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#181 Re: Another speaker thread

Posted: Sat Feb 06, 2021 2:53 pm
by steve s
Nick wrote: Sat Feb 06, 2021 2:42 pm Yes it does. But quality in terms of a resonant system. No other implied meaning.
Yes I see that nick, thanks

#182 Re: Another speaker thread

Posted: Sat Feb 06, 2021 7:39 pm
by Scottmoose
You may find this interesting: http://web.archive.org/web/200809291142 ... Box-Q.html It's nominally in reference to sealed box systems, but you can simply replace 'Qtc' with '[effective] Qts' & apply to drive units.

#183 Re: Another speaker thread

Posted: Sun Feb 07, 2021 12:03 am
by steve s
Scottmoose wrote: Sat Feb 06, 2021 7:39 pm You may find this interesting: http://web.archive.org/web/200809291142 ... Box-Q.html It's nominally in reference to sealed box systems, but you can simply replace 'Qtc' with '[effective] Qts' & apply to drive units.
Thanks scott, that's interesting, page two being particularly informative.

Its also discussing system q, which I know is the important aspect rather than driver q.
Cheers..

#184 Re: Another speaker thread

Posted: Sun Feb 07, 2021 8:50 am
by Scottmoose
It is if you're building a sealed box, which was primarily what John was discussing; it doesn't really apply for vented etc. alignments (although keeping in mind the latter are 4th order systems you can extrapolate somewhat). However, for much of John's two pages, you can simply substitute 'Qts' for 'Qtc' if you're focusing purely on the drive unit, or using baffles that provide no effective air-mass loading or resonance. Just ensure it's effective Qts you use, i.e. Qts + any series R in circuit (either via loop resistance or amplifier output impedance).

#185 Re: Another speaker thread

Posted: Sat Feb 27, 2021 8:17 pm
by Ali Tait
Vic’s been fiddling again-

https://www.trans-fi.com/diy-speaker-blog

#186 Re: Another speaker thread

Posted: Sun Feb 28, 2021 10:20 am
by Ali Tait
Been emailing with Vic, thought this picture of the measurements of the last few FR drivers he's used was worth putting up. As he points out, it's interesting to note the break up above 2k from all the wide range drivers he's tried, until he got to the Gallos and KEF's with tweeters. the KEF's look to measure pretty well, a very good result given you can get a pair on ebay for a hundred quid. He's done a few mods to them, nothing drastic though.

The graphs do not show the UM18 output.


Image

#187 Re: Another speaker thread

Posted: Sun Feb 28, 2021 11:12 am
by Ant
I can remember mi dad having some of the original ones, kht 2001 i think about 20 years ago, a pair of the eggs and a sub.
I think the eggs stood on the window sill and the sub was somewhere out of the way
Always liked them, i always wondered what the uni q driver would have sounded like in a metronome. I had some q15 stand mounts which i really liked at the time

My q15 drivers ended up in a mates car parcel shelf. Wonder what happened to the kht eggs? The sub plate amp ended up in some open baffles with active bass drivers iirc

#188 Re: Another speaker thread

Posted: Sun Feb 28, 2021 11:13 am
by Scottmoose
Right. Wideband drive units use TL (aka 'breakup', aka 'resonant') modes to produce the majority of their bandwidth. As far as bald mathematics goes this is for frequencies up to a point defined by Sd; for frequencies above that however piston behaviour should continue up to acoustic diameter of the voice coil, after which it transitions to TL modes running through or over the diaphragm. In practice not usually so pat as the above assumes a flat piston & cone shape, materials, additional stiffening structures etc. modify this.

The KEF is a multiway; the individual drive units are sized & optimised for operation over narrower bandwidths; the object is to avoid TL modes altogether by rolling off the main cone in the crossover & handing over to the tweeter which should not exhibit any significant bell modes etc. until well above 20KHz. Most wideband drive units attempt a mechanical equivalent -for example decoupling the main cone & using a sub-cone like a whizzer or central dustcap bonded to the end of the voice coil to handle the higher frequency range, with varying levels of success.

