Hey Greg,
First of you have a great room (asymmetrical is the best) and with a fully DSP/Eq active system you will be able to get great sound.
A few general guide lines I believe are very important:
(1) I never drive any driver beyond 50% of its X Max, preferably plus/minus 2mm to reach desired SPL for most of the time... Excluding the wild party nights! If you do need more Vd (volume displacement) use multiple drivers or a bigger driver.
(2) I sim all drivers at 25% below max AES power rating.
(3) I only use sealed or open baffle loading. Never ported/transmission line/back loaded horn a or any similar "time domain flawed bass boost" loading.
(4) I aim for a Qts between 0.5 and 0.7. I usually find drivers with low Qts /high VAS fit my design the best.
(5) I never use any driver with a rubber surround. The one exception was an 8 inch Seas Mag coned driver which was very expensive but sounded average.
(6) Thermal compression (thermal distortion) can be a serious issue... Best way to be sure you are not going to suffer from it (its hard to detect and measure with domestic DSP/mics/software) is to use drivers with large well ventilated voice coils and design to 80% power (point 2).
(7) My goals/design preferences/bias are for high efficiency, sealed, accurate low distortion/high dynamics.... So not too ambitious!
My two suggestions for 15 inch bass covering 30Hz to 400Hz are as follows:
Beyma 15lx60 V2 https://www.beyma.com/en/products/c/low-mid-frequency/115LX60V28/altavoz-15lx60v2-8-oh/ (147g Mms/21.1 Bl = 6.96)
Beyma https://www.beyma.com/en/products/c/low-mid-frequency/115P80FEN8/altavoz-15p80fe-n-8-oh/ (88g Mms /22.1 Bl = 3.98) https://www.beyma.com/en/products/c/low-mid-frequency/115P80FEN8/altavoz-15p80fe-n-8-oh/
I will attach sims in a mo.
Hope this helps
A.
First of you have a great room (asymmetrical is the best) and with a fully DSP/Eq active system you will be able to get great sound.
A few general guide lines I believe are very important:
(1) I never drive any driver beyond 50% of its X Max, preferably plus/minus 2mm to reach desired SPL for most of the time... Excluding the wild party nights! If you do need more Vd (volume displacement) use multiple drivers or a bigger driver.
(2) I sim all drivers at 25% below max AES power rating.
(3) I only use sealed or open baffle loading. Never ported/transmission line/back loaded horn a or any similar "time domain flawed bass boost" loading.
(4) I aim for a Qts between 0.5 and 0.7. I usually find drivers with low Qts /high VAS fit my design the best.
(5) I never use any driver with a rubber surround. The one exception was an 8 inch Seas Mag coned driver which was very expensive but sounded average.
(6) Thermal compression (thermal distortion) can be a serious issue... Best way to be sure you are not going to suffer from it (its hard to detect and measure with domestic DSP/mics/software) is to use drivers with large well ventilated voice coils and design to 80% power (point 2).
(7) My goals/design preferences/bias are for high efficiency, sealed, accurate low distortion/high dynamics.... So not too ambitious!
My two suggestions for 15 inch bass covering 30Hz to 400Hz are as follows:
Beyma 15lx60 V2 https://www.beyma.com/en/products/c/low-mid-frequency/115LX60V28/altavoz-15lx60v2-8-oh/ (147g Mms/21.1 Bl = 6.96)
Beyma https://www.beyma.com/en/products/c/low-mid-frequency/115P80FEN8/altavoz-15p80fe-n-8-oh/ (88g Mms /22.1 Bl = 3.98) https://www.beyma.com/en/products/c/low-mid-frequency/115P80FEN8/altavoz-15p80fe-n-8-oh/
I will attach sims in a mo.
Hope this helps
A.
The 115P80 sims are comparing it to a few other drivers I was looking at... The PD158 is the best above 80Hz but the 15P80 is better below 80Hz. Compare the driver efficiency... 5% for Beyma 115P80 Vs 1.68% for the Beyma 15LX60 V2.
Thanks for your reply...
I don't understand when you say:
(4) I aim for a Qts between 0.5 and 0.7. I usually find drivers with low Qts /high VAS fit my design the best.
But what I understand is that drivers with low QTS climb well but don't go low naturally and vice versa...
I think I should get something in the middle of that...
I don't know if you know BMS 15s330, seems well designed...
15pr400 also is right in the middle, 3% hehe
I don't understand when you say:
(4) I aim for a Qts between 0.5 and 0.7. I usually find drivers with low Qts /high VAS fit my design the best.
But what I understand is that drivers with low QTS climb well but don't go low naturally and vice versa...
I think I should get something in the middle of that...
I don't know if you know BMS 15s330, seems well designed...
15pr400 also is right in the middle, 3% hehe
Sounds more like Alex was referring to Qtc, not Qts with that target range of 0.5-0.7.
