Dear Tubino,
Of course you can mount it on the corner for increased bass, but firing directly on a back to front wall direction you may loose HF and sounstage clarity. Installing them tilted inwards could do the trick.
There are many ways of increasing bass reach, all of them involve a saw 😀
The easiest way is cutting the sides of the final part of the rear horn and opening them "as a book" to increase the mouth's width, prolonging the wood panels until they reach the front. Of course you must keep some columns of wood for structural strength. That if you don't care about a bigger box 😉 😉
You an calculate the final area and compare it with the above table#2.
I got to go...
M
Of course you can mount it on the corner for increased bass, but firing directly on a back to front wall direction you may loose HF and sounstage clarity. Installing them tilted inwards could do the trick.
There are many ways of increasing bass reach, all of them involve a saw 😀
The easiest way is cutting the sides of the final part of the rear horn and opening them "as a book" to increase the mouth's width, prolonging the wood panels until they reach the front. Of course you must keep some columns of wood for structural strength. That if you don't care about a bigger box 😉 😉
You an calculate the final area and compare it with the above table#2.
I got to go...
M
maxlorenz said:
I've got a saw -- and I'm not afraid to use it! But I think the EASIEST way would be to add flare wings to the front, and continue the horn THAT way. If I put them in the corners, tilted in, then it would be easy-peasy to put in place a wing to extend the bottom to the wall, for example.
The high-frequency shouldn't be a problem I think, because when on their side, these cabinets in the corner would still put the driver about 5 feet from the side wall. The problem I have is that the corners I intend to use are NOT that far apart, so the space between the Left and Right channels gets too small!
I could also see adding a wing on top, slanting forward... I will need to start making paper and cardboard models to illustrate!
Yes, well, there are easier ways too of course.
Remember that a back-loaded horn is a compromise compared to a 'real' horn. The latter is front-loaded, and the sealed rear-chamber is tuned to the same frequency as the horn to present a near equal load to both sides of the diaphram (alternatively you could bolt an identical horn to the rear of the driver). A BLH does not have equal loading on both sides of the diaphram. What is often called a compression chamber in a BLH is really little more than a low-pass filter chamber. The listening-room forms the compression-chamber of a BLH, so there's an inherent mismatch there.
Once you realise that, you can start looking at them in a different way. 90% of BLHs can be regarded as a small (i.e. undersized) bass reflex box coupled to a gigantic vent. The vent needs to be gigantic because the chamber Vb is so small; ergo, the horn provides all the LF gain & extension. Despite being relatively gigantic by most people's standards, most are actually under-sized (or they'd be impossibly large for the majority of people), and either use the room reflection-boundary conditions to complete the horn expansion & dramatically increase the mouth size, or use QW loading at the bottom-end, and shift to horn loading as the acoustic-impedance match at the mouth / terminus improves.
Another take is the Big Vent Reflex approach. Assuming that we keep the 'all BLHs are really just extreme variations of BR cabinets' analogy, you can design a full-sized reflex box (or something intermediate) for the driver. With these boxes, the cabinet passband is narrower (like a normal BR box), and is not / less dependant on the horn to provide the gain & extension. So you can make the horn smaller. It no longer needs to be ideally 1/2 wavelength of Fc long & have a mouth circumference = wavelength of Fc. The horn will reduce pressure in the vent (due to the rapid expansion), provide a large scale to the sound (obvious), and function as a waveguide. Like the more usually seen BLHs, they have compromises, but they can be very effective, they're nice & simple, and considerably more compact for a given tuning. I did the attached example for a 15in Monacor PA driver last week. It's good for 100db 1w / 1m to 35Hz, with an F10 of ~24Hz before room-gain is factored in.
Remember that a back-loaded horn is a compromise compared to a 'real' horn. The latter is front-loaded, and the sealed rear-chamber is tuned to the same frequency as the horn to present a near equal load to both sides of the diaphram (alternatively you could bolt an identical horn to the rear of the driver). A BLH does not have equal loading on both sides of the diaphram. What is often called a compression chamber in a BLH is really little more than a low-pass filter chamber. The listening-room forms the compression-chamber of a BLH, so there's an inherent mismatch there.
