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Old 22nd September 2013, 11:25 AM   #21
DrBoar is offline DrBoar  Sweden
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KEF B200 SP 1014 (high MMs and high Q)
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Click the image to open in full size.

KEF B200 SP1014
This is how it looks and how it measures. The Q might appear high but this is an effect of 35 years of aging that have made the suspension less supple. If the Fr could be dropped from 40 to 25 Hz the Q would drop from 0.8 to 0.5. That would be in line with KEFs data sheet.

This is the impedance of SP1014 in Decca placed in corner and reverse wall (driver facing forward).
Click the image to open in full size.


The left graph in post 12 of the B200 in a voigt pipe of different dimensions than the Decca show some features to note.
Driver NF: the driver has a substantial peak just above the dip of the fundamental.
Pipe NF: there is a mismatch of peak output from pipe and the tuning frequency. At tuning frequency the pipe output is several dB below the peak output.

Time to look at how the KEF works in the Decca.

Click the image to open in full size.
Driver Near Field: The KEF is in red and the black trace is the Philips 9710 as a reference. (I had to increase the KEF by 10 dB to match it to the 9710). The B200 has this +5dB hump at 65 Hz, the 9710 while not a real low Q driver still is flatter than the KEF.


Pipe output: Above 80 Hz there is no difference really between the red KEF and the black Philips. Below 80 Hz the Philips is within +/- 2 dB from 33 to 80 Hz relative to 92 dB. If I use the same reference level for the KEF it peaks at 10 dB at 58 Hz.
Click the image to open in full size.

The B200 SP1014 regardless of other qualities is not a good driver for tuned pipes. The fact that measurements 38 years apart on two different pipes gives so similar results suggest that the finding is general. I also have the feeling that the 9710 works but is marginal in tuned pipes but the high frequency lift is good in orientation with the driver facing the back wall or corner.
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Old 22nd September 2013, 01:33 PM   #22
DrBoar is offline DrBoar  Sweden
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This is a crazy candidate a Pioneer TSE20 Car speaker. They fit the cutout and the Q is lower than the previous two tested drivers. I usually measure MMs and Vas by adding a roll of masking tape to the cone but the way this one looks it can not be done. My guess is that it is high mass low Vas driver.
Click the image to open in full size.

Partial Thile Small
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In the pipe, hard do see any impedance peaks at the harmonics.
Click the image to open in full size.

Now for the response curves. I have adjusted them to equal output disregarding differences in surface area.
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Pipe output is really flat +/- 1dB from 40 to 70 Hz, good match between peak pipe output and the dip in driver response centered at 45-50 Hz.

Now I am really out of drivers that fit that 190mm cutout, I think at least...
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Old 25th September 2013, 09:13 PM   #23
DrBoar is offline DrBoar  Sweden
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Added a 16mm MDF subbaffle to fit standard cutout 8" drivers, that I have a few of. First in line is a Peerless 831862. Polypropylene cone, foam surround, Low Q a typical modern bass reflex driver.
Click the image to open in full size.

Click the image to open in full size.

Compared to wall the corner postion lowers the tuning and also the lower impedance peak hight.Click the image to open in full size..

Instead of a hump at 70 Hz as the KEF there gentle slope from 130 to 70 Hz.
Click the image to open in full size.

I also tried to measure in the corner but despite being very close to the cone the walls close by totaly mess up the response curves.
Click the image to open in full size.

With this driver I can hear more of a boxy coloration than what I heard with the Philips 9710, at least I think I do. The relevant comparison would be to listen to the same driver in a welldamped box.

I saw someone using a constriction baffle in a tapped horn to reduce harmonics. Has onyone done this in Voigt pipes? I am thinking about trying to reduce that pesky 5th harmonic.
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Old 26th September 2013, 09:53 AM   #24
DrBoar is offline DrBoar  Sweden
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An other Peerless PP cone driver, this one with inverted PP dome and rubber surround.
* Manufacturer: Peerless
* Model: 850126
* Piston Diameter = 175.0 mm
* f(s)= 48.45 Hz
* R(e)= 6.00 Ohms
* Z(max)= 58.76 Ohms
* Q(ms)= 4.488
* Q(es)= 0.511
* Q(ts)= 0.459
* V(as)= 43.160 liters (1.524 cubic feet)
* L(e)= 1.91 mH
* n(0)= 0.92 %
* SPL= 91.72 1W/1m
* M(ms)= 20.31 grams
* C(ms)= 0.53 mm/N
* BL= 8.52

Click the image to open in full size.

Click the image to open in full size.

The response is quite similar to the other Peerless driver
Click the image to open in full size.
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Old 26th September 2013, 10:11 AM   #25
DrBoar is offline DrBoar  Sweden
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A high efficiency paper cone driver salvaged from Audio Pro 4-40 dipole speakers from the late 70s. Corrugated paper sorround coated with some sticky green stuff. The frame look like the Peerless did in the 1970s.
* Piston Diameter = 170.0 mm
* f(s)= 47.10 Hz
* R(e)= 6.65 Ohms
* Z(max)= 34.26 Ohms
* Q(ms)= 1.575
* Q(es)= 0.379
* Q(ts)= 0.306
* V(as)= 59.860 liters (2.114 cubic feet)
* L(e)= 0.93 mH
* n(0)= 1.57 %
* SPL= 94.07 1W/1m
* M(ms)= 13.81 grams
* C(ms)= 0.83 mm/N
* BL= 8.47

Click the image to open in full size.