That's the total system Q in a sealed box, taking account of the effect of box size on the shape of the LF rolloff, not just the drivers Q at resonance.
HTH,
D.
That's the total system Q in a sealed box, taking account of the effect of box size on the shape of the LF rolloff, not just the drivers Q at resonance.
HTH,
D.
Faital/BMS/18Sound/RCF/Precision Devices etc... All great brands and I'm sure there are lots of other great Pro 15 inch drivers and to be honest I think it is hard to tell the difference between the top 10 / well matched drivers once your total system is up and running. I haven't used any BMS drivers (but they have a great 5 inch mid I would love to try!) and Precision Devices are about as good as it gets in the Pro world.
You wont go far wrong with any of these brands in a sealed box, DSP/Eq'd/ active system.... Low ish Qts/low Mms/high Bl for best mids and slightly higher Qts for more extended bass and keep the whole (Qtc !) system between 0.5 and 0.7 and try to match the 50% X max limit with the 80% power limit if poss.... Good luck!
Cheers
A.
Of course I am stupid...
That said if you have a target of an f3 with correction, of the speaker is too medium like with high bl/MMS, it will need more correction and more distortion...
This is why I was reluctant to pick a low medium with 100db/w and 5% efficiency.
Something intermediate would be less risky...
I like faital 15fh530 : ferrite, 0.35qts, demodulation ring, triple roll,
18s 15lw2400, but doesn't this start to be oversized for home use !?
BMS 15s330, supposed to be very good on a distortion point, double roll ? Ferrite, demodulation, QTS 0.32...
Edit, what is strange is that 15fh510 with stronger magnet has an m roll suspension like the BMS...
Cms is the force exerted by the mechanical suspension of the speaker. It is simply a measurement of its stiffness. Considering stiffness (Cms), in conjunction with the Q parameters gives rise to the kind of subjective decisions made by car manufacturers when tuning cars between comfort to carry the president and precision to go racing. Think of the peaks and valleys of audio signals like a road surface then consider that the ideal speaker suspension is like car suspension that can traverse the rockiest terrain with race-car precision and sensitivity at the speed of a fighter plane. It’s quite a challenge because focusing on any one discipline tends to have a detrimental effect on the others.
18s 15lw2400, but doesn't this start to be oversized for home use !?
BMS 15s330, supposed to be very good on a distortion point, double roll ? Ferrite, demodulation, QTS 0.32...
Edit, what is strange is that 15fh510 with stronger magnet has an m roll suspension like the BMS...
Cms is the force exerted by the mechanical suspension of the speaker. It is simply a measurement of its stiffness. Considering stiffness (Cms), in conjunction with the Q parameters gives rise to the kind of subjective decisions made by car manufacturers when tuning cars between comfort to carry the president and precision to go racing. Think of the peaks and valleys of audio signals like a road surface then consider that the ideal speaker suspension is like car suspension that can traverse the rockiest terrain with race-car precision and sensitivity at the speed of a fighter plane. It’s quite a challenge because focusing on any one discipline tends to have a detrimental effect on the others.
Last edited:
I opened my test box, volume for the beyma 12b100r is between 50 and 60l.
I put a layer of 6cm rockwool bent in the middle and closed...
But what I realized is that if you don't put a high slope you have quite a lot of harmonics which go through the low section...even if set at 300hz.
I think I tend to prefer with steep crossovers designs...
I put a layer of 6cm rockwool bent in the middle and closed...
But what I realized is that if you don't put a high slope you have quite a lot of harmonics which go through the low section...even if set at 300hz.
I think I tend to prefer with steep crossovers designs...
I mean 300hz 48db/oct
Edit : I think I was so happy about trying that LT transform that the tonal balance was not right and the low section being 3db louder creating weired stuff
Edit : I think I was so happy about trying that LT transform that the tonal balance was not right and the low section being 3db louder creating weired stuff
Last edited:
"I like faital 15fh530 : ferrite, 0.35qts...."
But that is the datasheet, has someone measured it in real life after some breaking in ? How vain to simulate if your datas are not acurrate. vas can vary. Well you always can make a bigger box then full it of solid brick to reduce the volume if needed...
But that is the datasheet, has someone measured it in real life after some breaking in ? How vain to simulate if your datas are not acurrate. vas can vary. Well you always can make a bigger box then full it of solid brick to reduce the volume if needed...
Hey Greg,
Re your question about cabinet shape/resonance, I think its very important to minimise cabinet resonance, here are a few thoughts:
(1) Asymmetry is great, symmetry is bad. ie the worst cabinet shape is a cube and a trapezoid or curved shape is best.
(2) Use birch ply, not MDF!
(3) Dont build a "box"! Build up a laminated / layered cabinet for a true inert non resonant structure. (See attached pics)
(4) Calculate internal volume required, plus the air volume the driver takes up then add 10% to 20%. This allows you to apply internal cabinet damping material and/or internal stuffing. ("Twaron" or Angel Hair is very good).
