Efficiency
No mention of "decent", just "some" bass.
You need 4 times the enclosure size for every octave you drop,
when power and efficiency are kept constant (Hoffman's Iron Law). From an increase in enclosure size from 40l to 160l, in your example, one would gain bass extension from (~)100 to 50 Hz - a cube of 54.6cm (21.5"). No "fridge" fits that description around here. Cooler, maybe.
Tim
No mention of "decent", just "some" bass.
You need 4 times the enclosure size for every octave you drop,
when power and efficiency are kept constant (Hoffman's Iron Law). From an increase in enclosure size from 40l to 160l, in your example, one would gain bass extension from (~)100 to 50 Hz - a cube of 54.6cm (21.5"). No "fridge" fits that description around here. Cooler, maybe.
Tim
Well, I have no idea what this is, but I do not what 'Girlfriend's Iron Law' is and that's "Nag every day till speakers are put back together"
But, keeping the chin up here, I'm just wondering where we stand now and if we're leaning toward any solution. Whatever did happen with the fostex - are they in or out?
Re: Any vintage speakers above $100 - With no warranty, I just ain't got the jack to gamble on them. Unless, I was certain they were dead mint. This was one of the reasons why I forged ahead and sealed up the box. So this pretty much prescinds that route.
Thanks again for all the help. I suppose Graham Greene put it best:
'Despair is the price one pays for setting his sites on impossible goals.'
Or something to that effect.
Take care,
Giacomo
Some more basic principles :
Take the Seas Njord as an example:
http://www.seas.no/kit/Njord.pdf
The bass driver has a genuine 93dB/W effficiency.
Yet the speaker is rated at 88dB/W.
This is because the Njord is specified for free space placement
and includes 5dB of baffle step compensation for balanced bass.
BSC must be included for good bass,
minimum is 3dB for close to wall placement.
So a genuine 100dB/W speaker needs a unit of at least 103dB/W.
TM :
Simply not true, its 8 times the size, = 320 litres.
My fridge is 19" x 18" x 28" = 5.5 cuft = 150 litres.
I reckon 320 litres is enough to cover a small American fridge
.
sreten.
Take the Seas Njord as an example:
http://www.seas.no/kit/Njord.pdf
The bass driver has a genuine 93dB/W effficiency.
Yet the speaker is rated at 88dB/W.
This is because the Njord is specified for free space placement
and includes 5dB of baffle step compensation for balanced bass.
BSC must be included for good bass,
minimum is 3dB for close to wall placement.
So a genuine 100dB/W speaker needs a unit of at least 103dB/W.
TM :
Simply not true, its 8 times the size, = 320 litres.
My fridge is 19" x 18" x 28" = 5.5 cuft = 150 litres.
I reckon 320 litres is enough to cover a small American fridge
. sreten.giacomo said:
I haven't given up yet.
I'm beginning to understand why so many full range designs sound
awful, simply the builders haven't got a clue about basic acoustics.
The Fostex will give outstanding levels in the midrange and treble.
But if you can't balance this results will be frustrating to say the least.
I'm still researching options and will get back to you.
sreten.Re: Efficiency
Hi TM,
Yet another example of being good at making out you
know what you are talking about when you don't.
I know you don't like my attitude, but see it from my perspective,
you make statements that are wrong usually qualified by by some
reference or theory that reads as though you are talking sense.
As I've said before I honestly wish you did know your stuff.
But by contradicting people that do, and carrying on regardless
of anything that contradicts your opinion your not really getting
the best out of a forum like this.
Your posts do have some good points, which are relevant,
but you have to accept that in a forum like this that to say
"its like this" is not the same as "I think its like this isn't it ?".
Unless you are sure you are correct.
sreten.
Tim Moorman said:
Hi TM,
Yet another example of being good at making out you
know what you are talking about when you don't.
I know you don't like my attitude, but see it from my perspective,
you make statements that are wrong usually qualified by by some
reference or theory that reads as though you are talking sense.
