Something stirs in the Undergrowth

Dedicated to those large boxes at one end of the room
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Toppsy
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#2701 Re: Something stirs in the Undergrowth

Post by Toppsy »

Yes the standard tubes are Philips ECC88 Jan 6922. I bought my reference model direct from AH! and had it fitted with Siemons E288CC. Best sound I got from this player. According to my user manual tubes from the 6DJ8 / 88/ 6922 family can be used. You can use 6N1P as long as R15 (being 1 Ohm) is changes to 0 Ohm (take R15 out and replace with a small wire-bridge. This procedure is illustrated in the user manual. I can email yo a scanned copy if you don't have one?
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IslandPink
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#2702 Re: Something stirs in the Undergrowth

Post by IslandPink »

Let me see what I has first Colin - no rush.

Have been listening more, definitely the back enclosure is needed. There's no 'ping' or focus to the bass end of its response at present. Just been out making a start on that - took the wooden box and have hacked out a load of 'devil's candy-floss' with a knife and chisel.
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IslandPink
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#2703 Re: Something stirs in the Undergrowth

Post by IslandPink »

I thought I was doing quite well with this, till I checked putting the circular part over the phase plug surround here, and found I'd made it just ever so slightly ( 0.2mm ? ) too small on diameter.
Grrr !
Horn1p9m_enclosure1.JPG
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#2704 Re: Something stirs in the Undergrowth

Post by IslandPink »

Getting there ... finally got some time today.
Will get the driver in there and wired up later. Might try just putting a flat lid on there first - that will give me about 5L , which is a bit small, but will give me an idea of what changes occur.
Horn1p9m_enclosure_half.JPG
Bastard ! - driver doesn't go down fully - more fettling required. I was just about to get a first listening.
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IslandPink
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#2705 Re: Something stirs in the Undergrowth

Post by IslandPink »

First impressions are not good. I have tried it with heavy 3/4" lid on the top, weighted down ; also with a shim wedging the lid open slightly to simulate a larger box. However it may be that I've overshot significantly with 5L. The next step is either to build up the sides by 2" or so, or find cardboard & fabricate a half-box for more volume at the top.
This will have to wait till Sunday. I need to get over to the slate quarry tomorrow to find a Christmas present !
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IslandPink
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#2706 Re: Something stirs in the Undergrowth

Post by IslandPink »

Found a good box made from thick cardboard. A bit of penknife work and some gaffer tape, and it fits over the wooden box snugly. I set the height to give about 11 litres total now.
Just listening. It's better than either no box or 5L ,but there doesn't seem to be any magic. Is this the end of the horn bass/mid ? Probably.
I am already thinking about OB for 100-600Hz with something like a PM6A.....
Horn1p9m_hybridbox_11L.JPG
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chris661
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#2707 Re: Something stirs in the Undergrowth

Post by chris661 »

IslandPink wrote: Thu Dec 17, 2020 10:17 pm
Just listening. It's better than either no box or 5L ,but there doesn't seem to be any magic. Is this the end of the horn bass/mid ? Probably.
I am already thinking about OB for 100-600Hz with something like a PM6A.....
There are certainly more compact solutions available, Mark.

For OB 100-600Hz, I'd be looking for 10" or larger drivers. The last time I tried OB, it was a 3-way system with a Beyma 15P1200Nd, Faital 10FH520 and EV DH1a per side. Tri-amped.

I tried running it as a 2-way (10"+HF) and barely got to 60Hz (with some EQ boost for the bottom end) - the 10" cone was flapping around all over the place. 100Hz would probably be reasonably comfortable for a 10", but I'd still consider a 12" to keep things happy.

Question: have you considered a passive cardioid?
I'm wondering if having half of your sound radiation firing into a bay window is a great idea.

Chris
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#2708 Re: Something stirs in the Undergrowth

Post by simon »

Don't know if the bay is an issue for Mark but at our last house I tried speakers in the bay and it really didn't work, I moved them sharpish.
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#2709 Re: Something stirs in the Undergrowth

Post by IslandPink »

Thanks for your thoughts.
I was under the impression I had something like a passive cardoid , with the quasars, at least at some frequencies - but James knows more about the specifics, perhaps he can comment. I know that firing into the sides of the bay ( with the wall and window slanting at about 45° away ) is definitely better than firing towards a flat wall. However, I can try some options at least with a single test-bed.
The key thing is that in the past, I mainly tried to get an integration with the horn and a dual-driver Quasar combo, with the series cross at 180 or 200Hz. This ultimately didn't work, as the 600Hz low-pass I was trying to get on the mid driver was screwing-up the bass/mid crossover - they were too close.
I did have some great results on a couple of occasions, at least in mono, with a horn and the B&C 8PE21 - however this driver was too low Q ( rising response ) and didn't have enough response lower down.
I will start with Fostex FF225WK, which has the right sort of parameters. Maybe PM6A will have problems with excursion - yes. However I don't play very loud ... and I only need to go to 70 or 80Hz on the rolled-off response, I could control cone motion with a HP at say 30 or 40Hz . We'll see.
The other option is to dig out the 12" alnico Tone Tubbies - they will have no trouble going louder, and a bit lower - but I never got a great result from them before - again, worth another try.
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chris661
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#2710 Re: Something stirs in the Undergrowth

Post by chris661 »

IslandPink wrote: Sat Dec 19, 2020 1:09 pm
I was under the impression I had something like a passive cardoid , with the quasars, at least at some frequencies - but James knows more about the specifics, perhaps he can comment.
I think James and I disagree on the cardioid-ness of the Quasar baffles. In my experience with microphones (which are often passive cardioids) and looking at other attempts at passive cardioid speakers, there needs to be some absorption at the rear.

