gluing up this evening using Gorilla for the first time. Interesting stuff
that seems to set very strong.
I will deal with the assembly soon prob tomorrow, thus far all you have seen is the panels push fit together. No hammer action either just a little dunt here and there with my forehead:banghead:

[JBLOG]

Thanks for the view! It's been real helpful as I am cutting and routing too (4345 clone).

Why did you opt for a Dado and butt joints rather than rabbet/dado all around?

[macaroonie]

Keeping it simple. No 45deg cutting which can be a headache with primitive tools. In any case the cabs will be veneered after assembly so the joints are not visible. this way i can trim the tiny excess that I have built into the edges down to exact size with the face it meets.
Bear in mind I have only used one cutter from start to present.
I've seen commercial V groove mitre tables at work and they are way accurate and big and expensive. I cant really compete with that.
Secondly I have seen so many particle board cabinets that have split at the mitres due to impact or damp. Mine will not since the ply is WBP and there is no immediate joint at the edge.
Well thats my excuse anyway your honour.

[macaroonie]

Remember that I plan to round over the front to back edges as in L300 hence 1" stock sides and base / top. I feel this lends itself better to that end.
The pic here is self explanatory

[macaroonie]

:)

[Russellc]

Great thread, really nice....please, I hope you show details of the veneering process!

russellc

[macaroonie]

I will get there Russell but I am not big on this and will take advice. I mostly use laminate ie Formica and such but real wood is another thing. Since you mention it anyone who can give any input as to the pitfalls please pitch in.
My main concern is the turn over at the rounded edge. The veneer runs horizontally and should just fold over the round over BUT ????? !!!!!

[macaroonie]

:)

[Zilch]

I don't understand why the roller guide, specifically the one you show with the bearing at the shank, wouldn't work to cut the 2405 hole using the flange as template.

Seems that would work, at least for a finish cut. :dont-know

Me, I use hole saws, as I don't have a router....

[macaroonie]

For that particular cutter---- The roller is the same size as the cutter blade dia.---------- it can plunge all the way through the stock BUT it is too hard going for it to cut lateraly once it is through. Hence one has to work a near hole but not up to the template until enough is cut away that a blank drops out. This will leave a trim cut ideally 1/8 - 3/16. This you do with the roller on the mounting flange. It is really only clean up that this tool does. You could do the same by cutting a circ. hole just less than required and then using that same cutter to clean up.
The great strength of the guided cutters is that they exactly copy what they are following and the less greedy you are in the cut the tidier the cut is.
In industry they will always make a rough cut and then a finish cut even with CNC machines.
Howz the whisky tastin comin along ?

[Zilch]

Howz the whisky tastin comin along ?Gonna hafta find me a local source.

Winter's coming.... :)

[macaroonie]

As you bay area geezers all know it all comes from the sky. My personal recommendation in the same zone ie island whisky would be this if you can find it or rather from here. :D (http://www.bruichladdich.com/web_cam.htm) Very unique, water is a must:D

[macaroonie]

As you bay area geezers all know it all comes from the sky. My personal recommendation in the same zone ie island whisky would be this if you can find it or rather from here. :D (http://www.bruichladdich.com/web_cam.htm) Very unique, water is a must:D


http://www.bruichladdich.com/web_cam.htm

[macaroonie]

re alignment. Internal is 14 x 17 1/2 x 32 minus components. I suppose it is a little less than a B380 and with no BX63. to help.
I would reckon to tune to 30Hz what do you think ?

[macaroonie]

Win ISD says for say 115 litres at 30Hz giving a nice 'knee' with a 4" port i need 153mm ie 6". Do you have any better ideas. I know you have been doon this path before.

[Zilch]

BB6P calls your gross internal volume 4.54 cuft. It deducts for the woofer displacement, and I took out another 0.2 cuft for the horn and HF drivers, for a net internal volume of 4.15 cuft.

It suggests a tuning of 26 Hz, which is B380, and too low in my experience. Giskard has recommended 30 Hz, as I recall, and I don't think you can lose with that. F3 = 39.5 Hz and F10 = 26 Hz.

4" duct at 5" long, it says. Typical BB6P lengths come out a bit long when the actual box frequency is measured.

If I've deducted too much for driver volumes, changing that to 0.1 cuft, net 4.25 cuft, the duct becomes 4.864"....

