simple question to horn speaker

[Scottmoose]

Originally posted by bigcatdairy


wow, it seems helpful for me.
like to build a back loaded horn.
by the way, can a horn speaker which using a driver within 64Hz cutoff freq provide 30~40Hz sound?

Yes indeed. You see, within reason, a horn couldn't care less about the free air resonant frequency of the driver. All it needs to operate is pressure at the throat, and it will do the rest across it's operating BW (that's very heavily simplified, but as a basic principle it's true enough). Getting 2 or more octaves below Fs is a doddle if you can go large enough, or, if you can't, then using multiple drivers can compensate for whatever issues you might face due to an undersized box -harmonic nulls, high excursion etc.

You can use higher Q drivers in a horn -however, remember that you might find the HF start to vanish as the driver doesn't have sufficient motor-power to overcome the very high damping the horn places on it.

As for whether the BIB is a horn or not, it is. It's a tapped, chamberless conical corner-horn to be exact. As I mentioned above, if a cabinet expands toward the mouth, then it's a horn. Period. A cone, or any type of expanding 'tube' that is closed at one end & open at the other has the same fundamental resonant frequency and harmonic behaviour as a cyliner that is open at both ends. Resonance thus occurs at lambda / 2, unlike a straight cylinder closed at one end & open at the other, where resonance is at lambda / 4. A horn may therefore be categorised as a 1/2 wave resonator with a 1/4 wave fundamental. Some say that for something to be defined as a horn, it must match the impedance of the diaphram to the air at Fc. Strictly speaking, that's not really true. Impedance matching at Fc might be a design objective, but the true measure is if it expands sufficiently for 1/2 wave resonant behaviour to exist. If it does (and it doesn't take all that much), that's all that is needed.

See here if you want some of the basic physics: http://hyperphysics.phy-astr.gsu.edu...opecol.html#c2

Best
Scott

PS -if the terminus of a horn is choked via a port or similar, it's a mass loaded horn. If you're interested, a TQWT (which originally described a reverse taper horn that narrows toward the open terminus, i.e. the exact opposite of what is commonly called a TQWT these days) may also be regarded as a mass-loaded line.

[kristleifur]

Thank you for the excellent clarification, Scottmoose.

[bigcatdairy]

Originally posted by Scottmoose


Yes indeed. You see, within reason, a horn couldn't care less about the free air resonant frequency of the driver. All it needs to operate is pressure at the throat, and it will do the rest across it's operating BW (that's very heavily simplified, but as a basic principle it's true enough). Getting 2 or more octaves below Fs is a doddle if you can go large enough, or, if you can't, then using multiple drivers can compensate for whatever issues you might face due to an undersized box -harmonic nulls, high excursion etc.

You can use higher Q drivers in a horn -however, remember that you might find the HF start to vanish as the driver doesn't have sufficient motor-power to overcome the very high damping the horn places on it.

As for whether the BIB is a horn or not, it is. It's a tapped, chamberless conical corner-horn to be exact. As I mentioned above, if a cabinet expands toward the mouth, then it's a horn. Period. A cone, or any type of expanding 'tube' that is closed at one end & open at the other has the same fundamental resonant frequency and harmonic behaviour as a cyliner that is open at both ends. Resonance thus occurs at lambda / 2, unlike a straight cylinder closed at one end & open at the other, where resonance is at lambda / 4. A horn may therefore be categorised as a 1/2 wave resonator with a 1/4 wave fundamental. Some say that for something to be defined as a horn, it must match the impedance of the diaphram to the air at Fc. Strictly speaking, that's not really true. Impedance matching at Fc might be a design objective, but the true measure is if it expands sufficiently for 1/2 wave resonant behaviour to exist. If it does (and it doesn't take all that much), that's all that is needed.

