I know i posted a first build type thread the other day (3way)
but i decided to start a bit simpler so im gonna make some 2way bookcase style speakers for a mate.
Im thinking seas 27TFFC tweeter and a P17RCY MidWoofer.
This will be in a 7.3L vented enclosure tuned to 66Hz with a 6.8cm vent 28cm long giving a vent mach of 0.04 (calculated in WinIsd Beta).
I was thinking of using a 2nd order LW crossing at 3KHz with a zobels network on the midwoofer.
I have attached and image of the xover and zobels network i designed for it and a SPL plot for the P17RCY from WinIsd.
If someone could have a look and check that i havent gone horribly wrong it would be very much appreciated.
Oh and baffle step effects - how much should i worry?
but i decided to start a bit simpler so im gonna make some 2way bookcase style speakers for a mate.
Im thinking seas 27TFFC tweeter and a P17RCY MidWoofer.
This will be in a 7.3L vented enclosure tuned to 66Hz with a 6.8cm vent 28cm long giving a vent mach of 0.04 (calculated in WinIsd Beta).
I was thinking of using a 2nd order LW crossing at 3KHz with a zobels network on the midwoofer.
I have attached and image of the xover and zobels network i designed for it and a SPL plot for the P17RCY from WinIsd.
If someone could have a look and check that i havent gone horribly wrong it would be very much appreciated.
Oh and baffle step effects - how much should i worry?
Attachments
Why? - I have ploted the different curves in WinIsd and 7.3 @ 66Hz remains flatter for ~100hz longer - admittedly the rate of roll off is steeper but the F3 point is 75.18hz compared to 91.24Hz for the same driver in a 12L enclosure tuned to 44Hz.
Can you explain why you recommend 12l / 45Hz? Im new to this and not sure what im missing here
Ive ploted the curves in winisd and attached them below
Green - 12L / 44Hz F3 @ 91.24hz
Red - 7.3l / 55Hz F3 @ 79.92Hz
Blue - 7.3L / 66hz F3 @ 75.18Hz
Can you explain why you recommend 12l / 45Hz? Im new to this and not sure what im missing here
Ive ploted the curves in winisd and attached them below
Green - 12L / 44Hz F3 @ 91.24hz
Red - 7.3l / 55Hz F3 @ 79.92Hz
Blue - 7.3L / 66hz F3 @ 75.18Hz
Attachments
Intent
Not sure of your intentions here, but what you have modeled has no bass. If you wish to pair this up with a subwoofer as a satellite, then the response is appropriate. Otherwise, it will be all midrange and highs, with no balance.
I think the other posters were suggesting some kind of alignment to extend the low end response.
Tim
Not sure of your intentions here, but what you have modeled has no bass. If you wish to pair this up with a subwoofer as a satellite, then the response is appropriate. Otherwise, it will be all midrange and highs, with no balance.
I think the other posters were suggesting some kind of alignment to extend the low end response.
Tim
Im trying to model a simple twoway full range speaker in a small enclosure. when you say it has no bass - at what point does the mid / midbass become bass / sub-bass?
The WinIsd plots above show only a 10 - 20Hz extention from my original plot (blue line) and the suggested 12L / 45Hz enclosure (green line) is an F3 75.18 really produce poor bass response?
The blue curve maintains a 92dB profile to a lower freq than the green
Sry still kinda new to all this - just trying to understand how to extend the bass repsonse while maintaining a relatively flat profile.
All the help is greatfully appreciated
The WinIsd plots above show only a 10 - 20Hz extention from my original plot (blue line) and the suggested 12L / 45Hz enclosure (green line) is an F3 75.18 really produce poor bass response?
The blue curve maintains a 92dB profile to a lower freq than the green
Sry still kinda new to all this - just trying to understand how to extend the bass repsonse while maintaining a relatively flat profile.
All the help is greatfully appreciated
Response
Couple of basics might help - highly simplified. Bass extends from 20 Hz up to aound 200 Hz. Most commercial speakers run to +- 3dB from 30Hz and below, for the large floor standers, to 60 or 70 Hz for the small bookshelf/mini-monitors, in terms of bass extension. Music can run to very low frequencies with a big pipe organ, like 16 Hz, but generally speaking, low E on the electric bass guitar is good enough, or, at or near 40 Hz. So to reproduce 95 % or more of all music, that should be your target.