[macaroonie]

:p

[Russellc]

Sorry to be dense, but could you please describe how the tweet hole was cut? I am not following, sorry!

thanks,
Russellc

[macaroonie]

The slot tweeter has a mounting flange that can be detatched from the body.
The centre hole of this piece is perhaps1/16" bigger overall dia than the snout of the tweet ie an ideal size ( not surprisingly ) that can be used as a guide for the type of cutter shown ( with the roller up at the shank ).
However it is obvious that until the roller is down deep enough to contact the flange/ template then you run the risk of contacting the flange with the cutter blade.
In the first instance I tried plunging the cutter down to a depth that would allow the roller to run inside the flange and then tried to cut as guided by the roller. However the cut was too heavy to be sensible ( 3/4" ply at one go ) and the cutter was screaming and protesting. Pulled it out and tackled it another way this time ( using the same cutter ) freehand cutting 1/8 depth at a time in a small circle just less than the size of the flange.
Eventually broke through and a small blank fell away leaving a rough excess around the periphery. This was then cleaned off using the same cutter with the roller in contact with the flange . If you are not comfy with this the you are probably better getting a circular hole cutter of the appropriate size.
I dont like them much as they can tend to be a bit eccentric and the first contact with the material can be a bit messy

[macaroonie]

:)

[Russellc]

Thanks, that certainly clears the process up, and now I see what you mean. Thanks for the clarification!

Russellc

[glen]

I think that last pic should be your new avatar


http://audioheritage.org/vbulletin/attachment.php?attachmentid=28033&stc=1&d=1189520532

[JBLOG]

:D

[macaroonie]

Middle.......... no disrespect intended to anyone I just couldn't resist it. well spotted. Router work is pretty much done anyway barring perhaps the input panel.
Now on its all finger work. I got my veneer in today same as sample in the thread --- quarter cut oak with MEDULERY RAYS -- hey there is a new term for yez.
I have to spend a day or so getting this process down, after all this I don't want to screw it all up at the last hurdle and have Rick and Audiobeer etc all going I told you so. Actually that is not the reason I want them good for ME !!

[Zilch]

Medullary ray:

Bot. strands of parenchymal tissue extending from the pith to the bark and separating the vascular bundles in the stems of certain plants

[Russellc]

I don't understand why the roller guide, specifically the one you show with the bearing at the shank, wouldn't work to cut the 2405 hole using the flange as template.

Seems that would work, at least for a finish cut. :dont-know

Me, I use hole saws, as I don't have a router....
What kind of hole saw do you use, like a hand operated key hole type, or are you refering to the round metal cutters that goes in a drill? If so, can you reccommend a good one? I would be scared to death to come near the actual JBL flange part with a router, given my lack of experience!

Russellc

[macaroonie]

Firstly I have to mention that Scotland beat France (The world Champions) 1-0 in Paris last night !!!!!!
Eh Starrett hole saw. They do have one the correct size you will need to dig about but the correct dimension is on the site somewhere.

http://catalog.starrett.com/catalog/catalog/groupf.asp?GrpTab=Feature&GroupID=199

[Zilch]

My hole saws are Lenox, the white ones.

I also have a variety of their arbors, so it always takes a bit of head-scratching to figure out which combination to set up for which job using which drill. :p

[macaroonie]

Do NOTuse one of those cheap multi blade cutters with the black blades with a split in them. Deadly.
Do a couple of test cuts so that you are happy with your method.
If you can clamp a piece of 1/2 ply on top and cut through both you will have a clean entry into your workpiece.

Starrett Morse Bosch Lenox loads of em out there. Ace hardware or HD will have em

[richluvsound]

Mac ,

it dont matter how you got there Mate, It looks briliant. NICE ONE:applaud: Rich

[macaroonie]

Hey I just kind of got going on it. You should see that stuff in the sun -- it shimmers. Wait till I get them scraped and sanded and a wee coating of somthing special. I might have a look at shellac just to keep the sheen thing going.
Hows Ian ?






:barf:

[richluvsound]

Ian's off on a walkabout and left me in heaven. I did'nt realise there was so much more better sound that could be squeezed out of these babies. calibrating the L-pads and the Aquaplas . Not to mention me have a wire ass-backwards on one the crossovers :o:No wonder it sounded crap.

Future sound of London sounds :jawdrop:

oil and wax IMHO. shellac reminds me of a Jag dashboard:D



If you stick wee cute doilies on'em I'll PM a moderator and have you struck off:p

Rich

[macaroonie]

I like Jag dashboards.
Right style council here is a question ---- blue baffle or black. If blue it will have to run up over the top although it will not matter as that will be glass I just dont want to have a change of colour at an edge.