See here if you want some of the basic physics: http://hyperphysics.phy-astr.gsu.edu...opecol.html#c2

Best
Scott

PS -if the terminus of a horn is choked via a port or similar, it's a mass loaded horn. If you're interested, a TQWT (which originally described a reverse taper horn that narrows toward the open terminus, i.e. the exact opposite of what is commonly called a TQWT these days) may also be regarded as a mass-loaded line.

tqwt might be a good choice, but i think it's not v suitable 4 me, bcoz i like low freq bass v much.and limited in fund, that's y i think blh is the best choice 4 this time.

[GM]

Originally posted by Scottmoose

2) By 'a driver' I'm assuming you mean an FR driver? Generally, a low Q unit (below 0.3) is preferable for horn loading.

Originally posted by bigcatdairy

now i have a pair of dls driver, within Qts 0.5x, fs 64 Hz, can i use this pair of driver to make a horn enclusure?

FWIW, for a BLH, IMO it's best to use an effective mass corner no higher than 250 - 400 Hz depending on the individual's hearing sensitivity to out of phase comb filtering that unfortunately can only be found through experimentation AFAIK, so erring on the low side seems the prudent choice without knowing.

Once you know the driver's effective Qes, then its upper mass corner can calculated using 2*Fs/Qes or ~213 Hz for this driver using an assumed 0.6 Qes and if driven by a typical super low output impedance SS amp and large enough wire to keep voltage drop to an equally low percentage. IOW, very good specs IMO for a BLH, though with a relatively high Q it will be fairly large.

If you drive it with a typical SET amp though, the effective Qes will be higher, therefore have an effectively lower mass corner which will make the horn larger, so starting with a higher mass corner driver is desirable.

As to how low it will go, Fs*Qes/2 defines its lower mass corner, but due to the nature of BLHs, if designed to load this low, then its usable BW is limited to its upper mass corner, so for wide BW use I recommend loading no lower than ~0.707*Fs or ~45 Hz in this example. If you make it long enough and corner load it though, then it will play much lower with its actual gain BW being determined by the room's loading. To do this right you need to know the room's gain curve, otherwise designing in too much gain and bleeding off any excess worked for me, though if your room is a simple rectangular one, then having the horn roll off ~2nd order below the room's calculated first axial mode will at least get you in the 'ballpark' or use 1st order if you want to probably have enough extra gain for more tuning flexibility.

There are a number of programs available to design BLHs and all that I'm aware of require some quality time be spent learning them, though Hornresp seems the easiest overall of the ones I've tried, but the most accurate results will come from Akabak due to its much greater input flexibility, ergo very steep learning curve to realize its potential.

GM

[just a guy]

...you need to know the room's gain curve...

I never had the ability to do any measurements, but now that I can measure I would like to measure the gain curves of all the rooms I am likely to ever use for audio to avoid potentially huge speaker/room mismatch situations.

What is the best way to measure a room's gain curve? The only thing I can think of is to measure a (preferably) sealed sub outside to gain a known reference, and then remeasure in room (preferably at several different locations in room) and then subtract the reference (outside measurement) from the in room measurement.

Am I close or is there an easier or better way to measure the room gain curve?

[GM]

http://purebits.com/appnote11.html#par1

[bigcatdairy]

thx guys, 1 more question: i found maybe it's easier to make a spiral horn instead of folded blh.
can any body who has corresponding experiences of both(spiral and folded blh) tell what's the difference of final results between those enclosures? assume that except boxes' enclosures, other conditions are the same.

[Scottmoose]

Depends on what you mean by a spiral horn. The angular spiral horns, with a couple of exceptions, have no expansion, so they cannot be regarded as horns -they're just long QW boxes with a large number of folds. The BR boxes with the spiral packed into the tube are still primarily BR -I suspect that the spiral simply has the effect of slightly increasing the vent length & lowering the tuning frequency for a given tube size.

All of which is to say, they won't sound much like a more regular type of BLH -they don't / won't have the efficiency, nor will they have the physical scale & impact the latter can provide.

