Making speakers

Hi all. Look for some advice on speakers.
I use naim sbl with my seca amp and have found them bass light. As I put on a different pair of kef and the bass is much better but I think they lack in the mid.

I have a massive pair of transmission line from where I used to live but are to big for the room. I'd like to make a pair of floor or stand mount speakers with the units out off the transmission line.
Witch are kef b139 and a peerless mid and an addax tweeter.

Your thoughts please.


  • It would be a daring project, speaker design is quite complex.
    I'm surprised you find the SBLs bass light, they're certainly not rumblers but light?

    MkI or MKII bass driver?
    Yours from new or 2nd hand? (wondering about set up)
    Maybe you could experiment on placement within your room, all the usuall parameters except; must be against a solid wall.
    Improving on the standard Xover can also bring surprising dividends.
  • There are mrk2. Haven't had them from new. Have them close to a wall as it says. Using the standard crossovers. But to have better ones made it would cost alot.

    I would say the bass is there but is not very deep doesn't seem to go really low.
  • edited November 2015
    Naim claim down to 30Hz in room. They are fast and tight though. Certainly compared to a good TL they would seem a little anaemic.
    Having owned and installed many of these placement is really critical on them. Usually firing from the longer wall, if the room is not square. Not just "close" to the wall but as snug as you can get them, literally backs to the wall, as close as you can without actually touching, no toe in. In most rooms approx. 5.5' - 6' apart is the sweet spot. That wall must be solid, not partition etc.
    I do agree they do not dig deep though, I suppose it depends on what you are used to and how deep you want (not to be confused with quantity of bass).
    There is a chance that the bass driver box is not properly set up to the chamber below. That seal must be good and is easily compromised while moving the speakers. The spikes of said driver box must also rest on the small metal plates of the bass chamber, not pierce them.

    I found mine had sufficient bass even for movie watching. However, I do dislike booming or prominent bass so maybe just different preferences?
    edited November 2015
    30Hz in room is more than generated by most music you're likely to ever hear so it sounds like either a room issue (cancellation due to room modes or similar) or a speaker issue, or a speaker/amp matching issue.  They are sensitive to placement too, and as the advice above, work better close to rear walls than in free space.

    As CJ says, building speakers is a complex process, and anyone thinking of throwing a couple of drivers into a box and calculating a crossover for them is mostly in for big disappointment.  Most experiments along the DIY are doomed to failure I'm afraid  unless you know what you're doing.

    The B139 is a fine driver but you still need to know what sort of enclosure to use it in, and have the information to design and tune that enclosure for that drive unit.  Then there's the crossover.  You need to understand how high you can run the bass unit, then understand the electro-acoustic response in the chosen (prototyped) enclosure before you can accurately establish the electrical filter needed for the correct transfer function.  Then there's integration with the tweeter and phase matching.

    That all done, if it is a room mode causing the issue, then you'd be effectively wasting your time.

    Also, the crossover on the SBLs: it doesn't matter what upgrades you thrown at it in terms of posher components of the same value, they will not change the bass response.  

    There is also the question of the speaker/amp match.  I don't know what the amp specifications are but you need to be happy that their output is adequate to drive the SBLs properly.
  • Hi there.
    I understand what you are saying with building's very very difficult.
    It may be an amp speaker match problem.
    Colin made me the seca amp and what a brilliant job I love it. I was just surprised that I got more deep bass from a small speaker. And find the sbl's light. They were about deep when using a claymore.
    Don't no what to try. Would standing them on the carpet be better the slate.
  • Could a make or use a sub woofer.
  • FWIW I'm not a fan of subwoofers, although there are people here who like them.

    They never seem to integrate properly and usually mess up the timing of the main speakers.
  • I do agree with you on that one.
  • If not already tried, place them as close to a rear wall as you can.  What output is the SECA?  Whilst the SBLs are rated at 88dB/1W and nominal 6 ohm load, it's likely they drop lower in impedance.  I haven't seen the impedance curve for SBLs but when speakers are rated, most manufacturers normally rate them at the average resistive load somewhere in the lower mids which can be pretty meaningless when amp matching.  If this is the case with the SBLs they may well dip to 4 ohms or less in the bass needing  a fair few more watts up them to generate the 88dB.  Also, the 88 figure may be tight to wall placing.  Pull them into the room, and at lower frequencies below baffle step, you'll find they probably drop to more like 82dB.
  • There are close to the wall bit sat on slate at the mo. I belive the amp is 25 or 27 in to 8ohms.

