Rogers LS7:

Shortly after joining the BBC in 1996, I made the mistake of borrowing a pair of LS3/5a's. Of course, it meant my old Musical Fidelity MC1's had to be replaced!

At the time, the second-hand price of LS3/5a's was around £400, which I felt to be a bit much. After a bit of investigation, I discovered The Emporium in Diss, Suffolk. They offered me a loan of some Spendor BC-1's which were going for £100, and a pair of Rogers LS7's which were priced at £200

It was an interesting week, as I still had the 3/5a's, plus a pair of Spendor SA-1's that a friend was trying to sell me as a cheaper alternative LS3/5a... My landlord was starting to seriously worry about me!

Almost from the moment I heard the LS7's, I knew they were exactly what I was looking for! I normally refrain from making quick judgements until after a few different recordings because first impressions are often misleading. My Cambridge Audio DAC is proof of that!

Technical:

The enclosure is made using classic "thinwall" construction, but with cheaper MDF instead of plywood. The cabinet walls are 12mm and the baffle is 18mm. All walls except the baffle are damped with self-adhesive bitumen pads and lined with foam. The cabinet has a real-wood veneered which is stained gloss-black in my case.

The bass driver is retained with decent machine bolts and captive nuts, and the port opening is flared to reduce port noises. The tweeter and plastic connection plate (holding the crossover PCB) are held with wood screws. Gaskets are used on every removable component to ensure a good air seal.

Until I bought the ATC's, this was probably the biggest magnet I'd seen on a bass driver! It's about twice the size of the LS2/14 used in the BBC LS5/9's. Note the "Swisstone Electronics Ltd" markings on the casting - I'm not sure what the exact relationship was, but basically it seems that "Rogers" = "Swisstone"

As mentioned on the LS5/9 page, the two bass drivers share some obvious visual similarities. However, they measure very differently:

The accuracy of these results are not guaranteed! I made these measurements a little while ago while I was playing around with the LS7 driver in a LS5/9 cabinet (Results were interesting, but probably won't amount to anything). Perhaps they might be useful if you ever need to find an equivalent replacement driver...

The crossover is similar to the LS5/9, but somewhat simpler due to the lack of treble adjustment. The description given on the page is equally applicable here. The only thing to add is the series inductor in the treble section - this will help to roll-off excessive (ultrasonic) frequencies, which effectively offers the tweeter some protection from HF oscillation or clipping in the power amplifier.

As you can see from the photo below, some components aren't fitted. Perhaps the crossover PCB, labelled "ROGERS LSX MODULE 1", was standard across several Rogers models at the time, and different components were fitted as required. Another possibility is that the design was simplified to save a few pennies. In the Hi-Fi Choice review below, they mention the "13-element 3kHz crossover" - I can only count 13 components if I include the omitted ones...

I've not bothered to include any details of the Celestion HF1000 tweeter, as it's the least interesting component in the design. It's also the weakest part, in my opinion. The criticisms in the review below mostly point to the tweeter, and I certainly feel that my objections can be attributed to it.

Mods:

I quite often receive emails asking about modding these speakers (and others on this site). From experience, I would advise caution. I tried changing the two electrolytic capacitors for expensive polypropylene devices, and the results were horrible! The midrange glare mentioned below was made much worse, and the original caps went back in a few weeks later!

Electrolytic capacitors have well-known problems and limitations, and the designers working at Rogers back then were (are) talented and experienced engineers. Quite simply, these limitations were accounted for at the design stage, and substituting "better" components will upset the balance.

As for "upgrading" internal wiring, before doing this try to work out how much standard copper wire is on each inductor in the crossover, and in the voicecoil!

I'm not saying don't do it, but don't expect huge changes in the sound, because, even assuming that you've managed to find a short length of wire that sounds appreciably different to standard wire, think about the bigger picture first.