As I've said before I honestly wish you did know your stuff.
But by contradicting people that do, and carrying on regardless
of anything that contradicts your opinion your not really getting
the best out of a forum like this.
Your posts do have some good points, which are relevant,
but you have to accept that in a forum like this that to say
"its like this" is not the same as "I think its like this isn't it ?".
Unless you are sure you are correct.
sreten.
Re: Re: Efficiency
Ok calm down... Tim is sorta right. I dug into my archives and pulled up a basslist post where Tim states that the box actually needs to be 8 times as big. Since he was contradicting himself, i dug a bit further.
Hoffman's Law, the equation for the Spl output regardless of the driver (in a perfect world)
"no" = 2E-9 x F3^3 x Vb (in litres)
so for our case where we want to get an extra octave of bass, keeping sensitivity the same....
Vb = "no"x2e9/F3^3
If F'3 = F3/2
then V'b = 8 x Vb
Briefly, Hoffman's Iron Law says that there are three things you can
optimize in any design: 1) box size, 2) efficiency/sensitivity, or 3) low
bass extension.
dave
sreten said:
Ok calm down... Tim is sorta right. I dug into my archives and pulled up a basslist post where Tim states that the box actually needs to be 8 times as big. Since he was contradicting himself, i dug a bit further.
Hoffman's Law, the equation for the Spl output regardless of the driver (in a perfect world)
"no" = 2E-9 x F3^3 x Vb (in litres)
so for our case where we want to get an extra octave of bass, keeping sensitivity the same....
Vb = "no"x2e9/F3^3
If F'3 = F3/2
then V'b = 8 x Vb
Briefly, Hoffman's Iron Law says that there are three things you can
optimize in any design: 1) box size, 2) efficiency/sensitivity, or 3) low
bass extension.
dave
Oops!
Yes, folks, you are correct. My mistake. One octave drop in freq requires 8 times the box volume (efficiency and power unchanged), not 4X.
Memory banks are fading; should have verified.
Thanks, Dave, for the clarification...and the search.
I still like the sound of the vintage woofers on tube gear. Dynamics and tone in spades, and even at low volume.
I'm sure the folks at Madisound have enough feedback on the Fostex units to suggest which may work out well in the enclosure.
Maybe G could call or email them for his options.
Tim
Yes, folks, you are correct. My mistake. One octave drop in freq requires 8 times the box volume (efficiency and power unchanged), not 4X.
Memory banks are fading; should have verified.
Thanks, Dave, for the clarification...and the search.
I still like the sound of the vintage woofers on tube gear. Dynamics and tone in spades, and even at low volume.
I'm sure the folks at Madisound have enough feedback on the Fostex units to suggest which may work out well in the enclosure.
Maybe G could call or email them for his options.
Tim
Snell / Audionote clone
Ok, I'm giving up on the full range approach, I can't get it to work
to my satisfaction and also fulfil Giacomo's basic requirements.
so I'm going back to what I know, the following :
http://www.hifichoice.co.uk/review_read.asp?ID=475
Is a design specifically intended for valve amplifiers, and I'm
pretty sure it uses the same bass unit, or a version of the same
unit as the Njord design,
the Seas CA21REX paper cone 93dB/W unit.
Whatsmore I'm pretty sure the crossovers are very similar, first
order, as the the original designer Snell liked them this way.
Simulations indicate excellent bass, 40Hz (lower in room ~ 30Hz)
and no bass power handling issues whatsover, excursion limits
with 10W only occur below 24Hz.
They also indicate with the low damping factor of the amplifier
tuning the port to 35Hz instead of 40Hz with 40L is a good idea.
So how does the Njord crossover work ?
http://www.seas.no/kit/Njord.pdf
Treble c/o is ~ 3.5kHz, but at first sight bass c/o is 600Hz ?
The inductor is implementing baffle step compensation.