Once you realise that, you can start looking at them in a different way. 90% of BLHs can be regarded as a small (i.e. undersized) bass reflex box coupled to a gigantic vent. The vent needs to be gigantic because the chamber Vb is so small; ergo, the horn provides all the LF gain & extension. Despite being relatively gigantic by most people's standards, most are actually under-sized (or they'd be impossibly large for the majority of people), and either use the room reflection-boundary conditions to complete the horn expansion & dramatically increase the mouth size, or use QW loading at the bottom-end, and shift to horn loading as the acoustic-impedance match at the mouth / terminus improves.
Another take is the Big Vent Reflex approach. Assuming that we keep the 'all BLHs are really just extreme variations of BR cabinets' analogy, you can design a full-sized reflex box (or something intermediate) for the driver. With these boxes, the cabinet passband is narrower (like a normal BR box), and is not / less dependant on the horn to provide the gain & extension. So you can make the horn smaller. It no longer needs to be ideally 1/2 wavelength of Fc long & have a mouth circumference = wavelength of Fc. The horn will reduce pressure in the vent (due to the rapid expansion), provide a large scale to the sound (obvious), and function as a waveguide. Like the more usually seen BLHs, they have compromises, but they can be very effective, they're nice & simple, and considerably more compact for a given tuning. I did the attached example for a 15in Monacor PA driver last week. It's good for 100db 1w / 1m to 35Hz, with an F10 of ~24Hz before room-gain is factored in.
Attachments
SPH-390TC. An excellent alternative is the Eminence Gamma 15, though that rolls off a touch more below 100Hz -not automatically a bad thing, as room-gain will lift everything below this point anyway. That's actually the kind of response a lot of designers build into their cabinets from the off. I generally tend to use nominally flat however, & let people adjust them to suit their own taste / room / system, because assuming a one-size-fits-all is like saying that every bloke on the planet thinks a night with Gwen Stefani would be as good as it gets (I prefer Lauren Laverne myself, not that I think Gwen is lacking on the eye-candy front 😉 ). These kind of cabinets are relatively forgiving of the driver used (within reason) so a decent range of drivers should slot in & perform respectably.
I assume you are using both voice coils in parallel on that driver? Which MJK worksheet are using to calculate such BVR?
Scottmoose said:
Scottmoose, this post was extremely useful to me. I have been trying to understand different ways to compare loading via BR vs BLH, but don't know enough... what you posted is wonderfully clear.
But of course it raises more questions. 🙂 For nefarious reaons, I'd like to use a 12" in a BLH designed for a 15", so Saturday I made a pair of adaptor rings, seen here:
An externally hosted image should be here but it was not working when we last tested it.
It fits both driver and cabinet very well, and required NO permanent cabinet mod (used existing T-nuts to mount), and I can now try an Altec 414-16B in a Tannoy GRF-R cab:
An externally hosted image should be here but it was not working when we last tested it.
But now the questions: If properly designed in the first place for the larger driver, the jury-rigged smaller driver will have too much space behind it, and won’t load properly, resulting in bass being boomy or lacking bass. Is that pretty much right?
Is there a way to cheat? If the larger (relatively) space is there, maybe I can modify throat a little, and use a differently spec'ed driver... What if the smaller driver has a higher Qts than would normally be used in a horn? Wouldn’t that mean – as it moves up the Qts scale toward open baffle – that it would require less loading, and just might work with the oversize backloaded horn?
A full-range driver would be interesting, so I look at the Audio Nirvana drivers:
Super 12: Fs 33, Qts .049
Super 10: Fs 36, Qts .29
Super 8: Fs 43, Qts .175
So which, if any, would work? Or would any work, as long as I adjust the volume behind the driver? Maybe that would work with the 12, but the whole thing has to be scaled down for the smaller drivers? The space behind the driver is visible here:
An externally hosted image should be here but it was not working when we last tested it.
Thanks for patience with me. I'm green as grass here.
Tubino wrote:
Wings added to the bass mouth: increase in horn length + mouth area. The first effect will increase bass reinforcement, with eventually lost of balance between LF and HF. It could also bring a phase mismatching, I suppose...
Nevertheless, it would be very interesting if you could make the said winged expanded bass horn plus a front horn for midrange
a monster speaker!
