| SCD |
I guess I have been programed by the mass market designs to find the narrow cabinet more apealing. I recall a design that GM did for Pea using the JS92 that I liked. I think it would be possible to take the folded ML design put it on a psuedo stand with a down firing port and a slant front and I would be very happy.
Other comments:
The brace in between the two drivers needs to be just right and firmly anchored to both drivers. The mounting screws for the drivers must be bolts rather than screws if the brace is not just right. Harmonic and construction forces will challenge the integrity of the mounting screws. for visible ports I prefer slots with roled edges they seem more graceful to me. |
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| SCD |
Another thought:
I was reviewing some of the design work That MJK did with the Fe164. When he folded the TQWP it developed a ripple in the mid frequency range. One of our earlier designs has the fold point just below and behind the driver with the fold going side to side. This results in a wider front baffle, yet it appears to charge both sides of the line equally. With the fold going front to back I think it might be important to ensure the line gets charge equally. I am not sure how this can be evaluated?
Any thoughts? |
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| Timn8ter |
| Minor variances in the length of the coupling dowel (-1mm) might be dealt with by placing a small amount of Duct Seal on the magnet backs where the dowel is placed. Does this seem an acceptable method? |
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| Timn8ter |
| quote: | Originally posted by SCD
Another thought:
I was reviewing some of the design work That MJK did with the Fe164. When he folded the TQWP it developed a ripple in the mid frequency range. |
That's surprising. All the statements I've read concerning folding pipes say that there are no detrimental effects. :xeye: Did I miss something? |
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| planet10 |
| quote: | Originally posted by Timn8ter
Minor variances in the length of the coupling dowel (-1mm) might be dealt with by placing a small amount of Duct Seal on the magnet backs where the dowel is placed. Does this seem an acceptable method? |
That is similar to what NAIM is doing... so far the distances i've had to deal with can be covered with a sheet of paper (in fixed brace subs) or with the hot glue i use to loosely attach the dowel to the back of the magnet.
dave |
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| SCD |
Maybe I read it a little too fast but I think the diagram on page 11, 12 shows a ripple. I am not as up on the theory as you guys I just threw the idea out there. I may be off the mark and it may not be an issue.
Firmly coupling the drivers is important. I have some ideas that I plan on trying. I will share once I get them a little more refined. |
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| SCD |
Hot glue was I what I was thinking as well.
The other idea was threaded rods at the mounting points. I was thinking about hexagon rod that was cut to length tapped and threaded. This may be over kill for this driver yet it is the one that is needed for the Push push bass drivers. |
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| planet10 |
| quote: | Originally posted by Timn8ter
That's surprising. All the statements I've read concerning folding pipes say that there are no detrimental effects. :xeye: Did I miss something? |
Depends how well you fold it... in my fold the drivers are still appearing the same offset from the end of the line... in your fold they have different offsets (not necessarily a bad thing, just another detail the models don't handle)
dave |
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| planet10 |
| quote: | Originally posted by SCD
The other idea was threaded rods at the mounting points. I was thinking about hexagon rod that was cut to length tapped and threaded. This may be over kill for this driver yet it is the one that is needed for the Push push bass drivers. |
Similar to this?
be nice if drivers all started coming such that you could put a big bolt or screw thru thru th epole piece to secure them (and not have th magnet unintentionally pulled off)
dave |
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| Timn8ter |
| quote: | Originally posted by planet10
Depends how well you fold it... in my fold the drivers are still appearing the same offset from the end of the line... in your fold they have different offsets (not necessarily a bad thing, just another detail the models don't handle)
dave |
True, I was considering the acoustical center of the backwave but really don't know how that all works out inside the enclosure. My bipoles to date have not been folded. Should we consider something similar to my bipole 1197s? No fold yet still a reasonably sized enclosure. We could mount the drivers on the narrow side too I would think. |
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| amt |
On my drivers, I used two pieces of wood that are slightly larger that the magnets and then routed out a hole for the magnet to seat into. Then cut the eyelets off of both ends of a turn buckle and threaded them into the two wood rounds. Just slip it between the drivers and tighten to the desired pressure. They cant slip or loosen and can be taken on and off easily.
amt |
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| Timn8ter |
| quote: | Originally posted by amt
On my drivers, I used two pieces of wood that are slightly larger that the magnets and then routed out a hole for the magnet to seat into. Then cut the eyelets off of both ends of a turn buckle and threaded them into the two wood rounds. Just slip it between the drivers and tighten to the desired pressure. They cant slip or loosen and can be taken on and off easily.
amt |
This necessitates a removable panel somewhere on the cabinet and assumes no bracing interferes with your hands/tools getting to the bolt. It's a very good concept though.
After looking at the possibilities I'm looking back to my initial proposal for a bipole on a psuedo-stand. Depending on the preferred listening height that would make the stand 20" to 25" high. |
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| SCD |
Good thoughts AMT:
The concern I have with just a one way coupler is that it transfers the energy to the mounting screws or even to the glue holding the magnet to the driver. Dave has shown a good drawing of the concept I was trying to present. This may be a bit of over kill for this project though.
I was also wondering if plugging up the vent in the pole of the magnet with a bolt will effect the performance of the driver, but that is a queston for another discussion. |
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| planet10 |
| quote: | Originally posted by SCD
I was also wondering if plugging up the vent in the pole of the magnet with a bolt will effect the performance of the driver, but that is a queston for another discussion. |
In the case of the drivers that inspired the above drawing, the hole in the pole-piece was designed specifically to put a bolt (or in his case a lag screw). This designer would never put a vented pole-piece in any of his designs -- he doesn't like the soup-can resooance they cause.
dave |
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| amt |
I actually took the concept partially from Mr Linkwitz, who mounts his mid-drivers by the magnet and not the frame. I just added a squeeze to the equation rather than a firm grasp. And you are right about access. I use a removable top plate on my speakers so I can re-wire, add tweeters etc. Another option would be a wedge block that fits between the drives and a threaded rod would expand it (like a bicycle stem) The rod could terminate at the bottom of the cabinet where it cant be seen. And it could be tightened after the speaker is functional.
amt |
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| SCD |
Anyone care to summarise where we are so far and what we need to still discuss.
