SpeakerTalk

Lee in Montreal · Senior Contributor 200+ Joined: 22 Aug 2009 Posts: 231

How would increasing the volume of an 105/2 enclosure affect the lower frequency of the system? Would it help the woofer reach its free air resonance frequency? Or is the woofer "electronically locked" at 40Hz by the big caps at the entry of the filters.

Per exemple the the B300 is rated at 23Hz (plus or minus 5Hz) while the 105/2 system rolls off at around 38Hz.

And one other thought I had and should be best asked to peoples having worked on designing the 105/2, is that only one design made it to production. The one we could buy and that was destined for residential or studio use. But what about all the other drafts that perhaps were better sounding? The "other" projects that never made it to production because the marketing guys thought it was too big to fit a living room, or that got canned by the accountants because it was too costly to produce...

Any design ideas we can use to make an improved 105/2?
Larger cabinet? Taller? Deeper? More bracing? Better shape to avoid standing waves?

Just thinking out loud.

T.O. Chef · Posted: Sat Oct 10, 2009 4:51 pm Post subject:

And another out loud thought or 2 ... starting with: is the B-300 suited to a TL (or variant) design?

Getting deeper and tighter bass from the 105 II seems to be an often expressed wish of contributors and owners posting to other threads.

Personally, I would never modify a properly working pair of original 105 II's. They are wonderful just as designed. But as a hobbyist I can't contain my curiosity as to how different bass loading would / could be done either with the B-300 or a B-139 or even a B-200.

TL, Isobaric, Reflex ???? Anyone?
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SaSi · Senior Contributor 200+ Joined: 24 Aug 2008 Posts: 256

ME!

I have 4 B300 from the constructor series, several different B200 variants in numbers and more B139 than I care to use. Let alone PRs.

And a workshop to build some test enclosures.

My first project will be just that. Build a test enclosure of about 150lt, and mount a B300 or 2 B300s back to back and in isobaric. I am planning to work with different enclosure volumes by placing 1.5lt bottles filled with sand inside.

I have a pair of CS1 like satelites, so I can easily test drive a single enclosure with listening tests.

Lee in Montreal · Senior Contributor 200+ Joined: 22 Aug 2009 Posts: 231

ColinR · Posted: Sat Oct 10, 2009 7:46 pm Post subject:

Any offers of plans for the B300B, B110B, T52B Skyline, Klang+Ton 10-11 1987 Very Happy

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Lee in Montreal · Senior Contributor 200+ Joined: 22 Aug 2009 Posts: 231

speakerguru · Posted: Sun Oct 11, 2009 9:41 pm Post subject:

KEF made their own drivers, so box and driver were pretty well optimised for each other in each design.

If you increase the box volume you're making it easier to run out of driver excursion with less amplifier power. The spl at any given frequency is limited by the volume dispacement capability of the driver's moving parts. If you want lower, louder bass you will need more box volume and more drivers. You have to pump a lot of air from a big resevoir. Just look at a Tuba player compared to a trumpet player.

If you're unhappy with the sound or quality of the bass you'll most likely have to look at the room construction and acoustics.

Lee in Montreal · Senior Contributor 200+ Joined: 22 Aug 2009 Posts: 231

speakerguru · Posted: Mon Oct 12, 2009 8:37 am Post subject:

Lee in Montreal · Senior Contributor 200+ Joined: 22 Aug 2009 Posts: 231

T.O. Chef · Posted: Mon Oct 12, 2009 8:38 pm Post subject:

Fascinating stuff Lee, Speakerguru.
Now, I wonder just how that correction circuitry in the 105 II is sonically tied into the crossover design?

As Lee's 105 heads have had the protection boards removed, could he expect the same sonic results if using an original 105 crossover without that circuit in place and wiring the B-110 / T-52 directly to the main crossover board?
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speakerguru · Posted: Tue Oct 13, 2009 8:14 am Post subject:

Not sure what you mean by "sonically tied". The protection circuit is related to to the thermal characteristics of the voice coils. It is an analogue model of the three vc thermal time constants. The trip point is reached if any of the units gets too large a voltage for too long a period. This corresponds to the voice coil maximim safe operating temperature being reached. The protection circuit has no effect on the crossover filters or eq.

T.O. Chef · Posted: Tue Oct 13, 2009 10:03 pm Post subject:

{The protection circuit has no effect on the crossover filters or eq.}

I could / should have worded that question better but you have answered it perfectly Speakerguru. That's what I wondered about .. if the mid and HF signal from the main crossover has further EQ or filtering applied in the protection circuit.

The reason I ask is that in experimenting with replacing capacitors on a 105 II filter using Solen's / Bennic's I found the tonal character drastically altered.
This was surprising, as the same treatment to 2 pairs Cantata's has yielded superb results. Same B-110 / T-52. I suspected interaction with protection circuit was to account for the difference.

I know we've strayed a bit off topic here, but any thoughts on other differences that may account for these findings?[/img]
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T.O. Chef · Posted: Wed Oct 14, 2009 12:34 am Post subject:

Well Sasi, if you have more B-139 SP 1044's than you'll ever need, and would like to see 2 of them go to very good use feel free to IM me to discuss.
My 4 units show more than their age Sad

Plan: B-139's in a TL cabinet with B-110 sp1057 & T-52 sp1072 in separate head enclosures ala R105. Cantata crossover. Get the line right and I think it's a winner design. (Sorry, don't mean to offend any contributors here).

All other bits are collected, tested, and ready.
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Lee in Montreal · Senior Contributor 200+ Joined: 22 Aug 2009 Posts: 231

Hi Robert

If you make a TL speaker, most likely, it will be about 1.5m tall. In this case, if you put some 105/2 style heads on top of them, then you'll need to grab a scaffold to seat on to be at the heads' height. I am not kidding.

Most likely (and that is what I did back then) you will locate the B139 on top, and the mid/hi drivers below.

To make a shorter cabinet, it will need to be very deep, and to fold the TL four or five times. But it is posible. The cabinet will most likley be 24" deep, which is not that bad if the whole cabinet is not too tall (40" ???)...
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Current line up
2 sets basic Kef 104/2
2 sets bi-wire Kef 104/2
Plenty of KEF components for a few fun builds