| gmilitano |
Has anyone given some thought to the idea of a diyAudio Full Range Reference Project and groupbuy?
My thoughts were:
A modestly priced driver. Say the FE103/107 or FE126/127. The 40-1197 would have been a strong canidate if it was readily available.
The enclosure would be a simple t-line or folded pipe with dimensions that would allow the use of standard boards so that the woodworking was not scarry.
A simple BSC, a well documented webpage and of course rhe friendly and knowledgable in the forum.
This way, several of use could compare speakers to this reference project and discuss.
Anyway, it is just a thought.
Regards,
GM. |
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| planet10 |
Not a bad idea... the FE127 seems a nice balance between bass & top... Tim Forman has been playing with them...
My preferred BSC is bi-pole :^)
dave |
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| Timn8ter |
I think having a bipole FE127E folded pipe would be a good one. I know this takes away from one of the goals which is to describe a method for designing a BSC circuit. Perhaps the challenge would be to build a BSC circuit that could rival the bipole method used in the reference project. After all, the purpose of a reference project is to set a high bar that future builds are compared against, correct?
These are the initial numbers I come up with using Martin King's MathCAD worksheet .
L=40"
zDriver = 20"
zPort = 38"
So = 6.5" x 1.5"
SL = 6.5" x 12"
Density = .25
rPort = 1.5"
Lport = 4.0"
Driver parameters were taken from the published Fostex numbers and the drivers are wired in series. |
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| gmilitano |
| quote: | Originally posted by planet10
Not a bad idea... the FE127 seems a nice balance between bass & top... Tim Forman has been playing with them...
My preferred BSC is bi-pole :^)
dave |
The BSC would help keep costs down and could serve as a BSC primer course for new builders.
A bipole 126/127 would be in the price range of a 166/167 and 206/207. At that price would a single 166 or 206 be money better spent?
I love the idea of the GM-ML Voigt
http://www.diyaudio.com/forums/show...9120#post519120
It can be very sharp looking and the use of standard size boards makes it an attrcative project for those who are not expert wood workers.
Perhaps something similar to the GM-ML Voigt with a FE103/107 or FE126/127 with BSC is a good idea.
Cheers,
GM. |
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| Timn8ter |
| quote: | | A bipole 126/127 would be in the price range of a 166/167 and 206/207. At that price would a single 166 or 206 be money better spent? |
This causes many builders to shy away from bipoles. The advantage of the FE167E for the same price would be a gain of 10Hz lower BR at the cost of a larger cabinet. The reduced cabinet resonance and better bass control is gained in the bipole configuration along with increased power handling and increased SPL output. |
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| gmilitano |
| quote: | Originally posted by Timn8ter
This causes many builders to shy away from bipoles. The advantage of the FE167E for the same price would be a gain of 10Hz lower BR at the cost of a larger cabinet. The reduced cabinet resonance and better bass control is gained in the bipole configuration along with increased power handling and increased SPL output. |
I don't understand how a bipole configuration provides equal increase in SPL across the entire frequency range. I would guess that the SPL increase in HF responce at the listening postion would be much less than the LF responce.
I would also think that the placement of a bipole in a room would be more critical, making it less versatile as it may not be suitable for some rooms.
Of course, these are just my thoughts. I have never actually heard a bipole.
Regards,
GM. |
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| planet10 |
| quote: | Originally posted by gmilitano
I don't understand how a bipole configuration provides equal increase in SPL across the entire frequency range. I would guess that the SPL increase in HF responce at the listening postion would be much less than the LF responce. |
actual on-axis SPL is the same at mid frequencies as a monopole, but there is no need to slice 3-6 dB off that for baffle step. The power response is doubled, and is uniform unlike a monopole. No ugly reative BSC components means a happier amplifier.
| quote: | | I would also think that the placement of a bipole in a room would be more critical, making it less versatile as it may not be suitable for some rooms. |
true... but not as critical as you might think... if you need a BSC circuit you aren't that close to the back wall anyway, a bi-pole will probably work fine
| quote: | Of course, these are just my thoughts. I have never actually heard a bipole.
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I was skeptical at 1st to. Now i'm a convert.
dave |
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| gmilitano |
| quote: | Originally posted by planet10
actual on-axis SPL is the same at mid frequencies as a monopole, but there is no need to slice 3-6 dB off that for baffle step. The power response is doubled, and is uniform unlike a monopole. No ugly reative BSC components means a happier amplifier.
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This is what I was thinking, the monopole and bipole would have the same on-axis SPL at mid to high frequencies. I guess what I don't understand is why the monopole would require a BSC and the bipole would not if the on-axis SPL at mid to high frequencies is the same for both configurations.
| quote: | Originally posted by planet10
I was skeptical at 1st to. Now i'm a convert.
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The unfortunate part is that I will likely have to build a pair for myself to have a listen.
Cheers,
GM. |
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| planet10 |
| quote: | Originally posted by gmilitano
This is what I was thinking, the monopole and bipole would have the same on-axis SPL at mid to high frequencies. I guess what I don't understand is why the monopole would require a BSC and the bipole would not if the on-axis SPL at mid to high frequencies is the same for both configurations. |
Because in the monopole, the bass (ie below baffle-step) has as much as 6 dB less SPL than the bi-pole. The BSC circuit chops this (up to) 6 dB off the mid/highs so that they are equal to the lows. In a bipole there is no baffle-step.
