Frequency Response: +/-3dB Good Enough?

[BAM]

I have been poking away at a crossover redesign for my main "Project MTM" speakers, and I have reached a point where the predicted response curve according to Speaker Workshop is no more than +/-3dB. Should this be "good enough" for satisfying listening? The Seas H537 tweeter seems to be working pretty good. My problem is with the 5.25" midbass driver I am using. I already have them, and they demonstrate good resolution, and I already have them, so I don't want to go pay for new drivers.

My question is simply this: How important is it to have ruler-flat frequency response, all things considered?

[MBK]

If you measure in-room, +- 3 dB is excellent. In anechoic conditions maybe manufacturers would go further, only to achieve +- 5 or even 10 dB in-room

What's more inportant that the fight for the last dB on-axis, is a smooth integration off-axis. Say, repeat the measurements at 45 degrees off axis and see if the drivers integrate smoothly.

Another tidbit: I noticed that dips or peaks of 3 dB in the 100-500 Hz region can change the character quite noticeably, form "boomy" to "lean", it is worth tweaking to find a solution that you like (here it's more "taste" than "engineering").

[5th element]

To check the drivers are in phase too reverse the polarity on the tweeter in SPWshop and see if you get a good null at the xover frequency.

Otherwise +-3 is good.

[BAM]

Here's a picture of the predicted response. It looks like junk because of that 3200Hz peak but I have already calculated a notch filter to take that one out. Woofer crossover is second order 2100Hz, tweeter crossover is second order 2600Hz. You;ll notice the severely recessed lower midrange and midbass. (This midbass driver is used in the Definitive Technology BP8.) Yet, this is still only -2dB.

[MBK]

Hmm, didn't read carefully. If it's a simulation, I'd stop here, built a prototype (breadboard is enough) and measure in room, this will give a very different picture

[BAM]

I don't have a good measuring setup (or any at all) for actual performance, so I am trying to cover as many bases as possible in my own simulations. The overall character of the speakers shouldn't change much (recessed midrange, good bass, extended and detailed highs), just a major smoothing of the midrange and, of course, the elimination of that bothersome peak.

On a side note, is 2600hz an appropriate crossover point for a tweeter whose Fs is 1200Hz? pdf

[5th element]

If you wish to email me the FRD and ZMA files you have for both of these drivers I dont mind having a go with LSPcad and see what I can come up with.

c.storey@freeuk.com

[BAM]

5thelement: YGM.

Thanks, man.

[hunter audio]

hi

well

i think you will need to divide the drive units to get ruler flat - phase responce

no 1 - phase in tweeters will not be box dependant

no 2 - but lows and mids drivers will be speacially if ported

leaving out off axis performance and polar plots

we have either you go in for manger for a flat frequency responce down to about 80 hz (as its not box dependant)

or considering hi - fi drivers , in ported enclosures of lows to mid lows will have a phase problem speacially when multiple drivers are used - even 2 for sterio purposes - as waves emiited from one will cancel the other - in real life conditions

after box modelling you will need considerable tweeking with the c/o (which will change the timing of the drivers) and porting

with a audio sweep and a pro rta to eliminate phase problems and have the system up / and adapted to your listining area

but once - if you have done this a 1000 USd sytem can take on really expensive set ups - the improvement will be quite a bit

i think the responce is good enough - you should construct the box and then go fro final sound engineering to improve the room for improvement here is quite vast

and more often than not over looked - that way if one uses the most over - killed drive units - and the best box - they should end up with the best loudspeaker

it is not so ,

keen ingeneering , common sence and application can make way for great improvements

suranjan

transducer design engineer