#189 Re: Another speaker thread

Posted: Sun Feb 28, 2021 12:54 pm
by chris661
Just a quick FWIW that I have a pair of Kef HTS3001SE on my desk (the SE versions have the "tangerine" phase plug). I sealed up the boxes and applied a big boost at 35Hz, plus a cut in the 150Hz range (probably the "chestiness" that Vic notes) and a couple of other response tweaks.

The results are excellent. Of course, they don't get loud before the 4.5" cones make unhappy sounds instead of bass. However, my listening distance is a couple of feet. I don't need loud. I just wanted a full-range point source.

For use at larger distances, I'm not surprised Vic doubled them up.

I'm very interested in Kef's more recent efforts, but all those square edges scream "diffraction" to me.

Chris

PS - Further to Scott's post, I generally prefer electrical crossovers to mechanical. The former is much easier to tweak and optimise.

#190 Re: Another speaker thread

Posted: Sun Feb 28, 2021 1:40 pm
by Ali Tait
He’s also only running them down to 200hz.

#191 Re: Another speaker thread

Posted: Sun Feb 28, 2021 3:20 pm
by Nick
Ali Tait wrote: Sun Feb 28, 2021 1:40 pm He’s also only running them down to 200hz.
Also, to be picky, the "Journey to No-Baffle Speaker System" has failed a bit given the two way Kef's are enclosed. He could have put a pair of LS3/5A's on the top.

#192 Re: Another speaker thread

Posted: Sun Feb 28, 2021 4:00 pm
by chris661
Ali Tait wrote: Sun Feb 28, 2021 1:40 pm He’s also only running them down to 200hz.
True, but a bump at 150Hz will pull the acoustic crossover down, resulting in overlap.


Something that might be interesting would be to apply some FIR processing to the Kef eggs. In theory, square waves on & off axis should be possible - they're coaxial, after all.

Chris

#193 Re: Another speaker thread

Posted: Sun Feb 28, 2021 4:30 pm
by Ali Tait
AFAIK he dropped the UM18’s to 120hz

#194 Re: Another speaker thread

Posted: Sun Feb 28, 2021 4:33 pm
by Ali Tait
Nick wrote: Sun Feb 28, 2021 3:20 pm
Ali Tait wrote: Sun Feb 28, 2021 1:40 pm He’s also only running them down to 200hz.
Also, to be picky, the "Journey to No-Baffle Speaker System" has failed a bit given the two way Kef's are enclosed. He could have put a pair of LS3/5A's on the top.
Yep, that was true with the Gallo too. Can’t say he didn’t give it a fair go though. :)

#195 Re: Another speaker thread

Posted: Sun Feb 28, 2021 5:34 pm
by Vangelo
Nick wrote: Sun Feb 28, 2021 3:20 pm
Ali Tait wrote: Sun Feb 28, 2021 1:40 pm He’s also only running them down to 200hz.
Also, to be picky, the "Journey to No-Baffle Speaker System" has failed a bit given the two way Kef's are enclosed. He could have put a pair of LS3/5A's on the top.
Yah....this is true Nick! I had no idea this is where I would end up (if its the final stop). I tried driver after driver trying to find one that didnt 'break up'.
I didnt realise the driver was the culprit thinking my system was so revealing it was showing up poor recordings.....so I didnt play stuff that sounded bad (most rock).

Then I took the departure to try something commercial. I tried to chose something in keeping with the 'no-baffle' theme, and something relatively efficient. Also, I was very afraid of choosing a box as I can always hear boxiness having used OB for so long. The Gallos fitted the bill!

Immediatley the break-up was gone, and I started playing my rock library which sounded great. So I knew I was on the right path. As you say, probably anything would work on top, altho I might have trouble driving the LS3.5A's.