Once a BSC filter is added the monopole has up to 6 dB less SPL than the bipole.
dave |
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| gmilitano |
Ok, I have been sold on the bipole. The increased SPL would be nice for those who have low power tube amps.
In addition to the FE127 bipole, perhaps a bipole W3-871S may also be an option.
The cost would be much lower with the TB driver. However, the TB driver has a relatively high Fs ~110Hz.
GM. |
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| planet10 |
| quote: | Originally posted by gmilitano
n addition to the FE127 bipole, perhaps a bipole W3-871S may also be an option.
The cost would be much lower with the TB driver. However, the TB driver has a relatively high Fs ~110Hz.
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871 has Fs more like 135 Hz... how about the Mark M modified TB?
I do have an Adire AV3 bi-pole in the works... (it may need a T thou)
dave |
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| Variac |
I'd say the most important thing is to standardize on the driver, not the configuration. That way one could buy say 4 or 6 drivers, and try out bi-pole or BSC filter, transmission line or reflex, etc..
Multi channel or stereo
All for the cost of a couple of sheets of MDF. |
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| Variac |
The Fe 127 is $36.50 at Madisound
-How much (and where) is the Tangband? |
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| Timn8ter |
| quote: | Originally posted by Variac
The Fe 127 is $36.50 at Madisound
-How much (and where) is the Tangband? |
Parts Express
$17.07 each for 1 to 3 units
$16.04 each for 4 + units plus shipping of course. |
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| planet10 |
| quote: | Originally posted by Variac
The Fe 127 is $36.50 at Madisound
-How much (and where) is the Tangband? |
W3-881S at Parts Express.
dave |
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| Lionel |
| quote: | | I'd say the most important thing is to standardize on the driver, not the configuration. |
Hi,
Considering the above don't you think that it would be difficult to standardize on a modified driver ? :xeye: :xeye:
I'd say that in the case of a reference speaker, an "unmodified" Fostex (or other) driver would be a better choice.
Lionel |
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| planet10 |
The Mark M 881 is really more classed as a mid-tweeter (and i got some to try), but for a reference broject, something with a better bottom to top balance is probably called for... i think that the FE103 or FE127 are the best candidates to my mind... there are more expensive drivers that cover the range, but, like the 2-way reference already established, i think a modestly priced driver for a modestly priced system is appropriate.
And as has been demonstrated -- at least with the FE103 -- there are a wide variety of cabinets that work. With the FE103 there is also a whole family of variants to make things richer.
dave |
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| planet10 |
| quote: | Originally posted by Timn8ter
Bipole 103? |
That was one of the speakers in my mind.... the Solo 103 another.
dave |
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| SCD |
Hello Guys:
This is just the thread I was hoping would get going. I have a nice little pile of lumber in my shop that is in need of a project. I was planning on doing this very thing myself.
I think the concept of deciding on the the driver is the one that should be concluded first. I think there are three to chose from. The FE103, FE127, RS1197. All are reasonably priced. The reputation of all three is good. There are proven designs as well. They are all reasonably sensitive. It is always possible to have build cabinet designs for all three and have a shoot out. Hmmmmm that might be a good reason for another get together. I already have a few 1197, and a set of FE103A I just need a set or two of Fe127 to get going |
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| Timn8ter |
Unfortunately the 1197s are a challenge to come by for many people unless someone is willing to disperse their stockpile :D .
Have we eliminated the modded TB 881? Kinda sounds like it. That would leave the FE103E and the FE127E. I love the lower Fs of the FE127E so that would be my first choice. I do like the idea of the Solo 103 because it's already out there and is an easy and accessible project for most everyone. So my vote is..
1. FE127E
2. FE103E
:) |
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| 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.
Altho I like Dave's suggestion of solo or Bi 103's, the idea of just keeping the price low, might produce only average results. When you factor in the effort and expense of bringing the cabinets to finish, the price of the drivers might eventually be forgotten. That said I applaud GM for starting this thread, and everyone for participating.
OK-on to my questions:
Tim, as the cost is about the same, how does the Bi-103 compare to your mini-array 871S ?
As we look at the 167 and 207 or 4 127's their prices compare to the new offerings at Adire and CSS.
What do you guys who've heard them think? Should we be considering the Extremis or CSS XBL, or am I missing the point of this thread?
Are we limiting ourselves to easier-to-build cabs?
What could tip the scales here, a great deal on a group buy? Can anyone get a deal on Fostex in quantity? |
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| SCD |
Good thoughts x. onasis:
I have heard the CSS XBL and was impressed. I was also impressed with the fe127. I think it would be interesting to work up a desgn for the CSS driver as it is new to the market and seems to have a great deal of promise. The Fostex drivers have a proven track record that is very reliable. So do we stick with the known or try the new. Perhaps the group buy price will help to make the final decision.
Perhap we need to keep the prime directive in mind here, we can easily get lost in dreamland and suffer from paralysis by analysis.
