Hi everyone,
I would like to start a new journey in DIY with speaker building, and I'm sure that your help will be fundamental in doing the project right 🙂
The approach will be a little unconventional, starting with horn speakers covering specific frequency ranges instead of building a "complete" system.
The reason for this is that I'm planning to use the speakers in multichannel sound performances, each speaker couple will have its discreet stereo source and amplifier (and hi-pass filter from the audio source), along with a quadraphonic PA, so for the moment I will not use the speakers combined with a woofer via crossover, but later could be used in a "standard" 3-way configuration.
I would like to build 4 speakers, two for upper midrange and two for high frequencies. For the upper midrange I thought of Smith horns because everything has to fit in my suitcase (40x60cm) with the rest of my equipment.
About the Smith horns:
1 - I've seen the design built in different dimensions, I would like to stick with the original design, but I can consider improvements (like JBL 2397 style) or changing dimensions;
2 - JBL 2397 and some DIY projects I've seen have a flare at the opening, is it supposed to be somehow helpful for vertical distribution of sound?
3 - which compression driver would you recommend?
4 - any advice on a good simple design for the higher frequencies?
I’m not that good at working with wood and probably I will go for laser cut plywood for the project.
Thanks a lot to everyone in advance, looking forward to hear your thoughts!
glauco
I would like to start a new journey in DIY with speaker building, and I'm sure that your help will be fundamental in doing the project right 🙂
The approach will be a little unconventional, starting with horn speakers covering specific frequency ranges instead of building a "complete" system.
The reason for this is that I'm planning to use the speakers in multichannel sound performances, each speaker couple will have its discreet stereo source and amplifier (and hi-pass filter from the audio source), along with a quadraphonic PA, so for the moment I will not use the speakers combined with a woofer via crossover, but later could be used in a "standard" 3-way configuration.
I would like to build 4 speakers, two for upper midrange and two for high frequencies. For the upper midrange I thought of Smith horns because everything has to fit in my suitcase (40x60cm) with the rest of my equipment.
About the Smith horns:
1 - I've seen the design built in different dimensions, I would like to stick with the original design, but I can consider improvements (like JBL 2397 style) or changing dimensions;
2 - JBL 2397 and some DIY projects I've seen have a flare at the opening, is it supposed to be somehow helpful for vertical distribution of sound?
3 - which compression driver would you recommend?
4 - any advice on a good simple design for the higher frequencies?
I’m not that good at working with wood and probably I will go for laser cut plywood for the project.
Thanks a lot to everyone in advance, looking forward to hear your thoughts!
glauco
The low frequency cutoff (Fc) is determined by the exponential horn length. Generally you want to cross about an octave above Fc.
The Smith horn exit works by diffraction, the more narrow it is, the wider the vertical dispersion.
The flare improves the smoothness of frequency response, and low frequency loading to some extent.
Depends on how low and loud you want it to go. With 4" diaphragm drivers, ~400Hz is as low as practical for ~340mm horn depth and concert levels.
1.5" to 2" diaphragm compression drivers could cover smaller areas at reduced levels.
The Smith horn can go as high as the driver used supports- even with a 4" diaphragm 400-16kHz is no problem.
Using coax compression drivers like the B&C DCX series would improve both low and high frequency.
Art
Thanks @Arez and @weltersys for replying!
I'd like to apply the hi-pass filter the midrange smith horn ideally at around 700-800Hz as per the original design, but I can also raise the frequency up to 1kHz if there is a better choice of reasonably priced drivers. I had a look at B&C drivers but most of them are out of my price range, a couple that I can afford are:
DE52 - frequency range 1-17kHz recommended crossover 1kHz
DE82TN - frequency range 0.5-18kHz recommended crossover 1kHz
DH450 - frequency range 1-18kHz recommended crossover 1kHz (also a lot lighter in weight than the others, which can be good since I will travel with them)
or a JBL Selenium D250X - frequency range 0.4-9kHz
Do you think some of them will work? Or maybe you know some better options in that price range (below 250€ for the single driver, better if around 100€)?
I don't need them to play that loud, I used for years some half broken speakers (without any cabinet or horn) powered by a Muse M-20 t-amp (ta2020 IIRC) and they were loud enough in every place I've been. I would like to use the same amps for the new speakers.
Thanks a lot for the help!
