How good can D.I.Y speakers really get? - Enter Mr Al Newall

[Marco]

Dunno what it is, Marco. Everything seems ok. Doesn't do it here at the volume i play at.
Might just be a reflection of the bass wave off the Spendors, which were right behind.

Yes, that could well have been the reason, although it was interesting that it was happening on one speaker more than on the other... I think what we should perhaps do is for me to bring my kit to yours (everything minus the speakers) and see if it happens again. I think it's also partly to do with how they're being driven.

It's an interesting one for sure!

Marco.

[muffinman]

Excellent info here. My mind and heart are set and i'll definatley be doing a straight rip off of alb's design. it's gonna take a few months so i can slip it under the wifedar - no mean feat as she's an air traffic controller
I'd like to use veneered mdf for the baffle so i can get a pretty finish should i like them. this stuff can be a little expensive though so would like to know what the front baffle dimensions are (so i can cost it and decide)

many thanks
Gareth

[muffinman]

I see there are various emince 15s at vaying prices alpha-delta £35-£65ish
are these pretty much similar or is the power handling (200-400w)a major concern. I don't wish to sell my self short but if i don't need to buy the most expensive then that's a help.

[Clive]

Yes, that could well have been the reason, although it was interesting that it was happening on one speaker more than on the other... I think what we should perhaps do is for me to bring my kit to yours (everything minus the speakers) and see if it happens again. I think it's also partly to do with how they're being driven.

It's an interesting one for sure!

Marco.

Marco, it seems unlikely that a reflected bass wave from your Spendors would cause cone displacement on the OB bass. As you suggest it seems more likely that this is something to track down upstream. Was this a big cone movement, ie like a badly warped record can cause? Did it happen with CD too? I assume it wasn't continuous, just when music was playing, did it happen all the time music was playing? Valve pre and power amps when they go unstable they "motorboat", this is a low frequency beating, normally though you would hear this rather than only see it and it would be continuous.

[Mike]

Dunno what it is, Marco. Everything seems ok. Doesn't do it here at the volume i play at.
Might just be a reflection of the bass wave off the Spendors, which were right behind.

Don't worry. It's just the LF instability in Marco's rubbish old music centre!

[Mike]

Oh, I see Clive beat me to it.... Sorry.

[Ali Tait]

Hi Gareth,
Al will confirm I'm sure,but I think he used the Betas.I think the different models have different impedances and sensitivity.

[alb]

Clive.

It's just a noticeable cone movement on the full range drivers. These only have an Xmax of 1mm and normally don't move visibly on my system.
It's nothing like motorboating or the kind of movement you get with dc.

I'd expect this to happen if i was running them as full range, but they should be crossing over at 120Hz. Its not enough to concern me, but the fact it was more obvious on the left side just made me think.

[Marco]

LOL, Mikey, good one!

Marco, it seems unlikely that a reflected bass wave from your Spendors would cause cone displacement on the OB bass. As you suggest it seems more likely that this is something to track down upstream. Was this a big cone movement, ie like a badly warped record can cause? Did it happen with CD too? I assume it wasn't continuous, just when music was playing, did it happen all the time music was playing? Valve pre and power amps when they go unstable they "motorboat", this is a low frequency beating, normally though you would hear this rather than only see it and it would be continuous.

Clive, I'm sure Al will be able to describe it much better than I can, but I don't think it's as a result of what you describe above. The best way I can describe it is that the 'full-range' drivers (their response tailored to be used as midrange and high frequency units) were 'pulsing', or moving in a piston-like fashion, in time with the music and in conjunction with the bass cones, but on one speaker it was doing it significantly more (L/H channel) than on the other.

I'd be interested in your further thoughts on this. I basically put it down to my rather punchier and more powerful push-pull amp putting more bass energy into the drive units than normally happens with Al's SET amp, together with perhaps the slightly more capable source components reproducing a stronger 'musical signal' and thus both combining to drive the speakers much harder than normal with Al's equipment.

It's worth noting also that at no point was there any audible distortion and that the speakers could quite clearly be driven very loudly and with seemingly endless available headroom.

That's why I'd like to take my gear around to Al's and see if the same thing happens in a different room and without the Spendors in situ, and also compare the effect of Al's source and control components to mine using his speakers. The only way to ascertain what's happening is to remove as many variables as possible.

Marco.

[aquapiranha]

Perhaps the filters are not doing the job properly? I would imagine that may be a possible cause, and as for the effect being greater on one side that may simply be down to to the fact that bass is considerably less directional than mid / treble energy and therefore it would "sound" like the problem is coming from both channels? all hypothetical of course.