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Old 20th December 2004, 10:52 PM   #11
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Default 500 watt plate amp $250

A sealed box woofer should give the best quality transients, so consider more power. Parts Express, for example, has a 500 watts into 4 ohm plate amp for $250, as well as a 1000 watt for $350.

I'm sure your ran many models. A more efficient woofer would have a higher Fs, and hence give up deep bass. OR a more efficient woofer would have lower Qts, and require a port to extend the bass which will compromise transients.


http://www.partsexpress.com/pe/showd...number=300-806


"One of the most technologically advanced subwoofer amplifiers on the market!
This new subwoofer amplifier is based on state-of-the-art Class G circuit topology that combines the proven high power, high fidelity characteristics of a Class AB amplifier with a patented tracking down converter power supply to achieve an operating efficiency up to 86%. You get the efficiency of a Class D amplifier without compromising audio quality and reliability. The class AB output stage provides the clean and low-distortion sound that audiophiles demand, without any instability problems of other high-efficiency amplifier designs. This American designed and engineered amplifier uses patented circuitry that continuously tracks the input signal to modulate or control the voltage available to the output stage. This "tracking" capability delivers the exact amount of power based on demand instead of constantly keeping it in reserve, so the output stage only draws the amount of power that is required at any given time. This means less energy is wasted as heat, and more power is available for the subwoofer driver. "
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Old 21st December 2004, 12:25 AM   #12
AR2 is offline AR2  United States
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Just as I went through the design of my speakers all your answers came to my mind. All of the suggestions are great and correct. Let me post some answers to your questions/ suggestions and then we could decide on the path.
I do like mid / high combo a lot and it is a match from haven. Particularly 10” PHL driven by low powered 2A3 amp. After having ribbon I would never go back to conventional tweeter. It is such a great speaker that is not harsh even when driven with SS amp such as GC ( I use to drive it with another tube amp, but it is better with GC)
Lambda is high quality speaker and in sealed box sounds very natural. I chose sealed box over vented because that is my preference – sonically. It is hard to find speaker that is very efficient, has a very low fs and is meant for sealed enclosure. It is usually ether or.
Just like Line Source pointed out and I couldn’t spell it better.
I checked for Gamma la1231, since I am not familiar with that speaker and I couldn’t find much info. It is certainly interesting speaker based on the specs, the only question is if it is constructed with sealed or vented design in mind. 12 incher, 96 dB with 25Hz Fs hopefully in sealed box (as much as I gathered over web) Price is great and the only problem is shipping it from Europe since it is not available here in States. For the price it is worth buying it and placing in the same box.
The reason I am stuck on Lambda is sound quality. It is crossed at 225Hz, and even sounds better when crossed at 300Hz as I tried in few experiments. The box is 78 liters. At those frequencies I still need good and clean amplification. I never tried plate amps, but somehow I trust more brute power and lots of iron/aluminum. I certainly could be wrong but with great amp I am sure my chances are better.
My crossover is based on Burr Brown opamps and it allows –12+6dB adjustment per output. On the top of that I am using DEQ2496 just for the Lambda in order to eq. and to increase the signal about 4 db. After that it goes into class AB Mosfet. With this set up I am able to match Lambdas with the rest, mostly because upper end is driven with low powered amps and because I am amping LF signal before the amp.
I do not like the fact that I have to do so much on the signal, and I would rather put more current from the amp than do what I am doing now. It certainly will be cleaner giving the proper amp to the speaker. If I forget on the matching with Mid/High which so far is working, that speaker needs better amp. That would stand for majority of low extension high quality sealed woofers. Another approach would be designing the cabined with several woofers of the same kind, but that will present us with another problems, such as huge size of the box and difficulties in finding the proper position for ribbon (very limited horizontal dispersion) I think I found a very good compromise for what I like. All that is missing is better amp. Changing the speaker is a solution as well but with another problems introduced.
I measured Lambdas after I built them and based on that I realized that they did very good job up to 30 Hz. I have to admit that my measurement tools are not the best – Behringer mic, and at the time Speaker Workshop in my room – not outside. I am now on Sound Easy. If it helps I could post measurements just have to find them which will take some time, or I will be happy to make new ones. Seeing curves and more than that listening these speakers makes me think that it worth try. As I mentioned I already started collecting parts so I could end up with great amp even if I realized that I should change the speaker. The biggest question is which Uli pointed out: Does class A brings any benefit or should I stick with class AB with lots of current. If that is the case could Aleph X be configured that way?
Thank you all for the great discussion
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Old 21st December 2004, 12:39 AM   #13
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The only benefit of classA over well-implemented AB for high power is to the local electric company when you pay your monthly energy bill! (of course, some will be sure to disagree!