I think we have come a long way along the group design trail. There are few things to conclude still, but good for us this seems pretty good so far. |
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| Timn8ter |
The selected driver is the Fostex FE127E.
There will be two designs:
1. Single driver w/BSC
2. Two driver bipole wired in series.
We have one straight pipe bipole design and two folded bipole designs.
We do not have a monopole design although it should just be a matter of reducing the size of one of the bipole designs.
It appears our next step shoud be to select one of the bipole designs unless someone has another one to offer for consideration. |
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| planet10 |
| quote: | Originally posted by Timn8ter
2. Two driver bipole wired in series. |
We should be more flexible than to mandate series or parallel connection
| quote: | | We do not have a monopole design although it should just be a matter of reducing the size of one of the bipole designs. |
Many of the bipole designs can just be sliced in half to become monopoles.
dave |
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| Timn8ter |
| quote: | Originally posted by planet10
We should be more flexible than to mandate series or parallel connection |
True. It makes for an interesting comparison.
| quote: | Originally posted by planet10
Many of the bipole designs can just be sliced in half to become monopoles. |
Exactly. Shall we select one of the proposals? Then we can move on to construction specific things such as bookshelf or psuedo-stand and driver coupling techniques. |
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| gmilitano |
| quote: | Originally posted by x. onasis
As a "common to many of us" reference speaker project, I'll definitely participate, but let me just say that my feeling from the other "reference" project, is that we didn't set our goals high enough to get wider involvement. |
| quote: | Originally posted by Timn8ter
The selected driver is the Fostex FE127E.
There will be two designs:
1. Single driver w/BSC
2. Two driver bipole wired in series.
We have one straight pipe bipole design and two folded bipole designs.
We do not have a monopole design although it should just be a matter of reducing the size of one of the bipole designs.
It appears our next step shoud be to select one of the bipole designs unless someone has another one to offer for consideration. |
I suggest that we take a step backwards for the moment. One thing we have not done is set performance goals.
I suggest that the performance of this reference project should exceed the performance of the Fostex reccomeded enclosure:
http://www.fostexinternational.com/...27e_enclrev.pdf
Having said that, I think the next step should be to model a single driver design that will better the preformance of the Fostex design.
Once that is in place, the bi-pole version should essentially be a matter of doubling the mono-pole design. We could also investigate series and parallel connections.
If we do the bi-pole design first, we have no relative benchmark to judge the performance of the design.
Anyway, just my 2 cents.
Gio. |
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| SCD |
| Dave did a quick mono pole design earlier in the string. I am not sure if anyone closely evaluated it or checked it potential. |
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| Timn8ter |
Do you mean this one?
http://www.diyaudio.com/forums/atta...tamp=1102221644
I was trying to figure out what the physical measurements of the line and CSA were. At first glance the line appears too long. Pretty darn close for gosh and golly though. Can that line be shortened up any? Something like L=32, CSA=24?
| quote: | | Having said that, I think the next step should be to model a single driver design that will better the preformance of the Fostex design. |
That may be a tough one. I think we can do a little better and have a simpler design. I've not tested the Fostex design but my guess is efficiency is less and power handling is higher in their design than a TL would be. |
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| x. onasis |
About the "quality" of the other reference project.... And what I meant about not setting our sights high enough:
That project initially aimed for a speaker that might be described as good quality 2-way, useful for A/B comparisons to our other projects and using drivers that would show potential for tweaking or redesigning for other/better applications. Perhaps it was the second part of that criteria or maybe the way it was presented that pushed it more toward the simplest, newbie/first DIY speaker of decent quality.
At any rate what we didn't end up with, was a project worthy of interest to veteran builders who already have more hi-end reference speakers and realized the P13/D27 combo in a small cab would have its limitations. Namely that no matter how clear the mids and highs, this simple 2way needs a sub and would never have the presence a larger woofer/cab combination would have.
In retrospect, at $200, or twice that for the TLb, (in order to get decent midbass presence), looks to me that this price has too much competition for experts with too many projects already on their wishlist. Even in the DIY Frugalphile (thanks Dave) world, there seems to be a price/performance ratio albeit with different compromises.
This fullrange project, OTOH should cost half of that one and (hopefully) the compromise is in maximum SPL's, with the gain being the imaging of single-point-source, surprising bass from TL's and the quality reputation benchmark of Fostex. Those of us who persue frugal as a starting point will likely learn something yet again. For myself, I've learned to have great faith in the advice of the posters who've moved this project along, and hope it continues.
Thanks for your efforts.
I like the designs with the narrow front cabs, I'll be building both, knowing that whichever becomes my reference, the others will find a home. My drivers are on the way. |
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| SCD |
Well said x. onasis:
It looks like we got stalled a bit. Perhaps we should get back to the design details of either the bipole or the mono with BSC. Is it safe to assume the published T/S specs from fostex are close enough to conclude our designs.
Tim have you checked the numbers from a set of drivers that have been broken in?
some common design concepts to start things off:
Birch plywood or solid wood is very good
Use 1/4" concrete board to line the inside of the enclosure
Try to get non-parralel insides.
Brace the panels to eliminate enclosure resonance
Use cat 5 wire inside the enclosure
Use duct seal to reduce driver basket resonance
That should get things going again |
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| planet10 |
| quote: | Originally posted by Timn8ter
I was trying to figure out what the physical measurements of the line and CSA were. At first glance the line appears too long. Pretty darn close for gosh and golly though. Can that line be shortened up any? Something like L=32, CSA=24?
|
That design is as close as i could get to 30" long as i could get (by gollying) and has 24 in^2 CSA. If you want it 32" increase the height -- including the middle divider -- by an inch.
dave |
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| Timn8ter |
| quote: | Originally posted by SCD
Well said x. onasis:
It looks like we got stalled a bit. Perhaps we should get back to the design details of either the bipole or the mono with BSC. Is it safe to assume the published T/S specs from fostex are close enough to conclude our designs.
