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Old 9th September 2008, 08:51 PM   #1
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Default Small MTM driver combo?

Hi,

I'm looking to build a small MTM. Room is smallish - approximately 12 ft by 14 ft, with an opening into a larger space. Application would be high quality, near field listening - I have no need to charge up the house to 105dB.

I've plowed through Zaph's site and others and have landed on this driver combo.

Seas W15LY
Seas 29TFFW

There's also a subwoofer in the mix, so extension below 80 Hz isn't a main concern.

Any thoughts? I'd like to know if I'm headed for a cliff before I start throwing down charge cards.....

Thanks!
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Old 10th September 2008, 01:39 AM   #2
Jay_WJ is offline Jay_WJ  United States
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SEAS Excel W15LY looks nice on Zaph's test. Only a tiny little higher distortions than the class leading Scan-Speak 15W8530.

If you don't need high SPL, why MTM instead of TM?

And why SEAS 29TFFW? There are some other lower distortion tweeters.
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Old 10th September 2008, 12:15 PM   #3
sreten is online now sreten  United Kingdom
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Hi,

Could do a lot worse than :
http://www.eldamar.net/audio/RS150MTM/
Use the sealed reduced BSC Seas tweeter option.

Though I'd go sealed MT for a nearfield,
http://www.partsexpress.com/projects...project=Encore
Already has reduced BS and would make a good nearfield monitor.

/sreten.
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Old 10th September 2008, 12:55 PM   #4
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Quote:
Originally posted by Jay_WJ
SEAS Excel W15LY looks nice on Zaph's test. Only a tiny little higher distortions than the class leading Scan-Speak 15W8530.

If you don't need high SPL, why MTM instead of TM?

And why SEAS 29TFFW? There are some other lower distortion tweeters.
Thanks, Jay.

Regarding MTM configuration, my thought was to achieve slightly greater SPL than a pair of SF Signum which I already own. Also, I was thinking that two mid-woofers should perform at less distortion than one for a given output/excursion level.

29TFFW was considered since it may crossover lower. Thanks, again.
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Old 10th September 2008, 02:04 PM   #5
Jay_WJ is offline Jay_WJ  United States
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If I wanted something better than the SF Signum, which uses custom Scan-Speak drivers, I'd definitely go with the Scan Speak Revelator. You can't find a better 5.25" driver than the 15W8530. It's the current performance benchmark.

As for the tweeter, the larger diaphragm of a tweeter doesn't automatically indicate better low end performance. It must be measured. If you want inexpensive ones, Seas 27TDFC or Dayton RS28A-4 is a good choice. If you can spend more, Seas Excel T25CF001 will be excellent. Scan Speak D3004/6600 is definitely a top performer, but the price is steep.

MTM has higher power handling than TM (i.e., lower distortion at high SPL), but doesn't necessarily mean significantly lower distortions at a normal listening level.

-jAy
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Old 10th September 2008, 02:43 PM   #6
sreten is online now sreten  United Kingdom
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Hi,

The Signum's are not loud enough nearfield ?
To better them is a tall order, especially if you like them .....
Both drivers are custom Scanspeak, and presumably very good.

Taking the bass/mid up a size notch might be preferable to MTM.
Usually the bass end parameters are better for the larger driver,
whilst the bass extension aspects of a MTM are the same as MT.
But you have subwoofer so another moot point.

There is a DIY option to increase the SPL / decrease the distortion
of the Signums. Which is to filter them 1st order, easily done at
the power amplifier input by increasing the input capacitor value.

Presuming the sub is driven by the amplifier outputs here you
interject a passive reverse 1st order filter, again very easy,
to restore correct bass into the sub, and then use its filters.

I imagine the main effect is reduction of intermodulation distortion
related to bass signals - as I have not actually done this. It is a
useful technique for any speakers not driven by an AV amplifier.

/sreten.
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Old 10th September 2008, 02:51 PM   #7
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Quote:
Originally posted by sreten
Hi,

Could do a lot worse than :
http://www.eldamar.net/audio/RS150MTM/
Use the sealed reduced BSC Seas tweeter option.

