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Eminent LFT-16 (2)
Sound quality
Conclusion
Readers Letters
Manufacturer's Correspondence
Measured performance
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MANUFACTURER'S CORRESPONDENCE

 

From Bruce Thigpen of Eminent Technology

 

Noel,

I want to apologize because you received a version of the speaker that we are no longer producing. The measurement flaw is our mistake, a failure to analyze a replacement woofer carefully.

 

We started producing the speaker with a woofer that we designed in-house and was manufactured by Eminence. The cone supplier at the time (Nuway) was acquired and no longer makes the cone we want, so we substituted a woofer without checking the impulse response. In fact the speaker you have will not exhibit the dip you find with either a sine sweep or pink noise or music reproduction. The dip occurs in the first .0006 seconds of a step or mls response centered around 700Hz. It should measure fine with other techniques, this is why we missed it.

 

About 50 pairs of speakers went out with the woofer you have and will be replaced at no charge to any customer who wants the new driver.

 

The replacement woofer we are using now does not exhibit the problem and passes all different types of frequency response measurements. We can arrange to have Darren change the woofer and send it back to you.

 

We like to produce the same product year after year. We manufacture the planar transducers and the cabinets in house and the quality can remain consistent. We never undertook cone loudspeaker manufacturing because it is highly competitive, now with changes in loudspeaker suppliers, for the last ten years or so we have not been able to source the same cone speaker components for any length of time.

 

Thank you very much for looking at our products.

 

Bruce Thigpen

Eminent Technology (Florida, USA)

 

Hi Darren,

Here are Pink Noise and Sinusoidal (stepped &  gated) responses for the LFT-16 and indeed they show just the same picture: drive units out of phase. Re-connected in phase they sum as expected and change the aural character of the loudspeaker. But obviously the bass unit is too sensitive for the mid and treble units. There are various ways of overcoming this but sensitivity will suffer of course. All the same, they  have smoother mid and treble than most loudspeakers, in spite of everything.

regards

Noel Keywood (London, UK)

 

Hi Noel

Thanks for your reply, are you happy to publish the review with you findings or would you require the LFT-16 with the newer bass units?

Darren Hatcher, Eminent Technology UK


Hi Darren,

Probably both.  We will put an in-depth look on the website with updates as they come in, and notice of updates too. The loudspeaker is worth covering because it is unique and strong in crucial areas.  The magazine may perhaps take a shorter condensed version, that refers to the website coverage.

regards

Noel Keywood

 

Hi Bruce,

It seems both sets of LFT-16s you sent over are not working to their full potential, such a shame as we were hoping to get the review in for this month. Could you please contact Noel and cc me in and I will forward your reply to the customer. Is it a component error? I have no way of testing these things, any help would be useful.

Kind Regards,

Darren.


Darren,

We found the problem, the microphone and preamp combination we used to measure the speaker had a peak at 20kHz. The microphone with a different preamp calibrated very nicely, but the measurement preamp we use did not agree with it which resulted in a pretty big peak, about 10dB, in the response at 20kHz. So the resultant speaker design using that combination has a significant roll off at 20kHz, opposite the microphone. The irony is that I took the speaker home and pronounced it as good, unfortunately I evaluated the redesigned crossover on an FM tuner for several hours, since the FM tuner was at best flat to 15Khz I completely missed that fact that the tweeter is down 10dB at 20kHz.   We are trying to solve the problem and determine the best solution. Hopefully we can do this quickly. We will need to modify or exchange both pairs speakers  Needless to say I am disappointed and will endeavor to make this right.

Bruce Thigpen 
Eminent Technology



 

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