| smithsonga |
Hi Guys
I have been tinkering with some designs with WINISD using the Lambda SB15. I have configured a system with 2 SB15s, sealed that is flat to 30Hz with a drop of 7 dB at 20Hz.
How much gain can I anticipate in the room? How much would the response pick up at 20Hz?
I love the sound of sealed systems and with all my playing around with different drivers and box sizes, this combo seems to work well as the group delay peaks at 10ms at 25Hz...lower than that everywhere else. The program is predicting sensitivity of 94dB also...which is nice and high.
What am I missing? Limits to max SPL? Distortion issues? Power Hungry? what?
Lastly, what is good source for 250-350W sub amps? I plan on using electronics for crossover.
Thanks!
Jim |
|
|
| kelticwizard |
| quote: | Originally posted by smithsonga:
What am I missing? Limits to max SPL? Distortion issues? Power Hungry? what?
|
Here is the answer, or an approximate guideline, to one of your questions anyway. Look up the displacement volume of the Strykes, and look at the corresponding place on the chart. Room gain goes on top of this.
PS: For 15 inchers, the approximate cone area is 132 inČ. Multiply that by your one-way excursion, and you have the displacement volume of the Stryke.
http://www.diyaudio.com/forums/show...light=chart+SPL |
|
|
| tcpip |
You could try the high power designs by Randy Slone. You can buy his High Power Audio Amplifier Construction Manual and try building some of his designs. He used to sell PCBs of his amps, and even finished kits, on his Website, www.sealelectronics.com. But he appears to have decided to close down this business.
He still writes and answers email from readers, though. I can vouch for the fact that he has infinite patience, going by the number of stupid technical questions he has patiently answered for me. :)
His books include 400W amps (that's 400W/channel if you build a stereo amp), driven by L-MOSFET output stages. And performance for sub-woofers should be absolutely fine, because good transistor amps, even if they exhibit distortion, do so at high frequencies, which become irrelevant for subwoofer apps. In fact, Randy Slone's high power amps are good enough to be used for full-range applications, giving you 0.5% THD at those power levels.
Tarun |
|
|
| kelticwizard |
Here is a link to a chart of Room Gain. This is an approximation-other charts will differ slightly.
It's all guesswork because of the room and it's modes anyway, but at least you can get an idea.
http://www.speakerbuilding.com/content/1020/rge.gif |
|
|
| kelticwizard |
| quote: | Originally posted by smithsonga:
Lastly, what is good source for 250-350W sub amps? I plan on using electronics for crossover. |
Here is a page with sub amps at pretty decent prices. Those power ratings are into 4 ohm speakers-they only put out half their power into 8 ohm speakers. Parts Express had other subwoofer amps, some with remote control, for similar prices. so does Madisound at www.madisound.com
http://www.partsexpress.com/pe/show...t_ID=9388&DID=7
Here is a somewhat more expensive 500 watt, (8 ohms), sub amp. It gives 720 watts into 4 ohms:
http://www.adireaudio.com/diy_audio...fiers/hs500.htm |
|
|
| navin |
funny i notice that drivers with big Xmax have low sensitivity. that means you are using a lot of power to produce high SPLs.
Ex: Driver with Xmax 27mm sens is 84db, Driver with Xmax 13mm Sens is 89db and Driver with Xmax 9mm Sens is 92db (all these 3 are well known 12" drivers).
What you should actually look at is what is max SPL the driver can produce. All things remaining equal, if a driver can produce 100db at 50hz using only 50W it is better than a driver that can produce 100db at 50Hz using 200W.
the driver that has a sens of 84db will need to thermally handle 100W to get to 104db but the driver that has a sens of 92db need only handle 10W to get to 102db. Again these are thermal handling capacities and are not directly realted to physical Xmax limitations but it vaguely illustrates what I am trying to say.