(5) Also use up the extra air volume by gluing in place some acoustic foam wedges inside your cabinet ie turn the internal air space into a mini anechoic chamber.
(6) Numbers (4) and (5) are very important in the mid and high frequencies, less so in the bass. The bass cabinet requires mass and rigidity.
(7) Ratio of cone weight to cabinet weight is important ie If your 15 inch cone weighs 100g and its being powered by 500 watts its "pumping" in and out at 20 to approx 150 times a second.... If you calculate the stop/start energy and remember "for every action there is an equal and opposite reaction..." All that energy will rock a light cabinet back and forward and the panels will radiate more sound than the cone! My ref is the bass cabinet needs to weigh at least 400 times the Mms of the cone ie a 15 inch /100g cone needs a solid cabinet of at least 40Kg avoid the worst of the resonance issues.
(8) Really strong spikes are needed to anchor the bass cabinet to the floor. Then use "Sorbothane" pads (not more spikes!) to mount the mids and treble cabinets on top.
Cheers
A.
Re your question about cabinet shape/resonance, I think its very important to minimise cabinet resonance, here are a few thoughts:
(1) Asymmetry is great, symmetry is bad. ie the worst cabinet shape is a cube and a trapezoid or curved shape is best.
(2) Use birch ply, not MDF!
(3) Dont build a "box"! Build up a laminated / layered cabinet for a true inert non resonant structure. (See attached pics)
(4) Calculate internal volume required, plus the air volume the driver takes up then add 10% to 20%. This allows you to apply internal cabinet damping material and/or internal stuffing. ("Twaron" or Angel Hair is very good).
(5) Also use up the extra air volume by gluing in place some acoustic foam wedges inside your cabinet ie turn the internal air space into a mini anechoic chamber.
(6) Numbers (4) and (5) are very important in the mid and high frequencies, less so in the bass. The bass cabinet requires mass and rigidity.
(7) Ratio of cone weight to cabinet weight is important ie If your 15 inch cone weighs 100g and its being powered by 500 watts its "pumping" in and out at 20 to approx 150 times a second.... If you calculate the stop/start energy and remember "for every action there is an equal and opposite reaction..." All that energy will rock a light cabinet back and forward and the panels will radiate more sound than the cone! My ref is the bass cabinet needs to weigh at least 400 times the Mms of the cone ie a 15 inch /100g cone needs a solid cabinet of at least 40Kg avoid the worst of the resonance issues.
(8) Really strong spikes are needed to anchor the bass cabinet to the floor. Then use "Sorbothane" pads (not more spikes!) to mount the mids and treble cabinets on top.
Cheers
A.
Attachments
Hello,
Thanks, waiting for your answer I was getting some information...
As space is not an issue here and regarding the fact that sealed enclosure require less volume, what i will do :
Bigger rectangular box.
Inside double walls, not parallel of course, filled with sand. Or ceramic tiles, of debrees from all the stuff used for the house...
Brace behind the speaker with Dacron, polyester thin cloth stitched to it.
Fill behind with rockwool or melamine foam (expensive). Or acoustic foam wedges as you describe to create an anechoic chamber...
OSB could be a cheaper alternative to plywood which is insanely expensive here...?
3/ didn't understand, or what I understand is a lot of loss, expensive lol
4/ I read opposite as filling the box will artificially increase the volume. Also that smaller boxes have resonances which tend to go beyond bandwidth usage...
Thanks, waiting for your answer I was getting some information...
As space is not an issue here and regarding the fact that sealed enclosure require less volume, what i will do :
Bigger rectangular box.
Inside double walls, not parallel of course, filled with sand. Or ceramic tiles, of debrees from all the stuff used for the house...
Brace behind the speaker with Dacron, polyester thin cloth stitched to it.
Fill behind with rockwool or melamine foam (expensive). Or acoustic foam wedges as you describe to create an anechoic chamber...
OSB could be a cheaper alternative to plywood which is insanely expensive here...?
3/ didn't understand, or what I understand is a lot of loss, expensive lol
4/ I read opposite as filling the box will artificially increase the volume. Also that smaller boxes have resonances which tend to go beyond bandwidth usage...
Placed an order for the speakers 400€ /pair delivered.
I have lab gruppen lab 500 2*180w@8 ohms don't know if I should upgrade... I hardly get it to -15db led indicator
I have lab gruppen lab 500 2*180w@8 ohms don't know if I should upgrade... I hardly get it to -15db led indicator
#7 For a 100:1 mass ratio, the amplitude should also be 100:1, making the cone 40dB louder assuming the same effective surface area and radiation pattern. The box will also move as a dipole, partially cancelling itself out. And it's diminishing returns where you have to double the mass just to get a 6dB return. My mind is set on taking a risk with a light-weight box for my next build, but also taking counter measures like a castor wheel setup to minimise transfer of vibrations, and remembering to centre the woofer to prevent rotation.