So what was the prime directive again? What is the objective of the project. To develop a fullrange reference project for a reasonable price or something like that. |
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| Timn8ter |
| quote: | | Tim, as the cost is about the same, how does the Bi-103 compare to your mini-array 871S ? |
I'm not sure which mini-array you're referring to. If it's the one with the 6 W3-871S on top of the 2 W5-704s the price isn't even close. I also don't believe it meets the criteria of this project. If you're referring to the small 4 driver array I scraped that project long ago. That was a pre-Spires design that CSS did a better job with. IMHO, arrays have their place but I would prefer to see this project stay as close to single-point source design as possible to demonstrate the ability of a full-range to deliver an excellent soundstage. If the group wants to do a low-cost line array I can't think of anything much better (price/performance) than the CSS Spires. |
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| gmilitano |
| quote: | Originally posted by Timn8ter
Unfortunately the 1197s are a challenge to come by for many people unless someone is willing to disperse their stockpile :D .
Have we eliminated the modded TB 881? Kinda sounds like it. That would leave the FE103E and the FE127E. I love the lower Fs of the FE127E so that would be my first choice. I do like the idea of the Solo 103 because it's already out there and is an easy and accessible project for most everyone. So my vote is..
1. FE127E
2. FE103E
:) |
Fostex seems to provide a reasonable compromise between cost and performance. In addition, they are popular, well documented by Fostex and others.
If we go bipole, FE103 and FE126/127E would be options to try keep costs down.
Tim, is there a reason you prefer the 127 over the 126?
For a monopole project, we could go for lower costs with the FE126/127E. However, the FE166E and FE206E can also be considered at costs similar to the bipole option.
For projects, I also like the Solo103, however, the woodwork does not look that straight forward.
A slim T-line is always attractive in my mind.
As mentioned previously, the idea of the GM-Voigt looks like a nice project. I like the idea of common wood sizes to simplify the woodwork. The FE127E in a folded voigt may be an option.
Somethings that I would like to see this project have are:
1. Unmodified drivers. Reversable modifications may be okay as they can likely be reproduced well between builders.
2. Try keep total driver costs below about $180US.
3. Relatively simple woodworking so not to scare off potential builders.
4. Low power/tube friendly designs.
Anyway, for the time being, we should concentrate on drivers. My suggestions are (in no order): FE126/127E (bipole?), FE166E, FE206E.
I don't know if Fostex plans to keep the FE103E around.
I prefer the FE166E and FE206E over the FE167E and FE207E. |
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| Timn8ter |
| No particular reason to use the FE-**7E drivers if the shielding is not needed. |
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| SCD |
Hello Guys:
Is there a performance diference between the Fe??7 driver and the FE??6 drivers. I thought they were the same except for magnetic shielding.
If that is the case then it does not really matter. I already have a Fe167 project completed so I am leaning toward the FE127 as a mono and a bipole. Both are pretty simple to build and the cost is not too bad.
TQWP or MLTL or folded TQWP all of these work for me. |
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| gmilitano |
| quote: | Originally posted by SCD
Hello Guys:
Is there a performance diference between the Fe??7 driver and the FE??6 drivers. I thought they were the same except for magnetic shielding.
If that is the case then it does not really matter. I already have a Fe167 project completed so I am leaning toward the FE127 as a mono and a bipole. Both are pretty simple to build and the cost is not too bad.
TQWP or MLTL or folded TQWP all of these work for me. |
The Fe??7E driver are sheilded while the FE??6 is not. All of the Fe??7E drivers seem to have a higher Q, which makes them less suitable for a horn.
In my mind,
The 107 FR looks better than the 103
The 126 has rising FR, and less bumps. The 127 has a few more bumps but the FR does not rise, however, the impedence rise is about 4ohm higher
The 166 and 167 look very similar.
The 207 is 1dB less efficient and does not have the HF that the 206 has. A super tweeter may be needed with the 207.
That being said, I prefer the FE??6E, unless several people see the necessity for shielding.
Cheers,
Gio. |
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| gmilitano |
| quote: | Originally posted by x. onasis
As we look at the 167 and 207 or 4 127's their prices compare to the new offerings at Adire and CSS.
What do you guys who've heard them think? Should we be considering the Extremis or CSS XBL, or am I missing the point of this thread?
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My Fostex suggestions are just ideas. The nice thing about Fostex is that it is available in several different countries.
I like the idea of a reference project being feasible for as many people as possible.
Gio. |
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| Variac |
| I agree we should stick with Fostex so availability isn't an issue worldwide. |
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| SCD |
Well it looks like we have gone half way arround the block today discussing this one. It seems we are very close to coming up with a driver. I am not sure how long we want to debate the choice of the driver or if there might be anyone else interested in this part of the discussion.
I put forward that we go with the Fe127 and begin discussion about the enclosure. |
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| Timn8ter |
| The Extremis is not a full range driver. The CSS WR125S is an XBL^2 based full range driver that sells for $138 per pair. I guess I was a little slow on the response. My vote is already cast. :xeye: |
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| planet10 |
The CSS is a nice driver... a little shy on top... not as tube friendly and quite a bit more $$$ -- it is really more in competition with the Jordan JX92 (giving up some top to get better bottom)
As to Tim's Bi-103s vrs his woofer assisted 871 towers, his Bi-1197s (budget FE103s) cleaned their clock.... the 103s should only be better.
dave |
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| Timn8ter |
| quote: | Originally posted by planet10
The CSS is a nice driver... a little shy on top... not as tube friendly and quite a bit more $$$ -- it is really more in competition with the Jordan JX92 (giving up some top to get better bottom)
As to Tim's Bi-103s vrs his woofer assisted 871 towers, his Bi-1197s (budget FE103s) cleaned their clock.... the 103s should only be better.
dave |
Oh sure, if you like depth and detail :D . |
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| Timn8ter |
It would appear that it's a contest between the FE103E and the FE126E since no one has seen a need for shielding. I vote for the FE126E. Sorry Dave. :)
Shall we have an official vote? |
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| x. onasis |
I think shielding is good....and wasn't the 127E your first choice?