    Can the crossovers be change to help this?
  • jsm, are you saying you had more bass from the SBLs when using the Claymore that you get with the SECA? If yes, did anything else change, cables, speakers moved etc?

    It's the crossover on these that give them the 6ohm rating, the drivers are 8ohm which is what the amps in an active system would see. As PAC said this dips in real usage.

    When you purchased them were they re-set up properly (by you or by a dealer) or did you use them as they came?

    I'm trying to narrow down a problem in the set up as I have also had a 15w Aclass amp (not SECA) replace a Claymore and I was both delighted and impressed with the resulting sound so am having problems thinking your problem is a simple mismatch.
    If you do try standing them on the carpet be sure the spikes pierce to the floor below with the frame of the speakers just clear of the carpet.
  • How big are the drivers in the SBLs Justin...?
    In general, I've found that in general one needs large drivers to plumn the depths. Paul (RFC) seems to find ways around this with some of his designs, but outside of RFC towers, it's what I've generally found.
    The SECA certainly goes low. I was impressed by how low it went with Colin's own standmounts, but we both remarked about how, on some tracks with deep / low bass the speakers simply couldn't do the SECA justice. At home with my old Goodmans (10/12 inch bass drivers) the SECA's bass came through far more impactfully.
    In addition, I'll put up my hand here and say that I do have a subwoofer (built around an old 18 inch Goodmans driver in a huge sealed cab). Which is a bit silly as a SECA into large floorstanders is plenty for most tracks. The sub is something that I feel ambivalent about. On the positive side, I listen to a lot of dub and electro where deep deep bass is almost the whole point of the track. With the sub turned on I realise how subconsciously used I am (without the sub) to the lowest notes slightly fading away. It is an absolute delight with the sub turned on to have the volume of bass lines maintained throughout. Keith Hudson's "Blood Brother" on the "Pick a Dub" album is a good example of this. The lowest notes of the bass line are utterly incredible with the sub turned on. They don't budge an inch. Impossible not to smile and rub one's hand with excited glee.
    On the downside, what people are saying about the timing is true. Or rather, I found it hard to get the timing right(ish). Before I introduced my sub I did a bit of reading (most of it beyond me). A few times I came across the notion that to work a sub into a system it is helpful if it is closer to the listening position than the main speakers, in order to reduce the likelihood of the wave from the sub from already being "behind" the wave form the main speakers before one starts to adjust the phase control on the sub amp. Most sub amps have a continuous "phase" control (0-180 degrees) which I think basically delays the signal to the set degree, in order to avoid the sound waves from the sub bring out of phase from the equivalent sound waves coming from the main speakers. The problem is that (obviously(?)) the phase control can only delay the signal from the subwoofer (it can't bring it forward (unless it contains time-travel circuitry). If the signal is already "behind" that from the main speakers (eg due to potentially longer / more convoluted signal paths in the sub pre- and power- amp) bringing the wave subjectively "in phase" may actually be  resulting in the delaying of the overall note longer, and so messing with the timing further.
    Sometimes I think I hear that a bit, even though the sub is tucked right behind my sofa. However, in my case the sub really is filling in the absolute lowest registers (probably picking to pick up things from about 40Hz down), so if there is a slight timing issue it's neither pronounced nor frequent. Also the amp I stuck in the sub is a fairly cheap one (good enough), so it maybe that the *quality* of the bass isn't as good as that coming out the mains.
    Actually, for me the greater issue when fine tuning the sub was its physical position relative to my usual listening position. It took ages, but I'm happy with it now.
    In any event, I don't have the sub on all the time. Only on tracks in which the deep bass is an integral part of the overall story.
  • Did the cone test they seem to have a good seal. Just wondering if I have the bottoms with the right bass. I will try tomorrow with them close a on the carpet.