Tim have you checked the numbers from a set of drivers that have been broken in? |
I have not personally, however, others have and the variances are minimal.
| quote: | Originally posted by SCD
some common design concepts to start things off:
Birch plywood or solid wood is very good
Use 1/4" concrete board to line the inside of the enclosure
Try to get non-parralel insides.
Brace the panels to eliminate enclosure resonance
Use cat 5 wire inside the enclosure
Use duct seal to reduce driver basket resonance
That should get things going again |
I like working with those materials although by the time you add concrete board and braces the external material becomes less consequential IMHO. Non-parallel sides can be beneficial but I wonder if less experienced builders would be put off by it. Basket damping is definitely recommended as is adding felt to the magnet back. I also like lining surfaces close to the back of the driver with felt or poly-batting. I had put up a FR graph for the monopole but I apparently deleted it when I edited my comments.
:cannotbe: At L=32" and CSA at 24"^2 it looked pretty good. |
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| planet10 |
| quote: | | Fostex recommended enclosure |
Not being a big fan of BR in general -- i have heard some that are OK -- i'd stay way-way away from the double bass reflex... and from the tuning on the BR i'd say we are already achieving a lower F3 (due to the support of the quarter wave resonance). All the BR gains you is some cabinet size savings (10 litre vrs about 14 litres)... the ML-TL is also inherently better braced (and if you routed off that top-front void would give you a little bit of un-rectangular flair to the box.
dave |
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| planet10 |
| quote: | Originally posted by Timn8ter
I had put up a FR graph for the monopole but I apparently deleted it when I edited my comments.
:cannotbe: At L=32" and CSA at 24"^2 it looked pretty good. |
Post it again...
dave |
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| Timn8ter |
| quote: | Originally posted by planet10
That design is as close as i could get to 30" long as i could get (by gollying) and has 24 in^2 CSA. If you want it 32" increase the height -- including the middle divider -- by an inch.
dave |
I could see the CSA but didn't know L. L=30" produces a slight bump in the upper bass which isn't a bad thing when contemplating baffle step. Could make calculating a BSC difficult or unneccessary. |
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| planet10 |
| quote: | Originally posted by SCD
Birch plywood or solid wood is very good |
we can specify this as standard (pick 1 -- ply would be my choice) but with people out looking for shelving to cut up to make boxes we should leave it clear there is some flexibility.
Also, what is standard -- if you go into home despot what widths can you buy (so i can tailor a design to standard widths)
| quote: | | Use 1/4" concrete board to line the inside of the enclosure |
I'd move towards 1/2" ply with extra hardwood bracing before i mass-loaded with concrete (matter of fact i'd do alot of other things before i added concrete board which is antithetical to my concepts of cabinet building)
| quote: | | Try to get non-parralel insides. |
Always a laudable goal, but hard to acheive in a box if you don't have Scott-Dunn-like woodworking skills... the easiest way to achieve a large portion of this requirement is to build a tapered line instead of a straight one -- we have one ML-Voigt on the table already... what can we get out of a tapered line? with or without ML?
| quote: | | Brace the panels to eliminate enclosure resonance |
The largest expanses are not all that wide... but this is never a bad idea.
| quote: | | Use cat 5 wire inside the enclosure |
a very good base
| quote: | | Use duct seal to reduce driver basket resonance |
There are a number of driver mods that i considered required minimum, and this is one of them.
For the reference design we should keep things fairly simple -- the addition of enhancements can then give people an idea of the veracity of those enhancements.
dave |
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| planet10 |
| quote: | Originally posted by Timn8ter
I could see the CSA but didn't know L. L=30" produces a slight bump in the upper bass which isn't a bad thing when contemplating baffle step. Could make calculating a BSC difficult or unneccessary. |
A bump also probably means a bit less desirable group delay thou...
Here is V0.2 which is an inch taller to make the line 2 " longer. The driver also moved up an inch to keep it in the middle. (keep in mind that tho deflectors are probably more important as braces than they are as reflectors, ie the woodwork challenged could leave them out to simplify things).
dave |
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| Variac |
A tapered TL can be created by getting some 2" thick rigid foam insulation at Home Depot while picking up the wood type material.
You cut it to size, taper the thickness along the length (from 2" to zero) then put this on one wall of the box.
The only tricky part is tapering the foam. The best way is using a hot wire cutter- which is pretty easy to make with nichrome wire and a transformer. BUT if you just cut it with a bread knife and a sawing motion you can do it. This leaves a rougher surface which his probably better actually. AND you end up with 2 pieces from one cut. Easy to make deflectors this way too....
Yes, let's also make the design buildable using shelving from there too. I'll try to do research - someone else do it too- the crowds are packing the place this close to Christmas. |
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| planet10 |
| quote: | Originally posted by Variac
some 2" thick rigid foam... Easy to make deflectors this way too.... |
good reflectors... not so good as braces. if you were going to go this way you could try to follow the circular arcs done in dotted red...
dave |
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| Timn8ter |
| I like monopole v0.2 for it's simplicity, inherent cabinet bracing and having built something similar I'm familiar with it's performance which is quite good. :up: |
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| hoz816 |
Actual board measures can be found here: http://www.arnoldlumber.com/size.html
This applies to solid wood boards (generaly spruce or pine). All of the board sizes should be readily available (with the possible exception of 1x10 in some areas).
Home Depot also carries MDF in 3/4 thickness in 12 and 16 inch widths. I believe the 16" width is available in 48" lenghts, and the 12" in 96" lengths.
