This is the image from Bassbox that shows what they call Heavy Stuffing, filling pretty much the entire box with fill of some kind. This has the effect of increasing the apparent volume that the driver sees. So if you want to use a smaller box fill the inside of it and it will behave as a larger box.
Troels Graveson estimated about 25% extra apparent volume in the tests he did. I ran some impedance tests myself on various stuffing schemes in my line array cabinets and relatively low density fibreglass with a layer of felt on top worked better than any combination of other materials that I tried. Polyester stuffing will work for the volume but I prefer the low density fibreglass myself.
I have attached a pdf Printout from Jeff Bagby's woofer Designer. for the 12BR70 You can see that the standard Vab is 139 litres but at 50 litres with a lot of stuffing Qa = 10 the Q is 0.77 and with a Linkwitz Transform you can be flat with an F3 of 30 Hz at 100dB and not exceed xmax or power rating.
Making the box bigger will reduce the amplifier power needed if that is a trade off you want to make. If you have enough power then 50 to 60 litres well stuffed seems perfectly reasonable.
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Hi,
the project slowly begins. I ordered the parts for DSP. When the DSP is running I'm going to build the subs.
I made some simulations and I'm okay with corner placing. The bigger room has a better behavior in the low frequencies but for now I will stay in my smaller room.
Thank you for the simulation fluid. This is really great because I can save a lot of space. The amplifier has 2x 330W @8Ohm. This should be no problem. But my DSP has 8 channels/outputs and I realized that this is a bit limiting if I need to delay some of the subs. I need one channel for every sub so I can only build a 3-way speaker. For the start this is okay. But if I want to expand my systems I need another DSP or use two outputs from my studio interface.
My plan is a 3 way: HF10AK in 30cm tractrix+ 12PE32 in reflex enclosure without horn+ 4 subs
With a x-over around 1,2khz there should be an even dispersion. The 12PE32 seems like a great midbass. Only downside is that it won't be a closed box.
It's different from what I wanted but I can expand this system later on. I can add a midbass horn and a bigger midrange horn to get a 4way speaker when I have a bigger room. I couldn't find a solution for my dilemma with high frequencies on 2" or 1,4" drivers and I don't want to make big compromises in the highs.
There are some speakers of this kind so I'm confident to get a nice result. Of course I need to try the HF10AK in the tractrix. But Faital uses some tractrix horns so I hope the tractrix curve will work on this driver. I'm okay with the beaming and the small sweet spot.
the project slowly begins. I ordered the parts for DSP. When the DSP is running I'm going to build the subs.
I made some simulations and I'm okay with corner placing. The bigger room has a better behavior in the low frequencies but for now I will stay in my smaller room.
Thank you for the simulation fluid. This is really great because I can save a lot of space. The amplifier has 2x 330W @8Ohm. This should be no problem. But my DSP has 8 channels/outputs and I realized that this is a bit limiting if I need to delay some of the subs. I need one channel for every sub so I can only build a 3-way speaker. For the start this is okay. But if I want to expand my systems I need another DSP or use two outputs from my studio interface.
My plan is a 3 way: HF10AK in 30cm tractrix+ 12PE32 in reflex enclosure without horn+ 4 subs
With a x-over around 1,2khz there should be an even dispersion. The 12PE32 seems like a great midbass. Only downside is that it won't be a closed box.
It's different from what I wanted but I can expand this system later on. I can add a midbass horn and a bigger midrange horn to get a 4way speaker when I have a bigger room. I couldn't find a solution for my dilemma with high frequencies on 2" or 1,4" drivers and I don't want to make big compromises in the highs.
There are some speakers of this kind so I'm confident to get a nice result. Of course I need to try the HF10AK in the tractrix. But Faital uses some tractrix horns so I hope the tractrix curve will work on this driver. I'm okay with the beaming and the small sweet spot.
The 12PE32 seems to work OK in a closed box to me. This is vented in blue vs closed in green. EQ to flatten the response still leaves enough output to match your 4 subs and a 12dB electrical crossover would give 24dB acoustic at about 80Hz to match your subs from eyeballing the graph. They both want a similar volume around 15 to 16 litres net so you could try both by stuffing the port or making the port removable and adding a cover plate.
Faital 12FH320 gives similar response but has much more xmax, still not exceeding xmax at 200W input in a closed box Purple trace.
Faital 12FH320 gives similar response but has much more xmax, still not exceeding xmax at 200W input in a closed box Purple trace.
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I simulated the driver with 30L and tuned to 85hz (recommendation from B&C). The blue line is the closed box in 30L. The difference looks pretty big just from looking. I know what happens in my room but still... The second is 15L in both boxes like you simulated and the difference is not that big. What do you think? Is 15L better to match the subs?
I would prefer to EQ as little as possible. The 12PE32 is set because it works perfect in horns for a later upgrade. And it has nice specs like the low mms which might be helpful for the mids. Low xmax is the price to pay.
