10F/8424 in 2.3L Bass Reflex
My sims show that you will need at least a 2.3 liter cabinet to extract reasonable extension down to 80Hz with the 10F. Here is the cabinet tuned to 84Hz, the extension is about 79Hz at -3dB. It will need a high pass filter to prevent over excursion below this though. But if you were running 30 of them, the stroke would be cut by 30x, so maybe not an issue.
Freq response:
Displacement:
Impedance:
From my other thread, I can see that you can have a ported alignment to make it flat to 80Hz, but XO at 2 octaves higher at 320Hz, and this gives you the bandwidth needed for a -6dB/oct XO needed for a time-aligned FAST. So the cones would never actually move that much.
Here is what the frequency response would look like with a 320Hz 1st order Butterworth high pass filter applied (as the linear phase time aligned xo):
Here is the cone displacement of a single BR driver at xmax of 2.55mm - it takes 21 volts:
Here is the corresponding max SPL at 21 volts - about 105.7dB! Not bad - x 30 would be quite the loud semi PA like system:
My sims show that you will need at least a 2.3 liter cabinet to extract reasonable extension down to 80Hz with the 10F. Here is the cabinet tuned to 84Hz, the extension is about 79Hz at -3dB. It will need a high pass filter to prevent over excursion below this though. But if you were running 30 of them, the stroke would be cut by 30x, so maybe not an issue.
Freq response:
Displacement:
Impedance:
From my other thread, I can see that you can have a ported alignment to make it flat to 80Hz, but XO at 2 octaves higher at 320Hz, and this gives you the bandwidth needed for a -6dB/oct XO needed for a time-aligned FAST. So the cones would never actually move that much.
Here is what the frequency response would look like with a 320Hz 1st order Butterworth high pass filter applied (as the linear phase time aligned xo):
Here is the cone displacement of a single BR driver at xmax of 2.55mm - it takes 21 volts:
Here is the corresponding max SPL at 21 volts - about 105.7dB! Not bad - x 30 would be quite the loud semi PA like system:
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2.3 liter cabinet to extract reasonable extension down to 80Hz with the 10F.
Freq response:
I would question that sim (unless it has EQ built-in): here is what i get. Pretty ugly.
dave
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???
Dare I ask, Why are these so different? Different software, different formulas used, different BR alignments?
In all honesty, I doubt I will be going with BR, as I have had a hard time EQing them in the past and the bass always sounds out of wack to me. BR's seem to be very room dependent too.
Dare I ask, Why are these so different? Different software, different formulas used, different BR alignments?
In all honesty, I doubt I will be going with BR, as I have had a hard time EQing them in the past and the bass always sounds out of wack to me. BR's seem to be very room dependent too.
Thanks X
I wonder if this is the case with a near-field line array, where I will be listening to the 80 Hz through 300 Hz signal in the near field. Reflections are still a factor, but I believe more of the direct sound will cut through. Thoughts anyone?
Yes, 5 drivers in series, then those 6 groups paralleled. I end up with 6.666666666... ohms - do not know if I like that number!
Yes, I agree the woofer is going to be harder to integrate at these higher frequencies. 80 Hz is easier, but still not perfect. I like the idea of going completely full-range if the drivers can handle all that signal on dynamic peaks without discernible IM distortion. 30 Hz is more then sufficient for me. I would only use the subs for movies in that case.
Allen
I wonder if this is the case with a near-field line array, where I will be listening to the 80 Hz through 300 Hz signal in the near field. Reflections are still a factor, but I believe more of the direct sound will cut through. Thoughts anyone?
Yes, 5 drivers in series, then those 6 groups paralleled. I end up with 6.666666666... ohms - do not know if I like that number!
Yes, I agree the woofer is going to be harder to integrate at these higher frequencies. 80 Hz is easier, but still not perfect. I like the idea of going completely full-range if the drivers can handle all that signal on dynamic peaks without discernible IM distortion. 30 Hz is more then sufficient for me. I would only use the subs for movies in that case.
Allen
I would question that sim (unless it has EQ built-in): here is what i get. Pretty ugly.
dave
This is straight forward bass reflex element in Akabak - quite accurate from my experience. I have not accounted for baffle step loss because we don't know what the baffle is yet. There is no EQ in my sim.
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Use TS params from here
http://www.scan-speak.dk/datasheet/pdf/10f-8424g00.pdf
In Akabak, there is an option to set effective Q/fb. I set that at 0.1 to correspond to having some damping internally. Makes a minor difference - won't fix a funky step ledge response like that.
The impedance is always higher than the DCR. For the purposes of this kind of calc, nominal impedance is fine. For most of the range it will likely be higher.
dave
Rather than argue with whose model is right, I just whipped up a quick and dirty 2.3L bass reflex box and tested the 10F/8424 - 30mm dia x 75mm long port exits out of bottom, I put fiberglass damping on one end surrounding the internal port tube, and lined the wall opposite the driver with foam:
Near field measurements of port (red) and cone (green - still some port contribution) and combined output (blue) about 0.3 meter away (levels are NOT to scale):
Impedance measurement using DATS v2.0 showing tuning freq of 81Hz:
Simulation of cone, port, combined for 81Hz:
Oh, and almost forgot to say, with a 1.0mH & 5R BSC in place, the response is flat and it sounds quite nice. 80Hz bass is not bad and sufficient for easy listening as a portable speaker or mp3 player dock. The lower Qts of this driver makes for a compact BR box.
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I am Awestruck...
