From the moderate amount of testing I have done at home of various drivers and speakers, I have found that most of the big FR variations between 100 and 500 hz are room/reflection related. With systems, sometimes there are broad dips/ peaks in the mid bass due to box size and tuning (for ported boxes ).
Usually dips between 200 and 300 hz, when measured from 1-3 meters, seem to be cancellations from floor bounce------first reflections off the floor, and the ceiling. If you place the mic 1 cm off the cone and run a sweep, it should look much smoother. This gives you an idea of what the driver itself is doing. It is usually pleasantly smooth to 800hz or so, with a rising response until the upper mids on many drivers.
You would have to measure the output of the horn separately, and mathematically merge the measurements to get an accurate picture of the overall response. I think that this is called a quasi-anechoic measurement---because it largely takes away the effect of the room.
Most back loaded horns are too small to behave like true horns in the bass range, so there are standing waves that establish themselves within the horn, and like transmission lines, there are cancellations that occur between the driver direct output and the horn output at multiples of fundamental standing wave frequencies (pipe resonances) that have some effect up through about 1000hz. Martin King has done some of the most authoritative writing on this subject. SEE: http://www.quarter-wave.com/
Usually dips between 200 and 300 hz, when measured from 1-3 meters, seem to be cancellations from floor bounce------first reflections off the floor, and the ceiling. If you place the mic 1 cm off the cone and run a sweep, it should look much smoother. This gives you an idea of what the driver itself is doing. It is usually pleasantly smooth to 800hz or so, with a rising response until the upper mids on many drivers.
You would have to measure the output of the horn separately, and mathematically merge the measurements to get an accurate picture of the overall response. I think that this is called a quasi-anechoic measurement---because it largely takes away the effect of the room.
Most back loaded horns are too small to behave like true horns in the bass range, so there are standing waves that establish themselves within the horn, and like transmission lines, there are cancellations that occur between the driver direct output and the horn output at multiples of fundamental standing wave frequencies (pipe resonances) that have some effect up through about 1000hz. Martin King has done some of the most authoritative writing on this subject. SEE: http://www.quarter-wave.com/
This is great, thanks Howard! Gives me some ideas to try and material to go through. I will come back with a more useful set of measurements as well.
Reading up on the Dallas II enclosure, it seems more convincing indeed, but that would be a much bigger project right now. It also opens the question of other designs, other drivers..
Can I ask which BLH implenentation(s) is/are considered the absolute best right now? Enclosure/driver combo.
@321elements, its early days, but broadly speaking, I would call it balanced now, if still just slightly dry/lean. Space has improved, calmer and deeper.
80s pop/rock is still unbarable on them, but decent jazz/classical recordings are quite enjoyable.
I need to do some more reading up on phase response, any good material online you can suggest?
Reading up on the Dallas II enclosure, it seems more convincing indeed, but that would be a much bigger project right now. It also opens the question of other designs, other drivers..
Can I ask which BLH implenentation(s) is/are considered the absolute best right now? Enclosure/driver combo.
@321elements, its early days, but broadly speaking, I would call it balanced now, if still just slightly dry/lean. Space has improved, calmer and deeper.
80s pop/rock is still unbarable on them, but decent jazz/classical recordings are quite enjoyable.
I need to do some more reading up on phase response, any good material online you can suggest?
1. Measurement from 1cm (driver/horn), no filter, straight into ACA. THe level/volume was kept at the same position between the horn/driver measurements.
2. Driver from 1cm; no filter vs. 8R2 || 3.3 mH - this is overdone, it attenuates too low, 2.2mH should be about right
What do you think? I'm still most suspicious of that 700hz peak, clearly not room related. Is there something to do about it, without getting into a notch filter?
2. Driver from 1cm; no filter vs. 8R2 || 3.3 mH - this is overdone, it attenuates too low, 2.2mH should be about right
What do you think? I'm still most suspicious of that 700hz peak, clearly not room related. Is there something to do about it, without getting into a notch filter?
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I suppose the first thing you should do is to assess your goals with this project. You’re further along in your full range project than I am, but your frequency response does not bother me to look at. I think it’s pretty amazing that a single driver in a box can do that. Personally I’d put the microphone away and start tuning things with my ears now. You have verified that it’s not broken and now it’s time to tailor to your preferences. At least that’s my plan.
The other option is to digital correction which I’ve not particularly enjoyed. I’ve had better results cutting than boosting but flattening out the response is going to come at a cost (my personal opinion). If I were going to go that route, I’d do it in the digital domain (ideally before it gets fed to my DAC).
For me, and I’m an absolute newb at this whole enclosure building full range thing, we’re in the appreciating the differences territory. Appreciating what happens when you remove a crossover network from the equation. What is the speaker doing right that just can’t be done in a 2 or 3 or 4 way design? I’m less concerned about being a few decibel’s high at 700hz. If scientific perfection existed here, there’d be little reason to have options. Sorry for the rant. I think you’re doing awesome. I just think it’s time to start enjoying them.
