vainajala

Hello audioguru, The graph is frequency response of the prototype speaker, measures at approximately 1 meter away. Do you think it's totally messed up? How should 2-way speaker's phase response look like? Your comment made me suspicious to my measurements, so i'll have to re-measure to see if all went right. Seems like I'll have to increase the levels quite a bit. With as little level as -15dB (as in my graph), even the background noise might affect the results. And, the bass-area peaks and valleys might be caused by room standing waves.

Thread resurrection... 8) 8) Lately I've been busy trying different cross-over types, and found out that 2nd order Bessel filters, crossing at 2 KHz, seems to work quite well. I built a prototype-speaker and measured it, here is the resulted far-field frequency response. Only bad thing is that the highest frequencies have 6db rise between 10-20 KHz. But when listening (and measuring) the speaker at approximately 15-20 degrees off-axis, response flattens nicely. This measurement was done off-axis.

...and another pic... ::)

Forget the hat, those are way more important things! But is it really necessary to operate your woofer at its maximum SPL level...? I'm sure it will play gently too, just watch out for over-turning that volume knob! :) ~~~~ I came to think about using 24dB filters for both lowpass & subsonic. Because I heard from my electronics-teacher that steeper-slope filter works generally better with sub-woofers. I made a quick (and really messy) draft, which uses TL074 and TL071 op-amps... Highpass frequency is 15 Hz and lowpass 50 Hz. Propblem is that it needs quad pot to adust the lowpass frequency. and there's no EQ (if that is needed anyway) :P

Wow! :o Be sure to hold your hat while powering those ;D

Hello Brenn Which color Luxeon's are you going to use? Red Luxeon has forward voltage of 2,85V and blue has 3,42V. Four red Luxeons connected in series would have forward voltage of 11,4V. Simplest method for dropping voltage would be a series resistor. (13V-11,4V)/0,35A = 4,6 ohm => 5,6 ohm 2 watt resistor in series with the LED chain. For blue Luxeons, you could connect them series/parallel. For example, two chains of two series-connected LEDs, with each chain has its own series resistor. In this case, (13V-6,84V)/0,35A = 17,6 ohm => 18 ohm 5 watt series resistor for each chain. If you're interested about switch-mode's higer effiency, have a look at switch-mode regulator ICs from National and Maxim. LM2595T-ADJ: http://www.national.com/pf/LM/LM2595.html

I sim'ed the sealed+linkwitz alignment and a normal vented box with WinISD. Both use 50L box and the Linkwitz transform circuit's -3dB point is set to 28Hz. That way it goes quite low and has maximum boost of only 5,5dB. Both use 2nd order Butterworth 65Hz lowpass filter. Since I don't know the woofer's Xmax, I (again) approximated 6mm one-way. For Cone excursion plot: As you can see, sealed+Lw hits the excursion limit at 20Hz with 9W of input power. Reflex hits the limit at ~40Hz with 50W of power, but has higher mechanical power handling at 21-30Hz range. Below 20Hz, it drops very steeply. SPL graph is then simulated by the maximum mechanical power handling. Both are pretty much as (in)effiecient, but bass-reflex can stand more power. Only drawback with reflex is the worse group delay... (the maximum is fortunately below 20-25Hz). The Linkwitz circuit is indeed very good idea, but it could work better with a very long-throw 12"-15" sub. such as some of these: http://www.adireaudio.com/TextPages/TumultPageFrameText.htm http://www.adireaudio.com/TextPages/TempestPageFrameText.htm http://www.adireaudio.com/TextPages/ShivaPageFrameText.htm

Audioguru: I don't know how long Xmax it has, because I don't have any spec-sheets or instructions. This is most propably an automotive 4ohm woofer, so I guess the manufacturer has concentrated a bit more on the glamorous appearance, than the sound itself. It is almost too "pretty" to hide in box... ;D However, it weighs about 6,6 kilograms, has a ventilated 2" aluminium (i guess) voice coil, huge double-magnet, screw wire connectors and 4cm wide surround. Unfortunately, it is foam surround. :-X But considering the 35 euros I paid for it, I don't complain! These parameters are somewhat approximate, because Speaker workshop can't calculate the BL value. So I just approximated a value of 11 into it. I must measure the correct BL value sometime with my school's variable power supplies before making any real decisions for an enclosure. (Approximate) parameters I measured: Fs: 29,8 Hz Qts: 0,617 Qms: 3,617 Qes: 0,743 According to these measurements, this needs a little bigger enclosure than the Peerless woofer. But anyway, this is a 10" woofer, so that doesn't surprise.

I'm 99% certain, that I'll be using this woofer. I got it from friend for 35 euros! :D Now I need only to measure its parameters with Speaker Workshop...

audioguru: If a speaker manufacturer defines itself High-End grade, and then puts a wrong value inductor to their production speakers, does not seem very "High-End" to me. In fact, it's a cardinal mistake. I wonder if the customers (and you) got their money back, because of a "bad" product? Do you think their speakers would still be in sale, if you as a Guru of Audio hadn't been concerned about the parts' quality? From now on I will measure every coil and cap before putting it in work anywhere, especially in speakers! :) My 'dream-speakers', I wonder if they got their inductors correctly: http://www.wilsonaudio.com/products/Alex/index.html

I don't believe it's because of room reflection, tried in very different positions and curve looks almost perfectly same. My old speakers just simply suck. Your speaker-measuring arrangement seems cool. Are you using a laptop-computer for measuring? What program you prefer? I use Speaker workshop, because it's free! I expected that kind of response curve, because high freq. sounds (like cymbals) sound very loud and attacking, and in the lower octaves is almost no energy. It's quite hard to hear even a normal bass-guitar with these speakers. Placing in room has no/very little effect. >:( The Vifa drivers are propably delivered in a couple of days. In next weekend when I get back home from school, I'll build and measure a prototype-speaker... So we'll see how well/bad they perform ::) If they perform reasonably well, that means more work to me: because my brother needs also a pair of compact speakers... ;D

No, the SLS line is mostly meant for indoor-use so only 8 ohm version is available. and I'm not gonna wind new coil into it. ;D You're right, 2dB difference might not be worth that increased complexity at output stage...

<bump #2> Here's the frequency response (20Hz - 16KHz) of my old speakers, I just measured it with Speaker Workshop... The peak at 50Hz is propably mains voltage hum. I think below 35Hz is mostly junk too. They have 8" woofer and 1" dome tweeter, and have no cross-over. Just bipolar cap on tweeter.

I once tried this freeware program, and it actually worked quite well with soundcard input... http://www.saunalahti.fi/elepal/scope3.zip

In my opinion, 8" woofer is rather large for main speaker use, but quite small for sub-woofer use. But bigger cone size doesn't always mean better sound quality. :) About EQ: I think room acoustics will help somewhat with lowest frequencies. If it doesn't work that way then I might consider some sort of sub-bass boosting... 60W isn't very much power, but as the amp designer says: I have five of both MJ15003 and MJ15004 power transistors in my component-box... ::)