Have fun!
M
Wings added to the bass mouth: increase in horn length + mouth area. The first effect will increase bass reinforcement, with eventually lost of balance between LF and HF. It could also bring a phase mismatching, I suppose...
Nevertheless, it would be very interesting if you could make the said winged expanded bass horn plus a front horn for midrange
a monster speaker!Have fun!
M
What is the depth of the front horn on the Autograph?
What would you estimate is the depth of the midrange front horn on the Autograph? I can imagine working up a bolt-on device to fit snugly over the frame of the Tannoy Gold... If I'm going to the trouble, I would probably aim at making it a round horn...
If the depth added is something like 8 in / 20 cm, it would be easy enough to add that much flare to the horn mouth below... In for a dime, in for a dollar.
maxlorenz said:
Nevertheless, it would be very interesting if you could make the said winged expanded bass horn plus a front horn for midrange
M
What would you estimate is the depth of the midrange front horn on the Autograph? I can imagine working up a bolt-on device to fit snugly over the frame of the Tannoy Gold... If I'm going to the trouble, I would probably aim at making it a round horn...
If the depth added is something like 8 in / 20 cm, it would be easy enough to add that much flare to the horn mouth below... In for a dime, in for a dollar.
Have a look at the front horn on the Tannoy Westminster Royal.
It is probably sized for 200Hz to 1000Hz passband.
It is probably sized for 200Hz to 1000Hz passband.
Depth of Autograph front horn
I looked at these plans:
http://www.geocities.com/tannoy_autograph/Tannoy_Autograph.pdf
It seems reasonably clear that the front horn is about 245mm (9 5/8"), and goes from 394mm to 603mm, or 15.5" to 23 3/4".
On those plans the flare is shown as made up of two angles.
It's interesting to think of adding 10 inches to the front of my speakers...
I looked at these plans:
http://www.geocities.com/tannoy_autograph/Tannoy_Autograph.pdf
It seems reasonably clear that the front horn is about 245mm (9 5/8"), and goes from 394mm to 603mm, or 15.5" to 23 3/4".
On those plans the flare is shown as made up of two angles.
It's interesting to think of adding 10 inches to the front of my speakers...
Sounds favourite -I haven't checked, but I imagine it'd be in that region. The Tannoy designs owe quite a lot to Olson's compound horns.
Re a 12in driver in a 15in box, I wouldn't panic. If it's underdamped, then just damp it down. Remember, it's difficult to have too big a cabinet -you can always damp down what you don't need. It's harder to boost what you don't have in the first place.
Qt is one of the great semi-myths about horns, because it comes back down to what you call a horn. If you use a ~optimal expansion with a full-sized horn, then a high motor power (low Q), or a rising response are essential if no supporting drivers are used for the HF, because you'll suffer HF drop-off. But with a shorter PA style horn (which is what these were often used for, with the caveat that most weren't designed brilliantly), Q is less critical. If it's a good choice for a reflex box, it'll work fine in one of these, assuming the cabinet's designed right. Generally speaking, I say the more motor-power the better, for the same reasons as above: you can always loose what you don't need.
Re the AN drivers, I'd avoid the 12in unit -looks good value, but Vas is through the roof, so it needs a big cabinet (like one of these ironically enough, & preferably larger. I've yet to work out what it's for). The 8in is too small for this box, but the 10in would probably do OK. I'd be inclined to design something specifically for it rather than just drop it in the GRF box though. There isn't really anything special about the Tannoy designs per-se: good cabinets, but they're intended for a specific unit, so if you use something else, although you might get good results, you're unlikely to get the best out of either driver or cabinet.
Re a 12in driver in a 15in box, I wouldn't panic. If it's underdamped, then just damp it down. Remember, it's difficult to have too big a cabinet -you can always damp down what you don't need. It's harder to boost what you don't have in the first place.
Qt is one of the great semi-myths about horns, because it comes back down to what you call a horn. If you use a ~optimal expansion with a full-sized horn, then a high motor power (low Q), or a rising response are essential if no supporting drivers are used for the HF, because you'll suffer HF drop-off. But with a shorter PA style horn (which is what these were often used for, with the caveat that most weren't designed brilliantly), Q is less critical. If it's a good choice for a reflex box, it'll work fine in one of these, assuming the cabinet's designed right. Generally speaking, I say the more motor-power the better, for the same reasons as above: you can always loose what you don't need.