Does this make sense? |
|
|
| Brett D. |
My opinion is that amplifier power is cheap for sub purposes it's
not like you need a Pass Labs X series to run a sub so I don't
generaly give much thought to the sensitivity of a sub woofer.
Rythmik audio makes a high power plate amp (350W RMS If I am
not mistaken) that would work well with the Lam or the Stryke
HE or AV series. I think the web site is http://www.rythmikaudio.com/ I
have no personal experiance with this company but John Janowitz
is working with Brian from Rhythmic and plans to carry the 350W
plate amp in the not so distant future.
Or the Parts Express 250W Plate Amp or you could always run
a Pro amp like something from Crown or QSC.
As far as X-Max, X-Sus and X-Mag is concerned. The drivers with
the smaller values are most likely higher sensitivity due to a less
stiff enclosure, they have far less displacement and travel and do
not need the heavy suspension that big excursion drivers require.
Low excursion drivers need some seriously large enclosures to
produce the same SPL as a large excursion driver will in a much
smaller enclosure. Plus they won't reach as low as most large
excursion drivers will.
I run an AV-12 in a sealed .5Q Enclosure fed 500W RMS and I can
bottom it out if I am not careful and that's with 23mm of linear
travel and more than 30mm of X-Sus.. Granted I am running that
driver in a 14" x 14" x 15" enclosure Read: Small :) |
|
|
| kelticwizard |
Actually, Brett, I think the way it works is this. The magnetic gap working on the voice coil is where the driving power comes from.
Two drivers both have a magnetic gap of 0.25" and equal magnets with equal magnetic power, (flux), in that gap. The driver with a 0.5" voice coil winding will have half it's voice coil in the magnetic gap at any given time. The driver with a 1" voice coil winding will have only one quarter of it's voice coil in the gap at any given time. The 1 inch voice coil driver has greater excursion and air moving ability, but the 0.5" will play louder on the same power input. |
|
|
| navin |
| quote: | Originally posted by Brett D.
My opinion is that amplifier power is cheap for sub purposes it's
not like you need a Pass Labs X series to run a sub so I don't
generaly give much thought to the sensitivity of a sub woofer.......Granted I am running that
driver in a 14" x 14" x 15" enclosure Read: Small :) |
nice big amps are expensive. |
|
|
| Brett D. |
Keltic,
Sorry I didn't go into detail about the magnetic gap I was just
speaking solely of the suspension. The suspension alone is never
the full measure of any driver obviously. It's highly unlikely that a
driver with a robust suspension will have a short voice coil as that
goes against what it was designed for.
That being said, give me the large excursion driver any day, no
matter what the sensitivity is.. I don't even consider sensitivity
unless I am looking at midrange and tweeters. |
|
|
| Brett D. |
Navin,
For subs? Nope.. You don't need some esoteric "high end" amp
to drive a sub woofer.. Any amplifiers distorsion figures will be
far better than a subwoofers distorsion. I'd stick with the elite,
expensive amps on the top end.. Use Pro or Plates for the subs.
But that is, as always just my opinion and YMMV :) |
|
|
| navin |
| dont those plate amps have awfully small power supplies. i thoguth you need a lot of curent dumping capacity (read as big power supply) to feed subs. yes you might not need class A but a big power supply is certainly required. and these are expensive. |
|
|
| kelticwizard |
What Navin is trying to say, and I have had the same thoughts, is that when you take a look at some of these superheavyweights and see such low sensitivities, you have to wonder if you wouldn't be better off with a small excursioned driver and a smaller amp.
At some point, the sensitivity is so low that you never get to use the extra excursion because your maximum rated power has run out. When you have your amplifier having to play 500 watts to achieve the same SPL that a more efficient driver only has to play 125 watts to achieve, the SPL won't be that high when the maximum power input is achieved.
This is another argument in favor of ported subs, which cut cone excursion by 4 at the resonance point. This allows the use of a shorter voice coil, therefore makes for a more sensitive sub. However, ported is not necessarily the best choice in every subwoofer application. |
|
|
| 7V |
| quote: | Originally posted by kelticwizard
Here is a link to a chart of Room Gain. This is an approximation-other charts will differ slightly.