I get confused easily. Thanks for helping me out. You guys decide. I'm still excited.:) |
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| SCD |
I happen to like shielding to. If it does not diminish performance or increase cost, it does increase location options. I vote for shielding.
You can never be too safe after all
Fe127 |
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| gmilitano |
I also prefer the FE126E/FE127E over the FE103E/FE107E.
I do not have sheilding requirements, so I prefer the FE126E.
Here are links to the 126 and 127 specifications:
http://www.fostexinternational.com/.../pdf/fe126e.pdf
http://www.fostexinternational.com/.../fe127erev2.pdf
Quick Summary:
FE126E
Fs=70Hz, Re=6.9, Qts=0.25, SPL=93dB
FE127E
Fs=70.4, Re=6.5, Qts=0.43, SPL=91dB
I like the extra efficiency of the 126 which is good for those who may want to use a tube amp. The 127 is pretty flat to 6k and then has a couple of bumps. The 126 does not have big bumps, but shows increasing SPL with increasing frequency. Does anyone think that the 126 may be a tad bright? The HF response looks good on both drivers.
My vote is for the 126, unless people think it may be on the bright side.
Regards,
Gio. |
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| Timn8ter |
| quote: | Originally posted by x. onasis
I think shielding is good....and wasn't the 127E your first choice?
I get confused easily. Thanks for helping me out. You guys decide. I'm still excited.:) |
Ok, I go for shielding too. So three votes for the FE127E and one for the FE126E, right?
:judge: |
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| planet10 |
| quote: | Originally posted by Timn8ter
I vote for the FE127E. Sorry Dave. :)
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You needed to read between the lines, my 1st choice is the 127 -- the 126 has too low a Q to use in anything but a horn (but it does have an extra couple dB sensitivity)
dave |
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| planet10 |
For comparison here is FE126 (black) vrs FE127 (purple) factory FR & impedance
dave |
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| Timn8ter |
Or just remember which lines I read.
| quote: | Originally posted by planet10
Not a bad idea... the FE127 seems a nice balance between bass & top... Tim Forman has been playing with them...
My preferred BSC is bi-pole :^)
dave |
That would be four for the FE127E and one for the FE126E.
:judge: |
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| Variac |
The 127 would allow use as HT spkrs of course, which is certainly
useful... So 127 it is ? |
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| Josephjcole |
127 does seem like a good choice. My friend has asked me to build her a set of speakers, so she might just get a pair of 127's;). Although just to add my two cents, I would prefer not to go bi-pole since this would double the cost. Maybe I'm just a cheapskate thou':rolleyes:
Joe |
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| Timn8ter |
6 for the FE127E and 1 for the FE126E
:judge: |
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| gmilitano |
| quote: | Originally posted by planet10
You needed to read between the lines, my 1st choice is the 127 -- the 126 has too low a Q to use in anything but a horn (but it does have an extra couple dB sensitivity)
dave |
I like the FR and extra couple dB sensitivity of the 126. However, I was wondering about the low Q and thinking it may be a tad bright.
The 127 has a couple more peaks and dips, but shielding makes it more versatile.
I will be happy with either one.
The 127 is about $1 more than the 126 so price difference does not really matter.
It looks like we are leaning towards the FE127E.
I say we move on to selecting an enclosure.
I like the idea of a slim rectangular ported box with the driver located about 36" off the ground.
My reasoning, slim is attactive and would likelky pass a wife test. Rectangular is easy to build, and 36" seems like a reasonable ear height when sitting.
I also think we should try cover as much of the sound spectrum as possible so a bipole would enable us to increase the low end.
Regards,
Gio. |
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| gmilitano |
| quote: | Originally posted by Josephjcole
127 does seem like a good choice. My friend has asked me to build her a set of speakers, so she might just get a pair of 127's;). Although just to add my two cents, I would prefer not to go bi-pole since this would double the cost. Maybe I'm just a cheapskate thou':rolleyes:
Joe |
Initially, I had the same thoughts. However, a BSC complicates the project significantly. I have the feeling that the BSC would be amplifier dependent with SS amps requiring higher resistance than a tube amp. In that case, you can argue that it may not be a reference project.
The bipole does a couple of things. It gives more low end and increases the SPL making the project tube friendly.
Anyway, my 2 cents.
Gio. |
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| Variac |
| Now that it appears we have a driver, maybe we should all post links to projects that use the 127 or similar fullrange driver, and think about them. There is no reason we have to do only one design. In fact I propose we first do 2 designs- a bipole, and one with a single driver. Maybe they are basically the same design - one with BSC filter, one with 2 drivers and a bigger box. Or maybe each completely different |
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| planet10 |
I see no reason not to have a single driver & a double driver version -- we are only talking about doubling the volume...