Sound Quality:

At the time, I found that the 7's had all the qualities that I liked about the LS3/5a's, but with a extra octave of bass. The thing against the LS7's was their size, mainly because the room I was renting was only 12 by 8 feet, but I knew I wouldn't be there for the rest of my life...

They were my main speakers for about 5 years. Happily my first impressions were largely confirmed. They have a very neutral midrange that make vocals sound worryingly natural. The imaging is very good and easily up to the standard of modern loudspeakers. What impresses most is the bass - modern speakers just don't sound the same, unless you're able to spend a large amount of money. It's very clear and natural, and doesn't sound boxy or boomy like some modern designs I've directly compared them to.

I know this is a slightly strange thing to say, but if there's bass in the music, then you hear it. If there isn't, then you don't. I say that because speakers with higher system-resonances and poorly damped responses seem to produce bass that always sounds the same, and doesn't move up and down the scale like it should.

If I had to find a minor complaint, it would relate to the midrange. At low listening levels it's fine, but when you listen at higher levels some 'glare' is apparent. It may be a peak in the response, or perhaps the tweeter is unhappy at the lower end of its frequency range above a certain power level. Unfortunately, the acoustics of my lounge contribute to the effect, with the net result that some CD's are uncomfortable to listen to at moderate levels. A recent CD player change helped enormously, but having tried a variety of alternative models, I know that the speakers are at least partly responsible. A colleague has a pair of LS7's and I'm considering asking him for a loan, which would help me decide if it is a 'characteristic' or a fault...

They are quite efficient (88dB/W), which means that my Musical Fidelity A1 can drive them to reasonably high levels. They are well-suited components, and I was happy with the combination for many years...

Click here to read some interesting comments from visitors.

For details of what eventually replaced them, first check out the BBC LS5/9 page, and then the ATC SCM20SL page...

LS7 Hi-Fi Choice Review:

Click here for a review of the LS7. On the whole, I like this review, for fairly obvious reasons. One thing I'd comment on is the "slightly 'edgy' and 'sibilant' treble" they observed: having heard CD players from the time, I wonder how much of that is a function of the source?

I use mine without the grills for the reasons given. And I've found that the 'rich' bass can be tuned by careful positioning. In the test room they were positioned a metre from each of the side walls and 0.8 metres from the back wall, firing down the length of their 13'9" by 18' listening room, whereas I listen to them across the width of my lounge, which puts them at least 1.5 metres from a sidewall.

Update - 16/8/2004: The LS7t:

The later version of this speaker, the LS7t, used a different tweeter, but kept the rest of the design largely unchanged. A titanium dome unit was selected, hence the "t" suffix. I've only ever heard an example briefly, and to my ears the treble was much crisper and more detailed, but I wondered if this could become tiring after extended listening. Critics didn't seem to receive the model quite as warmly as the predecessor, but there are plenty of happy owners out there who love them...

Thanks are due to Andrey Tiurpenko for sending me these pictures and allowing me to publish them here.

Note how the front edges of the sides, top and bottom panels are square - my older LS7's have a 45 degree machined edge. The grill cloth appears to be a conventional material, as opposed to the Tygan used on my older LS7's.

The tweeter is clearly very different to the original Celestion model. Many thanks to Danko Suvar for identifying it as an MB Quart model, apparently a well-regarded model.

As you can see, the port has been moved off the centre line and the chassis has been painted black. The tweeter is very different to the Celestion HF1000.

These models can be buy-wired, as the market demanded at the time. This is something that is easily done with conventional parallel crossover networks, so the tempation must have been overwhelming for manufacturers to do this - an extra "tick" on the reviewers check-list.

Many thanks to Chris Hardy for supplying me with the crossover schematic, sketched from the crossover PCB in his examples:

As you can see, it's slightly simplified compared to the LS7. The bass section is almost identical, but lacks the impedance correcting network R3 and C2. The treble section is, not surprisingly, quite different. The inductor is used as an auto-transformer as well as a frequency-dependant component - the 15 ohm LS3/5a's and LS5/9's use this trick.

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