The Thiele-Small parameters are basically an electrical means to measure what a woofer is capable of doing. For sealed enclosures, look for Qts values from .35 to .50. Since Qts is a rough reflection of damping, a sealed box generally requires more excursion, therefore less motor strength, and lower damping than a woofer used in a ported box.
Ported enclosures usually contain woofers with Qts values from mid .30s on down. When Qts drops into the .20s, the woofer is said to be highly damped, which works well for efficiency but not so well for excursion, where the motor strength is actually working against a reasonable freedom of movement.
For the short term, to get extension near 40 Hz, look for Qts around low .30s, Xmax in the 6mm or more range, Fs in the 30s Hz or below, and efficiency as high as you can get. Peerless has affordable woofers that should meet yor needs, also Vifa, but the Seas are really quite good. The metal cones offer more of a challenge to a beginning DIYer due to the resonances and break-up problems at higher frequencies that must be successfully dealt with in the crossover. See Siegfried Linkwitz's "Orion" dipole design.
One popular Seas design is the Thor MTM, which may give you some idea of the specs to look for, and the woofers are paper.
The box size will increase at a rate of 8 times for every octave you drop in bass extension while maintaining the same SPL(dB), so it will not be possible to achieve low frequency extension, low power use, and small box size simultaneously, Hoffman's Iron Law says, so pick two.
Most people cheat on the power end of it by simply giving it more gas, failing to realize the result of this is rising compression and distortion, but that is another day.
Speaker-building is a collection of compromises, but at least you get to pick those right for you.
Tim
Couple of basics might help - highly simplified. Bass extends from 20 Hz up to aound 200 Hz. Most commercial speakers run to +- 3dB from 30Hz and below, for the large floor standers, to 60 or 70 Hz for the small bookshelf/mini-monitors, in terms of bass extension. Music can run to very low frequencies with a big pipe organ, like 16 Hz, but generally speaking, low E on the electric bass guitar is good enough, or, at or near 40 Hz. So to reproduce 95 % or more of all music, that should be your target.
The Thiele-Small parameters are basically an electrical means to measure what a woofer is capable of doing. For sealed enclosures, look for Qts values from .35 to .50. Since Qts is a rough reflection of damping, a sealed box generally requires more excursion, therefore less motor strength, and lower damping than a woofer used in a ported box.
Ported enclosures usually contain woofers with Qts values from mid .30s on down. When Qts drops into the .20s, the woofer is said to be highly damped, which works well for efficiency but not so well for excursion, where the motor strength is actually working against a reasonable freedom of movement.
For the short term, to get extension near 40 Hz, look for Qts around low .30s, Xmax in the 6mm or more range, Fs in the 30s Hz or below, and efficiency as high as you can get. Peerless has affordable woofers that should meet yor needs, also Vifa, but the Seas are really quite good. The metal cones offer more of a challenge to a beginning DIYer due to the resonances and break-up problems at higher frequencies that must be successfully dealt with in the crossover. See Siegfried Linkwitz's "Orion" dipole design.
One popular Seas design is the Thor MTM, which may give you some idea of the specs to look for, and the woofers are paper.
The box size will increase at a rate of 8 times for every octave you drop in bass extension while maintaining the same SPL(dB), so it will not be possible to achieve low frequency extension, low power use, and small box size simultaneously, Hoffman's Iron Law says, so pick two.
Most people cheat on the power end of it by simply giving it more gas, failing to realize the result of this is rising compression and distortion, but that is another day.
Speaker-building is a collection of compromises, but at least you get to pick those right for you.
Tim
cheers for the pointers - ive been using the T-S parameters and WinIsd to calculated Spl and freq response but im still having great difficultly finding a driver.
As you said its a matter of compromise but i really cant go for an enclosure of more than 20L.
This restricts a number of drivers i would have other wise chosen - the Vifa c20WJ-19 for example which maintains the 91dB SPL and can extend bass response down to an F3 of 33.1Hz unfortuneately this require a cab or over 124L
Im having great difficulty in find a driver that retains the sensitivity while having a extended bass response.
Any driver suggestion? - I have modelled the majority of the ones i have been able to find readily availiable and it appear that most with a 90+spl and an f3 of below 40hz require a cab of 50L and upwards
As you said its a matter of compromise but i really cant go for an enclosure of more than 20L.