I would prefer to EQ as little as possible. The 12PE32 is set because it works perfect in horns for a later upgrade. And it has nice specs like the low mms which might be helpful for the mids. Low xmax is the price to pay.
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30L gives a non flat bass response from a higher Q, I think sealed will be much easier to integrate with the subs and the difference is not huge but with low xmax the extra bump might be worthwhile.
12PE32 is apparently no longer in production if that matters to you. Faital also have the 12PR300 which has low mms, not quite as low as the 12PE32 but has nearly 5mm of xmax which would be more breathing room in a sealed cab.
You will need to EQ to get the best response, I don't understand the idea behind using an active system and then wanting to go easy on the EQ. Your really just cutting to take away the excess response where you don't need it.
Active lets you mix drivers that would not work together passively, if you want minimal active the drivers need to chosen more carefully.
Thanks Fluid for that input. 40 hz at 108 db is a very honorable result. And imho will suffice most of the musics and dynamic peaks with a domestic average spl level (85 db?). So yes my question was related to the use of such 12" at their lowest Fs tunning in order just to use the subs for the first octave with plate amps or stay at a 40 hz F3. Indeed Linkwitz transforms shorten the headroom of cone exursion.
So 111 db is 160 W, 114 db 320 W if I"m ok with the math ? It means the amp for that way must be strong to acheive such levels in case of instant dynamic peaks if present in the reccording.
115 dB if Xmax is not reached seems a good targett for the majority of todays reccordings that are compressed. Or maybe Xmax is not a problem for instant peaks if they last 0,1 second as a drums attack, then as far as the Xvar is not reached, it's so short in time one doesn't care about distorsion? It's hided by the rest of the music and too short for the brain to notice short times distorsions and their harmonics ?
Feel free not to answer as the question is maybe if off topics. But as Drunberg is ok with vented, it may give further driver choices?
I reopen J. Bagbys (RIP) spreadsheet to play, I forgotten all the good possibilities of his Excels..
Edit, you have experienced many 12", is there one you consider more for the snap, chest impact behavior please, or anyway with EQ w
A d active aml we don't care ? Qtc belkw 0,8 is ok or equivalent in vented ?
So 111 db is 160 W, 114 db 320 W if I"m ok with the math ? It means the amp for that way must be strong to acheive such levels in case of instant dynamic peaks if present in the reccording.
115 dB if Xmax is not reached seems a good targett for the majority of todays reccordings that are compressed. Or maybe Xmax is not a problem for instant peaks if they last 0,1 second as a drums attack, then as far as the Xvar is not reached, it's so short in time one doesn't care about distorsion? It's hided by the rest of the music and too short for the brain to notice short times distorsions and their harmonics ?
Feel free not to answer as the question is maybe if off topics. But as Drunberg is ok with vented, it may give further driver choices?
I reopen J. Bagbys (RIP) spreadsheet to play, I forgotten all the good possibilities of his Excels..
Edit, you have experienced many 12", is there one you consider more for the snap, chest impact behavior please, or anyway with EQ w
A d active aml we don't care ? Qtc belkw 0,8 is ok or equivalent in vented ?
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Sorry, I was not clear about EQing. I'd like to avoid increasing the low end because of efficiency and the low xmax. Of course cutting is no problem. But in my mind I was going to match the closed box curve with the vented box. To get the same response from closed box I'd need to add some db in the lower range and that's what I want to avoid. But as you sad there is no need to match them.
The 12PE32 is still available right now. This shouldn't be a problem if I don't wait too long with ordering a pair. Should I take 8 or 16 Ohm? As you are talking about max spl etc. 8 Ohm should be better for closed/vented box and 16 Ohm better for horn, isn't it?
Please no further driver
I'm happy that I finally found a solution for my dilemma. And if the 12PE32 works in a closed box that's even better for me. I'm pretty sure that one day I will use a midbass horn that's why I focused on this driver.
Oh yes, it's also a dream for me to have a mid-bass long horn (say circa 40/80-200/300 hz mainly, upper bass-low mid so). But due to the difficulty for integreation and sounding stage with low dimensionned room & close listening position at home...& price (my hands are not woody proof, uh !)... well a direct driver is ok for me !
I don't know the answer to that question but most drivers are not behaving that well at xmax, most are compliance limited rather than excursion limited. Lots of research shows that harmonic distortion is not that audible even in extreme amounts, but lowering harmonic distortion also tends to lower other types of distortion so it can be hard to know the exact reason why something is preferred. Avoiding drivers being smashed into the bump stops is always a good idea though
Very true, another great loss to the diy audio world
I don't have much direct experience of 12" pro drivers, but my understanding and experience on this point is that the effect is more pronounced the bigger the cone and that it has more to do with volume and a bump in EQ in the 80 to 160 Hz range. So the best 12" for it would be a 15 or 18
I suspect the 8 Ohm driver will be more flexible in use but unless you plan to go super loud in practice either would work.