36" to the driver almost for sure makes this a stand-mounter (or a fake bottom)
dave |
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| Timn8ter |
I'm just going to throw out some numbers then I have to get back to gluing up some cabinets.
Internal cab dims for bipole: 30"H x 6"W x 8"D. 2" dia port 2"L.
Driver should be near the middle of the line as much as possible.
Opinions? |
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| planet10 |
Here is v0.1 drawing of Tim's suggested ML-TL. Since it has the driver a 50% this could be elegantly folded -- particularily interesting for the monopole version... i'll have to dig out Denson's paper and do it mathematically proper instead of the usual guess & by golly method.
dave |
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| gmilitano |
Wow. This is progessing much faster than I would have imagined.
With regards to the enclosure, I think we should try get as much as possible i.e low end out of the driver. In that regard, is a dipole double bass reflex box a possibility?
Gio. |
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| planet10 |
| quote: | Originally posted by gmilitano
In that regard, is a dipole double bass reflex box a possibility?
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You won't get more bass than can be had out a quarter-wave resonator, and a dipole BR -- by its very nature -- will get NO bass. Are you sure you don't mean bi-pole?
The only point of a BR would be to get a box that is shaped much closer to a cube.
dave |
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| gmilitano |
| quote: | Originally posted by planet10
You won't get more bass than can be had out a quarter-wave resonator, and a dipole BR -- by its very nature -- will get NO bass. Are you sure you don't mean bi-pole?
The only point of a BR would be to get a box that is shaped much closer to a cube.
dave |
Yes, I did mean bi-pole! :) |
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| ScottG |
Monkey-works time!
Why not use a combination of an omni with direct raditor? This way you could get a LOT more bass at less cost WITH-OUT a crossover - allowing 16 ohm or 4 ohm impeadance (assuming both drivers are 8 ohms). Additionally you'll be able to use the BEST driver for the money for your upper-mids and tweets and perhaps even shape the rear of this driver for better sound. |
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| BTW |
| quote: | Originally posted by planet10
You won't get more bass than can be had out a quarter-wave resonator, and a dipole BR -- by its very nature -- will get NO bass. Are you sure you don't mean bi-pole?
The only point of a BR would be to get a box that is shaped much closer to a cube.
dave |
Hi Dave,
Have you compared a bipole version( 2 opposite drivers in phase) vs dipole(2 opposite drivers out of phase). Friends and I just put together a 2 pairs of Coral Flat 8 in a BR box and the result was most interesting. The bipole had good bass and midrange was a wee bit cloudy and slight boxiness. In the dipole, wow huge soundstage but centre fill wasn't that good. Maybe because of the almost isobarik type loading the clarity and highs also improved quite a bit. We then tried reducing the high frequency from the rear driver, the centre fill did improve quite a bit and btw the dipole version had less bass.Still experimenting but dipole with subwoofer seems like a good solution. |
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| x. onasis |
BTW, Help me understand you. Could the effects you noted be remnants of the cancellation inherent in dipole speakers in general? I'm sure I don't understand, but my first thought is that this is exactly the opposite of what we're trying to do by going bipole in regard to BSC, and the effect you liked (soundstage) is what the OB rage is about.
Scott, Come again? This time for us dummies. Please?
Dave, "Elegantly folded"? I like the sound of that. What sort of bass are we expecting? I'm imagining a rather deep, narrow box that's only about 18-24" tall sitting on it's own matching sub for a stand. Go ahead, tell me the sub won't be necessary. |
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| gmilitano |
| quote: | Originally posted by planet10
Here is v0.1 drawing of Tim's suggested ML-TL.
dave |
Assuming that Zport = 28.5 in and a density of 0.3 lb/ft^3, I get the attached response.
I would estimate -6dB @ 50Hz and -3dB @ 70 Hz.
Is it possible to get a little more out of the low end?
Gio. |
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| BTW |
| quote: | Originally posted by x. onasis
BTW, Help me understand you. Could the effects you noted be remnants of the cancellation inherent in dipole speakers in general? I'm sure I don't understand, but my first thought is that this is exactly the opposite of what we're trying to do by going bipole in regard to BSC, and the effect you liked (soundstage) is what the OB rage is about.
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Yes, I think the big soundstage effect is due to the dipole, "open baffle" type effect. The speaker box we did had 2 pair of terminals each so we could try bipole, dipole, 4 ohm, 16 ohm,... connections etc. We did some swaping around and dipole consistently gives biggest soundstage with least bass and sure does sound very OB like. Actually we were quite surprised by the dipole result, our orginal idea was to see how much the bipole would eliminate the baffle step problem. The dipole arrangenent was done just for kicks and were we surprised. :bigeyes: |
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| planet10 |
| quote: | Originally posted by gmilitano
estimate -6dB @ 50Hz and -3dB @ 70 Hz. |
70 Hz was about what i was gonna guess before i saw your chart -- not bad for a 5" ... try lengthening the port a bit.
dave |
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| planet10 |
| quote: | Originally posted by BTW
Have you compared a bipole version( 2 opposite drivers in phase) vs dipole(2 opposite drivers out of phase). Friends and I just put together a 2 pairs of Coral Flat 8 in a BR box and the result was most interesting. The bipole had good bass and midrange was a wee bit cloudy and slight boxiness. In the dipole, wow huge soundstage but centre fill wasn't that good. Maybe because of the almost isobarik type loading the clarity and highs also improved quite a bit. We then tried reducing the high frequency from the rear driver, the centre fill did improve quite a bit and btw the dipole version had less bass.Still experimenting but dipole with subwoofer seems like a good solution. |
You are confusing me here... 2 drivers wired out of phase in the same box?
