SpeakerTalk Forum Index SpeakerTalk
This forum has been set up to facilitate discussion of 1970s KEF speakers and drive units. The owner of the Forum has no connection with KEF Audio.
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Increasing a sealed enclosure's volume
Goto page 1, 2  Next
 
Post new topic   Reply to topic    SpeakerTalk Forum Index -> DIY with KEF drive units
View previous topic :: View next topic  
Author Message
Lee in Montreal
Senior Contributor 200+


Joined: 22 Aug 2009
Posts: 203

PostPosted: Fri Oct 09, 2009 10:23 pm    Post subject: Increasing a sealed enclosure's volume Reply with quote

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.


Last edited by Lee in Montreal on Sat Oct 10, 2009 7:23 pm; edited 1 time in total
Back to top
View user's profile Send private message
T.O. Chef
Senior Contributor 100+


Joined: 31 Aug 2007
Posts: 179
Location: Toronto Canada

PostPosted: Sat Oct 10, 2009 4:51 pm    Post subject: Reply with quote

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?
_________________
Music is food for the soul.
Back to top
View user's profile Send private message Send e-mail
SaSi
Senior Contributor 200+


Joined: 24 Aug 2008
Posts: 236

PostPosted: Sat Oct 10, 2009 6:46 pm    Post subject: Reply with quote

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.
Back to top
View user's profile Send private message
Lee in Montreal
Senior Contributor 200+


Joined: 22 Aug 2009
Posts: 203

PostPosted: Sat Oct 10, 2009 7:36 pm    Post subject: Reply with quote

T.O. Chef wrote:
Personally, I would never modify a properly working pair of original 105 II's.


I am with you on that. Which is why one set will stay as original as it left the factory, while the second set (the Franken Kef) will be the subject of an experiment. I am leaning toward a 4th order band pass enclosure. Same principle as the 107 and 104 (even though they are also Isobaric, having twin bass drivers).

This way, the main enclosure stays a sealed one (as in any original 105), but the baffling allows for a selection of the frequencies. Putting the B300 flat horizontal also means I won't have to turn it 120 degrees every year.

Don't get me wrong. The set I am listening to at the moment is very, very nicely balanced and rewarding. It is flat as Utah's Salt Lakes. But I am still looking for that hit in the chest from Dead Can Dance's timpanis or from a low organ key.
Back to top
View user's profile Send private message
ColinR
Über Contributor 1000+


Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire

PostPosted: Sat Oct 10, 2009 7:46 pm    Post subject: Reply with quote

Any offers of plans for the B300B, B110B, T52B Skyline, Klang+Ton 10-11 1987 Very Happy Question
_________________
This post or any other information supplied to this website or any other by myself is not available for any form of commercial purpose i.e. to hi-fi magazines or as sales and marketing material for sleezeBay or Audiodogging pimps and the like.


Last edited by ColinR on Sat Oct 10, 2009 8:37 pm; edited 1 time in total
Back to top
View user's profile Send private message
Lee in Montreal
Senior Contributor 200+


Joined: 22 Aug 2009
Posts: 203

PostPosted: Sat Oct 10, 2009 8:11 pm    Post subject: Reply with quote

ColinR wrote:
Any offers of plans for the B300B, B110B, T52B Skyline Very Happy Question


Currently working on this: B300, B110 and T33 without the plastic fascia.

For now, it remains a sealed enclosure but with 50% more volume than a stock 105. Mega bracing and extra thick wall for best stiffness. Except for the top and bottom, there's no parallel facing walls.

Back to top
View user's profile Send private message
speakerguru
Über Contributor 1000+


Joined: 18 Nov 2005
Posts: 1007
Location: Green Hut, Tovil

PostPosted: Sun Oct 11, 2009 9:41 pm    Post subject: Reply with quote

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.
Back to top
View user's profile Send private message
Lee in Montreal
Senior Contributor 200+


Joined: 22 Aug 2009
Posts: 203

PostPosted: Sun Oct 11, 2009 10:01 pm    Post subject: Reply with quote

speakerguru wrote:
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.


Hmm... I guess I will stick with the maximum "allowed" internal volume which is 75 litres. Thanks for the advice.

Lee
Back to top
View user's profile Send private message
speakerguru
Über Contributor 1000+


Joined: 18 Nov 2005
Posts: 1007
Location: Green Hut, Tovil

PostPosted: Mon Oct 12, 2009 8:37 am    Post subject: Reply with quote

Lee in Montreal wrote:
Hmm... I guess I will stick with the maximum "allowed" internal volume which is 75 litres. Thanks for the advice. Lee


On the other hand, the low frequency alignment of most designs is quite tolerant of changes in box volume up to 20% or so. KEF would often go for the slightly smaller option for aesthetic reasons. I designed the B300 SP1060 for the original 105. I seem to recall that ideally the box volume should have theoretically been 80 to 90 litres. However, using 70 or 75 litres made very little difference but was a lot more acceptable domestically. Remember that changes to box and port resonance frequencies are proportional to the square root of any changes in volume. If in doubt, use a simulator to check it out before you build.

BTW, I really like the look of your rounded cabs. Go for it!
Back to top
View user's profile Send private message
Lee in Montreal
Senior Contributor 200+


Joined: 22 Aug 2009
Posts: 203

PostPosted: Mon Oct 12, 2009 1:04 pm    Post subject: Reply with quote

speakerguru wrote:
I seem to recall that ideally the box volume should have theoretically been 80 to 90 litres. However, using 70 or 75 litres made very little difference but was a lot more acceptable domestically.


Hi SpeakerGuru.

This what exactly the type of information I was looking for when I asked what where the initial designs before the marketing guys came in. So, if the B300 was designed for an 80-90 ltre enclosure, then I will make one of that size.

Thanks again very much, you have no idea how I appreciate the input. It is a great honor to discuss with you.

Lee
Back to top
View user's profile Send private message
T.O. Chef
Senior Contributor 100+


Joined: 31 Aug 2007
Posts: 179
Location: Toronto Canada

PostPosted: Mon Oct 12, 2009 8:38 pm    Post subject: Reply with quote

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?
_________________
Music is food for the soul.
Back to top
View user's profile Send private message Send e-mail
speakerguru
Über Contributor 1000+


Joined: 18 Nov 2005
Posts: 1007
Location: Green Hut, Tovil

PostPosted: Tue Oct 13, 2009 8:14 am    Post subject: Reply with quote

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.
Back to top
View user's profile Send private message
T.O. Chef
Senior Contributor 100+


Joined: 31 Aug 2007
Posts: 179
Location: Toronto Canada

PostPosted: Tue Oct 13, 2009 10:03 pm    Post subject: Reply with quote

{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]
_________________
Music is food for the soul.
Back to top
View user's profile Send private message Send e-mail
T.O. Chef
Senior Contributor 100+


Joined: 31 Aug 2007
Posts: 179
Location: Toronto Canada

PostPosted: Wed Oct 14, 2009 12:34 am    Post subject: Reply with quote

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.
_________________
Music is food for the soul.
Back to top
View user's profile Send private message Send e-mail
Lee in Montreal
Senior Contributor 200+


Joined: 22 Aug 2009
Posts: 203

PostPosted: Wed Oct 14, 2009 1:58 am    Post subject: Reply with quote

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" ???)...
_________________
Kef Calinda - since 1979
Kef Cantata - since 2009
Kef 105/2 - since 2009
Evo 105/2 - in the build
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    SpeakerTalk Forum Index -> DIY with KEF drive units All times are GMT + 1 Hour
Goto page 1, 2  Next
Page 1 of 2

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group