What type of Lowther phase plugs

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I've got a pair of old TP1 units - the London type with the short top horn. These came with EX4 drivers which were simply too top heavy and the top horn needs converting to the longer 150Hz type used in the recent "Imperator" design. I have cut a pair of 4mm pieces of MDF to insert and bend into place to test out changing the horn profile and the results are promising.

Having taken out the EX4s and used them to good advantage in some other horns, I'm using a pair of PM2C units with the new style rolled back whizzer and this seems to tame the PM2Cs very well.

The question is phase plugs. The effect is very subtle. I have tried the ordinary bullet, the Lowther new style pepper pot, and a pair of big wooden door handle types.

I assumed the door handles dispersed treble more, and possibly tamed the Lowther units better, but actually makes them possibly more directional. Psychosomatically I believe the pepperpots make them more directional too, with a focussed line of increased treble on axis. But possibly the bullet, or no phase plug, is best of all . . . but the effects are so subtle that it's difficult to make an objective evaluation.

What are other people's experiences? And especially in front horns?

Best wishes

David P
Now, this is going to be entirely personal opinion and preference, but....

I have DX2's (EX2's with the back removed) that came with the pepper pots (lemon squeezers) and DX3's that came with bullets. Yes the lemon squeezers are more directional, and if there is anything that the DX's can't stand, it is more directional. The huge treble hump goes away something like 15* off axis and the FR smooths out pretty well. But by 15*, the top end starts to sag significantly.

So... Use the bullets and toe them in until the edge comes off the treble. (Don't have the door knobs, so not opinion.

I've listened to the 'door knob' with PM4 in front loaded horn (Oris 150). I felt it's not beaming very much. It has an even better HF dispersion than my 7" mid with bullet phase plug (compared up to around 14kHz or so).

I've read somewhere mentioned that the 'door knob' forms a narrower 'window' for the whizzer cone, thus a 'better loading' to the HF. This was designed to work with front horn in which the midrange would be boosted. But I'm wondering why the HF of Lowther needs any reinforce to match the horn loaded midrange...
My Dear Sir,

Keeping in mind your valuable advice...

You are acquainted to thousand times of more enthusiats than myself does. Might a few of them own this phase equalizer plug and be kind to measure and share its dimensions?

I would be grateful!


I have tried Lowther EX3, then I stripped the drivers to DX3 and tried them in BLH with original Lowther plastic plugs, no plugs and DIY oak plugs. With my horns and room I prefer the sound (by small margin) of oak plugs and I like the looks.

In my opinion Lowther plastic plugs are not worth copying - the picture may help you to make different DIY plugs.



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I have spent years with the various Lowther phase plugs, but I keep
coming back to the original bullets.

Of course, I am not horn loading my drivers...


I am horn-loading the DX4's and for a long time I was playing without any phase-plug giving me a more fluid ESL-like sound....BUT less focus in the middle.
Now I use the standard bullets (Arranged a couple of bronze ones ;) ) and this result in a tiny bit of reduction in the high-F....BUT....the Fostec driver starting from 14kHz takes care of this....now I got it all...PERFECT!
Phase Plugs

Guess this is the sort of question I should answer.

A vast majority of front horn loaded Lowthers use the wooden "light bulb" phase plug. Those who do not generally use an elongated bullet style. Same as Lowther's bullet phase plug, just longer (add wooden dowel).

Effects are subtle. Usually the light bulb plug gives a slightly more extended high, with slightly better dispersion. But I have not heard them in your cabinet.
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