The other option is to digital correction which I’ve not particularly enjoyed. I’ve had better results cutting than boosting but flattening out the response is going to come at a cost (my personal opinion). If I were going to go that route, I’d do it in the digital domain (ideally before it gets fed to my DAC).
For me, and I’m an absolute newb at this whole enclosure building full range thing, we’re in the appreciating the differences territory. Appreciating what happens when you remove a crossover network from the equation. What is the speaker doing right that just can’t be done in a 2 or 3 or 4 way design? I’m less concerned about being a few decibel’s high at 700hz. If scientific perfection existed here, there’d be little reason to have options. Sorry for the rant. I think you’re doing awesome. I just think it’s time to start enjoying them.
bridger2086:
Did you try moving the mic around in different spots (still close to the cone)? Whizzers, as I understand it, can have phase interferences with the main cone, and perhaps across their own diameter.
Maybe, see if the bumps are reduced if you move the mic out to 30cm or so, and from side to side. It seems like the most troublesome bumps are the ones that are picked up no matter where you measure.
Since it is easy to do, you might try stuffing the compression chamber with wool or fiber-fill to see if that has an effect on the bump at 700hz or just to learn what such a treatment does generally. I have done this to smooth out the midrange for drivers (that were in small sealed transmission lines).
It is not just the hump around 700hz, but the dip that is above it which is curious. If you are interested in learning/experimenting some, you could take a driver out, mount it in a sheet of plywood, and measure it from various distances. See what characteristics change. You could even put the driver in a sheet of cardboard or foam core board if the plywood is too expensive/troublesome.
Did you try moving the mic around in different spots (still close to the cone)? Whizzers, as I understand it, can have phase interferences with the main cone, and perhaps across their own diameter.
Maybe, see if the bumps are reduced if you move the mic out to 30cm or so, and from side to side. It seems like the most troublesome bumps are the ones that are picked up no matter where you measure.
Since it is easy to do, you might try stuffing the compression chamber with wool or fiber-fill to see if that has an effect on the bump at 700hz or just to learn what such a treatment does generally. I have done this to smooth out the midrange for drivers (that were in small sealed transmission lines).
It is not just the hump around 700hz, but the dip that is above it which is curious. If you are interested in learning/experimenting some, you could take a driver out, mount it in a sheet of plywood, and measure it from various distances. See what characteristics change. You could even put the driver in a sheet of cardboard or foam core board if the plywood is too expensive/troublesome.
Good tip, i will try experimenting a bit more with measuring to get a sort of an averaged response.
The compression chamber is completely filled with mineral wool (by previous owner). I actually just got some acoustic felt, 8mm and 20mm, to experiment with. Some seem to even prefer these drivers without any damping behind it, but it doesnt really seem likely in the fostex horn, which has a rather shallow space behind it, with all parallel walls.
This peak at 700hz (and dips both side of it) i picked up with my ear even before measuring, so its a bit of a comfirmation. We'll see what happens with damping.. measuring in an open baffle might be revealing too, as you say.
The compression chamber is completely filled with mineral wool (by previous owner). I actually just got some acoustic felt, 8mm and 20mm, to experiment with. Some seem to even prefer these drivers without any damping behind it, but it doesnt really seem likely in the fostex horn, which has a rather shallow space behind it, with all parallel walls.
This peak at 700hz (and dips both side of it) i picked up with my ear even before measuring, so its a bit of a comfirmation. We'll see what happens with damping.. measuring in an open baffle might be revealing too, as you say.
On the other hand it's these ones that are more likely to respond well to equalising.
AllenB said: "On the other hand it's these ones that are more likely to respond well to equalising".
Yes, that makes sense. I have heard my FE166E BLH speakers with room-type EQ applied, and it did seem to help; though for me they are listenable as is. The FE206E I have are a little more cantankerous.
Yes, that makes sense. I have heard my FE166E BLH speakers with room-type EQ applied, and it did seem to help; though for me they are listenable as is. The FE206E I have are a little more cantankerous.
Great vocabulary flex there Howard! 😀 But its exactly how I would describe them and in a way also why i think its worthwhile tinkering with them. There are moments where they really impress - spectacularly so even. Other times they seem to go deliberately against the mix. 80s music in general is one such example.
My bedroom system however, with the tiny SA LS35A sitting on top of Ikea pine cabinets, against the wall is a perfect antidote for that. The combination of those pine cabinets resonating and proximity to wall gives a true-full range response, with -5db at 20hz! (but a massively bloated midbass). 80s music sounds wonderfull and there is enough competence that even better recorded/mixed music isn't unbearable.
These same speakers sound like a small radio in the living room where the fostex horns are. Integration is key, which got me thinking, what sort of rooms do these 8 inch fullrange drivers in BLH enclosures perform best?
