Hello,
I have a KEFKIT 3 that I bought many years ago, it has never been assembled.
KEF's leaflet shows the cabinet dimensions, please see attachment. Front 15½, depth 11½ and height 29½ but the internal volume can be between 60 - 150 liters. The baffle dimensions are 28 x 14 x 10.25.
The drivers are B139 [13" x 9.25"]; B110 110mm and T27 108mm.
I have three questions: can I increase the depth of the cabinet and how do I calculate the correct internal volume between 60 and 150 liters or should I follow KEF's leaflet?
Thanks much in advance.
Kind regards,
Horacio
I have a KEFKIT 3 that I bought many years ago, it has never been assembled.
KEF's leaflet shows the cabinet dimensions, please see attachment. Front 15½, depth 11½ and height 29½ but the internal volume can be between 60 - 150 liters. The baffle dimensions are 28 x 14 x 10.25.
The drivers are B139 [13" x 9.25"]; B110 110mm and T27 108mm.
I have three questions: can I increase the depth of the cabinet and how do I calculate the correct internal volume between 60 and 150 liters or should I follow KEF's leaflet?
Thanks much in advance.
Kind regards,
Horacio
Attachments
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Do you still have the cabinet plans the leaflet says are included with the kit? From what I see there is some info that needs clarification. There is no mention of changing the port length if the volume is increased beyond the minimum recommendation in the leaflet. Also, the leaflet drawing appears to show separate enclosures for the midrange and tweeters but they may be horizontal brace locations instead since the minimum dimensions total about 65 liters.
29-1/2” is a bit short for a floorstander, IMO. Rather than make the cabinet deeper I’d make it taller or angle it back a few degrees or put it on a stand to get the midrange/tweeter area closer to listening height. If you do increase the volume I’d keep to the Golden Ratio as much as possible. I’m sure others will chime in with different recommendations.
29-1/2” is a bit short for a floorstander, IMO. Rather than make the cabinet deeper I’d make it taller or angle it back a few degrees or put it on a stand to get the midrange/tweeter area closer to listening height. If you do increase the volume I’d keep to the Golden Ratio as much as possible. I’m sure others will chime in with different recommendations.
Wow that's a blast from the past,when I was a poor engineering student I bought a pair of the kit 2's a B139 and T15,my mate who had a bit more cash bought the Kit3.I put mine in a 60Ltd fully stuffed sealed box with lots of stiffening,he built a larger vented box for his,forget the volume but bigger than mine.The B139 is still a class act even today and my sealed box was way better than his,much better bass detail and clarity.The B139 works best sealed in my view and if you use many of the free available box calculators you can tune it to your room position, i.e. free field Q of about 0.7 or close to the wall Q of 0.55 to 6.
This kit in a sealed enclosure as shown is completely fair if you care not for further bass enhancement. Otherwise you should follow Kef's note on increasing the volume to a maximum of about 150 litres vented keeping in mind the presumption of TS parameters being the same, Fs=25 Hz; Qts=0.37 and Vas=130-150 litres. The vent measures can easily be calculated. Still, if you would like to be totally certain, a set of two impedance measurements may be worthwhile for a fresh TS parameters evaluation. I would increase the height and depth to accomodate new vented enclosure volume requirement. Ultimatelly all drive units are best to be evaluated for their electrical and acoustical specifications to ensure the satifactory performance as originally foreseen. Midrange unit is to be in its own smaller enclosure.
Scans of original instructions and sales material on this page - KEF CONCERTO or KEFKIT 3
Very neat project!
Instructions suggest increasing depth for more bass.
Very neat project!
Instructions suggest increasing depth for more bass.
I agree with this. I made a pair of KEF CS7 speakers donkey's years ago, they are still in use and have excellent bass. They have a B139 in a sealed enclosure, plus B110 in its own sealed sub-enclosure, and a T33A tweeter.
My experience suggests a Q of 0.5 gives the most natural bass in a room.
You'll need to close the back of the midrange tube if it doesn't touch the back wall. Or extend the tube. Regardless, it needs to be sealed up so the woofer doesn't push it around.
EDIT: Looked at the photo more closely... it's already sealed. 🙂 🙂 🙂
EDIT: Looked at the photo more closely... it's already sealed. 🙂 🙂 🙂
And shows how to add a wooden block to the rear of the midrange tube in order that it can be supported by the back of a deeper cabinet.
The simplest approach would obviously be to complete the kit as intended - in a 65 litre enclosure.
Extending the bass response by utilising a larger volume may, or may not, suit the size of your listening room and/or the intended positioning of the speakers within the room.
The 65 litre volume may be considered a safe bet!
