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Planning a production of special speakers - anyone interested? Lowther TP1A PM3

Started by David Pinnegar, July 01, 2012, 06:19:39 PM

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David Pinnegar

Hi!

As other threads in this topic include speakers and speakers are often used for improving room acoustics as well as for hi-fi I hope that I might not have to apologise too heavily for posting this thread here.

For many right the way through from the 1950s the holy grail of loudspeakers has been the Lowther TP1 in its TP1A TP1B or TP1C incarnations:

fitted with a Lowther PM3 or PM3/5 unit mounted in what looks like a saucepan:


The design might look like a dalek but in a domestic environment does not scream "ostentatious hifi" and can achieve remarkable WAF as a result. The sound doesn't scream ostentatious hifi either, and is natural. It's so natural that someone in another room can imagine a physical presence of a person on the radio. The sound is so spacious that one does not need stereo . . .

Finally I have managed to obtain the plans of this speaker - so complex as to require 91 pages even if the sectional diagram appears simple:

and in the Autumn I'm planning a production run of 10 to 20 units.

Obviously with such complexity, the units won't be cheap, but in long experience of speakers, few others compare.

Best wishes

David P

JBR

This is interesting.  Presumably, the 'saucepan' must have an opening at the back somewhere in order for sound to enter the extended bass cone.

Also, it is noteworthy that many modern sub-woofers are downward firing and can utilise the room itself to provide increased bass.  On the other hand, many speaker manufacturers advise against siting speakers in corners as it produces excessive bass(!).
A missionary from Yorkshire to the primitive people of Lancashire

David Pinnegar

Hi!

Yes - there is an opening about 2 inches by 3 inches in the suacepan which mates with the corresponding start of the bass horn.

The unit is a corner horn and is well balanced although best in rooms with low ceilings. With higher ceilings one has to turn up the bass a little with the bass control and if not corner placed one supplements it with a speaker in a box in addition.

Another interesting design is the Voigt corner horn and I have a friend who is a mono audio freak of the valve and vinyl variety who maintains the Voigt to give the most natural reproduction of all. I used to use a Voigt corner horn for the Tuba stop of my organ but the corner in which I used it was too damp, to the detriment of the speaker cone resulting in its demise . . . However, if anyone is interested I have a pair of a variety of these which can provide a model to be copied. A single one is currently in the barn and out of curiosity a friend put into it a £10 full range unit and attached it to a transistor radio, to good result. . . .

If used with a straight top horn rather than one with a reflection, or a bass horn with no more than a 1:2 compression ratio a unit such as http://www.ebay.com/itm/200778253597 can be effective.

In contrast however, the compression ratio of the TP1 horn requires a unit with a strong magnet to drive the air column efficiently but does so very naturally.

Most of the time normal listening levels require only less than a tenth of a watt, half a watt being loud and 5 watts being utterly deafening.

Best wishes

David P

revtonynewnham


MusingMuso

I don't know a lot about loudspeaker design, but I do know that some of the old vintage units are awfully good.

I personally cherish my old Celestion Studio 66 Monitors, which are still in daily use and sound terrific. Very big and bulky, (not to mention heavy), I've not come across many speakers that compare, and with the added advantage that they're just the right height for reading-lamps or vases of flowers; being about 3ft high.

I don't think I ever heard a Lowther Acoustics speaker in the old days, but I did used to admire the old KEF units, with their folded horn construction.

Sounds like an interesting revival of a good old design....good luck with it.

MM


JBR

I note that the unit under discussion uses an 8" speaker.  When I made a pair of hi-fi speakers a long time ago, I chose a pair of 12" units (plus tweeters) as we thought that the bigger the speaker the bigger the bass.

Recently, when we bought a new TV and sound system I found it interesting that the sub-woofer, although having only an 8" speaker, at least equalled the bass output of my home-made speakers.  Technology moves on, I suppose.  Also, as I understand it, 'long throw' bass speakers can shift as much air as much larger conventional speakers at low frequencies.

I wish I understood more about these things!
A missionary from Yorkshire to the primitive people of Lancashire

David Pinnegar

Hi!

Bass . . . can be achieved without treble and 12 inch units work well. I have a TP1 next to a well respected Tannoy Lynx unit which has a 12 inch unit for bass up to 1.7kHz and a horn tweeter above that.