Hope this helps. |
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| Variac |
| Yes, these are the actual dimensions of nominal lumber as I mentioned before. The unknown (for me :D ) is if shelving is in the same widths. |
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| amt |
I tend to agree with Timn8ter on the monopole. Although the bipole will produce more LFs, even with the rear driver inductored, it still wont point-source as well as the monopole. If we are building a "reference" speaker for the Fostex, we should concentrate on making the virtues of a single driver shine. And bass response isnt really one of them. The simplier monopole will really show the drivers qualities best and would probably be built by far more people than the bipole. Adding a sub can be easily done to round out the sound. Now we have a speaker that can be used in a satalite/sub system, office/bedroom/dorm etc. More flexibility lower cost and ease of construction. The cost savings from the extra drivers can go towards woofers or proper stands.
amt |
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| hoz816 |
Actually, the 1"x** boards are used as shelving material. Most often the 1x12. The only other shelving material that I am aware of is the MDF shelving, common particle board, and the various pre-finished-vinyl-coated ones.
Also, most home centers will have these boards available in different species and grades of wood, including red oak in most sizes - which may make a very nice finished cabinet. The oak, however, may be expensive for many. |
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| Variac |
As has been pointed out, the monopole and dipole are pretty much the same thing. For simplicities sake we could focus on the monopole, but I certainly hope that people also make the dipole and that we can also discuss good/bad points and tweaking tips for the dipoles in this thread. After all, if you are willing to assume that bass is expendible and a sub is needed, then we might have to consider other approaches instead, such as open baffle.
Also in some rooms isn't it posible that the bipole would point source better? |
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| planet10 |
| quote: | Originally posted by Variac
hope that people also make the dipole... for the dipoles
.... the bipole.... |
bipole. bipole. bipole.
dipole & bipole are not interchangable
(gotta keep harping on this until it is ingrained :))
dave |
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| planet10 |
next... v0.2 of the bi-pole & mono-pole with provisions for building out of shelf material (see note 6)
extend sides or front & back (or both) by ~19" to get a free-standing box with driver at 36"
dave |
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| Timn8ter |
| quote: | Originally posted by planet10
bipole. bipole. bipole.
dipole & bipole are not interchangable
(gotta keep harping on this until it is ingrained :))
dave |
I'm really happy one minute then sad the next. What do you think that could be? :rolleyes: |
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| planet10 |
| quote: | Originally posted by Timn8ter
I'm really happy one minute then sad the next. What do you think that could be? :rolleyes: |
Not enuff Lithium?
Where is that FR plot for the 32" -er?
dave |
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| Timn8ter |
I must be BIPOLAR!
:) :( :) :( :) :( |
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| amt |
The bipole cant point-source better since the reflected sound of the rear speaker creates a point the size of the rear wall. I have a switchable inductor on mine so I can use the rear driver below 150hz just for the LF help. It becomes a different speaker this way. And remember that if a bipole is placed close to the rear wall were the best LF reinforcement is, it destroys the midrange presentation.
As far as a dipole goes, they will probably always sound the most natural BUT implementation is always difficult. They have to be big, placed out in the room and little FRs next a pretty high XO so integrating the sub is tricky. A Basszilla concept is a good way to go.
My personal plan is to use the monopole and play with a 4th order BP stand w/o a crossover. Sort of a Whamodyne meets the LS35a sub.
http://home.freeuk.net/pwhatton/subs.html
Below is a winISD screenshot of a 1197BR and a 8" Dayton 4thBP. If the Fostex could be integrated, it could be a solid bottom end w/o passives. Just a thought.
amt |
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| planet10 |
| quote: | Originally posted by Timn8ter
I must be BIPOLAR! |
You should be saving those as gifs... i cleaned out the jpg noise, added a title and put it back.
60 Hz F3, 40 Hz F10... pretty amazing for a 127mm driver.
I'm thinkin' this could surprise a few people :^)
dave |
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| planet10 |
| quote: | Originally posted by amt
The bipole cant point-source better since the reflected sound of the rear speaker creates a point the size of the rear wall. I have a switchable inductor on mine so I can use the rear driver below 150hz just for the LF help. It becomes a different speaker this way. And remember that if a bipole is placed close to the rear wall were the best LF reinforcement is, it destroys the midrange presentation. |
by its very nature a bipole shouldn't be too close to the back wall -- particularily for bass reinforcement. If the speaker is far enuff out from the wall then any reflected sound should merge into the sound field and not be perceived as a source, making the bi-pole act like a mono-pole as far as direct sound goes... of course the bipole has flat power response.
Flipping the inductor in makes a 1.5 way with a monopole source on the top... power-response will be lean at the top -- having a switchable choke (or cap in the case of series wiring) is a good idea.... the filter should be sized to correspond with the baffle step.
dave |
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| amt |
Dave, granted the sounds will merge but this is placing the speakers 4-5' into the room. Mine are about 2.5' in and there not much merging going on. There a night and day difference inductored/versus non. But I do hate losing the dbs.
BTW, dont you have BDs with the angled up rear driver? Have you compared that design with an opposed driver design. Ive wondered how the reflections change and each sound relative to each other . Ive actually hung t-shirts and such over the back speaker for tweakng purposes. Looks bad but sounds good. This is a poor mans' inductor.
amt |
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| planet10 |
| quote: | Originally posted by amt
BTW, dont you have BDs with the angled up rear driver? |
We compared those against Tim's BP 1197 ML-Voigts... Tim's speaker was decididly better... in my room 2.5 ft is as close as i can get my speakers to the back wall when i'm tucking them in... 4-5' is normal and optimum room placement (i'd have to flip the whole room around again -- currently as is for SAF and to accomodate a TV monitor) they are more like 6' out (24' x 16' main room -- with another 8' x 24' mostly open next to it, and another 12'x24' space open on the end)
dave |
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| planet10 |
| quote: | Originally posted by amt
There a night and day difference inductored/versus non. |
I have no doubt...
dave |
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| Timn8ter |
| quote: | Originally posted by planet10
You should be saving those as gifs... i cleaned out the jpg noise, added a title and put it back.