Baffle step is centred around 400Hz and is a 6dB rise over
the range of ~ 130Hz to ~ 1.2KHz. (for average baffle width)
The bass unit is designed to have a rising response above 1.2khz
that in combination with the BS inductor gives a flat response.
The crossover point is where the units response flattens out.
(note the CA21REX specs are measured in a box not on a baffle)
This means by varying the value if the inductor you can adjust
the amount of BSC without changing the c/o point, but as you
lift up the midrange by reducing the inductor value you need
to readjust the level of the tweeter.
The Njord is designed for freespace siting away from walls
and has 5dB of BSC. I'd suggest reducing this to 3 dB.
I'd suggest using the 91dB/W Seas 27TFFC
(excellent reputation) with 1.5R and 5.6uF.
For both options the bass unit inductor can be tuned by ear,
learning to wind / unwind inductors is a good idea.
Value needed I estimate at around 1mH.
The result will be a genuine 8 ohm 90dB/W loudspeaker.
Which given the box size, bass extension required and
8 ohms loading required is as good as your going to get.
And they'll sound quite different to the Event 20/20's.
(For tweaking there is the option of 6.8uF and no resistor
for the tweeter, tweaking the inductor again for 91dB/W)
sreten.
Ok, I'm giving up on the full range approach, I can't get it to work
to my satisfaction and also fulfil Giacomo's basic requirements.
so I'm going back to what I know, the following :
http://www.hifichoice.co.uk/review_read.asp?ID=475
Is a design specifically intended for valve amplifiers, and I'm
pretty sure it uses the same bass unit, or a version of the same
unit as the Njord design,
the Seas CA21REX paper cone 93dB/W unit.
Whatsmore I'm pretty sure the crossovers are very similar, first
order, as the the original designer Snell liked them this way.
Simulations indicate excellent bass, 40Hz (lower in room ~ 30Hz)
and no bass power handling issues whatsover, excursion limits
with 10W only occur below 24Hz.
They also indicate with the low damping factor of the amplifier
tuning the port to 35Hz instead of 40Hz with 40L is a good idea.
So how does the Njord crossover work ?
http://www.seas.no/kit/Njord.pdf
Treble c/o is ~ 3.5kHz, but at first sight bass c/o is 600Hz ?
The inductor is implementing baffle step compensation.
Baffle step is centred around 400Hz and is a 6dB rise over
the range of ~ 130Hz to ~ 1.2KHz. (for average baffle width)
The bass unit is designed to have a rising response above 1.2khz
that in combination with the BS inductor gives a flat response.
The crossover point is where the units response flattens out.
(note the CA21REX specs are measured in a box not on a baffle)
This means by varying the value if the inductor you can adjust
the amount of BSC without changing the c/o point, but as you
lift up the midrange by reducing the inductor value you need
to readjust the level of the tweeter.
The Njord is designed for freespace siting away from walls
and has 5dB of BSC. I'd suggest reducing this to 3 dB.
I'd suggest using the 91dB/W Seas 27TFFC
(excellent reputation) with 1.5R and 5.6uF.
For both options the bass unit inductor can be tuned by ear,
learning to wind / unwind inductors is a good idea.
Value needed I estimate at around 1mH.
The result will be a genuine 8 ohm 90dB/W loudspeaker.
Which given the box size, bass extension required and
8 ohms loading required is as good as your going to get.
And they'll sound quite different to the Event 20/20's.
(For tweaking there is the option of 6.8uF and no resistor
for the tweeter, tweaking the inductor again for 91dB/W)
sreten.Attachments
The fostex FE206E option in my opinion with 40L cabinets
requires it to be used with something like this 10" in parallel :
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=290-395
Probably with a series tuneable inductor. Believing the
specs is an issue, but the unit certainly looks the part.
The impedance would be 4 ohms, but with tuning of the
inductor I reckon a reasonably flat response allowing for
placement would be possible.