It's all guesswork because of the room and it's modes anyway, but at least you can get an idea.
http://www.speakerbuilding.com/content/1020/rge.gif |
So, roughly speaking you're 5dB down at 20Hz (relative to 30Hz). When you take into account the dramatic frequency peaks and troughs brought about by room resonances at bass frequencies I would say that this 5dB is, in practice, virtually insignificant.
Also, if you're planning to place a single subwoofer in a corner of the room in order to couple it to the room (a reasonable approach) then you can assume that the sub would be boosted by the room. You would probably need approximately 3dB less than the maximum SPL of your main speakers (+6dB for the room, -3db because there's only one sub but two mains). |
|
|
| kelticwizard |
| quote: | Originally posted by Brett D.
It's highly unlikely that a
driver with a robust suspension will have a short voice coil as that
goes against what it was designed for.
That being said, give me the large excursion driver any day, no
matter what the sensitivity is.. I don't even consider sensitivity
unless I am looking at midrange and tweeters. |
Brett:
Actually, the example I gave of a 0.5" voice coil really wouldn't be adequate for any sub that anyone would want. What I meant was, when you have a choice between a 1" excursion, (midpoint-to-extreme) sub of 84 dB, and a 0.5" excursion, (midpoint-to-extreme) sub of 88 dB, you might be better off going with the more efficient sub in terms of maximum SPL's produced at the lowest frequency.
Everything is a balance. |
|
|
| subwo1 |
| quote: | Originally posted by kelticwizard
Brett:
Actually, the example I gave of a 0.5" voice coil really wouldn't be adequate for any sub that anyone would want. What I meant was, when you have a choice between a 1" excursion, (midpoint-to-extreme) sub of 84 dB, and a 0.5" excursion, (midpoint-to-extreme) sub of 88 dB, you might be better off going with the more efficient sub in terms of maximum SPL's produced at the lowest frequency.
Everything is a balance. |
Some woofers may get a boost in SPL rating by using tighter suspension, not more flux on the voice coil. |
|
|
| navin |
| thanks kelticwizard |
|
|
| DIY_Peter |
| quote: | Originally posted by navin
Ex: Driver with Xmax 27mm sens is 84db, Driver with Xmax 13mm Sens is 89db and Driver with Xmax 9mm Sens is 92db (all these 3 are well known 12" drivers).
|
Xmax=27mm?? You mean +/- 27mm?
I thought that +/-10mm was already a very high Xmax, like the Peerless XLS range.
Which drivers are you refering to Navin? |
|
|
| navin |
| i saw them on the net. i guess one of the others will have a link. i dont use bookmarks. |
|
|
| kelticwizard |
| quote: | Originally posted by DIY_Peter
Xmax=27mm?? You mean +/- 27mm?
I thought that +/-10mm was already a very high Xmax, like the Peerless XLS range.
Which drivers are you refering to Navin? |
I believe the Blueprint 1503 and 1203 had Xmax ±25 mm, in fact a little over. Then there is the TC Sounds with linear excursions ±1.5 inches. Adire has a huge subwoofer that is ±1 inch as well.
I am not certain, but I think one of the models of Strykes is made by TC Sounds. It could be the very model this thread is about.
And yes, even ±10 mm is very good. It used to be the best subwoofers around had excursions of ±0.25", (6mm), until the Excursion Race started about a dozen years ago.
http://www.tcsounds.com/
http://www.adireaudio.com/diy_audio...dire/tumult.htm |
|
|
| kelticwizard |
| quote: | Originally posted by subwo1
Some woofers may get a boost in SPL rating by using tighter suspension, not more flux on the voice coil. |
I always kind of suspected that. PA speakers have a short voice coil, but not that short, and they sometimes have sensitivities over 100 dB @ 1W/1M. They have very stiff suspensions. |
|
|
| pinkmouse |
| quote: | Originally posted by kelticwizard
I always kind of suspected that. PA speakers have a short voice coil, but not that short, and they sometimes have sensitivities over 100 dB @ 1W/1M. They have very stiff suspensions. |
It is also very rare to see PA drivers with anything but paper cones...;) |
|
|
| Brett D. |
Navin,
The better question would be: Just how big of a tranny does a
350 to 500 watt monoral amp need?