Re the AN drivers, I'd avoid the 12in unit -looks good value, but Vas is through the roof, so it needs a big cabinet (like one of these ironically enough, & preferably larger. I've yet to work out what it's for). The 8in is too small for this box, but the 10in would probably do OK. I'd be inclined to design something specifically for it rather than just drop it in the GRF box though. There isn't really anything special about the Tannoy designs per-se: good cabinets, but they're intended for a specific unit, so if you use something else, although you might get good results, you're unlikely to get the best out of either driver or cabinet.
Scottmoose said:
I'm staring at this... thinking it is kind of an upscaled compression chamber.
How WIDE is the cabinet? I see every dimension on the drawing but that.
Those are very interesting results.
Tubino wrote:
And AndrewT wrote also:
Autograph's front horn is aimed at 250-1000Hz.
Dinsdale's article states frequency cut-off per mouth perimeter, if I recall well.
When you increase midrange reinforcement HF gets relatively weaker; that's one of the reasons why I actively bi-amp my speakers 😉
Cheers,
M
And AndrewT wrote also:
Autograph's front horn is aimed at 250-1000Hz.
Dinsdale's article states frequency cut-off per mouth perimeter, if I recall well.
When you increase midrange reinforcement HF gets relatively weaker; that's one of the reasons why I actively bi-amp my speakers 😉
Cheers,
M
Scottmoose said:
Ow! Ow! (sounds of Tubino as he flagellates self) Okay! Okay!
But... (rubbing back)... what if you turned that driver around and put a sealed box over the back of the speaker (front of the box)? If it fires into a large space several times its own volume, which then constricts into the throat of a horn, isn't that analogous on a grand scale to a compression driver fitted to horn?
The self-flagellation doesn't hurt as much as being this ignorant.
Scottmoose said:
IMPRESSIVE!
😀
Yes, that's basically correct. By reversing the driver, so the front loads into that cabinet, and then adding an appropriately tuned sealed chamber to the rear, you would create a front horn. Albeit not an optimal one because it's not designed to be used in that way.
Remember: a compression chamber is always sealed, almost invariably to the rear of the driver, and is ideally tuned to the same frequency as the horn on the opposite side, to provide a near perfect load on both sides of the diaphram.
An optional filter chamber is not sealed, and couples one side of the driver to the throat of the horn. Its duty is simply to form a low pass filter in conjunction with the horn throat, and roll the horn off above a frequency determined by its volume & the throat CSA.
In a back loaded cabinet, there is no compression chamber, other than the room the cabinets are in (the Vb of which is far too large of course to provide an identical load to that the horn provides), and the net result basically a more-or-less extreme version on the bass reflex theme, depending on which angle you approach it from.
Yes, that's basically correct. By reversing the driver, so the front loads into that cabinet, and then adding an appropriately tuned sealed chamber to the rear, you would create a front horn. Albeit not an optimal one because it's not designed to be used in that way.
Remember: a compression chamber is always sealed, almost invariably to the rear of the driver, and is ideally tuned to the same frequency as the horn on the opposite side, to provide a near perfect load on both sides of the diaphram.
An optional filter chamber is not sealed, and couples one side of the driver to the throat of the horn. Its duty is simply to form a low pass filter in conjunction with the horn throat, and roll the horn off above a frequency determined by its volume & the throat CSA.
In a back loaded cabinet, there is no compression chamber, other than the room the cabinets are in (the Vb of which is far too large of course to provide an identical load to that the horn provides), and the net result basically a more-or-less extreme version on the bass reflex theme, depending on which angle you approach it from.
Hi guys,
A couple of years ago I decided to remove the thick dust caps (I think this is the name) of my Beyma KX15 coaxials because I thought they did not let the HF out freely. Of course by removing them the highs improved significantly, in a way that I no longer miss HF extension. Unfortunately, one of the drivers then started to make ugly sounds on bass heavy (movies...etc) software, then distorted heavily...yesterday I had the courage to disassemble the drivers completely, removed the HF membrane and the woofer cone! 😱
I tell you, the Beymas are very well built. The gaps of the magnet, especially the woofer-s, were dirty, with metal particles that were scratching the voice coil. I cleaned them and assembled back the whole thing. It took me around six hours, including removing the drivers from the enclosures... 🙁
Unfortunately, my daughters were not home to lend me their camera so no picks of the adventure...