Are the magnets of the 2 drivers mechanically connected?
dave |
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| Variac |
So a folded trans line would allow the driver to be at the top?
Seems a lot more practical.
Whoops, maybe that's my wants being expressed. I was thinking that the best form factor is small towers about 40" tall with the driver up near the top centered at about 36", deep , but narrow.
Ids this what otheres want? |
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| planet10 |
| quote: | Originally posted by x. onasis
"Elegantly folded"? I like the sound of that. What sort of bass are we expecting? I'm imagining a rather deep, narrow box that's only about 18-24" tall sitting on it's own matching sub for a stand. Go ahead, tell me the sub won't be necessary. |
The narrow deep box isn't the perfect fold, but i'm still noodling it. Folding it for wide & shallow is a bit more elegant fold wise -- it ends up being wider & shallower (which with the monopole could push the baffle step low enuff that reasonable proximity to real wall would deal with baffle step.
dave |
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| Variac |
Well, 2 somewhat wide and shallow boxes placed back to back for the bi-pole would make a square section tower. They could be built as one box or they could be literally 2 separate boxes that could be screwed together back to back. As you mention, if you just use the front box with one driver, then you have something you MIGHT be able to put close to the wall
So I guess I'm thinking that we could make one box design with one driver that could be doubled and placed back to back for a dipole, or use just one box per channel for use with a BSC filter or against the wall.
I still prefer a narrower form factor if possible, but I see the advantages of wide....
Personally, as I already mentioned, I prefer towers to boxes, but the idea of placing them on a sub to form a tower is an interesting option. |
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| Timn8ter |
| I recommend tuning the cab at 50Hz+. Going any lower may cause loss of cone control. It can be surprising how much satisfaction is gained with quality of bass vs. quantity. |
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| Timn8ter |
| quote: | Originally posted by gmilitano
Assuming that Zport = 28.5 in and a density of 0.3 lb/ft^3, I get the attached response.
I would estimate -6dB @ 50Hz and -3dB @ 70 Hz.
Is it possible to get a little more out of the low end?
Gio. |
It appears that you've modeled the drivers wired in parallel. Are you sure you want to do that? |
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| planet10 |
| quote: | Originally posted by gmilitano
Assuming that Zport = 28.5 |
Set Zport to 30" -- a port out the bottom would work too.
dave |
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| planet10 |
| quote: | Originally posted by Timn8ter
It appears that you've modeled the drivers wired in parallel. |
I'd be wiring mine in series...
dave |
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| planet10 |
| quote: | Originally posted by x. onasis
I'm imagining a rather deep, narrow box that's only about 18-24" tall sitting on it's own matching sub for a stand. Go ahead, tell me the sub won't be necessary. |
1st draft of the narrow folded box... (using guess & by golly method)
Sub not necessary to enjoy the music... only if you want to shake the room.
dave |
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| gmilitano |
| quote: | Originally posted by Timn8ter
It appears that you've modeled the drivers wired in parallel. Are you sure you want to do that? |
| quote: | Originally posted by planet10
I'd be wiring mine in series...
dave |
I guess that depends. I was hoping for a tube friendly design. In series, the efficiency would only be about 90. However, the less than 4 ohm load may be problematic.
Gio. |
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| BTW |
| quote: | Originally posted by planet10
You are confusing me here... 2 drivers wired out of phase in the same box?
Are the magnets of the 2 drivers mechanically connected?
dave |
Hi Dave,
Sorry for not being so clear, the magnets of the 2 drivers are connnected together just like the bipole speaker in your drawing. We had 2 seperate terminals for we could try different ie bipole, dipole, series, parallel connections. |
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| planet10 |
| quote: | Originally posted by gmilitano
I was hoping for a tube friendly design. In series, the efficiency would only be about 90. However, the less than 4 ohm load may be problematic. |
Wired in series is particularily tube friendly. Wiring in series doesn't effect the efficiency. If you have a solid state amp, you'll; have a happier amp with 3 dB less power, less distortion & more balls. With a tube amp you won't lose much power (none if you have higher Z taps), and less distortion.
Besides series seems to sound better.
dave |
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| planet10 |
| quote: | Originally posted by BTW
the magnets of the 2 drivers are connnected together just like the bipole speaker in your drawing. We had 2 seperate terminals for we could try different ie bipole, dipole, series, parallel connections. |
OK.
Loading into the box you would have no output at all at levelengths smaller than about 2 x the average cabinet dimension. I think you'd be way better off just mounting the 2 drivers in an actual open baffle.
Separate connectors is what i put on them -- but mostly to play with series/parallel.
dave |
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| BTW |
| quote: | Originally posted by planet10
OK.
Loading into the box you would have no output at all at levelengths smaller than about 2 x the average cabinet dimension. I think you'd be way better off just mounting the 2 drivers in an actual open baffle.
Separate connectors is what i put on them -- but mostly to play with series/parallel.
dave |
Thanks Dave, think I'll get out my OB baffles and do some comparisons. :) |
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| gmilitano |
Well, I need to get into the fun. Here is what I have come up with. It is a little larger than the v0.1.
