dloper

IPL Acoustics S5TL

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I recently built a pair of IPL S5TL speakers and I've lived with them for a couple of months now. The build was straightforward although I took the cheaper option of cutting the cabinet parts myself. On first listening, I found them a little 'dark' - subdued treble and music sounding further back in the soundstage. I built the crossovers as per IPL's instructions, and added the recommended amount of long haired wool.  Ivan, who is IPL, suggests that this is a good starting point for the average room and gives alternative resistor values to adjust the mid and treble output. He also suggests varying the amount of long haired wool if required.

After giving the speakers a month or so to burn in, things improved. The bass was excellent, at least as extended as my old Ditton 66's, and more articulate. I was hearing individual notes I'd not noticed before. The mid was still somewhat dark, with vocals sounding chesty and acoustic guitar having too much body. The treble was still subdued and lacked the air and sparkle I was used to. Although the speakers were pulling out more detail in the lower end of the spectrum they had lost some of the mid and treble detail I'd been used to with my previous speaker set ups. Overall, the sound seemed a little closed in. Experimenting with placement helped, as did tilting the speakers backwards, but there was still something missing. So, I got the soldering iron out and reduced the mid and treble resistor values by 0.5 ohms and added another 5 grams of long haired wool - much better, but still not quite right. The bass seemed slightly less extended, but the mid had opened up, with no sign of the overly resonant guitar body or chestiness to vocals. The treble was better too, although it could on occasion seem a little detached from the rest of the sound and still lacked 'air'. I was quite pleased with the speakers, and considered them a worthwhile investment of time and money. This was with the speakers placed where I found they worked best before tweaking - 20 inches from the back wall and 28 inches from the side walls.

Today, I moved the speakers back so they are now 14 inches from the back  wall. I expected to hear much the same sound but with more bass. Instead, I was very pleasantly surprised with the result. The bass seems to be just as it was, but the mid and treble are beginning to shine. The sound opened up considerably and the speakers have virtually disappeared. The things I'd missed - voices and instruments hanging in space, the surprise when an unexpected voice or instrument jumps in and the sense of instruments playing in their own space had suddenly returned. I had previously noticed that they seemed much more critical of placement than any other speakers I've had (Ditton 66's, SL600's and Dynaudio Contour 1.8's), but this was a dramatic improvement.

I've gone from being fairly happy with the slightly tweaked speakers to being thoroughly pleased with them after doing nothing more than shifting them a few inches (no mean feat given the size and weight of the things). I'll live with them for a wee while before I get the screwdriver out again. I'm going to leave the crossovers as they are at present, and probably remove a little of the long haired wool. I may also try some heavy damping material in the upper part of the enclosure, which isn't as 'dead' sounding as the heavily braced transmission line cavity. Some further experiments with placement might yield rewards too.

In summary, I hadn't previously appreciated just how much difference a few inches could make!

Edited by dloper
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Hi dloper,

I live in NZ and am trying to decide on IPL Acoustic S5TL or S4TL speaker kit.

I currently have little TDL RTL2 speakers which are 20 years old, and still perfect, but I want something with lower bass capability.

Ivan thinks I should get the S4TL, even though my room is 27' x 14' main area - (normally I sit at 17' from the back wall of the long side).

I want to build the best sounding speakers of IPLs options, and note that you have the S5TLs.

I liked your write-up of them, and wonder if you still have them?

Also, have you ever heard the S4TLs?

Cheers,

Justin. 

Edited by JustingNZ

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Yes, still using them and very pleased with the sound. These are the only IPL's I've heard and I bought the kit 'blind', never having heard them. My room is around 23' x 14' and I find the bass deep and powerful without being excessive. I haven't made any further adjustments yet, although I do think the top part of the cabinet could do with more bracing and I may reduce the mid and treble resistors slightly more. A wee bit more presence would suit my ears although I'm using  Classe power and pre-amps and a Classe CD player which I believe are reckoned to have a slightly 'polite' presentation anyway.  The issue I had with the treble occasionally sounding somewhat detached from the mid has resolved itself over time so perhaps the ribbons just needed a bit more burn in.

Edited by dloper

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Thanks very much for your feedback.

In the end I was persuaded to build the S4TLs for myself, though my colleague may well decide that the S5TLs are definitely what he wants. It will all depend on how the S4TLs sound when they are built, run-in and tuned.

As for bracing, it is one of the thoughts I have with my plan. I have decided to use 25mm MDF throughout, rather than the 18mm specified - the deader the better for cabinets IMHO.

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8 hours ago, JustingNZ said:

Thanks very much for your feedback.

In the end I was persuaded to build the S4TLs for myself, though my colleague may well decide that the S5TLs are definitely what he wants. It will all depend on how the S4TLs sound when they are built, run-in and tuned.

As for bracing, it is one of the thoughts I have with my plan. I have decided to use 25mm MDF throughout, rather than the 18mm specified - the deader the better for cabinets IMHO.

Be careful with MDF, as it really can deaden the sound.  I now use birch ply for that reason.  In the '70s I once made two otherwise identical pairs of cabinets, one of MDF, the other of 700kg/m flooring chipboard, and  the chip pair were better.  But that grade of chipboard is hard to get these days; everyone seems to use MDF (or cheaper chip) for flooring.

