DIY Enclosures & Speaker Terminolgy

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Family_Dog

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I do not want to hijack Gert's thread, so have begun a new thread. This is inspired by Timber_MG's reply on the previous thread.



Timber_MG said:
Be sure to do a good job on those Tannoy cabs. That can really ruin a good drive unit to the extent that I would recommend a small sealed enclosure (personal experience with large cabs for Tannoys). The improved lower mid is really worth it (yes, I am going on about this again)

I would measure the T/S on those Tannoys first. Some older units have weakened motors and actually work in smaller cabs(and for ideal results an adjustable pad on the tweeter level helps). That and cheat with EQ (can be simple line-level passive even). The older Tannoys have enough sensitivity that you would have to use really low-powered amplification to notice it. I used 94dB odd sensitive 15" Tannoys (386s very similar to the HPDs) on a 2x25W receiver for ages in a  >40m^2 room and never missed the power so a bass-weak aligned 98-odd dB sensitive Monitor Gold might do the trick, even if it is 92dB (rough shot) sensitive at say 40Hz in a small box. Also don't forget that the output impedance of the valve amps raises Qes (effectively) changing the alignment and you will again gain the ability to use a smaller box.

The point is, that a small bit of EQ in some form before the amplifier input is a much smaller sonic mistake than a large resonant cab that needs a little less. The Tannoy Golds are notorious for their strong motors geared at the hybrid corner horn enclosures of the day. The later drive units (HPD and up) are much friendlier to employ in bass-reflex/transmission-line enclosures but pay for this with a little midband sensitivity.

Vas is huge on these, Qes is very low and Fs hovers around the mid-20s iirc meaning that you have a fair bit of flexibility, even in a sealed box (a Gold has very low Qes so EQ is almost mandatory in all but the largest of enclosures or the smallest of rooms) Get them set up right and they are a charm.

Martin

Martin,

I am completely in the dark when one refers to T&S, Qes, Vas, etc. I really have no idea what this all means. Many years ago, the only Loudspeaker books I had read were those by G. A. Briggs, of Wharfedale fame - and those were written some 50 years ago! Other than that, I have a book entitled "Hi-Fi- Loudspeakers & Enclosures", written by Abraham B. Cohen, the (then) Engineering Manager of University Loudspeakers Inc. This book was published in 1956.

Now we are hearing all sorts of foreign-sounding terminology in respect of speaker design. I for one would appreciate it if this was explained, in Plain Simple Old English, what these terms actually are and why they are now suddenly so important to good enclosure design.

You mention "I would measure the T/S on those Tannoys first"... OK, but how would I do this?

What I am after, is a plan for a pair of floor-standing enclosures that are as narrow as possible (baring in mind that the Tannoys are 15" diameter), the speakers should be mounted at more or less ear-level, be solid enough to produce good sound but not filled with sand etc so that they are impossible to move. Wood is expensive; I would be reluctant to build (read: pay someone to build) speaker enclosures unless I was assured that I had selected the correct design from the start. Currently, they are installed in Tannoy-built Lancaster cabinets, which are far from the ideal.

 
TANNOY-LANCASTER-15.jpg
   
TANNOY-LANCASTER-15-2.jpg


Would really appreciate some solid input here, I would love to hear these speakers in a decent enclosure. So far, the only improvement I have made is to raise the actual speaker height to ear-level by putting the speaker cabinets on stands.

-F_D
 
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