Does anyone have the slightest idea how to style the grilles. I have Zilchcloth but the nature of the frame etc has not really come to me yet.
I have a notion for a split grille but the driver layout tends to put the split about half way up and Hmmmmmmmmm???? to that.:banghead:

[saeman]

Sorry for putting my post in the build thread. I knew your desires but had a brain fade. I'm sure that the moderators can move it over to this thread.

The cabinets are looking pretty sporty and I'm anxiious to see that oak with a finish on it. Oak is a favorite for me and I have a project now that will be in oak, even though I have a house full of oak furniture and oak trim.

Rick

[macaroonie]

Would you like me to post you over a wee sample of that veneer if so PM me.:)

[Russellc]

Do NOTuse one of those cheap multi blade cutters with the black blades with a split in them. Deadly.
Do a couple of test cuts so that you are happy with your method.
If you can clamp a piece of 1/2 ply on top and cut through both you will have a clean entry into your workpiece.

Starrett Morse Bosch Lenox loads of em out there. Ace hardware or HD will have em
Macaroonie and Zilch, thanks again for the education on tools. the idea about the 1/2 inch ply on top sounds very good as well.

Thanks guys, very appreciated.
PS Wow! I just saw the picks of your veneering. Outstanding! I hope I can do half as well.
This really needs to be a sticky, most vaulable collection of box building info I have ever seen in one place. Not to mention its a "how to" with common tools to boot! Right up my alley, and many others I'm sure.

Russellc

Russellc

[macaroonie]

I do want to see your results though. Feel free to PM me if you get stuck.
The veneering was pretty new to me but really all it is about is arranging your pieces to suit and then making sure that your joins are straight before you stick em down. I will be doing a pictorial on this just to complete things.
I wanted this exercise to be something of value to other members and if the Mods want to make it a sticky then I would be flattered.
Remember that the whole exercise has been done with not a lot of fancy tools and in pretty ' non shop ' circumstances.

[hjames]

Thanks so much for all the detailed steps through the process. I got a sheet of paper-backed red oak veneer to redo a Yamaha receiver case - and I can already see that I'll need to skip the contact cement and try another approach with glue. (Yes, a small step, but seems to be a safe place for me to start).

[macaroonie]

You quote refers to the use of Gorilla glue in cabinet joints.
Veneering is a different matter entirely. I would suggest that for your reciever cover contact would be best coz it will certainly have some polish or oil residue.
See my post #81 inthe build thread and hang about coz I'm going to do a step by step on the 2nd cabinet:) and my subsequent reply to Rick in #85.
As it has worked out contact adhesive has presented no problems and has given me a quality result straight off.

Look for a type that allows a second try at placement, it will have a name like Timebond or somesuch. Two coats on each face and no notched spreader just keep it flat.

[Zilch]

Well, I don't understand bookmatching. That's not something you did yourself, right? You bought bookmatched veneer and then laid it up to the centerline of the cabinet sides such that the book "opens" top and bottom?

I'm supposing it would be more apparent and more critical using wood species with more prominent figuring. :dont-know

Please don't abandon us now. We want to see the finishing steps, too! :thmbsup:

[macaroonie]

In natural light the figuring is pretty obvious but the digi camera does not seem to pick it up that well. It is partially because the 'rays' seem to catch incident light and since the panels match or reflect across the center line then the top will catch it but the bottom will not appear to and visa versa.
Of course you buy matching leaves, I bought 4 so in theory my cabs are identical.
Anyway they are looking pretty nice.
I decided to go with black on the baffle as these are not 43xx of any sort.
The veneer will go to a mid to dark brown as in traditional old oak, the main reason being I have other furniture of that wood and colour.
I will be on to that tomorrow but the building as such is more or less complete. All you need to know that will allow you to home build is there already.
Anyone got a couple of cast badges ? good Kharma available.
Of course there will be final pics and such but the port is a reiteration of the tweet hole and so on and staining will not render very well online.
My plan is to press on to completion and then do a last oooh and aaaah post. I ' m going to use Balvenie 12 tube again since it worked so well in the 4315's. I concur with the length About 5.75 should do the trick.

[00Robin]

This all has been some of the most interesting read and shots ever for me. I just wanted you to know.
Some really cool man here gave me the names of two books to get and I did get them at my library and the same day my elderly mother broke her arm(ouchie!) SOMEHOW I lost them. It looks like I am buying Designing,Building,Testing you Own Speaker System AND Great Sound Speaker Manual for the Grand Blanc Library now:banghead::biting:
But this thread has really been a great read,thank you!

