My plan is to use 2 x 12mm mdf with 1mm damping glue in between (25mm total).
Constrained layer damping. I really beleive in that concept.
And then some 15mm or so mdf extra on the baffle, for the woofer to be flat.
Bracing to be done with something stiffer than mdf, probably plywood.
Flodstroem, it would be interesting to know if a tuning of 25Hz would work with 113L. Or which volume would be needed for that.
And where on the front-baffle you would place the ports.
And which tuning frequency original 4365 box has, based on the data I provided (4.2 cu ft volume and dual 8.5cm diameter ports with lenght of 15cm).
Im going to check that but Im to busy right now. I can do it Sunday evening as the earliest
X-max for the 1501fe seems to be approx 9.5 mm what I understand from this:
Flodstroem
And for your project its essential that the woofer should be located as high as possible in the cabinet or correct me if Im wrong...............Originally Posted by bubbleboy76
Flodstroem
Correct.
For 2 reasons:
1. Keeping woofer/horn cc distance as low as possible.
2. Getting center of woofer as close as possible to 60-65cm from floor (1/4 distance floor-roof).
I did a quick lookup in Thiele's paper.
An alignment which fits is a QB3 somewhere (interpolated) betweeen alignments #2 and #3.
Alignment #3 results in f3 = 53 Hz, Vb = 49 Liters, fb = 42 Hz.
That is a ballpark figure. You can vary that a bit, but not much.
Ca. 50 Hz from a 50 liter box is quite attractive.
Ruediger
This is a bit over my head, at the moment. Bare with me
Is this vented or close box you are taking about?
This is much higher tuning than I expected. I want as much fullrange speaker as possible (including room gain).
You are indicating that original 4365 (119L) is more than twice as large as it should be?
50L would be very nice so I could reduce the dimensions more to my liking. But I do not want to have to have subs. They must be able to reproduce music by themselfes.
Hi bubbleboy76,This is a bit over my head, at the moment. Bare with me
Is this vented or close box you are taking about?
This is much higher tuning than I expected. I want as much full-range speaker as possible (including room gain).
You are indicating that original 4365 (119L) is more than twice as large as it should be?
50L would be very nice so I could reduce the dimensions more to my liking. But I do not want to have to have subs. They must be able to reproduce music by themselves.
I can only imagine (using 1501FE driver) the bass box of round 156Lit, tuned at 36Hz ( with TWO duct internal diameter 105mm, and the length about 130mm each), so I can imagine to reach down to 35Hz (-3db) even less if room influence assumed.
regards
ivica
One option I have thought about is to use M2 box volume (140L) and tuning, togheter with M2 dsp for LF, as a starting point.
But 140L feels too large for my wanted speaker size. Going for 4365 box volume of 119L is more ok for my wanted design.
Another option would be to try to copy the K2 S9900 (96L) tuning.
(I really appreciate all the help).
Closed box with corner gain and a lot if dsp feels to me "easier" to get ok. With my limited knowledge.
The oscillator equation (for circuits made from R, L & C or sytems made from masses, springs and friction) is the same in mechanics and in electrodynamics (see electroacoustical or electromechanical analogies). The math is the same. One can apply the mathematical techniques from electronics to mechanical systems.This is a bit over my head, at the moment. Bare with me
Is this vented or close box you are taking about?
The equivalent electrical circuit for a loudspeaker in a vented box looks very messy and hard to handle. Thiele found out that if certain assumptions are justified the equivalent circuit can be simplified. A speaker in a vented box is a highpass filter of order 4.
These filters have been investigated, there are Butterworh, Bessel, Cauer etc. They are described by polynomials in frequency and the coefficients are made up from the so-called Thiele parameters.
Thiele compiled a table with alignments such as Butterworth filter of order 4. Given the Thiele (-Small) Parameters you can jump into that table and look up matching alignments. Within a few seconds you can tell what is possible with a certain speaker and what not.
You can find the Thiele Paper here in this forum: General Audio Discussion, 3rd entry: Technical References, 11th entry therein.
In many cases you will need to interpolate between alignments. And you can make your Qt (speaker Q) fit. You can experiment with different parameters and plot the result. At least you get a starting point for an educated guess.
Ruediger
Hi,
Not to say that there are some Vented box calculators on Internet:
http://www.mh-audio.nl/reflexboxcalculator.asp
http://www.micka.de/en/
http://www.ajdesigner.com/speaker/bcv.php
http://www.ajdesigner.com/speaker/ajvented.php
http://www.troelsgravesen.dk/ports.htm
etc
ivica
I think I will start with LF test-boxes that approximates the original 4365 volume and tuning:
Testbox with 4365 LF internal volume (4.2cu ft / 119L)
External dimensions:
Width 560mm
Height 1000mm
Depth 310mm
About 126L without bracing (119L with 7-8L bracing)
25mm mdf
Woofer at top of front baffle. 2 ports at bottom of front baffle.
A thin layer of damping on the inside, like 1/2" thick.
I have choice of BR-tube with 69 or 103mm internal diameter:
http://www.hifikit.se/tillbehor/aeroport-4
http://www.hifikit.se/tillbehor/aeroport-3
Flodstroem, can you help me calculate the best port dimension and lengths for tuning this box to 20, 25, 28 and 32Hz, respectively?
Found this post about 1501fe. It is probably 32Hz tune on the 4,2 cu ft box in 4365 then.
Greg used it in a 4.2 cubic foot volume tuned to 32 Hz and yes, WinISD does yield smaller volumes with less bandwidth.
I do have a pair of enclosures in progress that are something like 3 cubic feet tuned a bit higher for more impact. The AutoCAD drawing is on my laptop which I don't have access to at the moment. All the MDF is already in the garage stacked next to the table saw and, true to form, it's been there for months.
My plan was to build "B4" volumes with the option to tune them as "B6" volumes for response to 25 Hz. I figured that was as low as I wanted them to go.
I'm not sure what volume/tuning 1audiohack evaluated a pair in. I'm not sure what volume/tuning RobH3606 plans on evaluating the same pair in. I'm not sure what volume/tuning hlaari plans on using. Jerry Moro wanted to know how we all used them and whether or not we liked them. He mentioned that he didn't have a whole lot of experience with system design so he was interested in our feedback.
The 1500AL in the 4.6 cubic foot volume tuned to 28 Hz is a real work of art. The 1501FE won't beat it, but it should be very nice in its own right. Plus it isn't as heavy or expensive, albeit just as impossible to obtain. Rather irritating actually. To this day neither Greg nor Jerry seem to be able to fathom why it is impossible to get these transducers or their recone kits. I've read some of their internal emails and they seem totally perplexed. I suspect Harman simply doesn't want to stock anything and that means not building spares.
Yea I can do it tomorrow I guess
Good you have all the dimensions listed. That helps.
Flodstroem
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