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On 3/25/2018 at 23:02, awkwardbydesign said:

Be careful with MDF, as it really can deaden the sound.  I now use birch ply for that reason.  In the '70s I once made two otherwise identical pairs of cabinets, one of MDF, the other of 700kg/m flooring chipboard, and  the chip pair were better.  But that grade of chipboard is hard to get these days; everyone seems to use MDF (or cheaper chip) for flooring.

Thanks for the advice. The reason I thought of using the heavier MDF was some comments I saw elsewhere, and some other DIY builds of the S4TLs where the builders have doubled up on the 18mm front panel at least. In the end I asked Ivan if it would be OK to use 25mm instead of 18mm for the outer cabinet, and he said that it should be fine. They are big cabinets, and I hope the 25mm will make them slightly stiffer and less prone to resonance of any kind. I agree that the cabinet can have a significant effect on the sound, and can understand your chipboard ones sounding better with the units you had for them. I think for this build I will start with cabinets fairly "dead" and hope that the drive units and TL will sound nice like that. If not, I will try your suggestion of a  different cabinet material like your plywood.

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Super Wammer

I'm also a big fan of Baltic Birch plywood for speaker cabinets. :^

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9 hours ago, JustingNZ said:

 I think for this build I will start with cabinets fairly "dead" and hope that the drive units and TL will sound nice like that. If not, I will try your suggestion of a  different cabinet material like your plywood.

That word "dead" is used in different ways in hifi.  Although you don't want the material to add to the sound, MDF can dull the sound,  There are different opinions on this, of course, and MDF is popular with manufacturers because they can estimate cutting tool life accurately and it takes paint or stain nicely.  I do use MDF, mainly for cost reasons, and in my current speakers I have used 18mm birch ply laminated with 6mm MDF to reach the 24mm thickness I wanted, but the birch is the dominant material.  I have just acquired a pair Heybrook HB3s (thanks Ian [smarti]!) which have MDF front and rear panels with dense chipboard sides and ends.  Easier to make speaker cutouts and apply a finish to MDF!

If Ivan has tested his designs in MDF, and voiced them that way, then go with it.  BTW, I have been to his house to listen to some of his speakers and was favourably impressed.  

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On 03/04/2018 at 10:33, awkwardbydesign said:

That word "dead" is used in different ways in hifi.  Although you don't want the material to add to the sound, MDF can dull the sound,  There are different opinions on this, of course, and MDF is popular with manufacturers because they can estimate cutting tool life accurately and it takes paint or stain nicely.  I do use MDF, mainly for cost reasons, and in my current speakers I have used 18mm birch ply laminated with 6mm MDF to reach the 24mm thickness I wanted, but the birch is the dominant material.  I have just acquired a pair Heybrook HB3s (thanks Ian [smarti]!) which have MDF front and rear panels with dense chipboard sides and ends.  Easier to make speaker cutouts and apply a finish to MDF!

If Ivan has tested his designs in MDF, and voiced them that way, then go with it.  BTW, I have been to his house to listen to some of his speakers and was favourably impressed.  

Yes, I chose MDF as that was how they were designed. I also Ivan if it would be a good idea to mount the drivers flush with the front baffle, but he didn't recommend it. Presumably he's put a lot of time into the design so I'm happy to rely on his experience.  

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I really enjoyed your build write up, thanks for posting. I do t much time to pop in here these days, but these speaker threads make it worthwhile.

Stefan

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Some interesting comments here about the S5 loudspeakers.

i built a pair about 7 or 8 years ago, and found them awesome.. I had auditioned some B&W 805’s prior to the S5 build and have to admit the S5s were more than an equal. 

They do need to be tilted  back by packing out the fronts on account of the low position of the HF driver. They do need a decent size room for them to perform to their  full potential, and some space to breathe. 

Unlike tuned enclosures and closed box designs,  transmission line loudspeakers are essentially non resonant, so the coloration that box resonance can add to the music, is very much reduced. Just play these at high volume and put your hand on the cabinet. 

Because of the internal bracing of the line, the cabinet is very rigid. I personally think that 18mm MDF is more than adequate. 

The speakers are heavy enough beasts as designed by Ivan, and anything more will make them unmanageable for just one person. 

F0D649AF-7F1C-451C-9D44-A20D7D7ACC84.jpeg

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In the end, I built the S4TLs working exactly to Ivan's design - 18mm MDF with hardwood braces etc. Comparing them to the sound  from my favourite earbuds shows that these speakers are probably fairly true in terms of frequency response (at least  they sound VERY like the earbuds through the range). The damping factor on my little cheap amplifier leaves a lot to be desired, so they sound much faster on pedal drum etc when played on a good amp. I have found that moving them around my high-ceilinged room does change the sound a bit. If there was any complaint to be made about the S4TLs, it is that their efficiency is not as high as I expected - these are significantly quieter throughout the range than my old TDL RTL2 speakers which were rated at 89Db/watt with their 6-inch drivers. However, the lack of efficiency is not too big of a deal for me.  The sound is incredibly accurate and revealing, and I still get little bursts of sheer exhileration from just how good these things are. I think that the S5TLs would have been OK in the room, and I would still consider making some of these, but I would really need to hear them beside S4TLs before I would invest that time and cash. If I made the S5TLs, I would really be asking if there was any way to raise the tweeter to a position either above or beside the mid-range unit - closer to ear level. The configuration seems odd to me, having the tweeter so low down, , but I bet there is a very good reason why Ivan has designed them that way.

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