60 Hz F3, 40 Hz F10... pretty amazing for a 127mm driver.
I'm thinkin' this could surprise a few people :^)
dave |
Lucky for me you're not asking for a vector format. :D
I've seen several surprised faces when the FE127E is demo'd. :cool:
A question about the suggestion to use Cat5 as internal wiring. Does that mean all 4 pair? |
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| planet10 |
| quote: | Originally posted by Timn8ter
Lucky for me you're not asking for a vector format. :D |
The vector files i've gotten out of MathCad chomped (and that is being kind)
| quote: | | A question about the suggestion to use Cat5 as internal wiring. Does that mean all 4 pair? |
I assumed a single pr, but some people might want to use more -- using all 4 pr is certainly easier.
dave |
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| gmilitano |
| quote: | Originally posted by planet10
next... v0.2 of the bi-pole & mono-pole with provisions for building out of shelf material (see note 6)
extend sides or front & back (or both) by ~19" to get a free-standing box with driver at 36"
dave |
Looks good. I imagine we could also do a version with the driver at say 25% from the top or something.
Another thing, can the bi-pole be folded?
Gio. |
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| planet10 |
| quote: | Originally posted by gmilitano
I imagine we could also do a version with the driver at say 25% from the top or something. |
The driver offset from the end of the line is used to kill the 1st undesirable line harmonic... its placement is critical....
| quote: | Another thing, can the bi-pole be folded?
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An example of the folded one has been posted -- Post #95 (althou may need to adjusted for length -- still haven't dug out Denson's paper + we've increased line length from 30 to 32")
dave |
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| gmilitano |
| quote: | Originally posted by Timn8ter
A question about the suggestion to use Cat5 as internal wiring. Does that mean all 4 pair? |
| quote: | Originally posted by planet10
I assumed a single pr, but some people might want to use more -- using all 4 pr is certainly easier.
dave |
I have read over Nelson Pass's article regarding Current Source amps and Sensitive Full-Range Drivers.
http://www.firstwatt.com/current_source_amps_1.htm
Anyway, I think this is a must read for anyone interested in full range drivers.
The article does not cover the FE127E, but does look at the FE108E Sigma driver, which is similar to the FE127E. The article shows a much improved response of this driver with a current source amp + parallel network. The article explains that the network can be simplified as a single resistor.
Using that info, the optimal speaker wire for this driver may be a small diameter wire (high gauge).
Cheers,
Gio. |
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| Timn8ter |
| quote: | | the optimal speaker wire for this driver may be a small diameter wire (high gauge). |
I've been using a single pair from a Cat5 cable for some time now. For use with drivers like this it works well. Using a high guage solid conductor for internal wiring is agreeable to me also. |
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| SCD |
Hello dave:
I was studying the diagram from post 96. It may be an artifact of the sketch but it looks like the volume between the drivers is a little high. Could you check, I think the volume on the right side has been double counted.
I really like this presentation, I am thinking it would look similar to my current MLTL if I extend the sides. I checked with M last night and she likes the presentation as well. I may end up with a fleet of Fostex speakers. A bit of a stereo design showroom so to speak. All I need is a handmade tube amp or current source amp. |
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| planet10 |
| quote: | Originally posted by SCD
I was studying the diagram from post 96. It may be an artifact of the sketch but it looks like the volume between the drivers is a little high. Could you check, I think the volume on the right side has been double counted. |
96 is an alpha drawing of #98 which is more correctly as Tim envisioned it (he specified the dimensions -- i noted to myself that the partition is 6" from the top and 5 out from the sides). This design has the issue of the 2 drivers having different offsets from th ened of the line... this means that a model (with 2 driver equivalent firing out the top) is not necessarily going to as accurately portray things as a design where the 2 drivers have the same offset... it could work great thou.
dave |
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| Timn8ter |
| quote: | Originally posted by planet10
96 is an alpha drawing of #98 which is more correctly as Tim envisioned it (he specified the dimensions -- i noted to myself that the partition is 6" from the top and 5 out from the sides). This design has the issue of the 2 drivers having different offsets from th ened of the line... this means that a model (with 2 driver equivalent firing out the top) is not necessarily going to as accurately portray things as a design where the 2 drivers have the same offset... it could work great thou.
dave |
That was my attempt to come up with a narrow front baffle. #95 is a more accurate fold but I wonder if it's possible to make a psuedo-stand that is less than the width of the cabinet. |
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| dranreb&* |
I replaced my brine's internal wiring by a pair of cat5 it does improved over all . From the very begining my "bass" set up is +12 and +12 on the high(treble), but now I end up to +4 on the bass and +2 on treble on my AVR big improvement, though. And early yesterday I move my speaker from short wall to wide wall(and seeking for best placed),
big improvement as well on bass and improve sound stage and more livelier and dynamic. And my last tweak I put ceramic tiles on top of it about 8pcs both speaker(it's too heavy) and I'm surprised on the bass, its get tighter trust me to this. I remember Bob Brines recommend to double, the top panel or damping material(mine only used one tile), but my wife does'nt liked it :bawling: .Supposed to be, those ceramic tiles will be use on our terrace flooring, I'm just curious so I used it first ... hehehe.
And the last word I heard to my wife is... WHAT NEXT:smash: |
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| Timn8ter |
| quote: | | And the last word I heard to my wife is... WHAT NEXT |
A granite enclosure, of course! :D |
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| Timn8ter |
| If the goal is to have similar offsets of drivers then #95 is the way to do it. Were I to build this I would use a stand and have the port front or rear firing to reduce the visual impact. Thoughts? |
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| planet10 |
| quote: | Originally posted by Timn8ter
Thoughts? |
Got the sim?
I always figured terminus out the bottom was the least obtrusive
dave |
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| Variac |
I'm now thinking the straight line without any folds, and with the driver in the middle is prob going to be:
-easy to make
-most likely to match calcs.
-Perfect to lay on its side as a center channel
-Still could be extended with a false stand to raise the driver if a
tower format is desired.
-Easy to bolt back to back to create a BI pole
- All in all, a very nice modular unit!
Also, if the line terminates on the bottom, then the false stand requires it to be changed. I feel that the front port adds some interest to a very plain front |
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| Timn8ter |
| quote: | Originally posted by planet10
Got the sim?