[bigcatdairy]

Originally posted by Scottmoose

All of which is to say, they won't sound much like a more regular type of BLH -they don't / won't have the efficiency, nor will they have the physical scale & impact the latter can provide.

understood, mind of spiral horn is rejected.
thx guy~

[bigcatdairy]

Originally posted by Scottmoose


Yes indeed. You see, within reason, a horn couldn't care less about the free air resonant frequency of the driver. All it needs to operate is pressure at the throat, and it will do the rest across it's operating BW (that's very heavily simplified, but as a basic principle it's true enough). Getting 2 or more octaves below Fs is a doddle if you can go large enough, or, if you can't, then using multiple drivers can compensate for whatever issues you might face due to an undersized box -harmonic nulls, high excursion etc.

You can use higher Q drivers in a horn -however, remember that you might find the HF start to vanish as the driver doesn't have sufficient motor-power to overcome the very high damping the horn places on it.

As for whether the BIB is a horn or not, it is. It's a tapped, chamberless conical corner-horn to be exact. As I mentioned above, if a cabinet expands toward the mouth, then it's a horn. Period. A cone, or any type of expanding 'tube' that is closed at one end & open at the other has the same fundamental resonant frequency and harmonic behaviour as a cyliner that is open at both ends. Resonance thus occurs at lambda / 2, unlike a straight cylinder closed at one end & open at the other, where resonance is at lambda / 4. A horn may therefore be categorised as a 1/2 wave resonator with a 1/4 wave fundamental. Some say that for something to be defined as a horn, it must match the impedance of the diaphram to the air at Fc. Strictly speaking, that's not really true. Impedance matching at Fc might be a design objective, but the true measure is if it expands sufficiently for 1/2 wave resonant behaviour to exist. If it does (and it doesn't take all that much), that's all that is needed.

See here if you want some of the basic physics: http://hyperphysics.phy-astr.gsu.edu...opecol.html#c2

Best
Scott

PS -if the terminus of a horn is choked via a port or similar, it's a mass loaded horn. If you're interested, a TQWT (which originally described a reverse taper horn that narrows toward the open terminus, i.e. the exact opposite of what is commonly called a TQWT these days) may also be regarded as a mass-loaded line.

Originally posted by GM




FWIW, for a BLH, IMO it's best to use an effective mass corner no higher than 250 - 400 Hz depending on the individual's hearing sensitivity to out of phase comb filtering that unfortunately can only be found through experimentation AFAIK, so erring on the low side seems the prudent choice without knowing.

Once you know the driver's effective Qes, then its upper mass corner can calculated using 2*Fs/Qes or ~213 Hz for this driver using an assumed 0.6 Qes and if driven by a typical super low output impedance SS amp and large enough wire to keep voltage drop to an equally low percentage. IOW, very good specs IMO for a BLH, though with a relatively high Q it will be fairly large.

If you drive it with a typical SET amp though, the effective Qes will be higher, therefore have an effectively lower mass corner which will make the horn larger, so starting with a higher mass corner driver is desirable.

As to how low it will go, Fs*Qes/2 defines its lower mass corner, but due to the nature of BLHs, if designed to load this low, then its usable BW is limited to its upper mass corner, so for wide BW use I recommend loading no lower than ~0.707*Fs or ~45 Hz in this example. If you make it long enough and corner load it though, then it will play much lower with its actual gain BW being determined by the room's loading. To do this right you need to know the room's gain curve, otherwise designing in too much gain and bleeding off any excess worked for me, though if your room is a simple rectangular one, then having the horn roll off ~2nd order below the room's calculated first axial mode will at least get you in the 'ballpark' or use 1st order if you want to probably have enough extra gain for more tuning flexibility.

There are a number of programs available to design BLHs and all that I'm aware of require some quality time be spent learning them, though Hornresp seems the easiest overall of the ones I've tried, but the most accurate results will come from Akabak due to its much greater input flexibility, ergo very steep learning curve to realize its potential.

GM

what's mass corner?