The B&W midrange originally caught my attention when I auditioned a pair of their 801 loudspeakers. The pretty yellow 6"ers that no audiophile can ignore. The LF00264 is used on the 803 and 804. I saw a pair sold on Ebay and also discovered that they were available as replacement drivers. They're very efficient 94db so I'm wondering if anyone knows how the might do in a dipole enclosure. Below are the T-S parameters. The Ebay pair sold for $624. Not sure what B&W gets for them. Thinking that the high efficiency, negligible Xmax, high Fs and subsequent higher high pass crossover point might work well in a dipole. They also have a high Qts, but I don't think this matters for the 300-5000? range I'd be using them.
An externally hosted image should be here but it was not working when we last tested it.
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The max SPL you can reach with a dipole is based off of the degree of cancellation between the front and rear wave and the volume displacement of the driver.
The B&W has a surface area of 162cm square according to zaph, with an xmax of 1mm. This gives it a volume displacement of 16cm^3.
Assume a 20cm wide baffle that would set the path difference to 10cm for good dipole radiation.
In Linkwitz' spread sheet for calculating just this you can input the parameters and it details the amount of volume displacement you would require to hit a given SPL.
If we assume a max SPL of 110dB then for a closed box the FST will be capable of hitting that at just below 400Hz. A 4th order acoustic LWR slope at 300Hz here makes good sense because the filter is -6dB by 300Hz and the driver will be perfectly capable of this. You could push it down to 250Hz but that's about as far as you can take the driver and expect really good results.
In the 20cm wide OB you would need a crossover point of around 380Hz as the lower limit.
It is worth pointing out that Zaph's xmax figure is most likely guess work as no parameters are to be had for the B&W. Certainly it does not have much linear travel but that is more to do with the flat surround. The motor itself would appear to have more linear travel available. You can infer this by Zaph's distortion measurements, as only the 2nd order shoots up below around 300Hz. This implies a suspension non linearity often encountered in drivers with a suspension limited xmax or non linear surrounds. Sure the overall THD shoots up but the nature of it is benign. The third and higher order harmonics remain well suppressed indicating that the motor is remaining linear.
If you are happy with accepting a bit of 2nd order in exchange for a lower xover point or lower max SPL then this is up to you. I would not however take the FST any lower than 300Hz in a dipole config regardless as the surround may not be too happy with that. It is after all made of a closed cell foam and probably isn't quite as robust as your usual rubber half rolls.
The B&W has a surface area of 162cm square according to zaph, with an xmax of 1mm. This gives it a volume displacement of 16cm^3.
Assume a 20cm wide baffle that would set the path difference to 10cm for good dipole radiation.
In Linkwitz' spread sheet for calculating just this you can input the parameters and it details the amount of volume displacement you would require to hit a given SPL.
If we assume a max SPL of 110dB then for a closed box the FST will be capable of hitting that at just below 400Hz. A 4th order acoustic LWR slope at 300Hz here makes good sense because the filter is -6dB by 300Hz and the driver will be perfectly capable of this. You could push it down to 250Hz but that's about as far as you can take the driver and expect really good results.
In the 20cm wide OB you would need a crossover point of around 380Hz as the lower limit.
It is worth pointing out that Zaph's xmax figure is most likely guess work as no parameters are to be had for the B&W. Certainly it does not have much linear travel but that is more to do with the flat surround. The motor itself would appear to have more linear travel available. You can infer this by Zaph's distortion measurements, as only the 2nd order shoots up below around 300Hz. This implies a suspension non linearity often encountered in drivers with a suspension limited xmax or non linear surrounds. Sure the overall THD shoots up but the nature of it is benign. The third and higher order harmonics remain well suppressed indicating that the motor is remaining linear.
If you are happy with accepting a bit of 2nd order in exchange for a lower xover point or lower max SPL then this is up to you. I would not however take the FST any lower than 300Hz in a dipole config regardless as the surround may not be too happy with that. It is after all made of a closed cell foam and probably isn't quite as robust as your usual rubber half rolls.
Thank You so much for you excellent analysis. I'm thinking of mating the LF00264 with an AE speakers 15" dipole sub. Their site is down so I can't get the model # or TS parameters. I think it had a 12mm Xmax, good low Fs, a Qts in the neighborhood of 0.9. and efficiency of around 93db? So based on these I think was hoping 1 driver would be enough. I think I would prefer to use a DSP on the crossovers anyway so I could hopefully compensate for an FR irregularities. I will need to boost the woofer's output to compensate for the dipole response. I have a lot of reading to do in the Loudspeaker Cookbook. I haven't cracked it in years but I think this project has a chance to be something special.