Really serious levels would be achievable with low powered valve
amplifiers but bass extension below around 60hz would be weak.
Adding in a decent subwoofer for low bass and we are miles
over budget, though the whole combination has promise.
sreten.
requires it to be used with something like this 10" in parallel :
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=290-395
Probably with a series tuneable inductor. Believing the
specs is an issue, but the unit certainly looks the part.
The impedance would be 4 ohms, but with tuning of the
inductor I reckon a reasonably flat response allowing for
placement would be possible.
Really serious levels would be achievable with low powered valve
amplifiers but bass extension below around 60hz would be weak.
Adding in a decent subwoofer for low bass and we are miles
over budget, though the whole combination has promise.
sreten.Attachments
hi Giacomo,
Its make your mind up time again.
[ full range ]
The Fostex FE206E will work, but will probably need a filter
to sound balanced. The filter can always be bypassed and
you could use the tone control(s) instead for frequency
balance adjustment.
Levels achievable midrange and treble without the filter
are very high, maximum bass levels in comparison will be
relatively weak.
For example if the FE206E is eq'd with just your tone
controls solo acoustic guitar and vocals will be great,
a reggae band you'll have to knock the volume back.
With the filter bass levels will be OK in comparison
to mid/ treble levels, and handling of different types
of music will be more even, but the midrange will
not be able to "soar" like it will without the filter.
But the filter may well work better than the tone controls
for even balance as it specifically targets the area that
needs correcting.
Bass will go down to ~ 45Hz in room and will pretty
much match the amplifier, the amplifier and Fostex
will start distorting about the same time.
max bass levels - around 95dB.
max mid/treble - around 100dB (filter) to 106dB
[ two way ]
The 8" bass unit / 1" tweeter will produce similar levels
to the Fostex with filter. In this case bass will be far
stronger in the sense the speaker will not distort,
only the amplifier. Bass will not be a problem at all.
Bass will go down to ~35Hz in room.
Max levels - around 100dB - bass, mid and treble.
As with the Fostex with filter for bass light material you
will not be able to turn it up for high mid/treble levels.
[ other options ]
I've also checked out using Eminence 10" PA drivers.
This is quite workable but reflex loading is not sensible,
sealed box loading is the only option.
As a sealed box bass extension will not be great but
conversely lower bass will not be absent but present
at at lower level. in room extension to 60Hz is about
right but lower bass will be represented.
Compared to the 2-way 8"/1" midrange quality will
suffer but probably about 3dB more level is possible.
Max bass levels - around 100dB
Max mid/treble - around 103dB.
(levels are only really relative, in room and stereo pairs ignored)
sreten.
Its make your mind up time again.
[ full range ]
The Fostex FE206E will work, but will probably need a filter
to sound balanced. The filter can always be bypassed and
you could use the tone control(s) instead for frequency
balance adjustment.
Levels achievable midrange and treble without the filter
are very high, maximum bass levels in comparison will be
relatively weak.
For example if the FE206E is eq'd with just your tone
controls solo acoustic guitar and vocals will be great,
a reggae band you'll have to knock the volume back.
With the filter bass levels will be OK in comparison
to mid/ treble levels, and handling of different types
of music will be more even, but the midrange will
not be able to "soar" like it will without the filter.
But the filter may well work better than the tone controls
for even balance as it specifically targets the area that
needs correcting.
Bass will go down to ~ 45Hz in room and will pretty
much match the amplifier, the amplifier and Fostex
will start distorting about the same time.
max bass levels - around 95dB.
max mid/treble - around 100dB (filter) to 106dB
[ two way ]
The 8" bass unit / 1" tweeter will produce similar levels
to the Fostex with filter. In this case bass will be far
stronger in the sense the speaker will not distort,
only the amplifier. Bass will not be a problem at all.
Bass will go down to ~35Hz in room.
Max levels - around 100dB - bass, mid and treble.