There's a big thread here: https://www.diyaudio.com/forums/multi-w ... dioid.html

With some good stuff starting at page 5-6.

This post: https://www.diyaudio.com/forums/multi-w ... ost4332277
Shows what you get with just a U-frame. Dipole at low frequencies, and then a mix of omni/hypercardioid as you move up and things get more chaotic. There might be some frequency where the speaker is acting as an actual cardioid, but it's certainly not over a broad range.

Further along in that thread, the poster finds a combination of slots and absorption that give a good approximation of cardioid performance, over a couple of octaves.

Chris

PS - If your SPL demands are fairly modest, then I'd be looking for a simpler system overall. IMO, the only reason to split the frequency range up is additional output: crossovers are best avoided when possible, but I'd rather have a crossover than a 3" cone flapping away trying to produce 40Hz-20kHz. The speakers I have at the moment are a 2-way design. If you turn it up loud, there's a bit of harmonic distortion in the bass, but I'm willing to put up with that - the alternative is a 3-way system with dedicated bass drivers. Bigger cabinets, more complexity. Can't be bothered. This is good enough.
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#2711 Re: Something stirs in the Undergrowth

Post by IslandPink »

I'm not going to start from scratch with the system, Chris :) . I know what I have and what's good. The wooden bi-radial with the 288H, plus the ribbon, is the best thing I've ever heard, especially when driven from that 45 SE amp. That's why I will continue with a few more experiments. The combos I had before with cone for lower mid were all hampered by me trying to get bass and mids with a 2-way below. In that sense I also don't want to get too wound up in dealing with this as cardoid/room issue, when it may not be . That is easy to establish ( or not ) once I have the two drivers mounted up. There was no sign of any trouble when the Azura horn and B&C driver were paired.

The advantage of running (only) a middling-Q bass/mid driver on OB is that it has relatively benign phase behaviour as it rolls off below 100Hz, so you should get a good integration from mids to upper bass, without the compromises that the Quasar has around 150/200Hz.
I think the FF225WK is the best bet at first.
I had another look at the Tone Tubby 12" alnico, they now have new data -
https://www.tonetubby.com/all-products/alnico-black-dd/
but to be honest the low BL and really high Qts on there doesn't seem right ( it has a big peak around resonance , when simulated on IB with Hornresp ) and it doesn't reconcile with the graph they show on that page, which also has other T/S data ( Qts = 0.7 ! ). That one is going to take measurements in the room to sort out !

Of course, aside from the tapped horn, this system is looking to be rather like what Steve has .. !
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chris661
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#2712 Re: Something stirs in the Undergrowth

Post by chris661 »

Fair enough, Mark. It's confusing for me, sometimes, to watch you go to all this trouble when I have a 2-way setup that works for me - measures well and sounds great.

Given the placement, I do think cardioid speakers would be worth a look, and the thread I linked above is well-documented. I'm planning on trying something similar to this:
https://www.diyaudio.com/forums/multi-w ... akers.html

Where a wide-band dipole unit is mated with midbass omni unit to create a cardioid through most of the range. I do suspect the concept can be taken further - for example, a passive cardioid above a few kHz would extend the pattern control.

Chris
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#2713 Re: Something stirs in the Undergrowth

Post by vinylnvalves »

Chris, I know where there are a pair of Linkwitz Pluto’s gathering dust if you want to go down that route of omnidirectional, not mine btw.

Cardioid speakers I have mixed experience of the Dutch Dutch speakers when I heard them they were disappointing, didn’t do anything for me. However the owner can contour the voicing, so it could have been adjusted to sound like a Naim system :(
When I played with the Orelino concept http://www.goodsoundclub.com/Forums/Sho ... 9794#19794 ( I think Western Electric did it first) I liked the midbass that the 2 x 15” bass drivers gave. Not a lot of bottom end below 60Hz. I played with adding stuffing to the to tame the back wave. I would think with something like 3 Beyma 12BR70 per side it would sound impressive. You could try with the Tone Tubbies one channel, with some flat panel wave guides to get an idea, before making more wave guides. :)

This set up was what I borrowed your tapped horn for to try and fill the bottom end for. It was pre DSP, the 10 milliseconds of delay from the tapped horns I think is why it didn’t gel. With a DSP it would be a lot easier to integrate the tapped horn.
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#2714 Re: Something stirs in the Undergrowth

Post by IslandPink »

I don't even think I need to delay the tapped horn, Steve - I'm going to try out having the taped horn off to the side, but closer to me. Might work Ok at sub-100Hz.
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#2715 Re: Something stirs in the Undergrowth

Post by vinylnvalves »

I looking at the last page or so. I think I am not keeping up with this thread too well, I may have missed a couple of years :D . So upto 100Hz is covered by the tapped horn. 700 Hz and above is covered by the horns and the top end is covered by the ribbon or am I missing something. The latest horn was meant to cover this mid bass octave? Why are you talking about using Fostex drivers when you have the Supravox driver which covers that frequency band perfectly? The only thing is it doesn’t want to be on to be close to the floor as you don’t need the reinforcement off the floor if using the tapped horn.
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