6.5/7inch midbass recommendations - diyAudio
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Old 27th May 2005, 12:09 PM   #1
AntM is offline AntM  United Kingdom
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Join Date: May 2005
Location: Edinburgh
Default 6.5/7inch midbass recommendations

I'm upgrading my current system, and would like to know if
anyone has recommendations for a 6.5-7inch midbass driver, cosing less than 80UKpounds per unit? My current system has grainly treble and ill-defined slightly woolly bass, but fantastic stereo image.

Current system:
Focal 7K4211db dual-vc kevlar driver
Seas H398 25TAF/G tweeter
2nd-order Xover
20litre ported enclosure

New system:

Morel MDT30 Soft dome tweeter.
Contemplating the SPH-165KEP - looks good on paper, heard many recommendations, but seems too cheap!

I want to use a simple Xover, 1st, or 2nd order max + zobel, but no fancy notch filters

Any help before parting with cash would be great.
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Old 27th May 2005, 01:41 PM   #2
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Hi,

I've got those Monacor's myself but they're still lying on the shelf because the cabinets are not finished yet.
However I've also heard those monacors in another pair of speakers. They sound very good in the "bass/lmid" region. But I do not believe that they're that easy to crossover. When you let them play higher they have the tendency to start overemphasizing on the "ssss sshhh" tones (maybe some breakup also).
So for mine I bought the seas H1212 alu dome tweeter, this one has a low fs and high power handling which gives me the opportunity to experiment with lover x-overpoints.
Don't get me wrong many people are happy with them using a simple x-over but I think that you can have much more out of these if a more complex (aided with measurements and modelling software) x-over is used which addresses the speaker's weaker points.
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Old 27th May 2005, 02:49 PM   #3
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I also (am going to) use the SPH-165 KEP. And yes, it is cheap. So what?
I tried it in an two way with a RT2C tweeter. Sounds great. Stopped the project before final tweaking because I am building an active system. Why not just try this speaker. You won't be dissapointed (it is very good but in the end it's all about your own taste...)

Let me give you another choice: Alcone AC 6.5 HE.
I think this speaker also sounds very good. Also cheap I'm afraid...
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Old 28th May 2005, 09:29 AM   #4
AndrewT is offline AndrewT  Scotland
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Hi,
Audax carbon cone sound nice.
the 210 won't reach up to the treble nicely so you would have to settle for a 170 and have a bit less bass.
Or try a 2.5 way bringing in a second unit below some mid frequency.
Don't know current prices but I think you should be able to source all 4 mid/bass for under your budget.
BTW you will need a tower to give the cabinet volume for two drivers. Keep the cab narrow and deep with rounded corners and offset the treble so all edges are a different distance from the unit.
__________________
regards Andrew T.
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Old 30th May 2005, 02:05 PM   #5
AntM is offline AntM  United Kingdom
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Many thanks for the responses.
Bylie, the Morel tweeter I'm using goes down to 1.6kHz (700Hz resonance), so should be no problem with crossing over quite low.
The Alcone looks like it's got quite a nasty breakup above 2kHz, so that may be out of the question with a simple Xover.

Funny how the specs don't always add up though - one thing I noticed was that the Moncor driver Fs is quoted at 30Hz, yet the published spec shows an impedance peak just above 40Hz. It may be my ignorance, but I thought the two were supposed to coincide?

30Hz seems really low for a 6.5" unit.
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Old 30th May 2005, 02:14 PM   #6
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As Leeuwarden said, just try this speaker. You really won't get dissapointed! especially for the price!
And if you plan to have the xover point at aprox. 2Khz you should consider the RS180 from Dayton, a real bargain.
I recently build a speaker with the RS150 wich I crossed at aprox. 2,4 khz. I just used a 12db/oct filter and no problems with the cone breakups (I measures it, so I know).
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Old 30th May 2005, 06:38 PM   #7
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Quote:
Originally posted by AntM
Funny how the specs don't always add up though - one thing I noticed was that the Moncor driver Fs is quoted at 30Hz, yet the published spec shows an impedance peak just above 40Hz. It may be my ignorance, but I thought the two were supposed to coincide?

30Hz seems really low for a 6.5" unit.
I've done some crude measurements and found that the measured fs (free air) was between 33Hz to 35Hz. So I just based my cabinet design on those values.

However some interesting facts about this driver :

- The original T/S found on Monacor's website : (link)
As you see here these are the T/S parameters found on most sites.

- Another PDF found on a Polish (I think) website : (link)
As you can see here the fs is suddenly changed to 40Hz which, I admit, coincides with what we see on the impedance graph.

- A scanned article from K+T (in German) : (link)
As you see in this article a lot of T/S parameters are different from the published ones.

- My own free air measurements indicate a fs of 33Hz to 35Hz. The measurements were done with the loudspeaker lying on the floor (magnet facing down using a simple multimeter, 8ohm resistor, amp and frequencygenerator (I followed this guide : link). Maybe this method is not 100% correct (please tell me if it isn't) so don't take my word for it. I also did only measure the fs in free air, maybe this is not enough to get reliable results?

Now you tell me your conclusions about this .

If you're interested in using this driver I could publish my early CAD drawing.
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Old 30th May 2005, 06:47 PM   #8
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TS-parameters can vary a LOT!
But, mostly e.g. when the fs is lower then Vas gets higher and visa versa.

I measure TS-parameters with my PC, and sometimes they vary due to humidity and other influences.
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Old 31st May 2005, 12:56 PM   #9
AntM is offline AntM  United Kingdom
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Join Date: May 2005
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I've had a play with the Thiele-Small calculations for both extreme cases (the Monacor datasheet vs the German one) and in a 20l ported enclosure the F3 is 38Hz vs 42Hz (the latter also corresponding more or less to the example on the German spec). So not a huge problem, but 40Hz vs 30Hz with the same VAS would result in an F3 of 50Hz which would be disappointing.

I can believe your measurement, Bylie - that's how I would have measured the free-air resonance too. Is this a recently bought unit? I wonder if there were production changes.

By the way, I finally got my Morel tweeters in the box last night, and combined with the Focal midbass units (see first post), the change in sound quality was massive once I ditched the second order Xover, and went for a 1st order one. The biggest improvement? Bass weight and dynamics! Strange what a tweeter can do! (I suspect it was actually the second-order Xover that had a bad transient response)
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Old 31st May 2005, 01:48 PM   #10
gustav is offline gustav  Sweden
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Hello everyone!
I once made a FR measurement of this Monacor driver (in IB).
The driver has serious problems in midband !
I did not use the driver. I would use the Focal or some other good driver instead.

Good luck!
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