My bedroom system however, with the tiny SA LS35A sitting on top of Ikea pine cabinets, against the wall is a perfect antidote for that. The combination of those pine cabinets resonating and proximity to wall gives a true-full range response, with -5db at 20hz! (but a massively bloated midbass). 80s music sounds wonderfull and there is enough competence that even better recorded/mixed music isn't unbearable.
These same speakers sound like a small radio in the living room where the fostex horns are. Integration is key, which got me thinking, what sort of rooms do these 8 inch fullrange drivers in BLH enclosures perform best?
Hey thanks, I appreciate your opinion! I started this thread with technical discussions in mind, but also, lets call it - philosophy behind it. I most definitely am enjoying them. Its sort of a game of putting on a tinkerers hat, than other times hedonist one. 🙂
My slight obsession with bass also comes from the fact that I do a lot of quiet listening when the family is asleep. Compounded by my affinity for bass instruments, its a bit bothersome that they don't quite come up in the mix, on those occasions when the volume is turned down.
I tried avoiding a preamp, filters and such, keeping it direct and minimalist. But i might just need to consider building a sort of contraption, a buffer/passive preamp, with some line level filtering options for the "loudness" effect.
Has somebody built such a thing?
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Out of curiosity, do you know what the resonant frequency of the enclosure is? If it happened to fall into that 700hz territory, perhaps it could be pushed up a little and kill two birds with one stone. It’s a long shot, but worth exploring .
When your bass is balanced it sounds the same whether it is loud or quiet, and a loudness control makes it worse.
However room modes can be insidious, and a very common problem which is difficult to manage. It's possible that if parts of your bass are below a certain level you can lose them. Sometimes a loudness control can actually be an improvement there, even though it still isn't the correct fix.
“On second thought, maybe that’s just what this driver does?”
I found a few measurements that I made of one of my FE206E (stock cones, but with duct-seal between the magnet and frame and dampening material on the frame spokes). All were made at 12”/30cm, one at 20 degrees off axis, one with a version of the 98cent tweak-poly-fill stuffed between the cone and the whizzer. All were made with no baffle, just bare, sitting on the couch. The big peak/dip either side of 1000hz is not there in any of them.
I found a few measurements that I made of one of my FE206E (stock cones, but with duct-seal between the magnet and frame and dampening material on the frame spokes). All were made at 12”/30cm, one at 20 degrees off axis, one with a version of the 98cent tweak-poly-fill stuffed between the cone and the whizzer. All were made with no baffle, just bare, sitting on the couch. The big peak/dip either side of 1000hz is not there in any of them.
I could understand various reasons that one would strive to use the FE206En drivers alone but:
What about doing a WAW(woofer assisted wide-range)?
I have done this with happy results.
Are you open to the idea of adding smallish woofer-stands and two more amp channels?
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Very pliable leather, glued on, probably with E-6000 (solvent based, like Goop or Goo brands, that are sold in squeeze tubes at hardware stores in the USA), wrapped around the spokes and clamped with small spring clamps (or clothespins?) Any glue that sticks to leather would likely work.
There is a type of leather called “deer-tanned cowhide” which is not too expensive, but is quite supple/flexible. Actual deer skin costs much more. But since you don't need much, buying either new might seem expensive. Maybe recycle an old split-leather or suede clothing article?
I have also seen wool teased out and lightly placed in the space between the back of the cone and the frame, which should damp down reflections in that area. This probably would not work so well (?) on drivers that have greater excursion capabilities, but I don't know for sure.
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Here is a link to a site with FE206e and FE206en tweaks:
https://diyaudioprojects.com/Drivers/Fullrange-Modifications-Tweaks/
SECURITY NOTICE
Without naming the site I had trouble with (not the one in this message) remember: be careful with links to and from sites that are not https secure.
Especially worth noting: Recently I got suckered into clicking “I am not a robot” on my way to a linked site (never got there), and suffered a horrible barrage of “notifications” that were persistent, disruptive and loud (I eventually was advised to turn off “notifications”; that worked). The notifications that continually popped up in the lower right of the screen, wanted me to click on them----no thanks!!!
https://diyaudioprojects.com/Drivers/Fullrange-Modifications-Tweaks/
SECURITY NOTICE
Without naming the site I had trouble with (not the one in this message) remember: be careful with links to and from sites that are not https secure.
Especially worth noting: Recently I got suckered into clicking “I am not a robot” on my way to a linked site (never got there), and suffered a horrible barrage of “notifications” that were persistent, disruptive and loud (I eventually was advised to turn off “notifications”; that worked). The notifications that continually popped up in the lower right of the screen, wanted me to click on them----no thanks!!!
Second time that link has come up… i covered all of the mods, some here are not well done.
https://www.diyaudio.com/community/threads/kirishima-medicine-for-blh-bug.390785/post-7136381
dave
https://www.diyaudio.com/community/threads/kirishima-medicine-for-blh-bug.390785/post-7136381
dave