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I am hugely encouraged by the runaway success of my midrange, so I press on.
Hello,no correction best regards Gilles
Thats great Gilles. Do you have a reference to your system?
I have been reflecting on my 15" bass drivers which are vintage alnico Altec 416B. They are what is know as VOTT, meaning 'Voice of the Theatre', and spent their formative years in a theatre or cinema so I guess they are well able to pump out the low frequencies Up till now, running in unison with the mid range and tweeter fed by a single amp, they deliver an acceptable level of bass for me, but interestingly I have never really seen the cones move even on heavy bass notes. I am therefore guessing with a separate amp and DSP I may be able to release the genie from the bottle.
I use active servo bass drivers in my setup (GR Research Super 7s). It's nice because it goes to 20hz with tons of power, but is also extremely fast, tight and tuneful. They'll play up to 200hz and thus will mate with just about any "top portion" you care to run. It's nice because it solves the whole bass issue in one elegant package. Servo drivers in an OB config really is a game changer.
Interesting alternative. Do you have a website reference?
The kits are on the GR Research website here - http://gr-research.com/diysubwooferkits.aspxAnd they also have a forum here on AC. The thread that's probably most relevant to check out is the one discussing the H-Frame flat packs, here - https://www.audiocircle.com/index.php?topic=139480.0
Its always an interesting debate around Qts. Many of us, including me, learnt most of what we know from the Lampizator.Here is how he describes the bass driver with a recommendation for the Altec in the P17 on which mine are based - Max Fs 37Hz, optimum 25HzMin sensitivity 97dBMax Qts 1 optimum 0.35The other advantage of the Altecs in my baffles is the voicing marries up beautifully with vintage alnico magnet, paper cones of the mid and tweeter.I have an open mind on this and if not successful with the Altecs I'm quite prepared to try others.
I would welcome your response.
I agree with your observations and definition.The "Q" of a second order system is a simple measure of resonant damping. Q < 0.7 is overdamped and less resonant, Q > 0.7 is underdamped and more resonant.High Qts driver are used in open baffle to increase bass near the drivers Fs. I believe this comes at the cost of ringing and poor impulse response.My obs and listening tests lead me to the conclusion that high Qts is undesirable unless the system needs to be passive.Active systems can tolerate low Qts drivers and give better performance but require more power and more EQ. I personally went for a Qts just under 0.7 in an attempt to get good impulse response with minimal EQ. The result seems to be tight, deep and "effortless" bass. The majority of GR Research's excellent servo subs also have Qts near 0.7 with one notable exception.
While a high Qts (1.0 to 1.5) woofer will ring in a box when placed in an OB the low end will be rolled off and the resulting combined SPL response will be flat and then roll off to eventually become an 18 dB/octave slope. You can adjust the depth and shape of the bass response by changing the size of the baffle and the position of the woofer.
However, the resonance at Fs is still occurring and results in the desired bass boost that some Open Baffle designers are after. BUT, the boost is only a result of resonance and this can be heard as a bass artifact and impacts the impulse response due to ringing.
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