Speaker design factors

[bobhowell]

I have been looking at different design for a future project and just saw a statement on some site about value of drivers. A driver was mentioned as good value and, if use in an MTM configuration, it would still have less distortion than a Scan Speak MT at 4 or more times the price.

I did not know an MTM had that much of an edge over a top quality SS, of similar size in a MT. Is this overstatement or sometimes true, etc.

MTM is a good way to get small speakers, but most are 4 ohm and I have older amps of unknown quality. I don't play loud, so, ok now, but the kids I may give them to: who knows.

Thanks

Bob

[69Stingray]

A MTM will have lower impedance (assuming you wire the two drivers in parallel) and double the cone area, which give you an additional 6 dB of output. Therefore, you need less power to drive a MTM to the output as a TM and typically, speakers produce less distortion with less power.

If you are looking for an 8-ohm MTM, your best bet would be two 16-ohm drivers. Two 4-ohm connected in series increases your radiating area but require the same amount of “power”.

Now, can a "value" driver with average distortion have as good of distortion when a SS speaker is driven a little harder? Maybe...but there are so many of factors involved also.

[cotdt]

An MTM using good value drivers will beat out the Scanspeak MT in the low end, if just barely, but there is no way that it can match the low midrange distortion of the Scanspeak.

A MTM will have lower impedance (assuming you wire the two drivers in parallel) and double the cone area, which give you an additional 6 dB of output. Therefore, you need less power to drive a MTM to the output as a TM and typically, speakers produce less distortion with less power.

Good point but I'd like to make a minor technical clarification. MTM will give 6 dB more sensitivity, but only 3 dB more max output which is barely noticeable. It will extend half an octave lower, but then again the Scanspeak woofer also extends half an octave lower than its competitors of the same size.

If you don't need the 3dB of extra output, having the midrange come from a single point source will sound more coherent with better off-axis response. Personally I prefer MT over MTM, and will take the ScanSpeak MT any day of the week. Incidentally, I already have one

If you want a good value, try the Peerless Exclusives, especially the 5.5" has a gorgeous midrange with a magical quality to it. This comes from its extremely low distortion, smooth response, and cone material. It's a lot more sensitive than the Scanspeak but doesn't have its bass extension, the bass is clean and punchy but it just rolls off earlier 'cause of its lighter moving mass. Just use a bass unit or subwoofer and don't worry about it

[alias2]

Power handling up 3dB and 3dB extra real sensitivity = 6dB more output.

Volume displacement in the bass is doubled, again 6dB extra maximum level.

An MTM does not extend any lower than a MT of half its volume, same driver.

Its apples and pears and not a great comparison. MTM's need to be compared
to an MT made with a larger bass driver, and then most "advantages" disappear.

It is true that there are some bass/mid drivers that are more effective used in
pairs, as a MTM, MMT or BBMT etc, and this does depend on design choices.
Generally double bass drivers increases sensitivity and decreases impedance,
the cost of this is you get no more bass extension for doubling the box size.
In a sense its a way of getting round a bass drivers intrinsic parameters.

Generally the lower you want to go the bigger the drivers needed.
For equal cone area MTM versus MT for typical driver parameters
the MT would have better bass extension but less real sensitivity.

[Carl V]

Presently, I have three monitors to listen to in the room
1. SSR from Selah MT design with 180mm slit cone & Fountek.
2. ACI 150mm Slit cone & SS 9500 MT desing
3. Selah Garnet MTM with Accuton & SS600
*** most listeners have prefered the Accuton MTM
The MT are very nice. Very nice indeed.
Recently this summer I had the SRA Rapides 170mm Accuton/6600
and it too was prefered most of the time. Comparisons were done
amongst the aforementioned 3 as well as well regarded Usher BE (MT)
and a Mini-Utopia BE. It reminded me of comparing the sound from a
fine Martin VS a Taylor VS Gyphon. Once you reach a certain level
you are picking overtones & style of play.

Driver materials color the sound. MT VS MTM also effect the sound.
Preferences/bias played a big role. However, take home lesson was
if you can go with the best quality drivers...all else being equal.