I was in the coffee shop and I'm not a library. It all depends of the interest of the OP. You have to make a search. Or pay attention to threads... and save.
http://www.diyaudio.com/forums/multi-way/212953-project-ryu-diy-field-coil-loudspeaker-26.html
http://www.diyaudio.com/forums/multi-way/258526-surround-less-spider-less-mid-bass-driver.html
I was in the coffee shop and I'm not a library. It all depends of the interest of the OP. You have to make a search. Or pay attention to threads... and save.
http://www.diyaudio.com/forums/multi-way/212953-project-ryu-diy-field-coil-loudspeaker-26.html
http://www.diyaudio.com/forums/multi-way/258526-surround-less-spider-less-mid-bass-driver.html
I think I'll stick with my FSTs. I couldn't find the kind of detailed objective measurements necessary for good driver evaluation. Just a lot of people having fun.
I know some things about obsession and compulsion. I don't come to this forum to engage in either. So I'm not going to follow some wrongheaded suggestion to earn your respect or pursue this question in some overzealous way. Now your sending me youtube vids of fighter jets. Is there a joke in there somewhere that I'm not getting? I'm just not interested in crank political theories or other conspiracies. When I take the time to open offtopic emails you've sent to me on an DIY audio forum, that's wasted time. Please go sell crazy somewhere else.
I think the FSTs are all basically the same. At least the ones used in the 800 series. At one point they used a ferrite overhung motor for the older 800 speakers but quickly changed to a neo magnet and underhung geometry.
Some of their lower series loudspeakers use FSTs too both with ferrite and neo magnets but from what I can tell these are all overhung. The great thing about the 800 series FST is its very low distortion and high sensitivity. Whether or not the overhung patients also posses similar qualities is unknown.
Some of their lower series loudspeakers use FSTs too both with ferrite and neo magnets but from what I can tell these are all overhung. The great thing about the 800 series FST is its very low distortion and high sensitivity. Whether or not the overhung patients also posses similar qualities is unknown.
An externally hosted image should be here but it was not working when we last tested it.
My current dipole correction for fst
Thank you. I have B&W 804S so I'm familiar with the driver's sound, although I never took it out of the speaker to measure it. Zaph's and other measurements look great, though.
Before these speakers I had B&W CM-4, and while they also had an FST-looking driver, the difference in the sound of the midrange was very noticeable.
Do you use yours with a rod attached to the back, like B&W does?
The sensitivity is high relative to market. But my tweeter is a TPL-150H, so 101 dB, and in that light the FST is relatively low sensitivity. I will run active xo, though. Yet I was hoping to run these with SETs. Decissions!
When I owned N801, I noticed the rod was simply holding the mid driver in place by pulling the driver frame against the resin pod.. This creates a slick and fashionable appearance because the driver frame is almost frameless and without screw holes..
Also molded resin boxes will not have a lot of material for securing screws, the resin material would need other material attached to it.. I've looked into getting some resin tweeter spherical pods and decided to stay with cnc'd wood pods.. The resin pods would require extra work by adding wood material for securing screws.. The advantage of resin is the ability to create an amazing finish surface..
Also molded resin boxes will not have a lot of material for securing screws, the resin material would need other material attached to it.. I've looked into getting some resin tweeter spherical pods and decided to stay with cnc'd wood pods.. The resin pods would require extra work by adding wood material for securing screws.. The advantage of resin is the ability to create an amazing finish surface..
I've always admired the FST midrange. I had them on my 683's. It was the gem of the speaker. Too bad the tweeter wasn't nearly as good. It would be alot of fun trying them in open baffle, play with dsp on them, etc. 300hz means you could run a fast 15" up to 400-800hz and get even lower distortion from the fst. I'd be even curious how the fst horn loads? Also, I think a dealer could get a replacement pair for cheaper than $600. Or go visit the factory with a few under your arms. (Joking!)
They are expensive. But is seems like B&W builds there speakers around these drivers. And yes, I was thinking of using 15" AE dipole woofers with these. Or 2 Eminence. One dipole project uses special made Eminence Alpha's with neo magnets and better Xmax. I supposed this belongs on another thread, but I don't know how low I should expect a 15" to go on an open baffle. The AE 15's have about 12mm Xmax and a Q around 1. I understand the basics of dipole bass reproduction, but I don't know what to compare them to. all else being equal, is a 15" dipole the same as your average 8" in a sealed box?
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