[Krunchy]

Hi Mac, I see your veneering job is coming along nicely, once they are stained and finished you should have a fine pair English Brown Oak "heirloom" quality speakers. Keep em coming.
Take care,

Fred

[macaroonie]

you got winter yet ? we have snow on some high up places as of yesterday.

[JBLOG]

You will need very concentrated Ammonia hyroxide to get sufficient concentrations of gasous ammonia in your tent. This is very , very nasty stuff.

As an alternative try some commercial grade diluted Ammonia you can purchase from the grocery store. Wipe some on a test piece and when you get the desired level of tannin conversion, wipe on some diluted vinagar to stop the color change. The acidic vinagar soln will neutralize the basic NH4OH. Then wipe with water. This is a trick used by folks making modern repros of Mission Furniture.

Try out some different concentrations of Ammonia as this will determine the rate of color change. This process will most likley also raise the grain a bit, so sanding will be necessary after the treatment. I would also test and see if the basic conditions of the Ammonia treatment adversly effects the glue used to tact down the veneer. Good look and I can't wait to see some pics!

[Krunchy]

Hi Mac,
No we dont have any snow yet, it has gotten cooler though, fall is on its way in all its glory. I love snow but all good things in all good time. Give my regards to the Drymen :D

[macaroonie]

Well I have been at the fuming process and have been somewhat frustrated.
JBLOG I think your technique may be the way to go. After 24 hrs in the tent ( 3x2 plastic and duct tape and staples and spray glue ) I have only returned a very slight darkening to the colour of very milky coffee.
Having said that the change is very even over the veneered area and I am concerned that direct application could end up blotchy.:(

[JBLOG]

Hi Mac,

Fuming is definitely the way to go to obtain a uniform reaction and reproducibility but really difficult to execute in a non-industrial setting. Conversion rate will be proportional to ammonia hydroxide (NH4OH) concentration and temperature (both hard to control @ home). Are you experiencing a cold September? Maybe you need more time in the tent. or ...you may need some more concentrated NH4OH. Reagent grade is closer to 30% and might be available through school/university supply shops (laboratory supply). Household ammonia is closer to 5%.

I share you concern on the 'blotchiness'. There will be a sweet spot in the ammonia concentration that will enable you to 'work' the surface uniformally in a confortable time frame. Try some test pieces with low concentrations and work from there. Check and see how much the grain raises on the veneer. These procedures were implimented for solid hardwood not veneer. There is a real art to this and also a smigin of institutional knowledge. As you said... its a learning curve and ... well, it takes some time.

With the popularity of mission style furniture, there are some great looking stains and procedures available that might provide the fumed patina you are after. You might want to look into this as well.

Cheers

[macaroonie]

Thanks for that , you seem to have been here before. I've been trying it your way today diluted 3-1 so it will be 6/7% and the colour is coming up gradually
I have done about four passes allowing to dry between each. At each pass of course the ammonia evaporates and the situation becomes stable or neutral.
I need more darker ( Like MO BASS ) so i might beef it up some. There is a good colour when I am applying the solution but it seems to fade back a little. I am doing some parallel test squares which I am trying oil and or spirit stain.
Slowly but surely. My god that stuff stinks:barf:

[JBLOG]

Its Smelling Salts...... :D

Glad to hear your makin progress.

[macaroonie]

:beamup:

[Hoerninger]

... has anyone ever investigated using two ports of differing lengths, the idea being to spread the resonance over a wider band ? Alignment ..., I have not really thought it through it was just a stray thought.
You do not intend to change the specific bass reflex alignment, do you?
For a certain speaker you need a specific volume and a specific tube which may change length and diameter combined, otherwise you have a different alignment.

Resonances within the tubes will appear far above the bass region. As the tubes are not so much different there is only little variation. Different tubes are diffuculty to handle, some math would be helpful.

Good tubes have big diameters and they widen to the ends.
Everest II has two of these (100 mm diameter), see picture.
____________
Peter

[JBLOG]

:applaud:

Gorgeous!
Outstanding Finish!!