Click the image to open in full size.

Note the impedance peaks at the harmonics. Compare that to the lack of impedance peaks for drivers like the Pioneer one. However, in frequency response they both have output peaks at the harmonics. So when comparing different drivers those impedance peaks say little if anything about the harmonics.

Click the image to open in full size.

Compare these curves to the one in post #12 the set to the right with that gentle slope below 200 Hz. Pretty similar, so I assume that that Peerless driver had a light cone and low Q as this driver has.
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Old 26th September 2013, 11:28 AM   #26
xrk971 is online now xrk971  United States
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Dr Boar,
As always, you continue to amaze us with your thoroughness in studying this cabinet. Nice work! Is it my correct understanding that the ideal driver for this horn is a low Qts variety? The Pioneer car audio one seems very good but I think car door panel speakers are generally high Qts. I have often wondered about using a Pioneer 6.5 in coaxial on "fullrangedriver" type cabinets.
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Old 26th September 2013, 01:11 PM   #27
DrBoar is offline DrBoar  Sweden
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xrk971,
So far it looks like the medium to low Q drivers works better than the high Q driver I have tested so far. But as I have only tested one high Q driver so far (KEF B200 SP 1014) I have to test other high Q drivers (in the pipeline!).

Low Q is not the only thing, my guess is two drivers with Q of 0.3 with one having a Fr of 20 Hz and one 80 Hz might behave differently in the Decca Pipe.
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Old 26th September 2013, 09:35 PM   #28
DrBoar is offline DrBoar  Sweden
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High Q (1) low mass 8gram and high Fr (63 Hz) and impressive power handling of 12 Watt American rating, the more modest UK rating is 6W.

BTW I was belting out some loud rock music with the Peerless 850126, I felt the vibrations in the hardwood floor, then the vibrations in the lower part of the front is substantial and quite a lot in the backside below the driver and surprisingly in the top. The flat and angled sides as well as the driver baffle fares much better.

Click the image to open in full size.

I front mounted it, sealed as best as I could, but it really should be rear mounted.
Click the image to open in full size.

The driver has some resonances as can be seen at the impedance and phase curves.
Click the image to open in full size.

In the pipe the lower resonance peak is lower than upper one, that seems to be the case with drivers that has an Fr above tuning frequency.
Click the image to open in full size.

The output does not look good the driver has a peak around 100 Hz and the pipe maximal output is above the tuning frequency.
Click the image to open in full size.

The Axiette could be used on open baffle at low levels or in a closed box/ box with resistive damping. But pipes and horns is not were it works well.
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Old 27th September 2013, 09:12 AM   #29
DrBoar is offline DrBoar  Sweden
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A third high Q driver this time the Philips AD8061W4, a very common driver here in Europe in its day, in run of the mill HiFi setups.
Click the image to open in full size.

Despite being a budget driver they show little variations between samples.
* Manufacturer: Philips
* Model: 8061W4
* Piston Diameter = 170.0 mm
* f(s)= 64.60 Hz
* R(e)= 4.17 Ohms
* Z(max)= 18.45 Ohms
* Q(ms)= 4.564
* Q(es)= 1.333
* Q(ts)= 1.032
* V(as)= 32.260 liters (1.139 cubic feet)
* L(e)= 0.80 mH
* n(0)= 0.62 %
* SPL= 90.04 1W/1m
* M(ms)= 13.62 grams
* C(ms)= 0.45 mm/N
* BL= 4.16
* Manufacturer: Philips
* Model: 8061W4
* Piston Diameter = 170.0 mm
* f(s)= 61.91 Hz
* R(e)= 4.16 Ohms
* Z(max)= 17.88 Ohms
* Q(ms)= 4.480
* Q(es)= 1.358
* Q(ts)= 1.042
* V(as)= 38.530 liters (1.361 cubic feet)
* L(e)= 0.76 mH
* n(0)= 0.64 %
* SPL= 90.18 1W/1m
* M(ms)= 12.41 grams
* C(ms)= 0.53 mm/N
* BL= 3.85

Click the image to open in full size.

And then the response ( Pipe output lowered 5 dB)
Click the image to open in full size.

Driver peak +4dB above midrange levels from 75 to 100 Hz, pipe output is from 35 Hz and upwards. They sound quite good if you like a fat bass pounding away, I think this is reflection of the good midrange with a fall above 3 kHz without any nasty peaks.
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Old 27th September 2013, 11:27 AM   #30
DrBoar is offline DrBoar  Sweden
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The 4th high Q driver: Something similar from Seas but with a paper surround, the Seas 21F-GW. On top it is Seas to the left and Philips 8061 to the right.
Click the image to open in full size.
* Manufacturer: Seas
* Model: 21F-GW
* Piston Diameter = 175.0 mm
* f(s)= 57.87 Hz
* R(e)= 4.76 Ohms
* Z(max)= 15.09 Ohms
* Q(ms)= 2.971
* Q(es)= 1.369
* Q(ts)= 0.937
* V(as)= 42.030 liters (1.484 cubic feet)
* L(e)= 0.70 mH
* n(0)= 0.57 %
* SPL= 89.64 1W/1m
* M(ms)= 14.62 grams
* C(ms)= 0.52 mm/N
* BL= 4.30
Click the image to open in full size.

Click the image to open in full size.

The sound is OK but not more than that.
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