I'd appreciate it if someone could look over my model to see if there are any errors.
I chose the internal dimensions 6.5" X 10" so that the enclosure could be built with standard 1"X8" and 1"X10" boards which should have a nominal 3/4" thickness.
I'll have to check, but I think a 3" OD pipe has an internal radius of 1.414".
Regards,
Gio. |
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| Variac |
a nominal 1x8 would be .75"x 7.5" I believe.
A nominal 1x10 would be .75"x9.25"
1x12 = .75"x11.25"
Maybe finish material is different but I don't think so
Shelf boards might be different also |
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| planet10 |
Tim,
If you were to put a rebate into the baffle to flush mount the front of the 127, out deep would it be?
dave |
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| planet10 |
Here is a 1st draft of a bi-pole folded version... for a monopole the cabinet is sliced at the red line. I've drawn it round topped but it could be square with reflectors.
dave |
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| planet10 |
we can call the monopole version of that the head-stone
:)
dave |
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| planet10 |
a little creative paintwork, and no one would knoe its a speaker...
dave |
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| Kofi Annan |
OK. I dig this. Looks like an old Philco radio (or any vintage radio, for that matter).
Could we wire it so's it could only play reruns of The Shadow and Abbott and Costello?
Kofi |
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| Timn8ter |
| quote: | Originally posted by planet10
Tim,
If you were to put a rebate into the baffle to flush mount the front of the 127, out deep would it be?
dave |
The frame itself is only 2mm plus the final thickness of whatever sealant is chosen. The underside of the frame is not flat (the edge is rolled over) so the sealant will not change the total thickness very much. Since I'm using rope caulk I would stay at 3mm or 1/8" in the States. |
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| Timn8ter |
:confused:
Anyway, how about this?
Internal dims of 23"H x 6.5"W x 10"D. Drivers mounted on the narrow side 20" from the bottom (internal). Internal baffle when viewed from the wide side begins at 6" down 5" from the back, tapers to 1" from the back. A 2" x 2" port at the bottom on the back. Image below from Martin King's MathCAD worksheet |
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| gmilitano |
Hi Tim,
My model was in series. I have gone through the MKJ document and while the text does not mention anything about doubling Bl in series, the example on the last two pages does show Bl as double. In that regard, it is not clear if Bl should be double or not.
Also, how do you know that the LF begins rolling off prematurely? Is that shown on the graphs or is that experience? I like to play around with the MathCAD models, but initial sizing of the cabinets is what I struggle with the most.
Regards,
Gio. |
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| Timn8ter |
| quote: | Originally posted by gmilitano
Hi Tim,
My model was in series. I have gone through the MKJ document and while the text does not mention anything about doubling Bl in series, the example on the last two pages does show Bl as double. In that regard, it is not clear if Bl should be double or not.
Also, how do you know that the LF begins rolling off prematurely? Is that shown on the graphs or is that experience? I like to play around with the MathCAD models, but initial sizing of the cabinets is what I struggle with the most.
Regards,
Gio. |
Yes, I see where you show Re as double, I'm sorry for missing that. Just to be crystal:
TS parameters for two FE127E wired in series:
Fs = 70.4
Re = 13 ohm
Lvc = 0
Bl = 8.28
Sd = 133cm^2
Vas = 19.8 liter
Qe = .50
Qm = 3.33
For parallel Re would be 3.25 ohm and BL would be 4.14.
On page two of Martin's document the only time doubling BL is mentioned is when two drivers are wired in series. Compare my graph to your graph and you'll see where the LF begins to roll off. It may be personal preference but I like to keep LF up as long as possible before rolling off. Just MHO. |
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| gmilitano |
| quote: | Originally posted by Timn8ter
Yes, I see where you show Re as double, I'm sorry for missing that. Just to be crystal:
For parallel Re would be 3.25 ohm and BL would be 4.14.
Compare my graph to your graph and you'll see where the LF begins to roll off. It may be personal preference but I like to keep LF up as long as possible before rolling off. Just MHO. |
Great, sounds like I have the parameters all down, thanks for your help.
Perfect, I now understand what you mean by LF roll off, you mean the slope of the line (sorry, I speak better math than english)! Ok this makes sense.
Now, why I keep harping on the bass is becuase the series example of the 40-1197 in the MJK document. The 1197 has an Fs 0f 83 and a Qtd of .372 compared to the Fs of 70 and Qtd of .435 for the FE127E.
Despite that, the 1197 is getting about 62Hz at 0dB and 55Hz at -3dB, while we a more like 80Hz at 0dB and 60Hz at -3dB. Considering we have a bigger driver, with lower Fs and higher Q, I think we should be able to better the LF of the 1197 by 10Hz or more.
I was hoping to be able to get more low end out of these two drivers. Perhaps we should ask the question of how much bass we would like to see out of this project?
I would like to see (hear!) at least 50Hz at -3dB or better.
Anyway, lets hear what others think.