I always figured terminus out the bottom was the least obtrusive
dave |
Courtesy Martin King's MathCAD worksheet |
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| Timn8ter |
| quote: | Originally posted by Variac
I'm now thinking the straight line without any folds, and with the driver in the middle is prob going to be:
-easy to make
-most likely to match calcs.
-Perfect to lay on its side as a center channel
-Still could be extended with a false stand to raise the driver if a
tower format is desired.
-Easy to bolt back to back to create a BI pole
- All in all, a very nice modular unit!
Also, if the line terminates on the bottom, then the false stand requires it to be changed. I feel that the front port adds some interest to a very plain front |
A straight BPTL would look similar to this. |
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| planet10 |
| quote: | Originally posted by Variac
-Still could be extended with a false stand to raise the driver if a
tower format is desired. |
And make a real tall, slim, elegant speaker... i was going to do a 3D model of this one last night, but instead got really frustrated trying to get martin's worksheets to generate anything useful for an Apexjr Super 8 :(
I've built a couple bi-pole 1197 centres along this theme that work really well (systems both use 4 1197 BD-pipes for mains & reares & a single push-push sub (one with Philips 12s, the other with Foster 12s -- the extended range bass drivers really do much better than "official" subwoofers in these aps)
dave |
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| planet10 |
| quote: | Originally posted by Timn8ter
A straight BPTL would look similar to this. |
as drawn we have put the drivers on what would be the sides of these boxes...
Note: the speakers Tim shows are inspiring... a real Frugal-phile(tm) delight (and giant killers)
dave |
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| Timn8ter |
| quote: | Originally posted by planet10
as drawn we have put the drivers on what would be the sides of these boxes...
Note: the speakers Tim shows are inspiring... a real Frugal-phile(tm) delight (and giant killers)
dave |
Ali's favorites too. She had a hard time deciding between these and the FE127E though. It will be interesting to see what tweaking the 127 leads to (I need new blades for my hobby knife). :devilr: |
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| x. onasis |
Oh no! Got the drivers this evening, immediately hooked a few up to break them in a little, started ripping up some MDF, and I take a little break, come here to find you're completely changing the project?
Oh well, "spin me around and smack me upside the head" as one of our more eloquent fellow posters once said. Serves me right to be in such a hurry.
VO.1 (plus 2") is what I've got going. No prob. I'll work on something that'll be appropriate. Anyone got the dims for Spires baffles? Thanks to Tim, those drivers will be here tomorrow. How long before Xmas?
And a real question: The threads dealing with break-in didn't help much. Any recommended procedure? And how long should we expect before we appreciate what these lovely little beauties will do? 300 hrs or so? |
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| x. onasis |
Tim, you can put a scalpel-sharp edge on a knife with 320>400>600 wet/dry sandpaper placed on a pane of glass.
(This is coming from someone with over a hundred $ worth of Japanese waterstones.) |
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| Timn8ter |
| quote: | | VO.1 (plus 2") is what I've got going. No prob. I'll work on something that'll be appropriate. |
There's nothing wrong with that, in fact, I was going to suggest that the CSA be reduced to 48" but a couple of inches of CSA doesn't seem to change the modeling. What it does do is invoke the mystical powers ala the "golden ratio". :wiz:
| quote: | | Tim, you can put a scalpel-sharp edge on a knife with 320>400>600 wet/dry sandpaper placed on a pane of glass. |
Great! Even on a broken blade? :D
V0.1 plus 2" courtesy of Martin King's MathCAD worksheet |
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| x. onasis |
Thank you for putting my mind at ease, Tim. This Santa's Helper will sleep better now.
Broken blade, huh? You'll laugh at this, but a tool I've had on my bench for decades is a broken sabre saw blade, fastened by a(tiny) screw and wire wrapped to a whittled, pencil-sized stick of hickory. It's a homemade x-acto knife, only longer, stronger, and sharper. That blade takes and holds a polished edge as well as my Marples chisels. |
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| planet10 |
| quote: | Originally posted by Timn8ter
V0.1 plus 2" |
These are the most recent posted both straight bi-pole & monopole, and folded monopole (folded bipole will need to be extended 1" at the bottom)
dave |
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| SCD |
Stands:
I am not a big fan of stands they are an additional project that often does not get done. If possible try to not require a stand. Most speakers that requie stands end up as bookshelf speakers that look to big. I think it is reasonably easy to integrate a stand into any design. The easiest way is to extend the sides, this allows for down firing ports. A good example is the design that GM did for Pea and his JS92 project.
To help off set the tippy look it is nice to oversize and bulk up the base. The material of choice for me is polished granite, but any othe material will also work. A doulbe layer of MDF or a MDF/sand/MDF sandwinch also works.
Sharp cutting blades:
I have carefully taken appart a new Bic razor and attached the blade to a thin piece of wood. This is real sharp. A spot of epoxy glue and a wrap of hockey tape did the job for me. I think it is sharper than a regular hobby knife. You may have to use a strip or belt sander to sharpen to a point.
Be real careful these blades are sharper than you think. Of interest if you can see the blade when looked straight down at it is dull.
Another design concept for the bipole:
Rather than folding the TQWP, it would be nice to mount one driver on the slant face @ 50% and on on the back face right behind it. This would reduce the off set issue and eliminate the need for a stand. A nice slot port in the front and a granite base would be my choice. Thoughts? |
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| Timn8ter |
| quote: | | Rather than folding the TQWP, it would be nice to mount one driver on the slant face @ 50% |
This is monopole but exemplifies the concept. |
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| SCD |
Thanks Tim
That is the one. I really like the presentation.
What are the #'s for a bipole in that design? |
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| SCD |
Fabulous Tim:
Driver @ 50% ?
Any stuffing needed to work that slight ripple? |
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| Timn8ter |
| Yes, driver at 50% port is centered 1.75" from the bottom. I modeled it with .25lbs per cu. ft. so there is room to add stuffing to taste. |
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| SCD |
Thanks Tim:
I am all over this one.
