When a naive diy begginer, such as myself, attempts to design a first system, the options seem endless - so many drivers, so little time.... But then constraints begin to take place, and the options quickly dissapear. Two such constrains, seem to be especially tough together. If you want an all-sealed design, with Qb between .5 and .7, and at the same time one that can reproduce respectable SPL, and at the same time must be driven by a half dozen alephs, non of which are to exceed a specific size to reduce heat dissipation..... I thought these were reasonable parameters, untill I began modeling the system for power requirements using Mr. Linkwitz's formular (or rather formulas found on his site...). The vast majority of high quality drivers, when placed in a sealed box of the above mentioned Qb, require MASSIVE ammounts of power to be driven to decen SPL. In some cases, multiples of drivers must be used, also encreasing power requirements.... What to do......
I keep coming back to the same solution, which seems to be the most reasonable, although very expensive. This solution will have one large driver reproducing the midbass, from maybe 60 Hz to 800 Hz, and probably 1 Khz if we factor in after-XO responce. What bothers me, however, is that this driver has an exceleration factor of 175, and I need some reasurance that this is ok, even all the way up to 1 Khz, before I commit to this expensive solution. So if anyone has comments, I would love to hear them. Thanks!
I keep coming back to the same solution, which seems to be the most reasonable, although very expensive. This solution will have one large driver reproducing the midbass, from maybe 60 Hz to 800 Hz, and probably 1 Khz if we factor in after-XO responce. What bothers me, however, is that this driver has an exceleration factor of 175, and I need some reasurance that this is ok, even all the way up to 1 Khz, before I commit to this expensive solution. So if anyone has comments, I would love to hear them. Thanks!
Peak Current = Force x Bl... Does this mean that acceleration factor (being Bl/Mms) has little to do with the "sound", and -ONLY-SPL is effected by quantety of current available? In other words, low Bl and high Mms are ok, as long as you have enough power to drive the speaker????? Is my logic correct?
This is one of those things where figures and measurements don't tell the whole story...
Yes, a high acceleration factor is a good thing, but it needs to be coupled with a lack of cone breakup, colouration, and many other factors besides, as with all these things, a driver can measure really well, but have a sound that usually tends towards the sterile. There is no substitute for listening, or if that is impossible, using others opinions. However, as with all web based stuff, you also need to filter responses and opinions...
Yes, a high acceleration factor is a good thing, but it needs to be coupled with a lack of cone breakup, colouration, and many other factors besides, as with all these things, a driver can measure really well, but have a sound that usually tends towards the sterile. There is no substitute for listening, or if that is impossible, using others opinions. However, as with all web based stuff, you also need to filter responses and opinions...
pinkmouse said:This is one of those things where figures and measurements don't tell the whole story...
Yes, a high acceleration factor is a good thing, but it needs to be coupled with a lack of cone breakup, colouration, and many other factors besides, as with all these things, a driver can measure really well, but have a sound that usually tends towards the sterile. There is no substitute for listening, or if that is impossible, using others opinions. However, as with all web based stuff, you also need to filter responses and opinions...
Agreed on all accounts. However, i have been relying on people's openions for far too long, and these also tell 50% of the story. So finally I decided to go for the second half, and crunch some numbers. I can tall you that it has been an eye opening experience.
RobWells said:
The Alephs are still in the "awaiting PCBs" stage, I am afraid.... But, four of them will be 30 watts each (6 channels by the way, not 12). These 4 x 30 will drive a pair of tweeters (94 dB efficiency), and a pair of dome midranges (also 94 dB). I have decided to use a dome midrange for several reasons. First, construction is much simpler, and there is no "box interaction", aside from half space radiation.... The other reason is efficiency. I think 30 watts will push these drivers hard enouph, especially if the baffle step is factored in.
The remaining 2 channels are up in the air, untill I can establish power requirements exactly. The driver is 97 dB efficient, but I am not too sure how it will combine with the other two. I know for sure that for now the woofers will be pushed by a pair of P3A amps, as I can not in any way deal with that much heat. I hope that in a year or so, when I get a new place, I will be able to move the woofers to a pair of Alephs, and use the P3As for a pair of sealed subs (45 Hz and lower?)
I have analyzed several drivers for bass duty, that will not take much power, and still deliver UP TO, 110 dB peak. I am not sure I need so much SPL, but its always good to have a little extra.
Nielsio said:
High efficiency is exactly what I am trying to get, but it appears to be hard to achieve in a sealed box...
I guess what I am trying to understand, is if the Acceleration Factor is just another measure of efficiency, where more power solves any inedequecy (sp?), or does it add to the sound (other things equal) reguardless of power levels.
Perhaps the sealed box decision is key. It became clear back in the hey-day of accoustic suspension (predecessors to the sealed box such as AR, Advent and KLH) the the only way to get the best out such loudspeakers was watts, wattts and more watts. Just as biologigical organisms in nature co-evolve, perhaps wthout AR and it's ilk, there never would have been Phase Linear and it's sucessors. In any case, I think that if one of the parameters is a seal box, there isn't going to be any way juggle other parameters so as to avoid the need for substantial amplification.
sam9 said:
I think you are right. Based on my simulations, which are based on Linkwitz's examples, and a little on WINisd, it appears that the woofers will need right around 200 watts each, and the subs, perhaps half of that. Thats a total of 600 watts of power for sub and mid bass, and of course another 1.5 kilowatt for the room
. The four channels of 30 watts seem like a drop in the bucket compared to that. So I will have to live with class AB for bass untill I can construct some type of heat management system....
