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Lyndon Johnson 21st January 2017 12:22 PM

Kit speakers for 300B pp
I am considering building some small- medium sized floor standing speakers for my newly acquired 300B pp amp (being used with no feedback).
IPL and Wilmslow both seem to have suitable kits.
I am keen to hear from anyone who has used this amp with a currently available kit speaker . I know the WAD KLS3 was designed with this amp in mind but presumably the drive units are now obsolete?

Greg. 23rd January 2017 08:42 AM

Re: Kit speakers for 300B pp
Hello Lyndon,

If you did want to go for KLS3, all the drive units and crossover components are still available.

Falcon Acoustics can supply the tweeter and mid range units as well as all the crossover components.

The bass drivers can be obtained from here.

If you wanted to build the Mk2 versions, the gold tweeters are no longer available but the fabric dome unit as used in the Mk1 version can be used with an alteration to the crossover. See the FAQ here for detail on how to do this.

Lyndon Johnson 23rd January 2017 06:02 PM

Re: Kit speakers for 300B pp
That's great, thanks Greg. I still have all my old DIY supplements so I will get them out and read up. I will need to understand the differences between the mk1 and mk2 ........

Greg. 23rd January 2017 06:22 PM

Re: Kit speakers for 300B pp
When you read, be aware that the published Mk1 crossover design in the supplement was altered when the kit was released. I can send you the corrected schematic if you wish.

I've used these speakers for over twenty years and it is my view that the Mk2 crossover is the superior option. Obviously you would need to alter it to accommodate the tweeter that replaces the now unobtainable gold dome version, as per the FAQ here.

Good luck. If I can help further, just shout.

Lyndon Johnson 31st January 2017 08:40 PM

Re: Kit speakers for 300B pp
I'm still keen to hear comments from anyone who has used this amp with other kit designs, even better if they can offer a comparison with the KLP3.

Lyndon Johnson 25th February 2017 11:01 AM

Re: Kit speakers for 300B pp
I've re-read all my old DIY supplements now - all the way from 1993 to 2001 and I reckon I do indeed want to build myself a pair of KLS3's and maybe even go the whole hog and get the SEAS tweeters if still available.
I have a question though - the Mk2 has a rear facing reflex port but domestic reality means my speakers will be less than a foot from a wall. Is it advisable to make this forward facing and does anyone have experience of doing this with the single 'tuneable' port tube of the Mk 2 as opposed to the twin ports of the Mk 1?

Greg. 25th February 2017 10:21 PM

Re: Kit speakers for 300B pp
Lyndon, I can give you a fairly specific response as I have two pairs of KLS3's here. The Mk1 and the Mk3 gold with rear facing single port.

Back when I built Mk3, it was for use in a very large high ceilinged Victorian living room with the speakers located well into the room space and well away from any walls. They sounded great and a point of interest is that my son and I could detect very little difference when rear port tuning, i.e. Shortening or lengthening the rear port. They sounded great whatever the setting.

I now have these speakers back for my own use. Having sorted out the tweeter failure problem (see FAQ's) I have trialled them in my 4m x 5m listening room. Here, the speakers can be no more than 18 inches from the wall behind them. On trial with rear ports, there was a massively sloppy bass bloom which completely swamped the sound and was terrible. As I know the Mk1 version with front firing ports work well, I am now progressing to converting the Mk3's to also have the front ports.

I have never listened to these speakers fitted with the single port at the front so can't comment on that. The single ports that came with the kit are screw fixed with an ugly flange, so for front baffle fitting, something more elegant would be needed. As I know the twin port version works, I'm going with that. Obviously, I am dealing with previously built veneered speakers, so I can't afford to make any mistake cutting into the front baffle, therfore, I am converting the Mk3's to twin ports. I'd love to experiment with a single front port, but cannot afford to take the risk as in the event of failure or dissatisfaction, the baffle would be ruined.

To do this it then gets more interesting because the original 40mm O.D ports originally used are no longer available anywhere, or at least not within my search ability. If you manage to find any, please let me know. Noel Keywood in one of the articles commented that 35mm ports could be used and specified the length, but I have not been able to find any that suit my personal taste. The twin version ports also have a I.D. Of 37mm (wall thickness 1.5mm). I searched long and hard for this and could find no suitable tube in plastic. However, I did turn up some Stainless Steel tube and have bought a metre as I also have a friend who wants to do this conversion as well.

The tubing is now with me. I now need to get it cut into 85mm lengths, cut absolutely square and cleanly finished. I am currently looking for a small local engineering works that'll take on the task.

I hope this is useful. Please come back if you in your planning find out anything that could be useful for me or others. We'd much appreciate that.

Now sending you a PM.

Lyndon Johnson 10th March 2017 04:05 PM

Re: Kit speakers for 300B pp
Thanks for this Greg,
I know it affects the sound but I always keep the front grilles on my speakers so the appearance of the port tubes might not be so critical. I might look out for cardboard tubes of 38mm ID which I think sometimes get used in the packaging industry, which is where I work.
I have done myself a cardboard mock-up of the cabinet and concluded that 1000mm high is going to be domestically unacceptable but that I might get away with 920-950mm high. I propose to increase the depth from 350mm to 370mm in order to retain the same cabinet volume. I have seen no mention of cabinet depth being critical to sound quality- is that your understanding too or am I committing a sin?

Chris 11th March 2017 08:25 AM

Re: Kit speakers for 300B pp
Hi Lyndon, I have the KLS10's with the seas millenium tweeter and a Audax Bass/Mid driver and have no plans to look for anything to replace them. So I can understand Greg's personal attachment to the KLS3's.

The sound will change regarding the volume size, but making bigger you can always add a block of wood inside the cabinet to reduce the volume, as suggested in the KLS10's build..which did encourage the builder to experiment, with the volume size, port size, using straws in the port, etc.

The removal of the crossover will increase the volume size, which I plan to try over the next few weeks. (external crossover)

If possible I would use a router to cut in the drivers..I made a template using 6mm ply, using a router bush guide makes a perfect fit.


Lyndon Johnson 11th March 2017 10:31 AM

Re: Kit speakers for 300B pp
Thanks Chris,
With my last speakers I flushed the drivers in by cutting the outer faceplate size out of 3mm ply then glueing it to the front baffle 'in register' with the cut-outs. Thus avoiding routing. The front baffle is then 28mm thick of course.
I too plan to have the crossovers outside, though I must admit I hadn't planned for that influencing the effective volume

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