Glauco
I'd like to apply the hi-pass filter the midrange smith horn ideally at around 700-800Hz as per the original design, but I can also raise the frequency up to 1kHz if there is a better choice of reasonably priced drivers. I had a look at B&C drivers but most of them are out of my price range, a couple that I can afford are:
DE52 - frequency range 1-17kHz recommended crossover 1kHz
DE82TN - frequency range 0.5-18kHz recommended crossover 1kHz
DH450 - frequency range 1-18kHz recommended crossover 1kHz (also a lot lighter in weight than the others, which can be good since I will travel with them)
or a JBL Selenium D250X - frequency range 0.4-9kHz
Do you think some of them will work? Or maybe you know some better options in that price range (below 250€ for the single driver, better if around 100€)?
I don't need them to play that loud, I used for years some half broken speakers (without any cabinet or horn) powered by a Muse M-20 t-amp (ta2020 IIRC) and they were loud enough in every place I've been. I would like to use the same amps for the new speakers.
Thanks a lot for the help!
Glauco
Glauco,
The D250X would require a tweeter, it's response drops like a rock after 7kHz. Also uses a thread on mount, more difficult to fabricate, or an added adapter expense.
Smith's original design was for 1" exit drivers, you have included 1.4" exit drivers also, which would require a 1.4" height horn, increasing size and weight.
The driver's diaphragm size directly translates to how much low end they can produce before the diaphragm hits the phase plug (about 0.5mm excursion), the 3" capable of around 6dB more than the 2", the 2" ~6dB more than the 1.4".
That 12 dB variance means the DE82 could go around an octave lower, or play over twice as loud as the DH450.
That said, with your low power, even the smallest of those drivers won't have any excursion problem at 700 Hz, your amp will clip and sound terrible before the driver will sound overly distressed.
The DH450 is an interesting new design, the size, weight & cost certainly attractive.
It is also one of the few HF drivers available in 4ohms, which would be an advantage with your amp, ~11 watts rather than 7 watts at 8ohms, around 2.5 dB more "clean" power.
Art
The D250X would require a tweeter, it's response drops like a rock after 7kHz. Also uses a thread on mount, more difficult to fabricate, or an added adapter expense.
Smith's original design was for 1" exit drivers, you have included 1.4" exit drivers also, which would require a 1.4" height horn, increasing size and weight.
The driver's diaphragm size directly translates to how much low end they can produce before the diaphragm hits the phase plug (about 0.5mm excursion), the 3" capable of around 6dB more than the 2", the 2" ~6dB more than the 1.4".
That 12 dB variance means the DE82 could go around an octave lower, or play over twice as loud as the DH450.
That said, with your low power, even the smallest of those drivers won't have any excursion problem at 700 Hz, your amp will clip and sound terrible before the driver will sound overly distressed.
The DH450 is an interesting new design, the size, weight & cost certainly attractive.
It is also one of the few HF drivers available in 4ohms, which would be an advantage with your amp, ~11 watts rather than 7 watts at 8ohms, around 2.5 dB more "clean" power.
Art
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Thanks a lot Art for the information, It's my first speaker project and everything you say is incredibly precious <3
One question about the height of the horn: if I go for a 1.4" driver and accordingly change the horn height, do I have to change width and length to respect the ratio of the design?
I can consider to buy a new amp with more power output if necessary, I can try different portable amps when the project is done.
The DH450 could be a good solution anyways, at least if it's a mistake it will not be that expensive 🙂 but having more power and manage to go down to 700Hz as initially planned can be worth the extra expense/weight of the DE82.
Thanks again!
Glauco
One question about the height of the horn: if I go for a 1.4" driver and accordingly change the horn height, do I have to change width and length to respect the ratio of the design?
I can consider to buy a new amp with more power output if necessary, I can try different portable amps when the project is done.
The DH450 could be a good solution anyways, at least if it's a mistake it will not be that expensive 🙂 but having more power and manage to go down to 700Hz as initially planned can be worth the extra expense/weight of the DE82.
Thanks again!
Glauco
No, since the taper rate would remain the same, Fc should remain ~375 Hz, assuming you use Bob Smith's DSH dimensions from the January 1951 Audio engineering article.
https://www.worldradiohistory.com/Archive-All-Audio/Archive-Audio/50s/Audio-1951-Jan.pdf
With a steep (24dB/octave) crossover, the 1951 DSH with a DE82TN could cross as low as 450Hz at the levels you are used to.
Art