It is sounding quite good now. I hope it still does for long.
I learned a few things, like the woofer-s binding posts are connected to the woofer-s tinsel leads by a common iron bolt...I did not had time nor the energy to solder directly the speaker cable (as AndrewT wisely adviced long ago) but I might today.
Here is a link to a newer photo where you can see the waveguide for the HF driver>
http://picasaweb.google.com/lh/photo/iIUYF2v1Xlh4NpM_aIBhTw?feat=directlink
Now I will have to put some fabric on the HF throat to protect the magnetic gap from dust entering...
In my view, the dust cap makes two things> protecting and adding mechanical stiffness to the woofer-s cone.
Apart that, I contacted previously David Dicks from commonsenseaudio because I was considering replacing the Beymas for the lovely P Audio BM15CX38. He has his 15 and 12 incher AN, cast frame, on sale and recommended me the 15inches FR, which is attractive and a lot less expensive than the P Audio, and has the benefit of avoiding the active crossover...on the other hand one maybe has to install a supertweeter due to the lesser response after 15KHz...
He also said that P Audio-s Xmax (maximal voice coil overhang) was 4,5mm and that was too much for this type of enclosures? What do you guys think? Scottmoose?
Anyway, I will be buying soon an AN super 10 cast frame for my future and definitive monster fullranger which will be an adaptation of the Autographs. 😎
Regards,
M
A couple of years ago I decided to remove the thick dust caps (I think this is the name) of my Beyma KX15 coaxials because I thought they did not let the HF out freely. Of course by removing them the highs improved significantly, in a way that I no longer miss HF extension. Unfortunately, one of the drivers then started to make ugly sounds on bass heavy (movies...etc) software, then distorted heavily...yesterday I had the courage to disassemble the drivers completely, removed the HF membrane and the woofer cone! 😱
I tell you, the Beymas are very well built. The gaps of the magnet, especially the woofer-s, were dirty, with metal particles that were scratching the voice coil. I cleaned them and assembled back the whole thing. It took me around six hours, including removing the drivers from the enclosures... 🙁
Unfortunately, my daughters were not home to lend me their camera so no picks of the adventure...
It is sounding quite good now. I hope it still does for long.
I learned a few things, like the woofer-s binding posts are connected to the woofer-s tinsel leads by a common iron bolt...I did not had time nor the energy to solder directly the speaker cable (as AndrewT wisely adviced long ago) but I might today.
Here is a link to a newer photo where you can see the waveguide for the HF driver>
http://picasaweb.google.com/lh/photo/iIUYF2v1Xlh4NpM_aIBhTw?feat=directlink
Now I will have to put some fabric on the HF throat to protect the magnetic gap from dust entering...
In my view, the dust cap makes two things> protecting and adding mechanical stiffness to the woofer-s cone.
Apart that, I contacted previously David Dicks from commonsenseaudio because I was considering replacing the Beymas for the lovely P Audio BM15CX38. He has his 15 and 12 incher AN, cast frame, on sale and recommended me the 15inches FR, which is attractive and a lot less expensive than the P Audio, and has the benefit of avoiding the active crossover...on the other hand one maybe has to install a supertweeter due to the lesser response after 15KHz...
He also said that P Audio-s Xmax (maximal voice coil overhang) was 4,5mm and that was too much for this type of enclosures? What do you guys think? Scottmoose?
Anyway, I will be buying soon an AN super 10 cast frame for my future and definitive monster fullranger which will be an adaptation of the Autographs. 😎
Regards,
M
Hello Max. Can you tell me the steps you took to open up the coil to clean it. And do you think the dirt got in there because of you removing the dustcap.It seems to me it shouldn't have because you said they were metal filings and they usually get created in the coil I think over time on there own. I am curious because I have the same speakers and one of them is having the same problem. And I want to try cleaning the coil if possible without damaging the cone or spider before I buy a replacement.