On http://www.youtube.com/watch?v=45OeT8E37FM I demonstrated the way in which in particular with teh Cornet stop sounds that we hear are made up of harmonics and on http://www.youtube.com/watch?v=vii521NGSos I demonstrated the effect of separating harmonics and giving some middle ones different emphasis - which is what happens with two way or multiway speakers and especially in the confusion in the middle where pitches are thrown varyingly to both speakers at once and causing confusion.

What happens then is most unmusical: to hear what we want to hear in the detail of the music we simply turn the volume up and this either satisfies the listening experience, or not, but our listening volume preference goes up and we cease to listen to the nuances inherent in classical music. In wider society this has simply progressed to pop-concert levels and nightclub computer regurgitated rhythmic noise . . . at volumes which will benefit hearing aid manufacturing companies significantly within the next two decades.

Furthermore, with a woofer and a tweeter, the woofer has a more massive cone than the tweeter and so requires more energy, more force, to get it moving. This means that we turn the volume up to get balanced sound . . . and also its acceleration being slower separates gutteral noises and percussion into two audibly distinct sounds.

This is the methodology therefore of using a smaller unit, such as here an 8 inch, with the lightest possible paper cone of least mass able to accelerate with the help of being driven with a huge magnet to the point of vibration beyond the upper frequency of hearing, and to multiply the effective area of this cone with a horn as an acoustic transformer ending in an area of multiple square feet. The effect is that a cymbal becomes represented not by a 1 inch diameter spot but by a vibrating surface approximating that of the original instrument and a bass drum emits from the bottom horn of a similar area of the original drumskin.

The other remarkable effect is that as all the sound is generated through vibration of the same surface all the instruments retain balance with each other even down to remarkably low volumes and the detail of the midrange gives illusions of total instrumental and vocal reality. Because the cone hardly moves at all to transfer the energy to the air columns distortion is the lowest of any speaker possible and a vocal duet will produce no audible beat frequencies between the two singers even at high listening levels.

Best wishes

David P

David Pinnegar

Hi!

On ebay at the moment there is the holy grail of a pair of these vintage speakers -
http://www.ebay.co.uk/itm/Vintage-TP1-Lowther-corner-horn-speakers-with-PM3-drivers-in-amazing-condition-/271106763285

Whether used for organs or not, reproducing orchestral music is extraordinary and speech is as though the person is there . . .

On account of the compression ratio of the bass horn - (or I'm told the effect of high ceilings), bass needs a boost through a standard tone control, or extra speakers added in parallel on a 3.5mH-7mH inductor. Understanding this and working with this is worthwhile. The effect of a bass drum is utterly incredible - one can almost see the drum membrane. It's arriving through a transducer of at least 1/2 metre squared area. Likewise, cymbals are reproduced by a transducer of a size approaching the original instrument and giving a realism unattainable by any other speakers.  Transients are extraordinary and on account of minimal cone movement, and utter control of the cone by the largest possible of magnets, distortion is . . . effectively absent.

Forum members who have followed my differing advices for different Hauptwerk installations will know that anyone can have confidence in following any of my recommendations.

The units are still supported http://www.lowtherloudspeakers.com/ . Anyone doing research on them will find detractors. Very often these result from auditioning of the units inappropriately mounted: they were designed for the TP1 enclosure and that is how they perform perfectly. Cones should be of the straight rather than rolled back variety (one can slit the roll back and bring it forward) and the original type of doorknob stabiliser, 67mm diameter, can still be obtained.

Best wishes

David P


David Pinnegar

Quote from: Bobbell9 on November 23, 2012, 08:44:19 PM
Can anyone remember Jordan-Watts loudspeakers? - brochure here.
http://www.drmarksays.com/wp-content/uploads/2008/08/jw-of-sales-brochure.pdf

Hi!

Interesting to see the original sales brochure of JW. I hadn't realised that their units were only 4 inches diameter and don't greatly understand why they were saying that a large cone increases intermodulation distortion.

The problem with high movement small units is that to produce bass displacing air by way of large movement rather than large area is that one gets Doppler distortion making the sound muddy.

The horn, in this case of Lowthers, makes an enormous difference by creating great area of airmass moving by way of a cone moving minimally, thus avoiding distortion.

Best wishes,

David P

David Pinnegar

Hi!

The Lowthers on ebay made £3700 and the units were not the original PM3s with the original Alnico magnets but ones with ceramic magnets based on the PM2C.

Best wishes

David P