I Should have a prototype made by the end of the weekend. |
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| x. onasis |
If you hold the drivers in you hands while playing sub-200Hz tones and press the magnet covers back to back you'll easily hear that coupling them mechanically, clearly reduces harmonic resonances of the baskets themselves. In free air, it sounds like awful distortion. While playing with finding the pressure needed to accomplish this, I've found that its somewhere between 1/2 and 2 lbs of pressure, and definately needs to be dialed in.
In other words, I don't think you can reliably just cut a dowel close to size and glue it in with a removable caulk.
I have some circular pieces left over from three inch driver cutouts about the same size as the magnets, these make a nice block to screw to a dowel or short 2"x2". The other end of the dowel gets predrilled and fitted with a T-nut fastener. You can then use a threaded rod and lock nuts to adjust the pressure in your test fit.
If you don't want to deal with cutting and filing a threaded rod, you can use anchor fasteners (sometimes called Threaded dowels) these are bolts with no heads, lag screw thread on one end (directly into the dowel) and machine thread on the other.(Into the T-nut)
To make this assembly semi-permanent/removable I'm thinking silicone to one driver and ductseal to the other. Any thoughts?
And has anyone worked out a final measured drawing of their preferred "reference" for our common group build? |
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| gmilitano |
I finally got some time to play with v0.2 of the design and the MJK MathCAD software some more.
The mono-pole, bi-pole parallel and bi-pole series have essentially the same frequency response, with the exception that the parallel is about +6db in sensitivity.
I was supprised to see that the mono-pole and bi-pole series have the same response. I would have expected more bass out of the bi-pole. Is there any reason why this is the case?
For tube amps, I like the idea of an extra 6dB that you get with the parallel connection. However, I don't know if most tubes amps can handle the very low impedance (<3.5 ohm!)
Cheers,
Gio. |
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| Timn8ter |
1. Regardless the number of drivers the Fs is still the same.
2. The worksheets do not account for baffle step.
3. Most amps, tube or SS will perform better with a higher load. Tube amps tend to be more sensitive to load then SS. I found that having two FE103E in series sounded cleaner than parallel even when driven by the little S5 amp which is rated for 4 or 8 ohm loads by the designer. |
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| planet10 |
| quote: | Originally posted by gmilitano
For tube amps, I like the idea of an extra 6dB that you get with the parallel connection. However, I don't know if most tubes amps can handle the very low impedance (<3.5 ohm!) |
GM -- you need to shake the brain-washing... :)
For a tube amp with proper taps you will get the 3 dB of extra sensitivity whether you connect in series or parallel... 6 dB is an artifact of MJK assumming everyone is using a SS amp with high damping (1/2 of the 6 dB gain from parallel is from assumming that the SS amp doubles its power into 4 ohms and -3 dB in the case of the series connection comes from the SS amp putting out half as much power into 16 ohms. (ie the 6 dB difference between parallel & series is purely that into 4 ohms the amp is providing 2 W & into 16 ohms a 1/2 W -- this is a completely false assumption if you have a tube amp)
dave |
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| gmilitano |
| quote: | Originally posted by Timn8ter
1. Regardless the number of drivers the Fs is still the same.
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I went through the design some more and read over the MJK two driver doccument. The actual reason may be that each driver in a bi-pole system has 1/2 the displacement of the driver in the mono-pole version.
In going through the mono-pole and bi-pole design, I discovered that the volume of port on the bi-pole is not double that of the mono-pole design.
The bi-pole port radius should be SQRT(2 * 0.75) = 1.225". I have attached a MJK mathCAD simmulation of the larger port.
I don't know if a 1.25" port can be attained, therefore, one may have to use two 0.75" ports. The two ports would work nicely out the bottom. A while back, Dave had a nice plan for the 40-1197.
http://www.diyaudio.com/forums/show...0693#post390693
Perhaps we can incorporate this stand in the design to get the desired driver height and the twin ports out the bottom.
Regards,
Gio. |
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| Timn8ter |
| quote: | | I don't know if a 1.25" port can be attained, therefore, one may have to use two 0.75" ports. The two ports would work nicely out the bottom. A while back, Dave had a nice plan for the 40-1197. |
Of course you mean a 2.5" diameter port or two 1.25" diameter ports, don't you? Actually you should be increasing the volume of the port rather than just the diameter. In the dims I gave to SCD I suggested a 2" diameter port.
If a driver is capable of a theoretical LF output limit of 50Hz that is all it will produce regardless whether there is one, or a dozen. With an increase in the number of drivers you will experience a corresponding increase in SPL but not lower frequency response. |
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| gmilitano |
| quote: | Originally posted by Timn8ter
Of course you mean a 2.5" diameter port or two 1.25" diameter ports, don't you? Actually you should be increasing the volume of the port rather than just the diameter. In the dims I gave to SCD I suggested a 2" diameter port.
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Yes and no. The mono-pole uses a port with radius of 0.75", diameter of 1.5". For the bi-pole, the port diameter should be the SQRT (0.75 * 2), which is 1.225". The bi-pole should use either a single port with radius of 1.25", diameter of 2.5" or use two of the ports used in the mono-pole design (two 1.5" diameter by 2" length).
I am thinking that the bi-pole should be double the mono-pole. I don't see why the volume of the enclosure would be exactly double, but not the volume of the port.
Gio. |
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| gmilitano |
| quote: | Originally posted by planet10
GM -- you need to shake the brain-washing... :)
For a tube amp with proper taps you will get the 3 dB of extra sensitivity whether you connect in series or parallel... 6 dB is an artifact of MJK assumming everyone is using a SS amp with high damping (1/2 of the 6 dB gain from parallel is from assumming that the SS amp doubles its power into 4 ohms and -3 dB in the case of the series connection comes from the SS amp putting out half as much power into 16 ohms. (ie the 6 dB difference between parallel & series is purely that into 4 ohms the amp is providing 2 W & into 16 ohms a 1/2 W -- this is a completely false assumption if you have a tube amp)
dave |
I hope I am not being brain washed! If so, here is your turn!