This restricts a number of drivers i would have other wise chosen - the Vifa c20WJ-19 for example which maintains the 91dB SPL and can extend bass response down to an F3 of 33.1Hz unfortuneately this require a cab or over 124L
Im having great difficulty in find a driver that retains the sensitivity while having a extended bass response.
Any driver suggestion? - I have modelled the majority of the ones i have been able to find readily availiable and it appear that most with a 90+spl and an f3 of below 40hz require a cab of 50L and upwards
Efficiency
Baronty,
Try the 850122 Peerless 7". The Qs are a little high, the efficiency pretty low, but that is the cost of the box size remaining fixed if we still want to attain somrthing close to 40 Hz.
See how it models in a 20 l ported enclosure tuned to 40 Hz.
Fs is 38 Hz, so not much more there. Handles power well though, and has 5mm xmax, so the numbers look OK.
It will work in either a sealed or ported enclosure. While you have not mentioned the dreaded sealed box, they do actuallt work well. Just not as efficient.
Tim
Edit: The Thor has magnesium woofers.
Baronty,
Try the 850122 Peerless 7". The Qs are a little high, the efficiency pretty low, but that is the cost of the box size remaining fixed if we still want to attain somrthing close to 40 Hz.
See how it models in a 20 l ported enclosure tuned to 40 Hz.
Fs is 38 Hz, so not much more there. Handles power well though, and has 5mm xmax, so the numbers look OK.
It will work in either a sealed or ported enclosure. While you have not mentioned the dreaded sealed box, they do actuallt work well. Just not as efficient.
Tim
Edit: The Thor has magnesium woofers.
Efficiency
Efficiency and low frequency extension are somewhat at odds with one another. That is why most of the subwoofers available are either low efficiency in the 85 dB/w/m range, or large in size to compensate. Bass production is really about sweeping as much air as possible. So, big cone, big excursion, low Fs will achieve a lower tuning frequency in a resonable box size at the expense of being power hungry.
Yes, you will probably need some sort of baffle step compensation unless the speaker is placed close to a rear wall where boundary reinforcement will boost the low end.
Also look at the Vifa PL18009-08 in the same ported 20 liter box tuned to 40 Hz. If you look at the vifa response plot, this unit has a peak at around 3K Hz - 4.5 K Hz before roll-off. If you crossover at the usual 2.5K or 2.7K Hz, this peak will probably still be audible unless you can smooth it with a notch filter. You'll have to experiment.
Some of the Audax units might work as well, but I haven't loaded any recently as they are drifting awqy from diy. Monacor has some really nice extended midbasses. I would certainly check them out.
This alignment requires quite a long vent. If necessary use PVC pipe and a 90 degree elbow to keep the vent from extending out of the box, or up against the front baffle. Don't forget to deduct the overall losses of the woofer and vent displacement from the interior volume when figuring the enclosure size (I'd guess about 5 liters).
There are an amazing number of two-ways shown on line. Perhaps a quick search would show you some of the obstacles others have had to overcome.
Tim
Efficiency and low frequency extension are somewhat at odds with one another. That is why most of the subwoofers available are either low efficiency in the 85 dB/w/m range, or large in size to compensate. Bass production is really about sweeping as much air as possible. So, big cone, big excursion, low Fs will achieve a lower tuning frequency in a resonable box size at the expense of being power hungry.
Yes, you will probably need some sort of baffle step compensation unless the speaker is placed close to a rear wall where boundary reinforcement will boost the low end.
Also look at the Vifa PL18009-08 in the same ported 20 liter box tuned to 40 Hz. If you look at the vifa response plot, this unit has a peak at around 3K Hz - 4.5 K Hz before roll-off. If you crossover at the usual 2.5K or 2.7K Hz, this peak will probably still be audible unless you can smooth it with a notch filter. You'll have to experiment.
Some of the Audax units might work as well, but I haven't loaded any recently as they are drifting awqy from diy. Monacor has some really nice extended midbasses. I would certainly check them out.
This alignment requires quite a long vent. If necessary use PVC pipe and a 90 degree elbow to keep the vent from extending out of the box, or up against the front baffle. Don't forget to deduct the overall losses of the woofer and vent displacement from the interior volume when figuring the enclosure size (I'd guess about 5 liters).
There are an amazing number of two-ways shown on line. Perhaps a quick search would show you some of the obstacles others have had to overcome.
Tim
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