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Worst measuring loudspeaker?

DSJR

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I'm stunned frankly, that a speaker range such as this suffers no deep bass extension yet the TL cancellation between 100 and 200Hz is still there. Ancestors IMF's larger models had prodigious bass extension and output but the 150Hz or so issues were disguised somewhat by pulling the mid and high frequencies down somewhat to match it, leaving the 20 - 100Hz region up in level. The later RSPM IV, in addition to having switchable lf filters, damped the bass extension more and this minimised the 150Hz-ish dip somewhat. PMC don't seem to care about this TL characteristic and leave it blatantly there. The rise and rise at hf is again deliberate and maybe to attract B&W customers? There's usually a deep 'scoop' in the lower kHz region as well. For such an exalted company, I don't know what the heck is going on with them, although in a large room I liked the powerful energetic Fact Fenestrias which did entertain and involve, despite any response anomalies.. Even these seem to roll off below 80Hz - surely not right?

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dfuller

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I've said it once and I'll say it again, the only PMCs worth even trying are their most recent DSP actives.
 

fpitas

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Anything from PMC is not cheap. Surely they could afford a testing microphone. The old stoner of a founder should really hire better people. Or at least some educated ones. Holy F*ck. All PMCs I have seen measurements for have that chasm between 125 and 175 hz.
I suspect these were "designed" by marketing.
 
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Bjorn

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That top end is a real firestarter. The whole review is well worth reading for entertainment, there is a comment about the top end that I won't spoil by quoting.

PS Dennis posted about this above.
What does the reviewer think when he sees the measurements after writing his review?
 
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Purité Audio

Purité Audio

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Reviewers think?
Keith
 

fpitas

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What does the reviewer think when he sees the measurements after writing his review?
He seems so enthralled by the idea it has a transmission line, I suspect it could hoot like a steam calliope and he'd be happy.
 

fpitas

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They aren't transmission line either. That requires much more length.
I suspect trying to force-fit the "transmission line" idea is exactly why they turned out special.
 

Bjorn

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The question is, how do your market your products without sending them to subjective reviews? And if you don't have reviews in magazines, you could also potentially be locked out from hifi shows. There are ties here.
 

mwmkravchenko

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I suspect trying to force-fit the "transmission line" idea is exactly why they turned out special.
You can increase stuffing density and shorten a line length. It's not impossible. But that will be evident in a very flat impedance curve.

Mark
 

mwmkravchenko

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The question is, how do your market your products without sending them to subjective reviews? And if you don't have reviews in magazines, you could also potentially be locked out from hifi shows. There are ties here.
You mean the audio mafia :eek:
 

fpitas

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You can increase stuffing density and shorten a line length. It's not impossible. But that will be evident in a very flat impedance curve.

Mark
It's hard to guess what they thought they were doing, and obviously it didn't work. But it seems they hoped the port would add something beneficial:

a notch at 150Hz broadly coincides with the peak in output from the 'Laminair' vent at 155Hz while another notch at 245Hz mirrors a port peak at 255Hz.

In which case they couldn't stuff like crazy. Maybe that 105Hz peak comes from the port and serves for "bass".
 
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mwmkravchenko

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It's hard to guess what they thought they were doing, and obviously it didn't work. But it seems they hoped the port would add something beneficial:

a notch at 150Hz broadly coincides with the peak in output from the 'Laminair' vent at 155Hz while another notch at 245Hz mirrors a port peak at 255Hz.

In which case they couldn't stuff like crazy. Maybe that 105Hz peak comes from the port and serves for "bass".
Good point. I never bothered reading it. I am not impressed with PMC at all.

Mark
 

fpitas

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Good point. I never bothered reading it. I am not impressed with PMC at all.

Mark
The sad thing is, if they just used a common garden variety bass reflex, it might have been far better. Score one for marketing.
 

mwmkravchenko

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The sad thing is, if they just used a common garden variety bass reflex, it might have been far better. Score one for marketing.
Yup. It's amazing what can happen when you have a purpose designed driver. (shameless plug) All of a sudden you are not DSPing the crap out of some poor handicapped wannabe and you can actually do this right from the get go! I just designed a 6 inch "subwoofer" for a prospective client that will function very well in a 6 litre enclosure. Yeah a 1/4 cubic foot. 64mm voice coil to boot. So no, it is not power limited. And 11 millipedes of Hex max. So reasonable SPL. Watch out KEF I'm coming :oops:

Mark
 

dfuller

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The problem, of course, is that open TLs don't work in small cabinets. The smallest box I've seen it not be an abject outright fail in is the somewhat larger PMC 6, and it still has a big interference dip around 300hz.
 
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