[macaroonie]

your help brother OG. :o:

[macaroonie]

Yes yes I understand but I am not sure if you have got my concept. Perhaps
if two tubes were near to each other in length as the frequency becomes small then the small tube will resonate first and then as the average of both tubes becomes resonant ---and then the bass tube takes over?????????
I'm sure I'm well out of phase here but what the hell:dont-know

[macaroonie]

Ja ja verstehe ich aber ich bin nicht sicher, wenn Sie meinen Begriff erhalten haben. Vielleicht, wenn zwei Rohre nah zu einander in Länge waren, während die Frequenz klein dann wird, wird das kleine Rohr zuerst resonieren, und dann während der Durchschnitt von beiden Rohren volltönend ---and then the bass tube dann das tiefe Rohr wird, übernimmt? ???????? Ich bin sicher ich bin gut aus Phase hier aber was
die Hölle _____________:p

[Hoerninger]

Macaroonie,

you are driving me to the limits of my language skills. But your translation is a challenge. :D
And I do need some practice as my son lives in Scotland. Yet he has no intention to come back ... job, girl friend, country side. Recently he send me some self made pictures from Loch Lomand, beautiful.

Now to physics. With the tube there are two kinds of resonances. First the one obtained by the volume of the enclosure and the air mass in the tube (Helmholz resonator). Second but not dominating the one determined by the length of the tube (pipe). The first one is deep the second one is in the mid range nearly inaudible.

In a bass reflex enclosure the resonance may not be too sharp nor too weak. It must be choosen in that way that the energy from the speakers back will enhance the sound pressure of the deep bass. So the frequency response is extended to lower frequencies. There is no choice for another air mass in the tube, linearity of response would be lost.
When a Helmholz resonator has different tubes then the air mass within all tubes must be considered. This is easier to handle when they are all the same.
When two or more tubes contain very different amounts of air - and that is what you suggest I presume - then I do not dare to predict the result. Perhaps weak bass with some irregularities - don't know. Anyway, this is not an approved alignment, I would not do this.

On the other hand an open tube will have a resonance which is only determined by its length and not by the diameter (pipe). For a 30 cm length it would be 572 Hz. With a good construction this can be suppressed.

Many words, little anser ;). If you want to read more about alignment, here it is "schwer verdaulich" (http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20%281972-05%20AES%20Preprint%29%20-%20Vented%20Loudspeaker%20A%20Restatement.pdf) (indigestive?)

Best regards
Peter

[macaroonie]

Peter it was no more than a passing thought but it is an application that I have never seen nor heard of and be aware I worked in HI Fi since 1974 to 97 ish. In theory there would be a situation where the smaller port would become less active as the frequency goes down and at the same time the large tube would then start to work and take over as the Fo lowers. I would see the problem where both tubes are working together I would guess that would generate a peak.

[jerv]

Resonances within the tubes will appear far above the bass region. As the tubes are not so much different there is only little variation....

All bass reflex tubes exhibit this behaviour. The resonance frequency is (mostly) a function of pipe length and width. The resonance can be quite substantial, and is often at an inconvinient frequency (in one of my LE14A cabinets it was at 760 Hz, only 6-7dB below max port output at 34 Hz). This can be audible.

It is possible to damp the resonance by stuffing the tube (old socks are frequently suggested:)), but the resonance frequency and Q of the enclosure will change somewhat.

Some have suggested another solution: make the port about 1.4 times longer, then drill about 4-6 8mm holes inthe port "wall" at half length. This helps killing standing waves in the port.

I have used this solution with good effect. For optimum tuning you will have to measure actual enclosure resonance and maybe experiment somewhat with the tube length.

Espen

[macaroonie]

Ok 2 ports one chamber one driver , one port is say for example 20% shorter than ideal and the other is 20% longer than ideal. What is going to happen ?:dont-know

[Zilch]

U.S. Patent #5,479,520, Fig. 4 vs. 3.

"Schmeer." :p

[macaroonie]

I had a peek but cannot find your referrence. :o:

[Zilch]

http://www.google.com/patents?id=DlEiAAAAEBAJ&dq=5,479,520

I'm sure there are references more directly on point, but this one was on my desk. :p

It may lead you to what you want to know.... :yes:

[macaroonie]

:beamup:

[ratitifb]

Hi mac, very nice and great work i followed with great interest to learn about building ... and veenering.

Did you post in LHF about your crossover design ?

I'm interested for. My project is arround one E145-8 + 1" (i'm watching to buy a 2" driver but ... it's a lot of money ...) coupled with 2327 adaptator to the 2380 A CD Horn + 077 slot tweeter.

Could you let me know, many thanks

[macaroonie]

The system is fully active running from a JBL M553 electronic x/over.
If you search for M553 you will find the relevant posts.
Good luck with your build.:)