Ok, I think I got most of your comments.
What do you mean by a "tube amp with proper taps"?
To summarize what you have said, if one uses a tube amp to drive this bi-pole, the sensitivity will be about 93dB regardless of weather it is wired series or parallel.
Cheers,
Gio. |
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| Timn8ter |
| quote: | | The bi-pole port radius should be SQRT(2 * 0.75) = 1.225". I have attached a MJK mathCAD simmulation of the larger port. |
Yes, that's the correct formula. Something strikes me odd about using a 2.5" port though. The modeling shows little difference other than slightly lower port velocity and slightly higher box tuning. |
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| planet10 |
When Tim specified the bi-pole he gave a 2" port... for the monopole i divided the area in half, it came out to 1.4x something diameter so i just rounded it to 1.5" since that is a standrad size in NA... it may need to be a tad longer because of that approximation.
Until someone actually builds them, the port size is really just a close approximation.
dave |
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| planet10 |
speaking of monopole... here is the up-to-date round-top folded monopole....
dave |
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| planet10 |
| quote: | Originally posted by gmilitano
What do you mean by a "tube amp with proper taps"?
To summarize what you have said, if one uses a tube amp to drive this bi-pole, the sensitivity will be about 93dB regardless of weather it is wired series or parallel. |
Tube amps have taps on there output transformers, typically at least 4 & 8 ohm, or 8 & 16 ohm (or 5 & 10 ohm on some older German OPTs). The idea is to connect the speaker to the one that is closest to your speaker. Now if your speaker doesn't correspond to the right tap (ie a 16 ohm speaker on an 8 ohm tap) you will get a little less power (in the case of the example shown usually a little less distortion also), but in the end the power output differences between taps is usually not all that great, and the best way to determine which one to use is the one that sounds best.
Yes... real sensitivity of 2 speakers in parallel or series will be 3 dB greater than a single one. And tube amps (and most SS amps for that matter) are happier with higher impedance (it is just that the SS amp typically puts out less maximum power -- ie it has a relatively more robust power supply just by changing speaker impedance)
dave |
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| Optical |
I have two questions:
First, is the purpose of this reference speaker simply for doing A/B test with other speakers. Or to provide a flat full range response?
Personally i would prefer a reference speaker with a flat response to compare others to, rather than a speaker modelled to sound 'good'..
Secondly, does anyone know where to get Fostex drivers in New Zealand?
Thanks guys, keep up the good work
Matt |
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| jeremyg |
| quote: | Originally posted by planet10
speaking of monopole... here is the up-to-date round-top folded monopole....
dave |
I think i may give these a go next weekend...got some time on my hand...now this is basically my first DIY home audio project. Sence it looks "cute" according the the boss....i got the approval..so with that...i had one question...would anyone have any recommendations on stuffing...as in how much and where exactly.
thank you |
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| Timn8ter |
| quote: | Originally posted by Optical
I have two questions:
First, is the purpose of this reference speaker simply for doing A/B test with other speakers. Or to provide a flat full range response?
Personally i would prefer a reference speaker with a flat response to compare others to, rather than a speaker modelled to sound 'good'..
Secondly, does anyone know where to get Fostex drivers in New Zealand?
Thanks guys, keep up the good work
Matt |
I believe the suggested designs in this thread provide an adequate standard to base future builds against when taking price, performance and construction requirements into consideration. |
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| MarkMcK |
Greetings full rangers,
I would like to follow up on Matt's (optical) first question. How are you using the word reference?
By the dictionary definition of the word "reference," you don't have to have flat response. Still, it ought to be a known quantity or quality.
This is, however, different from the way "reference" has been used in ad copy to refer to certain loudspeakers. There the reference to reference has implied superior performance (flatness or whatever).
This brings me to the driver selected by the vote of I believe seven people. One of the voters made the comment about a preference for shielded if the shielded and unshielded versions had the same performance. I have not tested the FE126E or the FE127E. I can only comment on what is listed in the spec sheets. From the spec sheets, however, the drivers are not the same. The motors (magnets and BL) are significantly different. The 126 uses a 440 gram ferrite magnet, the 127 uses a 100 gram ferrite magnet. The 126 has a specified BL of 5.92, the 127 is only 4.14. The 126 is rated at 93 db and the 127 is rated at 91 db.
The published frequency responses of the two drivers are also different. The 126 appears to be up as much as 3 or 4 db between 500 and 7 kHz above the 2 db lesser sensitivity of the 127.
In addition, even Fostex's rather smoothed response graphs show two drivers that do not meet rated response bandwidth even with a plus or minus five db range. For example, both drivers' output is falling fast above 15 to 17 kHz. The two drivers are also significantly different in output between 500 and 7 kHz.
As I already stated, I do not have access to either the 126 or the 127. I do have access to the FE103E. I do know how an engineering quality frequency response test of the FE103E compares with the Fostex published response of the FE103E. While I will not know for certain unless I test, I have little reason to expect that Fostex changed their test set up just for the 126 and 127 drivers. (As an aside, I love the way Fostex changes the vertical sizes of their published graphs. Makes it so much easier to compare frequency response differences from driver to driver.)
Now, I have a one-time proposition for the thread and the thread contributor who owns a company that sells the FE127E. If you will donate a driver, I will test the driver and publish the response in this thread. In addition, I will build the monopole TL box and test the box and the driver.
I do have some experience testing TL designs. I published a couple of reviews of Fried's TL loudspeakers during the 1980s. And I still have the data in a digital format that I can access to use as a TL reference. I also have a reference four-inch driver that I can compare to the 127 in the exact same test set up.
Good designing and good building,
Mark |
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| falcott |
| quote: | Originally posted by Optical
... does anyone know where to get Fostex drivers in New Zealand? |
Hi Matt,
Syntec in Auckland is the Fostex agent. Ph 263 9885. I spoke to Conrad when I phoned recently with an enquiry about drivers.
:) |
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