Gio. |
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| Timn8ter |
| While I think Martin King's MathCAD worksheet is a wonderful tool it is still a tool. Martin has told us that there are some things that are not reflected accurately in the modeling, one in particular being baffle step. The bump you see in the example graphs for the 1197 is an anomoly. What I see is that the FE127E is 50hz at 85db, which is lower than the 1197. Granted, it's not much but when you start driving for bass response beyond Fs*.707 you risk loss of cone control and from experience I can tell you the 127 will "slap" at moderate volume levels during heavy bass tracks and when not slapping will muddle the mid-range. |
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| amt |
Great project guys.
Gio,
Trying to get too much LF out of the drivers will definately rob them of midrange clarity. Ive built 8 different speakers using the 1197 and an ob with a helper woofer was clearly the best way of keeping as much midrange magic as possible. Second best is the bipole arrangement which Ive used as HT for 4 years now. BTW, I find that parallelled drivers and the gain in efficiency adds much to the dynamics of the drivers. . My gainclones and Sonic Impact based amps have no problem with 4 ohm loads and the gain in output and "speed" is noticable to me. Below is my best effort at a 4". All dipole and done on the cheap. My current thoughts are of a bipole, backhorn design.
amt |
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| juggle2 |
One might hope the term "elegant" would suggest more universal appeal.
:) (end of sarcasm)
Question: How important is the level placement of the opposing drivers in regard to BSC? IOW, Could the rear driver be placed slightly higher? This might necessitate a braced, rectangular board as a mechanical coupler for the drivers.
And as a related follow-up ... might the rear driver's TL be a simple L shape, placed over the top and rear of the of the single driver plan? This might provide for a cab still around 8" wide and 12" deep. |
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| x. onasis |
(my quote function ain't working at the moment)
"I can tell you the 127 will "slap" at moderate volume levels during heavy bass tracks and when not slapping will muddle the mid-range."
I keep thinking how Dave used to keep reminding us of the benefit of going active for bass, ie. "frees the mid up to do what it does best." (or in this case, the full ranger) |
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| planet10 |
| quote: | Originally posted by juggle2
One might hope the term "elegant" would suggest more universal appeal. |
A term from my math days... nothing to do with visual appeal. But i did come up with one that was not your regular box -- the geometry is probably too extreme to work (which is why i held off posting it). The terminus would probably be best not as a tube, but built in as part of the box -- perhaps a development of the point. Flip it 180 degrees and you could hang them from the ceiling by the point.
| quote: | | Question: How important is the level placement of the opposing drivers in regard to BSC? IOW, Could the rear driver be placed slightly higher? This might necessitate a braced, rectangular board as a mechanical coupler for the drivers. |
Won't affect BSC, but in a TL will much with the tuning developed by having a driver offset... the drivers need to appear to the line like they are in the same place.
dave |
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| Timn8ter |
| quote: | Originally posted by planet10
a little creative paintwork, and no one would know its a speaker...
dave |
Hmmmm....it's interesting what comes out of your mind at 2am Dave. Kinda like the eyeball on the US dollar bill. Illuminati?:dodgy:
(No, I still haven't read it.)
The curved top is interesting but time is a valuable quantity for me lately. I doubt I would build it. I do like the idea of a folded pipe though because the common version is quick and easy to build. |
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| planet10 |
| quote: | Originally posted by Timn8ter
The curved top is interesting but... |
The Flat-Top (tm) version:
internal reflectors are optional (2 possible drawn in green & magenta)
Port out the front, back, side, or bottom (as illustrated).
Next up the lated Tim suggestion. Supper 1st.
dave |
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| planet10 |
| quote: | Originally posted by Timn8ter
Internal dims of 23"H x 6.5"W x 10"D. Drivers mounted on the narrow side 20" from the bottom (internal). Internal baffle when viewed from the wide side begins at 6" down 5" from the back, tapers to 1" from the back. A 2" x 2" port at the bottom on the back |
Like this?
dave |
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| Timn8ter |
| quote: | | The Flat-Top (tm) version: |
...not "Prune Face", thankfully.
:cannotbe: Oh yeah, I guess we decided it should have a down-firing port. Still could. I had the top of the line ending 4 inches up from the bottom of the cabinet allowing room for a rear firing port. This could easily accomodate a down-firing port also. |
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| planet10 |
This closer to what you had in mind?
dave |
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| SCD |
Morning boys:
I foolishly went to bed last night and missed all the fun. Somewhere back in the discussion things turned to a stand mount for the bipole. Any reason we could not do the bipole as a free stander tower. Some designs I have seen put a pseudo stand together with a short cabinet. It uses a down firing port and a slant front. This could easily be mounted on a solid base. The space behind the slant can be loaded with either lead shot or baked sand. |
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| Timn8ter |
| quote: | Originally posted by SCD
Morning boys:
I foolishly went to bed last night and missed all the fun. Somewhere back in the discussion things turned to a stand mount for the bipole. Any reason we could not do the bipole as a free stander tower. Some designs I have seen put a pseudo stand together with a short cabinet. It uses a down firing port and a slant front. This could easily be mounted on a solid base. The space behind the slant can be loaded with either lead shot or baked sand. |
That was actually discussed earlier and is the reason for the down-firing ports in the drawings from Dave except for mine, however, it's easy enough to move the port to that position. Determining the output for the port in a psuedo-stand will be an interesting exercise. GM had described how to do that without turning it into a horn. I'll have to look around for that info. IIRC, he recommended having the port tube exit into a slot port. My bipole FE103E uses a slant front which interestingly enough sounds better when it's off the floor several inches. |
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