The XO is the weakest part of this kit. The simplest, and likely best recommended box is the sealed one. I would abandon the included baffle and look to build a modern TL and at least bi-amp.
dave
dave
Here the DN12 XO used in the KETKit 3:
If you were to bi-amp you could use the later AB XO on the tweeter and biamp the B139/B110 below 250 Hz (making the nasty 1kHz resonance less of an issue):
Me, i’d biamp and substitute something like the Alpair 5.2eN for the b110/T27.
http://p10hifi.net/TLS/downloads/B139-TTL-map-100707.pdf
The A5.2 could be housed an a 4” piece of PVC pipe out the back (midTL)
dave
If you were to bi-amp you could use the later AB XO on the tweeter and biamp the B139/B110 below 250 Hz (making the nasty 1kHz resonance less of an issue):
Me, i’d biamp and substitute something like the Alpair 5.2eN for the b110/T27.
http://p10hifi.net/TLS/downloads/B139-TTL-map-100707.pdf
The A5.2 could be housed an a 4” piece of PVC pipe out the back (midTL)
dave
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I think that Galu is correct, I'll build the complete kit as intended but I'll use the new Falcon Acoustics - I bought my first kit from them in 1977 - crossover No.33Mc. with the MF & HF upgrade super version. This xover can be used in the Concerto too.
Crossovers, Networks, Filters, LS3/5a, KEF, RAM, Celef from Falcon Acoustics.
Crossovers, Networks, Filters, LS3/5a, KEF, RAM, Celef from Falcon Acoustics.
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Dave,
I have read a review of the LS3/5a "the cult of a little legend" in the Absolute Sound that the achilles hill of this monitor is the hump around the 125Hz.
The KK 3 uses the same B110 and T27, I am not sure if this problem exists in the KK 3 or if Falcon redesigned crossover solved this problem.
Excerpts from the review:
"This owes in part to what is often affectionately referred to as the “hump,” a substantial rise in the vicinity of 125Hz to give the impression there’s more bass than there is. I noticed that in at least one published set of measurements, there is quite a mountain around this frequency, about 5dB at its peak, which makes it as high as the 125Hz hump. This would account for the edginess—though perhaps a better description might be shoutiness in the presence region—and for the greater nasality. It would also account for why the midrange proper sounds slightly recessed, as the ear apparently keys onto the rises at 125Hz and 1000Hz". "And because the hump is a hump—as opposed, say, to a broad rise with a smooth roll-off—it not only can’t be ameliorated with careful tone-control correction".
Please see link below.
What's your opinion. By the way I have been using a pair of fully updated and upgraded ESL63 for a while.
Falcon Acoustics BBC LS3/5a | The Absolute Sound
Kind regards,
Horacio
I have read a review of the LS3/5a "the cult of a little legend" in the Absolute Sound that the achilles hill of this monitor is the hump around the 125Hz.
The KK 3 uses the same B110 and T27, I am not sure if this problem exists in the KK 3 or if Falcon redesigned crossover solved this problem.
Excerpts from the review:
"This owes in part to what is often affectionately referred to as the “hump,” a substantial rise in the vicinity of 125Hz to give the impression there’s more bass than there is. I noticed that in at least one published set of measurements, there is quite a mountain around this frequency, about 5dB at its peak, which makes it as high as the 125Hz hump. This would account for the edginess—though perhaps a better description might be shoutiness in the presence region—and for the greater nasality. It would also account for why the midrange proper sounds slightly recessed, as the ear apparently keys onto the rises at 125Hz and 1000Hz". "And because the hump is a hump—as opposed, say, to a broad rise with a smooth roll-off—it not only can’t be ameliorated with careful tone-control correction".
Please see link below.
What's your opinion. By the way I have been using a pair of fully updated and upgraded ESL63 for a while.
Falcon Acoustics BBC LS3/5a | The Absolute Sound
Kind regards,
Horacio
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Hi again Horacio!
If your ears have become attuned to the open sound of an elecrostatic loudspeaker then you'll quickly perceive the limitations of any box speaker in terms of its 'boxy' resonances!
The LS3/5a has no low bass to speak of and that is why the 125Hz hump is engineered into the design in order to give the impression of it having low bass.
No such hump will have been engineered into the KK3 as it has a greater bass extension and so no need for such artificial boosting.
Thank you for your note, very interesting.
I am aware of this kit's limitations but I am retired and bored, I cannot heat a seat for more than ten minutes so I need activity when I am at home. That's why I want to build the kit.
I have had quite a few loudspeakers, Mission 770, B&W DM6, Goldmund Super Dialogs, Tannoy silvers, reds and HPD 385, three pairs of ESL 63 - not at the same time - Proac, Tangent, Spendor BC1, Aerial 10T, Kelly ribbons and a pair of B&W DM 70 but in the end I went back to QUAD.
The ESL63 are superb speakers for chamber and baroque but Wagner... I have the 1955 live recording of Keilberth's Der Ring at Bayreuth, the 63's don't do it justice... the dynamic range is astounding!
Cheers,
Horacio
I am aware of this kit's limitations but I am retired and bored, I cannot heat a seat for more than ten minutes so I need activity when I am at home. That's why I want to build the kit.
I have had quite a few loudspeakers, Mission 770, B&W DM6, Goldmund Super Dialogs, Tannoy silvers, reds and HPD 385, three pairs of ESL 63 - not at the same time - Proac, Tangent, Spendor BC1, Aerial 10T, Kelly ribbons and a pair of B&W DM 70 but in the end I went back to QUAD.
The ESL63 are superb speakers for chamber and baroque but Wagner... I have the 1955 live recording of Keilberth's Der Ring at Bayreuth, the 63's don't do it justice... the dynamic range is astounding!
Cheers,
Horacio
Treat the KEFKIT 3 simply as a fun project then. You will have heard better speakers - and perhaps some that are worse! 🙂