I'm very interested in what 94 dB tweeters and dome mids you are using. Many people seem to prefer cone mids, except for the ATC mid domes which are quite pricey. But units that efficient are rare I thought.
It's true- a large mid cone is flexing and bending all over the place, so I think the center part of it can easily accelerate faster than the figures that use the entire mass of the cone would indicate. Sound scary but it works out fine if the drivers are made for this (in fact some sound spectacular!)
15" PA type sound reinforement speakers in huge sealed boxes seemed to model OK r.e. efficiency for me... what are you considering? A lot of peopple try for really low bass which pushes up the power requirement. If you stay above 40 hz things work out better. And still sound Great! You can always add a sub with
a more efficient amp than the alephs- bass apparently isn't their strong point sound wise anyway.
Mark
It's true- a large mid cone is flexing and bending all over the place, so I think the center part of it can easily accelerate faster than the figures that use the entire mass of the cone would indicate. Sound scary but it works out fine if the drivers are made for this (in fact some sound spectacular!)
15" PA type sound reinforement speakers in huge sealed boxes seemed to model OK r.e. efficiency for me... what are you considering? A lot of peopple try for really low bass which pushes up the power requirement. If you stay above 40 hz things work out better. And still sound Great! You can always add a sub with
a more efficient amp than the alephs- bass apparently isn't their strong point sound wise anyway.
Mark
Variac said:
SS Ring Radiators for tweets;
ATC "S" mid domes;
TAD 1601c in 75 liters sealed.
I did not want to use such expensive drivers, but for one reason or another, I came back to these 3 again and agian. I really like the fact that the tweeter and mid will not need a complex enclosure, which will alow me to concentrate on the baffle and the looks instead of trying to create a small cavity for a cone. These two are so close in sensitivity, and thus in power requirements, that I just can not resist. The project will take somewhat longer due to high cost, but what the hell, I already waited for so long. As far as the woofer (for which the price has so unseremoniously just gone up to $1,100), the only possibly better alternative that I can see, is the 1602, but I HATE the idea of paying so much for a foam sorround. So there it is, over 2k USD per side
Audiophilia is worse then cocaine addiction
I have also been pricing wood, which is apperantly going to be expensive as hell. I would like to do what the TAD guys have done for the Model 1, complete with "one piece" internal crossbracing, and extra thick baffle and sides. It is a good thing I am not married, so I HAVE to get this project in before I am
I agree- it is better to use very good drivers- it helps amortize the millions of hours you will spend on this. Why waste the time on less than the best?
Here is a guy that has some good insights I think , and has built speakers with the same or similar drivers as you are considering.
http://www.kingston.neostrada.pl/speakerbuilding.html
I had no idea the SS tweet is so efficient. Are they rated at
1 watt/1 meter or at 2.83 volts or some such?
there is a difference!! check to be sure the tweet and mid are using the same standard.
Try a bigger box with a Q of around .6
The pre marriage accumalation concept shows that you are a very clever fellow. Get a junker motorcycle too, and keep it in your garage so its established that you have rights to one.
Here is a guy that has some good insights I think , and has built speakers with the same or similar drivers as you are considering.
http://www.kingston.neostrada.pl/speakerbuilding.html
I had no idea the SS tweet is so efficient. Are they rated at
1 watt/1 meter or at 2.83 volts or some such?
there is a difference!! check to be sure the tweet and mid are using the same standard.
Try a bigger box with a Q of around .6
The pre marriage accumalation concept shows that you are a very clever fellow. Get a junker motorcycle too, and keep it in your garage so its established that you have rights to one.
amo said:
SS Ring Radiators for tweets;
ATC "S" mid domes;
TAD 1601c in 75 liters sealed.
I did not want to use such expensive drivers, but for one reason or another, I came back to these 3 again and agian. I really like the fact that the tweeter and mid will not need a complex enclosure, which will alow me to concentrate on the baffle and the looks instead of trying to create a small cavity for a cone. These two are so close in sensitivity, and thus in power requirements, that I just can not resist. The project will take somewhat longer due to high cost, but what the hell, I already waited for so long. As far as the woofer (for which the price has so unseremoniously just gone up to $1,100), the only possibly better alternative that I can see, is the 1602, but I HATE the idea of paying so much for a foam sorround. So there it is, over 2k USD per side
Audiophilia is worse then cocaine addiction
I have also been pricing wood, which is apperantly going to be expensive as hell. I would like to do what the TAD guys have done for the Model 1, complete with "one piece" internal crossbracing, and extra thick baffle and sides. It is a good thing I am not married, so I HAVE to get this project in before I am
Woo that is expensive. I was about to suggest doubling up the woofers, which should give you an extra 3-6Db.(thus halving/quartering you power requirements.) I use 2 10" per side and these give a sensitivity of 94Db per side. Plenty loud enough for music(using 60w per driver). Still needs sub for AV though..
Good luck anyway..
Rob
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