Seas 2Way. - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 18th October 2004, 11:06 PM   #1
Baronty is offline Baronty  United Kingdom
diyAudio Member
Join Date: Oct 2004
Default Seas 2Way.

I know i posted a first build type thread the other day (3way)
but i decided to start a bit simpler so im gonna make some 2way bookcase style speakers for a mate.

Im thinking seas 27TFFC tweeter and a P17RCY MidWoofer.

This will be in a 7.3L vented enclosure tuned to 66Hz with a 6.8cm vent 28cm long giving a vent mach of 0.04 (calculated in WinIsd Beta).

I was thinking of using a 2nd order LW crossing at 3KHz with a zobels network on the midwoofer.

I have attached and image of the xover and zobels network i designed for it and a SPL plot for the P17RCY from WinIsd.

If someone could have a look and check that i havent gone horribly wrong it would be very much appreciated.

Oh and baffle step effects - how much should i worry?
Attached Images
File Type: gif 2way 2ndlw seas.gif (33.8 KB, 628 views)
  Reply With Quote
Old 19th October 2004, 12:02 AM   #2
diyAudio Member
Lazyworm's Avatar
Join Date: Nov 2003
Location: Stockholm in Sweden
Send a message via ICQ to Lazyworm
I would have used a 12l box tuned to 44ish Hz.
even if I went for a 7l box I wouldnt tune it above 55Hz
  Reply With Quote
Old 19th October 2004, 07:46 AM   #3
Nisbeth is offline Nisbeth  Denmark
diyAudio Member
Nisbeth's Avatar
Join Date: Jan 2001
Location: Denmark
12 liter box and 44-45 Hz tuning would be my suggestion as well

  Reply With Quote
Old 19th October 2004, 08:12 AM   #4
Baronty is offline Baronty  United Kingdom
diyAudio Member
Join Date: Oct 2004
Why? - I have ploted the different curves in WinIsd and 7.3 @ 66Hz remains flatter for ~100hz longer - admittedly the rate of roll off is steeper but the F3 point is 75.18hz compared to 91.24Hz for the same driver in a 12L enclosure tuned to 44Hz.

Can you explain why you recommend 12l / 45Hz? Im new to this and not sure what im missing here

Ive ploted the curves in winisd and attached them below

Green - 12L / 44Hz F3 @ 91.24hz
Red - 7.3l / 55Hz F3 @ 79.92Hz
Blue - 7.3L / 66hz F3 @ 75.18Hz
Attached Images
File Type: gif comparison p17rcy.gif (36.0 KB, 496 views)
  Reply With Quote
Old 19th October 2004, 05:35 PM   #5
diyAudio Member
Join Date: Nov 2002
Location: Indiana
Default Intent

Not sure of your intentions here, but what you have modeled has no bass. If you wish to pair this up with a subwoofer as a satellite, then the response is appropriate. Otherwise, it will be all midrange and highs, with no balance.

I think the other posters were suggesting some kind of alignment to extend the low end response.

  Reply With Quote
Old 19th October 2004, 06:41 PM   #6
Baronty is offline Baronty  United Kingdom
diyAudio Member
Join Date: Oct 2004
Im trying to model a simple twoway full range speaker in a small enclosure. when you say it has no bass - at what point does the mid / midbass become bass / sub-bass?

The WinIsd plots above show only a 10 - 20Hz extention from my original plot (blue line) and the suggested 12L / 45Hz enclosure (green line) is an F3 75.18 really produce poor bass response?

The blue curve maintains a 92dB profile to a lower freq than the green

Sry still kinda new to all this - just trying to understand how to extend the bass repsonse while maintaining a relatively flat profile.

All the help is greatfully appreciated
  Reply With Quote
Old 19th October 2004, 11:03 PM   #7
diyAudio Member
Join Date: Nov 2002
Location: Indiana
Default Response

Couple of basics might help - highly simplified. Bass extends from 20 Hz up to aound 200 Hz. Most commercial speakers run to +- 3dB from 30Hz and below, for the large floor standers, to 60 or 70 Hz for the small bookshelf/mini-monitors, in terms of bass extension. Music can run to very low frequencies with a big pipe organ, like 16 Hz, but generally speaking, low E on the electric bass guitar is good enough, or, at or near 40 Hz. So to reproduce 95 % or more of all music, that should be your target.

