audio-talk

[SteveTheShadow]

[andrew Ivimey]

'I'll build it using my existing subwoofers to test the concept. If it succeeds I'll think about bigger bass drivers fed from more powerful solid state plate amps.'

Burn him! Burn Him! He is a witch!

' ... and that, my Liege, is how we know the earth to be banana shaped...'

[Clive]

I expect Steve has finished the speakers by now and is listening to them, knowing his rate of work!

OK, so it is heresy to adulterate valve systems with solid state amps. Of course a nice KT88 P-P could be used but here's my opinion and experience of my system in my room.

Until I got a calibrated mic and analysis s/w I didn't appreciate how much my room was impacting bass. The room modes are really quite large and they resulted a sound that was great for some albums but lousy with a few where the notes coincided with the room modes. Also my subs were setup with a bit of hole between them and the OBs. Having got integratation right using measurement I then still had to kill the room modes. Now I'm a vinyl, SET and OB guy so introducing digital EQ into my system took me a while to come around to, certainly it's going nowhere near the OBs!

The effect of sorting out the sound of the room is so dramatic that I have to use digital EQ, all purist thoughts are trumped by digital EQ on the bass. So, my opinion is that using active subs with OBs is a great match and it allows the use of digital EQ. Also, as the crossover point is around 100Hz the digital EQ assists quite a way up the bass frequency band. Just my opinion FWIW.

[Max N]

Very interesting stuff from Clive and it ties in with my experience.
I've been on a bit of a surround sound detour lately. (Many years ago, in my single days, I had a pretty good surround system, but it got retired when I became a family man)
Recently I built some speakers to go either side of the telly, things snow-balled and I ended up with a 4.1 system with a NAD T175 processor. The NAD comes with Audyssey room equalization, which is highly regarded. Well, to cut a long story short, I was never entirely happy with the Audyssey EQ - it did a good job with the bass, but it lost some transparency in the midrange. Instruments sounded less real, music was less involving and less satisfying. (Audyssey works on all channels, not just the sub.) Having heard how much better things sounded in the bass when the room modes were under control, I didn't want to go back to the boomy bass. Audyssey had shown me that my speakers weren't boomy, they were just (inevitably) exciting the room modes.
I have ended up turning the Audyssey off and applying room EQ to just the sub, using the excellent Room Equalization Wizard (REW) software and a Behringer Feedback Destroyer (BFD). Lots of information about both and a useful forum here:
http://www.hometheatershack.com/roomeq/
So essentially I've arrived at a similar place to Clive, applying EQ to the sub channel only and leaving everything else as clean as possible.
I would definitely recommend downloading REW and getting hold of a cheap RS SPL meter to anyone going the subwoofer route. Useful both for integration and analysing room modes.

[cressy]

why not use those 2 8" rel subs i gave you and get a pair of t-amps to power the subs? they ought to put about 50wpc out and in an 11 litre box should give you what you need in terms of to grunt

[Clive]

Having got my bass working really well I now realise that that the previously slightly overblown bass was masking some unwanted reflections from behind the open baffles. Hanging carpet felt behind the speakers makes such a difference, not surprising for OBs but nonetheless the extra damping really works. Big, rich and atmospheric sounds are back, sorting out had the bass "exposed" the mid a top a little.



Not pretty but pretty effective. It's the green felt on the edges of the bay. The lesson I've learnt here is to not neglect the room, especially where OBs are concerned. I knew it really but just never got around to it.

[richardcooper2k]

too much chintz and not enough hifi

[Clive]

Not enough hi-fi I get complaints about 4 x 12" widebands for the OBs, 2 x 15" for the sealed subs and 2 x 18" for the dipole subs. When I get back from SF next weekend I'll experiment with reducing the damping (carpet felt - chintz?) by 50%.

[SteveTheShadow]

Well I've been playing around with the subs in preparation for actually building the new baffles in time for Owston.

I decided to perch the mini-baffles on top of the subwoofers with bass drivers in the subs facing backwards. A bit of a jury rig TBH and it looked awful.

The sound however was far from awful and seems to bode well for the eventual integration of the subwoofers into the bases of the new baffle design.

Mars, from Simon Rattle's 2005 production of Holst's Planets Suite with the Berlin Phil on EMI was pretty rousing stuff and pretty terrifying in parts. Timp rolls, thundered across the room and for the first time since I'd had the Naim amps, all those years ago, the force of the kettle drums were actually felt as pulses in the chest. The subs provided the rumble from the drums whilst the Axiom 401s provided the machine gun chest rattle of the beaters hitting the skins. Discontinuities were noticeable by their complete absence.

A good start I thought and the speakers were able to provide subtle details and plenty of hall ambience at the same time as all this bombast at the bottom end was happening.

Turning to a bit of eighties soul "Ai No Corrida" by Quincy Jones was cued up in the CD player. This track recorded using the "acusonic recording process" (yeah right) is extremely complex and to be honest had not been played since the days of my Naim 32/250 amp. I was not expecting 6watts of SE valve amp, or any valve amp for that matter to be able to unravel it,
and reproduce it convincingly, with the requisite funk and groove intact

It came up with all the shakers bells and twiddly bits intact plus the vital propulsive groove and a nice spread of ambience behind the musicians.
I enjoyed the track so my Eighties Soul Weekender recordings were dug out.

Booker Newbury III, Mezzoforte, D-Train, Brass Construction, Sister Sledge, Kool & The Gang, Rick James, Jermaine Jackson, James Ingram, Luther Vandross, Yarborough & Peoples, The Fatback Band, Narada Michael Walden and so on and on were spun up for the first time in almost 15 years, and all were handled with suitable bump and grind. All in all it was a very enjoyable blast from the past session.

I only went to clubs in the North but listening to Eighties Soul again, I can just see the young DTB and his mates on the pull down the Lacy Lady Canvey Island, supping weak lager out of plastic glasses with Chris Hill or Robbie Vincent, spinning the wheels of steel, pounding out this stuff till sun-up.Yeh!

Can't wait to get these speakers properly built now.

Steve

[richardcooper2k]

oh stop it steve. you're making me want to build some (been thinking about building some like nick's for some time but like the idea of more beefy mid range drivers like yours-prehaps i'm barking(mad)up the wrong tree though)

[Dave the bass]

[Nick]

Err, you do know you are talking about yourself in the third person?

[Dave the bass]

[pre65]

[Prince of Darkness]