RoHo

whenever I adjust my subwoofer the song I keep coming back to test it out is the Flaming Lips' "Suddenly Everything Has Changed" from the Soft Bulletin album. The album contains lots of deep electronic thumps and groans if that floats your boat, but that song contains several vigorously played runs up and down the fretboard of the bass guitar. This test if I have an even frequency response throughout the bass range. The strings are quite heavily plucked giving a strong "leading edge" sound. I know that if that sound is precisely reproduced then the timing/delay of the subs signal is optimum. If the notes are blurred and muddy then something is wrong with the delay.

Using a sub with bass limited speakers can work really well. If you like the sound of your existing speakers then adding good bass will be an obvious improvement. But to get good bass from a single subwoofer can require some work. You may need to move any of the sub, speakers and listening position around to get acceptable bass ie not lumpy or boomy or weak. You do have to put in some effort to get it to work well. If you are able to do some measurements it will make this process much easier.

IMO there will be absolutely no difference in the operation of any of the 6N1P variants in your typical audio circuits. The "tighter" variants of such tubes were designed for applications, maybe military, where they needed guaranteed specs for certain parameters. Buy whatever is available. With Russian tubes I just buy a bunch on ebay from Ukraine, Russia, Bulgaria, whatever, cheap as chips. Never had a dud and never had any not turn up, eventually. Then I stick 'em in the circuit one by one and measure the plate current and then sort them into pairs. Can't see the point of buying these from established tube stores.

Thanks, Arthur. I wanted a separate volume control for an experiment with my MiniDSP and so I just threw it together. Much quicker than any conventional alternative and chassis work is way down the list of my favourite DIY jobs! Maybe I should keep it in the system permanently? 🙂

As this is the DIY forum I humbly present my SOTA passive pre-amp. Made from a particularly non-resonant form of cellulose fibre, a unique feature in the world of hi-end audio. A big problem with passive pre-amps has been their lack of drive. Not so with mine- note how the volume goes up to eleven. And the shipping costs should I decide to commercialise will be uniquely low. I will just have to whack a stamp on the outside t

Yes, which is frustrating because for most of us the 2x4 has all the features we need. To get better DAC performance you need to shell out 5x the price for the SHD which includes Dirac and streaming functions you are less likely to require. The MiniDSP range is rather complex but I don't think there is a cheaper way to get analog in/out with the upgraded DAC. The SHD also has much more flexible input/output impedances (100/47k) compared with the cheaper models (560/10k).

Absolutely, Andy. I was just thinking I might need to attenuate slightly to keep the level under the 2V max of the miniDSP. Your volume control sounds positively heroic. Implementing a multi channel analogue volume control is a big stumbling block when using MiniDSP with analogue ins and outs.

Done some more reading. Will try the volume control after the MiniDSP and adjust MiniDSP input level to suit.

Thanks, Dave, will try your suggestion. I had thought that using the pot at about 3/4 would not be too much attenuation. What is the optimum way to control volume? If I'm increasing the pot's "baseline" level it won't leave much useful range.

Input side of MiniDSP.

Mine was in between CD player and amps, fed by a pot to adjust level. No attenuation in the MiniDSP itself and the pot was usually at 2-4 "o'clock". Suggest any possible improvements?

Agree with you about the noise. Not everyone has this problem, which puzzles me, but it could be a deal breaker. According to your sig you use a PC as your source? Have you considered doing the crossover and/or bass EQ in software? I have no experience with this but plenty of people use this type of system.

The MiniDSP 2x4HD "in a box" is US$200 and hard to beat. It will do stereo 2-way crossover and EQ or get 2 for a full stereo 3-way. If you already have a spare amp suitable for driving the bass section then it would be very hard to beat.

You've explained what I really couldn't ask about properly! Are there sub-harmonics and are they important? The phase issue is something I had never considered but does make sense. Terrific post, thanks for that.

On the thread I recently started on bass extension I learnt that a specified low frequency limit has little meaning unless it is measured at a LOUD volume. Hence your JBL can maintain the same 40Hz level at 10 or 100dB while another speaker may in fact produce more 30Hz output at very low level but turn up the wick........Your observation of the speakers having "authority" rings absolutely true.