The plate amp I run is 500 watts RMS Mono and runs a larger
toroid than most class A two channel amps. Alternately most of
these sub amps run in Class A/B or G and D I believe and they are
all certainly more efficient than a pure class A amp though some
would argue not as "musical" but for sub frequency use what is
exactly audible? Drivers can make as much as 40% distorsion and
I don't think the human ears can even pick up on this, a measurement
mic can.
I guess it's all in what you want.. I am into HT and 2Channel and
because of this I need a large excursion driver to produce lower
than 20Hz info in movies... For music you never see much below
the 30's unless it's Pipe Organs. A high sensitivity modest excursion
driver certainly "can" work given the right enclosure and tunning.
In the end, like everything else it all boils down to preference or
design philosophy. |
|
|
| navin |
| given that your plate amp might cost more than some class A amps. |
|
|
| Brett D. |
If I told you what I paid for my Carver Sunfire plate amp you
would smack me :) It's from an OEM'd sub and the company (AR)
was selling off thier parts replacement stock to a surplus company.
Believe it or not.. I paid a whopping $54.00 for a brand new
sealed 500 Watt RMS Bob Carver Sunfire TDC Sub Amp with a
Variable 40-120Hz XO and a Audio/Video Selector (Video adds
Bass Boost, Audio is Flat) Plus Gain Control. It was meant for
the European Models (240V) but luckily I have a 220V Receptacle
in my Living Room. :)
But I agree my luck is not the standard.. But you can still buy
QSC or Crown Pro Amps cheaply and add a Behringer Feedback
Destroyer for EQing... |
|
|
| 7V |
| quote: | Originally posted by Brett D.
Believe it or not.. I paid a whopping $54.00 for a brand new
sealed 500 Watt RMS Bob Carver Sunfire TDC Sub Amp with a
Variable 40-120Hz XO and a Audio/Video Selector (Video adds
Bass Boost, Audio is Flat) Plus Gain Control. :) |
You've been robbed, Brett. If the company won't refund your hard-earned money, I am prepared to reimburse your original stake - only because I feel strongly for the victims of this sort of scam. |
|
|
| Brett D. |
Steve,
I know, I know! I was a victim... It happens! But through years
of counsuling perhaps I will recover?
I wish I would have bought a pair! Since when I run dual stereo
sealed AV-12's I need another amp.. Chances are I won't find
another one of these when I need one.. *Shrugs* I guess I will
just go with a QSC Amp and a Behringer FBD |
|
|
| navin |
| quote: | Originally posted by Brett D.
Believe it or not.. I paid a whopping $54.00 for a brand new
sealed 500 Watt RMS Bob Carver Sunfire TDC Sub Amp
... |
You lucky ........ :-) I'd say more but then dave'd dump me in the sin bin. :-) |
|
|
| smithsonga |
Guys
Here is the graph from WinISD...ORANGE line is with two lambda SB15 drivers, 390 liter box. (smaller box increased loss at 20hz and raised a peak in the 40-50Hz range and if I got even smaller, I lost more at 20Hz...go larger didnt do too much.
Thoughts on this graph? Figured between room gain and equalization, I can raise the 20 Hz -6dB loss. But I keep my sealed system with low group delay.
The GREEN line is a ported system using Lambda PB15, same size enclosure, tuned to 22Hz. I prefer the sealed. |
|
|
| navin |
| you ever consdiered what you gonna do when all your room stuff resonates? bass traps and diffusers will be order of the day. |
|
|
|