I am another vote for at least trying a different bass driver.
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Old 21st December 2004, 02:47 AM   #14
AR2 is offline AR2  United States
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Here is the measurement that I was able to find. It is unsmoothed close mic measurement in FFT program. I hope you will be able to read it. Not very precise but it is enough to give you idea. This was done without any crossover or EQ in the path, just a row driver.
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Old 21st December 2004, 04:11 AM   #15
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Looks as though the driver gives up any pretense of flat response below about 50Hz. I think your ears are telling you accurately that there's not much bass going on. An amp, regardless of operating class or topology, will not cure this problem. Three options occur to me:
1) EQ
2) Different speaker
3) Live with it
At intervals I drop into threads in the Speaker forum and make myself unpopular by telling people that the Titanics and the Shivas and now presumably the Lambdas are not flat. Not even close. To get anything like deep bass out of them, you have to EQ the critters. At this point, people start arguing with me. Generally, after a day or three of posts telling me what an idiot I am, someone posts a frequency response graph and I'm vindicated. That thread slides into the past, and things go quiet for a month...until someone else comes up and says...
You get the picture.
Just be aware that EQ eats power at a prodigious rate. Godzilla can't sit at the same table as an amplifier dealing with EQ, his appetite ain't big enough; can't run with the big beasts. Don't even think about trying EQ with an amp of less than 100W, and that's for low volume listening.
Now that I'm into the reply thing, I no longer have the graph in front of me, but I think you're looking at a 12dB/oct slope starting at about 50Hz or so. Titanics and Shivas tend more towards 6dB/oct and are easier to deal with. This 12 thing is going to get annoying. There are two ways to approach the problem. One is to start a boost at 50Hz. The fly in the ointment is that this is an invitation to serious instability, so you have to stop the boost and go to at least flat response, if not cut, somewhere in the teens. Your other option is to use a low pass filter with a corner frequency somewhere down in the 15-20Hz range. The declining low pass will combine with the declining driver response to give you flat response from the rolloff up to where the driver flattens out, i.e. around 50Hz, at which point you start rolling off the driver when it gets flat. Draw this out on paper, and it will make more sense.
Passive EQ is out of the question, you're talking active here.
The moral of the story is not to trust the simulations. Just to give the flamers a good place to start, I'll say it again--the Thiele-Small simulations lie. They're a nice starting point, but that's all.
It's going to be up to you to decide what the tradeoffs are. Money? Physical space? Fights with your significant other? The only thing I can promise you is that amplifier power alone will not solve this problem.

Grey
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Old 21st December 2004, 07:33 AM   #16
AR2 is offline AR2  United States
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[QUOTE]Originally posted by GRollins
[B]Looks as though the driver gives up any pretense of flat response below about 50Hz. I think your ears are telling you accurately that there's not much bass going on.

To give some proper credit to Lambdas, as I mentioned it was close mike measure. Proper way would be to combine close mike with 1 meter measure and smooth the responce out 1/3 of octave. That usually lift lower freq. up.


At intervals I drop into threads in the Speaker forum and make myself unpopular by telling people that the Titanics and the Shivas and now presumably the Lambdas are not flat.
Not even close. To get anything like deep bass out of them, you have to EQ the critters. At this point, people start arguing with me. Generally, after a day or three of posts telling me what an idiot I am, someone posts a frequency response graph and I'm vindicated.

javascript:smilie('') Sounds like speaker people

Your EQ suggestion describe exactly what I did. I started without it, and it was weak, so I added DEQ 2496. I tried a few combinations and here is one where I pushed it little bit harder. ( See included pict) It is tremendous help. The truth is with all this pushing, Amp does get exhorted as you predicted. Out of my inexperience I was hoping that better amp will eliminate the EQ, thinking that my amp falls short in the low freq. and in combination with difficult speaker just dies out.
Well I have to agree with EQ approach, because something has to level out normal fall off of the sealed speaker. My EQ doesn't support any frequency below 20, so your suggestion on dealing with the teen fq. should be taken care off within the crossover.
So I will take all of your advices:
Keep EQ,
I will certainly try other speaker, at least just to feel the difference. Overall majority of people suggested the very same thing.
And I will certainly live with it, because all considered I like the sound.

That still leave me with one problem to solve. I still need to improve my amp. Even with EQ it easily runs out of power. That 12dB boost sucks out all of the juice and amp obviously suffers. So what amp to chose that will handle this easier?
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Old 21st December 2004, 07:36 AM   #17
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Picture didn't go through. Here it is.
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Old 21st December 2004, 10:04 AM   #18
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In closed box I am using the woofer attached down. In 60 liters it has a -3 db at 70 Hz and then goes down smooth at 12 dB octave. Fs in box is 53 Hz. With the LR equalizer that I use he becamens flat at 30 Hz. The load doesn't go under 7 hom, so it is very easy to drive. Efficiency is about 92 dB, that respect to 86 means that you need 1/4 of the actually power. Works very well until 700 Hz, but I use it at 500 12 dB LR.
Ciao.
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Old 21st December 2004, 03:00 PM   #19
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You can move the test mic around the room and get different curves, but they'll all be variations on the same general theme.
Beware buying other drivers based on simulations--you will likely find yourself no better off than you are now.

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Old 21st December 2004, 07:11 PM   #20
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btw AR2 was a good speaker, not many left unfortunately.
Quote:
I checked for Gamma la1231, since I am not familiar with that speaker and I couldn’t find much info. It is certainly interesting speaker based on the specs, the only question is if it is constructed with sealed or vented design in mind. 12 incher, 96 dB with 25Hz Fs hopefully in sealed box (as much as I gathered over web) Price is great and the only problem is shipping it from Europe since it is not available here in States. For the price it is worth buying it and placing in the same box.
The LA1231 was designed in the early 70´s and is almost identical today, was probably designed for vented designs but works very well in closed systems Qts 0,42; (was used in comercial swedish speaker made of sealed glued marble box of ca 65 litres in the 70´s, actually was pretty good) I´ve heard it in well braced designs, not overly damped, around 75-80 litres and i find it superior to all modern lf drivers with strange conematerials You cant pronunciate. It is almost undestructible regarding power input and has the ,imo, very lifelike soundquality of good quality papercone units. I do not have enough hair on my chest to argue with Grey, but this driver goes subjectively very low in even modest cabinet size.
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