Most amps are voltage limited due to the power supply rails and are not designed to give huge power into high impedances. Most amps deliver more power into a 4 ohm load than an 8 Ohm one which would be worse for a 16 Ohm driver.
This post below has some input from Tom Danley and to me suggests that an efficient horn will increase the impedance seen by the amplifier which would suggest that a higher impedance driver may not be ideal for a horn. I suspect it depends on the specific horn being used.
16 ohm drivers are usually used when a light load and less power is needed or when arrayed and parallel wired so the impedance doesn't get too low
Horn impedance effects
- what sense would that make if there was no benefit to higher impedance?
The study they did on golden ears site (I think) with headphones and square waves....the higher ohm drivers were more accurate...but I've heard different theories why a higher ohm may be more accurate...like voice coil weight....but when that was said others would say that voice coils don't differ in weight among ohm versions of the same driver....I theorized that the higher ohms aka higher resistance is akin to higher compliance of a suspension....but I am far from the empirical
Golden ears, headphones, milliwatts not exactly the same situation.
There are good reasons to use a 16 ohm driver as part of a system design valve amps would like them too. For a solid state amp that may be required to deliver a lot of power they make less sense when used as singles.
Parallel connections are often preferred when connecting multiple speakers but they halve the impedance each time and most amps are not designed to work well at 2 ohms and below.
You won't find many if any 16 ohm drivers in a hifi speaker companies catalogue. They come from pro sound where speakers are expected and often need to be arrayed to achieve the spl.
There are good reasons to use a 16 ohm driver as part of a system design valve amps would like them too. For a solid state amp that may be required to deliver a lot of power they make less sense when used as singles.
Parallel connections are often preferred when connecting multiple speakers but they halve the impedance each time and most amps are not designed to work well at 2 ohms and below.
You won't find many if any 16 ohm drivers in a hifi speaker companies catalogue. They come from pro sound where speakers are expected and often need to be arrayed to achieve the spl.
Stereophile measurements show an unrealistic rise in the low frequencies due to the nearfield splicing method used by JA, it is not real though, he knows about it but keeps it the same for comparison to older measurements. There is a good comparison in bikinpunks Measurement thread where he compares a nearfield splice to ground plane measurement.
Hi,
after waiting two long months my DSP was finally delivered. It will take some time until I get everything to work since it’s diy. But I wanted to order the drivers because they are not in stock and it will take 3-4 weeks until they arrive.
My shopping cart so far:
-2x HF10AK (16 Ohm)
-2x 12PE32 (8 Ohm)
-4x 12BR70 (8 Ohm)
I’m unsure with the wires and connections. The connection between DSP and the amps will be with with XLR and Cordial CMK 222 microphone cable which I already use for studio purpose. But from the amps to the drivers I’m not sure (distance ~3-5m). Should I go for 1,5mm² in the mids/highs and 2,5mm² for the subs (for example Cordial CLS215 and CLS225 / Sommer Meridian SP225 and SP215)? The cable for the subs will be longer of course. Inside the box I could use 1,5mm² for the subs and 0,75mm² for the mids. The HF10AK has no box, it will be open on top of the box with the 30cm tractrix. Here I would directly use the 1,5mm² coming from the amp. This driver has faston 6,3 x 0,8mm terminals. Is it better to solder the cable to it or use quick disconnect tabs? I think the subs have that Faston terminal too.
Is something like the Visaton VS 77 terminal okay for mids and subs? Or is speakon better for the subs?
I feel like all these things are a matter of taste but since I have no preference the opinion of an experienced person could be very helpful.
after waiting two long months my DSP was finally delivered. It will take some time until I get everything to work since it’s diy. But I wanted to order the drivers because they are not in stock and it will take 3-4 weeks until they arrive.
My shopping cart so far:
-2x HF10AK (16 Ohm)
-2x 12PE32 (8 Ohm)
-4x 12BR70 (8 Ohm)
I’m unsure with the wires and connections. The connection between DSP and the amps will be with with XLR and Cordial CMK 222 microphone cable which I already use for studio purpose. But from the amps to the drivers I’m not sure (distance ~3-5m). Should I go for 1,5mm² in the mids/highs and 2,5mm² for the subs (for example Cordial CLS215 and CLS225 / Sommer Meridian SP225 and SP215)? The cable for the subs will be longer of course. Inside the box I could use 1,5mm² for the subs and 0,75mm² for the mids. The HF10AK has no box, it will be open on top of the box with the 30cm tractrix. Here I would directly use the 1,5mm² coming from the amp. This driver has faston 6,3 x 0,8mm terminals. Is it better to solder the cable to it or use quick disconnect tabs? I think the subs have that Faston terminal too.
Is something like the Visaton VS 77 terminal okay for mids and subs? Or is speakon better for the subs?
I feel like all these things are a matter of taste but since I have no preference the opinion of an experienced person could be very helpful.