The Thiele-Small parameters are basically an electrical means to measure what a woofer is capable of doing. For sealed enclosures, look for Qts values from .35 to .50. Since Qts is a rough reflection of damping, a sealed box generally requires more excursion, therefore less motor strength, and lower damping than a woofer used in a ported box.
Ported enclosures usually contain woofers with Qts values from mid .30s on down. When Qts drops into the .20s, the woofer is said to be highly damped, which works well for efficiency but not so well for excursion, where the motor strength is actually working against a reasonable freedom of movement.

For the short term, to get extension near 40 Hz, look for Qts around low .30s, Xmax in the 6mm or more range, Fs in the 30s Hz or below, and efficiency as high as you can get. Peerless has affordable woofers that should meet yor needs, also Vifa, but the Seas are really quite good. The metal cones offer more of a challenge to a beginning DIYer due to the resonances and break-up problems at higher frequencies that must be successfully dealt with in the crossover. See Siegfried Linkwitz's "Orion" dipole design.
One popular Seas design is the Thor MTM, which may give you some idea of the specs to look for, and the woofers are paper.

The box size will increase at a rate of 8 times for every octave you drop in bass extension while maintaining the same SPL(dB), so it will not be possible to achieve low frequency extension, low power use, and small box size simultaneously, Hoffman's Iron Law says, so pick two.
Most people cheat on the power end of it by simply giving it more gas, failing to realize the result of this is rising compression and distortion, but that is another day.

Speaker-building is a collection of compromises, but at least you get to pick those right for you.

  Reply With Quote
Old 19th October 2004, 11:49 PM   #8
Baronty is offline Baronty  United Kingdom
diyAudio Member
Join Date: Oct 2004
cheers for the pointers - ive been using the T-S parameters and WinIsd to calculated Spl and freq response but im still having great difficultly finding a driver.

As you said its a matter of compromise but i really cant go for an enclosure of more than 20L.

This restricts a number of drivers i would have other wise chosen - the Vifa c20WJ-19 for example which maintains the 91dB SPL and can extend bass response down to an F3 of 33.1Hz unfortuneately this require a cab or over 124L

Im having great difficulty in find a driver that retains the sensitivity while having a extended bass response.

Any driver suggestion? - I have modelled the majority of the ones i have been able to find readily availiable and it appear that most with a 90+spl and an f3 of below 40hz require a cab of 50L and upwards
  Reply With Quote
Old 20th October 2004, 12:49 AM   #9
diyAudio Member
Join Date: Nov 2002
Location: Indiana
Default Efficiency

Try the 850122 Peerless 7". The Qs are a little high, the efficiency pretty low, but that is the cost of the box size remaining fixed if we still want to attain somrthing close to 40 Hz.
See how it models in a 20 l ported enclosure tuned to 40 Hz.
Fs is 38 Hz, so not much more there. Handles power well though, and has 5mm xmax, so the numbers look OK.
It will work in either a sealed or ported enclosure. While you have not mentioned the dreaded sealed box, they do actuallt work well. Just not as efficient.


Edit: The Thor has magnesium woofers.
  Reply With Quote
Old 20th October 2004, 07:08 AM   #10
manek is offline manek  India
diyAudio Member
Join Date: May 2004
Location: Bombay
try the vifa P17wj-00-08 6.5" mid/bass
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Help on 2way DIY Enclosure pcyl Planars & Exotics 2 10th February 2009 12:31 PM
SEAS 2way tpsorin Multi-Way 29 28th July 2007 08:50 AM
Seas 2Way Cabinets ndc_11 Multi-Way 2 5th July 2005 02:48 PM
Seas L series 6.5" 2way michael Multi-Way 16 25th November 2004 05:35 AM

New To Site? Need Help?

All times are GMT. The time now is 07:50 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2