As with the Fostex with filter for bass light material you
will not be able to turn it up for high mid/treble levels.
[ other options ]
I've also checked out using Eminence 10" PA drivers.
This is quite workable but reflex loading is not sensible,
sealed box loading is the only option.
As a sealed box bass extension will not be great but
conversely lower bass will not be absent but present
at at lower level. in room extension to 60Hz is about
right but lower bass will be represented.
Compared to the 2-way 8"/1" midrange quality will
suffer but probably about 3dB more level is possible.
Max bass levels - around 100dB
Max mid/treble - around 103dB.
(levels are only really relative, in room and stereo pairs ignored)
sreten.sreten,
I'm leaning toward the full range because of its ability to handle wider range of material. Though a lot of my records are 60s to present, I also have a lot 50s jazz/lounge too. Will having a combination of full range fostexes do anything for me? Such as a pair of 8" in each cabinet, or a 10" - 8" combination?
Regards
Giacomo
I'm leaning toward the full range because of its ability to handle wider range of material. Though a lot of my records are 60s to present, I also have a lot 50s jazz/lounge too. Will having a combination of full range fostexes do anything for me? Such as a pair of 8" in each cabinet, or a 10" - 8" combination?
Regards
Giacomo
Hi giacomo,
I don't know if you can get hold of them, or how much they would
cost, but if your set on the full range 8 ohm single driver route :
The Supravox 215 RTF Bicone seems to be ideal.
http://www.supravox.fr/
This french driver has very low moving mass (9g) and pretty
decent Xmax, 4mm. Parameters indicate it will work well in
your boxes if they are sealed and stuffed.
The downside is not much in the way of bass, but bass power handling
is good and the response is ideal to easily use a subwoofer in parallel.
On its own bass will go down to 50Hz in room. But a subwoofer will be
needed to bring up maximum bass levels to match those
above 100Hz.
sreten.
I don't know if you can get hold of them, or how much they would
cost, but if your set on the full range 8 ohm single driver route :
The Supravox 215 RTF Bicone seems to be ideal.
http://www.supravox.fr/
This french driver has very low moving mass (9g) and pretty
decent Xmax, 4mm. Parameters indicate it will work well in
your boxes if they are sealed and stuffed.
The downside is not much in the way of bass, but bass power handling
is good and the response is ideal to easily use a subwoofer in parallel.
On its own bass will go down to 50Hz in room. But a subwoofer will be
needed to bring up maximum bass levels to match those
above 100Hz.
sreten.Hi Giacomo,
Having possibly identified the optimum solution, it could be
too expensive and really needs an added subwoofer.
So I've thought about the solution that doesn't need a subwoofer.
I think here your best bet is the Fostex FE207E.
But I think it needs a "helper" tweeter.
Best way of doing this IMO is a nice little wooden box with
a felt bottom that sits on top of each speaker - (polished up
cigar box would be suitable) - and the tweeter I suggest :
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=276-156
The tweeters response looks ideal for the job.
So basically the speakers would be a single driver reflexed,
which is in keeping with the cabinet and age of the equipment.
The add-on tweeter would be exactly that, an add-on, not part of
the rebuilt speaker, which seems to me the the best way of doing it.
sreten.
Having possibly identified the optimum solution, it could be
too expensive and really needs an added subwoofer.
So I've thought about the solution that doesn't need a subwoofer.
I think here your best bet is the Fostex FE207E.
But I think it needs a "helper" tweeter.
Best way of doing this IMO is a nice little wooden box with
a felt bottom that sits on top of each speaker - (polished up
cigar box would be suitable) - and the tweeter I suggest :
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=276-156
The tweeters response looks ideal for the job.
So basically the speakers would be a single driver reflexed,
which is in keeping with the cabinet and age of the equipment.
The add-on tweeter would be exactly that, an add-on, not part of
the rebuilt speaker, which seems to me the the best way of doing it.
sreten.Attachments
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