    How do you make them active.
    edited November 2015
    Hi Justin.  In response to your earlier question, crossover mods to raise impedance can be done but it's not the way to go as it would be at the expense of efficiency.  The nominal load of the SBLs having now checked is not 8 Ohms but 6 Ohms.  Whilst a 25w amp should drive them to acceptable levels, it is never going to grip them in the bass as a more powerful amplifier.  I know that low powered amps, especially single ended designs have their fans, but on some speakers you really do need more juice to get things moving and it could simply be a case of the impedance curve dipping below nominal quoted impedance in the lower registers.  I have tested a large 3 way design here in recent months which the makers claimed was an 8 ohm load.  It actually tested at 2.8Ohms where it mattered, between lower bass and woofer crossover region and that would have had a serious impact on any driving amp not adequately rated for that load.  In that case, I did modify the design but it was needed anyway for other reasons and the customer ended up with a nominally flat 6 ohm load.

    I should add, that going active will not solve your problems either if a more powerful amp doesn't do the trick.  Beg or borrow an amp with at least 3 or 4 times the rated output power and try that before doing anything else.  It will likely decide one way or the other the resolution (amp or speakers).

    It is the only sensible advice in this case (all other things like drive units and amps being healthy)  given that you've already said the room itself is likely not to be the issue (ie you can get bass from other speakers/amps).

    I would not recommend going the sub route if you can avoid it.  More power needed (unless you buy active) and phase/SPL matching can be very challenging to get right.
  • Thank you for that and I do agree with you I belive it is the amp and speaker match. So looks like il be looking for new speakers.
    As I don't realy want to sell the amp Colin as just made for me. :(
  • I'm biased, but a speaker swap is definitely the way I'd go.

    I'm not a fan of Naim gear generally, but I've always thought Naim speakers were happiest on the end of Naim amps.

    It's a shame Colin's not around as he has some history with Naim and might have some thoughts to add on amp/speaker matching here.
  • edited November 2015
    I only mentioned active for its difference on resistance. It would involve a second power amp, either identical or of the same gain rating, plus an active cross over network. Although the SBLs were designed for active running (the passive xovers are just basic affairs to get you going) and sound better that way, it would certainly not cure what you are experiencing.

    As I have no experince of solid state single ended I can't agree or disgaree with PAC's comments on compatability with your speakers, I can only repeat that my Aclass 15w (not single ended) worked beautifully on them.

    On the bright side you'll have no trouble selling them, they are sought after second hand and being second hand to you originally you'll probably not lose out financially either.

    UG, I share your non-fan status of Naim equipment in general but made an exception for the SBLs. They are now long gone, however. I run some smaller stand mounts at the moment.

    I hope Colin's out and at them soon. I see John Farlowe (founder of Exposure) now also works with Naim equipment (Naim Thailand) !
  • Sorry... Chews thread tangent coming up!

    I run small stand mounts, of course, but sometime in the distant future want to try some floor standers in my rather live room. I'm not sure how they'll go, but it'll be fun to try them out.

    John Farlowe Exposures... I had a mate who worshipped them.
  • I haven't spoken to Colin for a couple of days hope he's ok.
  • He wasn't feeling too well on Friday.

    I've tried to contact him today, but haven't had any luck.
    edited November 2015
    I agree with CJ66 that SBLs almost always sound better when active driven.  Both Linn and Naim only offered rudimentary passive crossover set ups with their active designs, but whilst active will address grip, damping factor issues,  lower out of band distortion and improve fthe shape of the frequency response, if a gutsy SS amp can't deliver bass on the passive set up, then going active is less likely to do the same for obvious reasons.  I never really gelled with any speaker from Linn or from Naim and never considered loudspeakers to be their forte (being kind!).  The SBL though was a pretty decent attempt and a fine loudspeaker when correctly partnered.

    Hope Cols ok too, perhaps anyone who manages to get hold of him could let us all know?
  • Well I did message him and he just sent one back say he's not feeling good.
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