One world is high efficiency / broadband and the other is conventional moreway.
The speaker I thought up uses:
-A broadband whizzer-less 5" 88 db driver, open baffle [Fostex FX120]
-An 8" 88 db mid-bass driver, sealed [Scan-speak 8545]
-1st order cross-over at 300 hz
The FX120 has a very flat response, which is hard to find in broadband world. Yes, it is only 88 db, but flat frequency respons
is a must, in my opinion.
Sealed enclosure because a ported design (especially in small rooms) will give too much bass.
This way cost and enclosure complexity are kept pretty low, but will have a great (I think) and balanced sound.
My questions are:
-Any comments on this design?
-Does anyone know how I can calculate the needed sealed enclosure volume?
The speaker I thought up uses:
-A broadband whizzer-less 5" 88 db driver, open baffle [Fostex FX120]
-An 8" 88 db mid-bass driver, sealed [Scan-speak 8545]
-1st order cross-over at 300 hz
The FX120 has a very flat response, which is hard to find in broadband world. Yes, it is only 88 db, but flat frequency respons
is a must, in my opinion.
Sealed enclosure because a ported design (especially in small rooms) will give too much bass.
This way cost and enclosure complexity are kept pretty low, but will have a great (I think) and balanced sound.
My questions are:
-Any comments on this design?
-Does anyone know how I can calculate the needed sealed enclosure volume?
I like it.
I have a slight feeling, that planet10 will
comment on the Fostex.
It has fs 70 Hz, so 300 is more than 4 times above.
ScanS 8545 is not at all bad suited for sealed box.
So for a reasonable small box, say 50-80 liters
you will get a rather low Fc and f-3dB
And not too high Qtc. I like below 0.7
I would prefer this setup to
8" + 25mm dometweeter.
I would rather have some slope in the upper, beyond my hearing area,
than to let the 8 inch woofer handle
the diskant/treble up to 2500-3000 Hz.
With a power of 16 watts, the Fostex will put out
up to 100dB. It is rated something like 30 W.
It is enough for an ordinary room.
I have a slight feeling, that planet10 will
comment on the Fostex.
It has fs 70 Hz, so 300 is more than 4 times above.
ScanS 8545 is not at all bad suited for sealed box.
So for a reasonable small box, say 50-80 liters
you will get a rather low Fc and f-3dB
And not too high Qtc. I like below 0.7
I would prefer this setup to
8" + 25mm dometweeter.
I would rather have some slope in the upper, beyond my hearing area,
than to let the 8 inch woofer handle
the diskant/treble up to 2500-3000 Hz.
With a power of 16 watts, the Fostex will put out
up to 100dB. It is rated something like 30 W.
It is enough for an ordinary room.
According to to the plot seen at www.eifl.co.jp the Fostex FX120 dosen't look very smooth and off axis roll off is quite steep.
Though it's more expensive the FX200 is much smoother, in this case it seems that a notch filter will be needed at around 4Khz. But as usual it has to be tested.
I am also looking to do something simillar to your project. It would be interesting for you to have look at other threads on the subject since there are almost identical projects been worked.
Though it's more expensive the FX200 is much smoother, in this case it seems that a notch filter will be needed at around 4Khz. But as usual it has to be tested.
I am also looking to do something simillar to your project. It would be interesting for you to have look at other threads on the subject since there are almost identical projects been worked.
Can you direct me to such projects? I haven't run in to any.
The FX200 is quite more expensive (here in Europe: 145 <-> 215). Strange thing that Fostex measures differently than Eifl. I really want to keep the costs low so that the design can be built by other people too. Also the FX120's efficiency is a better match with the Scan-speak.
The FX200 is quite more expensive (here in Europe: 145 <-> 215). Strange thing that Fostex measures differently than Eifl. I really want to keep the costs low so that the design can be built by other people too. Also the FX120's efficiency is a better match with the Scan-speak.
What you are describing is one implementation of what i call a "mostly full-range system. I have veen doing it with ESLs for years, but am now playing with conventional drivers (so i can get efficient enuff to also play with small tube amps and Class A SS).
The XO of 300 Hz is as high as you want to go -- lower would be better. Much lower and you have to go active.
As more & more interesting FRs hit the market the choices increase. There are any number of suitable candidates for top end on this kind of thing. This concept will be played out in The Tale of Two Tangbands and the
New Reference Speakers with Full/Wide-Range Driver thread is also covering similar territory. Variacs variation on the Basszilla is the same kind of thing.
dave
The XO of 300 Hz is as high as you want to go -- lower would be better. Much lower and you have to go active.
As more & more interesting FRs hit the market the choices increase. There are any number of suitable candidates for top end on this kind of thing. This concept will be played out in The Tale of Two Tangbands and the
New Reference Speakers with Full/Wide-Range Driver thread is also covering similar territory. Variacs variation on the Basszilla is the same kind of thing.
dave
Nielsio said:
I just throw the T/S parameters in a box modeling program and then juggle Q and box size until i get something suitable for the application (bigger box means lower Q). My program gives between 6 litres (Q=0.7) to 35 litres (Q=0.5).
kelticwizard has this all stored in his head
dave
Nielsio said:
The Critical mid band is considered to go from 80-150 Hz up to 4-6kHz. In the situation one tries to get the XO as close as you can get to those limits
below 200 Hz the size of the passive components start getting impractically large.
In the 1st of the Tangband projects i'm going to try to get the XO down towards the 250 Hz mark. In the 2nd i'll go active somewhere between 150 & 180 (nothing set in stone yet of course)
dave
Online Calc with "WINISD"
and BOXsizes.
At this page, you can put in values
and get results.
When calculating you need mainly
3 data of the woofer:
-Vas in liters
-fs in Heartz, the resonance freq
-Qts
For your formula you can have one factor
you want to set.
Most common is to set Qtc of the box,
this set the low rolloff of the bass.
Qtc= 0.707 gives the lowest -3dB point of the woofer.
Then you can get the Box size you need for Qtc 0.707
You can also say that I will limit the boxsize Vb, Volume box
to x liters.
Then you get the Qtc and Fc and -f3
I have downloaded the program from that site.
Many uses this FREEWARE.
And many can better than me
tell you how to use WINISD.
WINISD online calculation
With WINISD freeware program, you get the CURVES in diagramNielsio said:
and BOXsizes.
At this page, you can put in values
and get results.
When calculating you need mainly
3 data of the woofer:
-Vas in liters
-fs in Heartz, the resonance freq
-Qts
For your formula you can have one factor
you want to set.
Most common is to set Qtc of the box,
this set the low rolloff of the bass.
Qtc= 0.707 gives the lowest -3dB point of the woofer.
Then you can get the Box size you need for Qtc 0.707
You can also say that I will limit the boxsize Vb, Volume box
to x liters.
Then you get the Qtc and Fc and -f3
I have downloaded the program from that site.
Many uses this FREEWARE.
And many can better than me
tell you how to use WINISD.
WINISD online calculation
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