Dave and X,
My heart goes out to both of You for the interest and dedicated effort You guys are putting out on this project on my behalf.
I will have to invite You guys out to listen to the final Arrays when they are up and running (it will be a while yet 
) Have either of You been to the UP (Upper Peninsula Michigan)?
X, that response looks quite good actually, maybe there is some potential to a BR alignment if I can design the cabinet so the "ported" bass is in-phase and aligned with the direct sound emanating from the driver. Maybe a vent spanning the entire length of the cabinet on the back would work. I would be curious to see how your dirty 2.3L bass reflex box works for your FAST system with the RS225. I have not had time to review that thread yet due to the intense work load I have and will continue to have through June. But maybe a lower cross-over point would help (not necessarily 80 Hz). It would be interesting to play with and compare...
Dave and X,
My heart goes out to both of You for the interest and dedicated effort You guys are putting out on this project on my behalf.
I will have to invite You guys out to listen to the final Arrays when they are up and running (it will be a while yet ) Have either of You been to the UP (Upper Peninsula Michigan)?X, that response looks quite good actually, maybe there is some potential to a BR alignment if I can design the cabinet so the "ported" bass is in-phase and aligned with the direct sound emanating from the driver. Maybe a vent spanning the entire length of the cabinet on the back would work. I would be curious to see how your dirty 2.3L bass reflex box works for your FAST system with the RS225. I have not had time to review that thread yet due to the intense work load I have and will continue to have through June. But maybe a lower cross-over point would help (not necessarily 80 Hz). It would be interesting to play with and compare...
On a slightly different note;
X struck me with a possibility:
Lets entertain the idea of a full-range array:
If I was to pursue using the 10F as a full-range array, I would need to use a sealed cabinet to get bass below 80 Hz. I noticed in Dave's Sims, the bigger the box, the more "potential" bass extension was possible with EQ. I realize a bigger box causes a higher F3 and a lower Q, but being this is being EQed for a flat response anyway, would the EQ raise the Q? In fact, I could EQ to either "transient perfect" (0.5) or "flat response" (0.707). Of course, Excursion would be the limiting factor... ...again.
What I am gathering from the quote above, is one thing one sacrifices with a FAST system is "transient perfect steps". Have others of You experienced a loss in this attribute in your FASTs?
What I can say about this myself with my personal experience using Subs with my Avebury system, is the above statement is indeed correct. It is really hard to time align a mono-pole sub-woofer to a rear loaded horn, even at 80 Hz or lower. The bummer of the matter is, the mid-range is better with the sub-woofers, even though the bass is ever so slightly off. But for certain kinds of music, esp acoustical, small scaled material, Avebury run full-range is hard to beat. Yet for movies and large scaled and complex music, I must compromise the nimble bass for more open and dynamic mid-range with less overall IM distortion. But again, I am dealing with two very different bass systems, one being direct and the other being all reflected. That is an uphill battle right from the start...
But I am excited to try Avebury in a FAST system with these smaller full-rangers on mids and highs. Avebury will be doing the bass. I can try these higher cross-over points and hear for myself what the possibilities are...
X struck me with a possibility:
Lets entertain the idea of a full-range array:
If I was to pursue using the 10F as a full-range array, I would need to use a sealed cabinet to get bass below 80 Hz. I noticed in Dave's Sims, the bigger the box, the more "potential" bass extension was possible with EQ. I realize a bigger box causes a higher F3 and a lower Q, but being this is being EQed for a flat response anyway, would the EQ raise the Q? In fact, I could EQ to either "transient perfect" (0.5) or "flat response" (0.707). Of course, Excursion would be the limiting factor... ...again.
What I am gathering from the quote above, is one thing one sacrifices with a FAST system is "transient perfect steps". Have others of You experienced a loss in this attribute in your FASTs?
What I can say about this myself with my personal experience using Subs with my Avebury system, is the above statement is indeed correct. It is really hard to time align a mono-pole sub-woofer to a rear loaded horn, even at 80 Hz or lower. The bummer of the matter is, the mid-range is better with the sub-woofers, even though the bass is ever so slightly off. But for certain kinds of music, esp acoustical, small scaled material, Avebury run full-range is hard to beat. Yet for movies and large scaled and complex music, I must compromise the nimble bass for more open and dynamic mid-range with less overall IM distortion. But again, I am dealing with two very different bass systems, one being direct and the other being all reflected. That is an uphill battle right from the start...
But I am excited to try Avebury in a FAST system with these smaller full-rangers on mids and highs. Avebury will be doing the bass. I can try these higher cross-over points and hear for myself what the possibilities are...
You read my mind, sort of where I was going with this...
I think a bigger sealed box gets a lower f3 and a higher Q.
The transient perfect I am talking about here with a FAST is the ability to integrate the XO of the full range and bass unit so that the phase is flat and the step response looks like a right triangle - which gives clean transients. It's very difficult to achieve in multiway speakers. A single full range or an array of full range drivers in a sealed box can easily achieve transient perfect because there is not crossover to mess with phase. Full range in a BR will not be as good as there is a phase difference between the port and the direct radiation. I am not talking about underdamped ,critically damped, or overdamped Q's.
Way to go!
Looking forward to your experiments and listening impressions.
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Allen,Just placed an order with Madisound Speaker Components:
A pair of ScanSpeak 10F/8424G,
And a pair of Fostex FF85wk on the way...
Time to get my hands dirty...
Allen
If I may ask, what made you decide to drop the Tectonics BMR from your list? Or is that for consideration in the future?
Just curious.
Thanks.
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