Though I'd go sealed MT for a nearfield,
http://www.partsexpress.com/projects...project=Encore
Already has reduced BS and would make a good nearfield monitor.
Thanks for the links, sreten - I'll have to give these a more careful read. For sure, the Dayton RS speakers have a lot of bang for the buck/euro.

I appreciate the hints regarding sealed and reduced BSC. I presume the BSC comment is directly related to nearfield usage?

I may be mis-using the term "nearfield". By that, I mean less than 10 feet.

Is there a particular set of circumstances where you would opt for an MTM?
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Old 10th September 2008, 03:00 PM   #8
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Quote:
Originally posted by Jay_WJ
If I wanted something better than the SF Signum, which uses custom Scan-Speak drivers, I'd definitely go with the Scan Speak Revelator. You can't find a better 5.25" driver than the 15W8530. It's the current performance benchmark.
I had thought the Signums used a Vifa driver, based on a photo I found (attached). The part number on the magnet looks like the numbering system used by Vifa.

Quote:

As for the tweeter, the larger diaphragm of a tweeter doesn't automatically indicate better low end performance. It must be measured. If you want inexpensive ones, Seas 27TDFC or Dayton RS28A-4 is a good choice. If you can spend more, Seas Excel T25CF001 will be excellent. Scan Speak D3004/6600 is definitely a top performer, but the price is steep.

MTM has higher power handling than TM (i.e., lower distortion at high SPL), but doesn't necessarily mean significantly lower distortions at a normal listening level.
I already have the 29TFFW. Actually, I have the parts to convert it to a 29TAFW, which has better distortion figures. It would be great to use this, but not mandatory.

I appreciate the comment regarding the MTM vs. MT distortion levels. Point taken.

Thanks!
Attached Images
File Type: jpg signumfoto1.jpg (48.1 KB, 160 views)
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Old 10th September 2008, 03:19 PM   #9
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Quote:
Originally posted by sreten
Hi,

The Signum's are not loud enough nearfield ?
To better them is a tall order, especially if you like them .....
Both drivers are custom Scanspeak, and presumably very good.
That's the benchmark, for me. When pushed hard, the woofers hit their excusion limits. Not the most sensitive speaker out there. There's also a bass peak in the 100 to 150 Hz range, which appears as some boominess.

Quote:

Taking the bass/mid up a size notch might be preferable to MTM.
Usually the bass end parameters are better for the larger driver,
whilst the bass extension aspects of a MTM are the same as MT.
But you have subwoofer so another moot point.
Hmmm. Must think about this more....

Quote:

There is a DIY option to increase the SPL / decrease the distortion
of the Signums. Which is to filter them 1st order, easily done at
the power amplifier input by increasing the input capacitor value.

Presuming the sub is driven by the amplifier outputs here you
interject a passive reverse 1st order filter, again very easy,
to restore correct bass into the sub, and then use its filters.
Do you mean applying a passive first order high pass filter to the amplifier inputs of the Signums, at say 100 Hz, by simply changing the value of the input capacitor? Interesting idea!

This would be relatively easy to try.

The sub doesn't exist, yet, although the drivers are sitting in the garage. Maybe I need to build the sub first and deal with the satellite based on outcomes.

Thanks!
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Old 10th September 2008, 05:25 PM   #10
sreten is online now sreten  United Kingdom
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Location: Brighton UK
Quote:
Originally posted by weinstro


That's the benchmark, for me. When pushed hard, the woofers hit their excusion limits. Not the most sensitive speaker out there. There's also a bass peak in the 100 to 150 Hz range, which appears as some boominess.

Do you mean applying a passive first order high pass filter to the amplifier inputs of the Signums, at say 100 Hz, by simply changing the value of the input capacitor? Interesting idea!

This would be relatively easy to try.

The sub doesn't exist, yet, although the drivers are sitting in the garage. Maybe I need to build the sub first and deal with the satellite based on outcomes.

Thanks!
Hi,

The first order filter should solve both of your problems in one stroke.
But it will need subwoofery to fill out the now lacking bass end.
(this needs the inverse filter)

Sub drivers ? Two boxes are better than one for placement.
The amplifier can be in one of them only or have two amps.

/sreten.
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